Caloric restriction shortens lifespan through an increase in lipid peroxidation, inflammation and apoptosis in the G93A mouse, an animal model of ALS

Neuroprotective effects of dantrolene in neurodegenerative disease: Role of inhibition of pathological inflammation

Neurodegenerative diseases (NDs) refer to a group of diseases in which slow, continuous cell death is the main pathogenic event in the nervous system. Most NDs are characterized by cognitive dysfunction or progressive motor dysfunction. Treatments of NDs mainly target alleviating symptoms, and most NDs do not have disease-modifying drugs. The pathogenesis of NDs involves inflammation and apoptosis mediated by mitochondrial dysfunction. Dantrolene, approved by the US Food and Drug Administration, acts as a RyRs antagonist for the treatment of malignant hyperthermia, spasticity, neuroleptic syndrome, ecstasy intoxication and exertional heat stroke with tolerable side effects. Recently, dantrolene has also shown therapeutic effects in some NDs. Its neuroprotective mechanisms include the reduction of excitotoxicity, apoptosis and neuroinflammation. In summary, dantrolene can be considered as a potential therapeutic candidate for NDs.

Nutrigenomic profiling of reduced specification diets and phytogenic inclusion effects on critical TLR signaling, MAPK-apoptosis and PI3K-Akt-mTOR gene components along the broiler gut

The effects of concurrent reduction of dietary metabolizable energy (ME) and crude protein (CP) levels combined or not with the dietary inclusion of a phytogenic feed additive (PFA) were studied using a nutrigenomics approach. In particular, the expression of 26 critical genes relevant for inflammation control (TLR pathway), cellular apoptosis (MAPK pathway) cell growth and nutrient metabolism (PI3K-Akt-mTOR pathway) was profiled along the broiler intestine. Two dietary types (L and H) differing in metabolizable energy and crude protein levels (L: 95% and H: 100% of optimal Cobb 500 recommendations for ME and CP requirements) supplemented or not with PFA (- or +) and their interactions (L-, L+, H-, H+) were evaluated. There were only 3 total interactions (mTOR, IL8, and HRAS P < 0.05) between diet type and PFA inclusion indicating limited concurrent effects. Diet type, L upregulated genes related with inflammation mainly in the jejunum, ileum, and cecum (P < 0.05) and MAPK pathway in the ileum and cecum (P < 0.05). Moreover, diet type L negatively affected the expression of genes related to PI3K-Akt-mTOR pathway mainly in duodenum and cecum (P < 0.05). On the other hand, PFA inclusion downregulated (P < 0.05) genes related with TLR signaling pathway (TLR2B, MyD88, TLR3, IL8, LITAF) along the intestine and MAPK pathway genes (APO1, FOS) in jejunum (P < 0.05). Finally, PFA supplementation regulated nutrient sensing and metabolism in the cecum in a manner perceived as beneficial for growth. In conclusion, the study results highlight that the reduced ME and CP specifications, especially in the absence of PFA, regulate inflammation, apoptosis and nutrient metabolism processes at homeostatic control levels that hinder maximizing the availability of dietary energy and nutrients for growth purposes. Inclusion of PFA helped to adjust the respective homeostatic responses and control to levels supporting broiler performance, especially at reduced specification diets.

Comparing therapeutic modulators of the SOD1 G93A Amyotrophic Lateral Sclerosis mouse pathophysiology

Introduction

Amyotrophic Lateral Sclerosis (ALS) is a paralyzing, multifactorial neurodegenerative disease with limited therapeutics and no known cure. The study goal was to determine which pathophysiological treatment targets appear most beneficial.

Methods

A big data approach was used to analyze high copy SOD1 G93A experimental data. The secondary data set comprised 227 published studies and 4,296 data points. Treatments were classified by pathophysiological target: apoptosis, axonal transport, cellular chemistry, energetics, neuron excitability, inflammation, oxidative stress, proteomics, or systemic function. Outcome assessment modalities included onset delay, health status (rotarod performance, body weight, grip strength), and survival duration. Pairwise statistical analysis (two-tailed t-test with Bonferroni correction) of normalized fold change (treatment/control) assessed significant differences in treatment efficacy. Cohen's d quantified pathophysiological treatment category effect size compared to "all" (e.g., all pathophysiological treatment categories combined).

Results

Inflammation treatments were best at delaying onset (d = 0.42, p > 0.05). Oxidative stress treatments were significantly better for prolonging survival duration (d = 0.18, p < 0.05). Excitability treatments were significantly better for prolonging overall health status (d = 0.22, p < 0.05). However, the absolute best pathophysiological treatment category for prolonging health status varied with disease progression: oxidative stress was best for pre-onset health (d = 0.18, p > 0.05); excitability was best for prolonging function near onset (d = 0.34, p < 0.05); inflammation was best for prolonging post-onset function (d = 0.24, p > 0.05); and apoptosis was best for prolonging end-stage function (d = 0.49, p > 0.05). Finally, combination treatments simultaneously targeting multiple pathophysiological categories (e.g., polytherapy) performed significantly (p < 0.05) better than monotherapies at end-stage.

Discussion

In summary, the most effective pathophysiological treatments change as function of assessment modality and disease progression. Shifting pathophysiological treatment category efficacy with disease progression supports the homeostatic instability theory of ALS disease progression.

Apoptosis and its therapeutic implications in neurodegenerative diseases

Neurodegenerative disorders are characterized by progressive loss of particular populations of neurons. Apoptosis has been implicated in the pathogenesis of neurodegenerative diseases, including Parkinson disease, Alzheimer disease, Huntington disease, and amyotrophic lateral sclerosis. In this review, we focus on the existing notions relevant to comprehending the apoptotic death process, including the morphological features, mediators and regulators of cellular apoptosis. We also highlight the evidence of neuronal apoptotic death in Parkinson disease, Alzheimer disease, Huntington disease, and amyotrophic lateral sclerosis. Additionally, we present evidence of potential therapeutic agents that could modify the apoptotic pathway in the aforementioned neurodegenerative diseases and delay disease progression. Finally, we review the clinical trials that were conducted to evaluate the use of anti-apoptotic drugs in the treatment of the aforementioned neurodegenerative diseases, in order to highlight the essential need for early detection and intervention of neurodegenerative diseases in humans.

Effects of dietary restriction on neuroinflammation in neurodegenerative diseases

Recent and accumulating work in experimental animal models and humans shows that diet has a much more pervasive and prominent role than previously thought in modulating neuroinflammatory and neurodegenerative mechanisms leading to some of the most common chronic central nervous system (CNS) diseases. Chronic or intermittent food restriction has profound effects in shaping brain and peripheral metabolism, immunity, and gut microbiome biology. Interactions among calorie intake, meal frequency, diet quality, and the gut microbiome modulate specific metabolic and molecular pathways that regulate cellular, tissue, and organ homeostasis as well as inflammation during normal brain aging and CNS neurodegenerative diseases, including Alzheimer's disease, Parkinson's disease, amyotrophic lateral sclerosis, and multiple sclerosis, among others. This review discusses these findings and their potential application to the prevention and treatment of CNS neuroinflammatory diseases and the promotion of healthy brain aging.

Exploring Molecular Approaches in Amyotrophic Lateral Sclerosis: Drug Targets from Clinical and Pre-Clinical Findings

Amyotrophic lateral sclerosis (ALS) is a fatal motor neuron disease (MND) characterized by the death of upper and lower motor neurons (corticospinal tract) in the motor cortex, basal ganglia, brain stem, and spinal cord. The patient experiences the sign and symptoms between 55 to 75 years of age, which include impaired motor movement, difficulty in speaking and swallowing, grip loss, muscle atrophy, spasticity, and sometimes associated with memory and cognitive impairments. Median survival is 3 to 5 years after diagnosis and 5 to 10% of the patients live for more than 10 years. The limited intervention of pharmacologically active compounds, that are used clinically, is majorly associated with the narrow therapeutic index. Pre-clinically established experimental models, where neurotoxin methyl mercury mimics the ALS like behavioural and neurochemical alterations in rodents associated with neuronal mitochondrial dysfunctions and downregulation of adenyl cyclase mediated cAMP/CREB, is the main pathological hallmark for the progression of ALS in central as well in the peripheral nervous system. Despite the considerable investigation into neuroprotection, it still constrains treatment choices to strong care and organization of ALS complications. Therefore, this current review specially targeted the investigation of clinical and pre-clinical features available for ALS to understand the pathogenic mechanisms and to explore the pharmacological interventions associated with the up-regulation of intracellular adenyl cyclase/cAMP/ CREB and activation of mitochondrial-ETC coenzyme-Q10 as a future drug target in the amelioration of ALS mediated motor neuronal dysfunctions.

Metabolic Dysfunction in Spinal Muscular Atrophy

Spinal muscular atrophy (SMA) is an autosomal recessive genetic disorder leading to paralysis, muscle atrophy, and death. Significant advances in antisense oligonucleotide treatment and gene therapy have made it possible for SMA patients to benefit from improvements in many aspects of the once devastating natural history of the disease. How the depletion of survival motor neuron (SMN) protein, the product of the gene implicated in the disease, leads to the consequent pathogenic changes remains unresolved. Over the past few years, evidence toward a potential contribution of gastrointestinal, metabolic, and endocrine defects to disease phenotype has surfaced. These findings ranged from disrupted body composition, gastrointestinal tract, fatty acid, glucose, amino acid, and hormonal regulation. Together, these changes could have a meaningful clinical impact on disease traits. However, it is currently unclear whether these findings are secondary to widespread denervation or unique to the SMA phenotype. This review provides an in-depth account of metabolism-related research available to date, with a discussion of unique features compared to other motor neuron and related disorders.

Longevity pathways in stress resistance: targeting NAD and sirtuins to treat the pathophysiology of hemorrhagic shock

Stress resistance correlates with longevity and this pattern has been exploited to help identify genes that can influence lifespan. Reciprocally, genes and pharmacological agents that have been studied primarily in the context of longevity may be an untapped resource for treating acute stresses. Here we summarize the evidence that targeting SIRT1, studied primarily in the context of longevity, can improve outcomes in hemorrhagic shock and resuscitation. Hemorrhagic shock is a potentially fatal condition that occurs when blood loss is so severe that tissues no longer receive adequate oxygen. While stabilizing the blood pressure and reperfusing tissues are necessary, re-introducing oxygen to ischemic tissues generates a burst of reactive oxygen species that can cause secondary tissue damage. Reactive oxygen species not only exacerbate the inflammatory cascade but also can directly damage mitochondria, leading to bioenergetic failure in the affected tissues. Treatments with polyphenol resveratrol and with nicotinamide adenine dinucleotide (NAD) precursors have both shown promising results in rodent models of hemorrhagic shock and resuscitation. Although a number of different mechanisms may be at play in each case, a common theme is that resveratrol and NAD both enhance the activity of SIRT1. Moreover, many of the physiologic improvements observed with resveratrol and NAD precursors are consistent with modulation of known SIRT1 targets. Because small blood vessels and limited blood volume make mice very challenging for the development of hemorrhagic shock models, there is a paucity of direct genetic evidence testing the role of SIRT1. However, the development of more robust methods in mice as well as genetic modifications in rats should allow the study of SIRT1 transgenic and KO rodents in the near future. The potential therapeutic effect of SIRT1 in hemorrhagic shock may serve as an important example supporting the value of considering "longevity" pathways in the mitigation of acute stresses.

The potential interplay between energy metabolism and innate complement activation in amyotrophic lateral sclerosis

Amyotrophic lateral sclerosis (ALS) is a fatal and rapidly progressing motor neuron disease without effective treatment. Although the precise mechanisms leading to ALS are yet to be determined, there is now increasing evidence implicating the defective energy metabolism and components of the innate immune complement system in the onset and progression of its motor phenotypes. This review will survey the mechanisms by which the energy metabolism and the complement system are altered during the disease progression of ALS and how it can contribute to disease. Furthermore, it will also examine how complement activation can modify the energy metabolism in metabolic disorders, in order to highlight how the complement system and energy metabolism may be linked in ALS.

Risk Factors and Emerging Therapies in Amyotrophic Lateral Sclerosis

Amyotrophic lateral sclerosis (ALS) is a fatal progressive neurodegenerative disease characterized by a permanent degeneration of both upper and lower motor neurons. Many different genes and pathophysiological processes contribute to this disease, however its exact cause remains unclear. Therefore, it is necessary to understand this heterogeneity to find effective treatments. In this review, we focus on selected environmental and genetic risk factors predisposing to ALS and highlight emerging treatments in ALS therapy. Of numerous defective genes associated with ALS, we focus on four principal genes that have been identified as definite causes of ALS: the SOD1 gene, C9orf72, TDP-43, as well as the recently identified TBK1. We also provide up-to-date information on selected environmental factors that have historically been considered as key players in ALS development and pathogenesis. In parallel to our survey of known risk factors, we also discuss emerging ALS stem cell therapies and experimental medicines currently undergoing phase II and III clinical trials.

Insulin and Autophagy in Neurodegeneration

Crosstalk in the pathophysiological processes underpinning metabolic diseases and neurodegenerative disorders have been the subject of extensive investigation, in which insulin signaling and autophagy impairment demonstrate to be a common factor in both conditions. Although it is still somewhat conflicting, pharmacological and genetic strategies that regulate these pathways may be a promising approach for aggregate protein clearancing and consequently the delaying of onset or progression of the disease. However, as the response due to this modulation seems to be time-dependent, finding the right regulation of autophagy may be a potential target for drug development for neurodegenerative diseases. In this way, this review focuses on the role of insulin signaling/resistance and autophagy in some neurodegenerative diseases, discussing pharmacological and non-pharmacological interventions in these diseases.

Dietary Restriction and Neuroinflammation: A Potential Mechanistic Link

Chronic neuroinflammation is a common feature of the aged brain, and its association with the major neurodegenerative changes involved in cognitive impairment and motor dysfunction is well established. One of the most potent antiaging interventions tested so far is dietary restriction (DR), which extends the lifespan in various organisms. Microglia and astrocytes are two major types of glial cells involved in the regulation of neuroinflammation. Accumulating evidence suggests that the age-related proinflammatory activation of astrocytes and microglia is attenuated under DR. However, the molecular mechanisms underlying DR-mediated regulation of neuroinflammation are not well understood. Here, we review the current understanding of the effects of DR on neuroinflammation and suggest an underlying mechanistic link between DR and neuroinflammation that may provide novel insights into the role of DR in aging and age-associated brain disorders.

Swim Training Modulates Mouse Skeletal Muscle Energy Metabolism and Ameliorates Reduction in Grip Strength in a Mouse Model of Amyotrophic Lateral Sclerosis

Metabolic reprogramming in skeletal muscles in the human and animal models of amyotrophic lateral sclerosis (ALS) may be an important factor in the diseases progression. We hypothesized that swim training, a modulator of cellular metabolism via changes in muscle bioenergetics and oxidative stress, ameliorates the reduction in muscle strength in ALS mice. In this study, we used transgenic male mice with the G93A human SOD1 mutation B6SJL-Tg (SOD1^G93A) 1Gur/J and wild type B6SJL (WT) mice. Mice were subjected to a grip strength test and isolated skeletal muscle mitochondria were used to perform high-resolution respirometry. Moreover, the activities of enzymes involved in the oxidative energy metabolism and total sulfhydryl groups (as an oxidative stress marker) were evaluated in skeletal muscle. ALS reduces muscle strength (-70% between 11 and 15 weeks, p < 0.05), modulates muscle metabolism through lowering citrate synthase (CS) (-30% vs. WT, p = 0.0007) and increasing cytochrome c oxidase and malate dehydrogenase activities, and elevates oxidative stress markers in skeletal muscle. Swim training slows the reduction in muscle strength (-5% between 11 and 15 weeks) and increases CS activity (+26% vs. ALS I, p = 0.0048). Our findings indicate that swim training is a modulator of skeletal muscle energy metabolism with concomitant improvement of skeletal muscle function in ALS mice.

Disease-modifying effects of metabolic perturbations in ALS/FTLD

Amyotrophic lateral sclerosis (ALS) and frontotemporal lobar degeneration (FTLD) are two fatal neurodegenerative disorders with considerable clinical, pathological and genetic overlap. Both disorders are characterized by the accumulation of pathological protein aggregates that contain a number of proteins, most notably TAR DNA binding protein 43 kDa (TDP-43). Surprisingly, recent clinical studies suggest that dyslipidemia, high body mass index, and type 2 diabetes mellitus are associated with better clinical outcomes in ALS. Moreover, ALS and FTLD patients have a significantly lower incidence of cardiovascular disease, supporting the idea that an unfavorable metabolic profile may be beneficial in ALS and FTLD. The two most widely studied ALS/FTLD models, super-oxide dismutase 1 (SOD1) and TAR DNA binding protein of 43 kDA (TDP-43), reveal metabolic dysfunction and a positive effect of metabolic strategies on disease onset and/or progression. In addition, molecular studies reveal a role for ALS/FTLD-associated proteins in the regulation of cellular and whole-body metabolism. Here, we systematically evaluate these observations and discuss how changes in cellular glucose/lipid metabolism may result in abnormal protein aggregations in ALS and FTLD, which may have important implications for new treatment strategies for ALS/FTLD and possibly other neurodegenerative conditions.

Energy metabolism in ALS: an underappreciated opportunity?

Amyotrophic lateral sclerosis (ALS) is a relentlessly progressive and fatal neurodegenerative disorder that primarily affects motor neurons. Despite our increased understanding of the genetic factors contributing to ALS, no effective treatment is available. A growing body of evidence shows disturbances in energy metabolism in ALS. Moreover, the remarkable vulnerability of motor neurons to ATP depletion has become increasingly clear. Here, we review metabolic alterations present in ALS patients and models, discuss the selective vulnerability of motor neurons to energetic stress, and provide an overview of tested and emerging metabolic approaches to treat ALS. We believe that a further understanding of the metabolic biology of ALS can lead to the identification of novel therapeutic targets.

Protein aggregation activates erratic stress response in dietary restricted yeast cells

Chronic stress and prolonged activation of defence pathways have deleterious consequences for the cell. Dietary restriction is believed to be beneficial as it induces the cellular stress response machinery. We report here that although the phenomenon is beneficial in a wild-type cell, dietary restriction leads to an inconsistent response in a cell that is already under proteotoxicity-induced stress. Using a yeast model of Huntington's disease, we show that contrary to expectation, aggregation of mutant huntingtin is exacerbated and activation of the unfolded protein response pathway is dampened under dietary restriction. Global proteomic analysis shows that when exposed to a single stress, either protein aggregation or dietary restriction, the expression of foldases like peptidyl-prolyl isomerase, is strongly upregulated. However, under combinatorial stress, this lead is lost, which results in enhanced protein aggregation and reduced cell survival. Successful designing of aggregation-targeted therapeutics will need to take additional stressors into account.

Multi-target detection of oxidative stress biomarkers in quercetin and myricetin treated human red blood cells

Quercetin and myricetin help against oxidative stress in human red blood cells during aging, thereby has tremendous scope in medical diagnostics and therapeutics.

Mechanisms of Muscle Denervation in Aging: Insights from a Mouse Model of Amyotrophic Lateral Sclerosis

Muscle denervation at the neuromuscular junction (NMJ) is thought to be a contributing factor in age-related muscle weakness. Therefore, understanding the mechanisms that modulate NMJ innervation is a key to developing therapies to combat age-related muscle weakness affecting the elderly. Two mouse models, one lacking the Cu/Zn superoxide dismutase (SOD1) gene and another harboring the transgenic mutant human SOD1 gene, display progressive changes at the NMJ, including muscle endplate fragmentation, nerve terminal sprouting, and denervation. These changes at the NMJ share many of the common features observed in the NMJs of aged mice. In this review, research findings demonstrating the effects of PGC-1α, IGF-1, GDNF, MyoD, myogenin, and miR-206 on NMJ innervation patterns in the G93A SOD1 mice will be highlighted in the context of age-related muscle denervation.

AMPK Signalling and Defective Energy Metabolism in Amyotrophic Lateral Sclerosis

Amyotrophic lateral sclerosis (ALS) is caused by selective loss of upper and lower motor neurons by complex mechanisms that are incompletely understood. Motor neurons are large, highly polarised and excitable cells with unusually high energetic demands to maintain resting membrane potential and propagate action potentials. This leads to higher ATP consumption and mitochondrial metabolism in motor neurons relative to other cells. Here, we review increasing evidence that defective energy metabolism and homeostasis contributes to selective vulnerability and degeneration of motor neurons in ALS. Firstly, we provide a brief overview of major energetic pathways in the CNS, including glycolysis, oxidative phosphorylation and the AMP-activated protein kinase (AMPK) signalling pathway, while highlighting critical metabolic interactions between neurons and astrocytes. Next, we review evidence from ALS patients and transgenic mutant SOD1 mice for weight loss, hypermetabolism, hyperlipidemia and mitochondrial dysfunction in disease onset and progression. Genetic and therapeutic modifiers of energy metabolism in mutant SOD1 mice will also be summarised. We also present evidence that additional ALS-linked proteins, TDP-43 and FUS, lead to energy disruption and mitochondrial defects in motor neurons. Lastly, we review emerging evidence including our own that dysregulation of the AMPK signalling cascade in motor neurons is an early and common event in ALS pathogenesis. We suggest that an imbalance in energy metabolism should be considered an important factor in both progression and potential treatment of ALS.

Effects of diet on adenosine monophosphate-activated protein kinase activity and disease progression in an amyotrophic lateral sclerosis model

OBJECTIVES

To study the effects of diet on disease progression and activity levels of adenosine monophosphate-activated protein kinase (AMPK), and its downstream targets, in an amyotrophic lateral sclerosis (ALS) animal model.

METHODS

AMPK activity was measured in cerebral cortex, spinal cord, cerebellum and hindlimb muscle tissue using immunohistochemistry in transgenic mice overexpressing human superoxide dismutase-1 (SOD1(G93A)) fed a high-fat (HFD), standard ad libitum (AL) or calorie-restricted (CR) diet; AMPK activity was also measured in wild-type (SOD1(WT)) mice. Activity of AMPK and phospho-AMPK, acetyl coenzyme-A carboxylase (ACC), phospho-ACC and heat shock protein-70 (Hsp70) were also measured using Western blot. Food intake and grip strength were recorded; body composition was analysed using dual energy X-ray absorptiometry. Motor neuron survival was observed using Nissl staining.

RESULTS

AMPK activity increased and Hsp70 expression decreased in AL SOD1(G93A) mice compared with SOD1(WT) mice in spinal cord and hindlimb muscle. Compared with AL SOD1(G93A) mice, CR SOD1(G93A) mice showed increased AMPK activity, downregulated Hsp70 expression, reduced motor neuron survival in spinal cord and hindlimb muscle and reduced lifespan; HFD SOD1(G93A) mice showed opposite effects.

CONCLUSIONS

In this mouse model, increased AMPK activity seems to play a negative role in motor neuron survival, possibly through a novel mechanism involving Hsp70 downregulation. These changes can be modified by diet. Inhibition of AMPK may provide a therapeutic strategy for ALS.

"Preconditioning" with latrepirdine, an adenosine 5'-monophosphate-activated protein kinase activator, delays amyotrophic lateral sclerosis progression in SOD1(G93A) mice

Adenosine 5'-monophosphate-activated protein kinase (AMPK) is a master regulator of energy balance. As energy imbalance is documented as a key pathologic feature of amyotrophic lateral sclerosis (ALS), we investigated AMPK as a pharmacologic target in SOD1(G93A) mice. We noted a strong activation of AMPK in lumbar spinal cords of SOD1(G93A) mice. Pharmacologic activation of AMPK has shown protective effects in neuronal "preconditioning" models. We tested the hypothesis that "preconditioning" with a small molecule activator of AMPK, latrepirdine, exerts beneficial effects on disease progression. SOD1(G93A) mice (n = 24 animals per group; sex and litter matched) were treated with latrepirdine (1 μg/kg, intraperitoneal) or vehicle from postnatal day 70 to 120. Treatment with latrepirdine increased AMPK activity in primary mouse motor neuron cultures and in SOD1(G93A) lumbar spinal cords. Mice "preconditioned" with latrepirdine showed a delayed symptom onset and a significant increase in life span (p < 0.01). Our study suggests that "preconditioning" with latrepirdine may represent a possible therapeutic strategy for individuals harboring ALS-associated gene mutations who are at risk for developing ALS.

Neuronal cells but not muscle cells are resistant to oxidative stress mediated protein misfolding and cell death: role of molecular chaperones

Our recent study in a mouse model of familial-Amyotrophic Lateral Sclerosis (f-ALS) revealed that muscle proteins are equally sensitive to misfolding as spinal cord proteins despite the presence of low mutant CuZn-superoxide dismutase, which is considered to be the key toxic element for initiation and progression of f-ALS. More importantly, we observed differential level of heat shock proteins (Hsp's) between skeletal muscle and spinal cord tissues prior to the onset and during disease progression; spinal cord maintains significantly higher level of Hsp's compared to skeletal muscle. In this study, we report two important observations; (i) muscle cells (but not neuronal cells) are extremely vulnerable to protein misfolding and cell death during challenge with oxidative stress and (ii) muscle cells fail to mount Hsp's during challenge unlike neuronal cells. These two findings can possibly explain why muscle atrophy precedes the death of motor neurons in f-ALS mice.

Mutant TDP-43 deregulates AMPK activation by PP2A in ALS models

Bioenergetic abnormalities and metabolic dysfunction occur in amyotrophic lateral sclerosis (ALS) patients and genetic mouse models. However, whether metabolic dysfunction occurs early in ALS pathophysiology linked to different ALS genes remains unclear. Here, we investigated AMP-activated protein kinase (AMPK) activation, which is a key enzyme induced by energy depletion and metabolic stress, in neuronal cells and mouse models expressing mutant superoxide dismutase 1 (SOD1) or TAR DNA binding protein 43 (TDP-43) linked to ALS. AMPK phosphorylation was sharply increased in spinal cords of transgenic SOD1^G93A mice at disease onset and accumulated in cytoplasmic granules in motor neurons, but not in pre-symptomatic mice. AMPK phosphorylation also occurred in peripheral tissues, liver and kidney, in SOD1^G93A mice at disease onset, demonstrating that AMPK activation occurs late and is not restricted to motor neurons. Conversely, AMPK activity was drastically diminished in spinal cords and brains of presymptomatic and symptomatic transgenic TDP-43^A315T mice and motor neuronal cells expressing different TDP-43 mutants. We show that mutant TDP-43 induction of the AMPK phosphatase, protein phosphatase 2A (PP2A), is associated with AMPK inactivation in these ALS models. Furthermore, PP2A inhibition by okadaic acid reversed AMPK inactivation by mutant TDP-43 in neuronal cells. Our results suggest that mutant SOD1 and TDP-43 exert contrasting effects on AMPK activation which may reflect key differences in energy metabolism and neurodegeneration in spinal cords of SOD1^G93A and TDP-43^A315T mice. While AMPK activation in motor neurons correlates with progression in mutant SOD1-mediated disease, AMPK inactivation mediated by PP2A is associated with mutant TDP-43-linked ALS.

A plural role for lipids in motor neuron diseases: energy, signaling and structure

Motor neuron diseases (MNDs) are characterized by selective death of motor neurons and include mainly adult-onset amyotrophic lateral sclerosis (ALS) and spinal muscular atrophy (SMA). Neurodegeneration is not the single pathogenic event occurring during disease progression. There are multiple lines of evidence for the existence of defects in lipid metabolism at peripheral level. For instance, hypermetabolism is well characterized in ALS, and dyslipidemia correlates with better prognosis in patients. Lipid metabolism plays also a role in other MNDs. In SMA, misuse of lipids as energetic nutrients is described in patients and in related animal models. The composition of structural lipids in the central nervous system is modified, with repercussion on membrane fluidity and on cell signaling mediated by bioactive lipids. Here, we review the main epidemiologic and mechanistic findings that link alterations of lipid metabolism and motor neuron degeneration, and we discuss the rationale of targeting these modifications for therapeutic management of MNDs.

The fine line between lifespan extension and shortening in response to caloric restriction

Caloric restriction (CR) is generally linked to lifespan extension in various organisms and may limit age-associated diseases. Processes through which caloric restriction promotes lifespan include obesity-countering weight loss, increased DNA repair, control of ribosomal and telomeric DNA repeats, mitochondrial regulation, activation of antioxidants, and protective autophagy. Several of these protective cellular processes are linked to the suppression of TOR (target of rapamycin) or the activation of sirtuins. In stark contrast, CR fails to extend or even shortens lifespan in certain settings. CR-dependent lifespan shortening is linked to weight loss in the non-obese, mitochondrial hyperactivity, genomic inflexibility, and several other processes. Deciphering the balance between positive and negative effects of CR is critical to understanding its ultimate impact on aging. This knowledge is especially needed in order to fulfil the promise of using CR or its mimetic drugs to counteract age-associated diseases and unhealthy aging.

Dietary restriction in cerebral bioenergetics and redox state

The brain has a central role in the regulation of energy stability of the organism. It is the organ with the highest energetic demands, the most susceptible to energy deficits, and is responsible for coordinating behavioral and physiological responses related to food foraging and intake. Dietary interventions have been shown to be a very effective means to extend lifespan and delay the appearance of age-related pathological conditions, notably those associated with brain functional decline. The present review focuses on the effects of these interventions on brain metabolism and cerebral redox state, and summarizes the current literature dealing with dietary interventions on brain pathology.

Superoxide dismutase 1 mutation in a cellular model of amyotrophic lateral sclerosis shifts energy generation from oxidative phosphorylation to glycolysis

Amyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative disorder involving the progressive degeneration of motor neurons in the brain and spinal cord. Mitochondrial dysfunction plays a key role in ALS disease progression and has been observed in several ALS cellular and animal models. Here, we show that fibroblasts isolated from ALS cases with a Cu/Zn superoxide dismutase (SOD1) I113T mutation recapitulate these mitochondrial defects. Using a novel technique, which measures mitochondrial respiration and glycolytic flux simultaneously in living cells, we have shown that SOD1 mutation causes a reduction in mitochondrial respiration and an increase in glycolytic flux. This causes a reduction in adenosine triphosphate produced by oxidative phosphorylation and an increase in adenosine triphosphate produced by glycolysis. Switching the energy source from glucose to galactose caused uncoupling of mitochondria with increased proton leak in SOD1(I113T) fibroblasts. Assessment of the contribution of fatty acid oxidation to total respiration, suggested that fatty acid oxidation is reduced in SOD1 ALS fibroblasts, an effect which can be mimicked by starving the control cells of glucose. These results highlight the importance of understanding the interplay between the major metabolic pathways, which has the potential to lead to strategies to correct the metabolic dysregulation observed in ALS cases.

Molecular mechanisms underlying genotype-dependent responses to dietary restriction

Dietary restriction (DR) increases lifespan and attenuates age-related phenotypes in many organisms; however, the effect of DR on longevity of individuals in genetically heterogeneous populations is not well characterized. Here, we describe a large-scale effort to define molecular mechanisms that underlie genotype-specific responses to DR. The effect of DR on lifespan was determined for 166 single gene deletion strains in Saccharomyces cerevisiae. Resulting changes in mean lifespan ranged from a reduction of 79% to an increase of 103%. Vacuolar pH homeostasis, superoxide dismutase activity, and mitochondrial proteostasis were found to be strong determinants of the response to DR. Proteomic analysis of cells deficient in prohibitins revealed induction of a mitochondrial unfolded protein response (mtUPR), which has not previously been described in yeast. Mitochondrial proteotoxic stress in prohibitin mutants was suppressed by DR via reduced cytoplasmic mRNA translation. A similar relationship between prohibitins, the mtUPR, and longevity was also observed in Caenorhabditis elegans. These observations define conserved molecular processes that underlie genotype-dependent effects of DR that may be important modulators of DR in higher organisms.

Beneficial effects of a 6-month dietary restriction are time-dependently abolished within 2 weeks or 6 months of refeeding-genome-wide transcriptome analysis in mouse liver

Dietary restriction (DR) has been shown to exert a number of beneficial effects including the prolongation of life span. One of the mechanisms by which DR leads to these advantages seems to be the induction of endogenous antioxidant defense and stress response mechanisms. However, little is known about the persistence of DR benefits after return to an ad libitum diet. In this study, male C57BL/6 mice were fed 75% of a normal diet for 6 months (DR) followed by 6 months of ad libitum refeeding (RF) and compared to a continuously ad libitum fed control group. To study the impact of DR and RF on the liver transcriptome, a global gene expression profile was generated using microarray technology. In comparison, the DR group showed lower body weight, lower triglyceride and cholesterol levels, reduced lipid peroxidation, and a changed hepatic fatty acid pattern. mRNA transcription and activity of antioxidant and phase II enzymes, as well as metallothionein 1 gene expression, were increased and autophagy was induced. Shifting from long-term DR to RF abolished 96% of the DR-mediated changes in differential gene expression within 2 weeks, and after 6 months of refeeding all of the previously differentially expressed genes were similar in both groups. These results indicate that DR has to be maintained continuously to keep its beneficial effects.

Aging decreases antioxidant effects and increases lipid peroxidation in the Apolipoprotein E deficient mouse

In this study, to study the effect of aging and Apolipoprotein E (ApoE) deficiency on antioxidant ability in mice, we examined whether lipid peroxidation is promoted by aging in ApoE deficient (ApoE(-/-)) mice, which have a shorter lifespan than normal mice. The levels of thiobarbituric acid-reactive substances (TBARS), a biomarker of lipid peroxidation, were measured in plasma and liver in ApoE(-/-) mice aged 12 weeks (young) and 52 weeks (early stage of senescence). TBARS in plasma and liver were significantly increased by aging. Next, we examined the reasons why lipid peroxidation was promoted by aging, based on measurement of protein and mRNA levels for antioxidant enzymes (superoxide dismutase, catalase, and glutathione peroxidase) in liver in ApoE(-/-) mice aged 12 and 52 weeks. The levels of superoxide dismutase 1 and 2 in liver were significantly decreased by aging. The mRNA level of catalase was also significantly decreased and the mRNA levels of superoxide dismutase 1, superoxide dismutase 2 and glutathione peroxidase 1 all showed a tendency to decrease with age. These results suggest that lipid peroxidation is caused by reduction of antioxidant activity with aging and that this promotes senescence and shortens lifespan in ApoE(-/-) mice.

The omega-3 fatty acid eicosapentaenoic acid accelerates disease progression in a model of amyotrophic lateral sclerosis

Amyotrophic lateral sclerosis (ALS) is a progressive fatal neurodegenerative disease characterised by loss of motor neurons that currently has no cure. Omega-3 polyunsaturated fatty acids, such as eicosapentaenoic acid (EPA), have many health benefits including neuroprotective and myoprotective potential. We tested the hypothesis that a high level of dietary EPA could exert beneficial effects in ALS. The dietary exposure to EPA (300 mg/kg/day) in a well-established mouse model of ALS expressing the G93A superoxide dismutase 1 (SOD1) mutation was initiated at a pre-symptomatic or symptomatic stage, and the disease progression was monitored until the end stage. Daily dietary EPA exposure initiated at the disease onset did not significantly alter disease presentation and progression. In contrast, EPA treatment initiated at the pre-symptomatic stage induced a significantly shorter lifespan. In a separate group of animals sacrificed before the end stage, the tissue analysis showed that the vacuolisation detected in G93A-SOD1 mice was significantly increased by exposure to EPA. Although EPA did not alter motor neurone loss, EPA reversed the significant increase in activated microglia and the astrocytic activation seen in G93A-SOD1 mice. The microglia in the spinal cord of G93A-SOD1 mice treated with EPA showed a significant increase in 4-hydroxy-2-hexenal, a highly toxic aldehydic oxidation product of omega-3 fatty acids. These data show that dietary EPA supplementation in ALS has the potential to worsen the condition and accelerate the disease progression. This suggests that great caution should be exerted when considering dietary omega-3 fatty acid supplements in ALS patients.

Evaluation of longevity enhancing compounds against transactive response DNA-binding protein-43 neuronal toxicity

In simple systems, lifespan can be extended by various methods including dietary restriction, mutations in the insulin/insulin-like growth factor (IGF) pathway or mitochondria among other processes. It is widely held that the mechanisms that extend lifespan may be adapted for diminishing age-associated pathologies. We tested whether a number of compounds reported to extend lifespan in C. elegans could reduce age-dependent toxicity caused by mutant TAR DNA-binding protein-43 in C. elegans motor neurons. Only half of the compounds tested show protective properties against neurodegeneration, suggesting that extended lifespan is not a strong predictor for neuroprotective properties. We report here that resveratrol, rolipram, reserpine, trolox, propyl gallate, and ethosuximide protect against mutant TAR DNA-binding protein-43 neuronal toxicity. Finally, of all the compounds tested, only resveratrol required daf-16 and sir-2.1 for protection, and ethosuximide showed dependence on daf-16 for its activity.

Pathogenic VCP mutations induce mitochondrial uncoupling and reduced ATP levels

Valosin-containing protein (VCP) is a highly expressed member of the type II AAA+ ATPase family. VCP mutations are the cause of inclusion body myopathy, Paget's disease of the bone, and frontotemporal dementia (IBMPFD) and they account for 1%-2% of familial amyotrophic lateral sclerosis (ALS). Using fibroblasts from patients carrying three independent pathogenic mutations in the VCP gene, we show that VCP deficiency causes profound mitochondrial uncoupling leading to decreased mitochondrial membrane potential and increased mitochondrial oxygen consumption. This mitochondrial uncoupling results in a significant reduction of cellular ATP production. Decreased ATP levels in VCP-deficient cells lower their energy capacity, making them more vulnerable to high energy-demanding processes such as ischemia. Our findings propose a mechanism by which pathogenic VCP mutations lead to cell death.

Aging decreases antioxidant effects and increases lipid peroxidation in the Apolipoprotein E deficient mouse

In this study, to study the effect of aging and Apolipoprotein E (ApoE) deficiency on antioxidant ability in mice, we examined whether lipid peroxidation is promoted by aging in ApoE deficient (ApoE^−/−) mice, which have a shorter lifespan than normal mice. The levels of thiobarbituric acid-reactive substances (TBARS), a biomarker of lipid peroxidation, were measured in plasma and liver in ApoE^−/− mice aged 12 weeks (young) and 52 weeks (early stage of senescence). TBARS in plasma and liver were significantly increased by aging. Next, we examined the reasons why lipid peroxidation was promoted by aging, based on measurement of protein and mRNA levels for antioxidant enzymes (superoxide dismutase, catalase, and glutathione peroxidase) in liver in ApoE^−/− mice aged 12 and 52 weeks. The levels of superoxide dismutase 1 and 2 in liver were significantly decreased by aging. The mRNA level of catalase was also significantly decreased and the mRNA levels of superoxide dismutase 1, superoxide dismutase 2 and glutathione peroxidase 1 all showed a tendency to decrease with age. These results suggest that lipid peroxidation is caused by reduction of antioxidant activity with aging and that this promotes senescence and shortens lifespan in ApoE^−/− mice.

Vitamin D(3) at 50x AI attenuates the decline in paw grip endurance, but not disease outcomes, in the G93A mouse model of ALS, and is toxic in females

BACKGROUND

We previously demonstrated that dietary vitamin D(3) at 10x the adequate intake (AI) attenuates the decline in functional capacity in the G93A mouse model of ALS. We hypothesized that higher doses would elicit more robust changes in functional and disease outcomes.

OBJECTIVE

To determine the effects of dietary vitamin D(3) at 50xAI on functional outcomes (motor performance, paw grip endurance) and disease severity (clinical score), as well as disease onset, disease progression and lifespan in the transgenic G93A mouse model of ALS.

METHODS

Starting at age 25 d, 100 G93A mice (55 M, 45 F) were provided ad libitum with either an adequate (AI; 1 IU D(3)/g feed) or high (HiD; 50 IU D(3)/g feed) vitamin D(3) diet.

RESULTS

HiD females consumed 9% less food corrected for body weight vs. AI females (P = 0.010). HiD mice had a 12% greater paw grip endurance over time between age 60-141 d (P = 0.015), and a 37% greater score during disease progression (P = 0.042) vs. AI mice. Although HiD females had a non-significant 31% greater CS prior to disease onset vs. AI females, they exhibited a significant 20% greater paw grip endurance AUC (P = 0.020) when corrected for clinical score.

CONCLUSION

Dietary D(3) supplementation at 50x the adequate intake attenuated the decline in paw grip endurance, but did not influence age at disease onset, hindlimb paralysis or endpoint in the transgenic G93A mouse model of ALS. Furthermore, females may have reached the threshold for vitamin D(3) toxicity as evidence by reduced food intake and greater disease severity prior to disease onset.

Glucose delays age-dependent proteotoxicity

Nutrient availability influences an organism’s life history with profound effects on metabolism and lifespan. The association between a healthy lifespan and metabolism is incompletely understood, but a central factor is glucose metabolism. Although glucose is an important cellular energy source, glucose restriction is associated with extended lifespan in simple animals and a reduced incidence of age-dependent pathologies in humans. We report here that glucose enrichment delays mutant polyglutamine, TDP-43, FUS, and amyloid-β toxicity in Caenorhabditis elegans models of neurodegeneration by reducing protein misfolding. Dysregulated metabolism is common to neurodegeneration and we show that glucose enrichment is broadly protective against proteotoxicity.

Dietary vitamin D3 supplementation at 10× the adequate intake improves functional capacity in the G93A transgenic mouse model of ALS, a pilot study

BACKGROUND

Vitamin D has antioxidant, anti-inflammatory, and neuroprotective properties, and may mitigate amyotrophic lateral sclerosis (ALS) pathology.

AIMS

To determine the effects of dietary vitamin D(3) (D(3)) at 10-fold the adequate intake (AI) on functional and disease outcomes and lifespan in the transgenic G93A mouse model of ALS.

METHODS

Starting at age 40 days, 32 G93A mice (21 M, 11 F) were provided ad libitum with either an adequate (AI; 1 IU/g feed) or high (HiD; 10 IU/g feed) D(3) diet. Differences were considered significant at P≤ 0.10, as this was a pilot study.

RESULTS

For paw grip endurance, HiD mice had a 7% greater score between 60-133 d versus AI mice (P= 0.074). For motor performance, HiD mice had a 22% greater score between 60-133 days (P= 0.074) versus AI mice due to changes observed in male mice, where HiD males had a 33% greater score (P= 0.064) versus AI males. There were no significant diet differences in disease onset, disease progression, or lifespan.

CONCLUSION

Although disease outcomes were not affected, D(3) supplementation at 10-fold the AI improved paw grip endurance and motor performance in the transgenic G93A mouse model of ALS, specifically in males.

Reduced activity of AMP-activated protein kinase protects against genetic models of motor neuron disease

A growing body of research indicates that amyotrophic lateral sclerosis (ALS) patients and mouse models of ALS exhibit metabolic dysfunction. A subpopulation of ALS patients possesses higher levels of resting energy expenditure and lower fat-free mass compared to healthy controls. Similarly, two mutant copper zinc superoxide dismutase 1 (mSOD1) mouse models of familial ALS possess a hypermetabolic phenotype. The pathophysiological relevance of the bioenergetic defects observed in ALS remains largely elusive. AMP-activated protein kinase (AMPK) is a key sensor of cellular energy status and thus might be activated in various models of ALS. Here, we report that AMPK activity is increased in spinal cord cultures expressing mSOD1, as well as in spinal cord lysates from mSOD1 mice. Reducing AMPK activity either pharmacologically or genetically prevents mSOD1-induced motor neuron death in vitro. To investigate the role of AMPK in vivo, we used Caenorhabditis elegans models of motor neuron disease. C. elegans engineered to express human mSOD1 (G85R) in neurons develops locomotor dysfunction and severe fecundity defects when compared to transgenic worms expressing human wild-type SOD1. Genetic reduction of aak-2, the ortholog of the AMPK α2 catalytic subunit in nematodes, improved locomotor behavior and fecundity in G85R animals. Similar observations were made with nematodes engineered to express mutant tat-activating regulatory (TAR) DNA-binding protein of 43 kDa molecular weight. Altogether, these data suggest that bioenergetic abnormalities are likely to be pathophysiologically relevant to motor neuron disease.

Vitamin D3 deficiency differentially affects functional and disease outcomes in the G93A mouse model of amyotrophic lateral sclerosis

Amyotrophic lateral sclerosis (ALS) is a neuromuscular disease characterized by motor neuron death in the central nervous system. Vitamin D supplementation increases antioxidant activity, reduces inflammation and improves motor neuron survival. We have previously demonstrated that vitamin D(3) supplementation at 10× the adequate intake improves functional outcomes in a mouse model of ALS.

OBJECTIVE

To determine whether vitamin D deficiency influences functional and disease outcomes in a mouse model of ALS.

METHODS

At age 25 d, 102 G93A mice (56 M, 46 F) were divided into two vitamin D(3) groups: 1) adequate (AI; 1 IU D(3)/g feed) and 2) deficient (DEF; 0.025 IU D(3)/g feed). At age 113 d, tibialis anterior (TA), quadriceps (quads) and brain were harvested from 42 mice (22 M and 20 F), whereas the remaining 60 mice (34 M and 26 F) were followed to endpoint.

RESULTS

During disease progression, DEF mice had 25% (P=0.022) lower paw grip endurance AUC and 19% (P=0.017) lower motor performance AUC vs. AI mice. Prior to disease onset (CS 2), DEF mice had 36% (P=0.016) lower clinical score (CS) vs. AI mice. DEF mice reached CS 2 six days later vs. AI mice (P=0.004), confirmed by a logrank test which revealed that DEF mice reached CS 2 at a 43% slower rate vs. AI mice (HR= .57; 95% CI: 0.38, 1.74; P=0.002). Body weight-adjusted TA (AI: r=0.662, P=0.001; DEF: r=0.622, P=0.006) and quads (AI: r=0.661, P=0.001; DEF: r=0.768; P<0.001) weights were strongly correlated with age at CS 2.

CONCLUSION

Vitamin D(3) deficiency improves early disease severity and delays disease onset, but reduces performance in functional outcomes following disease onset, in the high-copy G93A mouse.

Biochemical and anthropometric effects of a weight loss dietary supplement in healthy men and women

Background:

We have recently noted an acute increase in circulating free fatty acids and glycerol, as well as resting metabolic rate, when men and women ingested the dietary supplement OxyELITE Pro™ in a single dose. We have also noted a reduction in appetite when subjects were treated with this supplement for 14 consecutive days. It is possible that such findings may favor body weight and fat loss over time. Therefore, the purpose of the present study was to determine the effects of this dietary supplement on weight loss and associated markers using an eight week intervention.

Methods:

Exercise-trained subjects were randomly assigned in double blind manner to ingest either the dietary supplement (n = 16; aged 22.8 ± 0.7) or a placebo (n = 16; 22.5 ± 0.5) every day for eight weeks. Body weight, body composition, skinfold thickness, serum lipids, and appetite were measured as the primary outcome variables. As measures of supplement safety, a complete blood count and comprehensive metabolic panel were performed, and resting heart rate and blood pressure were measured (pre and post intervention).

Results:

No interactions or main effects were noted for our primary outcome measures (P > 0.05). However, when comparing pre and post intervention values for the supplement, significant decreases were noted in appetite, body weight, body fat percentage, and skinfold thickness (P < 0.05), while increases were noted for total and HDL-C, as well as for resting heart rate (P < 0.05). No changes were noted for placebo from pre to post intervention (P > 0.05), with the exception of an increase in HDL-C (P < 0.05). Blood pressure and bloodborne safety variables were not differently impacted by supplement or placebo (P > 0.05), with the exception of monocytes, for which an interaction effect was noted (P = 0.04).

Conclusion:

These data indicate that the dietary supplement OxyELITE Pro™ may assist in weight and body fat loss in a sample of exercise-trained men and women. The supplement does not result in any adverse effects pertaining to resting blood pressure or bloodborne markers of safety; however a small increase in resting heart rate is observed.

Dysregulation of astrocyte-motoneuron cross-talk in mutant superoxide dismutase 1-related amyotrophic lateral sclerosis

Amyotrophic lateral sclerosis is a neurodegenerative disease in which death of motoneurons leads to progressive failure of the neuromuscular system resulting in death frequently within 2-3 years of symptom onset. Focal onset and propagation of the disease symptoms to contiguous motoneuron groups is a striking feature of the human disease progression. Recent work, using mutant superoxide dismutase 1 murine models and in vitro culture systems has indicated that astrocytes are likely to contribute to the propagation of motoneuron injury and disease progression. However, the basis of this astrocyte toxicity and/or failure of motoneuron support has remained uncertain. Using a combination of in vivo and in vitro model systems of superoxide dismutase 1-related amyotrophic lateral sclerosis, linked back to human biosamples, we set out to elucidate how astrocyte properties change in the presence of mutant superoxide dismutase 1 to contribute to motoneuron injury. Gene expression profiling of spinal cord astrocytes from presymptomatic transgenic mice expressing mutant superoxide dismutase 1 revealed two striking changes. First, there was evidence of metabolic dysregulation and, in particular, impairment of the astrocyte lactate efflux transporter, with resultant decrease of spinal cord lactate levels. Second, there was evidence of increased nerve growth factor production and dysregulation of the ratio of pro-nerve growth factor to mature nerve growth factor, favouring p75 receptor expression and activation by neighbouring motoneurons. Functional in vitro studies showed that astrocytes expressing mutant superoxide dismutase 1 are toxic to normal motoneurons. We provide evidence that reduced metabolic support from lactate release and activation of pro-nerve growth factor-p75 receptor signalling are key components of this toxicity. Preservation of motoneuron viability could be achieved by increasing lactate provision to motoneurons, depletion of increased pro-nerve growth factor levels or p75 receptor blockade. These findings are likely to be relevant to human amyotrophic lateral sclerosis, where we have demonstrated increased levels of pro-nerve growth factor in cerebrospinal fluid and increased expression of the p75 receptor by spinal motoneurons. Taken together, these data confirm that altered properties of astrocytes are likely to play a crucial role in the propagation of motoneuron injury in superoxide dismutase 1-related amyotrophic lateral sclerosis and indicate that manipulation of the energy supply to motoneurons as well as inhibition of p75 receptor signalling may represent valuable neuroprotective strategies.