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(A): H&E staining of quadriceps and gastrocnemius muscle from 3–4 month-old WT and MCK-SIRT3M3 mice. (B): Fiber cross-section area of quadriceps and gastrocnemius muscle from 4.5 m old male WT and MCK-SIRT3M3 mice. n = 3–5. *P<0.05, **P<0.01 between WT and MCK-SIRT3M3 mice.
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We have previously reported that the expression of mitochondrial deacetylase SIRT3 is high in the slow oxidative muscle and that the expression of muscle SIRT3 level is increased by dietary restriction or exercise training. To explore the function of SIRT3 in skeletal muscle, we report here the establishment of a transgenic mouse model with muscle-...
Citations
... SIRT1 and SIRT3 also influence myoblast differentiation, with SIRT1 showing decreased expression during C2C12 differentiation. SIRT1 overexpression negatively affects myogenesis by downregulating myogenin, MEF2C, myosin heavy chain, and other differentiation-related genes [106,107]. Muscle-specific Sirt1 knockout mice exhibit altered gene expression related to skeletal muscle development, notably upregulating the embryonic myosin-heavy-chain isoform Myh3 [18]. Myf5 expression increases early in differentiation, and MEF2 overexpression enhances MyoD expression, promoting differentiation [108]. ...
... Despite being shorter, SIRT3M3 exhibits similar mitochondrial deacetylase activity compared to the full-length SIRT3 [115]. SIRT3 expression correlates with oxidative muscle types [54], and SIRT3M3 overexpression induces a transition to oxidative fibers, increases energy expenditure, and reduces muscle mass [107]. Conversely, SIRT3 knockout accelerates lean mass loss and shifts muscle fibers toward fast-twitch types [116]. ...
... SIRT3 achieves this by reducing protein acetylation in metabolic pathways such as the TCA cycle and fatty acid beta-oxidation [131]. Conversely, SIRT3M3 enhances muscle protein degradation by upregulating FoxO1 expression and increasing MuRF1 expression [107]. SIRT6 regulates muscle atrophy by modulating IGF/PI3K/AKT signaling and influencing the expression of atrogenes [132]. ...
The sirtuins constitute a group of histone deacetylases reliant on NAD⁺ for their activity that have gained recognition for their critical roles as regulators of numerous biological processes. These enzymes have various functions in skeletal muscle biology, including development, metabolism, and the body's response to disease. This comprehensive review seeks to clarify sirtuins' complex role in skeletal muscle metabolism, including glucose uptake, fatty acid oxidation, mitochondrial dynamics, autophagy regulation, and exercise adaptations. It also examines their critical roles in developing skeletal muscle, including myogenesis, the determination of muscle fiber type, regeneration, and hypertrophic responses. Moreover, it sheds light on the therapeutic potential of sirtuins by examining their impact on a range of skeletal muscle disorders. By integrating findings from various studies, this review outlines the context of sirtuin-mediated regulation in skeletal muscle, highlighting their importance and possible consequences for health and disease.
... Similarly, SIRT3, a mitochondrial sirtuin, directly and indirectly regulates AMPK by deacetylating LKB1 and other AMPK-regulating proteins, leading to AMPK phosphorylation and activation. The decrease in AMPK phosphorylation observed in the muscle tissue of SIRT3 knockout mice indicates that SIRT3 plays a positive role in AMPK activation [28,51,52]. Upon 1,25VD3 binding to VDR, coactivators are recruited, leading to increased AKT phosphorylation. ...
The onset of sarcopenia is associated with a decline in vitamin D receptor (VDR) expression, wherein reduced VDR levels contribute to muscle atrophy, while heightened expression promotes muscle hypertrophy. Like VDR, the age-related decline in protein deacetylase sirtuin (SIRT) expression is linked to the development of sarcopenia and age-related muscle dysfunction. This study aimed to investigate whether the VDR agonist 1,25-dihydroxyvitamin D3 (1,25VD3) exerts beneficial effects on muscles through interactions with sirtuins and, if so, the underlying molecular mechanisms. Treatment of 1,25VD3 in differentiating C2C12 myotubes substantially elevated VDR, SIRT1, and SIRT3 expression, enhancing their differentiation. Furthermore, 1,25VD3 significantly enhanced the expression of key myogenic markers, including myosin heavy chain (MyHC) proteins, MyoD, and MyoG, and increased the phosphorylation of AMPK and AKT. Conversely, VDR knockdown resulted in myotube atrophy and reduced SIRT1 and SIRT3 levels. In a muscle-wasting model triggered by IFN-γ/TNF-α in C2C12 myotubes, diminished VDR, SIRT1, and SIRT3 levels led to skeletal muscle atrophy and apoptosis. 1,25VD3 downregulated the increased expression of muscle atrophy-associated proteins, including FoxO3a, MAFbx, and MuRF1 in an IFN-γ/TNF-α induced atrophy model. Importantly, IFN-γ/TNF-α significantly reduced the mtDNA copy number in the C2C12 myotube, whereas the presence of 1,25VD3 effectively prevented this decrease. These results support that 1,25VD3 could serve as a potential preventive or therapeutic agent against age-related muscle atrophy by enhancing the VDR/SIRT1/SIRT3 axis.
... Similarly, SIRT3, a mitochondrial sirtuin, directly and indirectly regulates AMPK by deacetylating LKB1 and other AMPK-regulating proteins, leading to AMPK phosphorylation and activation. The decrease in AMPK phosphorylation observed in the muscle tissue of SIRT3 knockout mice indicates that SIRT3 plays a positive role in AMPK activation 13 [28,49,50]. Upon 1,25VD3 binding to VDR, coactivators are recruited, leading to increased AKT phosphorylation. ...
Age-related declines in vitamin D receptor (VDR) expression have been implicated in the onset of sarcopenia. The increased expression of VDR in muscle is known to increase muscle mass, whereas VDR knockout in the muscle decreases muscle mass in rats. Similar to VDR, the age-related decline in protein deacetylase sirtuin (SIRT) expression is linked to the development of sarcopenia and age-related muscle dysfunction. This study aimed to investigate whether the VDR agonist 1,25-dihydroxyvitamin D3 (1,25VD3) exerts beneficial effects on muscles through interactions with sirtuins and, if so, the underlying molecular mechanisms. 1,25VD3 treatment increases the expression of VDR, SIRT1, and SIRT3 in C2C12 myotubes. Additionally, it stimulates the differentiation of C2C12 myoblasts into myotubes. Furthermore, 1,25VD3 significantly enhanced the expression of key myogenic markers, including myosin heavy chain (MyHC) proteins (MyHC I and II), MyoD, and MyoG, and increased the phosphorylation of AMPK and AKT. Conversely, VDR knockdown in myoblasts induces myotube atrophy by downregulating SIRT1 and SIRT3 expression. Furthermore, 1,25VD3 ameliorated muscle atrophy and apoptosis induced by IFN-γ/TNF-α co-treatment to C2C12 myotube. Moreover, 1,25VD3 downregulated the increased expression of muscle atrophy-associated proteins, including FoxO3a, MAFbx, and MuRF1 in IFN-γ/TNF-α induced atrophy model. Importantly, IFN-γ/TNF-α significantly reduced the mtDNA copy number in C2C12 myotube, whereas the presence of 1,25VD3 effectively prevented this decrease. These results indirectly suggest that 1,25VD3 has the potential to develop as a therapeutic or preventive agent for age-mediated muscle atrophy by enhancing the VDR/SIRT1/SIRT3 axis and inhibiting the FoxO3-mediated atrophy pathway.
... The quadriceps of mice were fixed and embedded in a cassette and immersed in formalin before being sliced and followed by H&E staining [17]. Then, quadriceps samples were examined using Tissue Cytometer (TissueGnostics, Vienna, Australia; magnification, x200). ...
Both quercetin and leucine have been shown to exert moderately beneficial effects in preventing muscle atrophy induced by cancers or chemotherapy. However, the combined effects of quercetin and leucine, as well as the possible underlying mechanisms against cisplatin (CDDP)-induced muscle atrophy and cancer-related fatigue (CRF) remain unclear. To investigate the issues, male BALB/c mice were randomly assigned to the following groups for 9 weeks: Control, CDDP (3 mg/kg/week), CDDP+Q (quercetin 200 mg/kg/day administrated by gavage), CDDP+LL (a diet containing 0.8% leucine), CDDP+Q+LL, CDDP+HL (a diet containing 1.6% leucine), and CDDP+Q+HL. The results showed that quercetin in combination with LL or HL synergistically or additively attenuated CDDP-induced decreases in maximum grip strength, fat and muscle mass, muscle fiber size and MyHC level in muscle tissues. However, the combined effects on locomotor activity were less than additive. The combined treatments decreased the activation of the Akt/FoxO1/atrogin-1/MuRF1 signaling pathway (associated with muscle protein degradation), increased the activation of the mTOR and E2F-1 signaling pathways (associated with muscle protein synthesis and cell cycle/growth, respectively). The combined effects on signaling molecules present in muscle tissues were only additive or less. In addition, only Q+HL significantly increased glycogen levels compared to the CDDP group, while the combined treatments considerably decreased CDDP-induced proinflammatory cytokine and MCP-1 levels in the triceps muscle. Using tumor-bearing mice, we demonstrated that the combined treatments did not decrease the anticancer effect of CDDP. In conclusion, this study suggests that the combination of quercetin and leucine enhanced the suppressed effects on CDDP-induced muscle weakness and CRF through downregulating muscle atrophy and upregulating the glycogen level in muscle tissues without compromising the anticancer effect of CDDP. Multiple mechanisms, including regulation of several signaling pathways and decrease in proinflammatory mediator levels in muscles may contributed to the enhanced protective effect of the combined treatments on muscle atrophy.
... Mitochondrial acetylation reduces mitochondrial function via inhibiting ATP generation, hormone synthesis, and calcium regulation [50]. SIRT3 is a mitochondrial deacetylase encoded in the nucleus, transported to and imported into the mitochondria where it regulates acetylation of mitochondrial proteins [51,52] such as complexes I, II, and IV [31,32,53]. With late-onset hypoxia, the increased mitochondrial acetylation corresponds to the decrease in SIRT3 activity in males or no change in females. ...
Chronic intrauterine hypoxia is a significant pregnancy complication impacting fetal heart growth, metabolism, and mitochondrial function, contributing to cardiovascular programming of the offspring. PGC1α (peroxisome proliferator-activated receptor γ co-activator 1α) is the master regulator of mitochondrial biogenesis. We investigated the effects of hypoxia on PGC1α expression following exposure at different gestational ages. Time-mated pregnant guinea pigs were exposed to normoxia (NMX, 21% O 2 ) or hypoxia (HPX, 10.5% O 2 ) at either 25-day (early-onset) or 50-day (late-onset) gestation, and all fetuses were extracted at term (term = ~65-day gestation). Expression of nuclear PGC1α, sirtuin 1 (SIRT1), AMP-activated protein kinase (AMPK), and mitochondrial sirtuin 3 (SIRT3) was measured, along with SIRT3 activity and mitochondrial acetylation of heart ventricles of male and female fetuses. Early-onset hypoxia increased ( P <0.05) fetal cardiac nuclear PGC1α and had no effect on mitochondrial acetylation of either growth-restricted males or females. Late-onset hypoxia had either no effect or decreased ( P <0.05) PCC1α expression in males and females, respectively, but increased ( P <0.05) mitochondrial acetylation in both sexes. Hypoxia had variable effects on expression of SIRT1, AMPK, SIRT3, and SIRT3 activity depending on the sex. The capacity of the fetal heart to respond to hypoxia differs depending on the gestational age of exposure and sex of the fetus. Further, the effects of late-onset hypoxia on fetal heart function impose a greater risk to male than female fetuses, which has implications toward cardiovascular programming effects of the offspring.
... Previous studies have reported that FOXO1 inhibits early differentiation of myoblasts and regulates the type of skeletal muscle fibers, with transgenic mice exhibiting significantly reduced skeletal muscle mass, impaired muscle function, and reduced abundance of slow fiber-related gene expression [36,37]. The FOXO1 protein mainly exerts its function in the nucleus. ...
This study aimed to explore the regulatory role of FOXO1 promoter methylation on its transcriptional level and unravel the effect of FOXO1 on the proliferation and differentiation of bovine myoblasts. Bisulfite sequencing polymerase chain reaction (BSP) and real-time quantitative PCR were performed to determine the methylation status and transcript levels of the FOXO1 promoter region at different growth stages. BSP results showed that the methylation level in the calf bovine (CB) group was significantly higher than that in the adult bovine (AB) group (p < 0.05). On the other hand, qRT-PCR results indicated that the mRNA expression level in the AB group was significantly higher than that in the CB group (p < 0.05), suggesting a significant decrease in gene expression at high levels of DNA methylation. CCK-8 and flow cytometry were applied to determine the effect of silencing the FOXO1 gene on the proliferation of bovine myoblasts. Furthermore, qRT-PCR and Western blot were conducted to analyze the expression of genes associated with the proliferation and differentiation of bovine myoblasts. Results from CCK-8 revealed that the short hairpin FOXO1 (shFOXO1) group significantly promoted the proliferation of myoblasts compared to the short-hairpin negative control (shNC) group (p < 0.05). Flow cytometry results showed a significant decrease in the number of the G1 phase cells (p < 0.05) and a significant increase in the number of the S phase cells (p < 0.05) in the shFOXO1 group compared to the shNC group. In addition, the expression of key genes for myoblast proliferation (CDK2, PCNA, and CCND1) and differentiation (MYOG, MYOD, and MYHC) was significantly increased at both mRNA and protein levels (p < 0.05). In summary, this study has demonstrated that FOXO1 transcription is regulated by methylation in the promoter region and that silencing FOXO1 promotes the proliferation and differentiation of bovine myoblasts. Overall, our findings lay the foundation for further studies on the regulatory role of epigenetics in the development of bovine myoblasts.
... A treadmill endurance protocol was performed using an Exer-3/6 open treadmill (Columbus Instruments, Columbus, OH, USA) similar to previously described [40]. Mice started the test at 6 m/min. ...
The orexigenic hormone ghrelin has multifaceted roles in health and disease. We have reported that ablation of the ghrelin receptor, growth hormone secretagogue receptor (GHS-R), protects against metabolic dysfunction of adipose tissues in aging. Our further observation interestingly revealed that GHS-R deficiency phenocopies the effects of myokine irisin. In this study, we aim to determine whether GHS-R affects the metabolic functions of aging skeletal muscle and whether GHS-R regulates the muscular functions via irisin. We first studied the expression of metabolic signature genes in gastrocnemius muscle of young, middle-aged and old mice. Then, old GHS-R knockout (Ghsr−/−) mice and their wild type counterparts were used to assess the impact of GHS-R ablation on the metabolic characteristics of gastrocnemius and soleus muscle. There was an increase of GHS-R expression in skeletal muscle during aging, inversely correlated with the decline of metabolic functions. Remarkedly the muscle of old GHS-R knockout (Ghsr−/−) mice exhibited a youthful metabolic profile and better maintenance of oxidative type 2 muscle fibers. Furthermore, old Ghsr−/− mice showed improved treadmill performance, supporting better functionality. Also intriguing to note was the fact that old GHS-R-ablated mice showed increased expression of the irisin precursor FNDC5 in the muscle and elevated plasma irisin levels in circulation, which supports a potential interrelationship between GHS-R and irisin. Overall, our work suggests that GHS-R has deleterious effects on the metabolism of aging muscle, which may be at least partially mediated by myokine irisin.
... As reported in the results sections, significant improvements were reported after both RT [33] or ET [34], while at present the impact of CT has not been investigated yet. On the other hand, the present results suggest positive effects of both ET and RT in mitochondrial quality, suggesting benefits in terms of metabolic flexibility of muscle and possible effects in muscle mass and OXPHOS protein expression regulation [53,55]. ...
Background
Previous evidence showed that cellular aging is a multifactorial process that is associated with decline in mitochondrial function. Physical exercise has been proposed as an effective and safe therapeutical intervention to improve the mitochondria network in the adult myocytes.
Aims
The aim of this systematic review of randomized controlled trials (RCTs) was to assess the exercise-induced muscle mitochondria modifications in older adults, underlining the differences related to different exercise modalities.
Methods
On November 28th, 2021, five databases (PubMed, Scopus, Web of Science, Cochrane, and PEDro) were systematically searched for RCTs to include articles with: healthy older people as participants; physical exercise (endurance training (ET), resistance training (RT), and combined training (CT)) as intervention; other different exercise modalities or physical inactivity as comparator; mitochondrial modifications (quality, density and dynamics, oxidative, and antioxidant capacity) as outcomes. The quality assessment was performed according to the PEDro scale; the bias risk was evaluated by Cochrane risk-of-bias assessment tool.
Results
Out of 2940 records, 6 studies were included (2 assessing ET, 2 RT, 1 CT, and 1 both ET and RT). Taken together, 164 elderly subjects were included in the present systematic review. Significant positive effects were reported in terms of mitochondrial quality, density, dynamics, oxidative and antioxidant capacity, even though with different degrees according to the exercise type. The quality assessment reported one good-quality study, whereas the other five studies had a fair quality.
Discussion
The overall low quality of the studies on this topic indicate that further research is needed.
Conclusion
RT seems to be the most studied physical exercise modality improving mitochondrial density and dynamics, while ET have been related to mitochondrial antioxidant capacity improvements. However, these exercise-induced specific effects should be better explored in older people.
... No one metric encompasses all aspects of exercise capacity. Although there is no consensus terminology, experimental studies generally focus on measuring 1 of 2 distinct entities: the endurance capacity 2 or the maximum exercise capacity, 3 which intuitively are akin to the capacity to run a marathon versus a sprint and reflect largely distinct physiological traits. This dichotomy in performance types between sustainable and unsustainable exercise states can be made precise using the concepts of critical velocity and power, which represent a theoretical threshold between the two. ...
Acute and chronic animal models of exercise are commonly used in research. Acute exercise testing is used, often in combination with genetic, pharmacological, or other manipulations, to study the impact of these manipulations on the cardiovascular response to exercise and to detect impairments or improvements in cardiovascular function that may not be evident at rest. Chronic exercise conditioning models are used to study the cardiac phenotypic response to regular exercise training and as a platform for discovery of novel pathways mediating cardiovascular benefits conferred by exercise conditioning that could be exploited therapeutically. The cardiovascular benefits of exercise are well established, and, frequently, molecular manipulations that mimic the pathway changes induced by exercise recapitulate at least some of its benefits. This review discusses approaches for assessing cardiovascular function during an acute exercise challenge in rodents, as well as practical and conceptual considerations in the use of common rodent exercise conditioning models. The case for studying feeding in the Burmese python as a model for exercise-like physiological adaptation is also explored.
... SIRT1 and SIRT3 change the mitochondrial function in a similar manner. SIRT3, being localized within the mitochondria, regulates several mitochondrial proteins such as succinate dehydrogenase (SDH), FOXO3, manganese-dependent superoxide dismutase (Mn-SOD), and acetyl-CoA synthase [53]. During periods of fasting, mitochondrial oxidative phosphorylation is increased in part due to the expression of Sirt3, where SIRT3 is also suggested to regulate oxidative muscle fiber formation [53,54]. ...
... SIRT3, being localized within the mitochondria, regulates several mitochondrial proteins such as succinate dehydrogenase (SDH), FOXO3, manganese-dependent superoxide dismutase (Mn-SOD), and acetyl-CoA synthase [53]. During periods of fasting, mitochondrial oxidative phosphorylation is increased in part due to the expression of Sirt3, where SIRT3 is also suggested to regulate oxidative muscle fiber formation [53,54]. Absence of SIRT3 in mice is linked with direct downregulatory effects on PGC-1α and effect mitochondrial biogenesis [55]. ...
The nicotinamide adenine dinucleotide (NAD⁺) is an essential redox cofactor, involved in various physiological and molecular processes, including energy metabolism, epigenetics, aging, and metabolic diseases. NAD⁺ repletion ameliorates muscular dystrophy and improves the mitochondrial and muscle stem cell function and thereby increase lifespan in mice. Accordingly, NAD⁺ is considered as an anti-oxidant and anti-aging molecule. NAD⁺ plays a central role in energy metabolism and the energy produced is used for movements, thermoregulation, and defense against foreign bodies. The dietary precursors of NAD⁺ synthesis is targeted to improve NAD⁺ biosynthesis; however, studies have revealed conflicting results regarding skeletal muscle-specific effects. Recent advances in the activation of nicotinamide phosphoribosyltransferase in the NAD⁺ salvage pathway and supplementation of NAD⁺ precursors have led to beneficial effects in skeletal muscle pathophysiology and function during aging and associated metabolic diseases. NAD⁺ is also involved in the epigenetic regulation and post-translational modifications of proteins that are involved in various cellular processes to maintain tissue homeostasis. This review provides detailed insights into the roles of NAD⁺ along with molecular mechanisms during aging and disease conditions, such as the impacts of age-related NAD⁺ deficiencies on NAD⁺-dependent enzymes, including poly (ADP-ribose) polymerase (PARPs), CD38, and sirtuins within skeletal muscle, and the most recent studies on the potential of nutritional supplementation and distinct modes of exercise to replenish the NAD⁺ pool.
