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Alpha-Lipoic as biological antioxidant
Abstract
alpha-Lipoic acid, which plays an essential role in mitochondrial dehydrogenase reactions, has recently gained considerable attention as an antioxidant. Lipoate, or its reduced form, dihydrolipoate, reacts with reactive oxygen species such as superoxide radicals, hydroxyl radicals, hypochlorous acid, peroxyl radicals, and singlet oxygen. It also protects membranes by interacting with vitamin C and glutathione, which may in turn recycle vitamin E. In addition to its antioxidant activities, dihydrolipoate may exert prooxidant actions through reduction of iron. alpha-Lipoic acid administration has been shown to be beneficial in a number of oxidative stress models such as ischemia-reperfusion injury, diabetes (both alpha-lipoic acid and dihydrolipoic acid exhibit hydrophobic binding to proteins such as albumin, which can prevent glycation reactions), cataract formation, HIV activation, neurodegeneration, and radiation injury. Furthermore, lipoate can function as a redox regulator of proteins such as myoglobin, prolactin, thioredoxin and NF-kappa B transcription factor. We review the properties of lipoate in terms of (1) reactions with reactive oxygen species; (2) interactions with other antioxidants; (3) beneficial effects in oxidative stress models or clinical conditions.
... No direct information, to the best of our knowledge, is available on the role(s) of another key MN, ALA, endowed to be an essential nutrient for mitochondrial functions, namely in the TCA (Krebs) cycle and as a recognized antioxidant [39]. Several reports on ALA-associated protective roles of ALA in other pathologies [40][41][42]. Further research is expected on this subject. ...
... Notwithstanding the current limitations on the roles -if any -of MNs, it is worth recalling the recognized prevalence of MDF, along with a prooxidant state, in FXS/FXTAS [2,7,[11][12][13][14][15][16][17][18][19][40][41][42][43][44][45][46][47]. ...
Fragile X syndrome (FXS) is a genetic disorder characterized by mutation in the FMR1 gene, leading to the absence or reduced levels of fragile X Messenger Ribonucleoprotein 1 (FMRP). This results in neurodevelopmental deficits, including autistic spectrum conditions. On the other hand, Fragile X-associated tremor/ataxia syndrome (FXTAS) is a distinct disorder caused by the premutation in the FMR1 gene. FXTAS is associated with elevated levels of FMR1 mRNA, leading to neurodegenerative manifestations such as tremors and ataxia.
Mounting evidence suggests a link between both syndromes and mitochondrial dysfunction (MDF). In this minireview, we critically examine the intricate relationship between FXS, FXTAS, and MDF, focusing on potential therapeutic avenues to counteract or mitigate their adverse effects. Specifically, we explore the role of mitochondrial cofactors and antioxidants, with a particular emphasis on alpha-lipoic acid (ALA), carnitine (CARN) and Coenzyme Q10 (CoQ10). Findings from this review will contribute to a deeper understanding of these disorders and foster novel therapeutic strategies to enhance patient outcomes.
... ALA is a natural compound that can be found in virtually all animal species. Moreover, it has been shown that ALA is a natural and very powerful free radical scavenger [46]. In addition to its antioxidant effects, ALA helps with the regeneration of glutathione (GSH), vitamin C, vitamin E, and coenzyme Q10 in vivo [47]. ...
Over three years since the World Health Organization (WHO) declared COVID-19 a pandemic, it is still a global burden. Vaccines against COVID-19, caused by SARS-CoV-2, are available and effective for preventing disease. However, their protective effects are not 100%. Currently, the U.S. Food and Drug Administration (FDA) has only approved a limited number of inpatient treatments for COVID-19, such as remdesivir, baricitinib, and tocilizumab. These medications have indications and contraindications applicable to a select patient population. Finding additional effective therapies that are widely available with limited risk could be vital in optimizing treatment strategies for this viral illness. Some vitamins and supplements have been identified as potential options for managing COVID-19. Vitamin D (VD) deficiency has been associated with respiratory tract infections. Moreover, alpha-lipoic acid (ALA) is a powerful antioxidant and helps reduce inflammatory responses in many pathologic conditions. This review aims to analyze the current evidence regarding the effectiveness of VD and alpha-lipoic acid in COVID-19 infection in both outpatient and hospitalized patients.
Relevant randomized controlled trials (RCTs) were identified via the PubMed database from January 1, 2021, to December 31, 2023. Inclusion criteria were as follows: the study design was a randomized controlled trial (RCT), the usage of a constant dose during the intervention period without any additional boluses, and a research ethics committee approved it. Exclusion criteria included a lack of an outcome or apparent intervention, additional boluses, or a single-dose regimen in all the interventional groups. There were 11 studies with a total sample size of 35,717 patients that met the criteria for this review.
A total of 10 RCTs examined the efficacy of VD, and one RCT that reviewed the efficacy of ALA was identified. All of the articles investigated the use of VD or ALA during the treatment of COVID-19. The endpoints of each study varied, including length of stay in hospital, viral load, SARS-CoV-2 infection rate, mechanical ventilation, inflammatory markers, clinical symptoms, Sequential Organ Failure Assessment (SOFA) score, and mortality. In 8/10 VD supplementation trials, significant differences were identified between the interventional and placebo groups in the aforementioned parameters. In 2/10 VD supplementation trials, no significant differences were identified. The ALA supplementation RCT found no differences between the interventional and placebo groups in the SOFA score and 30-day all-cause mortality rate.
The current literature suggests that VD can potentially reduce the SARS-CoV-2 infection rate, oxygen requirements, inflammatory markers, clinical symptoms, and mortality. Regarding ALA, although there was a suggestion of benefit, it was not statistically significant. Common limitations among the different studies included relatively small sample sizes, different geographical patient locations among studies, and differences in dosages. Trials investigating the effects of higher doses of VD supplementation on SARS-CoV-2 infection should be conducted. More research is needed to define best practices and optimal dosing protocols for the use of VD in COVID-19.
... The reduction in MDA caused by LA application was combined with increases in antioxidant molecules, which resulted in better fitness of tomato plants under salinity conditions. Similar findings are reported by LA application under salt stress, water stress (Sezgin et al. 2019), heavy metal stress (Packer et al. 1995;Turk et al. 2018), and osmotic stress (Terzi et al. 2018). Although salt stress triggered POD and SOD activities in this research (Fig 4, 5), LA application boosted these antioxidants' activities even further. ...
Lipoic acid (LA) is a naturally synthesized antioxidant in plants, and its protective role against abiotic stresses is well known. However, its protective role on tomato growth and yield under salt stress is not clear. In this study, we explored the impact of different doses of LA (0, 2, 4, and 6 mM) on two tomato cultivars (Nadir and Naqeeb) under saline conditions (0, 120 mM). Tomato seedlings were shifted to plastic pots containing sterile soil. LA was sprayed on tomato foliage after salt stress application. Foliar application of LA significantly enhanced plant growth by improving 34% shoot length (SL), 28% shoot fresh weight (SFW), and 29% leaf area (LA) in Nadir under salt stress. Leaf photosynthetic pigments were improved viz. chlorophyll a (Chl a) by 29%, chlorophyll b (Chl b) by 35%, total chlorophyll (total chl) by 42%, and carotenoids (carot) by 25% in Nadir under salt stress. The improvement in plant growth was related with a decrease in salt-induced oxidative damage like reduction in leaf malondialdehyde (MDA) by 23% in Nadir. Generally, LA application showed higher antioxidant enzyme activities under control and stress conditions. Peroxidase (POD) activity was increased by 11% and superoxide dismutase (SOD) activity by 21% in Nadir under saline condition. Interestingly, LA application helped to reduce sodium (Na +) concentration in leaf (14%) and roots (25%) in Nadir under salt stress. In contrast, potassium (K +) concentration was increased in both roots (48%) and leaves (77%) in Nadir under stress. Moreover, tomato yield was also increased by LA application under stress. These results exhibited that LA application may reduce the negative effect of salt stress on tomato growth and yield by modulating its enzymatic antioxidants and biochemical traits and hence could be used effectively for the induction of salinity tolerance in plants.
... This chemical motif is inherent in naturally occurring α-lipoic acid (LA), also known as thioctic acid, which exhibits biological activities such as robust antioxidant properties ( Figure 1a). 1,2 In addition, LA derivatives are recognized for various applications including the stabilization of quantum dots and metal nanoparticles. [3][4][5] In recent years, considerable attention has been directed towards the utilization of 1,2-dithiolanes in polymer science as a pivotal motif for creating "circular" plastics with recyclability, 6,7 and adaptable networks with functionalities like self-healing. ...
Passerini polymerization using naturally occurring α-lipoic acid as a raw material yields polyamides with 1,2-dithiolane functional groups in a one-step reaction. The polyamide exhibits characteristics of an adaptable dynamically crosslinked...
... α-lipoic acid is an antioxidant and plays a role in the formation of various types of dehydrogenases involved in energy metabolism [12]. Its ability to regenerate allows it to provide continuous protection to organisms [13]. Adding α-lipoic acid to the diets of Nile tilapia (Oreochromis niloticus) and crucian carp (Carassius auratus) can enhance their weight gain rate and specific growth rate [14,15]. ...
This study aimed to assess the impact of α-lipoic acid on the growth performance, antioxidant capacity and immunity in hybrid groupers (♀ Epinephelus fuscoguttatus × ♂ E. lanceolatus) fed with a high-lipid diet. Groupers (8.97 ± 0.01 g) were fed six different diets, with α-lipoic acid content in diets being 0, 400, 800, 1200, 1600, and 2000 mg/kg, named S1, S2, S3, S4, S5, and S6, respectively. The results show that the addition of 2000 mg/kg α-lipoic acid in the diet inhibited the growth, weight gain rate (WGR), and specific growth rate (SGR), which were significantly lower than other groups. In serum, catalase (CAT) and superoxide dismutase (SOD) were significantly higher in the S5 group than in the S1 group. In the liver, CAT, SOD and total antioxidative capacity (T-AOC) levels were significantly increased in α-lipoic acid supplemented groups. α-lipoic acid significantly upregulated liver antioxidant genes sod and cat, anti-inflammatory factor interleukin 10 (il10) and transforming growth factor β (tgfβ) mRNA levels. Conclusion: the addition of 2000 mg/kg of α-lipoic acid inhibits the growth of hybrid groupers. In addition, 400–800 mg/kg α-lipoic acid contents improve the antioxidant capacity of groupers and have a protective effect against high-lipid-diet-induced liver oxidative damage.
... Lipoic acid synthase (LIAS) is responsible for encoding the components of the lipoic acid pathway and synthesizingα-Lipoic acid (LA), which is a potent antioxidant found in mitochondria [33]. Mutations in the LIAS gene can lead to impaired enzyme activity and disruption of the normal process of long-chain fatty acid oxidation, leading to an accumulation of fatty acid intermediates. ...
Background
Multiple modes of cell death occur during the development of sepsis. Among these patterns, cuproptosis has recently been identified as a regulated form of cell death. However, its impact on the onset and progression of sepsis remains unclear.
Method
We screened a dataset of gene expression profiles from patients with sepsis using the GEO database. Survival analysis was performed to analyze the relationship between cuproptosis-related genes (CRGs) and prognosis. Hub genes were identified through univariate Cox regression analysis. The diagnostic value of hub genes in sepsis was tested in both training sets (GSE65682) and validation sets (GSE134347). To examine the association between hub genes and immune cells, single-sample gene set enrichment analysis (ssGSEA) and Pearson correlation analysis were employed. Additionally, the CRGs were validated in a septic mouse model using real-time quantitative PCR (qRT-PCR) and immunohistochemistry (IHC).
Results
In sepsis, most CRGs were upregulated, with only DLD and MTF1 downregulated. High expression of three genes (GLE, LIAS, and PDHB) was associated with better prognosis, but only two hub genes (LIAS, PDHB) reached statistical significance. The receiver operating characteristic (ROC) analysis for diagnosing sepsis showed LIAS had a range of 0.793–0.906, while PDHB achieved values of 0.882 and 0.975 in the training and validation sets, respectively. ssGSEA analysis revealed a lower number of immune cells in the sepsis group, and there was a correlation between immune cell population and CRGs (LIAS, PDHB). Analysis in the septic mouse model demonstrated no significant difference in mRNA expression levels and IHC staining between LIAS and PDHB in heart and liver tissues, but up-regulation was observed in lung tissues. Furthermore, the mRNA expression levels and IHC staining of LIAS and PDHB were down-regulated in renal tissues.
Conclusions
Cuproptosis is emerging as a significant factor in the development of sepsis. LIAS and PDHB, identified as potential diagnostic biomarkers for cuproptosis-associated sepsis, are believed to play crucial roles in the initiation and progression of cuproptosis-induced sepsis.
... Coenzyme Q10 Ubiquinone plays a key role in oxidative phosphorylation. Coenzyme Q10 has been shown to beneficially stimulate the AMPK gene, which may be responsible for the inflammation, low antioxidant levels, and low mitochondrial production that characterize the pathophysiology of fibromyalgia [57]. This review shows that there are studies demonstrating its benefits for pain [38,42,46]. ...
Citation: Fernández-Araque, A.; Verde, Z.; Torres-Ortega, C.; Sainz-Gil, M.; Velasco-Gonzalez, V.; González-Bernal, J.J.; Mielgo-Ayuso, J. Effects of Antioxidants on Pain Perception in Patients with Fibromyalgia-A Systematic Review.
... PαLA and its degradation products are safe and biocompatible. Disulfide bonds in its main chain play an antioxidant role in osteoarthritis (Packer et al., 1995;Shimoda et al., 2007;Shay et al., 2009;Li et al., 2013;Yang et al., 2018). Given the use of nanomaterials as corticosteroids carriers and PLA's excellent antiinflammatory properties, we speculated that NP DXM/PPLA prepared by the electrostatic and hydrophobic action of the carboxyl group on mPEG-g-PαLA carrying DXM may be a promising new drug for the treatment of OA. ...
Osteoarthritis (OA) is a chronic inflammatory disease that causes synovial hyperplasia, cartilage destruction, and the formation of bone spurs. Macrophages play an indispensable role in the pathogenesis of OA by producing proinflammatory cytokines. To achieve the effect of arthritis, hormones can effectively inhibit the progression of inflammation by inhibiting the secretion of inflammatory cytokines by macrophages in traditional therapy. However, the drug is quickly cleared from the joint space, and the high injection site infection rate and low local drug concentration make the clinical efficacy of corticosteroids greatly reduced. We described the design and preparation of Polyethylene Glycol-grafted Poly Alpha-lipoic Acid-dexamethasone Nanoparticles (NP DXM/PPLA ), elucidated the mechanism of action of NP DXM/PPLA in the treatment of OA in mice, and provided an experimental basis for investigating the treatment of OA with polymer nanoparticles loaded with dexamethasone. Flow cytometry and confocal laser scanning microscopy were used to confirm that NP DXM/PPLA was well absorbed and released by macrophages, and it was discovered that NP DXM/PPLA could efficiently reduce the proliferation of activated macrophages (RAW 264.7 cells). Enzyme-linked immunosorbent assay revealed that NP DXM/PPLA could efficiently reduce the expression of proinflammatory cytokines IL-1β, IL-6, and TNF-α. The knee bone structure of OA mice was investigated by MicroCT, and it was discovered that intraarticular injection of NP DXM/PPLA effectively alleviated the bone damage of the articular cartilage. Therefore, NP DXM/PPLA is a potential therapeutic nanomedicine for the treatment of OA.
... There are some antioxidants that are both water and fat soluble, like Gingko Biloba and alpha lipoic acid. The latter has both antioxidant properties and restores the antioxidant ability of glutathione, vitamin A, vitamin E, and vitamin C [97]. It has been demonstrated that vitamins C and E are potential treatments of SNHL. ...
Introduction:
OSAS is a disease that affects 2% of men and 4% of women of middle age. It is a major health public problem because untreated OSAS could lead to cardiovascular, metabolic, and cerebrovascular complications. The more accepted theory relates to oxidative stress due to intermittent hypoxia, which leads, after an intense inflammatory response through multiple pathways, to endothelial damage. The objective of this study is to demonstrate a correlation between OSAS and hearing loss, the effect of the CPAP on hearing function, and if oxidative stress is also involved in the damaging of the hearing system.
Methods:
A review of the literature has been executed. Eight articles have been found, where seven were about the correlation between OSAS and the hearing system, and only one was about the CPAP effects. It is noted that two of the eight articles explored the theory of oxidative stress due to intermittent hypoxia.
Results:
All studies showed a significant correlation between OSAS and hearing function (p < 0.05).
Conclusions:
Untreated OSAS affects the hearing system at multiple levels. Oxidative stress due to intermittent hypoxia is the main pathogenetic mechanism of damage. CPAP has no effects (positive or negative) on hearing function. More studies are needed, with the evaluation of extended high frequencies, the execution of vocal audiometry in noisy environments, and the evaluation of potential biomarkers due to oxidative stress.
... The reduction in MDA caused by LA application was combined with increases in antioxidant molecules, which resulted in better fitness of tomato plants under salinity conditions. Similar findings are reported by LA application under salt stress, water stress (Sezgin et al. 2019), heavy metal stress (Packer et al. 1995;Turk et al. 2018), and osmotic stress (Terzi et al. 2018). Although salt stress triggered POD and SOD activities in this research (Fig 4, 5), LA application boosted these antioxidants' activities even further. ...
Lipoic acid (LA) is a naturally synthesized antioxidant in plants, and its protective role against abiotic stresses is well known. However, its protective role on tomato growth and yield under salt stress is not clear. In this study, we explored the impact of different doses of LA (0, 2, 4, and 6 mM) on two tomato cultivars (Nadir and Naqeeb) under saline conditions (0, 120 mM). Tomato seedlings were shifted to plastic pots containing sterile soil. LA was sprayed on tomato foliage after salt stress application. Foliar application of LA significantly enhanced plant growth by improving 34% shoot length (SL), 28% shoot fresh weight (SFW), and 29% leaf area (LA) in Nadir under salt stress. Leaf photosynthetic pigments were improved viz. chlorophyll a (Chl a) by 29%, chlorophyll b (Chl b) by 35%, total chlorophyll (total chl) by 42%, and carotenoids (carot) by 25% in Nadir under salt stress. The improvement in plant growth was related with a decrease in salt-induced oxidative damage like reduction in leaf malondialdehyde (MDA) by 23% in Nadir. Generally, LA application showed higher antioxidant enzyme activities under control and stress conditions. Peroxidase (POD) activity was increased by 11% and superoxide dismutase (SOD) activity by 21% in Nadir under saline condition. Interestingly, LA application helped to reduce sodium (Na+) concentration in leaf (14%) and roots (25%) in Nadir under salt stress. In contrast, potassium (K+) concentration was increased in both roots (48%) and leaves (77%) in Nadir under stress. Moreover, tomato yield was also increased by LA application under stress. These results exhibited that LA application may reduce the negative effect of salt stress on tomato growth and yield by modulating its enzymatic antioxidants and biochemical traits and hence could be used effectively for the induction of salinity tolerance in plants.
... The DSB system is a master regulator of bacteria virulence. [1,[13][14][15] Anticancer agent romidepsin, used for the treatment cutaneous T-cell lymphoma, [16] antioxidant lipoic acid, [17] or hormone inhibitor atosiban [18] contain sulfur-sulfur bridge. Natural product, Psammaplysilla sp. ...
A series of novel 1,2‐bissubstituted disulfanes bearing beta‐amino acid, dihydropyrimidine‐2,4‐(1H,3H)‐dione, hydrazide, hydrazone and azole moieties were synthesized. The antibacterial activity was evaluated by determining minimum inhibition (by broth microdilution) and minimum bactericidal (by growth on agar) concentrations. The assessment revealed that MIC values for L. monocytogenes varied between 3.9 and 62.5 μg/mL as well as for S. aureus ranged between 7.8 and 250 μg/mL, with the exception of one compound with much weaker MIC of 500 μg/mL. The MBC values for L. monocytogenes have been found to be of 7.8–250 μg/mL, while S. aureus demonstrated the higher resistance and MBCs varied in the range of 7.8–500 μg/mL. The determined MBC/MIC ratios showed that eleven compounds were classified bactericidal agents for all tested bacteria.
The blue mussels Mytilus edulis and Mytilus trossulus are ecologically and economically important species distributed widely across the Northern Hemisphere. Understanding their behavioral and physiological disparities is crucial for assessing their ecological success and aquacultural value. The recent finding of non-native M. trossulus in the White Sea raises concerns regarding its potential competition with native M. edulis and its prospective spread in light of climate change and surface water freshening. We investigated the responses of M. edulis and M. trossulus to salinity variations by examining shell closure thresholds and tissue levels of 35 metabolic intermediates in mussels acclimated to different salinities (25, 16, and 10). The salinity threshold for valve closure was similar in both studied species, but M. trossulus consistently opened at lower salinities (by 0.2-0.7 practical salinity units) compared to M. edulis. Salinity-induced changes in metabolite levels were similar between the two species. Taurine emerged as the dominant osmolyte, comprising over 50% of the total free amino acid pool, with aspartate and glycine contributing 15-30%. Concentrations of taurine, glycine, and total free amino acids declined with decreasing salinity. Taurine to glycine ratios were higher in M. edulis and increased in both species with declining salinity. Acclimation salinity significantly influenced urea cycle intermediates and methionine sulfoxide content, a cellular biomarker of amino acid oxidation. Species-specific differences were observed in purine metabolism, with higher levels of GMP and AMP found in M. edulis. Likewise, aromatic amino acids and histidine levels were higher in M. edulis compared to M. trossulus. However, no evidence Frontiers in Marine Science Sokolova IM, Kovalev A, Timm S, Marchenko J and Sukhotin A (2024) Species-specific metabolome changes during salinity downshift in sub-Arctic populations of Mytilus edulis and M. trossulus. suggests superior adaptation of M. trossulus metabolism to hypoosmotic stress compared to M. edulis. Further research is necessary to elucidate the functional implications of subtle metabolic differences between these Mytilus congeners and their ecological consequences in changing marine environments.
This study was designed to address the question: does antioxidant-containing embryo culture media affect DNA methyltransferases, global DNA methylation, inner cell mass/trophoblast differentiation, intracellular reactive oxygen species (ROS) levels, and apoptosis? Mouse zygotes were cultured in embryo culture media containing MitoQ, N-acetyl-l-cysteine (NAC), acetyl-l-carnitine (ALC), α-lipoic acid (ALA), or the mixture of NAC + ALC + ALA (AO) until the blastocyst stage, whereas in vivo-developed blastocysts were used as control. Protein expression levels of Dnmt1, 3a, 3b, and 3l enzymes were analyzed by immunofluorescence and western blot, while global DNA methylation, apoptosis, and ROS levels were evaluated by immunofluorescence. NAC, ALC, and MitoQ significantly increased the levels of all Dnmts and global methylation. ALA significantly induced all Dnmts, whereas global methylation did not show any difference. NAC and mixture AO applications significantly induced Nanog levels, ALA and MitoQ increased Cdx2 levels, while the other groups were similar. ALA and MitoQ decreased while ALC increased the levels of intracellular ROS. This study illustrates that antioxidants, operating through distinct pathways, have varying impacts on DNA methylation levels and cell differentiation in mouse embryos. Further investigations are warranted to assess the implications of these alterations on the subsequent offspring.
Lipoic acid trisulfide, a sulfane sulfur-containing trisulfide of α-lipoic acid, holds promise in pharmaceuticals, yet knowledge gaps persist regarding its synthesis, properties, and stability. Here, we synthesized the lipoic acid trisulfide with a purity exceeding 99% from α-lipoic acid on a gram scale and obtained novel β-cyclodextrin clathrates (84%-95% yield). Differential scanning calorimetry confirmed the inclusion of lipoic acid trisulfide in β-cyclodextrins. The resulting β-cyclodextrin clathrates exhibited significant improvements in water solubility and thermal stability. This pioneering study demonstrated a novel approach to the practical preparation of trisulfide and its β-cyclodextrin clathrates as active ingredients, paving the way for clinical development.
Abalone is a commercially important mariculture mollusc because of its nutrient‐rich value and extensive market demand. To date, over 95% of the abalone supply has been contributed by farming. Macroalgae are the natural food of abalones. However, the supply of macroalgae is unstable owing to seasonal restrictions. This limits the success of abalone farming. Therefore, formulated diets are crucial for the ongoing expansion and sustainable development of abalone culture. The most important considerations in formulated diets are the nutrient composition and commercially available feed ingredients. This review presents a comprehensive description of the nutrient requirements of abalones and the role that nutrients play in regulating abalone growth and health. The dietary proteins, lipids, carbohydrates, macroalgae sources and feed additives currently used in abalone feeds were subsequently summarised. Additionally, this review also highlights the importance of prioritizing the development of sustainable alternative sources of proteins, carbohydrates and macroalgae to meet the increasing demand for abalone feed. Based on the information provided, future directions in the knowledge of abalone nutrition and feeds are subsequently discussed, which will guide further research towards the development of well‐balanced commercial feeds that enhance feed utilisation and promote abalone growth and health.
Periodontitis, a common chronic inflammatory disease caused by pathogenic bacteria, can be treated with diverse biomaterials by loading drugs, cytokines or proteins. However, these biomaterials often show unsatisfactory therapeutic efficiency due to their poor adhesion, short residence time in the wet and dynamic oral cavity and emerging drug resistance. Here we report a wet-responsive methacrylated gelatin (GelMA)-stabilized co-enzyme polymer poly(α-lipoic acid) (PolyLA)-based elastic patch with water-induced adhesion and softening features. In PolyLA-GelMA, the multiple covalent and hydrogen-bonding crosslinking between PolyLA and GelMA prevent PolyLA depolymerization and slow down the dissociation of PolyLA in water, allowing durable adhesion to oral periodontal tissue and continuous release of LA-based bioactive small molecule in periodontitis wound without resorting external drugs. Compared with the undifferentiated adhesion behavior of traditional adhesives, this wet-responsive patch demonstrates a favorable periodontal pocket insertion ability due to its non-adhesion and rigidity in dry environment. In vitro studies reveal that PolyLA-GelMA patch exhibits satisfactory wet tissue adhesion, antibacterial, blood compatibility and ROS scavenging abilities. In the model of rat periodontitis, the PolyLA-GelMA patch inhibits alveolar bone resorption and accelerates the periodontitis healing by regulating the inflammatory microenvironment. This biomacromolecule-stabilized coenzyme polymer patch provides a new option to promote periodontitis treatment.
Reversal or mitigation against an age-related decline in NAD ⁺ has likely benefits, and this premise has driven academic and commercial endeavour to develop dietary supplements that achieve this outcome. We used a systems-based approach to improve on current supplements by targeting multiple points in the NAD ⁺ salvage pathway. In a double-blind, randomised, crossover trial, the supplement – Nuchido TIME+® (NT) - increased NAD ⁺ concentration in whole blood. This was associated with an increase in SIRT1 and an increase in nicotinamide phosphoribosyltransferase (NAMPT) in peripheral blood mononucleocytes, lower concentrations of pro-inflammatory cytokines in plasma, including a reduction in interleukin 2 (IL2), a reduction in glycated serum protein and a shift in the glycosylation profile of immunoglobulin G (IgG) toward a younger biological age, all of which are likely to promote a healthier ageing trajectory.
Introduction/Aims
Oxaliplatin is a platinum‐based anti‐cancer drug widely used in colorectal cancer patients, but it may cause peripheral neuropathy. As one of the main causes of oxaliplatin‐induced peripheral neuropathy (OPN) is oxidative stress, which is also a key factor causing diabetic peripheral neuropathy (DPN), the aim of this study was to evaluate the preventive effects of alpha‐lipoic acid (ALA) and epalrestat (EP), which are used for the treatment of DPN, in an OPN zebrafish model.
Methods
Tg(nbt:dsred) transgenic zebrafish, with sensory nerves in the peripheral lateral line, were treated with oxaliplatin, oxaliplatin/EP, and oxaliplatin/ALA for 4 days. A confocal microscope was used to visualize and quantify the number of axon bifurcations in the distal nerve ending. To analyze the formation of synapses on sensory nerve terminals, quantification of membrane‐associated guanylate kinase (MAGUK) puncta was performed using immunohistochemistry.
Results
The number of axon bifurcations and intensity of MAGUK puncta were significantly reduced in the oxaliplatin‐treated group compared with those in the embryo medium‐treated group. In both the oxaliplatin/EP and oxaliplatin/ALA‐treated groups, the number of axon bifurcations and intensity of MAGUK puncta were greater than those in the oxaliplatin‐treated group ( p < .0001), and no significant difference was observed between larvae treated with oxaliplatin/ALA 1 μM and oxaliplatin/EP 1 μM ( p = .4292).
Discussion
ALA and EP have protective effects against OPN in zebrafish. Our findings show that ALA and EP can facilitate more beneficial treatment for OPN.
This study aims to characterize the bone-protecting effects of Alpha-lipoic acid (ALA), a potent antioxidant, against the detrimental effects of the coexistence of type 2 diabetes mellitus (T2DM) and postmenopausal osteoporosis (POP) and identify the possible mechanisms with particular reference to its modulation of YAP/Glut4 pathway. The T2DM and POP coexisting model was induced in mice by high fat diet (HFD) + Streptozocin (STZ) + ovariectomy (OVX). The mice in the treatment groups were given ALA for 10 weeks. In the in vitro study, MC3T3-E1 cells were induced with 500 μM methylglyoxal for 24 h with or without pretreatment with ALA for 24 h. The oxidative and antioxidative biomarkers, bone microarchitecture, histo-morphology, and related protein expression of apoptosis, osteogenic differentiation and the YAP/Glut4 pathway were detected. The results showed ALA could improve glucose tolerance, inhibit oxidative stress and apoptosis and alleviate bone loss. Further study by siRNA technology revealed that the YAP/Glut4 pathway was implicated in the pathogenesis of bone loss due to the coexistence of T2DM and POP. Taken together, the present study has demonstrated for the first time that ALA exerts potent protective effects against bone loss in T2DM and POP coexisting conditions by modulating the YAP/Glut4 pathway.
Abstract
Background
Diabetic peripheral neuropathy (DPN) is a frequent complication in people living with type 1 or type 2 diabetes. There is currently no effective treatment for DPN. Although alpha‐lipoic acid (ALA, also known as thioctic acid) is widely used, there is no consensus about its benefits and harms.
Objectives
To assess the effects of alpha‐lipoic acid as a disease‐modifying agent in people with diabetic peripheral neuropathy.
Search methods
On 11 September 2022, we searched the Cochrane Neuromuscular Specialised Register, CENTRAL, MEDLINE, Embase, and two clinical trials registers. We also searched the reference lists of the included studies and relevant review articles for additional references not identified by the electronic searches.
Selection criteria
We included randomised clinical trials (RCTs) that compared ALA with placebo in adults (aged 18 years or older) and that applied the study interventions for at least six months. There were no language restrictions.
Data collection and analysis
We used standard methods expected by Cochrane. The primary outcome was change in neuropathy symptoms expressed as changes in the Total Symptom Score (TSS) at six months after randomisation. Secondary outcomes were change in neuropathy symptoms at six to 12 months and at 12 to 24 months, change in impairment, change in any validated quality of life total score, complications of DPN, and adverse events. We assessed the certainty of the evidence using GRADE.
Main results
Our analysis incorporated three trials involving 816 participants. Two studies included people with type 1 or type 2 diabetes, while one study included only people with type 2 diabetes. The duration of treatment was between six months and 48 months. We judged all studies at high risk of overall bias due to attrition.
ALA compared with placebo probably has little or no effect on neuropathy symptoms measured by TSS (lower score is better) after six months (mean difference (MD) −0.16 points, 95% confidence interval (CI) −0.83 to 0.51; 1 study, 330 participants; moderate‐certainty evidence). The CI of this effect estimate did not contain the minimal clinically important difference (MCID) of 0.97 points. ALA compared with placebo may have little or no effect on impairment measured by the Neuropathy Impairment Score‐Lower Limbs (NIS‐LL; lower score is better) after six months (MD −1.02 points, 95% CI −2.93 to 0.89; 1 study, 245 participants; low‐certainty evidence). However, we cannot rule out a significant benefit, because the lower limit of the CI surpassed the MCID of 2 points. There is probably little or no difference between ALA and placebo in terms of adverse events leading to cessation of treatment within six months (risk ratio (RR) 1.48, 95% CI 0.50 to 4.35; 3 studies, 1090 participants; moderate‐certainty evidence).
No studies reported quality of life or complications associated with DPN.
Authors' conclusions
Our analysis suggests that ALA probably has little or no effect on neuropathy symptoms or adverse events at six months, and may have little or no effect on impairment at six months. All the studies were at high risk of attrition bias. Therefore, future RCTs should ensure complete follow‐up and transparent reporting of any participants missing from the analyses.
Oxidative stress influences the embryo production efficiency in vitro. We investigated the effects of alpha lipoic acid (ALA) treatment during the in vitro maturation (IVM) period on the porcine somatic cell nuclear transfer (SCNT) embryo production. After IVM, maturation rates of the 12.5‐ and 25‐μM ALA‐treated groups were not significantly different from those of the 0‐μM ALA‐treated group. Compared to those in the 0‐μM ALA‐treated group, the reactive oxygen species and glutathione levels were significantly decreased and increased, respectively, in the cytoplasm of matured oocytes in the 12.5–50‐μM ALA‐treated groups. Apoptosis rate in cumulus cells after IVM was significantly lower in the 12.5–50‐μM ALA‐treated groups than in the 0‐μM ALA‐treated group. Blastocyst formation rate was significantly higher in parthenogenetic oocytes treated with 12.5‐μM ALA than in the 0‐, 25‐, and 50‐μM ALA‐treated groups. Similarly, in SCNT embryos, the 12.5‐μM ALA‐treated group showed a significantly higher blastocyst formation rate than the 0‐μM ALA‐treated group. Apoptosis rate in SCNT blastocysts was significantly decreased by 12.5‐μM ALA treatment. The results showed that treatment with 12.5‐μM ALA during IVM improves porcine SCNT embryo development and partial quality.
Inflammation is a reaction of the immune system to infection and injury; in fact, it positioned at the center of metabolic disorders, particularly obesity, type 2 diabetes, and cardiovascular diseases. Thus play a major role not only in their development, but also exerts as a crucial linking factor among those diseases. In this regard, one of the strategies for tackling this problem is application of antioxidants to treat such diseases. The present study was performed to evaluate the synergistic effects of punicic acid (PUA) and alpha‐lipoic acid (ALA) as antioxidants and radical scavenging reagents on the expression of some inflammatory and metabolism‐related genes under oxidative stress in the muscle cells . The experimental treatments consisted of a range of 20, 40, 80, 160, and 320 µM of PUA, and 5, 25, 50, 100, and 200 µM of ALA with a 200 µM concentration of H 2 O 2 as an oxidative stress inducer. Accordingly, fatty acid treatments were applied for 24 h, and H 2 O 2 was treated for 1 h. Our results indicated that the simultaneous treatment of PUA and ALA at optimal concentrations (80 and 50 µM, respectively) decreased the expression of inflammation genes and increased the expression of regulatory genes ( Ppar γ, Pgc ‐1α) related to metabolism ( p < .05). Unexpectedly, H 2 O 2 treatment increased the Fndc5 expression ( p < .05). Maximal upregulation of Pparγ , Pgc‐1α were obtained when fatty acids combination (PUA and ALA) were used in the culture of H 2 O 2 treated cells ( p < .05). Therefore, our findings suggest that the simultaneous use of PUA and ALA fatty acids could reduce oxidative stress, and the expression of inflammatory genes, thereby improving the cell metabolism.
Acute respiratory distress syndrome (ARDS) is a life-threatening pulmonary condition characterized by the sudden onset of respiratory failure, pulmonary edema, dysfunction of endothelial and epithelial barriers, and the activation of inflammatory cascades. Despite the increasing number of deaths attributed to ARDS, a comprehensive therapeutic approach for managing patients with ARDS remains elusive. To elucidate the pathological mechanisms underlying ARDS, numerous studies have employed various preclinical models, often utilizing lipopolysaccharide as the ARDS inducer. Accumulating evidence emphasizes the pivotal role of reactive oxygen species (ROS) in the pathophysiology of ARDS. Both preclinical and clinical investigations have asserted the potential of antioxidants in ameliorating ARDS. This review focuses on various sources of ROS, including NADPH oxidase, uncoupled endothelial nitric oxide synthase, cytochrome P450, and xanthine oxidase, and provides a comprehensive overview of their roles in ARDS. Additionally, we discuss the potential of using antioxidants as a strategy for treating ARDS.
Endogenous formaldehyde (FA) is produced in the human body via various mechanisms to preserve healthy energy metabolism and safeguard the organism. However, endogenous FA can have several negative effects on the body through epigenetic alterations, including cancer growth promotion; neuronal, hippocampal and endothelial damages; atherosclerosis acceleration; haemopoietic stem cell destruction and haemopoietic cell production reduction. Certain medications with antioxidant effects, such as glutathione, vitamin E, resveratrol, alpha lipoic acid and polyphenols, lessen the detrimental effects of endogenous FA by reducing oxidative stress, directly scavenging endogenous FA or promoting its degradation. This study offers fresh perspectives for managing illnesses associated with endogenous FA exposure.
Diabetes mellitus (DM) is a major disease threatening human health and its incidence is increasing year on year. As a chronic complication of DM, hearing loss mostly occurs undetectably. However, the mechanism of this diabetes-related hearing loss (DRHL) remains unclear and there is no effective clinical treatment. Studies of animal or human pathology show that DM causes damage to the blood vessels, spiral ganglion neurons, afferent nerve fibers, the organ of Corti, and the stria vascularis of the inner ear. In recent years, more advances in pathological research have revealed the possible mechanism of DRHL. In addition, a large number of clinical studies suggest that the duration and severity of DM are closely related to the incidence and severity of DRHL. This review focuses on the relationship between DM and hearing loss. The clinical audiological characteristics of diabetic patients, risk factors for DRHL, typical pathology, and potential interventions of DRHL are summarized. This will help reveal the pathogenesis and intervention approaches for DRHL.
α-lipoic acid (LA) is an essential cofactor for mitochondrial dehydrogenases and is required for cell growth, metabolic fuel production, and antioxidant defense. In vitro, LA binds copper (Cu) with high affinity and as an endogenous membrane permeable metabolite could be advantageous in mitigating the consequences of Cu overload in human diseases. We tested this hypothesis in 3T3-L1 preadipocytes with inactivated Cu transporter Atp7a; these cells accumulate Cu and show morphologic changes and mitochondria impairment. Treatment with LA corrected the morphology of Atp7a-/- cells similar to the Cu chelator bathocuproinedisulfonate (BCS) and improved mitochondria function; however, the mechanisms of LA and BCS action were different. Unlike BCS, LA did not decrease intracellular Cu but instead increased selenium levels that were low in Atp7a-/- cells. Proteome analysis confirmed distinct cell responses to these compounds and identified upregulation of selenoproteins as the major effect of LA on preadipocytes. Upregulation of selenoproteins was associated with an improved GSH:GSSG ratio in cellular compartments, which was lowered by elevated Cu, and reversal of protein oxidation. Thus, LA diminishes toxic effects of elevated Cu by improving cellular redox environment. We also show that selenium levels are decreased in tissues of a Wilson disease animal model, especially in the liver, making LA an attractive candidate for supplemental treatment of this disease.
The free radical chemistry of lipoic acid (LA) and dihydrolipoic acid (DHLA) intersect at the point where DHLA loses hydrogen to a good hydrogen abstracting radical, while LA reacts with strongly reducing ketyl radicals capable of donating a hydrogen atom. While aliphatic thiyl radicals have an absorbance at ~ 330 nm, the resulting radical, formally also a thiyl radical has distinct spectroscopic properties with a maximum at 385 nm, suggesting that the two sulphur centres interact strongly with each other as part of the chromophore. The reactions that form these radicals were studied by laser flash photolysis that revealed DHLA as an excellent hydrogen donor, while LA is an excellent hydrogen acceptor. The results support earlier evidence that the real antioxidant is DHLA, while LA is not; yet, the reported facile interconversion of the two molecules suggests that LA may be a better supplement, given its shelf stability, compared with a far more difficult-to-handle DHLA.
Reversal or mitigation against an age-related decline in NAD ⁺ has likely benefits, and this premise has driven academic and commercial endeavour to develop dietary supplements that achieve this outcome. We used a novel systems-based approach to improve on current supplements by targeting multiple points in the NAD ⁺ salvage pathway. In a double-blind, randomised, crossover trial, the supplement – Nuchido TIME+ ® (NT) - increased NAD ⁺ concentration in whole blood. This was associated with an increase in SIRT1 and an increase in nicotinamide phosphoribosyltransferase (NAMPT) in peripheral blood mononucleocytes, lower concentrations of pro-inflammatory cytokines in plasma, including a reduction in interleukin 2 (IL2), a reduction in glycated serum protein and a shift in the glycosylation profile of immunoglobulin G (IgG) toward a younger biological age, all of which are likely to promote a healthier aging trajectory.
The enzyme cofactor (R)-lipoic acid plays a critical role in central carbon metabolism due to its catalytic function in the generation of acetyl-CoA, which links glycolysis with the tricarboxylic acid cycle. This cofactor is also essential for the generation of succinyl CoA within the tricarboxylic acid cycle. However, the biological functions of (R)-lipoic acid extend beyond metabolism owing to its facile redox chemistry. Most recently, the reduced form of (R)-lipoic acid, (R)-dihydrolipoic acid, has been shown to inhibit histone deacetylases (HDACs) with selectivity for the inhibition of HDAC6. Here, we report the 2.4 Å-resolution X-ray crystal structure of the complex between (R)-dihydrolipoic acid and HDAC6 catalytic domain 2 from Danio rerio, and we report a dissociation constant (KD) of 350 nM for this complex as determined by isothermal titration calorimetry. The crystal structure illuminates key affinity determinants in the enzyme active site, including thiolate-Zn²⁺ coordination and S-π interactions in the F583-F643 aromatic crevice. This study provides the first visualization of the connection between HDAC function and the biological response to oxidative stress: the dithiol moiety of (R)-dihydrolipoic acid can serve as a redox-regulated pharmacophore capable of simultaneously targeting the catalytic Zn²⁺ ion and the aromatic crevice in the active site of HDAC6.
The tripeptide glutathione (GSH), namely γ-L-glutamyl-L-cysteinyl-glycine, is an ubiquitous low-molecular weight thiol nucleophile and reductant of utmost importance, representing the central redox agent of most aerobic organisms. GSH has vital functions involving also antioxidant protection, detoxification, redox homeostasis, cell signaling, iron metabolism/homeostasis, DNA synthesis, gene expression, cysteine/protein metabolism, and cell proliferation/differentiation or death including apoptosis and ferroptosis. Various functions of GSH are exerted in concert with GSH-dependent enzymes. Indeed, although GSH has direct scavenging antioxidant effects, its antioxidant function is substantially accomplished by glutathione peroxidase-catalyzed reactions with reductive removal of H2O2, organic peroxides such as lipid hydroperoxides, and peroxynitrite; moreover, the detoxifying function of GSH is basically exerted in conjuction with glutathione transferases, which have also antioxidant properties. GSH is synthesized in the cytosol by the ATP-dependent enzymes glutamate cysteine ligase, which is rate-limiting, and glutathione synthase; after its cell export, GSH is degraded extracellularly by the membrane-anchored ectoenzyme γ-glutamyl transferase, a process occurring, as GSH synthesis and export, in the γ-glutamyl cycle. GSH degradation occurs also intracellularly by the cytoplasmic enzymatic ChaC family of γ-glutamyl cyclotransferase. Synthesis and degradation of GSH, together with its export, translocation to cell organelles, utilization for multiple essential functions, and regeneration from glutathione disulfide by glutathione reductase, are relevant to GSH homeostasis and metabolism. Notably, GSH levels decline during aging, an alteration generally related to impaired GSH biosynthesis and leading to cell dysfunction. However, there is evidence of enhanced GSH levels in elderly subjects with excellent physical and mental health status, suggesting that heightened GSH may be a marker and even a causative factor of increased healthspan and lifespan. Such aspects, and much more, are considered in this state-of-the-art review, which deals with GSH and GSH-dependent enzymes from biochemistry to gerontology, focusing attention also on lifespan/healthspan extension and successful aging; the significance of GSH levels in aging is considered also in relation to therapeutic possibilities and supplementation strategies aimed at increasing appropriately GSH and related defenses to improve health status and counteract aging processes in humans.
Ticks transmit pathogens and harbour non-pathogenic, vertically transmitted intracellular bacteria termed endosymbionts. Almost all ticks studied to date contain 1 or more of Coxiella , Francisella , Rickettsia or Candidatus Midichloria mitochondrii endosymbionts, indicative of their importance to tick physiology. Genomic and experimental data suggest that endosymbionts promote tick development and reproductive success. Here, we review the limited information currently available on the potential roles endosymbionts play in enhancing tick metabolism and fitness. Future studies that expand on these findings are needed to better understand endosymbionts’ contributions to tick biology. This knowledge could potentially be applied to design novel strategies that target endosymbiont function to control the spread of ticks and pathogens they vector.
Diabetes mellitus (DM) is a huge global health issue and one of the most studied diseases, with a large global prevalence. Oxidative stress is a cytotoxic consequence of the excessive development of ROS and suppression of the antioxidant defense system for ROS elimination, which accelerates the progression of diabetes complications such as diabetic neuropathy, retinopathy, and nephropathy. Hyperglycaemia induced oxidative stress causes the activation of seven major pathways implicated in the pathogenesis of diabetic complications. These pathways increase the production of ROS and RNS, which contributes to dysregulated autophagy, gene expression changes, and the development of numerous pro-inflammatory mediators which may eventually lead to diabetic complications. This review will illustrate that oxidative stress plays a vital role in the pathogenesis of diabetic complications, and the use of antioxidants will help to reduce oxidative stress and thus may alleviate diabetic complications.
In recent years, there has been a significant increase in the concomitant incidence of Hashimoto’s thyroiditis (HT) and polycystic ovary syndrome (PCOS), both in terms of incidence, etiology, and clinical consequences. PCOS patients suffering from autoimmune thyroid diseases show insulin resistance, impaired glucose tolerance, weight gain, and metabolic and reproductive complications. Studies have shown that chronic stress and its consequence, i.e. oxidative stress, play an important role in the pathomechanism of both disorders. It has also been shown that long-term exposure to stress triggers biological mechanisms, in particular related to the regulation of the inflammatory cascade, which plays a key role in autoimmune diseases. The paper is a review of the literature on the role of chronic stress, oxidative stress, and immune processes in the pathogenesis of HT and PCOS. In addition, the review is a source of knowledge about the treatment of these diseases, and in particular the use of antioxidants in therapeutic management.
Background:
The primary malignant brain tumor glioblastoma multiforme (GBM) is most commonly detected in individuals over 60 years old. The standard therapeutic approach for GBM is radiotherapy combined with temozolomide. Recently, herbal products, such as alpha-lipoic acid (ALA) and auraptene (AUR), have shown promising anticancer effects on various cancer cells and animal models. However, it is not well understood how ALA, AUR, and their combination in GBM work to combat cancer. Thus, the purpose of this study was to investigate the antimetastatic effects of the ALA-AUR combination on U87 human glioblastoma cells.
Methods:
The inhibitory effects of ALA, AUR, and the ALA/AUR combination on the migration and metastasis of U87 cells were evaluated using a wound healing test and gelatin zymography. The expression levels of matrix metalloproteinase MMP-2 and MMP-9 were assessed at the transcriptional and translational levels using quantitative real-time polymerase chain reaction (qRT-PCR) and western blotting, respectively.
Results:
Our findings revealed that combination therapy reduced cell migration and metastasis, which was indicated by the reduction in MMP-2/-9 expression both at mRNA and protein levels, as well as their enzymatic activity in U87 cells.
Conclusion:
This study demonstrated that the combination of ALA and AUR effectively inhibited the migration and metastasis of U87 cells. Thus, given their safety and favorable specifications, the combination of these drugs can be a promising candidate for GBM treatment as primary or adjuvant therapy.
Cancer has become an important cause of mortality and morbidity in the world. Over the past decades, biomedical research revealed insights into the molecular events and signaling pathways involved in carcinogenesis and cancer progression. Matrix metalloproteinases (MMPs) are a diverse family of enzymes that can degrade various components of the extracellular matrix and are considered as potential diagnostic and prognostic biomarkers for many cancer types and cancer stages. Recently, studies on the role of natural-origin active substances in the prevention of cancer development gained importance. Among them, the α-lipoic acid, which is commonly found in plants, displayed potent anti-proliferative effects on cancer cell lines. However, the effect of the compound on the induction of apoptosis and mRNA expression of MMPs in human prostate cancer cells remains unclear. The present study aimed to evaluate the anti-proliferative and apoptotic activity of α-lipoic acid in human PC3 prostate carcinoma cells considering different concentrations and exposure durations. The findings showed that, α-lipoic acid significantly decreased PC3 cell viability with an IC50 value of 1.71 mM at 48 h (p < 0.05). Additionally, the compound significantly increased Annexin-V binding in cells compared to control and induced a significant alteration in mitochondrial membrane potential and caspase levels (p < 0.05). Furhermore, the RT-PCR analyses have revealed that α-lipoic acid reduced MMP-9 mRNA expression in PC3 cells compared to the control (p < 0.05). In conclusion, this study highlights that α-lipoic acid induced apoptosis in human PC3 prostate cancer cells and inhibited the MMP-9 gene at the mRNA level, which is known to play a role in metastasis development.
The Mediterranean diet is recognized as one of the healthiest available dietary patterns. This perception results from its beneficial effects on the cardiovascular system and, also, on hypertension, diabetes, and cancer compared with other diets. Its impact on the course of diabetes is assessed in the available scientific literature; however, little information is available about its impact on diabetic retinopathy. The MD is characterized mainly by the consumption of fish, seafood, foods of plant origin, and fresh fruit and vegetables. It is also recommended to consume legumes, which are a source of folic acid, magnesium, iron, and dietary fiber. High consumption of nuts and unrefined grains is also recommended in the MD. Marine fish provide polyunsaturated acids from the omega-3 group. Olive oil plays a very important role, especially olive oil obtained from mechanical pressing. Additionally, olive oil contains vitamins E, K, and polyphenols. Polyphenols, which are present in a diverse range of vegetables, fruits, and seeds, have the ability to decrease oxidative stress, inflammation, and insulin resistance. Resveratrol is naturally found in grape skins and seeds, as well as in peanuts and berries, and is a constituent of red wine. Resveratrol can inhibit increased vascular leakage and loss of pericytes and regulate the level of VEGF protein in the retina, thus inhibiting the development of DR. Consumption of fruits, vegetables, fish, and olive oil may be correlated with a lower risk of diabetic retinopathy. This paper presents the definition of the Mediterranean diet and its influence on the course of diabetes and diabetic retinopathy.
Evidence for the binding of lipoic (LA) and dihydrolipoic (DHLA) acid to bovine serum albumin (BSA) was sought as a feature for understanding the mechanism of their antioxidant activity and prevention of glycation. Experiments were performed by 1H high resolution NMR. The average binding ratio of LA, DHLA and tetranor LA to BSA were 10 +/- 2, 7.9 +/- 2 and 1.8 +/- 0.4 mol/mol BSA respectively. In this row the number of bound molecules lessens with the decrease of their hydrophobic interactions that correlates with their protective activity. Octanoic acid, the closest analog of lipoate, had a binding ratio of 4.7 +/- 0.5 mol. Lipoic acid was able to replace bound octanoic acid which points out that lipoate occupies the same binding site on BSA. Lipoate had no binding to low density lipoproteins extracted from human plasma which corresponds to its low protection of LDL against glycosylation and oxidative modification. This study indicates that lipoic acid molecules experience strong hydrophobic attraction and binding to BSA which is important part of lipoate protective mechanism.
The reduction, by thiol-disulfide exchange, of small model disulfides and insulin catalyzed by thioredoxin was determined spectrophotometrically from the oxidation of NADPH in the presence of thioredoxin reductase. The rate of reduction is variable due to the micro-environment of the disulfides. Cystine is reduced faster than the basic cystamine. The two interchain disulfides of bovine insulin and the corresponding S-S bonds of proinsulin were exceptionally good substrates for thioredoxin when compared with L-cystine. The K(m) value for insulin was 11 μM, and the pH optimum was 7.5. With 8 nM thioredoxin, the disulfides of insulin were reduced at a rate of 1.5 μM per min, equivalent to a turnover number for thioredoxin of 740 per min. The second order rate constant at pH 7.0 for oxidation of thioredoxin-(SH)2 with insulin disulfides was estimated from fluorescence measurements and the enzymatic rates to be around 1 x 105 M-1S-1. This is around 10,000 times higher than the second order rate constant for the reaction between insulin and dithiothreitol, demonstrating the high affinity of insulin for thioredoxin-(SH)2. Nondisulfide oxidants such as Cu2+ ions, diamide, and vitamin K3, which are known to mimic the effects of insulin on cellular hexose transport, were rapidly reduced by the thioredoxin system. The exceptional reactivity of insulin and thioredoxin-(SH)2, in vitro, is consistent with a physiological function for mammalian thioredoxin in the degradation of insulin. Functions for thioredoxin in the 'thiol oxidation-reduction model' of insulin action are discussed.
Thioredoxin from Escherichia coli was shown to catalyze the reduction of insulin disulfides by dithiothreitol. A quantitative assay was developed which measures the rate of insulin reduction spectrophotometrically at 650 nm as turbidity formation from the precipitation of the free insulin B chain. Thioredoxin, at 5 microM concentration, accelerated the reaction between 0.130 mM insulin and 1.0 mM dithiothreitol at pH 7 around 20-fold. The pH optimum of the reaction was 7.5. Thioredoxins from E. coli and calf liver showed similar specific activities. Stopped flow fluorescence measurements of the rate of reduction of thioredoxin-S2 by dithiothreitol showed a second order rate constant of 1647 M-1 s-1 at pH 7.2. This is between 10(2) to 10(3) times larger than the reaction between insulin or linear model disulfides and dithiothreitol. It is consistent with a ping-pong mechanism of thioredoxin catalysis since reduced thioredoxin is known to react very fast with insulin. Thioredoxin also catalyzed lipoamide-dependent reduction of the insulin disulfides in a coupled system with NADH, lipoamide, and lipoamide dehydrogenase. The fast spontaneous reaction between dihydrolipoamide and thioredoxin-S2 provides a mechanism for NADH or pyruvate-dependent disulfide reduction. The implication of the dithiol-disulfide oxidoreductase activity of thioredoxin for the regulation of enzyme activities by thiol oxidation-reduction control is discussed.
α-Lipoic acid has been oxidized (as its methyl ester, 3) by a variety of oxidants, including singlet oxygen. An nmr chemical shift reagent, Eu(fod)3-d27, has been used to show that the products include four thiolsulfinates in all cases, and, in the case of singlet oxygen oxidation, two thiolsulfonates. The singlet oxygen oxidations are interpreted in terms of a mechanism involving initial formation of zwitterions by reaction of singlet oxygen at each of the two sulfur atoms in 3 followed by intramolecular or intermolecular reaction to give thiolsulfonate or thiolsulfinate, respectively.
The reactivity of several thiols, including glutathione, dihydrolipoic acid, cysteine, N-acetyl cysteine, and ergothioneine, as well as several disulfides, toward different redox states of myoglobin, mainly met-myoglobin (HX-FeIII) and ferrylmyoglobin (HX-FeIV=O), was evaluated by optical spectral analysis, product formation, and thiyl free radical generation. Only dihydrolipoic acid reduced met-myoglobin to oxy-myoglobin, whereas all the other thiols tested did not interact with met-myoglobin. Although the redox transitions involved in the former reduction were expected to yield the dihydrolipoate thiyl radical, the reaction was EPR silent. Conversely, all thiols interacted to different extent with the high oxidation state of myoglobin, i.e. ferrylmyoglobin, via two processes. First, direct electron transfer to heme iron in ferrylmyoglobin (HX-FeIV=O) with formation of met-myoglobin (HX-FeIII) or oxymyoglobin (HX-FeIIO2); the former transition was effected by all thiols except dihydrolipoate, which facilitated the latter, i.e. the formation of the two-electron reduction product of ferrylmyoglobin. Second, nucleophilic addition onto a pyrrole in ferrylmyoglobin with subsequent formation of sulfmyoglobin. The contribution of either direct electron transfer to the heme iron or nucleophilic addition depended on the physicochemical properties of the thiol involved and on the availability of H2O2 to reoxidize met-myoglobin to ferrylmyoglobin. The thiyl radicals of glutathione, cysteine, and N-acetylcysteine were formed during the interaction of the corresponding thiols with ferrylmyoglobin and detected by EPR in conjunction with the spin trap 5,5'-dimethyl-1-pyroline-N-oxide. The intensity of the EPR signal was insensitive to superoxide dismutase and it was decreased, but not suppressed, by catalase. The disulfides of glutathione and cysteine did not react with ferrylmyoglobin, but the disulfide bridge in lipoic acid interacted efficiently with the ferryl species by either reducing directly the heme iron to form met-myoglobin or adding onto a pyrrole ring to form sulfmyoglobin; either process depended on the presence or absence of catalase (to eliminate the excess of H2O2) in the reaction mixture, respectively. The biological significance of the above results is discussed in terms of the occurrence and distribution of high oxidation states of myoglobin, its specific participation in cellular injury, and its potential interaction with biologically important thiols leading to either recovery of myoglobin or generation of nonfunctional forms of the hemoprotein as sulfmyoglobin.
Oxidative modification of low density lipoproteins (LDL) and their unrestricted scavenger receptor-dependent uptake is believed to account for cholesterol deposition in macrophage-derived foam cells. It has been suggested that vitamin E that is transported by LDL plays a critical role in protecting against LDL oxidation. We hypothesize that the maintenance of sufficiently high vitamin E concentrations in LDL can be achieved by reducing its chromanoxyl radicals, i.e., by vitamin E recycling. In this study we demonstrate that: i) chromanoxyl radicals of endogenous vitamin E and of exogenously added alpha-tocotrienol, alpha-tocopherol or its synthetic homologue with a 6-carbon side-chain, chromanol-alpha-C6, can be directly generated in human LDL by ultraviolet (UV) light, or by interaction with peroxyl radicals produced either by an enzymic oxidation system (lipoxygenase + linolenic acid) or by an azo-initiator, 2,2'-azo-bis(2,4-dimethylvaleronitrile) (AMVN; ii) ascorbate can recycle endogenous vitamin E and exogenously added chromanols by direct reduction of chromanoxyl radicals in LDL; iii) dihydrolipoic acid is not efficient in direct reduction of chromanoxyl radicals but recycles vitamin E by synergistically interacting with ascorbate (reduces dehydroascorbate thus maintaining the steady-state concentration of ascorbate); and iv) beta-carotene is not active in vitamin E recycling but may itself be protected against oxidative destruction by the reductants of chromanoxyl radicals. We suggest that the recycling of vitamin E and other phenolic antioxidants by plasma reductants may be an important mechanism for the enhanced antioxidant protection of LDL.
Reactive free radicals contained in cigarette smoke (CS) and compromised phagocytic antimicrobial activities including those of polymorphonuclear leukocytes (PMNs) have been implicated in the pathogenesis of severe CS-related pulmonary disorders. In CS-exposed buffer solutions, O2-. was the predominant generated reactive oxygen species, as demonstrated by lucigenin-amplified chemiluminescence and electron spin resonance (ESR) spin-trapping with 5,5-dimethyl-1-pyrroline N-oxide (DMPO). When PMNs were incubated in this buffer, phorbol 12-myristate 13-acetate (PMA)-stimulated active oxygen production and coupled O2 consumption were strongly impaired without appreciably affecting PMN viability (1-min exposure inhibited active oxygen production by 75%). Superoxide dismutase (SOD) totally protected and an iron chelator, diethylenetriaminepentaacetic acid (DETAPAC), also protected the CS-exposed PMNs, suggesting that generated O2-. was an initiating factor in the impairment and OH. generation was a subsequent injurious factor. Pretreatment of PMNs with antioxidants such as alpha-tocopherol and dihydrolipoic acid (DHLA) was partially protective. The results suggest that (i) O2-. is probably generated in the upper and lower respiratory tract lining fluid when they come in contact with CS; (ii) such generated O2-. can primarily impair PMN capabilities to generate reactive oxygen species; and (iii) since these effects may contribute to the pathogenesis of CS-related lung diseases, prior supplementation with antioxidants such as alpha-tocopherol or DHLA might be successful in preventing these deleterious effects.
It has been shown in vitro that dihydrolipoate (DL-6,8-dithioloctanoic acid) has antioxidant activity against microsomal lipid peroxidation. We tested dihydrolipoate for its neuroprotective activity using models of hypoxic and excitotoxic neuronal damage in vitro and rodent models of cerebral ischemia in vivo. In vitro, neuronal damage was induced in primary neuronal cultures derived form 7-day-old chick embryo telencephalon by adding either 1 mM cyanide or 1 mM glutamate to the cultures. Cyanide-exposed and dihydrolipoate-treated (10(-9)-10(-7) M) cultures showed an increased protein and ATP content compared with controls. The glutamate-exposed cultures treated with dihydrolipoate (10(-7)-10(-5) M) showed a decreased number of damaged neurons. In vivo, dihydrolipoate treatment (50 and 100 mg/kg) reduced brain infarction after permanent middle cerebral artery occlusion in mice and rats. Dihydrolipoate treatment (50 and 100 mg/kg) could not ameliorate neuronal damage in the rat hippocampus or cortex caused by 10 min of forebrain ischemia. A comparable neuroprotection was obtained by using dimethylthiourea, both in vitro (10(-7) and 10(-6) M) and at a dose of 750 mg/kg in the focal ischemia models. Lipoate, the oxidized form of dihydrolipoate, failed to reduce neuronal injury in any model tested. We conclude that dihydrolipoate, similarly to dimethylthiourea, is able to protect neurons against ischemic damage by diminishing the accumulation of reactive oxygen species within the cerebral tissue.
It has been shown that parameters of oxidative stress are increased in experimental diabetic neuropathy. The glutathione redox system is one of the intracellular scavenger systems for neutralizing free oxygen radicals. In this investigation we studied the effect of glutathione-treatment on the development of diabetic neuropathy in streptozotocin-induced diabetic rats by measuring sensory and motor nerve conduction velocities. The total study period was 10 weeks. Four groups of rats were studied: Group 1 consisted of non-diabetic, age-matched control rats; Group 2, of diabetic rats treated with placebo from week 0 to 10; Group 3, of diabetic rats treated with 200 mg glutathione/kg body weight i.v. two times per week from weeks 0 to 10; and Group 4, of diabetic rats treated with placebo from weeks 0 to 4 and as Group 3 from weeks 4 to 10. The sensory and motor nerve conduction velocity of rats treated prophylactically with glutathione (Group 3) were significantly different from those of rats treated with placebo (Group 2) or with glutathione administered at a later time point (Group 4). Complete restoration of sensory and motor nerve conduction velocity was not reached. There was a significant improvement in motor nerve conduction velocity from weeks 4 to 6 (p less than 0.005), but not in sensory nerve conduction velocity in the delayed treatment group (Group 4). In conclusion, treatment with glutathione, a free radical scavenger, is partially effective in the prevention of diabetic neuropathy in streptozotocin-induced diabetic rats, but is of limited value when the neuropathy is already present.
Nonenzymatic glycation has been found to increase in a variety of proteins in diabetic patients. The present study examined a possibility of preventing glycation and subsequent structural modifications of proteins by alpha-lipoic acid (thioctic acid) as lipoate, a substance which has gained attention as a potential therapeutic agent for diabetes-induced complications. Incubation of bovine serum albumin (BSA) at 2 mg/ml with glucose (500 mM) in a sterile condition at 37 degrees C for seven days caused glycation and structural modifications of BSA observed by SDS-PAGE, near UV absorption, tryptophan and nontryptophan fluorescence, and fluorescence of an extrinsic probe, TNS (6-(p-toluidinyl)naphthalene-2-sulfonate). When BSA and glucose were incubated in the presence of lipoate (20 mM), glycation and structural modifications of BSA were significantly prevented. Glycation and inactivation of lysozyme were also prevented by lipoate. These results suggest a potential for the therapeutic use of lipoic acid against diabetes-induced complications.
Twenty years ago, the enzyme superoxide dismutase which uses the superoxide radical anion as its specific substrate was reported. With this discovery was born a new scientific field, in which oxygen, necessary for aerobi c 1 ife on thi s planet, had to be cons i dered also in terms of its toxicity and stresses. This stimulated the search for knowledge of active oxygen species in biology and medicine. Superoxide and other reactive oxygen species are now implicated in many disease processes. Major advances have been achieved during these past years with respect to free radical generation and mechanisms of free radical action in causing tissue injury. In parallel, the possibil ity of influencing free radical related disease processes by antioxidant treatment was studied in various in vitro and in vivo systems. This was the unique theme of a conference organized in Paris by the Society for Free Radical Research (December 9-10, 1988) which brought together experts from basic sciences and clinicians in order to evaluate the current status of antioxidant therapy. The conference emphasized fundamental processes in antioxidant action. Among the major topics were superoxide dismutase (SOD) and low molecular weight substances with such activity, called SOD mimics. Other antioxidant enzymes were also considered. Antioxidant vitamins, in particular vitamins E and C, other naturally occurri ng antioxidants and vari ous synthet i c antioxidants were included in the presentations as there is now a rapidly developing series of compounds with potentially interesting clinical applications.
Antihypertensive agents have various effects on glucose metabolism; beta-blockers and thiazides were shown to reduce insulin sensitivity, calcium channel blockers seem to be inert, and α1-blockers and ACE-inhibitors (AI) tend to improve insulin stimulated glucose uptake after acute and chronic administration. It is, however, not known whether this improvement is caused by an increase in (muscular) blood flow - as both agents cause vasodilation - or whether there is a more specific effect on glucose uptake. We therefore choose a model of isolated muscle to minimize the influence of blood flow; we used an animal model of insulin resistance - the obese Zucker (fa/fa) rat - to test whether acute (3 h) oral administration of the AI trandolapril (without SU-groups) has a direct effect on insulin-stimulated glucose transport activity in skeletal muscle. In vitro glucose transport activity in the epitrochlearis muscle was assessed by 2-deoxyglucose uptake in the absence or presence of insulin (2 mU/ml). Insulin-stimulated 2-deoxyglucose uptake was only ~ 50% as great in muscles from obese animals compared to lean (Fa/-) controls (p < 0.05), but was significantly (p < 0.05) improved by acute (+33%, p < 0.05) treatment with trandolapril. We conclude that the isolated epitrochlearis muscle from the obese Zucker rat is a suitable model for studying insulin resistance in skeletal muscle; that trandolapril significantly improves insulin-stimulated glucose transport activity in skeletal muscle in the obese Zucker rat after acute administration and that SH groups do not seem to play any role. Our data therefore support the hypothesis that the ACE inhibitors as a group can improve glucose disposal via a direct effect on the skeletal muscle glucose transport system.
Oxidative damage to DNA can be caused by excited oxygen species, which are produced by radiation or are by-products of aerobic metabolism. The oxidized base, 8-hydroxydeoxyguanosine (oh8dG), 1 of approximately 20 known radiation damage products, has been assayed in the DNA of rat liver. oh8dG is present at a level of 1 per 130,000 bases in nuclear DNA and 1 per 8000 bases in mtDNA. Mitochondria treated with various prooxidants have an increased level of oh8dG. The high level of oh8dG in mtDNA may be caused by the immense oxygen metabolism, relatively inefficient DNA repair, and the absence of histones in mitochondria. It may be responsible for the observed high mutation rate of mtDNA.
1. Pigeon heart mitochondria produce H(2)O(2) at a maximal rate of about 20nmol/min per mg of protein. 2. Succinate-glutamate and malate-glutamate are substrates which are able to support maximal H(2)O(2) production rates. With malate-glutamate, H(2)O(2) formation is sensitive to rotenone. Endogenous substrate, octanoate, stearoyl-CoA and palmitoyl-carnitine are by far less efficient substrates. 3. Antimycin A exerts a very pronounced effect in enhancing H(2)O(2) production in pigeon heart mitochondria; 0.26nmol of antimycin A/mg of protein and the addition of an uncoupler are required for maximal H(2)O(2) formation. 4. In the presence of endogenous substrate and of antimycin A, ATP decreases and uncoupler restores the rates of H(2)O(2) formation. 5. Reincorporation of ubiquinone-10 and ubiquinone-3 to ubiquinone-depleted pigeon heart mitochondria gives a system in which H(2)O(2) production is linearly related to the incorporated ubiquinone. 6. The generation of H(2)O(2) by pigeon heart mitochondria in the presence of succinate-glutamate and in metabolic state 4 has an optimum pH value of 7.5. In states 1 and 3u, and in the presence of antimycin A and uncoupler, the optimum pH value is shifted towards more alkaline values. 7. With increase of the partial pressure of O(2) to the hyperbaric region the formation of H(2)O(2) is markedly increased in pigeon heart mitochondria and in rat liver mitochondria. With rat liver mitochondria and succinate as substrate in state 4, an increase in the pO(2) up to 1.97MPa (19.5atm) increases H(2)O(2) formation 10-15-fold. Similar pO(2) profiles were observed when rat liver mitochondria were supplemented either with antimycin A or with antimycin A and uncoupler. No saturation of the system with O(2) was observed up to 1.97MPa (19.5atm). By increasing the pO(2) to 1.97MPa (19.5atm), H(2)O(2) formation in pigeon heart mitochondria with succinate as substrate increased fourfold in metabolic state 4, with antimycin A added the increase was threefold and with antimycin A and uncoupler it was 2.5-fold. In the last two saturation of the system with oxygen was observed, with an apparent K(m) of about 71kPa (0.7-0.8atm) and a V(max.) of 12 and 20nmol of H(2)O(2)/min per mg of protein. 8. It is postulated that in addition to the well-known flavin reaction, formation of H(2)O(2) may be due to interaction with an energy-dependent component of the respiratory chain at the cytochrome b level.
Probably most diseases at some point during their course involve free radical reactions in tissue injury. In some cases, free radical reactions may be involved in multiple sites and at different stages of a chronic disease. So, both acute and degenerative diseases are thought to involve free radical reactions in tissue injury. An overview will be given of the evidence for the occurrence of free radicals and the importance of antioxidant interventions with particular reference to the lipophilic antioxidant vitamin E (tocopherols and tocotrienols).
In people with diabetes, glycation of apolipoproteins correlates with other indices of recent glycemic control, including HbA1. For several reasons, increased glycation of apolipoproteins may play a role in the accelerated development of atherosclerosis in diabetic patients. Recognition of glycated LDL by the classical LDL receptor is impaired, whereas its uptake by human monocyte-macrophages is enhanced. These alterations may contribute to hyperlipidemia and accelerated foam-cell formation, respectively. Glycation of LDL also enhances its capacity to stimulate platelet aggregation. The uptake of VLDL from diabetic patients by human monocyte-macrophages is enhanced. This enhancement may be due, at least in part, to increased glycation of its lipoproteins. Glycation of HDL impairs its recognition by cells and reduces its effectiveness in reverse cholesterol transport. Glycation of apolipoproteins may also generate free radicals, increasing oxidative damage to the apolipoproteins themselves, the lipids in the particle core, and any neighboring macromolecules. This effect may be most significant in extravasated lipoproteins. In these, increased glycation promotes covalent binding to vascular structural proteins, and oxidative reactions may cause direct damage to the vessel wall. Glycoxidation, or browning, of sequestered lipoproteins may further enhance their atherogenicity. Finally, glycated or glycoxidized lipoproteins may be immunogenic, and lipoprotein-immune complexes are potent stimulators of foam-cell formation.
Levels of iron, copper, zinc and manganese were measured by inductively coupled plasma spectroscopy in frozen postmortem brain tissue from patients with Parkinson's disease (PD), progressive supranuclear palsy (PSP), multiple system atrophy with strionigral degeneration (MSA), and Huntington's disease (HD) compared with control subjects. Total iron levels were found to be elevated in the areas of basal ganglia showing pathological change in these disorders. In particular, total iron content was increased in substantia nigra in PD, PSP and MSA, but not in HD. Total iron levels in the striatum (putamen and/or caudate nucleus) were increased in PSP, MSA and HD but not in PD. Total iron levels were decreased in the globus pallidus in PD. There was no consistent alterations of manganese levels in basal ganglia structures in any of the diseases studied. Copper levels were decreased in the substantia nigra in PD, and in the cerebellum in PSP, and were elevated in the putamen and possibly substantia nigra in HD. Zinc levels were only increased in PD, in substantia nigra and in caudate nucleus and lateral putamen.
Levels of the iron binding protein ferritin were measured in the same patient groups using a radio-immunoassay technique. increased iron levels in basal ganglia were generally associated with normal or elevated levels of ferritin immunoreactivity, for example, the substantia nigra in PSP and possibly MSA, and in putamen in MSA. The exception was PD where there was a generalized reduction in brain ferritin immunoreactivity, even in the substantia nigra.
An increase in total iron content appears to be a response to neurodegeneration in affected basal ganglia regions in a number of movement disorders. However, only in PD was there an increased total iron level, decreased ferritin content, decreased copper content, and an increased zinc concentration in substantia nigra. These findings suggest an alteration of iron handling in the substantia nigra in PD. Depending on the form in which the excess iron load exists in nigra in PD, it may contribute to the neurodegenerative process.
Previously we have shown that cell death in the substantia nigra (SN) in Parkinson's disease (PD) is associated with an increase in iron content but a decrease in the level of the iron-binding protein ferritin. Alterations in other metal ion levels were also observed; copper levels were reduced, whereas zinc levels were increased. The importance of these changes in iron, ferritin, and other metal ions in the pathophysiology of PD depends on whether they are specific to the illness. We measured levels of iron, copper, zinc, manganese, and ferritin in postmortem tissue from patients with progressive supranuclear palsy (PSP) and multiple system atrophy (MSA) (which shows pathology in the SN and striatum) and Huntington's disease (HD) (which shows pathological changes in the striatum, compared with control subjects). Total iron levels were elevated in areas of the basal ganglia showing pathological changes in these disorders. In particular, total iron content was increased in SN in PD, PSP, and MSA, but not in HD. Total iron levels in the striatum (caudate nucleus and/or putamen) were increased in PSP, MSA, and HD, but not in PD. There were no consistent alterations in manganese levels in the basal ganglia in any of the diseases studied. Copper levels were decreased in the SN in PD and in the cerebellum in PSP, and were elevated in the putamen and possibly the SN in HD. Zinc levels were only increased in PD in the SN, the caudate nucleus, and the putamen.(ABSTRACT TRUNCATED AT 250 WORDS)
Complexes formed by the dianions LH2− and L′2− deriving from dihydrolipoic acid (LH3) and dihydrolipoamide (L′H2), respectively, by substitution of the hydrogen atoms of the thiol groups with Ni(II), Co(Il), Hg(II) and Cu(I) ions were synthesized, isolated and characterized. In all these compounds the metal ions are coordinated to the thiolic sulfur atoms of the ligands. Potentiometric and spectroscopic data (IR, UV-Vis, EPR and XPS) obtained for these complexes or for their solutions are discussed.
1. Oxygen is a toxic gas - an introductionto oxygen toxicity and reactive species 2. The chemistry of free radicals and related 'reactive species' 3. Antioxidant defences Endogenous and Diet Derived 4. Cellular responses to oxidative stress: adaptation, damage, repair, senescence and death 5. Measurement of reactive species 6. Reactive species can pose special problems needing special solutions. Some examples. 7. Reactive species can be useful some more examples 8. Reactive species can be poisonous: their role in toxicology 9. Reactive species and disease: fact, fiction or filibuster? 10. Ageing, nutrition, disease, and therapy: A role for antioxidants?
1.1. Administration of α-lipoic acid to guinea pigs on a scorbutogenic diet appeared to afford about the same protection as a suboptimal amount of ascorbic acid. When small amounts of ascorbic acid and of α-lipoic acid were given, the combination protected the guinea pigs better than either compound alone.2.2. Male and female rats reared since weaning on a diet low in vitamin E did not reproduce. Administration of α-lipoic acid brought about reproduction although not to the same extent as that attained by an optimal amount of α-tocopherol. The offspring, maintained on the α-lipoic acid-supplemented, vitamin E-low diet, reproduced and weaned successfully a third generation.3.3. The efficacy of α-lipoic acid in alleviating symptoms of ascorbic acid and of tocopherol deficiencies can best be explained on the basis of a protective action exerted by α-lipoic acid or its dihydro derivative on the two vitamins.
We examine the evidence for free radical involvement and oxidative stress in the pathological process underlying Parkinson's disease, from postmortem brain tissue. The concept of free radical involvement is supported by enhanced basal lipid peroxidation in substantia nigra in patients with Parkinson's disease, demonstrated by increased levels of malondialdehyde and lipid hydroperoxides. The activity of many of the protective mechanisms against oxidative stress does not seem to be significantly altered in the nigra in Parkinson's disease. Thus, activities of catalase and glutathione peroxidase are more or less unchanged, as are concentrations of vitamin C and vitamin E. The activity of mitochondrial superoxide dismutase and the levels of the antioxidant ion zinc are, however, increased, which may reflect oxidative stress in substantia nigra. Levels of reduced glutathione are decreased in nigra in Parkinson's disease; this decrease does not occur in other brain areas or in other neurodegenerative illnesses affecting this brain region (i.e., multiple system atrophy, progressive supranuclear palsy). Altered glutathione metabolism may prevent inactivation of hydrogen peroxide and enhance formation of toxic hydroxyl radicals. In brain material from patients with incidental Lewy body disease (presymptomatic Parkinson's disease), there is no evidence for alterations in iron metabolism and no significant change in mitochondrial complex I function. The levels of reduced glutathione in substantia nigra, however, are reduced to the same extent as in advanced Parkinson's disease. These data suggest that changes in glutathione function are an early component of the pathological process of Parkinson's disease. The data presented suggest (1) there is oxidative stress in the substantia nigra at the time of death in advanced Parkinson's disease that manifests in terms of increased lipid peroxidation, superoxide dismutase activity, and zinc levels; (2) there is a major impairment of the glutathione pathway in Parkinson's disease; and (3) alterations in reduced glutathione levels may occur very early in the illness.
To find the mechanism of promotion process, we have investigated the antipromoting effects of radical scavengers and specific inhibitors for phospholipid metabolism and for protein kinase C using a two-stage transformation assay system in BALB/3T3 cells. All radical scavengers and inhibitors tested showed the antipromoting effects on 12-O-tetradecanoylphorbol-13-acetate (TPA)-promoted transformation. Diacylglycerols, activators of protein kinase C, showed promoting effects in vitro and the promoted-transformation by them was suppressed by radical scavengers employed. By an electron spin resonance (ESR) spin-trapping method, inhibitors, which suppressed promoted-transformation by TPA markedly, had .OH scavenging action. It was found using a ESR spin-trapping method that treatment of TPA on BALB/3T3 cells generates .OH in a dose-dependent manner. These results suggest that generation of oxygen radicals, especially .OH, which occurs in the processes of phospholipid metabolism as well as activation of protein kinase C, is essential to the promotion process.
The preparation and properties of physiologically relevant complexes of iron(II) and iron(III) with dihydrolipoic acid and dihydrolipoamide are described. Data obtained from measurements of the magnetic properties of the compounds are discussed along with results obtained by vibrational, electronic, EPR and Mössbauer spectroscopy. While iron(III) compounds present a low-spin, d5 configuration, iron(II) compounds present an intermediate spin state, S=1, d6 configuration.
The rate constants, k5, for abstraction by peroxyl radicals of the phenolic hydrogens from a number of phenols have been measured at 30°C. Values of k5 for α-, β-, γ-, and δ-tocopherols are 23.5, 16.6, 15.9, and 6.5 × 105 M-1 s-1, respectively. Like most other phenols these tocopherols react with two peroxyls per molecule and the reaction with peroxyls exhibits a substantial deuterium kinetic isotope effect. α-Tocopherol is the most reactive chain-breaking, phenolic antioxidant known. The simple model compound 4-methoxy-2,3,5,6-tetramethylphenol (TMMP) is much less reactive, with a k5 value of only 2.1 × 105 M-1 s-1. A better model compound is 2,2,5,7,8-pentamethyl-6-hydroxychroman (PMHC) which has a k5 value of 21.4 × 105 M-1 s-1. The low reactivity of TMMP compared with α-tocopherol and PMHC is attributed to stereoelectronic factors. In TMMP the methoxy group is twisted out of the plane of the aromatic ring by steric forces and, in consequence, the p-type lone pair on the methoxyl oxygen cannot help stabilize the phenoxyl formed upon abstraction of the phenolic hydrogen. However, in the tocopherols and in PMHC the chroman ring system holds the ethereal oxygen's p-type lone pair nearly perpendicular to the aromatic ring, thereby providing additional stabilization for the resultant phenoxyls. This hypothesis has been confirmed by X-ray analysis of TMMP and PMHC and of 4-methoxyphenol and 2,6-di-tert-butyl-4-methoxyphenol.
The high-yield syntheses in aqueous media of [Fe4S4(SR)4]2- (R = Ph, CH2CH2OH) using sulfur, sulfide, or thiosulfate as the source of core sulfide are reported. From the reagent mole ratio 6/1/1 HOCH2CH2SH/FeCl2/S in pH ∼8 aqueous buffer, a 65-70% yield of water-soluble (n-Pr4N)2[Fe4S4(SCH 2CH2OH)4] can be obtained. This result demonstrates for the first time that synthetic analogues of biological [4Fe-4S] centers will spontaneously self-assemble in completely aqueous solvent in the absence of any protein. The spontaneous self-assembly and stability of [Fe4S4(SCH2CH2OH)4] 2- in water raise the possibility that clusters containing the Fe4S4 core occur in vivo with natural thiols outside of proteins. With benzenethiol solubilized in water by Triton X-100, sulfide can be used in place of sulfur. A 70% spectrophotometric yield of [Fe4S4(SPh)4]2- is achieved in aqueous Triton mixtures of 5/1/1 PhSH/Fe3+/S2-. The addition of the biologically relevant dithiol D,L-dihydrolipoic acid (HSCH2CH2(H-S)CHCH2(CH2) 3COOH) at a dithiol/Fe mole ratio ≳2 greatly diminishes the rates of precipitation of iron sulfides and hydroxides and makes possible the assembly of [Fe4S4(SCH2CH2OH)4] 2- using sulfide. When the outer sulfur of thiosulfate furnishes core sulfide, D,L-dihydrolipoate can serve as both reducing and sulfur-transfer agent. In this case the conversion to sulfide is catalyzed by the sulfurtransferase rhodanese. Yields of [Fe4S4(SR)4]2- (R = Ph, CH2CH2OH) with the enzyme-mediated system routinely exceed 78% in solution and 60% as solid (Et4N)2[Fe4S4(SPh)4]. (Et4N)2[Fe2S2(SPh)4] contaminated by (Et4N)2[Fe4S4(SPh)4] can be obtained from the thiosulfate/rhodanese system if Et4NBr is added at the outset of the reaction. Under comparable conditions, the rates of reconstitution of Clostridium pasteurianum ferredoxin are 1-2 orders of magnitude faster than the rates of assembly of synthetic [Fe4S4(SR)4]2- determined in this work. Thus, the C. pasteurianum ferredoxin polypeptide appears to accelerate the assembly of its own [4Fe-4S] centers.
The thioredoxin peptide Trp-Cys-Gly-Pro-Cys-Lys, which contains the redox active dithiol, was found to be reduced by lipoamide in a coupled reaction with lipoamide dehydrogenase and NADH. The reduced peptide in turn was shown to reduce insulin, oxidized lens protein and glyceraldehyde-3-phosphate dehydrogenase. While the peptide is not as effective a catalyst for utilizing pyridine nucleotides to reduce protein disulfides as thioredoxin, it offers a system which may be developed to provide more efficient disulfide reduction. This is particularly relevant since no thioredoxin peptides have been found to be active with thioredoxin reductase.
Cellular protection against the deleterious effects of reactive oxidants generated in aerobic metabolism, called oxidative stress, is organized at multiple levels. Defense strategies include three levels of protection; prevention, interception, and repair. Regulation of the antioxidant capacity includes the maintenance of adequate levels of antioxidant and the localization of antioxidant compounds and enzymes. Short-term and long-term adaptation and cell specialisation in these functions are new areas of interest. Control over the activity of prooxidant enzymes, such as NADPH oxidase and NO synthases, is crucial. Synthetic antioxidants mimic biological strategies.
Rat liver lipoyl transacetylase catalyzes the formation of acetyl dihydrolipoic acid from acetyl coenzyme A and dihydrolipoic
acid. In an earlier paper the formation of acetyl dihydrolipoic from pyruvate and dihydrolipoic acid catalyzed by pyruvate
dehydrogenase has been reported. Acetyl dihydrolipoic acid is a substrate for citrate synthase, acetyl coenzyme A carboxylase
and fatty acid synthetase. The Vmax. for citrate synthase with acetyl dihydrolipoic acid was identical to acetyl coenzyme A (approximately 1 μmol citrate formed/min/mg
protein) while the apparent Km was approximately 4 times higher with acetyl dihydrolipoic acid as the substrate. This may be due to the fact that synthetic
acetyl dihydrolipoic acid is a mixture of 4 possible isomers and only one of them may be the substrate for the enzymatic reaction.
While dihydrolipoic acid can replace coenzyme A in the activation of succinate catalyzed by succinyl coenzyme A synthetase,
the transfer of coenzyme A between succinate and acetoacetyl dihydrolipoic acid catalyzed by succinyl coenzyme A: 3 oxo-acid
coenzyme A transferase does not occur.
Metabolic aberrations in diabetes such as hyperglycemia, ketonemia, ketonuria, reduced glycogen in tissues and reduced rates
of fatty acid synthesis in the liver are corrected by the administration of lipoic acid. Dithiol octanoic acid is formed from
lipoic acid by reduction and substitutes for Coenzyme A in several enzymatic reactions such as pyruvate dehydrogenase, citrate
synthase, acetyl Coenzyme A carboxylase, fatty acid synthetase, and triglyceride and phospholipid biosynthesis; but not in
the oxidation of fatty acids because of the slow rates of thiolysis of β-keto acyl dithioloctanoic acid. The overall effect
of these changes in the key enzymic activities is seen in the increased rates of oxidation of glucose and a reduction in fatty
acid oxidation in diabetes following lipoic acid administration.
Relative α-lipoic acid content of diabetic livers was considerably less than that of normal livers as determined by gas chromatography.
It was not possible to detect any dihydrolipoic acid in the livers. Biochemical abnormalities such as hyperglycaemia, ketonemia,
reduction in liver glycogen and impaired incorporation of [2-14C] -acetate into fatty acids in alloxan diabetic rats were brought to near normal levels by the oral or intraperitoneal administration
of dihydrolipoic acid. The effect of α-lipoic acid was comparable to that of dihydrolipoic acid in reducing the blood sugar
levels of diabetic rabbits during a glucose tolerance test.
The results suggest that the mode of action of lipoic acid was through stimulation of pyruvate dehydrogenase.
Intraperitoneal administration of lipoic acid (10 mg/100 g) does not effect changes in serum insulin levels in normal and
alloxan diabetic rats, while normalising increased serum pyruvate, and impaired liver pyruvic dehydrogenase characteristic
of the diabetic state. Dihydrolipoic acid has been shown to participate in activation of fatty acids with equal facility as
coenzyme A. Fatty acyl dihydrolipoic acid however is sparsely thiolyzed to yield acetyl dihydrolipoic acid. Also acetyl dihydrolipoic
acid does not activate pyruvate carboxylase unlike acetyl coenzyme A. The reduced thiolysis of Β-keto fatty acyl dihydrolipoic
acid esters and the lack of activation of pyruvic carboxylase by acetyl dihydrolipoic acid could account for the antiketotic
and antigluconeogenic effects of lipoic acid
Lipoic acid has been reported recently to be an effective antioxidant in biological systems. It may act in vivo through reduction to its dithiol form, dihydrolipoic acid. Using a dual Hg/Au electrode, and HPLC with electrochemical detection, a method was developed which allowed simultaneous measurement of lipoic acid and dihydrolipoic acid, at nanomolar levels. (RS)-α-Lipoic acid was added to human cells in tissue culture (Jurkat T-lymphocytes and primary neonatal diploid fibroblasts). Lipoic acid was converted rapidly by the cells to dihydrolipoic acid, which accumulated in the cell pellet. Monitored over a 2-hr interval, dihydrolipoic acid was released, and several-fold more dihydrolipoic acid could be found in the medium than in the pellet.
dl-[1,6-14C]Lipoic acid was synthesized and administered to rats or incubated in vitro with rat liver systems. The urinary excretion of radioactivity after labeled lipoate was administered intraperitoneally at a level of 0.5 mg/100 g body weight was maximal at 3–6 hr, with 60% of the injected radioactivity recovered within 24 hr. Respiratory 14CO2 from the same animals is maximal at 3 hr, after which it falls off markedly. Approximately 30% of the injected radioactivity was recovered as 14CO2 within 24 hr. The excretion of radioactivity after lipoate was administered by stomach tube was similar to that after intraperitoneal injection. Localization of radioactivity in the body was greatest in liver, intestinal contents, and muscle in all cases. Ionexchange and paper chromatographies of 24-hr pooled urine revealed several watersoluble radioactive metabolites. Incubation of [14C]lipoate with homogenates or mitochondrial preparations in vitro resulted in the production of 14CO2, which was decreased by incubation with unlabeled fatty acids and unaffected by the addition of carnitine or (+)-decanoylcarnitine. The rat, like certain bacteria, metabolizes lipoate via β-oxidation of the valeric acid side chain and by other metabolic reactions on the dithiolane ring, which render the molecule more water soluble.
1. Both NADH and NADPH supported the oxidation of adrenaline to adrenochrome in bovine heart submitochondrial particles. The reaction was completely inhibited in the presence of superoxide dismutase, suggesting that superoxide anions (O(2) (-)) are responsible for the oxidation. The optimal pH of the reaction with NADPH was at pH7.5, whereas that with NADH was at pH9.0. The reaction was inhibited by treatment of the preparation with p-hydroxymercuribenzoate and stimulated by treatment with rotenone. Antimycin A and cyanide stimulated the reaction to the same extent as rotenone. The NADPH-dependent reaction was inhibited by inorganic salts at high concentrations, whereas the NADH-dependent reaction was stimulated. 2. Production of O(2) (-) by NADH-ubiquinone reductase preparation (Complex I) with NADH or NADPH as an electron donor was assayed by measuring the formation of adrenochrome or the reduction of acetylated cytochrome c which does not react with the respiratory-chain components. p-Hydroxymercuribenzoate inhibited the reaction and rotenone stimulated the reaction. The effects of pH and inorganic salts at high concentrations on the NADH- and NADPH-dependent reactions of Complex I were essentially similar to those on the reactions of submitochondrial particles. 3. These findings suggest that a region between a mercurialsensitive site and the rotenone-sensitive site of the respiratory-chain NADH dehydrogenase is largely responsible for the NADH- and NADPH-dependent O(2) (-) production by the mitochondrial inner membranes.
The stabilities of the 1:1 complexes of Mn2+, Cu2+, and Zn2+ with lipoate and its chainshortened catabolites, viz., bisnorlipoate and tetranorlipoate, were studied by potentiometric titrations in water containing 50% dioxane (I = 0.1, NaClO4; 25 °C). A comparison of the stabilities of these complexes with those of simple carboxylates reveals that the catabolite complexes formed with Cu2+ and Zn2+ are more stable than expected from only the basicity of the carboxylate groups. This is evidence that chelates involving the disulfide group are formed. The stability of all Mn2+ complexes is determined by the basicity of the carboxylate groups. The same pattern of stability holds for the mixed-ligand complexes formed by Cu2+ or Zn2+, 2,2′-bipyridyl, and lipoate or one of its derivatives. It is evident that the disulfide group of the 1,2-dithiolane moiety can participate in the formation of binary and ternary complexes. The somewhat less-pronounced coordinating properties of the 1,2-dithiolane moiety compared with the tetrahydrothiophene moiety are discussed. It is apparent that the electron density at S(1) and S(2) in the dithiolane moiety of lipoate is not equivalent: S(1) is favored over S(2) in electrophilic reactions; possible biological implications are indicated.
The incidence of Amanita mushroom poisoning seems to be increasing in the United States. Its neurological aspects contribute importantly to morbidity and mortality. In reported series, mortality has ranged from 50 to 90%, and survival following the appearance of coma was exceptional. The cause of nervous system involvement was uncertain. In the patient presented here, clinical and electroencephalographic observations were consistent with severe hepatic encephalopathy and correlated closely with liver function abnormalities. Despite the development of coma, full recovery followed the use of thioctic acid, an experimental therapeutic agent.
This chapter discusses the biosynthesis of lipoic acid via unsaturated fatty acids. From in vivo experiments performed on the rat, it has been suggested that a metabolic relationship exists between unsaturated fatty acids and lipoic acid. According to this hypothesis, essential fatty acids may be the preferential precursors for lipoic acid biosynthesis through a yet unknown metabolic pathway. The fatty acids are obtained from the International Chemical and Nuclear Corporation. The specific radioactivity of [U-14C]linoleic acid and [U-14C]oleic acid is 250–500 mCi/mmol. The purity of the fatty acids can be checked by radio-gas chromatography, after esterification with anhydrous MeOH–HCl (1.1 N). Three different phases are observed: (H) = upper methanolic aqueous phase, (M) = fluffy phase (insoluble), and (L) = lower chloroformic phase containing the total lipids. The purification of the three phases is described in the chapter.
dl-[1,6-14C]Lipoic acid was administered by intraperitoneal injection to rats at the level of 0.5 mg/100 g body weight. Approximately 56% of the radioactivity was recovered in the urine. When acidified and extracted with benzene, 92% of the radioactivity remained in the aqueous phase. Gel-filtration and paper chromatography were used to identify three of the compounds in the benzene extract as lipoic, bisnorlipoic and tetranorlipoic acids. In addition, a keto compound appears to be present. The aqueous phase contained several radioactive components separable by ion-exchange and paper chromatographies. Two of these compounds were identified as lipoate and β-hydroxybisnorlipoate. No evidence for oxidation of the dithiolane ring of lipoic acid was observed. dl-[7,8-14C]Lipoic acid was administered to rats under the same conditions. The urine contained 81% of the radioactivity, 72% of which remained in the aqueous phase and 28% was extracted into benzene. In contrast to over 30% of the label from dl-(1,6-14C] lipoate being expired as 14CO2, a negligible amount of 14CO2 was produced by rats injected with dl-[7,8-14C]lipoate. The catabolites identified were the same as those found using the 1,6-labeled lipoate. Another dithiolane-intact compound was also isolated. It appears that the rat, similar to Pseudomonas putida LP, metabolizes lipoate mainly via β-oxidation of the valeric acid side chain.
89 randomized liver patients (42 with chronic hepatitis, 25 with hepatic cirrhosis, 14 with hepatitis of protracted evolution, 8 with alcohol-toxic adiposis hepatica, stage II) are reported, in whom considerable functionally and histologically identifiable therapeutic results were achieved by combined i.v. and oral treatment with thioctic acid. According to expectation, the most favourable results were found in alcohol-conditioned chronic liver diseases; however, also in chronic active hepatitis, resistant to treatment, a therapy could be promising. The oral therapy with thioctic acid, producing no side effects, is especially suited for the long-term outpatient treatment of chronic hepatitis and hepatic cirrhosis of toxic and posthepatic etiology.
To find the mechanism of promotion process, we have investigated the antipromoting effects of radical scavengers and specific inhibitors for phospholipid metabolism and for protein kinase C using a two-stage transformation assay system in BALB/3T3 cells. All radical scavengers and inhibitors tested showed the antipromoting effects on 12-O-tetradecanoylphorbol-13-acetate (TPA)-promoted transformation. Diacylglycerols, activators of protein kinase C, showed promoting effects in vitro and the promoted-transformation by them was suppressed by radical scavengers employed. By an electron spin resonance (ESR) spin-trapping method, inhibitors, which suppressed promoted-transformation by TPA markedly, had .OH scavenging action. It was found using a ESR spin-trapping method that treatment of TPA on BALB/3T3 cells generates .OH in a dose-dependent manner. These results suggest that generation of oxygen radicals, especially .OH, which occurs in the processes of phospholipid metabolism as well as activation of protein kinase C, is essential to the promotion process.
The influence of alpha-lipoic acid (CAS 62-46-4) on the amount of intracellular glutathione (GSH) was investigated in vitro and in vivo. Using murine neuroblastoma as well as melanoma cell lines in vitro, a dose-dependent increase of GSH content was observed. Dependent on the source of tumor cells the increase was 30-70% compared to untreated controls. Normal lung tissue of mice also revealed about 50% increase in glutathione upon treatment with lipoic acid. This corresponds with protection from irradiation damage in these in vitro studies. Survival rate of irradiated murine neuroblastoma was increased at doses of 100 micrograms lipoic acid/d from 2% to about 10%. In agreement with the in vitro studies, in vivo experiments with whole body irradiation (5 and 8 Gy) in mice revealed that the number of surviving animals was doubled at a dose of 16 mg lipoic acid/kg. Improvement of cell viability and irradiation protection by the physiological compound lipoic acid runs parallel with an increase of intracellular GSH/GSSG ratio.
Thioctic (lipoic) acid is used as a therapeutic agent in a variety of diseases in which enhanced free radical peroxidation of membrane phospholipids has been shown to be a characteristic feature. It was suggested that the antioxidant properties of thioctic acid and its reduced form, dihydrolipoic acid, are at least in part responsible for the therapeutic potential. The reported results on the antioxidant efficiency of thioctic and dihydrolipoic acids obtained in oxidation models with complex multicomponent initiation systems are controversial. In the present work we used relatively simple oxidation systems to study the antioxidant effects of dihydrolipoic and thioctic acids based on their interactions with: (1) peroxyl radicals which are essential for the initiation of lipid peroxidation, (2) chromanoxyl radicals of vitamin E, and (3) ascorbyl radicals of vitamin C, the two major lipid- and water-soluble antioxidants, respectively. We demonstrated that: (1) dihydrolipoic acid (but not thioctic acid) was an efficient direct scavenger of peroxyl radicals generated in the aqueous phase by the water-soluble azoinitiator 2,2'-azobis(2-amidinopropane)-dihydrochloride, and in liposomes or in microsomal membranes by the lipid-soluble azoinitiator 2,2'-azobis(2,4-dimethylvaleronitrile); (2) both dihydrolipoic acid and thioctic acid did not interact directly with chromanoxyl radicals of vitamin E (or its synthetic homologues) generated in liposomes or in the membranes by three different ways: UV-irradiation, peroxyl radicals of 2,2'-azobis(2,4-dimethylvaleronitrile), or peroxyl radicals of linolenic acid formed by the lipoxygenase-catalyzed oxidation; and (3) dihydrolipoic acid (but not thioctic acid) reduced ascorbyl radicals (and dehydroascorbate) generated in the course of ascorbate oxidation by chromanoxyl radicals. This interaction resulted in ascorbate-mediated dihydrolipoic acid-dependent reduction of the vitamin E chromanoxyl radicals, i.e. vitamin E recycling. We conclude that dihydrolipoic acid may act as a strong direct chain-breaking antioxidant and may enhance the antioxidant potency of other antioxidants (ascorbate and vitamin E) in both the aqueous and the hydrophobic membraneous phases.
Antioxidant properties of thioctic and dihydrolipoic acid have been demonstrated in membranes and low density lipoproteins (LDL) in vitro. In vivo studies with dietary supplementation of thioctic acid to rats showed that it can also protect tissues against oxidative damage. Presumably, this action is due to a thioctic acid dihydrolipoic acid (TA/DHLA) coupled antioxidant mechanism, which enhances the activity of other antioxidants (i.e. ascorbate, alpha-tocopherol) by regenerating them from their radical form. In the present study, thioctic acid proved to protect against ischemia/reperfusion injury to Langendorff perfused hearts. Hearts isolated from rats fed thioctic acid and subjected to ischemia exhibited better mechanical recovery (left ventricular developed pressure) after reperfusion and lower lactate dehydrogenase leakage. Thioctic acid supplementation also decreased the appearance of fluorescent lipid peroxidation products after ischemia/reperfusion, lowered the rate of 2,2'-azobis-(2,4-dimethylvaleronitrile) (AMVN) induced lipid peroxidation in heart homogenates, and prevented the loss of alpha-tocopherol. The total sulfhydryl group content in thioctic acid fed animals was higher and the decrease due to ischemia-reperfusion was not as marked in this group as observed in the control. These results show that dietary supplementation with thioctic acid in vivo provides protection against ischemia/reperfusion injury in the Langendorff heart model.