Abstract
African-Americans have more hypertension, stroke, and type 2 diabetes than do Caucasians. Endothelial dysfunction and insulin resistance are precursors for each. Since these diseases have origins in pediatrics and are associated with obesity, this study was designed to determine if obesity has different effects on endothelial function, insulin sensitivity, and secretion in African-American and Caucasian adolescents. Thirty-three Caucasian and 25 African-Americans (10–18 years old) were subdivided by BMI into lean, overweight, and obesity groups. Endothelial function was measured as forearm vascular resistance (FVR) over 1 min following 5 min of upper arm vascular occlusion. Insulin sensitivity and secretion were measured using intravenous glucose tolerance test and minimal model. Postocclusive FVR was significantly increased in obese African-Americans. Insulin sensitivity was reduced in obese subjects but did not differ by race. Insulin secretion was increased in African-Americans but did not differ by obesity. Subjects were subdivided into risk groups based on 20th percentile for postocclusion FVR response in lean. Seven of nine obese African-Americans were in the high risk group compared to 0 of 5 obese Caucasians. These results demonstrate that obesity significantly impairs endothelial function in African-Americans. Endothelial dysfunction likely predisposes to future cardiometabolic disease in obese African-American adolescents.
Highlights
African-Americans have increased incidence of and mortality from cardiometabolic diseases, including stroke [1,2,3], hypertension [4], and type 2 diabetes [4,5,6]
There was a trend toward increased LDL cholesterol in the combined nonobese high risk group (106 ± 3 versus 92 ± 4 mg/dL; P = 0.079). These results demonstrate that obesity has a greater impact on endothelial function in African-American adolescents than in Caucasian adolescents
Postocclusive forearm vascular resistance (FVR) was increased and percent change in FVR was significantly decreased only in the obese African-American group compared nonobese African-American and obese Caucasian adolescents. This is further emphasized by the fact that 7 of 9 obese African American adolescents had endothelial function below the 20% for lean subjects while none of the 5 obese Caucasians were in the high risk group
Summary
African-Americans have increased incidence of and mortality from cardiometabolic diseases, including stroke [1,2,3], hypertension [4], and type 2 diabetes [4,5,6]. Hypertension, stroke, type 2 diabetes, and myocardial infarction are frequent outcomes of obesity and the metabolic syndrome. Their increased frequency in African-Americans is surprising since the metabolic syndrome is less common in AfricanAmericans than in Caucasians [4]. This raises the question of whether there are racial differences in obesity’s effects on nontraditional cardiometabolic risk factors that are not part of the metabolic syndrome. Diminished endothelial function decreases insulininduced vasodilation and glucose delivery to and usage by muscle tissue and predisposes to insulin resistance, and type 2 diabetes, and other cardiometabolic diseases. Hinderliter et al [15, 16] found higher minimum forearm vascular resistance (FVR) following vascular occlusion in African-American, young adults than in similar aged, Caucasian subjects
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