Repurposing of Trimetazidine for Amyotrophic Lateral Sclerosis: a study in SOD1G93A mice

Comparative Study of Structural and Functional Rearrangements in Skeletal Muscle Mitochondria of SOD1-G93A Transgenic Mice at Pre-, Early-, and Late-Symptomatic Stages of ALS Progression

BACKGROUND

Amyotrophic lateral sclerosis (ALS) is a progressive multisystem disease characterized by limb and trunk muscle weakness that is attributed, in part, to abnormalities in mitochondrial ultrastructure and impaired mitochondrial functions. This study investigated the time course of structural and functional rearrangements in skeletal muscle mitochondria in combination with motor impairments in Tg (copper-zinc superoxide dismutase enzyme (SOD1) G93A) dl1/GurJ (referred to as SOD1-G93A/low) male mice, a familial ALS model, as compared with non-transgenic littermates.

METHODS

The neurological status and motor functions were assessed weekly using the paw grip endurance method and the grid suspension test with two-limb and four-limb suspension tasks. Transmission electron microscopy followed by quantitative analysis was performed to study ultrastructural alterations in the quadriceps femoris. Functional analysis of skeletal muscle mitochondria was performed using high-resolution Oxygraph-2k (O2K) respirometry and methods for assessing the calcium retention capacity index and the content of lipid peroxidation products in freshly isolated preparations.

RESULTS

Based on the behavioral phenotyping data, specific age groups were identified: postnatal day 56 (P56) (n = 10-11), 84 (P84) (n = 10-11), and 156 (P154) (n = 10-12), representing the pre-symptomatic, early-symptomatic and late-symptomatic stages of ALS progression in SOD1-G93A/low mice, respectively. Electron microscopy showed mosaic destructive changes in subsarcolemmal mitochondria in fibers of the quadriceps femoris from 84-day-old SOD1-G93A/low mice. Morphometric analysis revealed an elevation in the mean size of the mitochondria in SOD1-G93A mice at P84 and P154. In addition, the P154 transgenic group demonstrated a decrease in sarcomere width and the number of mitochondria per unit area. At the symptomatic stage, SOD1-G93A mice exhibited a decreased respiratory control ratio, ADP-stimulated, and uncoupled respiration rates of mitochondria isolated from the quadriceps femoris muscle, as measured by high-resolution respirometry. In parallel, the mitochondria showed lower calcium retention capacity and increased levels of lipid peroxidation products compared with the control.

CONCLUSIONS

Taken together, these results indicate stage-dependent changes in skeletal muscle mitochondrial ultrastructure and functions associated with defective oxidative phosphorylation, impaired calcium homeostasis, and oxidative damage in the SOD1-G93A/low mouse model, which appears to be a promising direction for the development of combination therapies for ALS.

Hidden players in the metabolic vulnerabilities of amyotrophic lateral sclerosis

Amyotrophic lateral sclerosis (ALS) is a complex and rapidly progressive motor neuron disorder with a fatal outcome. Despite the remarkable progress in understanding ALS pathophysiology, which has significantly contributed to clinical trial design, ALS remains a rapidly disabling and life-shortening condition. The non-motor neuron features of ALS, including nutritional status, energy expenditure, and metabolic imbalance, are increasingly gaining attention. Indeed, the bioenergetic failure and mitochondrial dysfunction of patients with ALS impact not only the high energy-demanding motor neurons but also organs and brain areas long considered irrelevant to the disease. As such, here we discuss how considering energy balance in ALS is reshaping research on this disease, opening the path to novel targetable opportunities for its treatment.

Brown Adipose Tissue undergoes pathological perturbations and shapes C2C12 myoblast homeostasis in the SOD1-G93A mouse model of Amyotrophic Lateral Sclerosis

Amyotrophic lateral sclerosis (ALS) is a progressive neurodegenerative disease characterized by the selective loss of motor neurons. The contribution of peripheral organs remains incompletely understood. We focused our attention on brown adipose tissue (BAT) and its secreted extracellular vesicles (EVs) given their role in regulating systemic energy balance. In this study, we employed a multi-omics approach, including RNA sequencing (GEO identifier GSE273052) and proteomics (ProteomeXchange identifier PXD054147), to investigate the alterations in BAT and its EVs in the SOD1-G93A mouse model of ALS. Our results revealed consistent changes in the proteomic and transcriptomic profiles of BAT from SOD1-G93A mice, highlighting alterations such as mitochondrial dysfunction and impaired differentiation capacity. Specifically, primary brown adipocytes (PBAs) from SOD1-G93A mice exhibited differentiation impairment, respiratory defects, and alterations in mitochondrial dynamics. Furthermore, the BAT-derived EVs from SOD1-G93A mice displayed distinct changes in size distribution and cargo content. In parallel, such EVs negatively impacted the differentiation and homeostasis of C2C12 murine myoblasts, as well as induced atrophy in C2C12-derived myotubes. These findings suggest that BAT undergoes pathological perturbations in ALS mouse model and could impact on skeletal muscle homeostasis through the secretion of dysfunctional EVs.

An open-label Phase 2a study to assess the safety and tolerability of trimetazidine in patients with amyotrophic lateral sclerosis

Metabolic imbalance is associated with amyotrophic lateral sclerosis progression. Impaired glucose oxidation and increased reliance on fatty acid oxidation contribute to reduced metabolic flexibility and faster disease progression in amyotrophic lateral sclerosis. We sought to evaluate the safety and tolerability, and explore the pharmacodynamic response of trimetazidine, a partial fatty acid oxidation inhibitor, on oxidative stress markers and energy expenditure in amyotrophic lateral sclerosis. The study was conducted between June 29, 2021 and May 24, 2023. People living with amyotrophic lateral sclerosis, recruited in Australia and the Netherlands, received open-label oral trimetazidine for 12 weeks after an initial 4-week lead-in period. The primary outcome measures were safety and tolerability, as well as the change from baseline in oxidative stress markers malondialdehyde (MDA) and 8-hydroxy-2'-deoxyguanosine (8-OHdG). Secondary outcome measures were change from baseline in energy expenditure, amyotrophic lateral sclerosis functional rating scale-revised, and slow vital capacity (SVC). Linear mixed effects were used to estimate the mean difference in MDA and 8-OHdG between the on- and off-treatment periods. This trial is registered under ClinicalTrial.gov National Clinical Trial (NCT) number NCT04788745 and European Union Drug Regulating Authorities Clinical Trials (EudraCT) number 2020-005018-17. Twenty-one participants received trimetazidine; 19 (90%) completed the treatment period. Trimetazidine was well tolerated; there were 57 adverse events reported, of which 7 (11%) were deemed potentially drug-related, including hot flushes (2), nausea (2), paraesthesia (2) and fatigue (1). MDA was numerically lower during treatment [-0.29 uM; 95% confidence interval (CI) -0.90 to 0.33, P  = 0.36]; 8-OHdG was significantly lower during treatment (-0.12 nM; 95% CI -0.23 to -0.01, P = 0.0245). The decrease in oxidative stress markers was accompanied by a reduction in resting energy expenditure (95 kcal, 95% CI 36.8-154, P = 0.0014). The absence of a placebo group prevented the interpretation of the clinical parameters. Oral trimetazidine was safe and well tolerated among patients with amyotrophic lateral sclerosis. This, combined with the significant reduction in markers of oxidative stress and resting energy expenditure, warrants a larger double-blind placebo-controlled efficacy study.

New insights on pharmacological and therapeutic potentials of trimetazidine beyond anti-anginal drug: A comprehensive review

Trimetazidine (TMZ) is a beneficial and well-tolerable anti-anginal drug which has protective action towards ischemia and reperfusion injury. TMZ performs its anti-ischemic effect by modifying cardiac metabolism without shifting the hemodynamic functions, so it represents an outstanding complementary perspective to the general angina treatment. TMZ possesses a positive impact on the inflammatory profile, and also endothelial function furthermore displays various benefits through minimising the number, as well as the intensity of angina strikes and ameliorating the clinical indication and symptoms of myocardium ischemia. It is administrated as monotherapy along with a combination of different antianginal drugs. Apart from anti-angina action, in recent years TMZ has shown various pharmacological activities such as neuroprotective, renal protective, hepato-protective, cardio-protective effects, and other beneficial pharmacological activities. We select to write the present review article to cover the different pharmacological and therapeutic potentials of TMZ.

Type 2 diabetes mellitus and neurodegenerative disorders: The mitochondrial connection

The incidence of type 2 diabetes mellitus (T2DM) has increased in our society in recent decades as the population ages, and this trend is not expected to revert. This is the same for the incidence of the main neurodegenerative disorders, including the two most common ones, which are, Alzheimer's and Parkinson's disease. Currently, no pharmacological therapies have been developed to revert or cure any of these pathologies. Interestingly, in recent years, an increased number of studies have shown a high co-morbidity between T2DM and neurodegeneration, as well as some common molecular pathways that are affected in both types of diseases. For example, while the etiopathology of T2DM and neurodegenerative disorders is highly complex, mitochondrial dysfunction has been broadly described in the early steps of both diseases; accordingly, this dysfunction has emerged as a plausible molecular link between them. In fact, the prominent role played by mitochondria in the mammalian metabolism of glucose places the physiology of the organelle in a central position to regulate many cellular processes that are affected in both T2DM and neurodegenerative disorders. In this collaborative review, we critically describe the relationship between T2DM and neurodegeneration; making a special emphasis on the mitochondrial mechanisms that could link these diseases. A better understanding of the role of mitochondria on the etiopathology of T2DM and neurodegeneration could pave the way for the development of new pharmacological therapies focused on the regulation of the physiology of the organelle. These therapies could, ultimately, contribute to increase healthspan.

Fasudil attenuates syncytin-1-mediated activation of microglia and impairments of motor neurons and motor function in mice

Amyotrophic lateral sclerosis (ALS) is a devastating neurodegenerative disease. Syncytin-1 (Syn), an envelope glycoprotein encoded by the env gene of the human endogenous retrovirus-W family, has been resorted to be highly expressed in biopsies from the muscles from ALS patients; however, the specific regulatory role of Syn during ALS progression remains uncovered. In this study, C57BL/6 mice were injected with adeno-associated virus-overexpressing Syn, with or without Fasudil administration. The Syn expression was assessed by quantitative real-time polymerase chain reaction and immunohistochemistry analysis. The histological change of anterior tibial muscles was determined by hematoxylin-eosin staining. Qualitative ultrastructural analysis of electron micrographs obtained from lumbar spinal cords was carried out. Serum inflammatory cytokines were assessed by enzyme linked immunosorbent assay (ELISA) assay and motor function was recorded using Basso, Beattie, and Bresnahan (BBB) scoring, climbing test and treadmill running test. Immunofluorescence and western blot assays were conducted to examine microglial- and motor neurons-related proteins. Syn overexpression significantly caused systemic inflammatory response, muscle tissue lesions, and motor dysfunction in mice. Meanwhile, Syn overexpression promoted the impairment of motor neuron, evidenced by the damaged structure of the neurons and reduced expression of microtubule-associated protein 2, HB9, neuronal nuclei and neuron-specific enolase in Syn-induced mice. In addition, Syn overexpression greatly promoted the expression of CD16/CD32 and inducible nitric oxide synthase (M1 phenotype markers), and reduced the expression of CD206 and arginase 1 (M2 phenotype markers). Importantly, the above changes caused by Syn overexpression were partly abolished by Fasudil administration. This study provides evidence that Syn-activated microglia plays a pivotal role during the progression of ALS.

Inflammation in the Peripheral Nervous System after Injury

Nerve injury is a common condition that occurs as a result of trauma, iatrogenic injury, or long-lasting stimulation. Unlike the central nervous system (CNS), the peripheral nervous system (PNS) has a strong capacity for self-repair and regeneration. Peripheral nerve injury results in the degeneration of distal axons and myelin sheaths. Macrophages and Schwann cells (SCs) can phagocytose damaged cells. Wallerian degeneration (WD) makes the whole axon structure degenerate, creating a favorable regenerative environment for new axons. After nerve injury, macrophages, neutrophils and other cells are mobilized and recruited to the injury site to phagocytose necrotic cells and myelin debris. Pro-inflammatory and anti-inflammatory factors involved in the inflammatory response provide a favorable microenvironment for peripheral nerve regeneration and regulate the effects of inflammation on the body through relevant signaling pathways. Previously, inflammation was thought to be detrimental to the body, but further research has shown that appropriate inflammation promotes nerve regeneration, axon regeneration, and myelin formation. On the contrary, excessive inflammation can cause nerve tissue damage and pathological changes, and even lead to neurological diseases. Therefore, after nerve injury, various cells in the body interact with cytokines and chemokines to promote peripheral nerve repair and regeneration by inhibiting the negative effects of inflammation and harnessing the positive effects of inflammation in specific ways and at specific times. Understanding the interaction between neuroinflammation and nerve regeneration provides several therapeutic ideas to improve the inflammatory microenvironment and promote nerve regeneration.

A comparison between bioelectrical impedance analysis and air-displacement plethysmography in assessing fat-free mass in patients with motor neurone diseases: a cross-sectional study

AIM

To determine the validity of bioelectrical impedance analysis (BIA) in quantifying fat-free mass (FFM) compared to air-displacement plethysmography (ADP) in patients with a motor neurone disease (MND).

METHODS

FFM of 140 patients diagnosed with MND was determined by ADP using the BodPod (i.e. the gold standard), and by BIA using the whole-body Bodystat. FFM values were translated to predicted resting energy expenditure (REE); the actual REE was measured using indirect calorimetry, resulting in a metabolic index. Validity of the BIA compared to the ADP was assessed using Bland-Altman analysis and Pearson's r. To assess the clinical relevance of differences, we evaluated changes in metabolic index and in individualized protein demand.

RESULTS

Despite the high correlation between ADP and BIA (r = 0.93), averaged across patients, the assessed mean fat-free mass was 51.7 kg (± 0.9) using ADP and 54.2 kg (± 1.0) using BIA. Hence, BIA overestimated fat-free mass by 2.5 kg (95% CI 1.8-3.2, p < 0.001). Clinically, an increased metabolic index would be more often underdiagnosed in patients with MND using BIA (31.4% according to BIA versus 44.2% according to ADP, p = 0.048). A clinically relevant overestimation of ≥ 15 g in protein demand was observed for 4 (2.9%) patients using BIA.

CONCLUSIONS

BIA systematically overestimates FFM in patients with MND. Although the differences are limited with ADP, underscoring the utility of BIA for research, overestimation of fat-free mass may have consequences for clinical decision-making, especially when interest lies in determining the metabolic index.

Endurance exercise has a negative impact on the onset of SOD1-G93A ALS in female mice and affects the entire skeletal muscle-motor neuron axis

Background

Amyotrophic lateral sclerosis (ALS) is a fatal neuromuscular disease characterized by the degeneration of motor neurons that leads to muscle wasting and atrophy. Epidemiological and experimental evidence suggests a causal relationship between ALS and physical activity (PA). However, the impact of PA on motor neuron loss and sarcopenia is still debated, probably because of the heterogeneity and intensities of the proposed exercises. With this study, we aimed to clarify the effect of intense endurance exercise on the onset and progression of ALS in the SOD1-G93A mouse model.

Methods

We randomly selected four groups of twelve 35-day-old female mice. SOD1-G93A and WT mice underwent intense endurance training on a motorized treadmill for 8 weeks, 5 days a week. During the training, we measured muscle strength, weight, and motor skills and compared them with the corresponding sedentary groups to define the disease onset. At the end of the eighth week, we analyzed the skeletal muscle-motor neuron axis by histological and molecular techniques.

Results

Intense endurance exercise anticipates the onset of the disease by 1 week (age of the onset: trained SOD1-G93A = 63.17 ± 2.25 days old; sedentary SOD1-G93A = 70.75 ± 2.45 days old). In SOD1-G93A mice, intense endurance exercise hastens the muscular switch to a more oxidative phenotype and worsens the denervation process by dismantling neuromuscular junctions in the tibialis anterior, enhancing the Wallerian degeneration in the sciatic nerve, and promoting motor neuron loss in the spinal cord. The training exacerbates neuroinflammation, causing immune cell infiltration in the sciatic nerve and a faster activation of astrocytes and microglia in the spinal cord.

Conclusion

Intense endurance exercise, acting on skeletal muscles, worsens the pathological hallmarks of ALS, such as denervation and neuroinflammation, brings the onset forward, and accelerates the progression of the disease. Our findings show the potentiality of skeletal muscle as a target for both prognostic and therapeutic strategies; the preservation of skeletal muscle health by specific intervention could counteract the dying-back process and protect motor neurons from death. The physiological characteristics and accessibility of skeletal muscle further enhance its appeal as a therapeutic target.

Evaluating the protective role of trimetazidine versus nano-trimetazidine in amelioration of bilateral renal ischemia/reperfusion induced neuro-degeneration: Implications of ERK1/2, JNK and Galectin-3 /NF-κB/TNF-α/HMGB-1 signaling

BACKGROUND

Renal ischemia/reperfusion (I/R) is a primary culprit of acute kidney injury. Neurodegeneration can result from I/R, but the mechanisms are still challenging. We studied the implications of bilateral renal I/R on brain and potential involvement of the oxidative stress (OS) driven extracellular signal-regulated kinase1/2, c-Jun N-terminal kinase (ERK1/2, JNK) and Galectin-3 (Gal-3)/nuclear factor Kappa B (NF-қB)/tumor necrosis factor-alpha (TNF-α), high mobility group box-1 (HMGB-1), and caspase-3 paths upregulation. We tested the impact of Nano-trimetazidine (Nano-TMZ) on these pathways being a target of its neuroprotective effects.

METHODS

Study groups; Sham, I/R, TMZ+I/R, and Nano-TMZ+I/R. Kidney functions, cognition, hippocampal OS markers, Gal-3, NF-қB, p65 and HMGB-1 gene expression, TNF-α level, t-JNK/p-JNK and t-ERK/p-ERK proteins, caspase-3, glial fibrillary acidic protein (GFAP) and ionized calcium binding protein-1 (Iba-1) were assessed.

RESULTS

Nano-TMZ averted renal I/R-induced hippocampal impairment by virtue of its anti: oxidative, inflammatory, and apoptotic properties.

CONCLUSION

Nano-TMZ is more than anti-ischemic.

Anti-inflammatory reprogramming of microglia cells by metabolic modulators to counteract neurodegeneration; a new role for Ranolazine

Microglia chronic activation is a hallmark of several neurodegenerative diseases, including the retinal ones, possibly contributing to their etiopathogenesis. However, some microglia sub-populations have anti-inflammatory and neuroprotective functions, thus making arduous deciphering the role of these cells in neurodegeneration. Since it has been proposed that functionally different microglia subsets also rely on different metabolic routes, we hypothesized that modulating microglia metabolism might be a tool to enhance their anti-inflammatory features. This would have a preventive and therapeutic potential in counteracting neurodegenerative diseases. For this purpose, we tested various molecules known to act on cell metabolism, and we revealed the anti-inflammatory effect of the FDA-approved piperazine derivative Ranolazine on microglia cells, while confirming the one of the flavonoids Quercetin and Naringenin, both in vitro and in vivo. We also demonstrated the synergistic anti-inflammatory effect of Quercetin and Idebenone, and the ability of Ranolazine, Quercetin and Naringenin to counteract the neurotoxic effect of LPS-activated microglia on 661W neuronal cells. Overall, these data suggest that using the selected molecules -also in combination therapies- might represent a valuable approach to reduce inflammation and neurodegeneration while avoiding long term side effects of corticosteroids.

Skeletal muscle in amyotrophic lateral sclerosis

Amyotrophic lateral sclerosis (ALS), the major adult-onset motor neuron disease, has been viewed almost exclusively as a disease of upper and lower motor neurons, with muscle changes interpreted as a consequence of the progressive loss of motor neurons and neuromuscular junctions. This has led to the prevailing view that the involvement of muscle in ALS is only secondary to motor neuron loss. Skeletal muscle and motor neurons reciprocally influence their respective development and constitute a single functional unit. In ALS, multiple studies indicate that skeletal muscle dysfunction might contribute to progressive muscle weakness, as well as to the final demise of neuromuscular junctions and motor neurons. Furthermore, skeletal muscle has been shown to participate in disease pathogenesis of several monogenic diseases closely related to ALS. Here, we move the narrative towards a better appreciation of muscle as a contributor of disease in ALS. We review the various potential roles of skeletal muscle cells in ALS, from passive bystanders to active players in ALS pathophysiology. We also compare ALS to other motor neuron diseases and draw perspectives for future research and treatment.

Nutritional and metabolic factors in amyotrophic lateral sclerosis

Amyotrophic lateral sclerosis (ALS) is a complex neurodegenerative disease that is classically thought to impact the motor system. Over the past 20 years, research has started to consider the contribution of non-motor symptoms and features of the disease, and how they might affect ALS prognosis. Of the non-motor features of the disease, nutritional status (for example, malnutrition) and metabolic balance (for example, weight loss and hypermetabolism) have been consistently shown to contribute to more rapid disease progression and/or earlier death. Several complex cellular changes observed in ALS, including mitochondrial dysfunction, are also starting to be shown to contribute to bioenergetic failure. The resulting energy depletion in high energy demanding neurons makes them sensitive to apoptosis. Given that nutritional and metabolic stressors at the whole-body and cellular level can impact the capacity to maintain optimal function, these factors present avenues through which we can identify novel targets for treatment in ALS. Several clinical trials are now underway evaluating the effectiveness of modifying energy balance in ALS, making this article timely in reviewing the evidence base for metabolic and nutritional interventions.

Neuroprotective potential of trimetazidine against tramadol-induced neurotoxicity: role of PI3K/Akt/mTOR signaling pathways

Tramadol (TRA) causes neurotoxicity whereas trimetazidine (TMZ) is neuroprotective. The potential involvement of the PI3K/Akt/mTOR signaling pathway in the neuroprotection of TMZ against TRA-induced neurotoxicity was evaluated. Seventy male Wistar rats were divided into groups. Groups 1 and 2 received saline or TRA (50 mg/kg). Groups 3, 4, and 5 received TRA (50 mg/kg) and TMZ (40, 80, or 160 mg/kg) for 14 days. Group 6 received TMZ (160 mg/kg). Hippocampal neurodegenerative, mitochondrial quadruple complex enzymes, phosphatidylinositol-3-kinases (PI3Ks)/protein kinase B levels, oxidative stress, inflammatory, apoptosis, autophagy, and histopathology were evaluated. TMZ decreased anxiety and depressive-like behavior induced by TRA. TMZ in tramadol-treated animals inhibited lipid peroxidation, GSSG, TNF-α, and IL-1β while increasing GSH, SOD, GPx, GR, and mitochondrial quadruple complex enzymes in the hippocampus. TRA inhibited Glial fibrillary acidic protein expression and increased pyruvate dehydrogenase levels. TMZ reduced these changes. TRA decreased the level of JNK and increased Beclin-1 and Bax. TMZ decreased phosphorylated Bcl-2 while increasing the unphosphorylated form in tramadol-treated rats. TMZ activated phosphorylated PI3Ks, Akt, and mTOR proteins. TMZ inhibited tramadol-induced neurotoxicity by modulating the PI3K/Akt/mTOR signaling pathways and its downstream inflammatory, apoptosis, and autophagy-related cascades.

The positive impact on translational research of Fondazione italiana di ricerca per la Sclerosi Laterale Amiotrofica (AriSLA), a non-profit foundation focused on amyotrophic lateral sclerosis. Convergence of ex-ante evaluation and ex-post outcomes when goals are set upfront

Charities investing on rare disease research greatly contribute to generate ground-breaking knowledge with the clear goal of finding a cure for their condition of interest. Although the amount of their investments may be relatively small compared to major funders, the advocacy groups' clear mission promotes innovative research and aggregates highly motivated and mission-oriented scientists. Here, we illustrate the case of Fondazione italiana di ricerca per la Sclerosi Laterale Amiotrofica (AriSLA), the main Italian funding agency entirely dedicated to amyotrophic lateral sclerosis research. An international benchmark analysis of publications derived from AriSLA-funded projects indicated that their mean relative citation ratio values (iCite dashboard, National Institutes of Health, U.S.) were very high, suggesting a strong influence on the referring international scientific community. An interesting trend of research toward translation based on the "triangle of biomedicine" and paper citations (iCite) was also observed. Qualitative analysis on researchers' accomplishments was convergent with the bibliometric data, indicating a high level of performance of several working groups, lines of research that speak of progression toward clinical translation, and one study that has progressed from the investigation of cellular mechanisms to a Phase 2 international clinical trial. The key elements of the success of the AriSLA investment lie in: (i) the clear definition of the objectives (research with potential impact on patients, no matter how far), (ii) a rigorous peer-review process entrusted to an international panel of experts, (iii) diversification of the portfolio with ad hoc selection criteria, which also contributed to bringing new experts and younger scientists to the field, and (iv) a close interaction of AriSLA stakeholders with scientists, who developed a strong sense of belonging. Periodic review of the portfolio of investments is a vital practice for funding agencies. Sharing information between funding agencies about their own policies and research assessment methods and outcomes help guide the international debate on funding strategies and research directions to be undertaken, particularly in the field of rare diseases, where synergy is a relevant enabling factor.

Altered Metabolism in Motor Neuron Diseases: Mechanism and Potential Therapeutic Target

Motor Neuron Diseases (MND) are neurological disorders characterized by a loss of varying motor neurons resulting in decreased physical capabilities. Current research is focused on hindering disease progression by determining causes of motor neuron death. Metabolic malfunction has been proposed as a promising topic when targeting motor neuron loss. Alterations in metabolism have also been noted at the neuromuscular junction (NMJ) and skeletal muscle tissue, emphasizing the importance of a cohesive system. Finding metabolism changes consistent throughout both neurons and skeletal muscle tissue could pose as a target for therapeutic intervention. This review will focus on metabolic deficits reported in MNDs and propose potential therapeutic targets for future intervention.

Loss of hypothalamic MCH decreases food intake in amyotrophic lateral sclerosis

Amyotrophic lateral sclerosis (ALS) is associated with impaired energy metabolism, including weight loss and decreased appetite which are negatively correlated with survival. Neural mechanisms underlying metabolic impairment in ALS remain unknown. ALS patients and presymptomatic gene carriers have early hypothalamic atrophy. The lateral hypothalamic area (LHA) controls metabolic homeostasis through the secretion of neuropeptides such as orexin/hypocretin and melanin-concentrating hormone (MCH). Here, we show loss of MCH-positive neurons in three mouse models of ALS based on SOD1 or FUS mutations. Supplementation with MCH (1.2 µg/d) through continuous intracerebroventricular delivery led to weight gain in male mutant Sod1^G86R mice. MCH supplementation increased food intake, rescued expression of the key appetite-related neuropeptide AgRP (agouti-related protein) and modified respiratory exchange ratio, suggesting increased carbohydrate usage during the inactive phase. Importantly, we document pTDP-43 pathology and neurodegeneration in the LHA of sporadic ALS patients. Neuronal cell loss was associated with pTDP-43-positive inclusions and signs of neurodegeneration in MCH-positive neurons. These results suggest that hypothalamic MCH is lost in ALS and contributes to the metabolic changes, including weight loss and decreased appetite.

Emerging clinical investigational drugs for the treatment of amyotrophic lateral sclerosis

INTRODUCTION

Amyotrophic lateral sclerosis (ALS) is a neurodegenerative disorder caused by motoneuron death with a median survival time of 3-5 years since disease onset. There are no effective treatments to date. However, a variety of innovative investigational drugs and biological-based therapies are under clinical development.

AREAS COVERED

This review provides an overview of the clinical investigational small molecules as well as a brief summary of the biological-based therapies that are currently undergoing clinical trials for the treatment of ALS. All the data were obtained from ClinicalTrials.gov (registered through November 1).

EXPERT OPINION

Drug discovery for ALS is an active and evolving field, where many investigational clinical drugs are in different trials. There are several mechanisms of action supporting all these new therapies, although proteostasis is gaining stage. Probably, small orally bioavailable molecules able to recover functional TDP-43 homeostasis may have solid chances to modify ALS progression.

Honokiol alleviated neurodegeneration by reducing oxidative stress and improving mitochondrial function in mutant SOD1 cellular and mouse models of amyotrophic lateral sclerosis

Amyotrophic lateral sclerosis (ALS) is a progressive neurodegenerative disease affecting both upper and lower motor neurons (MNs) with large unmet medical needs. Multiple pathological mechanisms are considered to contribute to the progression of ALS, including neuronal oxidative stress and mitochondrial dysfunction. Honokiol (HNK) has been reported to exert therapeutic effects in several neurologic disease models including ischemia stroke, Alzheimer's disease and Parkinson's disease. Here we found that honokiol also exhibited protective effects in ALS disease models both in vitro and in vivo. Honokiol improved the viability of NSC-34 motor neuron-like cells that expressed the mutant G93A SOD1 proteins (SOD1-G93A cells for short). Mechanistical studies revealed that honokiol alleviated cellular oxidative stress by enhancing glutathione (GSH) synthesis and activating the nuclear factor erythroid 2-related factor 2 (NRF2)-antioxidant response element (ARE) pathway. Also, honokiol improved both mitochondrial function and morphology via fine-tuning mitochondrial dynamics in SOD1-G93A cells. Importantly, honokiol extended the lifespan of the SOD1-G93A transgenic mice and improved the motor function. The improvement of antioxidant capacity and mitochondrial function was further confirmed in the spinal cord and gastrocnemius muscle in mice. Overall, honokiol showed promising preclinical potential as a multiple target drug for ALS treatment.

Pattern of Mitochondrial Respiration in Peripheral Blood Cells of Patients with Parkinson's Disease

Mitochondria are central in the pathogenesis of Parkinson’s disease (PD), as they are involved in oxidative stress, synaptopathy, and other immunometabolic pathways. Accordingly, they are emerging as a potential neuroprotection target, although further human-based evidence is needed for therapeutic advancements. This study aims to shape the pattern of mitochondrial respiration in the blood leukocytes of PD patients in relation to both clinical features and the profile of cerebrospinal fluid (CSF) biomarkers of neurodegeneration. Mitochondrial respirometry on the peripheral blood mononucleate cells (PBMCs) of 16 PD patients and 14 controls was conducted using Seahorse Bioscience technology. Bioenergetic parameters were correlated either with standard clinical scores for motor and non-motor disturbances or with CSF levels of α-synuclein, amyloid-β peptides, and tau proteins. In PD, PBMC mitochondrial basal respiration was normal; maximal and spare respiratory capacities were both increased; and ATP production was higher, although not significantly. Maximal and spare respiratory capacity was directly correlated with disease duration, MDS-UPDRS part III and Hoehn and Yahr motor scores; spare respiratory capacity was correlated with the CSF amyloid-β-42 to amyloid-β-42/40 ratio. We provided preliminary evidence showing that mitochondrial respiratory activity increases in the PBMCs of PD patients, probably following the compensatory adaptations to disease progression, in contrast to the bases of the neuropathological substrate.

Altered TDP-43 Structure and Function: Key Insights into Aberrant RNA, Mitochondrial, and Cellular and Systemic Metabolism in Amyotrophic Lateral Sclerosis

Amyotrophic lateral sclerosis (ALS) is a progressive and fatal neuromuscular disorder with no cure available and limited treatment options. ALS is a highly heterogeneous disease, whereby patients present with vastly different phenotypes. Despite this heterogeneity, over 97% of patients will exhibit pathological TAR-DNA binding protein-43 (TDP-43) cytoplasmic inclusions. TDP-43 is a ubiquitously expressed RNA binding protein with the capacity to bind over 6000 RNA and DNA targets—particularly those involved in RNA, mitochondrial, and lipid metabolism. Here, we review the unique structure and function of TDP-43 and its role in affecting the aforementioned metabolic processes in ALS. Considering evidence published specifically in TDP-43-relevant in vitro, in vivo, and ex vivo models we posit that TDP-43 acts in a positive feedback loop with mRNA transcription/translation, stress granules, cytoplasmic aggregates, and mitochondrial proteins causing a relentless cycle of disease-like pathology eventuating in neuronal toxicity. Given its undeniable presence in ALS pathology, TDP-43 presents as a promising target for mechanistic disease modelling and future therapeutic investigations.

Ranolazine Counteracts Strength Impairment and Oxidative Stress in Aged Sarcopenic Mice

Sarcopenia is defined as the loss of muscle mass associated with reduced strength leading to poor quality of life in elderly people. The decline of skeletal muscle performance is characterized by bioenergetic impairment and severe oxidative stress, and does not always strictly correlate with muscle mass loss. We chose to investigate the ability of the metabolic modulator Ranolazine to counteract skeletal muscle dysfunctions that occur with aging. For this purpose, we treated aged C57BL/6 mice with Ranolazine/vehicle for 14 days and collected the tibialis anterior and gastrocnemius muscles for histological and gene expression analyses, respectively. We found that Ranolazine treatment significantly increased the muscle strength of aged mice. At the histological level, we found an increase in centrally nucleated fibers associated with an up-regulation of genes encoding MyoD, Periostin and Osteopontin, thus suggesting a remodeling of the muscle even in the absence of physical exercise. Notably, these beneficial effects of Ranolazine were also accompanied by an up-regulation of antioxidant and mitochondrial genes as well as of NADH-dehydrogenase activity, together with a more efficient protection from oxidative damage in the skeletal muscle. These data indicate that the protection of muscle from oxidative stress by Ranolazine might represent a valuable approach to increase skeletal muscle strength in elderly populations.

Advance in the Diagnostics and Management of Musculoskeletal Diseases

Musculoskeletal disorders are a broad spectrum of diseases, affecting muscles, bones, ligaments, and tendons worldwide [...].

Alteration of the Neuromuscular Junction and Modifications of Muscle Metabolism in Response to Neuron-Restricted Expression of the CHMP2Bintron5 Mutant in a Mouse Model of ALS-FTD Syndrome

CHMP2B is a protein that coordinates membrane scission events as a core component of the ESCRT machinery. Mutations in CHMP2B are an uncommon cause of amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD), two neurodegenerative diseases with clinical, genetic, and pathological overlap. Different mutations have now been identified across the ALS-FTD spectrum. Disruption of the neuromuscular junction is an early pathogenic event in ALS. Currently, the links between neuromuscular junction functionality and ALS-associated genes, such as CHMP2B, remain poorly understood. We have previously shown that CHMP2B transgenic mice expressing the CHMP2B^intron5 mutant specifically in neurons develop a progressive motor phenotype reminiscent of ALS. In this study, we used complementary approaches (behavior, histology, electroneuromyography, and biochemistry) to determine the extent to which neuron-specific expression of CHMP2B^intron5 could impact the skeletal muscle characteristics. We show that neuronal expression of the CHMP2B^intron5 mutant is sufficient to trigger progressive gait impairment associated with structural and functional changes in the neuromuscular junction. Indeed, CHMP2B^intron5 alters the pre-synaptic terminal organization and the synaptic transmission that ultimately lead to a switch of fast-twitch glycolytic muscle fibers to more oxidative slow-twitch muscle fibers. Taken together these data indicate that neuronal expression of CHMP2B^intron5 is sufficient to induce a synaptopathy with molecular and functional changes in the motor unit reminiscent of those found in ALS patients.

Mechanistic Insights of Mitochondrial Dysfunction in Amyotrophic Lateral Sclerosis: An Update on a Lasting Relationship

Amyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative disease characterized by progressive loss of the upper and lower motor neurons. Despite the increasing effort in understanding the etiopathology of ALS, it still remains an obscure disease, and no therapies are currently available to halt its progression. Following the discovery of the first gene associated with familial forms of ALS, Cu–Zn superoxide dismutase, it appeared evident that mitochondria were key elements in the onset of the pathology. However, as more and more ALS-related genes were discovered, the attention shifted from mitochondria impairment to other biological functions such as protein aggregation and RNA metabolism. In recent years, mitochondria have again earned central, mechanistic roles in the pathology, due to accumulating evidence of their derangement in ALS animal models and patients, often resulting in the dysregulation of the energetic metabolism. In this review, we first provide an update of the last lustrum on the molecular mechanisms by which the most well-known ALS-related proteins affect mitochondrial functions and cellular bioenergetics. Next, we focus on evidence gathered from human specimens and advance the concept of a cellular-specific mitochondrial “metabolic threshold”, which may appear pivotal in ALS pathogenesis.

Therapeutic Targets in Amyotrophic Lateral Sclerosis: Focus on Ion Channels and Skeletal Muscle

Amyotrophic Lateral Sclerosis is a neurodegenerative disease caused by progressive loss of motor neurons, which severely compromises skeletal muscle function. Evidence shows that muscle may act as a molecular powerhouse, whose final signals generate in patients a progressive loss of voluntary muscle function and weakness leading to paralysis. This pathology is the result of a complex cascade of events that involves a crosstalk among motor neurons, glia, and muscles, and evolves through the action of converging toxic mechanisms. In fact, mitochondrial dysfunction, which leads to oxidative stress, is one of the mechanisms causing cell death. It is a common denominator for the two existing forms of the disease: sporadic and familial. Other factors include excitotoxicity, inflammation, and protein aggregation. Currently, there are limited cures. The only approved drug for therapy is riluzole, that modestly prolongs survival, with edaravone now waiting for new clinical trial aimed to clarify its efficacy. Thus, there is a need of effective treatments to reverse the damage in this devastating pathology. Many drugs have been already tested in clinical trials and are currently under investigation. This review summarizes the already tested drugs aimed at restoring muscle-nerve cross-talk and on new treatment options targeting this tissue.