Effect of high doses of vitamin D on arterial properties, adiponectin, leptin and glucose homeostasis in type 2 diabetic patients

MANAGEMENT OF ENDOCRINE DISEASE: The effect of vitamin D supplementation on glycaemic control in patients with type 2 diabetes mellitus: a systematic review and meta-analysis

“…Of the 23 studies that were included in the systematic review, 13 reported fasting glucose as primary or secondary outcome measure (19,20,21,22,23,24,26,27,28,32,35,36,39). Three studies reported a significant reduction in fasting glucose level after vitamin D supplementation (21,28,39).…”

“…Thirteen studies reported data on insulin resistance, of which twelve studies used the HOMA-IR to quantify insulin resistance (19,20,21,22,24,25,26,29,30,35,36,39), and one study measured insulin resistance through hyperinsulinaemic-euglycaemic clamp method (23). Two studies observed a significant reduction in insulin resistance after vitamin D supplementation (21,39), and one study found a negative effect of vitamin D supplementation on insulin resistance compared with placebo (35).…”

“…The quality assessment of the studies resulted in 14 out of 23 studies having a good quality (Appendix 1, see section on Appendix given at the end of this article) (12,19,20,21,22,23,24,25,26,27,28,29,30,31). The main characteristics and main outcomes of the included studies are given in Table 1.…”

“…The main characteristics and main outcomes of the included studies are given in Table 1. All studies had a randomized controlled trial design, of which 18 studies used a placebo for control (12,19,20,22,23,24,25,27,29,30,31,32,33,34,35,36,37,38), three studies compared vitamin D fortified yoghurt versus plain yoghurt (21,28,39), one study used oral calcium supplementation for control (26), and one study used vitamin C supplementation for control (40). Apart from two studies, which solely included post-menopausal women (21,33), all studies included both men and women.…”

Effect of a Randomised Controlled Vitamin D Trial on Insulin Resistance and Glucose Metabolism in Patients with Type 2 Diabetes Mellitus

“…Although the trial failed to meet endpoints for improved insulin and C-peptide secretion as well as HOMA-index, the correlation of BMI, HbA1c, insulin levels, and the vitamin D status suggests that glucose homeostasis may be positively regulated by vitamin D. The paradox observation that diff erences were more signifi cant at 6 months of therapy in the placebo group suggests that either the chosen dose is insuffi cient or that other factors regulate vitamin D's metabolic eff ects. A recent placebocontrolled trial with 47 diabetic patients and a lower daily dose (1 000 IU/d) demonstrated no metabolic eff ects but a nonsignificant increase in adiponectin and a signifi cant improvement of aortal stiff ness [ 42 ] . Physiologic and metabolic improvement may be due to direct or indirect VDR-mediated musculoskeletal, hepatic or eff ects on pancreatic β-cell secretion.…”