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 () 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.
Highlights
Mitochondrial diseases caused by mutations in nuclear and mitochondrial DNA are recognized as the most common types of inherited neuromuscular diseases
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
Patients presented significantly lower peak torque, isometric torque, and total work (Table 2).: We observed that peak VO2, peak work rate, and GET were significantly lower in patients compared to controls (Table 3)
Summary
Mitochondrial diseases caused by mutations in nuclear and mitochondrial DNA (mtDNA) are recognized as the most common types of inherited neuromuscular diseases. These genetic defects in oxidative phosphorylation lead to specific abnormalities in exercise performance, such as a reduced maximal whole-body oxygen consumption and elevated lactate levels during exercise [1,2]. Impaired oxidative phosphorylation may result in exercise intolerance breathlessness, exaggerated lactic acidosis, and low exercise capacity [4]. This effect may augment the patient’s functional limitations and lead to a vicious cycle of exercise intolerance exacerbation [4]
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Schedule a callMore From: Brazilian journal of medical and biological research = Revista brasileira de pesquisas medicas e biologicas
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