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Partial least squares discriminant analysis (PLS-DA) of neurochemical profiles of striatum (row a), motor cortex (row b) and brainstem (row c) of G93A-SOD1 mice and WT mice at P60. The score plots of two components (the left column) (i.e. PC1 and PC2) discriminate regional profiles of G93A-SOD1 mice from those of WT mice at P60. The plots of loading factors (the right column) show the weighting contributions of each metabolite ratio in the principal components.
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In vivo ¹H magnetic resonance spectroscopy (¹H-MRS) investigations of amyotrophic lateral sclerosis (ALS) mouse brain may provide neurochemical profiles and alterations in association with ALS disease progression. We aimed to longitudinally follow neurochemical evolutions of striatum, brainstem and motor cortex of mice transgenic for G93A mutant hu...
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Amyotrophic lateral sclerosis (ALS) is a progressive disease of neuronal degeneration in the motor cortex, brainstem, and spinal cord, resulting in impaired motor function and premature demise as a result of insufficient respiratory drive. ALS is associated with dysfunctions in neurons, neuroglia, muscle cells, energy metabolism, and glutamate bala...
Citations
... SnRNAseq of prefrontal cortex from PD and age-matched control individuals demonstrated the upregulation of pathways related to detoxification of heavy metals in PD astrocytes compared to controls (Zhu et al., 2022; Table 1, GSE202210). Glial activation characterizes also ALS and its mouse SOD1 G93A model (Lei et al., 2019). Phenotypic alterations were found in SOD1 G93A spinal cord where astrocytes presented transcriptional changes in genes involved in complement activation and lipid metabolism (MacLean et al., 2022; Table 1, GSE173524), and in SOD1 G93A cortex, where astrocytes displayed dysregulation in genes associated with ion homeostasis and Wnt signaling (Miller et al., 2018; Table 1, GSE111031). ...
The central nervous system (CNS) is characterized by an intricate composition of diverse cell types, including neurons and glia cells (astrocytes, oligodendrocytes, and microglia), whose functions may differ along time, between sexes and upon pathology. The advancements in high-throughput transcriptomics are providing fundamental insights on cell phenotypes, so that molecular codes and instructions are ever more described for CNS physiology and neurodegeneration. To facilitate the search of relevant information, this review provides an overview of key CNS transcriptomics studies ranging from CNS development to ageing and from physiology to pathology as defined for five neurodegenerative disorders and their relative animal models, with a focus on molecular descriptions whose raw data were publicly available. Accurate phenotypic descriptions of cellular states correlate with functional changes and this knowledge may support research devoted to the development of therapeutic strategies supporting CNS repair and function.
... In particular, astrocytes provide essential trophic, metabolic, and protective support to neurons, and a dysregulation of astrocytic functions has been shown to contribute to several pathogenic mechanisms occurring in ALS [22,23]. For instance, a reduced expression/activity of glial glutamate transporters, as well as an elevated extracellular concentration of glutamate, have been reported in the CNS of both patients and animal models of ALS, contributing to excitotoxic damages to neurons [24][25][26][27][28][29]. Importantly, the metabolic crosstalk between motor neurons and astrocytes also appears disrupted. ...
Alterations in the activity of the regulator of cell metabolism AMP-activated protein kinase (AMPK) have been reported in motor neurons from patients and animal models of amyotrophic lateral sclerosis (ALS). Considering the key role played by astrocytes in modulating energy metabolism in the nervous system and their compromised support towards neurons in ALS, we examined whether a putative alteration in AMPK expression/activity impacted astrocytic functions such as their metabolic plasticity and glutamate handling capacity. We found a reduced expression of AMPK mRNA in primary cultures of astrocytes derived from transgenic rats carrying an ALS-associated mutated superoxide dismutase (hSOD1G93A). The activation of AMPK after glucose deprivation was reduced in hSOD1G93A astrocytes compared to non-transgenic. This was accompanied by a lower increase in ATP levels and increased vulnerability to this insult, although the ATP production rate did not differ between the two cell types. Furthermore, soliciting the activity of glutamate transporters was found to induce similar AMPK activity in these cells. However, manipulation of AMPK activity did not influence glutamate transport. Together, these results suggest that the altered AMPK responsiveness in ALS might be context dependent and may compromise the metabolic adaptation of astrocytes in response to specific cellular stress.
... Due to differences in transgene, symptom development and life span, it remains difficult to compare these findings to those in other commonly used ALS rodent models, such as the SOD1 model. In this mouse model, carrying the SOD1 G93A mutation, Lei et al. reported no significant effect on glucose utilization in motor-related brain regions (Lei et al., 2018). In addition, the correlation of behavioral symptoms to imaging findings may identify pivotal disease-related phenomena in future studies. ...
... Elevations in the Glx levels at the 2-and 6-month time points suggest an alteration in glutamatergic transmission creating an imbalance between the excitatory and inhibitory neuronal activity in both regions. In correspondence with our findings, Lei and colleagues showed increased levels of glutamate in the motor cortex of presymptomatic SOD1 G93A transgenic animals (Lei et al., 2018;Weerasekera et al., 2018). The glutamate-glutamine cycling in the glia and neurons is a complex process, where the enzyme glutamine synthetase plays a vital role. ...
Currently TAR DNA binding protein 43 (TDP-43) pathology, underlying Amyotrophic Lateral Sclerosis (ALS), remains poorly understood which hinders both clinical diagnosis and drug discovery efforts. To better comprehend the disease pathophysiology, positron emission tomography (PET) and multi-parametric magnetic resonance imaging (mp-MRI) provide a non-invasive mode to investigate molecular, structural, and neurochemical abnormalities in vivo. For the first time, we report the findings of a longitudinal PET-MR study in the TDP-43 A315T ALS mouse model, investigating disease-related changes in the mouse brain. 2-deoxy-2-[ 18 F]fluoro-D-glucose [ 18 F]FDG PET showed significantly lowered glucose metabolism in the motor and somatosensory cor-tices of TDP-43 A315T mice whereas metabolism was elevated in the region covering the bilateral substantia nigra, reticular and amygdaloid nucleus between 3 and 7 months of age, as compared to non-transgenic controls. MR spectroscopy data showed significant changes in glutamate + glutamine (Glx) and choline levels in the motor cortex and hindbrain of TDP-43 A315T mice compared to controls. Cerebral blood flow (CBF) measurements, using an arterial spin labelling approach, showed no significant age-or group-dependent changes in brain perfusion. Diffusion MRI indices demonstrated transient changes in different motor areas of the brain in TDP-43 A315T mice around 14 months of age. Cytoplasmic TDP-43 proteinaceous inclusions were observed in the brains of symptomatic , 18-month-old mice, but not in non-symptomatic transgenic or wild-type mice. Our results reveal that disease-and age-related functional and neurochemical alterations, together with limited structural changes, occur in specific brain regions of transgenic TDP-43 A315T mice, as compared to their healthy counterparts. Altogether these findings shed new light on TDP-43 A315T disease pathogenesis and may prove useful for clinical management of ALS.
... Additionally, our finding of increased myo-inositol level in the spinal cord of female and male transgenic mice points towards microglial activation, a phenomenon reported in Table 3 Concentration (µmol/g) of 13 C labeled metabolites from [1,6-13 C 2 ]glucose in SOD1 G37R and WT mice Mice were infused with [1,6-13 C 2 ]glucose for 10 min. The concentrations of 13 C labeled metabolites were measured in 1 H-[ 13 C]-NMR spectra of brain tissue extracts using [2-13 C]glycine as reference SOD1 G93A mice [25,43,44]. The elevated level of m-Ino is associated with neuroinflammation in different neurological [45] and hypertonic conditions [46]. ...
Amyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative disorder with selective degeneration of motor neurons in the central nervous system. The pathophysiology of ALS is not well understood. We have used ¹H-[¹³C]-NMR spectroscopy together with an administration of [1,6-¹³C2]glucose and [2-¹³C]acetate in female and male SOD1G37R mice to assess neuronal and astroglial metabolic activity, respectively, in the central nervous system in ALS condition. The female (p = 0.0008) and male (p < 0.0001) SOD1G37R mice exhibited decreased forelimb strength when compared with wild-type mice. There was a reduction in N-acetylaspartylglutamate level, and elevation in myo-inositol in the spinal cord of female and male SOD1G37R mice. The transgenic male mice exhibited increased acetate oxidation in the spinal cord (p = 0.05) and cerebral cortex (p = 0.03), while females showed an increase in the spinal cord (p = 0.02) only. As acetate is transported and preferentially metabolized in the astrocytes, the finding of increased rate of acetate oxidation in the transgenic mice is suggestive of astrocytic involvement in the pathogenesis of ALS. The rates of glucose oxidation in glutamatergic (p = 0.0004) and GABAergic neurons (p = 0.0052) were increased in the cerebral cortex of male SOD1G37R mice when compared with the controls. The female mice showed an increase in glutamatergic (p = 0.039) neurometabolic activity only. The neurometabolic activity was unperturbed in the spinal cord of either sex. These data suggest differential changes in neurometabolic activity across the central nervous system in SOD1G37R mice.
... Interestingly, lactate was also shown to modulate neuronal activity levels and plasticity [135], rendering it an important molecule potentially involved in alterations of the motor neuron circuitry in ALS. Notably, reduced lactate levels were detected in the motor cortex of SOD1 G93A tg mice by in vivo 1 H magnetic resonance spectroscopy ( 1 H-MRS) already during the early symptomatic phase [135,137,138], as well as in a SOD1 G93A tg astrocyte-MN (wt) co-culture system (Figure 3, Madji Hounoum et al. [139]). . Altered molecular profile of astrocytes in ALS. ...
Amyotrophic lateral sclerosis (ALS) is a fatal disease characterized by the degeneration of cortical and spinal motor neurons. With no effective treatment available to date, patients face progressive paralysis and eventually succumb to the disease due to respiratory failure within only a few years. Recent research has revealed the multifaceted nature of the mechanisms and cell types involved in motor neuron degeneration, thereby opening up new therapeutic avenues. Intriguingly, two key features present in both ALS patients and rodent models of the disease are cortical hyperexcitability and hyperconnectivity, the mechanisms of which are still not fully understood. We here recapitulate current findings arguing for cell autonomous and non-cell autonomous mechanisms causing cortical excitation and inhibition imbalance, which is involved in the degeneration of motor neurons in ALS. Moreover, we will highlight recent evidence that strongly indicates a cardinal role for the motor cortex as a main driver and source of the disease, thus arguing for a corticofugal trajectory of the pathology.
... Many studies have shown that the broad prospects of mouse models in the mechanism and therapy research of ALS. [36][37][38][39][40][41] It is reported that UBQLN2-P497H overexpression mice have pathological phenomena of neuron loss, behavioral defects, and protein aggregation. [42][43][44] Another UBQLN2-P497H mice expressing about 20% endogenous level using NF-H neuron promoter was reported, and no obvious pathological phenomenon was found. ...
Aims
The ubiquilin‐like protein ubiquilin 2 (UBQLN2) is associated with amyotrophic lateral sclerosis and frontotemporal degeneration (ALS/FTD). The biological function of UBQLN2 has previously been shown to be related to stress granules (SGs). In this study, we aimed to clarify the regulatory relationship between UBQLN2 and SGs.
Methods
In this study, we transfected UBQLN2‐WT or UBQLN2‐P497H plasmids into cell lines (HEK293T, HeLa), and observed the process of SG dynamics by immunofluorescence. Meanwhile, immunoblot analyses the protein changes of stress granules related components.
Results
We observed that ubiquilin 2 colocalizes with the SG component proteins G3BP1, TIA‐1, ATXN2, and PABPC1. In cells expressing WT UBQLN2 or P497H mutants, in the early stages of SG formation under oxidative stress, the percentage of cells with SGs and the number of SGs per cell decreased to varying degrees. Between WT and mutant, there was no significant difference in eIF2α activity after stress treatment. Interestingly, the UBQLN2 P497H mutant downregulates the level of TIA‐1. In addition, the overexpression of the UBQLN2 P497H mutant inhibited the phosphorylation of 4E‐BP1 and affected the nucleoplasmic distribution of TDP‐43.
Conclusions
Ubiquilin 2 colocalizes with the SG component proteins G3BP1, TIA‐1, ATXN2, and PABPC1. It participates in regulating SG dynamics. And UBQLN2 mutation affects the assembly of stress granules by regulating TIA‐1. In addition, the overexpression of the UBQLN2 P497H mutant inhibited the phosphorylation of 4E‐BP1 and affected the nuclear and cytoplasmic distribution of TDP‐43. These provide new insights into the role of UBQLN2 in oxidative stress and the pathogenesis of ALS.
... However, recent studies detected neurochemical or glucose-metabolism abnormalities in brain stem and cortex of ALS animals using magnetic resonance spectroscopy, suggesting that the above abnormalities may contribute to early differential diagnosis between patients with ALS and FOSMN. 8,9 It remains controversial whether FOSMN is a neurodegenerative disease, an inflammatory disease, or a mix of pathophysiological mechanisms. Minimal response to immunomodulation therapy with refractory progression suggests that ...
... Indeed, lactate measurements in CNS tissue from different regions of SOD-1G93A mice have yielded different results. In some studies, the metabolite was found diminished, like in lumbar segments from SOD1G93A mice at presymptomatic stages, coincident with results from culture media [29] and with recent findings in other CNS regions (brain stem, striatum, and motor cortex) obtained by in vivo 1 H magnetic resonance spectroscopy at different stages [102]. Conversely, in a recent study performed in 2 SOD1G93A models (fast and slow progressing), Valbuena et al. [103] found no differences in lactate levels at the lumbar spinal cord in any stages (presymptomatic, onset, and late stage) of disease, but an increase in the thoracic segments at the end stage of disease, in agreement with previous findings [104]. ...
ALS is a human neurodegenerative disorder that induces a progressive paralysis of voluntary muscles due to motor neuron loss. The causes are unknown, and there is no curative treatment available. Mitochondrial dysfunction is a hallmark of ALS pathology; however, it is currently unknown whether it is a cause or a consequence of disease progression. Recent evidence indicates that glial mitochondrial function changes to cope with energy demands and critically influences neuronal death and disease progression. Aberrant glial cells detected in the spinal cord of diseased animals are characterized by increased proliferation rate and reduced mitochondrial bioenergetics. These features can be compared with cancer cell behavior of adapting to nutrient microenvironment by altering energy metabolism, a concept known as metabolic reprogramming. We focus on data that suggest that aberrant glial cells in ALS undergo metabolic reprogramming and profound changes in glial mitochondrial activity, which are associated with motor neuron death in ALS. This review article emphasizes on the association between metabolic reprogramming and glial reactivity, bringing new paradigms from the area of cancer research into neurodegenerative diseases. Targeting glial mitochondrial function and metabolic reprogramming may result in promising therapeutic strategies for ALS.
... What is known about lactate and the ANLS in ALS? Cell culture and animal experiments indicate a lactate deficiency in ALS. Using in vivo 1 H magnetic resonance spectroscopy ( 1 H-MRS) approach Lei et al. (2019) observed a reduction of lactate in SOD1 G93A tg mice most prominently seen in motor cortex, starting at the early symptomatic phase in motor cortex and in the late symptomatic stage also in brainstem. In an astrocyte-MN co-culture system of tg astrocytes with WT MN, lactate was reduced, when compared to cultures containing WT astrocytes, indicating defects in the generation or release of lactate by astrocytes (Ferraiuolo et al., 2011;Madji Hounoum et al., 2017; Figure 4 and Supplementary Table 3). ...
Amyotrophic lateral sclerosis (ALS) is a fatal disease, characterized by the degeneration of both upper and lower motor neurons. Despite decades of research, we still to date lack a cure or disease modifying treatment, emphasizing the need for a much-improved insight into disease mechanisms and cell type vulnerability. Altered neuronal excitability is a common phenomenon reported in ALS patients, as well as in animal models of the disease, but the cellular and circuit processes involved, as well as the causal relevance of those observations to molecular alterations and final cell death, remain poorly understood. Here, we review evidence from clinical studies, cell type-specific electrophysiology, genetic manipulations and molecular characterizations in animal models and culture experiments, which argue for a causal involvement of complex alterations of structure, function and connectivity of different neuronal subtypes within the cortical and spinal cord motor circuitries. We also summarize the current knowledge regarding the detrimental role of astrocytes and reassess the frequently proposed hypothesis of glutamate-mediated excitotoxicity with respect to changes in neuronal excitability. Together, these findings suggest multifaceted cell type-, brain area- and disease stage- specific disturbances of the excitation/inhibition balance as a cardinal aspect of ALS pathophysiology.
... Furthermore, 1 H MRS provides evidence that increased adenosine is strongly correlated with phosphocreatine, creatine and their ratio, which reflects the adenosine diphosphate(ADP)/ATP ratio (Lei et al., 2019;Rao et al., 2010;Tkac et al., 2012). Therefore, studying cortical responses, including cortical blood flow (cCBF) and metabolic information, at different hypoglycemic phases by means of perfusion MRI and short-echo 1 H MRS techniques would allow researchers to characterize the metabolic status of each hypoglycemic phase. ...
... vised multivariate statistical tool that can seek a decision function based on a large number of metabolites for a clear separation of different groups(Lei et al., 2019). Without assuming data to be normally distributed, it provides insight into seeking significant metabolites that contribute to the causes of discrimination via the corresponding weights and loadings of each metabolite. ...
Hypoglycemia is critical condition during diabetic treatment that involves intensive insulin therapy, and it may impair brain function. We aimed to compare cortical responses of three hypoglycemic phases and the restoration of glycemia to control levels after a severe episode in rats using non‐invasive perfusion magnetic resonance (MR) imaging and localized ¹H MR spectroscopy. Under light α‐chloralose anesthesia, cortical blood flow (cCBF) was 42 ± 3 ml/100 g/min at euglycemia (~ 5 mM plasma glucose), was not altered at mild hypoglycemia I (42 ± 4 ml/100 g/min, 2–3.5 mM), increased to 60 ± 8 ml/100 g/min under moderate hypoglycemia II (1–2 mM) and amplified to 190 ± 35 ml/100 g/min at severe hypoglycemia III (< 1 mM). ¹H MRS revealed metabolic changes at hypoglycemia I without any perfusion alteration. At hypoglycemia III, glutamine and glutamate decreased, whereas aspartate increased. When animals subsequently regained glycemic control, not all metabolites returned to their control levels, for example, glutamine. Meanwhile, ascorbate was increased with amplified hypoglycemic severity, whereas glutathione was reduced; these compounds did not return to normal levels upon the restoration of glycemia. Our study is the first to report cCBF and neurochemical changes in cortex upon five glycemic stages. The cortical responses of different hypoglycemic phases would explain variable neuronal damages after hypoglycemia and might help identify the degrees of hypoglycemic insults and further improve alternative therapies.
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