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Copyright ©The Author(s) 2015. Published by Baishideng Publishing Group Inc. All rights reserved.
World J Diabetes. Jul 25, 2015; 6(8): 1057-1064
Published online Jul 25, 2015. doi: 10.4239/wjd.v6.i8.1057
Is there a relationship between vitamin D with insulin resistance and diabetes mellitus?
Kamal AS Al-Shoumer, Thamer M Al-Essa
Kamal AS Al-Shoumer, Division of Endocrinology and Metabolic Medicine, Department of Medicine, Faculty of Medicine, Kuwait University, 13110 Safat, Kuwait
Kamal AS Al-Shoumer, Thamer M Al-Essa, Division of Endocrinology and Metabolic Medicine, Department of Medicine, Mubarak Al Kabeer Hospital, 46304 Jabriya, Kuwait
Author contributions: Both authors contributed to this work.
Conflict-of-interest statement: No conflict of interest of any kind.
Open-Access: This article is an open-access article which was selected by an in-house editor and fully peer-reviewed by external reviewers. It is distributed in accordance with the Creative Commons Attribution Non Commercial (CC BY-NC 4.0) license, which permits others to distribute, remix, adapt, build upon this work non-commercially, and license their derivative works on different terms, provided the original work is properly cited and the use is non-commercial. See: http://creativecommons.org/licenses/by-nc/4.0/
Correspondence to: Kamal AS Al-Shoumer, MD, FRCP, PhD, FACE, Professor and Consultant, Head, Division of Endocrinology and Metabolic Medicine, Department of Medicine, Faculty of Medicine, Kuwait University, PO Box 24923, 13110 Safat, Kuwait. kshoumer@gmail.com
Telephone: +965-25-319596 Fax: +965-25-313511
Received: December 7, 2014
Peer-review started: December 9, 2014
First decision: January 8, 2015
Revised: April 17, 2015
Accepted: May 5, 2015
Article in press: May 6, 2015
Published online: July 25, 2015
Abstract

Available data suggest a possible link between abnormal vitamin D level and abnormal glucose homeostasis, two of the most common chronic medical conditions. Both conditions are associated with inflammation, and the exact mechanism for role of either on the other is not well clear. Literature investigating the link between vitamin D and either pre-diabetic states or diabetes is reviewed. Vitamin D deficiency is detrimental to insulin synthesis and secretion in animal and human studies. In humans, it has been shown by majority of observational studies, that vitamin D is positively correlated with insulin sensitivity and its role is mediated both by direct mechanism through the availability of vitamin D receptors in several tissues and indirectly through the changes in calcium levels. Large number of, but not all, variable samples cross sectional human trials have demonstrated an inverse relation between vitamin D status and impaired glucose tolerance, insulin resistance or diabetes. To compliment this conclusively, evidence from intervention studies is critically warranted before we can frankly state that vitamin D plays a role in diabetes prevention or treatment. Absence of both sizable prospective observational trials utilizing 25(OH)D as the main variable and the non-availability of randomized studies specifically designed to assess the effects of vitamin D on pre-diabetes and diabetes states, are the main obstacles to draw solid and conclusive relationships.

Keywords: Vitamin D, Insulin resistance, Type 2 diabetes

Core tip: A potential role for abnormal vitamin D level in changes of glucose homeostasis has been described. It has been demonstrated that deficient vitamin D status is detrimental to the synthesis and secretion of insulin in animal and human studies. In several, but not all, human observational trials, an inverse correlation was seen between vitamin D with insulin insensitivity, pre-diabetic states and dysglycemia. However, evidence from randomized interventional studies assessing the effects of changes in vitamin D status on markers of dysglycemia and diabetes prevention is not available. Therefore, firm and true protective influence of vitamin D on glucose homeostasis remains to be defined.