Cardiovascular correlates of insulin resistance in normotensive and hypertensive African Americans (Hemodynamic correlates of insulin resistance)

摘要

Insulin resistance (IR) is associated with obesity and predisposes to diabetes mellitus (DM), and cardiovascular disease (CVD). The purpose of this study is to determine if IR is related to cardiovascular function independent of DM or hypertension among African Americans (AA). 462 non-diabetic AA (50% hypertensive and 51% women) were studied on an inpatient GCRC. Measurements included anthropometrics, and 24 hour blood pressure (BP), heart rate (HR), fasting blood glucose, plasma aldosterone and insulin. Stroke volume (SV) and cardiac output (CO) were measured by impedance plethysmography; peripheral vascular resistance (PVRI) and vascular compliance indices (VCI) were computed. These measurements were also obtained in response to mental (computerized math testing) and pharmacologic (graded norepinephrine infusion) stress. IR was calculated using homeostasis model assessment (HOMA-IR). SV, CO and VCI decreased with increasing HOMA-IR whereas HR and PVRI increased. Overall, BP, HR, and PVRI were positively correlated with HOMA-IR (p<0.01); and SV index, cardiac index, and VCI were negatively correlated with HOMA-IR (p<0.0001). The correlations persisted after adjustment for BP, age, gender, plasma aldosterone and total, or LDL and HDL-cholesterol. In addition, multiple linear regression analyses showed that HOMA-IR contributes to the maximum variability of all the hemodynamic variables. BP responses to math stress and norepinephrine infusion did not correlate with HOMA-IR. Unrelated to DM and BP, IR is associated with increased PVRI and decreased CO in AA. These observations suggest that an exclusive focus on effects of IR on DM or BP may ignore independent pathophysiologic contributions of IR to CVD.