Plasma lipid profile of experimentally induced hyperlipidemic New Zealand white rabbits is not affected by resveratrol.INTRODUCTION
Presently, cardiovascular diseases are the main causes of morbidity and mortality Morbidity and Mortality can refer to:
pertaining to the muscular tissue of the heart (the myocardium). infarcts and brain vascular accidents. (4) Hyperlipidemia is recognized as an important risk factor to atherosclerosis, and most evidence focuses specifically on hypercholesterolemia. LDL, its main component, is most universally associated to an increased risk of cardiovascular diseases. (4)
Dietary antioxidants have attracted considerable attention as preventive and therapeutic agents. In vivo and in vitro studies using animal models show that the consumption of antioxidants can prevent and delay atherosclerosis progression. Resveratrol res·ver·a·trol
A natural compound found in grapes, mulberries, peanuts, and other plants or food products, especially red wine, that may protect against cancer and cardiovascular disease by acting as an antioxidant, antimutagen, and seems to play an important role in atherosclerosis prevention in human subjects through its inhibitory effect on LDL oxidation, platelet aggregation, and vascular proliferation of smooth muscle cells. (1,6) The hypocholesterolemic action of resveratrol is attributed, at least in part, to an increased excretion of neutral sterols and bile acids into feces. However, there are conflicting results regarding its effects on plasma lipid levels, since some studies have failed to show a reduction in plasma lipid levels induced by such a substance. (20)
The aim of the present study was to evaluate plasma LDL, high-density lipoproteins (HDL), triglycerides, and total cholesterol in experimentally hypercholesterolemic New Zealand white rabbits treated with resveratrol.
MATERIALS AND METHODS
Twenty healthy male adult New Zealand white rabbits whose mean weight was 2.5 kg were used on the study, which was conducted from March 15 to May 15, 2007. The animals were previously fed with regular rabbit ration during one week. Afterwards the animals were divided into four experimental groups containing five animals each, with the following feeding protocol: blank control group (CT) received maintenance diet (a); group R received maintenance diet with simultaneous oral administration of resveratrol (b) (3 mg/kg/day) (a); group CL received 1.5% cholesterol (c) added to the maintenance diet; and group CR received 1.5% cholesterol added to the maintenance diet and simultaneous oral administration of resveratrol (b) (3 mg/kg/ day). For the preparation of hypercholesterolemic diet, a cholesterol powder (b) was added to the previously grounded maintenance diet, mixed, pelleted, and stored at refrigerated units. The dose of resveratrol used was based in previous studies. (19) During the experiment, each animal received daily water ad libitum and 100 g of diet. The experiment was performed under approval of Animal Welfare and Ethics Committee of Universidade Estadual Paulista, Campus de Jaboticabal--UNESP.
Samples of 3 mL of heparinized blood were collected twice monthly from the central ear artery, with the ani mals kept in restraint cages. Those blood samples were used for plasma level determinations of triglycerides, total cholesterol, HDL, and LDL, through enzymatic methods (c), accomplished in Department of Veterinary Clinics and Surgery Laboratory, Campus de Jaboticabal, UNESP HDL levels were measured through selective inhibition technique, while total cholesterol, triglycerides, and LDL through enzymatic / Trinder method. All analytic procedures were made in triplicates. During the experimental period, the animals were weighed on a weekly basis for the adjustments of doses of resveratrol.
Statistical analysis was performed using Statistical Analysis Software (SAS) (d). The results were analyzed through analysis of variance (ANOVA anova
see analysis of variance.
ANOVA Analysis of variance, see there ). A Duncan's test was employed to compare means. A P<0.05 value was considered significant.
Mean values [+ or -] standard deviation of plasma lipid profile obtained in this study are expressed in the Table 1. The values of HDL, LDL, triglycerides, and total cholesterol indicate that the control group was different (P<0.05) from CL and CR groups, but not from R group.
The results obtained in lipid measurements on the first day of the experimental period were similar to all groups. No alterations in plasma lipid profile of the animals fed with regular diet were detected when the values obtained in the beginning and in the end of the experiment were compared, not even in CR group, which showed similar values to CT group in the end of the experiment. Nevertheless, there was a significant increase in total cholesterol, triglycerides, LDL, and HDL in those animals submitted to a hypercholesterolemic diet.
Epidemiological studies show a decreased risk of cardiovascular diseases with the intake of high amounts of polyphenolic substances. Thus, resveratrol contributes with the antioxidant potential and plays an important role in cardiovascular disease prevention in human subjects. The protective effects of resveratrol have been attributed to a number of mechanisms such as antioxidant, anti-inflammatory, anti-proliferative, and anti-thrombotic activities, as well as its hypolipidemic properties. Therefore, considering its antioxidant effects, early studies have proven that polyphenols from red wine were able to reduce plasma oxidation of LDL. (18) A fat-enriched meal prejudices endothelial function for more than four hours, being more severe in coronary disease patients. (22) Such a dysfunction is mainly attributable to an increase in endothelial oxidative stress, which is inhibited by wine antioxidants.
When the in-vitro effects of transresveratrol, some wine-derived phenol compounds, and some antioxidants were studied, a blockage in platelet aggregation and eicosanoid ei·co·sa·noid
Any of the physiologically active substances derived from arachidonic acid, including the prostaglandins, leukotrienes, and thromboxanes. synthesis in human cells was observed, contributing to the cardioprotective effect of resveratrol, mainly against atherosclerosis in coronary disease patients." The beneficial effect of resveratrol on endothelial integrity through an inhibition in VCAM-1 (Vascular Cell Adhesion Molecule 1),ICAM-1 (Intracellular Adhesion Molecule 1), and transcription factor NF- i, (Nuclear Factor Kappa ?) expression, the latter being responsible for pro-inflammatory modulatory mechanisms, is also documented. (5,9,21)
In the present experiment, groups CL and CR shared similarities to all variables studied, although differing from groups CT and R, which were similar. HDL values remained in the species reference range in all groups, only a slight increase being observed in CL and CR groups. LDL, triglycerides, and cholesterol, as expected, reached high levels in hypercholesterolemic groups, but remained in the reference range in CT and R groups, without differing among them.
The analysis of the findings allowed to infer that the use of resveratrol during the experimental period did not affect LDL, HDL, triglycerides, and cholesterol levels, similar to early studies. (17,19,20) Opposite to this evidence, some researchers detected changes in lipid profile induced by different flavonoids flavonoids,
n.pl common plant pigment compounds that act as antioxidants, enhance the effects of vitamin C, and strengthen connective tissue around capillaries. (3,8,10,11,16) and vitamin E (7,15) in various species. Furthermore, a synergic effect between statins and resveratrol was observed in hypercholesterolemic rats, leading to a significative sig·nif·i·ca·tive
1. Tending to signify or indicate; indicative.
2. Having meaning; significant.
sig·nif reduction in total plasma cholesterol, triglycerides, and LDL. (12,14) The use of an analogue of resveratrol (pterostilbene) in hypercholesterolemic hamsters showed a 29% reduction in plasma LDL and a 7% increase in plasma HDL.
In conclusion, resveratrol at 3 mg/kg/day did not show hypolipidemic activity in rabbits experimentally hypercholesterolemic, used as experimental model in atherosclerosis.
Sources of Manufacturers
a. Purina Paulinica, Sao Paulo, Brazil.
b. Vetec Duque de Caxias, Rio de Janeiro, Brazil.
c. LABTEST DIAGNOSTICA S.A, Minas Gerais, Brazil.
d. SAS, Statistics Software v2, version 6.08, Cary, NC.
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Marines de Castro (1)
Angela P M. Veiga
Maria R. Pacheco
From the Sao Paulo State University, Jaboticabal, SP, Brazil (de Castro, Pacheco) and the Federal University of Rio Grande The University of Rio Grande and Rio Grande Community College are twin colleges in Rio Grande, Ohio.
The University of Rio Grande offers a range of courses and majors and is known in the region for its Education and Nursing programs. do Sul, Porto Alegre, RS, Brazil (Veiga).
(1) Corresponding Author: Marines de Castro, Universidade Estadual Paulista (UNESP), Faculty of Agricultural and Veterinary Sciences, Department of Morphology, Via de Acesso Prof Paulo Donato Castellane, s/n, Jaboticabal, Sao Paulo, Brazil 14884-900. Tel: + 55 15 32092654; fax: +55 15 32035150; e-mail: email@example.com.
Table 1--Lipid profile (mg/dl) in rabbit fed a normal (CT and R) or high cholesterol diet (CL and CR) during 60 days, with or without supplementation of resveratrol. Total Chol (mg/dL) LDL (mg/dL) Groups M SD M SD CT 47.03 (b) [+ or -] 15.84 14.88 (b) [+ or -] 20.12 R 49.51 (b) [+ or -] 17.09 12.99 (b) [+ or -] 17.38 CL 950.94 (a) [+ or -] 662.90 872.74 (a) [+ or -] 639.57 CR 1508.50 (a) [+ or -] 889.71 1407.26 (a) [+ or -] 850.93 HDL (mg/dL) Tg (mg/dL) Groups M SD M SD CT 21.12 (b) [+ or -] 5.37 55.30 (b) [+ or -] 15.55 R 26.30 (ab) [+ or -] 4.08 51.01 (b) [+ or -] 10.49 CL 39.89 (a) [+ or -] 17.43 190.57 (ab) [+ or -] 116.35 CR 40.46 (a) [+ or -] 17.00 302.43 (a) [+ or -] 175.29 Chol = cholesterol; Tg = triglycerides; M = means; SD = standard deviation. Duncan's test, P<0.05. CT = control nornolipemic; R = resveratrol normolipemic; CL = control hyperlipemic; CR = resveratrol hyperlipemic.