Microvascular impairment is associated with insulin resistance in euglycemic mild hypertensives

Abstract BACKGROUND: Hypertension and diabetes are significantly associated with insulin resistance (IR), which could affect the vasodilatory capacity and microcirculation. The aim of the study was to verify whether IR is associated with a reduced microvascular blood flow in normoglycemic mild hypertensives. METHODS: Eighty-four untreated grade-1 hypertensives were equally divided, according to the IR homeostasis model assessment (HOMA) index, into three groups: IR-Low = 2.16 +/- 0.09 vs. IR-Medium = 3.77 +/- 0.09 vs. IR-High = 7.08 +/- 0.68 (P < 0.001) with similar sex distribution, office systolic blood pressure (SBP)/diastolic blood pressure (DBP) and history of hypertension. They underwent ambulatory blood pressure monitoring (ABPM) and a laboratory stress session, during which blood pressure (BP), heart rate (HR), and skin blood flow (Laser Doppler) were taken on the forehead (LDF) and the hand (LDH), where the neuroadrenergic control of the microvascular blood flow is higher. Reactivity was calculated as "area-under-the-curve" (AUC) during arithmetic and cold pressor tests. Postischemic LDH served as the index of endothelial microcirculatory damage. RESULTS: ABPM confirmed the diagnosis of hypertension, but IR-High patients showed a reduced nighttime BP fall. They also demonstrated reduced LDH-AUC and LDF-AUC although BP-AUC and HR-AUC reactivity were similar. Postischemic LDH was lower in the IR-High group (P < 0.05), and the postischemic LDH change was progressively impaired in both IR-Medium and IR-High patients (P < 0.001). LDH-AUC (-0.305, P = 0.007) and postischemic LDH at 30 s (-0.217, P = 0.059) and 60 s (-0.248, P = 0.030) during hyperemia were associated with HOMA. Multiple regression analysis, with HOMA as the dependent variable, showed that BMI (beta = 0.336, P < 0.001) and LDH (beta = -0.239, P < 0.001), LDH-AUC (beta = -0.296, P < 0.01) and postischemic LDH change (beta = -0.321, P < 0.001) entered the equation. CONCLUSIONS: The findings suggest that IR is associated with functional microvascular constrictive impairment in normoglycemic mild hypertensives.