ABSTRACT
Exercise intolerance due to impaired oxidative metabolism is a prominent symptom in patients with mitochondrial myopathy (MM), but it is still uncertain whether L-carnitine supplementation is beneficial for patients with MM. The aim of our study was to investigate the effects of L-carnitine on exercise performance in MM. Twelve MM subjects (mean age±SD=35.4±10.8 years) with chronic progressive external ophthalmoplegia (CPEO) were first compared to 10 healthy controls (mean age±SD=29±7.8 years) before they were randomly assigned to receive L-carnitine supplementation (3 g/daily) or placebo in a double-blind crossover design. Clinical status, body composition, respiratory function tests, peripheral muscle strength (isokinetic and isometric torque) and cardiopulmonary exercise tests (incremental to peak exercise and at 70% of maximal), constant work rate (CWR) exercise test, to the limit of tolerance [Tlim]) were assessed after 2 months of L-carnitine/placebo administration. Patients with MM presented with lower mean height, total body weight, fat-free mass, and peripheral muscle strength compared to controls in the pre-test evaluation. After L-carnitine supplementation, the patients with MM significantly improved their Tlim (14±1.9 vs 11±1.4 min) and oxygen consumption ( V ˙ O 2 ) at CWR exercise, both at isotime (1151±115 vs 1049±104 mL/min) and at Tlim (1223±114 vs 1060±108 mL/min). These results indicate that L-carnitine supplementation may improve aerobic capacity and exercise tolerance during high-intensity CWRs in MM patients with CPEO.
Subject(s)
Adult , Female , Humans , Male , Middle Aged , Young Adult , Carnitine/therapeutic use , Exercise Tolerance/drug effects , Ophthalmoplegia, Chronic Progressive External/drug therapy , Vitamin B Complex/therapeutic use , Cross-Over Studies , Double-Blind Method , Exercise Test/drug effects , Lactic Acid/blood , Mitochondrial Myopathies/drug therapy , Muscle Strength/drug effects , Oxidative Phosphorylation/drug effects , Oxygen Consumption/drug effects , Oxygen Consumption/physiology , SpirometryABSTRACT
Mitochondrial myopathy is a group of multisytemic disease, variable in the age at onset, frequency, clinical data, evolution and prognosis. It results from nuclear or mitochondrial DNA mutation or from defective interaction between nuclear and mitochondrial DNA. The transmission of this mitochondrial myopathy is exlusively maternal. Sometimes the mutationns are born in the maternal ovule, or early in the embryonal life. The diagnosis is suspected on clinical manifestations and is confirmed by existence of ragged - red - fibers in the muscular biopsy, and especially, by molecular study which discovers the mutation of mitochondrial DNA. The treatment is often disappointing, however some specific measures are necessary to improve the quality of patients life