Effects of melatonin and zinc on glycemic control in type 2 diabetic patients poorly controlled with metformin.

OBJECTIVE This project was designed to evaluate the effects of melatonin and zinc on the glycemic control in type 2 diabetes mellitus (T2DM) patients with inadequate response to the oral hypoglycemic agent metformin. METHODS A placebo controlled, double-blind clinical trial was performed at the Specialized Center for Endocrinology and Diabetes, Al-Rusafa Directorate of Health, Baghdad, Iraq during the period from February to July 2005, in which 46 type 2 diabetic patients were selected and allocated into 3 groups, these groups were treated with single daily oral doses of both 10 mg melatonin and 50 mg zinc acetate alone; 10 mg melatonin and 50 mg zinc acetate in addition to the regularly used metformin or placebo, given at bed time for 90 days. We measured the fasting plasma glucose (FPG), glycated hemoglobin (HbA1C) and serum C-peptide before starting the treatment (zero time) and after 30 and 90 days of treatment. We also performed post-prandial glucose excursion test (PPGE) for selected patients from the second and third groups before starting the treatment and after 90 days. RESULTS Daily administration of melatonin and zinc improved the impaired fasting and post-prandial glycemic control and decreased the level of glycated hemoglobin; addition of this treatment regimen in combination with metformin improved the tissue responses to this oral hypoglycemic agent. CONCLUSION The combination of melatonin and zinc acetate, when used alone or in combination with metformin improves fasting and post-prandial glycemic control in T2DM patients.