The Impact of Vitamin D on Type 2 Diabetes Mellitus: Exploring Its Role in Glucose Metabolism and Insulin Sensitivity

Vitamin D, a fat-soluble secosteroid, plays a pivotal role beyond its functions in calcium and bone homeostasis. Emerging evidence suggests its involvement in glucose metabolism and insulin sensitivity, thus influencing the pathophysiology of Type 2 Diabetes Mellitus (T2DM). For the current review, a search was conducted across four major databases: PubMed, Embase, Google Scholar, and Web of Science. The aim was to identify relevant studies and clinical trials, published in English, reporting the mechanistic insights of the impact of Vitamin D on Type 2 Diabetes Mellitus. Vitamin D influences insulin secretion through the Vitamin D Receptor (VDR) expression in pancreatic β-cells and modulates insulin sensitivity by regulating genes involved in glucose uptake and lipid metabolism in adipose tissue and skeletal muscle. Additionally, Vitamin D reduces inflammation and oxidative stress, which are hallmarks of T2DM progression. Multiple pathways indicate that vitamin D has a direct role in enhancing insulin sensitivity independent of its effects on inflammation. Vitamin D levels in the body can influence the balance between pro-inflammatory and anti-inflammatory cytokines, which affects insulin activity, lipid metabolism, and the development and functionality of adipose tissue. Several epidemiological studies link Vitamin D deficiency to an increased risk of T2DM. This review focuses on the molecular insights and clinical implications of Vitamin D in T2DM. Furthermore, the study addresses knowledge gaps in the relationship between Vitamin D and glucose metabolism in diabetes therapy.