INSR and Insulin resistance: Additionally, Vit D improves insulin resistance by increasing the binding of the active form of Vit D, calcitriol, to Vitamin D Receptor (VDR), forming a heterodimer with the Retinoid-X Receptor (RXR) leading to the modulation of several gene expressions involved in glucose metabolisms, such as PPARγ, Hepatocyte Nuclear Factor-1 Alpha (HNF-1α), and insulin receptor substrates (IRs) as a transcription factor14.