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

Abstract

endocrine regulator [ 5 ] . The active form of VD, 1α,25(OH) 2 D or calcitriol, is synthesised from precursor cholesterol by metabolic steps in skin, liver, and kidney. The primary metabolite, 25OHD, is the most abundant form of VD in blood and therefore established for measuring VD status. Various studies have shown an association of VD status and T2D [ 6 ] . Low 25OHD is found more often in patients with T2D [ 7 , 8 ] and correlates with a higher risk for T2D [ 6 , 9 , 10 ] . Furthermore, the 25OHD serum concentration is negatively associated with components of the metabolic syndrome, such as obesity, hyperglycaemia [ 11 -13 ] , and high body mass index (BMI) [ 9 , 14 -16 ] . Finally, many studies confi rmed an inverse correlation between 25OHD and parameters of insulin resistance: fasting glucose, glucose tolerance, insulin levels, and homeostasis model assessment-index (HOMA-I) [ 17 -24 ] . In addition, interventional studies showed benefi cial eff ects of VD on glucose status, insulin sensitivity, and insulin resistance [ 25 -27 ] . Introduction ▼According to the International Diabetes Federation, more than 300 million people worldwide are currently aff ected by diabetes mellitus ( http://www.idf.org/diabetesatlas/5e/the-globalburden ). A further increase of diabetes prevalence is expected, in particular due to the growing population in developing countries, the increasing industrialisation, urbanisation, and life style changes [ 1 , 2 ] . Diabetes pathophysiology is believed to result from environmental factors on a genetic background, but the causal genes remain complex and exert low hazard risk ratios [ 3 ] . The prevalence of type 2 diabetes (T2D) is infl uenced by multiple environmental factors, one of them may lie in the vitamin D system [ 4 ] . During recent years, vitamin D (VD), mainly known for its eff ects on bone and mineral metabolism, is growingly perceived as a pleiotropic

No Effect of High-Dose Vitamin D Supplementation on Glycemic Status or Cardiovascular Risk Factors in Subjects With Prediabetes

“…The majority of trials in subjects with type 2 diabetes have also not proven an effect of vitamin D supplementation on glucose metabolism (33)(34)(35). Of special interest is a recently published study in subjects with vitamin D deficiency (mean baseline serum 25(OH)D concentration 29.7 nmol/L) (36). A few trials in subjects with Iranian ethnicity and type 2 diabetes have suggested, on the other hand, a positive effect of vitamin D supplementation on glycemic outcomes; whether this is due to ethnicity or sociocultural differences remains unknown (37).…”

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

“…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.…”

A study to assess the effect of vitamin D supplementation on insulin resistance and glycaemic control in type 2 diabetes mellitus patients

“…While, there was a significant increase of 7.8% in fasting serum insulin and 10% in HOMA-IR in placebo group (p=0.032). 31 On the contrary, Witham etal did not observe any significant change in serum insulin levels and HOMA-IR with vitamin D supplementation. 32 This discrepancy might be because of different dosage and formulation of vitamin D used and small sample size of the study.…”