Gender-Specific Beneficial Effects of Docosahexaenoic Acid Dietary Supplementation in G93A-SOD1 Amyotrophic Lateral Sclerosis Mice

Glycogen accumulation modulates life span in a mouse model of amyotrophic lateral sclerosis

Amyotrophic lateral sclerosis (ALS) is a devastating neurodegenerative disease characterized by the progressive loss of motor neurons in the spinal cord. Glial cells, including astrocytes and microglia, have been shown to contribute to neurodegeneration in ALS, and metabolic dysfunction plays an important role in the progression of the disease. Glycogen is a soluble polymer of glucose found at low levels in the central nervous system that plays an important role in memory formation, synaptic plasticity, and the prevention of seizures. However, its accumulation in astrocytes and/or neurons is associated with pathological conditions and aging. Importantly, glycogen accumulation has been reported in the spinal cord of human ALS patients and mouse models. In the present work, using the SOD1G93A mouse model of ALS, we show that glycogen accumulates in the spinal cord and brainstem during symptomatic and end stages of the disease and that the accumulated glycogen is associated with reactive astrocytes. To study the contribution of glycogen to ALS progression, we generated SOD1G93A mice with reduced glycogen synthesis (SOD1G93A GShet mice). SOD1G93A GShet mice had a significantly longer life span than SOD1G93A mice and showed lower levels of the astrocytic pro-inflammatory cytokine Cxcl10, suggesting that the accumulation of glycogen is associated with an inflammatory response. Supporting this, inducing an increase in glycogen synthesis reduced life span in SOD1G93A mice. Altogether, these results suggest that glycogen in reactive astrocytes contributes to neurotoxicity and disease progression in ALS.

Neuroprotective effects of niclosamide on disease progression via inflammatory pathways modulation in SOD1-G93A and FUS-associated amyotrophic lateral sclerosis models

Amyotrophic lateral sclerosis (ALS) is a complex neurodegenerative disease influenced by genetic, epigenetic, and environmental factors, resulting in dysfunction in cellular and molecular pathways. The limited efficacy of current treatments highlights the need for combination therapies targeting multiple aspects of the disease. Niclosamide, an anthelminthic drug listed as an essential medicine, has been repurposed in clinical trials for different diseases due to its anti-inflammatory and anti-fibrotic properties. Niclosamide can inhibit various molecular pathways (e.g., STAT3, mTOR) that are dysregulated in ALS, suggesting its potential to disrupt these altered mechanisms associated with the pathology. We administered niclosamide intraperitoneally to two transgenic murine models, SOD1-G93A and FUS mice, mimicking key pathological processes of ALS. The treatment was initiated at the onset of symptoms, and we assessed disease progression by neurological scores, rotarod and wire tests, and monitored survival. Furthermore, we investigated cellular and molecular mechanisms affected by niclosamide in the spinal cord and muscle of ALS mice. In both models, the administration of niclosamide resulted in a slowdown of disease progression, an increase in survival rates, and an improvement in tissue pathology. This was characterised by reduced gliosis, motor neuron loss, muscle atrophy, and inflammatory pathways. Based on these results, our findings demonstrate that niclosamide can impact multiple pathways involved in ALS. This multi-targeted approach leads to a slowdown in the progression of the disease, positioning niclosamide as a promising candidate for repurposing in the treatment of ALS.

Gut Symptoms, Gut Dysbiosis and Gut-Derived Toxins in ALS

Many pathogenetic mechanisms have been proposed for amyotrophic lateral sclerosis (ALS). Recently, there have been emerging suggestions of a possible role for the gut microbiota. Gut microbiota have a range of functions and could influence ALS by several mechanisms. Here, we review the possible role of gut-derived neurotoxins/excitotoxins. We review the evidence of gut symptoms and gut dysbiosis in ALS. We then examine a possible role for gut-derived toxins by reviewing the evidence that these molecules are toxic to the central nervous system, evidence of their association with ALS, the existence of biochemical pathways by which these molecules could be produced by the gut microbiota and existence of mechanisms of transport from the gut to the blood and brain. We then present evidence that there are increased levels of these toxins in the blood of some ALS patients. We review the effects of therapies that attempt to alter the gut microbiota or ameliorate the biochemical effects of gut toxins. It is possible that gut dysbiosis contributes to elevated levels of toxins and that these could potentially contribute to ALS pathogenesis, but more work is required.

DHA/EPA (Omega-3) and LA/GLA (Omega-6) as Bioactive Molecules in Neurodegenerative Diseases

Neurodegenerative diseases are characterized by neuroinflammation, neuronal depletion and oxidative stress. They coincide with subtle chronic or flaring inflammation, sometimes escalating with infiltrations of the immune system cells in the inflamed parts causing mild to severe or even lethal damage. Thus, neurodegenerative diseases show all features of autoimmune diseases. Prevalence of neurodegenerative diseases has dramatically increased in recent decades and unfortunately, the therapeutic efficacy and safety profile of available drugs is moderate. The beneficial effects of eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) polyunsaturated fatty acids (omega-3 PUFAs) are nowadays highlighted by a plethora of studies. They play a role in suppression of inflammation, gene expression, cellular membrane fluidity/permeability, immune functionality and intracellular/exocellular signaling. The role of omega-6 polyunsaturated fatty acids, such as linoleic acid (LA), gamma linolenic acid (GLA), and arachidonic acid (AA), on neuroprotection is controversial, as some of these agents, specifically AA, are proinflammatory, whilst current data suggest that they may have neuroprotective properties as well. This review provides an overview of the existing recent clinical studies with respect to the role of omega-3 and omega-6 PUFAs as therapeutic agents in chronic, inflammatory, autoimmune neurodegenerative diseases as well as the dosages and the period used for testing.

Lipid Mediated Brain Disorders: A Perspective

The brain, one of the most resilient organs of the body is highly enriched in lipid content, suggesting the essential role of lipids in brain physiological activities. Lipids constitute an important structural part of the brain and act as a rich source of metabolic energy. Besides, lipids in their bioactive form (known as bioactive lipids) play an essential signaling and regulatory role, facilitating neurogenesis, synaptogenesis, and cell-cell communication. Brain lipid metabolism is thus a tightly regulated process. Any alteration/dysregulation of lipid metabolism greatly impact brain health and activity. Moreover, since central nervous system (CNS) is the most metabolically active system and lacks an efficient antioxidative defence system, it acts as a hub for the production of reactive oxygen species (ROS) and subsequent lipid peroxidation. These peroxidation events are reported during pathological changes such as neuronal tissue injury and inflammation. Present review is a modest attempt to gain insights into the role of dysregulated bioactive lipid levels and lipid oxidation status in the pathogenesis and progression of neurodegenerative disorders. This may open up new avenues exploiting lipids as the therapeutic targets for improving brain health, and treatment of nervous system disorders.

Integrative analysis of metabolomics and proteomics unravels purine metabolism disorder in the SOD1G93A mouse model of amyotrophic lateral sclerosis

Amyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative disease with progressive paralysis of limbs and bulb in patients, the cause of which remains unclear. Accumulating studies suggest that motor neuron degeneration is associated with systemic metabolic impairment in ALS. However, the metabolic reprogramming and underlying mechanism in the longitudinal progression of the disease remain poorly understood. In this study, we aimed to investigate the molecular changes at both metabolic and proteomic levels during disease progression to identify the most critical metabolic pathways and underlying mechanisms involved in ALS pathophysiological changes. Utilizing liquid chromatography-mass spectrometry-based metabolomics, we analyzed the metabolites' levels of plasma, lumbar spinal cord, and motor cortex from SOD1^G93A mice and wildtype (WT) littermates at different stages. To elucidate the regulatory network underlying metabolic changes, we further analyzed the proteomics profile in the spinal cords of SOD1^G93A and WT mice. A group of metabolites implicated in purine metabolism, methionine cycle, and glycolysis were found differentially expressed in ALS mice, and abnormal expressions of enzymes involved in these metabolic pathways were also confirmed. Notably, we first demonstrated that dysregulation of purine metabolism might contribute to the pathogenesis and disease progression of ALS. Furthermore, we discovered that fatty acid metabolism, TCA cycle, arginine and proline metabolism, and folate-mediated one‑carbon metabolism were also significantly altered in this disease. The identified differential metabolites and proteins in our study could complement existing data on metabolic reprogramming in ALS, which might provide new insight into the pathological mechanisms and novel therapeutic targets of ALS.

Lifelong docosahexaenoic acid intervention ameliorates aging in the telomere-DNA-mitochondria axis in telomerase-deficient mice

The health benefits of n-3 polyunsaturated fatty acids (PUFAs) in multiple age-related diseases are associated with telomere length. Telomerase is intimately related to inflammation and oxidative stress, but whether the underlying function of n-3 PUFAs on telomere maintenance is based on telomerase activation or related mechanisms remains unclear. Herein, we utilized late-generation (G4) telomerase-deficient (Terc^-/-) mice to perform a lifelong docosahexaenoic acid (DHA) intervention to determine the potential of DHA in telomere maintenance and health promotion. Unfortunately, DHA failed to prolong mouse longevity in either intrinsic or premature aging. However, intriguingly, lifelong dietary DHA intervention slowed the aging phenotypes and profoundly attenuated telomere attrition in blood leukocytes and multiple tissues, consistent with decreased β-galactosidase activity and other senescence hallmarks with no observed sex differences. Notably, DHA intervention alleviated telomere attrition-induced γ-H2AX accumulation dependent on poly (ADP-ribose) polymerase 1 (PARP1) recruitment, and further regulated mitochondrial dysfunction critically involved in the DNA damage response. Together with the improvement of mitochondria function, the blocked reactive oxygen species (ROS) accumulation and suppression of the nuclear factor-κB (NF-κB)/nucleotide-binding domain-like receptor protein 3 (NLRP3)/caspase-1 pathways partially indicated anti-oxidative and anti-inflammatory effects of DHA. These data revealed a regulatory paradigm involving DHA in the telomere-DNA-mitochondria feedback loop mediated by DNA damage response and inflammation in alleviating senescence, which may hold potential as a translatable intervention in telomere-related diseases during aging.

Dietary-Derived Essential Nutrients and Amyotrophic Lateral Sclerosis: A Two-Sample Mendelian Randomization Study

Previous studies have suggested a close but inconsistent relationship between essential nutrients and the risk of amyotrophic lateral sclerosis (ALS), and whether this association is causal remains unknown. We aimed to investigate the potential causal relation between essential nutrients (essential amino acids, essential fatty acids, essential minerals, and essential vitamins) and the risk of ALS using Mendelian randomization (MR) analysis. Large-scale European-based genome-wide association studies' (GWASs) summary data related to ALS (assembling 27,205 ALS patients and 110,881 controls) and essential nutrient concentrations were separately obtained. MR analysis was performed using the inverse variance-weighted (IVW) method, and sensitivity analysis was conducted by the weighted median method, simple median method, MR-Egger method and MR-PRESSO method. We found a causal association between genetically predicted linoleic acid (LA) and the risk of ALS (OR: 1.066; 95% CI: 1.011-1.125; p = 0.019). An inverse association with ALS risk was noted for vitamin D (OR: 0.899; 95% CI: 0.819-0.987; p = 0.025) and for vitamin E (OR: 0.461; 95% CI: 0.340-0.626; p = 6.25 × 10^-7). The sensitivity analyses illustrated similar trends. No causal effect was observed between essential amino acids and minerals on ALS. Our study profiled the effects of diet-derived circulating nutrients on the risk of ALS and demonstrated that vitamin D and vitamin E are protective against the risk of ALS, and LA is a suggested risk factor for ALS.

Restriction of Dietary Advanced Glycation End Products Induces a Differential Plasma Metabolome and Lipidome Profile

SCOPE

Diets with low content in advanced glycation end products (AGEs) lead to beneficial properties in highly prevalent age-related diseases. To shed light on the mechanisms behind, the changes induced by a low AGE dietary intervention in the circulating metabolome are analyzed.

METHODS AND RESULTS

To this end, 20 non-diabetic patients undergoing peritoneal dialysis are randomized to continue their usual diet or to one with a low content of AGEs for 1 month. Then, plasmatic metabolome and lipidomes are analyzed by liquid-chromatography coupled to mass spectrometry. The levels of defined AGE structures are also quantified by ELISA and by mass-spectrometry. The results show that the low AGE diet impinged significant changes in circulating metabolomes (166 molecules) and lipidomes (91 lipids). Metabolic targets of low-AGE intake include sphingolipid, ether-lipids, and glycerophospholipid metabolism. Further, it reproduces some of the plasma characteristics of healthy aging.

CONCLUSION

The finding of common pathways induced by low-AGE diets with previous metabolic traits implicated in aging, insulin resistance, and obesity suggest the usefulness of the chosen approach and supports the potential extension of this study to other populations.

DNA damage as a mechanism of neurodegeneration in ALS and a contributor to astrocyte toxicity

Increasing evidence supports the involvement of DNA damage in several neurodegenerative diseases, including amyotrophic lateral sclerosis (ALS). Elevated levels of DNA damage are consistently observed in both sporadic and familial forms of ALS and may also play a role in Western Pacific ALS, which is thought to have an environmental cause. The cause of DNA damage in ALS remains unclear but likely differs between genetic subgroups. Repeat expansion in the C9ORF72 gene is the most common genetic cause of familial ALS and responsible for about 10% of sporadic cases. These genetic mutations are known to cause R-loops, thus increasing genomic instability and DNA damage, and generate dipeptide repeat proteins, which have been shown to lead to DNA damage and impairment of the DNA damage response. Similarly, several genes associated with ALS including TARDBP, FUS, NEK1, SQSTM1 and SETX are known to play a role in DNA repair and the DNA damage response, and thus may contribute to neuronal death via these pathways. Another consistent feature present in both sporadic and familial ALS is the ability of astrocytes to induce motor neuron death, although the factors causing this toxicity remain largely unknown. In this review, we summarise the evidence for DNA damage playing a causative or secondary role in the pathogenesis of ALS as well as discuss the possible mechanisms involved in different genetic subtypes with particular focus on the role of astrocytes initiating or perpetuating DNA damage in neurons.

Secondary Metabolites with Antioxidant Activities for the Putative Treatment of Amyotrophic Lateral Sclerosis (ALS): "Experimental Evidences"

Amyotrophic lateral sclerosis (ALS) is a fatal motor neuron disorder that is characterized by progressive loss of the upper and lower motor neurons at the spinal or bulbar level. Oxidative stress (OS) associated with mitochondrial dysfunction and the deterioration of the electron transport chain are factors that contribute to neurodegeneration and perform a potential role in the pathogenesis of ALS. Natural antioxidant molecules have been proposed as an alternative form of treatment for the prevention of age-related neurological diseases, in which ALS is included. Researches support that regulations in cellular reduction/oxidation (redox) processes are being increasingly implicated in this disease, and antioxidant drugs are aimed at a promising pathway to treatment. Among the strategies used for obtaining new drugs, we can highlight the isolation of secondary metabolite compounds from natural sources that, along with semisynthetic derivatives, correspond to approximately 40% of the drugs found on the market. Among these compounds, we emphasize oxygenated and nitrogenous compounds, such as flavonoids, coumarins, and alkaloids, in addition to the fatty acids, that already stand out in the literature for their antioxidant properties, consisting in a part of the diets of millions of people worldwide. Therefore, this review is aimed at presenting and summarizing the main articles published within the last years, which represent the therapeutic potential of antioxidant compounds of natural origin for the treatment of ALS.

Diet, Microbiota and Brain Health: Unraveling the Network Intersecting Metabolism and Neurodegeneration

Increasing evidence gives support for the idea that extra-neuronal factors may affect brain physiology and its predisposition to neurodegenerative diseases. Epidemiological and experimental studies show that nutrition and metabolic disorders such as obesity and type 2 diabetes increase the risk of Alzheimer's and Parkinson's diseases after midlife, while the relationship with amyotrophic lateral sclerosis is uncertain, but suggests a protective effect of features of metabolic syndrome. The microbiota has recently emerged as a novel factor engaging strong interactions with neurons and glia, deeply affecting their function and behavior in these diseases. In particular, recent evidence suggested that gut microbes are involved in the seeding of prion-like proteins and their spreading to the central nervous system. Here, we present a comprehensive review of the impact of metabolism, diet and microbiota in neurodegeneration, by affecting simultaneously several aspects of health regarding energy metabolism, immune system and neuronal function. Advancing technologies may allow researchers in the future to improve investigations in these fields, allowing the buildup of population-based preventive interventions and development of targeted therapeutics to halt progressive neurologic disability.

Lipid metabolism in astrocytic structure and function

Astrocytes are the most abundant glial cell in the central nervous system and are involved in multiple processes including metabolic homeostasis, blood brain barrier regulation and neuronal crosstalk. Astrocytes are the main storage point of glycogen in the brain and it is well established that astrocyte uptake of glutamate and release of lactate prevents neuronal excitability and supports neuronal metabolic function. However, the role of lipid metabolism in astrocytes in relation to neuronal support has been until recently, unclear. Lipids play a fundamental role in astrocyte function, including energy generation, membrane fluidity and cell to cell signaling. There is now emerging evidence that astrocyte storage of lipids in droplets has a crucial physiological and protective role in the central nervous system. This pathway links β-oxidation in astrocytes to inflammation, signalling, oxidative stress and mitochondrial energy generation in neurons. Disruption in lipid metabolism, structure and signalling in astrocytes can lead to pathogenic mechanisms associated with a range of neurological disorders.

Genetics and Sex in the Pathogenesis of Amyotrophic Lateral Sclerosis (ALS): Is There a Link?

Amyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative disease with no known cure. Approximately 90% of ALS cases are sporadic, although multiple genetic risk factors have been recently revealed also in sporadic ALS (SALS). The pathological expansion of a hexanucleotide repeat in chromosome 9 open reading frame 72 (C9orf72) is the most common genetic mutation identified in familial ALS, detected also in 5–10% of SALS patients. C9orf72-related ALS phenotype appears to be dependent on several modifiers, including demographic factors. Sex has been reported as an independent factor influencing ALS development, with men found to be more susceptible than women. Exposure to both female and male sex hormones have been shown to influence disease risk or progression. Moreover, interplay between genetics and sex has been widely investigated in ALS preclinical models and in large populations of ALS patients carrying C9orf72 repeat expansion. In light of the current need for reclassifying ALS patients into pathologically homogenous subgroups potentially responsive to targeted personalized therapies, we aimed to review the recent literature on the role of genetics and sex as both independent and synergic factors, in the pathophysiology, clinical presentation, and prognosis of ALS. Sex-dependent outcomes may lead to optimizing clinical trials for developing patient-specific therapies for ALS.