GAMMA-TOCOTRIENOL AS A HYPOCHOLESTEROLEMIC AND ANTIOXIDANT AGENT IN RATS FED ATHEROGENIC DIETS

This study was designed to determine whether incoporation of gamma-toc otrienol or alpha-tocopherol in an atherogenic diet would reduce the c oncentration of plasma cholesterol, triglycerides and fatty acid perox ides, and attenuate platelet aggregability in rats. For six weeks, mal e Wistar rats (n = 90) were fed AIN76A semisynthetic test diets contai ning cholesterol (2% by weight), providing fat as partially hydrogenat ed soybean oil (20% by weight), menhaden oil (20%) or corn oil (2%). F eeding the ration with menhaden oil resulted in the highest concentrat ions of plasma cholesterol, low and very low density lipoprotein chole sterol, triglycerides, thiobarbituric acid reactive substances and fat ty acid hydroperoxides. Consumption of the ration containing gamma-toc otrienol (50 mg/kg) and alpha-tocopherol (500 mg/kg) for six weeks led to decreased plasma lipid concentrations. Plasma cholesterol, low and very low density lipoprotein cholesterol, and triglycerides each decr eased significantly (P < 0.001). Plasma thiobarbituric acid reactive s ubstances decreased significantly (P < 0.01), as did the fatty acid hy droperoxides (P < 0.05), when the diet contained both chromanols. Supp lementation with gamma-tocotrienol resulted in similar, though quantit atively smaller, decrements in these plasma values. Plasma alpha-tocop herol concentrations were lowest in rats fed menhaden oil without eith er chromanol. Though plasma alpha-tocopherol did not rise with gamma-t ocotrienol supplementation at 50 mg/kg, gamma-tocotrienol at 100 mg/kg of ration spared plasma alpha-tocopherol, which rose from 0.60 +/- 0. 2 to 1.34 +/- 0.4 mg/dL (P < 0.05). The highest concentration of alpha -tocopherol was measured in plasma of animals fed a ration supplemente d with alpha-tocopherol at 500 mg/kg. In response to added collagen, t he partially hydrogenated soybean oil diet without supplementary chole sterol led to reduced platelet aggregation as compared with the choles terol-supplemented diet. However, gamma-tocotrienol at a level of 50 m g/kg in the cholesterol-supplemented diet did not significantly reduce platelet aggregation. Platelets from animals fed the menhaden oil die t released less adenosine triphosphate than the ones from any other di et group. The data suggest that the combination of gamma-tocotrienol a nd alpha-tocopherol, as present in palm oil distillates, deserves furt her evaluation as a potential hypolipemic agent in hyperlipemic humans at atherogenic risk.