INSULIN-LIKE GROWTH FACTOR-I AND LOW-DENSITY-LIPOPROTEIN CHOLESTEROL IN WOMEN DURING HIGH-FAT AND LOW-FAT FEEDING

In vitro studies suggest that insulin-like growth factor I (IGF-I) may modulate hepatic production and peripheral utilization of lipoproteins. We measured blood concentrations of IGF-I; total, high-density-lipoprotein, and low-density-lipoprotein (LDL) cholesterol; and apolipoproteins in 18 women with above average cholesterol after high- and low-fat diet periods. Total cholesterol fell 6% (P < 0.02) during the low-fat diet because of reduced concentrations of LDL cholesterol (P < 0.01). Serum concentrations of IGF-I were inversely correlated with total and LDL cholesterol and apolipoprotein B during both high-fat (r = -0.676, P < 0.005; r = -0.745, P < 0.001; and r = -0.504, P < 0.04, respectively) and low-fat (r = -0.656, P < 0.005; r- -0.757, P < 0.001; and r = -0.695, P < 0.001, respectively) diets. IGF-I increased with reduced fat intake in obese subjects only. Thus, IGF-I may contribute to the regulation of LDL cholesterol in mildly hypercholesterolemic women but may not mediate the beneficial response to reduced fat intake.