Vitamin D supplementation improves simvastatin-mediated decline in exercise performance: A randomized double-blind placebo-controlled study.
The aim of the present study was to determine the effect of vitamin D supplementation on simvastatin-mediated changes in cardiorespiratory fitness and skeletal muscle mitochondrial content after exercise in adults with type 2 diabetes mellitus (T2DM). Vitamin D-deficient T2DM patients aged 25-50 years performed moderate intensity aerobic exercise for 12 weeks and were randomized to receive simvastatin 40 mg daily, simvastatin 40 mg daily plus vitamin D 60 000 units once weekly, or vitamin D 60 000 units once weekly. The primary outcomes were cardiorespiratory fitness (peak oxygen consumption) and skeletal muscle mitochondrial content (citrate synthase activity in the vastus lateralis) following simvastatin and/or vitamin D replacement therapy. Twenty-eight patients completed the study. Cardiorespiratory fitness decreased by 8.4% (P < 0.05) following 12 weeks of simvastatin therapy. Vitamin D supplementation blunted the decline in cardiorespiratory fitness to 0.6% (P < 0.05 for between-group difference in change from baseline). Similarly, skeletal muscle mitochondrial content decreased by 3.6% with simvastatin, but improved by 12.1% on supplementation with vitamin D, although the between-group difference was not significant. Vitamin D alone increased cardiorespiratory fitness and mitochondrial content by 7.1% (P < 0.05) and 16.7%, respectively. Simvastatin tends to cause deterioration in exercise-associated cardiorespiratory fitness and skeletal muscle mitochondrial content in adults with T2DM, which is blunted by vitamin D supplementation.