Reduction of cardiac and aortic cholesterol in hypercholesterolemic rats fed esters of phytosterol and omega-3 fatty acids

Abstract

Sterol esters are currently gaining importance because of their recent recognition and application in the food and nutraceutical industries. Phytosterol esters have an advantage over phytosterols, naturally occurring antioxidants, with better fat solubility and compatibility. Antioxidants and hypocholesterolemic agents are known to reduce hypercholesterolemic atherosclerosis. The objective of the study was to determine the effects of different sterol esters on cardiac and aortic lipid profile and oxidative stress parameters and on the development of atherosclerosis in rats fed a high-cholesterol diet. Thirty six rats were divided into six groups: control group, hypercholesterolemic group and four experimental groups fed with EPA-DHA rich sitosterol ester in two different doses, 0.25 g/kg body wt/day and 0.5 g/kg body wt/day, and ALA rich sitosterol ester in two different doses, 0.25 g/kg body wt/day and 0.5 g/kg body wt/day. The sterol esters were gavaged to the rats once daily for 32 days. The cardiac and aortic total cholesterol, non-HDL cholesterol and triglyceride level which were elevated in hypercholesterolemia were significantly lowered by both the doses of sterol esters. Antioxidant enzyme activities were significantly decreased and peroxidation product, malondialdehyde was increased in hypercholesterolemia. But administration of both the sterol esters was able to increase enzyme activities and decrease MDA level in the tissues. Histological study of cardiac tissues showed fatty changes in hypercholesterolemic group which was reduced by treatment with sterol esters. The higher doses of sterol-ester caused better effects against hypercholesterolemic atherosclerosis.

Keywords: Antioxidant enzymes; Hypercholesterolemia; Lipid peroxidation; Phytosterol ester.

Fig. 1

Pictomicrographs of cardiac tissues a Control; b Hypercholesterolemic Control; c Low dose of EPA-DHA ester; d High dose of EPA-DHA ester; e Low dose of ALA ester; f High dose of ALA ester (200× magnification, scale bar = 100 μm for all the pictomicrographs) (↔-10 μm)

Fig. 2

Activity of antioxidant enzymes (a-GSH, b-GPx, c-SOD, d-CAT) in cardiac homogenate. Values are Mean ± S.E.M. of 6 rats. I-Control, II- Hypercholesterolemic (HCD), III- HCD + EPA-DHA Ester(25 mg/day), IV- HCD + EPA-DHA Ester(50 mg/day), V- HCD + ALA Ester(25 mg/day), VI- HCD + ALA Ester(50 mg/day) *p <0.05, Group I vs Groups II, III, V, VI; ^a p <0.05, Group I vs Group II, ^b p <0.05 Group II vs Groups III, IV,V, VI

Fig. 3

Activity of antioxidant enzymes (a-GSH, b-CAT, c-GPx, d-SOD) in aorta homogenate. Values are Mean ± S.D of 6 rats. I-Control, II- Hypercholesterolemic (HCD), III- HCD + EPA-DHA Ester(25 mg/day), IV- HCD + EPA-DHA Ester(50 mg/day), V- HCD + ALA Ester(25 mg/day), VI- HCD + ALA Ester(50 mg/day) ^a p <0.05, Group I vs Group II; ^b p <0.05, Group II vs Group IV, V, VI; ^c p <0.05 Group IV vs Group VI

Fig. 4

Cardiac tissue MDA in six groups. Values are Mean ± S.E.M. of 6 rats. I-Control, II- Hypercholesterolemic (HCD), III- HCD + EPA-DHA Ester(25 mg/day), IV- HCD + EPA-DHA Ester(50 mg/day), V- HCD + ALA Ester(25 mg/day), VI- HCD + ALA Ester(50 mg/day) *p <0.05, Group I vs Groups II, III, IV, V, VI; ^a p <0.05, Group I vs Groups II, ^b p <0.05 Group II vs Groups V, VI, ^c p <0.05 Group III vs Groups V, VI

Fig. 5

Aortic tissue MDA in six groups. Results are expressed as Mean ± S.E.M C-Control,H-Hypercholesterolemic(HCD),Ia-HCD + EPA-DHA Ester(25 mg/day),Ib-HCD + EPA-DHAEster(50 mg/day),IIa-HCD + ALA Ester(25 mg/day), IIb- HCD + ALA Ester(50 mg/day) ^a p <0.05, Group C vs Group H; ^b p <0.05, Group C vs Groups V, VI; ^c p <0.05, Group V vs Group VI