Hypertension in the diet induced obese rat is independent of body weight gain

Abstract

This study tested the hypothesis that the elevated mean arterial pressure (MAP) observed in the diet induced obese rats (DIO) on normal chow diet is associated with early life weight gain. A radiotelemetry transmitter was implanted in the femoral artery of 4 week old DIO and diet resistant (DR) rats for measurements of MAP and heart rate (HR) over a four week period. All rats were maintained on a normal diet. At 5 weeks, MAP was higher in DIO vs. DR rats (97±1 vs. 89±1 mm Hg, p<0.05), while body weight was not different (DIO: 133±5 gms and DR: 127±2 gms, p>0.05). At 9 weeks, MAP was still significantly elevated (DIO: 114±1 mmHg vs. DR: 103±1 mmHg), but the DIO rats weighed more than the DR rats (336±12 vs. 300±6 gms, p<0.05). At 9 weeks, there was no difference in plasma renin activity (4.0±0.6 vs. 3.5±0.6 ng/ml/hr, p>0.05), aldosterone (82±24 vs. 55±19 pg/ml, p>0.05) and leptin (3.0±0.2 vs. 3.4±0.4 pg/ml, p>0.05). MAP response to ganglionic blockade was similar between the two groups of rats (−43±2 vs. –37±2 mmHg). However, plasma insulin was significantly elevated in the DIO compared to the DR rats (DIO: 1.9±0.2 pg/ml vs. DR: 1.5±0.1 pg/ml). In conclusion, hypertension in DIO rats precedes an enhanced weight gain suggesting that genetic factors predetermine the hypertensive phenotype independent of body weight.