Polymorphisms of the Vitamin D Receptor (VDR) gene: A possible trigger for the onset of obesity, type 2 diabetes mellitus and other metabolic syndromes

Vitamin D is known to perform diverse functions in the body, such as bone remodeling, insulin secretion, and adipogenesis. Vitamin D deficiency (VDD) therefore, causes a substantial setback in the normal functioning of the human body. The two most common health conditions faced today, type 2 diabetes mellitus and obesity, have been linked with VDD. The replenishment of vitamin D improves insulin levels and avoids the incidence of hyperglycemia that indicates its essential role in the secretion of pancreatic insulin. Studies have identified the potential involvement of Vitamin D Receptor (VDR) polymorphisms in altering the gene expression and function. The VDR gene polymorphisms Fold, TaqI, BsmI and ApaI have been identified as the molecular cause of type 2 diabetes. On the other hand, obesity, also known as the 'Pandemic of the 21st century,' has been associated with the polymorphisms described above. Vitamin D has been shown to affect adipogenesis. While obesity has both an environmental and a genetic origin, recent studies are now concentrating on the genetics of the same. In this review, these underlying polymorphisms have been investigated and characterized apropos of obesity, type 2 diabetes and other metabolic syndromes.