Calcium, Vitamin D and Metformin to Treat Insulin Resistance in Obese African American Adolescent Females

Overview

This is a feasibility study to examine the treatment with Metformin, vitamin D with calcium supplement for insulin resistance in obese, black, female teens. The association of low vitamin D levels and decreased insulin sensitivity has been established. Thus, the specific aims of this study are: Specific aim 1: To examine the effect of an 8-week treatment with vitamin D and calcium supplementations on diabetes-related risk factors in obese, black, female teens. Hypothesis 1a: In obese, black, female teens with both insulin resistance and vitamin D deficiency, treatment with vitamin D and calcium supplementation will significantly improve measures of insulin resistance and sensitivity (as determined by the homeostatic model assessment for insulin resistance and whole body insulin sensitivity index measures) when compared to controls not receiving vitamin D and calcium. Hypothesis 1b: In obese, black teen females with both insulin resistance and vitamin D deficiency, treatment with vitamin D and calcium supplementation will significantly improve measures of cardiovascular disease (decreased BMI and improved triglycerides and LDL) when compared to controls not receiving vitamin D and calcium. Specific aim 2: To determine if the addition of Metformin to the 8-week treatment with vitamin D and calcium supplementations improves diabetes-related risk factors in obese, black, female teens. Hypothesis 2a: In obese, black, female teens with both insulin resistance and vitamin D deficiency, treatment with Metformin, vitamin D, and calcium supplementation will significantly improve measures of insulin resistance and sensitivity (as determined by the homeostatic model assessment for insulin resistance and whole body insulin sensitivity index measures) when compared to standard of care or treatment with vitamin D with calcium supplementation alone while controlling for dietary intake of vitamin D and calcium. Hypothesis 2b: In obese, black, female teens with both insulin resistance and vitamin D deficiency, treatment with Metformin, vitamin D, and calcium supplementation will significantly improve measures of cardiovascular disease risk (as determined by the decreased BMI, improved triglycerides and LDL) when compared to standard of care or treatment with vitamin D with calcium supplementation alone while controlling for dietary intake of vitamin D and calcium.

The increasing rate of obesity in youth has reached epidemic proportion in the United States. African Americans share an overwhelming burden of this disorder and its complications.1 Vitamin D deficiency is prevalent in black girls and women2 and is associated with insulin resistance in populations at risk for diabetes.3 The use of Metformin, an oral diabetic agent, to halt the progression to diabetes in individuals at risk has been studied, but not in a population with concurrent vitamin D deficiency. In this proposal, we hypothesize that treatment with vitamin D with calcium supplement along with Metformin together will improve insulin resistance in obese, black teen girls. We will investigate this hypothesis in two specific aims to: 1) examine the effect of treatment of Vitamin D deficiency on insulin resistance in mature black teen girls, 2) to determine if there is any additional benefit of Metformin with treatment for Vitamin D deficiency to improve insulin resistance in this group. We propose to accomplish these aims through a clinical trial in obese black teen girls who have reached developmental maturity (approximately 15-18 years old) with vitamin D deficiency. Eligible participants will be randomized to one of three groups: standard of care, treatment with vitamin D/calcium supplement, and treatment with Vitamin D/Calcium Supplement and Metformin. We will enroll 30 obese adolescent subjects, (10 participants per group) into this 2-month study. The following measurements will be performed at baseline and 2 month follow-up: a) 25-hydroxy-vitamin D, b) Oral glucose tolerance tests to calculate homeostatic model assessment for insulin resistance (HOMA IR), and 4 to determine insulin resistance and total body insulin sensitivity index (TBISI) to determine insulin sensitivity,5 c) body mass index calculations, and c) lipid panel to include triglyceride, HDL-C, and LDL-C measurements. We will control for the effect of nutritional counseling on vitamin D and calcium intake will be controlled. Our outcome measures will include improvement in insulin resistance and decreased body mass index for our participants treated with vitamin D, calcium supplementation and Metformin. Validation of our hypothesis will show that Metformin along with vitamin D treatment and calcium supplementation is a novel treatment combination to improve insulin resistance, the health of an at-risk adolescent population.