Development of hypertension in a rat model of diet-induced obesity

Although obesity is a risk factor for hypertension, the relationship betwee n these 2 conditions is not well understood. Therefore, we examined same pa rameters of hypertension and cardiovascular disease in a dietary model of o besity. Male Sprague-Dawley rats were provided either a control diet (C) or a diet containing 32% kcal as fat (similar to a Western diet) for 1, 3, or 10 weeks. Rats in the latter group diverged based on body weight gain into obesity-prone (OP) and obesity-resistant (OR) groups. Systolic blood press ure in OP rats was significantly higher after 10 weeks of the diet (149+/-4 .8 mm Hg) compared with both OR and C groups (131+/-3.7 and 129+/-4.5 mm Hg , respectively). The aortic wall area of OP rats was significantly increase d, indicating arterial hypertrophy, and a 2-fold increase in plasma renin a ctivity was found in OP rats compared with OR and C rats. The lipid profile showed a significant increase in plasma and VLDL triglycerides of OP versu s OR and C groups as early as 3 weeks on the diet. Plasma and LDL-cholester ol levels were increased in the OP group versus the OR and C groups after 3 weeks of the diet, but the difference was blunted after 10 weeks. Lipid pe roxidation (thiobarbituric acid-reactive substances) in OP rats was increas ed 2-fold in LDL and 1.5-fold in aortic wall compared with OR rats, suggest ing an increased oxidative stress in these animals. Periodic acid-Schiff st aining of the kidney showed mesangial expansion and focal sclerosis that we re more prominent in OP rats than in OR rats. The results suggest that hype rcholesterolemia, but not hypertriglyceridemia, is linked to the diet; that hypertension and renin-angiotensin system activation are associated with o besity; and that lipid peroxidation and renal damage are the results of bot h factors.