Role of Gut Microbiota in Bridging Vitamin D Deficiency and Type 2 Diabetes Mellitus Pathogenesis

Type 2 diabetes mellitus (T2DM) is a complex metabolic disorder. The nutritional status of vitamin D, an essential micronutrient, is closely linked to the onset and progression of T2DM. A growing body of research has shown that gut microbiota and its metabolites are emerging as a biological link connecting vitamin D and systemic glucose metabolism. Gut dysbiosis is prevalent in T2DM patients, which is characterized by reduced gut microbial diversity, increased abundance of pathogenic bacteria, and abnormal production of key metabolites such as short-chain fatty acids, bile acids and tryptophan derivatives. These abnormal changes in gut microecology and metabolites can impair intestinal barrier integrity and induce chronic low-grade inflammation in the body, and vitamin D deficiency may further exacerbate these abnormal processes. The evidence suggests that the regulatory effect of vitamin D on systemic glucose metabolism may be partially achieved through gut microbiota-related pathways. This review aims to explore whether, and by what mechanisms, the gut microbiota mediates the regulatory effect of vitamin D on T2DM. It also intends to conduct an analysis of the potential molecular mechanisms underlying the interactions between vitamin D, gut microbiota and T2DM, so as to provide a new theoretical basis and research ideas for the prevention and intervention of T2DM.