Abstract P432: Racial Differences In Endothelial Function And Insulin Sensitivity

Abstract

Racial disparities in health outcomes continue to be a significant public health concern and African Americans (AA) are disproportionately burdened by several risk factors for cardiovascular disease. Endothelial dysfunction has been shown to be a predictor of CVD and metabolic factors, including insulin resistance, are associated with endothelial dysfunction. Compared to EA, AA have impaired endothelial function and are more insulin resistant (less insulin sensitive). However, it remains unclear how insulin resistance may contribute to endothelial dysfunction in AA and EA. The purpose of the present study was to evaluate the relationship between insulin sensitivity and endothelial function in AA and EA. It was hypothesized that insulin sensitivity would be associated with endothelial function in both AA and EA. Skeletal muscle insulin sensitivity was measured by hyperinsulinemic-euglycemic glucose clamp technique in 112 lean, overweight, and obese AA and EA adults without diabetes. Insulin was infused at 120 mU/m 2 /min for 3 hours and an infusion of 20% dextrose was adjusted to maintain blood glucose at the fasting level. Insulin sensitivity (10 -4 .dL.kg -1 .min -1 /(μU/mL)) was defined as M/(G x ΔI), where M is steady state glucose infusion rate, G is steady state serum glucose concentration, and ΔI is the difference between basal and steady state serum insulin concentrations. M was adjusted for total lean body mass which was measured by dual-energy X-ray absorptiometry (DXA). Endothelial function was assessed by percent change in flow-mediated brachial artery dilatation (FMD). Changes in brachial artery diameter during reactive hyperemia were measured using ultrasound. Increased blood flow was induced via blood pressure cuff around the forearm, with a 5-minute inflation at 50 mmHg above the subject’s systolic blood pressure. Brachial arterial flow was determined using a pulsed-Doppler signal at baseline and 10-15 seconds after cuff release. Arterial diameter was measured at end-diastolic phase from super-VHS recordings. For reactive hyperemia response, measurements with the 5 largest diameters were averaged and the percent increase from baseline was determined as FMD. A total of 55 AA and 57 EA were included in the analysis. Mean insulin sensitivity was 4.89 in AA and 7.97 in EA (p < .0001) and mean FMD was 10.69 in AA and 10.14 in EA (p = .595). Linear regression analysis indicated a significant relationship between insulin sensitivity and endothelial function in AA but not in EA (p= .005 and p= .5, respectively). These results suggest that insulin sensitivity may play a role in determining endothelial function in AA.