Activation of autophagy in patients with col6 myopathy through an experimental protein-free pilot diet.
A pilot study based on nutritional modulation was designed to evaluate the efficacy of a low protein diet over one year for autophagy activation in skeletal muscle of patients affected by COL6 myopathies. Ullrich congenital muscular dystrophy and Bethlem myopathy are rare inherited muscle disorders caused by mutations in the COL6, A1 A2 A3 genes, and for which there is no cure yet. Studies in col6-deficient mice revealed that muscle fiber degeneration involves autophagic defects and that forced activation of autophagy results in improvement of muscle pathology. Seven adult patients with myopathies caused by Col6 deficiency were placed on a controlled low-protein diet for 12 months and we assessed the presence of autophagosomes and mRNA and protein levels for BECN1/Beclin 1 and MAP1LC3B / LC3B in muscle biopsies and blood leukocytes. Muscle strength, motor and respiratory function, and metabolic parameters were assessed. After one year on a low-protein diet, autophagic markers were increased in the patients’ skeletal muscles and blood leukocytes. The safety of the treatment is demonstrated by the preservation of body composition fat percentage, muscle strength and function. Furthermore, the reduced incidence of muscle fiber apoptosis indicated benefits in muscle homeostasis, and the metabolic changes indicated improved mitochondrial function. These data provide evidence that low protein diet is able to activate autophagy and is safe and tolerable in patients with COL6 myopathies, pointing to autophagy activation as a potential target for therapeutic applications. Furthermore, our results indicate that blood leukocytes are a promising non-invasive tool to monitor autophagic activation in patients. Introduction: COL6/collagen VI is a major extracellular matrix protein of the skeletal muscle endomysium. Mutations of the COL6 genes (COL6A1, COL6A2, and COL6A3) cause COL6-related myopathies, a group of rare inherited muscle disorders that include Bethlem myopathy (BM) and Ullrich congenital muscular dystrophy (UCMD), as well as girdle and myosclerosis variants of myopathy. BM is characterized by axial and proximal muscle weakness, together with contractures of the interphalangeal joints of the last 4 fingers. BM is usually mild and sometimes slowly progressive. Respiratory failure is part of the clinical spectrum and can occur in outpatients. UCMD is a severe congenital muscular dystrophy characterized by early onset, generalized muscle wasting and weakness, proximal joint contractures, and distal joint hyperflexibility. Independent walking is rarely achieved or maintained in children with UCMD, who also suffer from early and progressive respiratory failure. There is currently no cure for BM or UCMD. We have previously demonstrated that cyclosporine A is able to rescue muscle alterations associated with COL6 deficiency in diseased mice and in cells from BM or UCMD patients. Although clinical studies have indicated that cyclosporine A may be beneficial in slowing disease progression by correcting mitochondrial dysfunction, the well-known immunosuppressive activity of cyclosporine A is a major obstacle and hinders its long-term use especially in pediatric patients. Recent studies of diseased mice and patient biopsies have provided new insights into the molecular mechanisms underlying COL6-related myopathies. These studies demonstrated that a failure of the autophagy machines plays an important pathogenetic role in muscle wasting and weakness. Autophagy is an evolutionarily conserved self-degradation process that is essential for recovering nutrients during fasting and for the removal of harmful or damaged cellular components. In the skeletal muscles of diseased mice (col6a1), impaired autophagosome formation triggers the accumulation of dysfunctional mitochondria and organelles in myofibers, leading to apoptosis and myopathy. Notably, restoration of appropriate autophagic flux by genetic, pharmacological, or nutritional approaches rescues the myopathic phenotype of col6a1 mice. Notably, feeding col6a1 mice for one month with a low protein diet (LPD) leads to a recovery of structural and functional muscle defects. Here we report the results of a pilot clinical study with an LPD conducted for 12 months in 7 adu subjects
