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1.
Mol Med ; 30(1): 80, 2024 Jun 10.
Article in English | MEDLINE | ID: mdl-38858657

ABSTRACT

BACKGROUND: Type 2 diabetes mellitus (T2DM) is a chronic metabolic disease that commonly results from a high-calorie diet and sedentary lifestyle, leading to insulin resistance and glucose homeostasis perturbation. Physical activity is recommended as one first-line treatment in T2DM, but it leads to contrasted results. We hypothesized that, instead of applying standard exercise protocols, the prescription of personalized exercise programs specifically designed to reverse the potential metabolic alterations in skeletal muscle could result in better results. METHODS: To test this hypothesis, we drew the metabolic signature of the fast-twitch quadriceps muscle, based on a combined unbiased NMR spectroscopy and RT-qPCR study, in several T2DM mouse models of different genetic background (129S1/SvImJ, C57Bl/6J), sex and aetiology (high-fat diet (HFD) or HFD/Streptozotocin (STZ) induction or transgenic MKR (FVB-Tg Ckm-IGF1R*K1003R)1Dlr/J) mice. Three selected mouse models with unique muscular metabolic signatures were submitted to three different swimming-based programs, designed to address each metabolic specificity. RESULTS: We found that depending on the genetic background, the sex, and the mode of T2DM induction, specific muscular adaptations occurred, including depressed glycolysis associated with elevated PDK4 expression, shift to ß-oxidation, or deregulation of amino-acid homeostasis. Interestingly, dedicated swimming-based exercises designed to restore specific metabolic alterations in muscle were found optimal in improving systemic T2DM hallmarks, including a significant reduction in insulin resistance, the improvement of glucose homeostasis, and a delay in sensorimotor function alterations. CONCLUSION: The muscle metabolism constitutes an important clue for the design of precision exercises with potential clinical implications for T2DM patients.


Subject(s)
Diabetes Mellitus, Type 2 , Disease Models, Animal , Muscle, Skeletal , Physical Conditioning, Animal , Animals , Diabetes Mellitus, Type 2/metabolism , Diabetes Mellitus, Type 2/therapy , Diabetes Mellitus, Type 2/genetics , Muscle, Skeletal/metabolism , Mice , Male , Female , Diet, High-Fat/adverse effects , Mice, Inbred C57BL , Insulin Resistance , Metabolome , Diabetes Mellitus, Experimental/metabolism , Diabetes Mellitus, Experimental/therapy , Mice, Transgenic , Metabolomics/methods
2.
Front Cell Neurosci ; 17: 1242828, 2023.
Article in English | MEDLINE | ID: mdl-37780204

ABSTRACT

Introduction: Spinal muscular atrophy (SMA) is a fatal neurodegenerative disorder, characterized by motor neuron (MN) degeneration and severe muscular atrophy and caused by Survival of Motor Neuron (SMN) depletion. Therapies aimed at increasing SMN in patients have proven their efficiency in alleviating SMA symptoms but not for all patients. Thus, combinational therapies are warranted. Here, we investigated the involvement of NADPH oxidase 4 (NOX4) in SMA-induced spinal MN death and if the modulation of Nox4 activity could be beneficial for SMA patients. Methods: We analysed in the spinal cord of severe type SMA-like mice before and at the disease onset, the level of oxidative stress and Nox4 expression. Then, we tested the effect of Nox4 inhibition by GKT137831/Setanaxib, a drug presently in clinical development, by intrathecal injection on MN survival and motor behaviour. Finally, we tested if GKT137831/Setanaxib could act synergistically with FDA-validated SMN-upregulating treatment (nusinersen). Results: We show that NOX4 is overexpressed in SMA and its inhibition by GKT137831/Setanaxib protected spinal MN from SMA-induced degeneration. These improvements were associated with a significant increase in lifespan and motor behaviour of the mice. At the molecular level, GKT137831 activated the pro-survival AKT/CREB signaling pathway, leading to an increase in SMN expression in SMA MNs. Most importantly, we found that the per os administration of GKT137831 acted synergistically with a FDA-validated SMN-upregulating treatment. Conclusion: The pharmacological inhibition of NOX4 by GKT137831/Setanaxib is neuroprotector and could represent a complementary therapeutic strategy to fight against SMA.

3.
Neuropathol Appl Neurobiol ; 48(5): e12816, 2022 08.
Article in English | MEDLINE | ID: mdl-35338505

ABSTRACT

AIM: Spinal muscular atrophy (SMA) is a neuromuscular disease caused by survival of motor neuron (SMN) deficiency that induces motor neuron (MN) degeneration and severe muscular atrophy. Gene therapies that increase SMN have proven their efficacy but not for all patients. Here, we explored the unfolded protein response (UPR) status in SMA pathology and explored whether UPR modulation could be beneficial for SMA patients. METHODS: We analysed the expression and activation of key UPR proteins by RT-qPCR and by western blots in SMA patient iPSC-derived MNs and one SMA cell line in which SMN expression was re-established (rescue). We complemented this approach by using myoblast and fibroblast SMA patient cells and SMA mouse models of varying severities. Finally, we tested in vitro and in vivo the effect of IRE1α/XBP1 pathway restoration on SMN expression and subsequent neuroprotection. RESULTS: We report that the IRE1α/XBP1 branch of the unfolded protein response is disrupted in SMA, with a depletion of XBP1s irrespective of IRE1α activation pattern. The overexpression of XBP1s in SMA fibroblasts proved to transcriptionally enhance SMN expression. Importantly, rebalancing XBP1s expression in severe SMA-like mice, induced SMN expression and spinal MN protection. CONCLUSIONS: We have identified XBP1s depletion as a contributing factor in SMA pathogenesis, and the modulation of this transcription factor proves to be a plausible therapeutic avenue in the context of pharmacological interventions for patients.


Subject(s)
Activating Transcription Factor 6 , Endoribonucleases , Muscular Atrophy, Spinal , Protein Serine-Threonine Kinases , Survival of Motor Neuron 1 Protein , X-Box Binding Protein 1 , Activating Transcription Factor 6/genetics , Activating Transcription Factor 6/metabolism , Animals , Cell Line , Disease Models, Animal , Endoribonucleases/genetics , Endoribonucleases/metabolism , Humans , Mice , Motor Neurons/pathology , Muscular Atrophy, Spinal/genetics , Muscular Atrophy, Spinal/metabolism , Muscular Atrophy, Spinal/pathology , Protein Serine-Threonine Kinases/genetics , Protein Serine-Threonine Kinases/metabolism , Survival of Motor Neuron 1 Protein/genetics , Survival of Motor Neuron 1 Protein/metabolism , X-Box Binding Protein 1/genetics , X-Box Binding Protein 1/metabolism
4.
Front Endocrinol (Lausanne) ; 12: 739287, 2021.
Article in English | MEDLINE | ID: mdl-34690932

ABSTRACT

Background: Obesity is a major public health problem of our time as a risk factor for cardiometabolic disease and the available pharmacological tools needed to tackle the obesity pandemic are insufficient. Neurotensin (NTS) is a 13 amino acid peptide, which is derived from a larger precursor hormone called proneurotensin or Long Form NTS (LF NTS). NTS modulates neuro-transmitter release in the central system nervous, and facilitates intestinal fat absorption in the gastrointestinal tract. Mice lacking LF NTS are protected from high fat diet (HFD) induced obesity, hepatic steatosis and glucose intolerance. In humans, increased levels of LF NTS strongly and independently predict the development of obesity, diabetes mellitus, cardiovascular disease and mortality. With the perspective to develop therapeutic tools to neutralize LF NTS, we developed a monoclonal antibody, specifically inhibiting the function of the LF NTS (LF NTS mAb). This antibody was tested for the effects on body weight, metabolic parameters and behavior in mice made obese by high-fat diet. Methods: C57bl/6j mice were subjected to high-fat diet (HFD) until they reached an obesity state, then food was switched to chow. Mice were treated with either PBS (control therapy) or LF NTS mAb at the dose of 5 mg/kg once a week (i.v.). Mice weight, plasma biochemical analysis, fat and muscle size and distribution and behavioral tests were performed during the losing weight period and the stabilization period. Results: Obese mice treated with the LF NTS mAb lost weight significantly faster than the control treated group. LF NTS mAb treatment also resulted in smaller fat depots, increased fecal cholesterol excretion, reduced liver fat and larger muscle fiber size. Moreover, mice on active therapy were also less stressed, more curious and more active, providing a possible explanation to their weight loss. Conclusion: Our results demonstrate that in mice subjected to HFD-induced obesity, a blockade of LF NTS with a monoclonal antibody results in reduced body weight, adipocyte volume and increased muscle fiber size, possibly explained by beneficial effects on behavior. The underlying mechanisms as well as any future role of LF NTS mAb as an anti-obesity agent warrants further studies.


Subject(s)
Antibodies, Monoclonal/pharmacology , Behavior, Animal/drug effects , Diet, High-Fat/adverse effects , Neurotensin/immunology , Obesity/drug therapy , Weight Loss/drug effects , Adipose Tissue/drug effects , Adipose Tissue/metabolism , Animals , Anti-Obesity Agents/pharmacology , Anti-Obesity Agents/therapeutic use , Antibodies, Monoclonal/therapeutic use , Male , Mice , Muscle, Skeletal/drug effects , Muscle, Skeletal/metabolism , Obesity/etiology , Obesity/metabolism
5.
Int J Mol Sci ; 22(9)2021 Apr 27.
Article in English | MEDLINE | ID: mdl-33925507

ABSTRACT

Physical exercise improves motor control and related cognitive abilities and reinforces neuroprotective mechanisms in the nervous system. As peripheral nerves interact with skeletal muscles at the neuromuscular junction, modifications of this bidirectional communication by physical activity are positive to preserve this synapse as it increases quantal content and resistance to fatigue, acetylcholine receptors expansion, and myocytes' fast-to-slow functional transition. Here, we provide the intermediate step between physical activity and functional and morphological changes by analyzing the molecular adaptations in the skeletal muscle of the full BDNF/TrkB downstream signaling pathway, directly involved in acetylcholine release and synapse maintenance. After 45 days of training at different intensities, the BDNF/TrkB molecular phenotype of trained muscles from male B6SJLF1/J mice undergo a fast-to-slow transition without affecting motor neuron size. We provide further knowledge to understand how exercise induces muscle molecular adaptations towards a slower phenotype, resistant to prolonged trains of stimulation or activity that can be useful as therapeutic tools.


Subject(s)
Brain-Derived Neurotrophic Factor/metabolism , Membrane Glycoproteins/metabolism , Neuromuscular Junction/metabolism , Protein-Tyrosine Kinases/metabolism , Running/physiology , Swimming/physiology , Animals , Male , Mice, Inbred Strains , Motor Neurons/metabolism , Munc18 Proteins/metabolism , Muscle, Skeletal/physiology , Nerve Growth Factors/metabolism , Physical Conditioning, Animal/physiology , Protein Serine-Threonine Kinases/metabolism , Signal Transduction , Synaptic Vesicles/metabolism , Synaptosomal-Associated Protein 25/metabolism
6.
Cell Mol Life Sci ; 77(15): 3027-3040, 2020 Aug.
Article in English | MEDLINE | ID: mdl-31646358

ABSTRACT

Nerve-induced muscle contraction regulates the BDNF/TrkB neurotrophic signalling to retrogradely modulate neurotransmission and protect the neuromuscular junctions and motoneurons. In muscles with amyotrophic lateral sclerosis, this pathway is strongly misbalanced and neuromuscular junctions are destabilized, which may directly cause the motoneuron degeneration and muscular atrophy observed in this disease. Here, we sought to demonstrate (1) that physical exercise, whose recommendation has been controversial in amyotrophic lateral sclerosis, would be a good option for its therapy, because it normalizes and improves the altered neurotrophin pathway and (2) a plausible molecular mechanism underlying its positive effect. SOD1-G93A mice were trained following either running or swimming-based protocols since the beginning of the symptomatic phase (day 70 of age) until day 115. Next, the full BDNF pathway, including receptors, downstream kinases and proteins related with neurotransmission, was characterized and motoneuron survival was analysed. The results establish that amyotrophic lateral sclerosis-induced damaging molecular changes in the BDNF/TrkB pathway are reduced, prevented or even overcompensated by precisely defined exercise protocols that modulate TrkB isoforms and neurotransmission regulatory proteins and reduce motoneuron death. Altogether, the maintenance of the BDNF/TrkB signalling and the downstream pathway, particularly after the swimming protocol, adds new molecular evidence of the benefits of physical exercise to reduce the impact of amyotrophic lateral sclerosis. These results are encouraging since they reveal an improvement even starting the therapy after the onset of the disease.


Subject(s)
Amyotrophic Lateral Sclerosis/pathology , Neuromuscular Junction/metabolism , Physical Conditioning, Animal , Signal Transduction , Swimming , Amyotrophic Lateral Sclerosis/metabolism , Animals , Brain-Derived Neurotrophic Factor/metabolism , Disease Models, Animal , Female , Male , Membrane Glycoproteins/metabolism , Mice , Mice, Transgenic , Motor Neurons/metabolism , Muscle, Skeletal/metabolism , Polymorphism, Single Nucleotide , Protein Isoforms/metabolism , Protein Kinase C-alpha/metabolism , Protein-Tyrosine Kinases/metabolism , SNARE Proteins/metabolism , Superoxide Dismutase-1/genetics , Superoxide Dismutase-1/metabolism
7.
Front Physiol ; 10: 1258, 2019.
Article in English | MEDLINE | ID: mdl-31632295

ABSTRACT

Spinal Muscular Atrophy (SMA), an autosomal recessive neurodegenerative disease characterized by the loss of spinal-cord motor-neurons, is caused by mutations on Survival-of-Motor Neuron (SMN)-1 gene. The expression of SMN2, a SMN1 gene copy, partially compensates for SMN1 disruption due to exon-7 excision in 90% of transcripts subsequently explaining the strong clinical heterogeneity. Several alterations in energy metabolism, like glucose intolerance and hyperlipidemia, have been reported in SMA at both systemic and cellular level, prompting questions about the potential role of energy homeostasis and/or production involvement in disease progression. In this context, we have recently reported the tolerance of mild SMA-like mice (SmnΔ7/Δ7; huSMN2 +/+) to 10 months of low-intensity running or high-intensity swimming exercise programs, respectively involving aerobic and a mix aerobic/anaerobic muscular metabolic pathways. Here, we investigated whether those exercise-induced benefits were associated with an improvement in metabolic status in mild SMA-like mice. We showed that untrained SMA-like mice exhibited a dysregulation of lipid metabolism with an enhancement of lipogenesis and adipocyte deposits when compared to control mice. Moreover, they displayed a high oxygen consumption and energy expenditure through ß-oxidation increase yet for the same levels of spontaneous activity. Interestingly, both exercises significantly improved lipid metabolism and glucose homeostasis in SMA-like mice, and enhanced oxygen consumption efficiency with the maintenance of a high oxygen consumption for higher levels of spontaneous activity. Surprisingly, more significant effects were obtained with the high-intensity swimming protocol with the maintenance of high lipid oxidation. Finally, when combining electron microscopy, respiratory chain complexes expression and enzymatic activity measurements in muscle mitochondria, we found that (1) a muscle-specific decreased in enzymatic activity of respiratory chain I, II, and IV complexes for equal amount of mitochondria and complexes expression and (2) a significant decline in mitochondrial maximal oxygen consumption, were reduced by both exercise programs. Most of the beneficial effects were obtained with the high-intensity swimming protocol. Taking together, our data support the hypothesis that active physical exercise, including high-intensity protocols, induces metabolic adaptations at both systemic and cellular levels, providing further evidence for its use in association with SMN-overexpressing therapies, in the long-term care of SMA patients.

8.
Mol Neurobiol ; 56(10): 6856-6872, 2019 Oct.
Article in English | MEDLINE | ID: mdl-30929165

ABSTRACT

Amyotrophic lateral sclerosis (ALS) is a chronic neurodegenerative disease characterized by progressive motor weakness. It is accepted that it is caused by motoneuron degeneration leading to a decrease in muscle stimulation. However, ALS is being redefined as a distal axonopathy, in that neuromuscular junction dysfunction precedes and may even influence motoneuron loss. In this synapse, several metabotropic receptor-mediated signaling pathways converge on effector kinases that phosphorylate targets that are crucial for synaptic stability and neurotransmission quality. We have previously shown that, in physiological conditions, nerve-induced muscle contraction regulates the brain-derived neurotrophic factor/tropomyosin-related kinase B (BDNF/TrkB) signaling to retrogradely modulate presynaptic protein kinases PKC and PKA, which are directly involved in the modulation of acetylcholine release. In ALS patients, the alteration of this signaling may significantly contribute to a motor impairment. Here, we investigate whether BDNF/TrkB signaling, the downstream PKC (cPKCßI, cPKCα, and nPKCε isoforms), and PKA (regulatory and catalytic subunits) and some SNARE/SM exocytotic machinery proteins (Munc18-1 and SNAP-25) are altered in the skeletal muscle of pre- and symptomatic SOD1-G93A mice. We found that this pathway is strongly affected in symptomatic ALS mice muscles including an unbalance between (I) BDNF and TrkB isoforms, (II) PKC isoforms and PKA subunits, and (III) Munc18-1 and SNAP-25 phosphorylation ratios. Changes in TrkB.T1 and cPKCßI are precociously observed in presymptomatic mice. Altogether, several of these molecular alterations can be partly associated with the known fast-to-slow motor unit transition during the disease process but others can be related with the initial disease pathogenesis.


Subject(s)
Amyotrophic Lateral Sclerosis/pathology , Brain-Derived Neurotrophic Factor/metabolism , Neuromuscular Junction/pathology , Protein Serine-Threonine Kinases/metabolism , SNARE Proteins/metabolism , Signal Transduction , Superoxide Dismutase-1/genetics , Amyotrophic Lateral Sclerosis/metabolism , Animals , Catalytic Domain , Disease Models, Animal , Male , Mice, Transgenic , Models, Biological , Motor Neurons/metabolism , Motor Neurons/pathology , Muscles/metabolism , Muscles/pathology , Nerve Growth Factors/metabolism , Neuromuscular Junction/metabolism , Receptors, Nerve Growth Factor/metabolism , Spinal Cord/pathology
9.
Sci Rep ; 8(1): 2075, 2018 02 01.
Article in English | MEDLINE | ID: mdl-29391529

ABSTRACT

The hereditary neurodegenerative disorder spinal muscular atrophy (SMA) is characterized by the loss of spinal cord motor neurons and skeletal muscle atrophy. SMA is caused by mutations of the survival motor neuron (SMN) gene leading to a decrease in SMN protein levels. The SMN deficiency alters nuclear body formation and whether it can contribute to the disease remains unclear. Here we screen a series of small-molecules on SMA patient fibroblasts and identify flunarizine that accumulates SMN into Cajal bodies, the nuclear bodies important for the spliceosomal small nuclear RNA (snRNA)-ribonucleoprotein biogenesis. Using histochemistry, real-time RT-PCR and behavioural analyses in a mouse model of SMA, we show that along with the accumulation of SMN into Cajal bodies of spinal cord motor neurons, flunarizine treatment modulates the relative abundance of specific spliceosomal snRNAs in a tissue-dependent manner and can improve the synaptic connections and survival of spinal cord motor neurons. The treatment also protects skeletal muscles from cell death and atrophy, raises the neuromuscular junction maturation and prolongs life span by as much as 40 percent (p < 0.001). Our findings provide a functional link between flunarizine and SMA pathology, highlighting the potential benefits of flunarizine in a novel therapeutic perspective against neurodegenerative diseases.


Subject(s)
Coiled Bodies/drug effects , Flunarizine/pharmacology , Muscular Atrophy, Spinal/metabolism , Survival of Motor Neuron 1 Protein/metabolism , Animals , Cell Line , Coiled Bodies/metabolism , Female , Fibroblasts/drug effects , Fibroblasts/metabolism , Flunarizine/therapeutic use , HeLa Cells , Humans , Male , Mice , Muscle, Skeletal/drug effects , Muscle, Skeletal/metabolism , Muscular Atrophy, Spinal/drug therapy , Small Molecule Libraries/pharmacology
10.
Front Mol Neurosci ; 10: 332, 2017.
Article in English | MEDLINE | ID: mdl-29104532

ABSTRACT

Amyotrophic Lateral Sclerosis is an adult-onset neurodegenerative disease characterized by the specific loss of motor neurons, leading to muscle paralysis and death. Although the cellular mechanisms underlying amyotrophic lateral sclerosis (ALS)-induced toxicity for motor neurons remain poorly understood, growing evidence suggest a defective energetic metabolism in skeletal muscles participating in ALS-induced motor neuron death ultimately destabilizing neuromuscular junctions. In the present study, we report that a specific exercise paradigm, based on a high intensity and amplitude swimming exercise, significantly improves glucose metabolism in ALS mice. Using physiological tests and a biophysics approach based on nuclear magnetic resonance (NMR), we unexpectedly found that SOD1(G93A) ALS mice suffered from severe glucose intolerance, which was counteracted by high intensity swimming but not moderate intensity running exercise. Furthermore, swimming exercise restored the highly ALS-sensitive tibialis muscle through an autophagy-linked mechanism involving the expression of key glucose transporters and metabolic enzymes, including GLUT4 and glyceraldehyde-3-phosphate dehydrogenase (GAPDH). Importantly, GLUT4 and GAPDH expression defects were also found in muscles from ALS patients. Moreover, we report that swimming exercise induced a triglyceride accumulation in ALS tibialis, likely resulting from an increase in the expression levels of lipid transporters and biosynthesis enzymes, notably DGAT1 and related proteins. All these data provide the first molecular basis for the differential effects of specific exercise type and intensity in ALS, calling for the use of physical exercise as an appropriate intervention to alleviate symptoms in this debilitating disease.

11.
J Physiol ; 594(7): 1931-52, 2016 Apr 01.
Article in English | MEDLINE | ID: mdl-26915343

ABSTRACT

KEY POINTS: The real impact of physical exercise parameters, i.e. intensity, type of contraction and solicited energetic metabolism, on neuroprotection in the specific context of neurodegeneration remains poorly explored. In this study behavioural, biochemical and cellular analyses were conducted to compare the effects of two different long-term exercise protocols, high intensity swimming and low intensity running, on motor units of a type 3 spinal muscular atrophy (SMA)-like mouse model. Our data revealed a preferential SMA-induced death of intermediate and fast motor neurons which was limited by the swimming protocol only, suggesting a close relationship between neuron-specific protection and their activation levels by specific exercise. The exercise-induced neuroprotection was independent of SMN protein expression and associated with specific metabolic and behavioural adaptations with notably a swimming-induced reduction of muscle fatigability. Our results provide new insight into the motor units' adaptations to different physical exercise parameters and will contribute to the design of new active physiotherapy protocols for patient care. ABSTRACT: Spinal muscular atrophy (SMA) is a group of autosomal recessive neurodegenerative diseases differing in their clinical outcome, characterized by the specific loss of spinal motor neurons, caused by insufficient level of expression of the protein survival of motor neuron (SMN). No cure is at present available for SMA. While physical exercise might represent a promising approach for alleviating SMA symptoms, the lack of data dealing with the effects of different exercise types on diseased motor units still precludes the use of active physiotherapy in SMA patients. In the present study, we have evaluated the efficiency of two long-term physical exercise paradigms, based on either high intensity swimming or low intensity running, in alleviating SMA symptoms in a mild type 3 SMA-like mouse model. We found that 10 months' physical training induced significant benefits in terms of resistance to muscle damage, energetic metabolism, muscle fatigue and motor behaviour. Both exercise types significantly enhanced motor neuron survival, independently of SMN expression, leading to the maintenance of neuromuscular junctions and skeletal muscle phenotypes, particularly in the soleus, plantaris and tibialis of trained mice. Most importantly, both exercises significantly improved neuromuscular excitability properties. Further, all these training-induced benefits were quantitatively and qualitatively related to the specific characteristics of each exercise, suggesting that the related neuroprotection is strongly dependent on the specific activation of some motor neuron subpopulations. Taken together, the present data show significant long-term exercise benefits in type 3 SMA-like mice providing important clues for designing rehabilitation programmes in patients.


Subject(s)
Muscular Atrophy, Spinal/therapy , Physical Conditioning, Animal/methods , Physical Exertion , Animals , Evoked Potentials, Motor , Mice , Muscle, Skeletal/metabolism , Muscle, Skeletal/pathology , Muscle, Skeletal/physiopathology , Muscular Atrophy, Spinal/physiopathology , Muscular Atrophy, Spinal/prevention & control , Running , Survival of Motor Neuron 1 Protein/genetics , Survival of Motor Neuron 1 Protein/metabolism , Swimming
12.
J Neurosci ; 35(34): 12063-79, 2015 Aug 26.
Article in English | MEDLINE | ID: mdl-26311784

ABSTRACT

Spinal muscular atrophy (SMA) is a neuromuscular disease characterized by the selective loss of spinal motor neurons due to the depletion of the survival of motor neuron (SMN) protein. No therapy is currently available for SMA, which represents the leading genetic cause of death in childhood. In the present study, we report that insulin-like growth factor-1 receptor (Igf-1r) gene expression is enhanced in the spinal cords of SMA-like mice. The reduction of expression, either at the physiological (through physical exercise) or genetic level, resulted in the following: (1) a significant improvement in lifespan and motor behavior, (2) a significant motor neuron protection, and (3) an increase in SMN expression in spinal cord and skeletal muscles through both transcriptional and posttranscriptional mechanisms. Furthermore, we have found that reducing IGF-1R expression is sufficient to restore intracellular signaling pathway activation profile lying downstream of IGF-1R, resulting in both the powerful activation of the neuroprotective AKT/CREB pathway and the inhibition of the ERK and JAK pathways. Therefore, reducing rather than enhancing the IGF-1 pathway could constitute a useful strategy to limit neurodegeneration in SMA. SIGNIFICANCE STATEMENT: Recent evidence of IGF-1 axis alteration in spinal muscular atrophy (SMA), a very severe neurodegenerative disease affecting specifically the motor neurons, have triggered a renewed interest in insulin-like growth factor-1 (IGF-1) pathway activation as a potential therapeutic approach for motor neuron diseases. The present study challenges this point of view and brings the alternative hypothesis that reducing rather than enhancing the IGF-1 signaling pathway exerts a neuroprotective effect in SMA. Furthermore, the present data substantiate a newly emerging concept that the modulation of IGF-1 receptor expression is a key event selectively determining the activation level of intracellular pathways that lie downstream of the receptor. This aspect should be considered when designing IGF-1-based treatments for neurodegenerative diseases.


Subject(s)
Muscular Atrophy, Spinal/metabolism , Muscular Atrophy, Spinal/prevention & control , Receptor, IGF Type 1/metabolism , Signal Transduction/physiology , Animals , Cells, Cultured , Female , Humans , Male , Mice , Mice, Knockout , Mice, Transgenic , Muscular Atrophy, Spinal/genetics , Receptor, IGF Type 1/genetics
13.
Am J Pathol ; 182(6): 2298-309, 2013 Jun.
Article in English | MEDLINE | ID: mdl-23624156

ABSTRACT

Dysferlinopathy refers to a group of autosomal recessive muscular dystrophies due to mutations in the dysferlin gene causing deficiency of a membrane-bound protein crucially involved in plasma membrane repair. The condition is characterized by marked clinical heterogeneity, the different phenotypes/modes of presentation being unrelated to the genotype. For unknown reasons, patients are often remarkably active before the onset of symptoms. Dysferlin deficiency-related persistence of mechanically induced sarcolemma disruptions causes myofiber damage and necrosis. We postulate that limited myodamage may initially remain hidden with well-preserved resistance to physical strains. By subjecting dysferlin-deficient B6.A/J-Dysf(prmd) mice to long-term swimming exercise, we observed that concentric/isometric strain improved muscle strength and alleviated muscular dystrophy by limiting the accumulation of membrane lesions. By contrast, eccentric strain induced by long-term running in a wheel worsened the dystrophic process. Myofiber damage induced by eccentric strain increased with age, reflecting the accumulation of non-necrotic membrane lesions up to a critical threshold. This phenomenon was modulated by daily spontaneous activity. Transposed to humans, our results may suggest that the past activity profile shapes the clinical phenotype of the myopathy and that patients with dysferlinopathy should likely benefit from concentric exercise-based physiotherapy.


Subject(s)
Muscular Dystrophies, Limb-Girdle/rehabilitation , Physical Conditioning, Animal/physiology , Aging/pathology , Aging/physiology , Animals , Cell Membrane/ultrastructure , Dysferlin , Locomotion/physiology , Membrane Proteins/deficiency , Mice , Mice, Mutant Strains , Microscopy, Electron , Muscle Contraction/physiology , Muscle Fibers, Skeletal/pathology , Muscle Strength/physiology , Muscle, Skeletal/physiopathology , Muscular Dystrophies, Limb-Girdle/etiology , Muscular Dystrophies, Limb-Girdle/pathology , Muscular Dystrophies, Limb-Girdle/physiopathology , Necrosis , Quadriceps Muscle/ultrastructure , Running/physiology , Swimming/physiology
14.
J Neurosci ; 33(10): 4280-94, 2013 Mar 06.
Article in English | MEDLINE | ID: mdl-23467345

ABSTRACT

Spinal muscular atrophy (SMA), a recessive neurodegenerative disease, is characterized by the selective loss of spinal motor neurons. No available therapy exists for SMA, which represents one of the leading genetic causes of death in childhood. SMA is caused by a mutation of the survival-of-motor-neuron 1 (SMN1) gene, leading to a quantitative defect in the survival-motor-neuron (SMN) protein expression. All patients retain one or more copies of the SMN2 gene, which modulates the disease severity by producing a small amount of stable SMN protein. We reported recently that NMDA receptor activation, directly in the spinal cord, significantly enhanced the transcription rate of the SMN2 genes in a mouse model of very severe SMA (referred as type 1) by a mechanism that involved AKT/CREB pathway activation. Here, we provide the first compelling evidence for a competition between the MEK/ERK/Elk-1 and the phosphatidylinositol 3-kinase/AKT/CREB signaling pathways for SMN2 gene regulation in the spinal cord of type 1 SMA-like mice. The inhibition of the MEK/ERK/Elk-1 pathway promotes the AKT/CREB pathway activation, leading to (1) an enhanced SMN expression in the spinal cord of SMA-like mice and in human SMA myotubes and (2) a 2.8-fold lifespan extension in SMA-like mice. Furthermore, we identified a crosstalk between ERK and AKT signaling pathways that involves the calcium-dependent modulation of CaMKII activity. Together, all these data open new perspectives to the therapeutic strategy for SMA patients.


Subject(s)
Cyclic AMP Response Element-Binding Protein/metabolism , Extracellular Signal-Regulated MAP Kinases/metabolism , Motor Neurons/physiology , Muscular Atrophy, Spinal/pathology , Signal Transduction/physiology , Animals , Animals, Newborn , Butadienes/pharmacology , Calcium/metabolism , Cell Survival/physiology , Cells, Cultured , Chromatin Immunoprecipitation , Coculture Techniques/methods , Cyclic AMP Response Element-Binding Protein/genetics , Disease Models, Animal , Enzyme Inhibitors/pharmacology , Excitatory Amino Acid Agonists/pharmacology , Exploratory Behavior/drug effects , Extracellular Signal-Regulated MAP Kinases/genetics , Female , Ganglia, Spinal/cytology , Humans , Male , Mice , Mice, Knockout , Motor Neurons/drug effects , Motor Neurons/pathology , Muscle Cells/drug effects , Muscle Cells/physiology , N-Methylaspartate/pharmacology , Nitriles/pharmacology , Signal Transduction/drug effects , Signal Transduction/genetics , Stem Cells/drug effects , Stem Cells/physiology , Survival of Motor Neuron 2 Protein/deficiency
15.
Hum Mol Genet ; 22(4): 668-84, 2013 Feb 15.
Article in English | MEDLINE | ID: mdl-23136128

ABSTRACT

SMN1, the causative gene for spinal muscular atrophy (SMA), plays a housekeeping role in the biogenesis of small nuclear RNA ribonucleoproteins. SMN is also present in granular foci along axonal projections of motoneurons, which are the predominant cell type affected in the pathology. These so-called RNA granules mediate the transport of specific mRNAs along neurites and regulate mRNA localization, stability, as well as local translation. Recent work has provided evidence suggesting that SMN may participate in the assembly of RNA granules, but beyond that, the precise nature of its role within these structures remains unclear. Here, we demonstrate that SMN associates with polyribosomes and can repress translation in an in vitro translation system. We further identify the arginine methyltransferase CARM1 as an mRNA that is regulated at the translational level by SMN and find that CARM1 is abnormally up-regulated in spinal cord tissue from SMA mice and in severe type I SMA patient cells. We have previously characterized a novel regulatory pathway in motoneurons involving the SMN-interacting RNA-binding protein HuD and CARM1. Thus, our results suggest the existence of a potential negative feedback loop in this pathway. Importantly, an SMA-causing mutation in the Tudor domain of SMN completely abolished translational repression, a strong indication for the functional significance of this novel SMN activity in the pathology.


Subject(s)
Gene Expression Regulation, Enzymologic , Protein Biosynthesis , Survival of Motor Neuron 1 Protein/genetics , Animals , Cells, Cultured , Genes, Reporter , Humans , Luciferases, Renilla/biosynthesis , Luciferases, Renilla/genetics , Mice , Mice, Transgenic , Muscular Atrophy, Spinal/genetics , Muscular Atrophy, Spinal/metabolism , Polyribosomes/metabolism , Protein Structure, Tertiary , Protein-Arginine N-Methyltransferases/genetics , Protein-Arginine N-Methyltransferases/metabolism , RNA, Messenger/genetics , RNA, Messenger/metabolism , Ribonucleoproteins/metabolism , Spinal Cord/enzymology , Survival of Motor Neuron 1 Protein/metabolism , Survival of Motor Neuron 1 Protein/physiology , Untranslated Regions , Up-Regulation
16.
J Physiol ; 590(22): 5907-25, 2012 Nov 15.
Article in English | MEDLINE | ID: mdl-22930275

ABSTRACT

Spinal muscular atrophy (SMA), the leading genetic cause of death in infants worldwide, is due to the misexpression of the survival of motor neuron protein, causing death of motor neurons. Several clinical symptoms suggested that, in addition to motor neurons, the autonomic nervous systems could be implicated in the cardiac function alterations observed in patienst with SMA. These alterations were also found in a severe SMA mouse model, including bradycardia and a reduction of sympathetic innervation, both associated with autonomic imbalance. In the present study, we investigate the extent of autonomic dysfunction and the effects of a running-based exercise on the altered cardiorespiratory function in type 2 SMA-like mice. We observed that the SMA induced: (1) a dramatic alteration of intrinsic cardiac conduction associated with bradycardia; (2) a severe cardiomyopathy associated with extensive ventricular fibrosis; and (3) a delay in cardiac muscle maturation associated with contractile protein expression defects. Furthermore, our data indicate that the sympathetic system is not only functioning, but also likely contributes to alleviate the bradycardia and the arrhythmia in SMA-like mice. Moreover, physical exercise provides many benefits, including the reduction of cardiac protein expression defect, the reduction of fibrosis, the increase in cardiac electrical conduction velocity, and the drastic reduction in bradycardia and arrhythmias resulting in the partial restoration of the cardiac function in these mice. Thus, modulating the cardiorespiratory function in SMA could represent a new target for improving supportive care and for developing new pharmacological and non-pharmacological interventions that would most certainly include physical exercise.


Subject(s)
Bradycardia/physiopathology , Fibrosis/physiopathology , Heart Ventricles/pathology , Physical Exertion , Spinal Muscular Atrophies of Childhood/physiopathology , Animals , Bradycardia/genetics , Contractile Proteins/genetics , Contractile Proteins/metabolism , Fibrosis/genetics , Gene Expression , Heart Ventricles/metabolism , Heart Ventricles/physiopathology , Mice , Mice, Transgenic , Running , Spinal Muscular Atrophies of Childhood/genetics , Survival of Motor Neuron 1 Protein/genetics , Sympathetic Nervous System/physiopathology
17.
PLoS One ; 6(11): e27283, 2011.
Article in English | MEDLINE | ID: mdl-22076146

ABSTRACT

Apoptosis Inducing Factor (AIF) is a highly conserved, ubiquitous flavoprotein localized in the mitochondrial intermembrane space. In vivo, AIF provides protection against neuronal and cardiomyocyte apoptosis induced by oxidative stress. Conversely in vitro, AIF has been demonstrated to have a pro-apoptotic role upon induction of the mitochondrial death pathway, once AIF translocates to the nucleus where it facilitates chromatin condensation and large scale DNA fragmentation. Given that the aif hypomorphic harlequin (Hq) mutant mouse model displays severe sarcopenia, we examined skeletal muscle from the aif hypomorphic mice in more detail. Adult AIF-deficient skeletal myofibers display oxidative stress and a severe form of atrophy, associated with a loss of myonuclei and a fast to slow fiber type switch, both in "slow" muscles such as soleus, as well as in "fast" muscles such as extensor digitorum longus, most likely resulting from an increase of MEF2 activity. This fiber type switch was conserved in regenerated soleus and EDL muscles of Hq mice subjected to cardiotoxin injection. In addition, muscle regeneration in soleus and EDL muscles of Hq mice was severely delayed. Freshly cultured myofibers, soleus and EDL muscle sections from Hq mice displayed a decreased satellite cell pool, which could be rescued by pretreating aif hypomorphic mice with the manganese-salen free radical scavenger EUK-8. Satellite cell activation seems to be abnormally long in Hq primary culture compared to controls. However, AIF deficiency did not affect myoblast cell proliferation and differentiation. Thus, AIF protects skeletal muscles against oxidative stress-induced damage probably by protecting satellite cells against oxidative stress and maintaining skeletal muscle stem cell number and activation.


Subject(s)
Apoptosis Inducing Factor/physiology , Apoptosis , Muscle Fibers, Skeletal/physiology , Oxidative Stress , Animals , Antioxidants/pharmacology , Autonomic Nervous System Diseases , Blotting, Western , Cell Count , Cell Differentiation , DNA Fragmentation , Ethylenediamines/pharmacology , Fluorescent Antibody Technique , Flushing , Hypohidrosis , Immunoenzyme Techniques , Male , Mice , Mice, Inbred C57BL , Mice, Inbred CBA , Mice, Mutant Strains , Mitochondria/drug effects , Muscle Fibers, Skeletal/cytology , Muscle Fibers, Skeletal/drug effects , Muscular Atrophy/etiology , Muscular Atrophy/metabolism , Muscular Atrophy/pathology , Organometallic Compounds/pharmacology , Phenotype , RNA, Messenger/genetics , Reactive Oxygen Species/metabolism , Real-Time Polymerase Chain Reaction
18.
J Neurosci ; 30(34): 11288-99, 2010 Aug 25.
Article in English | MEDLINE | ID: mdl-20739549

ABSTRACT

Spinal muscular atrophy (SMA), a lethal neurodegenerative disease that occurs in childhood, is caused by the misexpression of the survival of motor neuron (SMN) protein in motor neurons. It is still unclear whether activating motor units in SMA corrects the delay in the postnatal maturation of the motor unit resulting in an enhanced neuroprotection. In the present work, we demonstrate that an adequate NMDA receptor activation in a type 2 SMA mouse model significantly accelerated motor unit postnatal maturation, counteracted apoptosis in the spinal cord, and induced a marked increase of SMN expression resulting from a modification of SMN2 gene transcription pattern. These beneficial effects were dependent on the level of NMDA receptor activation since a treatment with high doses of NMDA led to an acceleration of the motor unit maturation but favored the apoptotic process and decreased SMN expression. In addition, these results suggest that the NMDA-induced acceleration of motor unit postnatal maturation occurred independently of SMN. The NMDA receptor activating treatment strongly extended the life span in two different mouse models of severe SMA. The analysis of the intracellular signaling cascade that lay downstream the activated NMDA receptor revealed an unexpected reactivation of the CaMKII/AKT/CREB (cAMP response element-binding protein) pathway that induced an enhanced SMN expression. Therefore, pharmacological activation of spinal NMDA receptors could constitute a useful strategy for both increasing SMN expression and limiting motor neuron death in SMA spinal cord.


Subject(s)
Motor Neurons/physiology , Muscle Fibers, Skeletal/physiology , Muscular Atrophy, Spinal/metabolism , Receptors, N-Methyl-D-Aspartate/metabolism , Spinal Cord/growth & development , Survival of Motor Neuron 2 Protein/biosynthesis , Animals , Coculture Techniques , Female , Gene Expression Regulation , Humans , Male , Mice , Mice, Knockout , Mice, Transgenic , Motor Neurons/drug effects , Muscle Fibers, Skeletal/drug effects , Muscular Atrophy, Spinal/pathology , Muscular Atrophy, Spinal/prevention & control , N-Methylaspartate/pharmacology , N-Methylaspartate/therapeutic use , Neuroprotective Agents/pharmacology , Neuroprotective Agents/therapeutic use , Receptors, N-Methyl-D-Aspartate/agonists , Severity of Illness Index , Spinal Cord/drug effects
19.
J Physiol ; 587(Pt 14): 3561-72, 2009 Jul 15.
Article in English | MEDLINE | ID: mdl-19491245

ABSTRACT

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.


Subject(s)
Amyotrophic Lateral Sclerosis/pathology , Amyotrophic Lateral Sclerosis/physiopathology , Disease Models, Animal , Exercise Therapy , Motor Neurons/pathology , Physical Conditioning, Animal/methods , Physical Exertion , Action Potentials , Amyotrophic Lateral Sclerosis/prevention & control , Animals , Cell Survival , Humans , Male , Mice , Mice, Transgenic
20.
J Neurosci ; 28(4): 953-62, 2008 Jan 23.
Article in English | MEDLINE | ID: mdl-18216203

ABSTRACT

Spinal muscular atrophy (SMA) is an inborn neuromuscular disorder caused by low levels of survival motor neuron protein, and for which no efficient therapy exists. Here, we show that the slower rate of postnatal motor-unit maturation observed in type 2 SMA-like mice is correlated with the motor neuron death. Physical exercise delays motor neuron death and leads to an increase in the postnatal maturation rate of the motor-units. Furthermore, exercise is capable of specifically enhancing the expression of the gene encoding the major activating subunit of the NMDA receptor in motor neurons, namely the NR2A subunit, which is dramatically downregulated in the spinal cord of type 2 SMA-like mice. Accordingly, inhibiting NMDA-receptor activity abolishes the exercise-induced effects on muscle development, motor neuron protection and life span gain. Thus, restoring NMDA-receptor function could be a promising therapeutic approach to SMA treatment.


Subject(s)
Motor Neurons/metabolism , Physical Conditioning, Animal/physiology , Receptors, N-Methyl-D-Aspartate/metabolism , Spinal Muscular Atrophies of Childhood/genetics , Spinal Muscular Atrophies of Childhood/metabolism , Animals , Cell Survival/genetics , Disease Models, Animal , Humans , Mice , Mice, Knockout , Mice, Transgenic , Motor Neurons/pathology , Muscle, Skeletal/growth & development , Muscle, Skeletal/metabolism , Muscle, Skeletal/pathology , Receptors, N-Methyl-D-Aspartate/deficiency , Receptors, N-Methyl-D-Aspartate/genetics , Spinal Muscular Atrophies of Childhood/pathology
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