No abstract

Regulated removal of proteins and organelles by autophagy-lysosome system is critical for muscle homeostasis. Excessive activation of autophagy-dependent degradation contributes to muscle atrophy and cachexia. Conversely, inhibition of autophagy causes accumulation of protein aggregates and abnormal organelles, leading to myofiber degeneration and myopathy. Defects in lysosomal function result in severe muscle disorders such as Pompe (glycogen storage disease type II (GSDII)) disease, characterized by an accumulation of autophagosomes. However, whether autophagy is detrimental or not in muscle function of Pompe patients is unclear. We studied infantile and late-onset GSDII patients and correlated impairment of autophagy with muscle wasting. We also monitored autophagy in patients who received recombinant a-glucosidase. Our data show that infantile and late-onset patients have different levels of autophagic flux, accumulation of p62-positive protein aggregates and expression of atrophy-related genes. Although the infantile patients show impaired autophagic function, the lateonset patients display an interesting correlation among autophagy impairment, atrophy and disease progression. Moreover, reactivation of autophagy in vitro contributes to acid a-glucosidase maturation in both healthy and diseased myotubes. Together, our data suggest that autophagy protects myofibers from disease progression and atrophy in late-onset patients.

Myophosphorylase deficiency is characterized by exercise intolerance, muscle cramps, and recurrent myoglobinuria. Some patients are severely affected, whereas others are minimally affected or asymptomatic. The molecular basis of the disease has been elucidated but does not provide an explanation for the clinical variability. In a large cohort of patients with myophosphorylase deficiency, we tested the hypothesis that polymorphic variants in either myoadenylate deaminase (MADA) or angiotensin-converting enzyme (ACE) could act as modulators of phenotype expression. Forty-seven patients were evaluated. Clinical severity was assessed according to a severity scale of four grades. MADA activity was studied by histochemical and biochemical analysis of muscle, and the Q12X mutation in the adenine monophosphate deaminase 1 gene (AMPD1) and the insertion/deletion polymorphism in the ACE gene were assessed genetically. A complete MADA defect together with the Q12X mutation was detected in one severely affected patient. Eleven patients were heterozygous for the Q12X mutation. There was no association between clinical grading and MADA status. In contrast, we found a highly significant (p < 0.01) association between ACE genotype and clinical severity, with strong correlation between severe phenotype and number of D alleles. We show that ACE insertion/deletion polymorphism may play a significant role as phenotype modulator in McArdle's disease.

ERT positively modified skeletal muscle pathology as well as motor and respiratory outcomes in the majority of LOPD patients.

Aims:The peculiar clinical features and the pathogenic mechanism related to calpain-3 deficiency (impaired sarcomere remodelling) suggest that the ubiquitinproteasome degradation pathway may have a crucial role in Limb Girdle Muscular Dystrophy 2A (LGMD2A). We therefore investigated muscle atrophy and the role of the ubiquitin-proteasome and lysosomal-autophagic degradation pathways. Methods: We selected 25 adult male LGMD2A patients (and seven controls), classified them using clinical severity score, analysed muscle fibre size by morphometry and protein and/or transcriptional expression levels of the most important atrophy-and autophagyrelated genes (MuRF1, atrogin1, LC3, p62, Bnip3). Results: Muscle fibre size was significantly lower in LGMD2A than in controls and it was significantly correlated with patients' clinical disability score recorded at the time of biopsy, suggesting that functional and structural muscle impairment are dependent. The large majority of atrophic fibres originate from a mechanism different from regeneration, as assessed by neonatal myosin immunolabelling. As compared with controls, LGMD2A muscles have higher MuRF1 (but not atrogin1) protein and MuRF1 gene expression levels, and MuRF1 protein levels significantly correlated with both muscle fibre size and clinical disability score.LGMD2A muscles have slightly increased levels of LC3-II and p62 proteins and a significant up-regulation of p62 and Bnip3 gene expression. Conclusions: In LGMD2A muscles the activation of the atrophy programme appeared to depend mainly upon induction of the ubiquitin-proteasome system and, to a lesser extent, the autophagic-lysosomal degradation pathway.