[Importance of vitamin D in insulin resistance]

Beyond its classical role in bone metabolism, fundamental and epidemiological studies suggest that vitamin D is also involved in immunity and cell proliferation. Indeed, 25-hydroxyvitamin D 1alpha-hydroxylase and specific receptors for 1,25-dihydroxyvitamin D, the hormonal form of vitamin D, have been found in a variety of organs and tissues, such as the liver, epidermis, thymus, small intestine and pancreas. This brief review examines the results of in vitro, animal and clinical studies suggesting a role of vitamin D in glucose homeostasis. Epidemiological studies and meta-analyses have shown a weak association between vitamin D nutritional status and the risk of diabetes, but this does not justify the increasing demands for serum vitamin D assay. The latter should be restricted to disorders affecting the musculoskeletal system.