Evidence for Sympathetic Origins of Hypertension in Juvenile Offspring of Obese Rats

Abstract

Maternal obesity in rodents is associated with increased adiposity, impaired glucose tolerance, and hypertension in adult offspring. In this study we investigated the influence of maternal obesity in the rat on blood pressure and blood pressure regulatory pathways in juvenile and adult offspring. Obesity was induced before pregnancy in female Sprague-Dawley rats by feeding a highly palatable energy-dense diet. In juvenile animals (30 days of age), before the onset of obesity and hyperleptinemia, basal nighttime mean arterial pressure was significantly raised in the offspring of obese dams (OffOb) relative to offspring of controls (OffCon; mean arterial pressure, males: OffOb, 121.8+/-0.6 mm Hg versus OffCon, 115.0+/-0.5 mm Hg, n=6, P<0.01; females: OffOb, 125.4+/-0.4 mm Hg versus OffCon, 114.4+/-0.5 mm Hg, n=6, P<0.001), as was the mean arterial pressure response to restraint stress (P<0.01). The pressor response to a leptin challenge was enhanced in OffOb rats (Deltamean arterial pressure: OffOb, 9.7+/-0.8 mm Hg versus OffCon, 5.3+/-1.3 mm Hg; n=8; P<0.05). Renal tissue norepinephrine content (P<0.001) and renin expression (P<0.05) were markedly raised. Analysis of heart rate variability revealed an increased low:high frequency ratio in OffOb versus OffCon rats (P<0.05). At 90 days, hypertension in OffOb rats persisted and was abolished by alpha1- and beta-adrenergic blockade, and cardiovascular responses to phenylephrine or sodium nitroprusside indicated altered baroreceptor function. The exaggerated pressor response to leptin in OffOb rats was maintained. Hypertension in the offspring of obese rats may arise from persistent sympathoexcitatory hyperresponsiveness acquired in early stages of development.