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J Steroid Biochem Mol Biol. 2017 Oct;173:280-285. doi: 10.1016/j.jsbmb.2016.11.021. Epub 2016 Dec 5.

Vitamin D and type 2 diabetes.

Author information

1
Department of Internal Medicine, Endocrine Section, VU University Medical Center, 1007 MB Amsterdam, The Netherlands. Electronic address: p.lips@vumc.nl.
2
Department of Internal Medicine, Endocrine Section, VU University Medical Center, 1007 MB Amsterdam, The Netherlands.
3
Department of Epidemiology and Biostatistics, VU University Medical Center, 1007 MB Amsterdam, The Netherlands.
4
Department of Internal Medicine, Endocrine Section, VU University Medical Center, 1007 MB Amsterdam, The Netherlands; Department of Internal Medicine, Catharina Hospital, 5623 EJ Eindhoven, The Netherlands.
5
Department of Internal Medicine, Medical Center Alkmaar, 1800 AM Alkmaar, The Netherlands.
6
Department of Internal Medicine, Endocrine Section, VU University Medical Center, 1007 MB Amsterdam, The Netherlands; Department of Internal Medicine, Medical Center Alkmaar, 1800 AM Alkmaar, The Netherlands.

Abstract

Vitamin D deficiency is associated with a decreased insulin release, insulin resistance and type 2 diabetes in experimental and epidemiological studies. Animal studies show that 1α,25-dihydroxyvitamin D3 (1,25(OH)2D3) stimulates the pancreatic β-cell to secrete insulin. The relationship between vitamin D deficiency and insulin resistance could develop through inflammation, as vitamin D deficiency is associated with increased inflammatory markers. In addition, genetic polymorphisms of vitamin D -related genes may predispose to impaired glycemic control and type 2 diabetes. Epidemiologic studies showed an association between low serum 25-hydroxyvitamin D3 (25(OH)D3) concentration and an increased risk for the metabolic syndrome and type 2 diabetes. This may be partly explained by an increased fat mass. A possible causal relationship between vitamin D deficiency and type 2 diabetes should be proven by randomized clinical trials showing that either type 2 diabetes can be prevented or insulin release and insulin sensitivity can be improved by vitamin D supplements. The results of randomized clinical trials on the effect of vitamin D versus placebo, sometimes combined with calcium, in patients with impaired glucose tolerance ("prediabetes") or type 2 diabetes are inconsistent. Some studies showed a slight decrease of fasting plasma glucose or improvement of insulin resistance, but often only in posthoc analyses. These effects are mainly visible in patients with vitamin D deficiency and impaired glucose tolerance at baseline. Meta-analyses of randomized clinical trials in general did not show significant effects of vitamin D supplementation on glycemic control. Currently, several large scale randomized clinical trials with vitamin D supplementation in doses of 1600-4000IU/d are ongoing with glycemic control or incidence of diabetes mellitus as outcome. Vitamin D deficiency needs to be prevented or cured, but until the results of these trials are published, high-dose vitamin D supplementation cannot be recommended for prevention or amelioration of type 2 diabetes.

KEYWORDS:

Impaired fasting glucose; Impaired glucose tolerance; Insulin resistance; Type 2 diabetes; Vitamin D deficiency; Vitamin D supplementation; β-cell function

PMID:
27932304
DOI:
10.1016/j.jsbmb.2016.11.021
[Indexed for MEDLINE]

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