Interactive relation of insulin and gender to cardiovascular reactivity in healthy young adults.

High levels of insulin may promote hypertension pathogenesis, in part, via enhanced sympathetic nervous system (SNS) activity. This study examined potential interactive relations of fasting insulin levels, gender, and race to cardiovascular reactivity-a correlate of SNS activation. Hemodynamic responses to 4 laboratory challenges were determined by impedance cardiography in 64 healthy young adults (ages 18-26; 48% male; 50% White, 50% African American). Also examined were lipoprotein lipids, central and total adiposity, self-reported dietary factors, and physical activity. High-insulin (>10.2 mU/ml) men showed greater total peripheral resistance and longer pre-ejection period responses than low-insulin ( pound 10.2 mU/ml) men. High-insulin women displayed greater cardiac index responses than high-insulin men. High insulin levels were related to greater percentage body fat, dietary carbohydrate and fat intake, lower high-density lipoprotein (HDL) cholesterol (in men), higher total cholesterol (in women), and a trend toward higher triglycerides. Cardiovascular reactivity findings were unchanged after statistical adjustment for total and HDL cholesterol, triglycerides, percentage body fat, dietary carbohydrates, and fat. The Gender x Insulin (continuous scores) interaction accounted for 7% and 9% of the variance in cardiac index and total peripheral resistance responses, respectively. These results indicate that high insulin levels are associated with greater vascular reactivity in young men and cardiac reactivity in young women. Enhanced cardiovascular reactivity may constitute a biobehavioral dimension of the metabolic syndrome.