Positive association between circulating free insulin-like growth factor–1 levels and coronary flow reserve in arterial systemic hypertension

Abstract Background The reduction of coronary flow reserve (CFR) found in arterial hypertension may be due to changes in afterload, left ventricular (LV) structure, and metabolic factors. Also, insulin-like growth factor–1 (IGF-1) may be associated with the magnitude of CFR in relation to its modulating action on cardiac and endothelial function. Methods A total of 44 newly diagnosed, untreated hypertensive patients, who were free of diabetes mellitus and coronary artery disease, underwent M-mode analysis, second-harmonic Doppler echocardiographic assessment of CFR (dipyridamole infusion 0.56 mg/kg intravenously in four patients), determination of circulating free IGF-1, and insulin resistance. Based on CFR levels, hypertensive subjects were divided into two groups: 18 with normal CFR (≥2) and 26 with impaired CFR (<2). Results Patients with normal CFR had lower diastolic blood pressure, heart rate, and LV mass index but higher free circulating IGF-1 than patients with reduced CFR (P< .001). Insulin resistance was not significantly different between the two groups. In a first multilinear regression analysis that included demographic and echocardiographic variables, insulin resistance was independently associated with CFR (standardized β COEFFICIENT = −0.31, P< .05) in the overall population. However, in a subsequent model which included also IGF-1, the relationship between insulin resistance and CFR disappeared, whereas IGF-1 was the main independent determinant of CFR (β = 0.51, P< .0002). Conclusions Free IGF-1 circulating levels are independently associated with CFR in hypertensive individuals free of overt coronary artery disease. A possible beneficial effect exerted by IGF-1 on coronary blood flow may be supposed in arterial hypertension.