Abstract 367: Insulin Resistance is Associated with Increased Sympathetic Activity and Decreased Baroreflex Function in Obese African American Women

Abstract

Obesity has a greater detrimental impact on the health of African American (AA) women than any other racial or gender group. Nearly 80% of AA women are overweight or obese and have higher incidence of insulin resistance compared to Caucasian women. The sympathetic nervous system (SNS) is increased in obesity and previous studies have reported that it may contribute to insulin resistance. However, most of these studies were performed in Caucasians. Thus, the contribution of the SNS to insulin resistance in African Americans remains unknown.The aim of this study was to determine if sympathetic activity is increased in obese AA women with insulin resistance. A total of 35 obese AA women with metabolic syndrome were studied (age 43±9 years, body mass index 38.7±5.5 Kg/m 2 , percentage body fat 48±4). Insulin sensitivity (SI) was evaluated by frequently sampled intravenous tolerance test and analyzed with Bergman's minimal model (MINMOD). Measurement of sympathetic regulation of vasomotor tone and baroreflex gain were determined with baroreflex-cross spectral analysis. Our results showed that SI was directly associated with baroreflex sensitivity, Figure. Subjects with insulin resistance (SI<3) had lower baroreflex sensitivity compared with those with normal SI (6.2±2.8 vs 10.4±4.5 ms/mm Hg, P=0.009). Subjects with insulin resistance tended to have elevated sympathetic activity as measured by low frequency variability of systolic blood pressure (LF SBP ; 5.9±3.4 vs 3.7±2.0 mm Hg 2 , P=0.057). In conclusion, insulin resistance is associated with decreased baroreflex gain and increased sympathetic activity in obese AA women.