Influence of vitamin D supplementation on glycemic control in type 2 diabetics.

INTRODUCTION: Several studies have suggested a benefic impact of vitamin D supplementation on glycemic control and insulin resistance among patients with type 2 diabetes mellitus. The aims of our study were to assess vitamin D status in individuals with type 2 diabetes mellitus and to investigate the effects of vitamin D supplementation on glycemic measures in patients having vitamin D deficiency. METHODS: We conducted a comparative prospective study involved 100 Tunisian patients with type 2 diabetes followed at the National Institute of Nutrition and Food Technology of Tunis. Glycemic control and insulin resistance were evaluated in the beginning of the study and three months after supplementation. RESULTS: Baseline mean 25-Hydroxy vitamin D  (25(OH)D) level was 17.5±9.8 ng/ml. Vitamin D status was deficient in 60%, insufficient in 26% and sufficient in 14% patients. After vitamin D supplementation, mean serum 25(OH)D concentration increased significantly (p˂10-3). We observed a negative correlation between the variation of plasma 25(OH)D level and the waist circumference's variation (r=-0.266 and p=0.018). This correlation persisted after adjustment for therapeutic management. Vitamin D supplementation did significantly improve neither glycemic control nor insulin resistance parameters. CONCLUSION: Vitamin D deficiency is frequent in patients with type 2 diabetes mellitus. The metabolic effects of supplementation are controversial, hence the need of expanding studies to better demonstrate these effects.

[Correlations between insulin sensitivity with anthropometric and metabolic parameters in type 2 diabetics]. / Étude de la corrélation entre la sensibilité à l'insuline et les paramètres anthropométriques et métaboliques dans le diabète de type 2.

AIM: The aim of the study was to evaluate correlations between insulin sensitivity and insulinosecretion with anthropometric and metabolic parameters in type 2 diabetics. MATERIALS AND METHODS: We conducted a cross-sectional study among patients with type 2 diabetes mellitus treated with oral antidiabetic medications. The evaluation of insulin resistance and insulinosecretion was based on the calculation of the HOMA-IR and HOMA-ß indices. RESULTS: The mean age for the 100diabetes recruited was 56.4±8.4years. The mean body mass index (BMI) and waist circumference (WC) were 30.5±5.7kg/m2 and 101.2±11.9cm respectively. The HOMA-IR and HOMA ß indices were respectively 3.5±2.8 and 48.9±45.5. We have found a significantly positive correlation between HOMA-IR index and weight (r=0.406, p<10-3), BMI (r=0.432, p<10-3) and WC (r=0.412, p<10-3). We noticed a significant negative correlation between HOMA ß index and fasting glucose (r=-0.457, p<10-3) and A1C (r=-0.399, p<10-3). A positive statistically significant correlation was noted between HOMA-IR and HOMA-ß (r=0.400, p<10-3). CONCLUSION: Insulin resistance is very related to overweight, especially the android distribution of fat hence the need for adequate management of this android obesity. It would also be interesting to evaluate the effects of weight loss on insulin resistance parameters.