The VDR gene provides instructions for making a protein called vitamin D receptor (VDR), which allows the cells to respond to vitamin D. This vitamin can be acquired from foods in the diet or made in the body with help from sunlight exposure. The vitamin D receptor (VDR), is a member of the nuclear receptor superfamily of transcriptional regulators. Vitamin D is involved in maintaining the proper balance of several minerals in the body, including calcium and phosphate, which are essential for the normal formation of bones and teeth. One of vitamin D's major roles is to control the absorption of calcium and phosphate from the intestines into the bloodstream. Vitamin D is also involved in several processes unrelated to bone and tooth formation.
The VDR protein binds to the active form of vitamin D, known as calcitriol. This interaction allows VDR to partner with another protein called retinoid X receptor (RXR). The Vitamin D-VDR-RXR complex migrates to the nucleus to regulate the transcription of genes involved in vitamin D effects including phosphorous and calcium metabolism, cell proliferation, and the control of innate and adaptive immunity.
Although the mechanism is not completely understood, the VDR protein is also involved in hair growth. Studies suggest that this process does not require calcitriol binding.
The VDR gene is located on chromosome 12 (12q13.11) and more than 900 allelic variants in the VDR locus have been reported. These genetic variants have been associated with a predisposition to chronic diseases such as type 2 diabetes, cancer, autoimmune diseases, cardiovascular alterations, rheumatic arthritis, osteoarthritis, osteoporosis, degenerative disc disease, and metabolic bone diseases.
Also, researchers found that VDR regulates vitamin D levels and calcium metabolism in the body, and these are known to be associated with endocrine dysfunctions, and insulin resistance. Vitamin D has been reported to influence glucose regulation via its effects on insulin secretion and action. Evidence is accumulating to suggest that altered vitamin D and Ca homeostasis may play a role in the development of metabolic disturbances in insulin resistance-related diseases. More and more studies found that vitamin D was useful for insulin resistance diseases.
Diabetes type 2, metabolic syndrome, and pre-diabetes are common metabolic disorders that are observed with increasing prevalence, and which are caused by a complex interplay between genetic and environmental factors, and these metabolic disorders are all characterized by insulin resistance. PCOS is by far the most common cause of anovulatory infertility and has been reported to be associated with insulin resistance, hyperinsulinemia, dyslipidemia, and central obesity, which are all risk factors for metabolic syndrome, type 2 diabetes, and cardiovascular disease. Several studies have assessed vitamin D receptor gene polymorphism in relationship with these diseases.