Óleo de coco virgem reduz o estresse oxidativo e melhora a sensibilidade do barorreflexo quando associado ao treinamento físico em ratos hipertensos

Abstract

The hypothesis that oral supplementation with virgin coconut oil (Cocos nucifera L.) and exercise training would improve impaired baroreflex sensitivity (BRS) and reduce oxidative stress in spontaneously hypertensive rats (SHR) was tested. Furthermore, the effects caused by lauric acid (LA) on oxidative stress and cardiovascular parameters in spontaneously hypertensive rats (SHR) were evaluated. In the first stage of the study, SHR and Wistar Kyoto rats (WKY) were used and divided in five groups: WKY + saline (n = 8); SHR + saline (n = 8); SHR + coconut oil (2 mL·day -1, n = 8); SHR + training (n = 8); and SHR + training + coconut oil (n = 8). The swimming protocol under 4% body weight workload lasted 60 minutes. Mean arterial pressure (MAP) was recorded and BRS was tested using phenylephrine (8 μg.kg-1, iv) and sodium nitroprusside (25 μg·kg-1, iv). Oxidative stress was measured using dihydroethidium by microscopy fluorescence in tissue sections from heart and aorta samples. SHR + coconut oil, SHR + training and SHR + training + coconut oil groups presented lower MAP compared to SHR + saline (148 ± 6, 147 ± 7, 134 ± 8 vs. 175 ± 6 mmHg, P < 0.05). Coconut oil combined with exercise training improved BRS in SHR compared with SHR + saline group (-2.47 ± 0.3 vs. -1.39 ± 0.09 ± bpm-1·min-1·mmHg, p <0.05). SHR + saline group showed higher superoxide levels when compared with WKY + saline (774 ± 31 vs. 634 ± 19 arbitrary units (AU), respectively; p <0.05). SHR + training + coconut oil group presented a reduction in oxidative stress compared with SHR + saline in heart (622 ± 16 vs. 774 ± 31 AU, p <0.05). Moreover, coconut oil reduced oxidative stress in SHR compared with SHR + saline in aorta (454 ± 33 vs. 689 ± 29 AU, p <0.05). In the second stage of thestudy, LA reduced blood pressure at 3, 4, 8 and 10 mg/kg doses compared with vehicle (-41±9.4;-41±6;-51.7±8.1;-61±11 vs. -1,3±0.4 mmHg, n = 6). LA (10-8 to 3x10-3M) induced vasorelaxation in isolated cranial mesenteric artery rings in the presence or absence of functional endothelium (Emax=104,1 ± 2,8% e pD2= 4,1 ± 1,4; n=7 vs. Emax= 103,5 3,7 pD2 = 3,3 ± 0,5; n=8, respectively). LA (10-3 M) reduced superoxide levels similar to Tempol, a superoxide anion scavenger, compared to tissue containing only NADPH oxidase in the heart (18.1 ± 0.7; 9.5 ± 0.3 vs. 25.3 ± 0.4 UML / min / ug protein, respectively) and kidney (81.9 ± 2.8, 79 ± 1.3, 99 ± 4.3 vs. UML / min / ug protein, respectively). In conclusion, coconut oil combined with exercise training reduced oxidative stress and improved BRS in SHR. Those effects seem to be, at least in part, to its major component (Lauric acid).