Evidence for defective energy homeostasis in amyotrophic lateral sclerosis: benefit of a high-energy diet in a transgenic mouse model

Ablation of Sim1 neurons causes obesity through hyperphagia and reduced energy expenditure

Single-minded 1 (Sim1) is a transcription factor necessary for development of the paraventricular nucleus of the hypothalamus (PVH). This nucleus is a critical regulator of appetite, energy expenditure and body weight. Previously we showed that Sim1^+/− mice and conditional postnatal Sim1^−/− mice exhibit hyperphagia, obesity, increased linear growth and susceptibility to diet-induced obesity, but no decrease in energy expenditure. Bilateral ablation of the PVH causes obesity due to hyperphagia and reduced energy expenditure. It remains unknown whether Sim1 neurons regulate energy expenditure. In this study, Sim1cre mice were bred to homozygous inducible diphtheria toxin receptor (iDTR) mice to generate mice expressing the simian DTR in Sim1 cells. In these mice, Sim1 neuron ablation was performed by intracerebroventricular (ICV) injection of diphtheria toxin. Compared to controls, mice with Sim1 neuron ablation became obese (with increased fat mass) on a chow diet due to increased food intake and reduced energy expenditure. In post-injection mice, we observed a strong inverse correlation between the degree of obesity and hypothalamic Sim1 expression. The reduction in baseline energy expenditure observed in these mice was accompanied by a reduction in activity. This reduction in activity did not fully account for the reduced energy expenditure as these mice exhibited decreased resting energy expenditure, decreased body temperature, decreased brown adipose tissue temperature, and decreased UCP1 expression suggesting an impairment of thermogenesis. In injected mice, hypothalamic gene expression of Sim1, oxytocin (OXT) and thyrotropin releasing hormone (TRH) was reduced by about 50%. These results demonstrate that Sim1 neurons in adult mice regulate both food intake and energy expenditure. Based on the body of work in the field, feeding regulation by Sim1 neurons likely occurs in both the PVH and medial amygdala, in contrast to energy expenditure regulation by Sim1 neurons, which likely is localized to the PVH.

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.

Identifying potential risk factors for developing amyotrophic lateral sclerosis

SUMMARY Amyotrophic lateral sclerosis (ALS) is a neurodegenerative disorder of adult life, characterized by the progressive loss of upper motor neurons in the primary motor cortex and of the spinal and bulbar lower motor neurons. The cause of sporadic cases and of the majority of hereditary cases remains elusive. So far a total of 17 genes or genetic loci of familial ALS have been identified, related to DNA/RNA processing, protein aggregation, membrane trafficking and axonal transport and mitochondrial dysfunction. A large range of environmental factors have also been studied, with inconclusive results, with the possible exception of cigarette smoking. ALS is now considered a complex multifactorial neurodegenerative disorder, but studies analyzing genetic and environmental factors together are still underway.

Biochemical alterations associated with ALS

Our objective was to identify metabolic pathways affected by ALS using non-targeted metabolomics in plasma, comparing samples from healthy volunteers to those from ALS patients. This discovery could become the basis for the identification of therapeutic targets and diagnostic biomarkers of ALS. Two distinct cross-sectional studies were conducted. Plasma was collected from 62 (Study 1) and 99 (Study 2) participants meeting El Escorial criteria for possible, probable, or definite ALS; 69 (Study 1) and 48 (Study 2) healthy controls samples were collected. Global metabolic profiling was used to detect and evaluate biochemical signatures of ALS. Twenty-three metabolites were significantly altered in plasma from ALS patients in both studies. These metabolites include biochemicals in pathways associated with neuronal change, hypermetabolism, oxidative damage, and mitochondrial dysfunction, all of which are proposed disease mechanisms in ALS. The data also suggest possible hepatic dysfunction associated with ALS. In conclusion, the data presented here provide insight into the pathophysiology of ALS while suggesting promising areas of focus for future studies. The metabolomics approach can generate novel hypotheses regarding ALS disease mechanisms with the potential to identify therapeutic targets and novel diagnostic biomarkers.

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.

Disease progression in a mouse model of amyotrophic lateral sclerosis: the influence of chronic stress and corticosterone

Amyotrophic lateral sclerosis (ALS) is a progressive neurodegenerative disease characterized by motor neuron cell loss, muscular atrophy, and a shortened life span. Survival is highly variable, as some patients die within months, while others live for many years. Exposure to stress or the development of a nonoptimal stress response to disease might account for some of this variability. We show in the SOD1(G93A) mouse model of ALS that recurrent exposure to restraint stress led to an earlier onset of astrogliosis and microglial activation within the spinal cord, accelerated muscular weakness, and a significant decrease in median survival (105 vs. 122 d) when compared to nonstressed animals. Moreover, during normal disease course, ALS mice display a cacostatic stress response by developing an aberrant serum corticosterone circadian rhythm. Interestingly, we also found that higher corticosterone levels were significantly correlated with both an earlier onset of paralysis (males: r(2)=0.746; females: r(2)=0.707) and shorter survival times (males: r(2)=0.680; females: r(2)=0.552) in ALS mice. These results suggest that stress is capable of accelerating disease progression and that strategies that modulate glucocorticoid metabolism might be a viable treatment approach for ALS.

Mitochondrial redox signalling by p66Shc mediates ALS-like disease through Rac1 inactivation

Increased oxidative stress and mitochondrial damage are among the mechanisms whereby mutant SOD1 (mutSOD1) associated with familial forms of amyotrophic lateral sclerosis (ALS) induces motoneuronal death. The 66 kDa isoform of the growth factor adapter Shc (p66Shc) is known to be central in the control of mitochondria-dependent oxidative balance. Here we report that expression of mutSOD1s induces the activation of p66Shc in neuronal cells and that the overexpression of inactive p66Shc mutants protects cells from mutSOD1-induced mitochondrial damage. Most importantly, deletion of p66Shc ameliorates mitochondrial function, delays onset, improves motor performance and prolongs survival in transgenic mice modelling ALS. We also show that p66Shc activation by mutSOD1 causes a strong decrease in the activity of the small GTPase Rac1 through a redox-sensitive regulation. Our results provide new insight into the potential mechanisms of mutSOD1-mediated mitochondrial dysfunction.

The in vivo contribution of motor neuron TrkB receptors to mutant SOD1 motor neuron disease

Brain-derived neurotrophic factor (BDNF) and its receptor tropomyosin-related kinase B (TrkB) are widely expressed in the vertebrate nervous system and play a central role in mature neuronal function. In vitro BDNF/TrkB signaling promotes neuronal survival and can help neurons resist toxic insults. Paradoxically, BDNF/TrkB signaling has also been shown, under certain in vitro circumstances, to render neurons vulnerable to insults. We show here that in vivo conditional deletion of TrkB from mature motor neurons attenuates mutant superoxide dismutase 1 (SOD1) toxicity. Mutant SOD1 mice lacking motor neuron TrkB live a month longer than controls and retain motor function for a longer period, particularly in the early phase of the disease. These effects are subserved by slowed motor neuron loss, persistence of neuromuscular junction integrity and reduced astrocytic and microglial reactivity within the spinal cord. These results suggest that manipulation of BDNF/TrkB signaling might have therapeutic efficacy in motor neuron diseases.

Abnormal changes in NKT cells, the IGF-1 axis, and liver pathology in an animal model of ALS

Amyotrophic lateral sclerosis (ALS) is a rapidly progressing fatal neurodegenerative disorder characterized by the selective death of motor neurons (MN) in the spinal cord, and is associated with local neuroinflammation. Circulating CD4⁺ T cells are required for controlling the local detrimental inflammation in neurodegenerative diseases, and for supporting neuronal survival, including that of MN. T-cell deficiency increases neuronal loss, while boosting T cell levels reduces it. Here, we show that in the mutant superoxide dismutase 1 G93A (mSOD1) mouse model of ALS, the levels of natural killer T (NKT) cells increased dramatically, and T-cell distribution was altered both in lymphoid organs and in the spinal cord relative to wild-type mice. The most significant elevation of NKT cells was observed in the liver, concomitant with organ atrophy. Hepatic expression levels of insulin-like growth factor (IGF)-1 decreased, while the expression of IGF binding protein (IGFBP)-1 was augmented by more than 20-fold in mSOD1 mice relative to wild-type animals. Moreover, hepatic lymphocytes of pre-symptomatic mSOD1 mice were found to secrete significantly higher levels of cytokines when stimulated with an NKT ligand, ex-vivo. Immunomodulation of NKT cells using an analogue of α-galactosyl ceramide (α-GalCer), in a specific regimen, diminished the number of these cells in the periphery, and induced recruitment of T cells into the affected spinal cord, leading to a modest but significant prolongation of life span of mSOD1 mice. These results identify NKT cells as potential players in ALS, and the liver as an additional site of major pathology in this disease, thereby emphasizing that ALS is not only a non-cell autonomous, but a non-tissue autonomous disease, as well. Moreover, the results suggest potential new therapeutic targets such as the liver for immunomodulatory intervention for modifying the disease, in addition to MN-based neuroprotection and systemic treatments aimed at reducing oxidative stress.

Emerging drugs for amyotrophic lateral sclerosis

INTRODUCTION

Amyotrophic lateral sclerosis (ALS) is a rapidly progressive neurodegenerative disease that results in increasing disability and that is uniformly fatal. Since its approval in the 1990s, riluzole remains the sole treatment for ALS offering modest survival benefit. While significant advances have been made in the symptomatic management of the disease, more effective drug therapy targeting disease progression is sorely needed.

AREAS COVERED

Advances in the understanding of pathogenic mechanisms involved in disease development and progression have provided multiple avenues for developing effective treatment strategies. This review highlights recent discoveries relating to these diverse mechanisms and their implications for the development of drug therapy. Previous human clinical trials that have targeted these pathways are mentioned and ongoing drug trials are discussed.

EXPERT OPINION

The search for effective drug therapy faces important challenges in the areas of basic science and animal research, translation of these results into human clinical trials, inherent bias in human studies and issues related to delays in clinical diagnosis. How these issues may be addressed and why ALS research constitutes fertile grounds for drug development not only for this devastating disease, but also for other more prevalent neurodegenerative diseases, is discussed in this review.

Evidence-based drug treatment in amyotrophic lateral sclerosis and upcoming clinical trials

Amyotrophic Lateral sclerosis/motor neuron disease is a severe neurodegenerative disease characterized by upper and Lower motor neuron degeneration for which there is no truly effective treatment. Several therapies have shown promise in preclinical models of motor neuron disease; however, most of them failed in human studies, so that the noticeable progress in understanding the cellular mechanisms of motor neuron degeneration has not been matched with the development of therapeutic strategies to prevent disease progression or to extend survival longer than achieved by riluzole. We review treatment development in motor neuron disease and discuss the strengths and limitations of past as well as upcoming clinical trials.

A mutation in the dynein heavy chain gene compensates for energy deficit of mutant SOD1 mice and increases potentially neuroprotective IGF-1

BACKGROUND

Amyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative disease characterized by a progressive loss of motor neurons. ALS patients, as well as animal models such as mice overexpressing mutant SOD1s, are characterized by increased energy expenditure. In mice, this hypermetabolism leads to energy deficit and precipitates motor neuron degeneration. Recent studies have shown that mutations in the gene encoding the dynein heavy chain protein are able to extend lifespan of mutant SOD1 mice. It remains unknown whether the protection offered by these dynein mutations relies on a compensation of energy metabolism defects.

RESULTS

SOD1(G93A) mice were crossbred with mice harboring the dynein mutant Cramping allele (Cra/+ mice). Dynein mutation increased adipose stores in compound transgenic mice through increasing carbohydrate oxidation and sparing lipids. Metabolic changes that occurred in double transgenic mice were accompanied by the normalization of the expression of key mRNAs in the white adipose tissue and liver. Furthermore, Dynein Cra mutation rescued decreased post-prandial plasma triglycerides and decreased non esterified fatty acids upon fasting. In SOD1(G93A) mice, the dynein Cra mutation led to increased expression of IGF-1 in the liver, increased systemic IGF-1 and, most importantly, to increased spinal IGF-1 levels that are potentially neuroprotective.

CONCLUSIONS

These findings suggest that the protection against SOD1(G93A) offered by the Cramping mutation in the dynein gene is, at least partially, mediated by a reversal in energy deficit and increased IGF-1 availability to motor neurons.

Amyotrophic lateral sclerosis is associated with hypolipidemia at the presymptomatic stage in mice

OBJECTIVE

To demonstrate that hypolipidemia is a typical feature of the mouse model of amyotrophic lateral sclerosis (ALS) and to assess the association between hypolipidemia and disease stage, dietary intake, and sex.

METHODS

We compared daily dietary intake, body weight, and serumlipid and glucose levels in ALS mice and wild-type controls at different stages of the disease.

FINDINGS

Total cholesterol low-density lipoprotein (LDL) and LDL/high-density lipoprotein (HDL) ratio were significantly lower in ALS mice compared with controls. Subgroup analysis revealed that the incidence of hypolipidemia was significantly greater in male, but not female, ALS mice compared with control mice and that hypolipidemia was present at the presymptomatic stage of the disease. This hypolipidemia can be found without a decrease in the serum levels of other energy sources, such as glucose, in the presymptomatic stage.

CONCLUSIONS

Hypolipidemia is present at the presymptomatic stage of the ALS mouse model in the absence of malnutrition, significant neuromuscular degeneration or regeneration, and respiratory difficulty. Our findings suggest that hypolipidemia might be associated with the pathomechanism of ALS and/or lipid-specific metabolism rather than simply an epiphenomenon of neuromuscular degeneration or energy imbalance.

The autophagic tumor stroma model of cancer: Role of oxidative stress and ketone production in fueling tumor cell metabolism

A loss of stromal Cav-1 in the tumor fibroblast compartment is associated with early tumor recurrence, lymph-node metastasis, and tamoxifen-resistance, resulting in poor clinical outcome in breast cancer patients. Here, we have used Cav-1 (-/-) null mice as a pre-clinical model for this "lethal tumor micro-environment." Metabolic profiling of Cav-1 (-/-) mammary fat pads revealed the upregulation of numerous metabolites (nearly 100), indicative of a major catabolic phenotype. Our results are consistent with the induction of oxidative stress, mitochondrial dysfunction, and autophagy/mitophagy. The two most prominent metabolites that emerged from this analysis were ADMA (asymmetric dimethyl arginine) and BHB (beta-hydroxybutyrate; a ketone body), which are markers of oxidative stress and mitochondrial dysfunction, respectively. Transcriptional profiling of Cav-1 (-/-) stromal cells and human tumor stroma from breast cancer patients directly supported an association with oxidative stress, mitochondrial dysfunction, and autophagy/mitophagy, as well as ADMA and ketone production. MircoRNA profiling of Cav-1 (-/-) stromal cells revealed the upregulation of two key cancer-related miR's, namely miR-31 and miR-34c. Consistent with our metabolic findings, these miR's are associated with oxidative stress (miR-34c) or activation of the hypoxic response/HIF1a (miR-31), which is sufficient to drive authophagy/mitophagy. Thus, via an unbiased comprehensive analysis of a lethal tumor micro-environment, we have identified a number of candidate biomarkers (ADMA, ketones, and miR-31/34c) that could be used to identify high-risk cancer patients at diagnosis, for treatment stratification and/or for evaluating therapeutic efficacy during anti-cancer therapy. We propose that the levels of these key biomarkers (ADMA, ketones/BHB, miR-31, and miR-34c) could be (1) assayed using serum or plasma from cancer patients, or (2) performed directly on excised tumor tissue. Importantly, induction of oxidative stress and autophagy/mitophagy in the tumor stromal compartment provides a means by which epithelial cancer cells can directly "feed off" of stromal-derived essential nutrients, chemical building blocks (amino acids, nucleotides), and energy-rich metabolites (glutamine, pyruvate, ketones/BHB), driving tumor progression and metastasis. Essentially, aggressive cancer cells are "eating" the cancer-associated fibroblasts via autophagy/mitophagy in the tumor micro-environment. Lastly, we discuss that this "Autophagic Tumor Stroma Model of Cancer Metabolism" provides a viable solution to the "Autophagy Paradox" in cancer etiology and chemo-therapy.

TDP-43-based animal models of neurodegeneration: new insights into ALS pathology and pathophysiology

The clinical and pathological overlap between amyotrophic lateral sclerosis (ALS) and frontotemporal lobar degeneration (FTLD) suggests these diseases share common underlying mechanisms, a suggestion underscored by the discovery that TDP-43 inclusions are a key pathologic feature in both ALS and FTLD. This finding, combined with the identification of TDP-43 mutations in ALS, directly implicates this DNA/RNA binding protein in disease pathogenesis in ALS and FTLD. However, many key questions remain, including what is the normal function of TDP-43, and whether disease-associated mutations produce toxicity in the nucleus, cytoplasm or both. Furthermore, although pathologic TDP-43 inclusions are clearly associated with many forms of neurodegeneration, whether TDP-43 aggregation is a key step in the pathogenesis in ALS, FTLD and other disorders remains to be proven. This review will compare the features of numerous recently developed animal models of TDP-43-related neurodegeneration, and discuss how they contribute to our understanding of the pathogenesis of human ALS and FTLD.

Patients with elevated triglyceride and cholesterol serum levels have a prolonged survival in amyotrophic lateral sclerosis

Weight loss is a common phenomenon and an independent prognostic factor in amyotrophic lateral sclerosis (ALS). Several potential causal mechanisms, including intrinsic hypermetabolism and deficient food intake, have been discussed. We investigated the influence of fasting serum glucose, cholesterol, and triglyceride levels at time of diagnosis on survival in ALS. Serum cholesterol (LDL, HDL, and LDL/HDL ratio), triglycerides, and glucose were investigated in 488 patients (age of onset = 57.6 ± 12.6 years) in relation to survival and revised Amyotrophic Lateral Sclerosis Functional Rating Scale (ALS-FRS) data. High serum levels of both fasting cholesterol and triglycerides had a significantly positive effect on survival (p < 0.05). We found a median prolonged life expectancy by 14 months for patients with serum triglyceride levels above the median of 1.47 mmol/l. The results suggest that the lipid metabolism and the nutritional status of ALS patients are important prognostic factors. These parameters should be thoroughly monitored during the clinical management of these patients. In case of progressive loss of body weight, a diet rich in lipids and calories should be considered. However, the final decision whether a lipid-rich diet should be recommended to ALS patients can only be based on a double-blind placebo-controlled interventional trial. Our results further imply that lipid-lowering drugs, e.g., statins, should be applied carefully in ALS patients although individual risk considerations must be made.

Characterization of a novel SOD-1(G93A) transgenic mouse line with very decelerated disease development

Amyotrophic Lateral Sclerosis (ALS) is a fatal motoneuron disease, characterized by progressive weakness, muscle wasting and death ensuing 3-5 years after diagnosis. The etiology of ALS is complex and therapeutic approaches rely mostly on transgenic animal models with SOD-1 mutations. Most frequently employed is a mouse line transgenic for SOD-1 (SOD-1 Tg) that contains a point mutation at amino acid position 93 (G->A), present in patients suffering from a familial form of amyotrophic lateral sclerosis. Here we report on a SOD-1 (G93A) Tg mouse line with abnormally delayed onset of disease and prolonged survival. This phenotype arose spontaneously in our colony of the classic SOD-1 (G93A) line. We found that the copy number of the SOD-1 transgene was drastically decreased. We established a new breeding colony, the SOD-1 (G93A)(PS) line (PS for prolonged survival) where the phenotype is stably inherited for 4 generations now. The mice develop symptoms at an age of approximately 12 months and die at 15 months of age. The delayed development of disease may more closely mimic human pathophysiology, and studying drug effects in this model may yield added confidence for potential efficacy of ALS drug candidates.

Ldlr-/- mice display decreased susceptibility to Western-type diet-induced obesity due to increased thermogenesis

The low-density lipoprotein receptor (Ldlr) is a key molecule involved with lipid clearance. The Ldlr(-/-) mouse has been used extensively as a model for studying atherosclerosis. This study sought to characterize the energy balance phenotype of Ldlr(-/-) mice with respect to weight gain, body composition, energy expenditure (EE), glucose homeostasis, and leptin sensitivity. Adult Ldlr(-/-) mice and Ldlr(+/+) controls on a C57Bl/6J background were fed either a chow or a high-fat, high-sucrose Western-type diet (WTD) for eight wk. Physiological studies of food intake, EE, activity, insulin sensitivity, and leptin responsiveness were performed. The effect of these diet interventions on circulating leptin and on leptin gene expression was also examined. On the chow diet, Ldlr(-/-) mice had lower EE and higher activity levels relative to controls. On the WTD, Ldlr(-/-) mice gained less weight relative to Ldlr(+/+) mice, specifically gaining less fat mass. Increased thermogenesis in Ldlr(-/-) mice fed the WTD was detected. Additionally, leptin responsiveness was blunted in chow-fed Ldlr(-/-) mice, suggesting a novel role for the Ldlr pathway that extends to leptin's regulation of energy balance. In addition to its known role in lipid transport, these results demonstrate the importance of the Ldlr in energy homeostasis and suggest a direct physiological link between altered lipid transport and energy balance.

Energy metabolism in amyotrophic lateral sclerosis

Amyotrophic lateral sclerosis (ALS) is characterised by the progressive degeneration of upper and lower motor neurons. Besides motor neuron degeneration, ALS is associated with several defects in energy metabolism, including weight loss, hypermetabolism, and hyperlipidaemia. Most of these abnormalities correlate with duration of survival, and available clinical evidence supports a negative contribution of defective energy metabolism to the overall pathogenic process. Findings from animal models of ALS support this view and provide insights into the underlying mechanisms. Altogether, these results have clinical consequences for the management of defective energy metabolism in patients with ALS and pave the way for future therapeutic interventions.

Platelet serotonin level predicts survival in amyotrophic lateral sclerosis

BACKGROUND

Amyotrophic lateral sclerosis (ALS) is a life-threatening neurodegenerative disease involving upper and lower motor neurons loss. Clinical features are highly variable among patients and there are currently few known disease-modifying factors underlying this heterogeneity. Serotonin is involved in a range of functions altered in ALS, including motor neuron excitability and energy metabolism. However, whether serotoninergic activity represents a disease modifier of ALS natural history remains unknown.

METHODOLOGY

Platelet and plasma unconjugated concentrations of serotonin and plasma 5-HIAA, the major serotonin metabolite, levels were measured using HPLC with coulometric detection in a cohort of 85 patients with ALS all followed-up until death and compared to a control group of 29 subjects.

PRINCIPAL FINDINGS

Platelet serotonin levels were significantly decreased in ALS patients. Platelet serotonin levels did not correlate with disease duration but were positively correlated with survival of the patients. Univariate Cox model analysis showed a 57% decreased risk of death for patients with platelet serotonin levels in the normal range relative to patients with abnormally low platelet serotonin (p = 0.0195). This protective effect remained significant after adjustment with age, gender or site of onset in multivariate analysis. Plasma unconjugated serotonin and 5-HIAA levels were unchanged in ALS patients compared to controls and did not correlate with clinical parameters.

CONCLUSIONS/SIGNIFICANCE

The positive correlation between platelet serotonin levels and survival strongly suggests that serotonin influences the course of ALS disease.

Skeletal muscle in motor neuron diseases: therapeutic target and delivery route for potential treatments

Lower motor neuron (LMN) degeneration occurs in several diseases that affect patients from neonates to elderly and can either be genetically transmitted or occur sporadically. Among diseases involving LMN degeneration, spinal muscular atrophy (SMA) and spinal bulbar muscular atrophy (Kennedy's disease, SBMA) are pure genetic diseases linked to loss of the SMN gene (SMA) or expansion of a polyglutamine tract in the androgen receptor gene (SBMA) while amyotrophic lateral sclerosis (ALS) can either be of genetic origin or occur sporadically. In this review, our aim is to put forward the hypothesis that muscle fiber atrophy and weakness might not be a simple collateral damage of LMN degeneration, but instead that muscle fibers may be the site of crucial pathogenic events in these diseases. In SMA, the SMN gene was shown to be required for muscle structure and strength as well as for neuromuscular junction formation, and a subset of SMA patients develop myopathic pathology. In SBMA, the occurrence of myopathic histopathology in patients and animal models, along with neuromuscular phenotype of animal models expressing the androgen receptor in muscle only has lead to the proposal that SBMA may indeed be a muscle disease. Lastly, in ALS, at least part of the phenotype might be explained by pathogenic events occuring in skeletal muscle. Apart from its potential pathogenic role, skeletal muscle pathophysiological events might be a target for treatments and/or be a preferential route for targeting motor neurons.

Mutations in cytoplasmic dynein lead to a Huntington's disease-like defect in energy metabolism of brown and white adipose tissues

The molecular motor dynein is regulated by the huntingtin protein, and Huntington's disease (HD) mutations of huntingtin disrupt dynein motor activity. Besides abnormalities in the central nervous system, HD animal models develop prominent peripheral pathology, with defective brown tissue thermogenesis and dysfunctional white adipocytes, but whether this peripheral phenotype is recapitulated by dynein dysfunction is unknown. Here, we observed prominently increased adiposity in mice harboring the legs at odd angles (Loa/+) or the Cramping mutations (Cra/+) in the dynein heavy chain gene. In Cra/+ mice, hyperadiposity occurred in the absence of energy imbalance and was the result of impaired norepinephrine-stimulated lipolysis. A similar phenotype was observed in 3T3L1 adipocytes upon chemical inhibition of dynein showing that loss of functional dynein leads to impairment of lipolysis. Ex vivo, dynein mutant adipose tissue displayed increased reactive oxygen species production that was, at least partially, responsible for the decreased cellular responses to norepinephrine and subsequent defect in stimulated lipolysis. Dynein mutation also affected norepinephrine efficacy to elicit a thermogenic response and led to morphological abnormalities in brown adipose tissue and cold intolerance in dynein mutant mice. Interestingly, protein levels of huntingtin were decreased in dynein mutant adipose tissue. Collectively, our results provide genetic evidence that dynein plays a key role in lipid metabolism and thermogenesis through a modulation of oxidative stress elicited by norepinephrine. This peripheral phenotype of dynein mutant mice is similar to that observed in various animal models of HD, lending further support for a functional link between huntingtin and dynein.

Sperm and oocyte communication mechanisms controlling C. elegans fertility

During sexual reproduction in many species, sperm and oocyte secrete diffusible signaling molecules to help orchestrate the biological symphony of fertilization. In the Caenorhabditis elegans gonad, bidirectional signaling between sperm and oocyte is important for guiding sperm to the fertilization site and inducing oocyte maturation. The molecular mechanisms that regulate sperm guidance and oocyte maturation are being delineated. Unexpectedly, these mechanisms are providing insight into human diseases, such as amyotrophic lateral sclerosis, spinal muscular atrophy, and cancer. Here we review sperm and oocyte communication in C. elegans and discuss relationships to human disorders.

Impaired glucose tolerance in patients with amyotrophic lateral sclerosis

Our objectives were to analyse carbohydrate metabolism in a series of ALS patients and to examine potential association with parameters of lipid metabolism and clinical features. Glucose tolerance was assessed by the oral glucose tolerance test in 21 non-diabetic ALS patients and compared with 21 age- and sex-matched normal subjects. Lipids and lactate/pyruvate ratio, levels of pro-inflammatory cytokines (tumour necrosis factor-alpha and interleukin-6) and adipocytokines (leptin and adiponectin) were also measured in ALS patients. Mann-Whitney U-tests analysed continuous data and Fisher's exact tests assessed categorical data. Blood glucose determined 120 min after the glucose bolus was significantly higher in patients with ALS (7.41 mmol/l+/-1.68) compared to controls (6.05+/-1.44, p=0.006). ALS patients with impaired glucose tolerance (IGT) according to WHO criteria (n=7, 33%) were more likely to have elevated free fatty acids (FFA) levels compared to patients with normal glucose tolerance (0.77 nmol/l+/-0.30 vs. 0.57+/-0.19, p=0.04). IGT was not associated with disease duration or severity. In conclusion, patients with ALS show abnormal glucose tolerance that could be associated with increased FFA levels, a key determinant of insulin resistance. The origin of glucose homeostasis abnormalities in ALS may be multifactorial and deserves further investigation.

Malnutrition at the time of diagnosis is associated with a shorter disease duration in ALS

BACKGROUND

Amyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative disease. During the course of the illness, malnutrition can occur and may shorten survival. The aim of our study was to determine whether clinical nutritional parameters that are used in daily practice are associated with prognosis and whether they can help guide therapeutic decisions.

METHODS

We retrospectively reviewed a cohort of ALS patients in our institution between January 2002 and January 2006. Clinical and demographic outcomes were compiled. To evaluate predictors of survival, we analyzed several clinical nutritional parameters available in daily practice (body mass index, weight loss exceeding 10% of premorbid weight at the time of diagnosis and during the course of the disease and the use of technical supports such as percutaneous endoscopic gastrostomy (PEG) and non-invasive ventilation).

RESULTS

Sixty-three patients were retrospectively studied. Thirteen patients had weight loss exceeding 10% of premorbid weight at the time of diagnosis and thirty patients had weight loss meeting this criterion at final examination. Weight loss exceeding 10% at the time of diagnosis was associated with a shorter duration of disease (17±6months versus 35±26months; p=0.002). A linear correlation was found between mean disease duration and time between onset and diagnosis (p<0.0001). The subgroup of patients with a PEG had a longer survival time than the other subgroup of patients (p=0.02).

CONCLUSIONS

In ALS patients, early and marked weight loss significantly predicts a worse prognosis. The percentage of premorbid weight loss is a suitable and useful measure that can be used in daily practice to identify patients with a poor prognosis.

Deletion of TDP-43 down-regulates Tbc1d1, a gene linked to obesity, and alters body fat metabolism

Tat activating regulatory DNA-binding protein (Tardbp or TDP-43), a highly conserved metazoan DNA/RNA binding protein thought to be involved in RNA transcription and splicing, has been linked to the pathophysiology of amyotrophic lateral sclerosis and frontotemporal lobar degeneration and is essential for early embryonic development. However, neither the physiological role of TDP-43 in the adult nor its downstream targets are well defined. To address these questions, we developed conditional Tardbp-KO mice and embryonic stem (ES) cell models. Here, we show that postnatal deletion of Tardbp in mice caused dramatic loss of body fat followed by rapid death. Moreover, conditional Tardbp-KO ES cells failed to proliferate. Importantly, high-throughput DNA sequencing analysis on the transcriptome of ES cells lacking Tardbp revealed a set of downstream targets of TDP-43. We show that Tbc1d1, a gene known to mediate leanness and linked to obesity, is down-regulated in the absence of TDP-43. Collectively, our results establish that TDP-43 is critical for fat metabolism and ES cell survival.

A decrease in body mass index is associated with faster progression of motor symptoms and shorter survival in ALS

Our objective was to test the hypothesis that changes in body mass index (BMI) are associated with changes in the clinical course of ALS. We examined the relationships between BMI at first clinical visit and changes in BMI up to a two-year follow-up, and multiple clinical variables related to ALS: age of onset, rate of progression of motor symptoms, and survival. Baseline BMI was classified according to the World Health Organization (WHO) criteria. Changes in BMI were classified as a loss of >1 unit, no change, or a gain of >1 unit. Our results showed that baseline BMI was not associated with age of onset, rate of progression or survival. In contrast, a loss of BMI >1 over two years was associated with significantly shorter survival and a faster rate of progression. In a multiple regression model, these results were independent of gender, site of onset, history of diabetes mellitus and apolipoprotein (ApoE) genotype. In summary, a change in BMI after ALS diagnosis was significantly associated with rate of progression and survival. This raises the possibility that early changes in BMI may identify patients likely to have a more malignant course of the disease. However, further research is needed to clarify the relationship between BMI and ALS.

Significance of behavioural tests in a transgenic mouse model of amyotrophic lateral sclerosis (ALS)

Amyotrophic Lateral Sclerosis (ALS) is a devastating adult-onset motor neuron disorder with marginal therapeutic options. The disease is characterized by progressive degeneration of motor neurons in spinal cord and motor cortex. Transgenic mice carrying the G93A mutation of the superoxide dismutase 1 (SOD1) gene develop a neurodegenerative disease closely mimicking human ALS. Several methods are currently used to record disease onset and progression of the animals in preclinical studies. For the interpretation of these preclinical trials, it is important to assess neurological function as sensitively as possible. In the present study, five different parameters (rotarod performance, weight, footprint analysis for both step length and runtime and the general condition of the mice scored from 1 to 5) were compared with respect to their significance to detect symptom onset and to monitor disease progression in transgenic G93A ALS mice. The rotarod and footprint analyses were performed weekly while the weight was recorded up to three times a week at later time points. General condition was assessed daily. First deficits were detected by rotarod testing and step length analyses. General condition score and weight showed first changes two weeks later. For preclinical testing of novel drug treatments rotarod and footprint analysis for step length therefore seem to be the most effective methods to detect symptom onset and potential treatment induced improvements.

[Nutritional problems in multiple system atrophy--necessity of early tube feeding and caloric restriction at the advanced stage]

We investigated nutritional states of 28 patients with multiple system atrophy (MSA) by measuring body mass index (BMI), arm muscle circumference (% AMC) and triceps skin fold thickness (% TSF). We also analyzed retrospectively chronological changes of nutritional status in 13 MSA patients surviving more than 10 years. BMI and % AMC were significantly reduced in patients having tube feeding compared with patients who had oral intake, whereas % TSF was increased in some patients with tube feeding. From the chronological study, patients at the stage of respiratory or swallowing deterioration showed marked malnutrition, whereas patients during the advanced, but stable stages with tracheostomy and gastrostomy showed much fat accumulation even under low calorie intake less than 1,000 kcal/day. Daily amount of calorie intake should be sufficient during respiratory or swallowing deterioration, but it should be restricted at the advanced stable stage to avoid fat accumulation.

Skeletal muscle-restricted expression of human SOD1 causes motor neuron degeneration in transgenic mice

Amyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative disease of motor neurons (MNs) that causes skeletal muscle paralysis. Familial forms of ALS are linked to mutations in the superoxide dismutase-1 (SOD1) gene. The mechanisms of human SOD1 (hSOD1) toxicity to MNs are unknown. We hypothesized that skeletal muscle is a primary site of pathogenesis in ALS that triggers MN degeneration. We created transgenic (tg) mice expressing wild-type-, G37R- and G93A-hSOD1 gene variants only in skeletal muscle. These tg mice developed age-related neurologic and pathologic phenotypes consistent with ALS. Affected mice showed limb weakness and paresis with motor deficits. Skeletal muscles developed severe pathology involving oxidative damage, protein nitration, myofiber cell death and marked neuromuscular junction (NMJ) abnormalities. Spinal MNs developed distal axonopathy and formed ubiquitinated inclusions and degenerated through an apoptotic-like pathway involving capsase-3. Mice expressing wild-type and mutant forms of hSOD1 developed MN pathology. These results demonstrate that human SOD1 in skeletal muscle has a causal role in ALS and identify a new non-autonomous mechanism for MN degeneration explaining their selective vulnerability. The discovery of instigating molecular toxicities or disease progression determinants within skeletal muscle could be very valuable for the development of new effective therapies for the treatment and cure of ALS.

P-glycoprotein expression and function are increased in an animal model of amyotrophic lateral sclerosis

The efflux pumps located at the blood-brain barrier (BBB) prevent drugs entering the brain. As such, efflux pumps are a major obstacle to drug brain distribution. Amyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative disease with little therapeutics available: riluzole is the only drug approved in its treatment. The lack of response to treatment in ALS may be, at least in part, due to increased activities of efflux pumps in relation to disease, leading to subtherapeutic brain concentrations of drugs. In the present study, we used a transgenic mouse model of ALS (G86R mSOD1 mice) to test this hypothesis. Expression and functionality of P-glycoprotein (ABCB1, P-gp) and Breast Cancer Resistance Protein (ABCG2, BCRP), two major efflux pumps, were studied. We observed an increased P-gp expression (1.5-fold) in presymptomatic mSOD1 mice compared to wild-type controls. Consistent with this, P-gp function was also increased by 1.5-fold and riluzole brain disposition was decreased by 1.7-fold in mSOD1 mice. Contrasting with this, BCRP expression and function were unaltered by the pathology. These results demonstrate that BBB transport proteins are modified in G86R mSOD1 mice ALS model. Such findings underline potential problems in extrapolating the results of animal studies to humans and developing clinical trials, especially for drugs transported by P-gp.

ALS disease onset may occur later in patients with pre-morbid diabetes mellitus

BACKGROUND

Several metabolic derangements associated with diabetes mellitus type 2 (DM) have been associated with a better outcome in amyotrophic lateral sclerosis (ALS), including hyperlipidemia and obesity. Here, we tested the hypothesis that DM would have a positive effect on the motor and cognitive findings of ALS.

METHODS

We compared data from ALS patients with pre-morbid DM (ALS-DM; n = 175) versus without DM (ALS; n = 2196) with regard to the age of onset, rate of motor progression, survival, and neuropsychological test performance.

RESULTS

The age of onset was later for women, Caucasians and patients with bulbar-onset ALS. However, we also found that after adjusting for gender, ethnicity and site of onset, DM was associated with a 4-year later onset of ALS (ALS = 56.3, ALS-DM = 60.3, P < 0.05).

CONCLUSION

Diabetes mellitus type 2 may delay the onset of motor symptoms in ALS. These findings support other studies suggesting a relationship between the pathophysiology of ALS and metabolic derangements. Further investigations are needed to ascertain whether manipulating metabolic parameters would improve outcomes in ALS.

Oxygen sensing: a common crossroad in cancer and neurodegeneration

Prolyl hydroxylase domain (PHD) proteins are cellular oxygen sensors that orchestrate an adaptive response to hypoxia and oxidative stress, executed by hypoxia-inducible factors (HIFs). By increasing oxygen supply, reducing oxygen consumption, and reprogramming metabolism, the PHD/HIF pathway confers tolerance towards hypoxic and oxidative stress. This review discusses the involvement of the PHD/HIF response in two, at first sight, entirely distinct pathologies with opposite outcome, i.e. cancer leading to cellular growth and neurodegeneration resulting in cell death. However, these disorders share common mechanisms of sensing oxygen and oxidative stress. We will focus on how PHD/HIF signaling is pathogenetically implicated in metabolic and vessel alterations in these diseases and how manipulation of this pathway might offer novel treatment opportunities.

Lipid oxidation and peroxidation in CNS health and disease: from molecular mechanisms to therapeutic opportunities

Reactive oxygen species (ROS) are produced at low levels in mammalian cells by various metabolic processes, such as oxidative phosphorylation by the mitochondrial respiratory chain, NAD(P)H oxidases, and arachidonic acid oxidative metabolism. To maintain physiological redox balance, cells have endogenous antioxidant defenses regulated at the transcriptional level by Nrf2/ARE. Oxidative stress results when ROS production exceeds the cell's ability to detoxify ROS. Overproduction of ROS damages cellular components, including lipids, leading to decline in physiological function and cell death. Reaction of ROS with lipids produces oxidized phospholipids, which give rise to 4-hydroxynonenal, 4-oxo-2-nonenal, and acrolein. The brain is susceptible to oxidative damage due to its high lipid content and oxygen consumption. Neurodegenerative diseases (AD, ALS, bipolar disorder, epilepsy, Friedreich's ataxia, HD, MS, NBIA, NPC, PD, peroxisomal disorders, schizophrenia, Wallerian degeneration, Zellweger syndrome) and CNS traumas (stroke, TBI, SCI) are problems of vast clinical importance. Free iron can react with H(2)O(2) via the Fenton reaction, a primary cause of lipid peroxidation, and may be of particular importance for these CNS injuries and disorders. Cholesterol is an important regulator of lipid organization and the precursor for neurosteroid biosynthesis. Atherosclerosis, the major risk factor for ischemic stroke, involves accumulation of oxidized LDL in the arteries, leading to foam cell formation and plaque development. This review will discuss the role of lipid oxidation/peroxidation in various CNS injuries/disorders.

The metabolic phenotype of SCD1-deficient mice is independent of melanin-concentrating hormone

We propose that deletion of pro-melanin-concentrating hormone (pMCH) would increase energy expenditure and further improve glucose tolerance in mice lacking stearoyl-coA desaturase-1 (SCD1). To test our hypothesis, we bred and metabolically challenged Pmch-/-; Scd1-/- double-knockout mice, with comparison to Pmch-/- mice; Scd1-/- mice and C57Bl/6J controls. Deletion of both Pmch and Scd1 increased both food intake and energy expenditure relative to control mice. Pmch-/-; Scd1-/- double-knockout mice had improved glucose tolerance relative to control mice. The majority of the metabolic effects were contributed by inactivation of the Scd1 gene. We conclude that the increased food intake and increased energy expenditure of Scd1-/- mice are independent of the neuropeptide melanin-concentrating hormone.

The failure of mitochondria leads to neurodegeneration: Do mitochondria need a jump start?

Mitochondria are the power engine generating biochemical energy in the cell. Mitochondrial dysfunction and bioenergy deficiency is closely linked to the pathogenesis of neurodegenerative disorders. Mitochondria play a variety of roles by integrating extracellular signals and executing important intracellular events in neuronal survival and death. In this context, the regulation of mitochondrial function via therapeutic approaches may exert some salutary and neuroprotective mechanisms. Understanding the relationship of mitochondria-dependent pathogenesis may provide important pharmacological utility in the treatment of neurodegenerative conditions such as Alzheimer's disease, amyotrophic lateral sclerosis, Huntington's disease and Parkinson's disease. Indeed, the modulation of mitochondrial pathways is rapidly emerging as a novel therapeutic target. This review focuses on how mitochondria are involved in neurodegeneration and what therapeutics are available to target mitochondrial pathways.

Effect of diet on the survival and phenotype of a mouse model for spinal muscular atrophy

Proximal spinal muscular atrophy (SMA) is a leading genetic cause of infant death. Patients with SMA lose alpha-motor neurons in the ventral horn of the spinal cord which leads to skeletal muscle weakness and atrophy. SMA is the result of reduction in Survival Motor Neuron (SMN) expression. Transgenic mouse models of SMA have been generated and are extremely useful in understanding the mechanisms of motor neuron degeneration in SMA and in developing new therapeutic candidates for SMA patients. Several research groups have reported varying average lifespans of SMNDelta7 SMA mice (SMN2(+/+);SMNDelta7(+/+);mSmn(-/-)), the most commonly used mouse model for preclinical therapeutic candidate testing. One environmental factor that varied between research groups was maternal diet. In this study, we compared the effects of two different commercially available rodent chows (PicoLab20 Mouse diet and Harlan-Teklad 22/5 diet) on the survival and motor phenotype of the SMNDelta7 mouse model of SMA. Specifically, the PicoLab20 diet significantly extends the average lifespan of the SMNDelta7 SMA mice by approximately 25% and improved the motor phenotype as compared to the Harlan diet. These findings indicate that maternal diet alone can have considerable impact on the SMA phenotype.

Dynamic NAD(P)H post-synaptic autofluorescence signals for the assessment of mitochondrial function in a neurodegenerative disease: monitoring the primary motor cortex of G93A mice, an amyotrophic lateral sclerosis model

Abnormal mitochondrial function was reported in patients and models for amyotrophic lateral sclerosis (ALS). It is therefore important to set up sensitive tools for the monitoring of active agents that enhance energy metabolism delay onset, and extend lifespan of transgenic G93A-SOD1 ALS mice. In this report, primary motor cortex slices from G93A mice at different stages of disease were studied, using NAD(P)H autofluorescence post-synaptic signals following ultraviolet stimuli, as a probe to evaluate mitochondrial function. We observed consistent age-related alterations of responses in G93A primary motor cortex slices versus controls. We conclude that NAD(P)H autofluorescence post-synaptic signal is a highly sensitive real-time technique to detect mitochondrial function failure in primary cortex from living tissues.

Nutritional and exercise-based interventions in the treatment of amyotrophic lateral sclerosis

BACKGROUND & AIMS

Disease pathogenesis in amyotrophic lateral sclerosis (ALS) involves a number of interconnected mechanisms all resulting in the rapid deterioration of motor neurons. The main mechanisms include enhanced free radical production, protein misfolding, aberrant protein aggregation, excitotoxicity, mitochondrial dysfunction, neuroinflammation and apoptosis. The aim of this review is to assess the efficacy of using nutrition- and exercise-related interventions to improve disease outcomes in ALS.

METHODS

Studies involving nutrition or exercise in human and animal models of ALS were reviewed.

RESULTS

Treatments conducted in animal models of ALS have not consistently translated into beneficial results in clinical trials due to poor design, lack of power and short study duration, as well as differences in the genetic backgrounds, treatment dosages and disease pathology between animals and humans. However, vitamin E, folic acid, alpha lipoic acid, lyophilized red wine, coenzyme Q10, epigallocatechin gallate, Ginkgo biloba, melatonin, Cu chelators, and regular low and moderate intensity exercise, as well as treatments with catalase and l-carnitine, hold promise to mitigating the effects of ALS, whereas caloric restriction, malnutrition and high-intensity exercise are contraindicated in this disease model.

CONCLUSIONS

Improved nutritional status is of utmost importance in mitigating the detrimental effects of ALS.

Motoneuron survival is promoted by specific exercise in a mouse model of amyotrophic lateral sclerosis

Several studies using transgenic mouse models of familial amyotrophic lateral sclerosis (ALS) have reported a life span increase in exercised animals, as long as animals are submitted to a moderate-intensity training protocol. However, the neuroprotective potential of exercise is still questionable. To gain further insight into the cellular basis of the exercise-induced effects in neuroprotection, we compared the efficiency of a swimming-based training, a high-frequency and -amplitude exercise that preferentially recruits the fast motor units, and of a moderate running-based training, that preferentially triggers the slow motor units, in an ALS mouse model. Surprisingly, we found that the swimming-induced benefits sustained the motor function and increased the ALS mouse life span by about 25 days. The magnitude of this beneficial effect is one of the highest among those induced by any therapeutic strategy in this disease. We have shown that, unlike running, swimming significantly delays spinal motoneuron death and, more specifically, the motoneurons of large soma area. Analysis of the muscular phenotype revealed a swimming-induced relative maintenance of the fast phenotype in fast-twitch muscles. Furthermore, the swimming programme preserved astrocyte and oligodendrocyte populations in ALS spinal cord. As a whole, these data are highly suggestive of a causal relationship not only linking motoneuron activation and protection, but also motoneuron protection and the maintenance of the motoneuron surrounding environment. Basically, exercise-induced neuroprotective mechanisms provide an example of the molecular adaptation of activated motoneurons.

Light therapy and supplementary Riboflavin in the SOD1 transgenic mouse model of familial amyotrophic lateral sclerosis (FALS)

BACKGROUND AND OBJECTIVE

Familial amyotrophic lateral sclerosis (FALS) is a neurodegenerative disease characterized by progressive loss of motor neurons and death. Mitochondrial dysfunction and oxidative stress play an important role in motor neuron loss in ALS. Light therapy (LT) has biomodulatory effects on mitochondria. Riboflavin improves energy efficiency in mitochondria and reduces oxidative injury. The purpose of this study was to examine the synergistic effect of LT and riboflavin on the survival of motor neurons in a mouse model of FALS.

STUDY DESIGN/MATERIALS AND METHODS

G93A SOD1 transgenic mice were divided into four groups: Control, Riboflavin, Light, and Riboflavin+Light (combination). Mice were treated from 51 days of age until death. A single set of LT parameters was used: 810 nm diode laser, 140-mW output power, 1.4 cm(2) spot area, 120 seconds treatment duration, and 12 J/cm(2) energy density. Behavioral tests and weight monitoring were done weekly. At end stage of the disease, mice were euthanized, survival data was collected and immunohistochemistry and motor neuron counts were performed.

RESULTS

There was no difference in survival between groups. Motor function was not significantly improved with the exception of the rotarod test which showed significant improvement in the Light group in the early stage of the disease. Immunohistochemical expression of the astrocyte marker, glial fibrilary acidic protein, was significantly reduced in the cervical and lumbar enlargements of the spinal cord as a result of LT. There was no difference in the number of motor neurons in the anterior horn of the lumbar enlargement between groups.

CONCLUSIONS

The lack of significant improvement in survival and motor performance indicates study interventions were ineffective in altering disease progression in the G93A SOD1 mice. Our findings have potential implications for the conceptual use of light to treat other neurodegenerative diseases that have been linked to mitochondrial dysfunction.

High metabolic level in patients with familial amyotrophic lateral sclerosis

An abnormally elevated level of resting energy expenditure (REE, measured by indirect calorimetry) has been reported in a subset of patients with sporadic amyotrophic lateral sclerosis (SALS). Hypermetabolism (measured REE/calculated REE (cREE)> or =1.1, or 110%) has also been observed in transgenic mice harbouring ALS-causing mutations in the SOD1 gene. By contrast, the REE of patients with familial amyotrophic lateral sclerosis (FALS) has never been assessed. Our objective was to evaluate the metabolic and nutritional parameters of FALS patients and to compare them with those of SALS patients, and search for correlations with clinical parameters. Eleven patients with FALS (from 10 different families, none carrying a SOD1 mutation) were evaluated by indirect calorimetry in our centre. As a control group, we used a sample of 33 patients with SALS, matched for age and sex with the FALS patients. 11/11 (100%) patients with FALS were hypermetabolic, compared to 17/33 (52%) patients with SALS (p=0.009). Measured REE (mREE) and mREE/cREE (metabolic level) were significantly higher in FALS patients than in SALS patients (p=0.03 and p=0.0008, respectively). No correlation was found between metabolic measures and neurological or respiratory parameters. In conclusion, hypermetabolism appears to be a common feature of subjects with FALS, suggesting that this impairment of energy homeostasis may be genetically driven. The high metabolic level of FALS patients should be taken into account for their nutritional management (need for a high-energy diet to prevent malnutrition).

Decline in daily running distance presages disease onset in a mouse model of ALS

Amyotrophic lateral sclerosis (ALS) is characterized by progressive degeneration of lower motor neurons resulting in paralysis and death. Epidemiological and clinical findings suggest that a decline in athletic performance may presage the clinical onset of ALS, but this possibility has not been tested in an animal model. By placing running wheels in each mouse's cage to measure their exercise activity, we show that presymptomatic G93A SOD1 ALS mice are more active runners (15-20 km/day) than control mice (7-9 km/day). The ALS mice then exhibit a sharp decline in daily running distance 10-20 days prior to the onset of clinical disease. Within the group of ALS mice, there were no significant correlations between cumulative lifetime running distance and age at clinical disease onset or age at death, suggesting that amount of exercise did not affect the course of the disease process. Our data show that presymptomatic ALS mice have a propensity for running long distances, and then dramatically reduce the amount they run prior to the appearance of clinical symptoms. The monitoring of voluntary running distance may provide a valuable biomarker to evaluate the efficacy of potential therapeutic interventions for ALS in preclinical studies.