Effects of Hyperinsulinemia on Blood Pressure in High-FatDiet Fed Rats

摘要

Objective. To determine the mechanisms of hyperinsulinemia-induced elevation in blood pressure in rats. Methods. Male Sprague-Dawley rats were divided into normal diet (normal control) and high-fat diet group. After 36 weeks of feeding, high-fat diet group was further randomized into high-fat diet control group and streptozocin treatment group. Plasma insulin, endothelin-1(ET-1), norepinephrine (NE), aldosterone, and angiotensin II levels were measured. AT₁ receptor, ET-1, and ET_A receptor mRNA expression in the aorta was evaluated by real-time PCR. Results . After 9 months, systolic blood pressure (SBP) in high-fat diet group was higher than in the normal control group (155.4±1.6 vs.132.1±5.3 mmHg, P 1 receptor, ET-1 and ET_A receptors in the aorta in the high-fat diet group was greater than in the normal control group ( P <0.05). Streptozocin treatment reduced SBP by an average of 20.9±3.3 mmHg ( P <0.05), and reduced insulin level from 110.63±14.86 μ IU/mL to 39.45±6.59 μ IU/mL ( P <0.01). The streptozocin group also showed a higher level of urine sodium excretion, and a lower level of plasma ET-1 and NE than in the high-fat diet control group ( P <0.05). Conclusions. Hyperinsulinemia following high-fat diet is associated with an elevation in blood pressure. Sodium retention, increased plasma endothelin-1 and noradrenaline, as well as activation of renin-angiotensin system may all contribute to the blood pressure elevation.