Vitamin D and development of diabetes mellitus

Vitamin D and development of diabetes mellitus

Vitamin D receptors have been found in various cell types, including the pancreatic beta cells, and active vitamin D is reportedly involved in insulin biosynthesis and secretion (1):

• vitamin D seems to play a regulatory role in insulin secretion, beta-cell survival and calcium flux within beta-cells
  • studies have shown that vitamin D deficiency impairs glucose-mediated insulin secretion in rat pancreatic beta cells, while vitamin D supplementation seems to restore such glucose-stimulated insulin secretion
  • vitamin D may also have a direct effect on beta-cell function, which seems to be exerted by binding of its circulating active form to the vitamin D receptor (VDR) that is expressed in pancreatic beta-cells

Evidence summary (1,2):

• obbservational studies have shown that vitamin D deficiency is associated with insulin resistance and an increased risk of future diabetes
  
  
• results of randomised controlled trials of vitamin D supplementation for preventing type 2 diabetes are not consistent (1)
  • effect of vitamin D supplementation on glycemia or incident type 2 diabetes has been reported in several trials with mixed results
    
    
• a previous study suggested that vitamin D supplementation was beneficial for people with pre-diabetes and vitamin D deficiency (2)

A study assessed whether eldecalcitol, an active vitamin D analogue, can reduce the development of type 2 diabetes among adults with impaired glucose tolerance (2):

• treatment with eldecalcitoldid not significantly reduce the incidence of diabetes and failed to increase the rate of regression to normoglycaemia compared with placebo among patients with impaired glucose tolerance who were at high risk for type 2 diabetes
  • however, the study suggested the potential for a beneficial effect of active vitamin D treatment on the prevention of type 2 diabetes after adjustment for confounding factors

Reference:

• Mitri J, Pittas AG. Vitamin D and diabetes. Endocrinol Metab Clin North Am. 2014;43(1):205-232. doi:10.1016/j.ecl.2013.09.010
• Kawahara T, Suzuki G, Mizuno S, Inazu T, Kasagi F, Kawahara C et al. Effect of active vitamin D treatment on development of type 2 diabetes: DPVD randomised controlled trial in Japanese population BMJ 2022; 377 :e066222 doi:10.1136/bmj-2021-066222