Relationship of insulin resistance to macro- and microvasculature reactivity in hypertension

Although insulin resistance (IR) is thought to be related to vascular dysfunction, the difference in the relationship of IR to microvasculature and macrovasculature reactivity has not yet been clarified. The present study was conducted to clarify whether the IR is more closely related to the macrovasculature reactivity (flow-mediated vasodilatation of the brachial artery induced by reactive hyperemia: FMD) or microvasculature reactivity (skin reactive hyperemia as assessed by laser Doppler flowmetry: SRH) in patients with hypertension.

In 75 consecutive hypertensive patients (61 +/- 11 years of age) without obvious cardiovascular (CV) disease and/or risk factors for CV disease other than hypertension, FMD, SRH, and homeostasis model assessment index of IR (HOMA(IR)) were measured.

No significant relationship was observed between FMD with the parameters of SRH. In the univariate linear regression analysis, HOMA(IR) showed a significant correlation with the FMD (R(2) = 0.05, P < 0.05), but not with the parameters of SRH. Multivariate linear regression analysis demonstrated a significant association between HOMA(IR) and FMD, even after adjustments for covariates, including the use of medication for hypertension. (R(2) = 0.32, beta = -0.29, P = 0.02).

The complication of IR in hypertensive patients without obvious CV disease/risk factors may be related to impaired macrovasculature rather than microvasculature reactivity, apart from the influence of antihypertensive medication on the reactivity of the vasculature and insulin sensitivity.