Treatment of Insulin Resistance in Hypertensive, Obese Adolescents

Overview

In this study, we propose using telmisartan, an angiotensin II receptor antagonist with PPAR-gamma modulating activity, for a 12-week period to decrease blood pressure and insulin levels in obese, hypertensive children. Telmisartan is currently approved for treatment of adult hypertension. Recent adult studies, however, have shown telmisartan as an effective medication for lowering insulin levels and improving insulin sensitivity. We will enroll 30 obese adolescents, ages 10 to 18 years, and randomly assign half of the group to receive telmisartan and the other half to receive placebo (sugar-pill). We will obtain fasting glucose and insulin levels, as well as other markers for insulin sensitivity and cholesterol panel, at the beginning of the study, at each clinic visit in 4-week intervals, and at the end of the study. We will obtain an imaging study (computed tomography, CT scan) on 10 randomly selected study patients (5 from each group) to examine the distribution of fat tissue before and after treatment. Studies suggest that fat tissue in the subcutaneous tissue is less harmful that fat tissues surrounding internal organs, such as the liver. We will also provide nutritional handouts and exercise recommendations to each participant as a life-style intervention. Each participant will be given a diary to record his or her diet and exercise activities throughout the study.

Hypothesis: This pilot study will provide data essential for designing a larger trial to test the hypothesis that telmisartan treatment of obese children with insulin resistance and hypertension will result in improved insulin levels and systolic blood pressure. Secondary outcome measures will include the effects of telmisartan on total cholesterol, triglyceride, HDL and LDL levels, body mass index (BMI), and body fat distribution. Specific Aims for to Test Hypothesis: Aim #1: Determine the change in insulin sensitivity in adolescents with obesity and hyperinsulinemia before and after treatment with telmisartan. We hypothesize a significant increase in insulin sensitivity following medical treatment. We will measure fasting insulin and glucose levels for calculation of the homeostasis model assessment (HOMA) \[29, 30\]. Furthermore, we will calculate parameters of insulin production and insulin resistance from simultaneous measurements of glucose, insulin, and C-peptide levels during an oral glucose tolerance test (OGTT). We will check IGF BP-1 (insulin-like growth factor 1 binding protein) level as an indirect measurement of insulin resistance. Due to the risks associated with glucose clamps and continuous insulin infusion, we will not use this procedure in our study. Aim #2: Determine the change in systolic blood pressure in adolescents with obesity and hypertension before and after treatment with telmisartan. We hypothesize a significant decrease in systolic blood pressure following medical treatment. Subjects will have blood pressure checked at each clinic visit. Aim #3: Evaluate changes in lipid profile and body mass index as secondary outcome measures with telmisartan treatment. Subjects will have weight, height, and fasting lipid panel checked at each clinic visit. Aim #4: Characterize fat distribution before and after telmisartan treatment. A subset of study participants will undergo magnetic resonance imaging (MRI) to characterize and separate abdominal adipose tissue into its subcutaneous and visceral components. A one-slice MRI will be obtained at 2 time-points during the study (weeks 0 and 12). Aim #5: Determine the feasibility of using telmisartan for the treatment of hyperinsulinemia and hypertension in obese adolescents. Study results will provide necessary data to calculate the power needed for a multi-center, randomized, placebo-controlled trial of telmisartan.