Vitamin D Status and Vitamin D-Dependent Apoptosis in Obesity

The role of vitamin D in obesity appears to be linked to vitamin D insufficient/deficient status. However, mechanistic understanding of the role of vitamin D in obesity is lacking. We have shown earlier that the vitamin D hormonal form, 1,25-dihydroxyvitamin D(3) (1,25(OH)(2)D(3)), induces cell death by apoptosis in mature adipocytes. This effect of the hormone is mediated by the cellular Ca(2+) signaling pathway: a sustained increase of intracellular (cytosolic) Ca(2+) concentration followed by activation of Ca(2+)-dependent initiators and effectors of apoptosis. In recent animal studies, we demonstrated that low vitamin D status is observed in diet-induced obesity (DIO). High intake of vitamin D(3) in DIO decreased the weight of white adipose tissue and improved biomarkers related to adiposity and Ca(2+) regulation. The anti-obesity effect of vitamin D (1,25(OH)(2)D(3)) in DIO was determined by the induction of Ca(2+)-mediated apoptosis in mature adipocytes executed by Ca(2+)-dependent apoptotic proteases (calpains and caspases). Thus, a high intake of vitamin D in obesity increases vitamin D nutritional status and normalizes vitamin D hormonal status that is accompanied by the reduction of adiposity. Overall, our findings imply that vitamin D may contribute to the prevention of obesity and obesity-related diseases and that the mechanism of the anti-obesity effect of 1,25(OH)(2)D(3) includes induction of Ca(2+)-mediated apoptosis in adipocytes.