Vitamin D, Vitamin D Receptor, and Adipose Tissue: Focus on Cellular Mechanisms

Adipose tissue is a known storage site for vitamin D steroids and is rapidly emerging as a clinically relevant target tissue for 1,25(OH)₂D. Links between vitamin D, body weight, and obesity have been proposed based on clinical and population studies; however, mechanistic understanding of the relationship is limited. The vitamin D receptor (VDR) is expressed in adipocyte precursors and is regulated during the differentiation process, but the impact of 1,25(OH)₂D on adipogenesis varies considerably with model systems. A lean phenotype associated with enhanced energy expenditure has been confirmed in mice with genetic deletions in VDR, but whether this phenotype reflects actions of the receptor and/or its ligand in adipose tissue remains to be resolved. This chapter will provide a brief update on the role of adipose tissue as a storage depot for vitamin D and will review the effects of 1,25(OH)₂D and the VDR on adipogenesis in vitro and adiposity in animal models.