Alterações cardiovasculares e hidro-eletrolíticas induzidas por dieta hiperlipídica

Abstract

Obesity has been pointed out as a worldwide epidemic. Data from the literature show that obesity can promote cardiovascular diseases such as hypertension, and the increased activity of the renin-angiotensin system (RAS) has been described as facilitating obesity-induced hypertension. In addition, RAS is also involved in hydroelectrolyte balance adjustments, and thus helping to regulate blood pressure. Therefore, the aims of the present study were, 1) to verify the changes in blood pressure and water intake induced by central ANG II in rats fed with a high-fat diet (HFD) diet; 2) to verify the participation of the AT1 receptors in the forebrain in the alterations of arterial pressure observed in rats fed with HFD; 3) to verify the daily water intake and urinary excretion, as well as the prandial consumption of water in rats fed with HFD. We used male Holtzman rats (290-320 g) that were fed a standard diet (DP, 5% calories from fat) or DH (45% calories from fat) for 6 weeks prior to testing. The experiments were performed between the 6th and 7th week after the onset of HFD. Part of the animals received a stainless steel cannula in the lateral ventricle (LV) at the 6th week after the beginning of the diets and the experiments were performed at week 7. We observed that the pressor effect, but not the dipsogenic response to the icv injection of ANG II, was potentiated in the HFD rats. The highest levels of basal blood pressure found in HFD rats were reversed by injection into the LV of losartan (angiotensin receptor antagonist of the subtype AT1). We also observed that daily water intake and urinary volume were significantly reduced in rats with DH, with no significant changes in sodium excretion. There was also a reduction in prandial water consumption. These results show that HFD rats have a potentiated pressor response to central ANG II without altering the dipsogenic response of ANG II and AT1 prosencephalic receptors appear to be involved in obesity-induced hypertension. Finally, HFD rats showed a reduction in daily water consumption, due to mechanisms still to be clarified, and the reduction in urinary volume seems to be related to this.