Diet-Induced Vitamin D Deficiency Results in Reduced Skeletal Muscle Mitochondrial Respiration in C57BL/6J Mice
Vitamin D deficiency is known to be associated with symptoms of skeletal muscle myopathy including muscle weakness and fatigue. Recently, vitamin D related metabolites have been linked to the maintenance of mitochondrial function within skeletal muscle. However, current evidence is limited to in vitro models and the effects of diet-induced vitamin D deficiency upon skeletal muscle mitochondrial function in vivo have received little attention. In order to examine the role of vitamin D in the maintenance of mitochondrial function in vivo, we utilised an established model of diet-induced vitamin D deficiency in C57BL/6J mice. Mice were fed either a control (2,200 IU/kg) or a vitamin D deplete (0 IU/kg) diet for periods of 1-, 2- and 3-months. Skeletal muscle mitochondrial function and ADP sensitivity were assessed via high-resolution respirometry and mitochondrial protein content via immunoblotting. As a result of 3-month of diet-induced vitamin D deficiency, respiration supported via CI+IIP and ETC were 35% and 37% lower when compared to vitamin D replete mice (P < 0.05). Despite functional alterations, the protein expression of electron transfer chain subunits remained unchanged in response to dietary intervention (P > 0.05). In conclusion, we report that 3-months of diet-induced vitamin D deficiency reduced skeletal muscle mitochondrial function in C57BL/6J mice. Our data, when combined with previous in vitro observations, suggests that vitamin D mediated regulation of mitochondrial function may underlie the exacerbated muscle fatigue and performance deficits observed during vitamin D deficiency.