To clarify the prevalence of hyperinsulinemic subjects among young, nonobese, Japanese men, and to evaluate characteristics, in particular, of sympathetic nerve system activity and lipid fractions in hyperinsulinemic subjects.
Norepinephrine, plasma insulin, and lipid fractions were measured in 512 normotensive, 124 borderline hypertensive (BHT) and 88 established hypertensive (EHT) subjects, matched for age and body mass index, after they had fasted overnight.
Hyperinsulinemia defined as mean fasting plasma insulin + 2SD in normotensives or more was found in 8% of all subjects (normotensive and hypertensive subjects, P = 0.018), 6% of normotensives, 10% of BHT (P = 0.28, versus normotensives), 18% of EHT (P = 0.005, versus normotensives), and 12% of hypertensives (P = 0.019, versus normotensives). The hyperinsulinemic (fasting insulin ≥mean + 2SD in normotensive) subjects had higher plasma norepinephrine levels in all blood pressure groups than did nonhyperinsulinemic (< mean + 2SD) subjects (normotensives P < 0.05, BHT P < 0.01, and EHT P < 0.05). Hyperinsulinemic normotensives had higher blood pressure levels than did nonhyperinsulinemic ones (P < 0.05); however, blood pressure levels in hyperinsulinemic BHT and EHT were similar to those in nonhyperinsulinemic subjects. Triglyceride in BHT and EHT was greater than that in normotensives (P < 0.05), and that in hyperinsulinemic subjects was greater than that in nonhyperinsulinemic subjects (P < 0.05). On the other hand, high-density lipoprotein cholesterol in hyperinsulinemic BHT and EHT was significantly lower than that in nonhyperinsulinemic BHT (P < 0.05) and EHT (P < 0.01).
These results demonstrated that the prevalence of hyperinsulinemia among the present sample of young, nonobese, Japanese men was 12% and that the prevalence increased with blood pressure elevation. Furthermore, hypertriglyceridemia and sympathetic nerve hyperactivity appear to be related to hyperinsulinemia and the emergence of hypertension.