INS and obesity due to melanocortin 4 receptor deficiency: VDR is expressed in adipose tissue, which produces, stores, and degrades active vitamin D. Due to the close link between obesity, glucose homeostasis, and hypovitaminosis D, having a good vitamin D status may be desirable, and based on the known mechanisms involved in the action of vitamin D. Obese individuals may represent the primary recipients of vitamin D's effects on insulin sensitivity modulation and T2DM prevention.