Effect of dietary menhaden, Canola and partially hydrogenated soy oil supplemented with vitamin E upon plasma lipids and platelet aggregation

Vitamin E inhibits fish oil-induced hyperlipidemia and tissue lipid peroxidation in hamsters

Previous research has linked hyperlipidemia with increased serum concentrations of lipid peroxidation products; however, a specific association between diet-induced oxidative stress and hyperlipidemia has not been studied. In the present study, the relationship between tissue lipid peroxidation and hyperlipidemia induced by ingestion of fish oil was examined. In Experiment 1, male Golden Syrian hamsters were fed semipurified diets composed of 1.6 wt% safflower oil plus 15.0 wt% of either butterfat (BF), safflower oil (SAFF), or high-cholesterol menhaden oil [MHO(H-CHOL)] semipurified diets for 27 d. The cholesterol contents of the diets were adjusted to 0.088%. The MHO(H-CHOL)-fed hamsters exhibited higher serum concentrations of total cholesterol, triglycerides, apolipoprotein B, and lipid peroxides when compared to the BF and SAFF diet groups. In a further study (Experiment 2), hamsters were fed for 27 d three dietary treatments: (i) MHO(H-CHOL) with no vitamin E content; (ii) a low-cholesterol menhaden oil containing high concentrations of vitamin E (2.5 mg tocopherol/g oil or dietary concentrations of 375 mg/kg) [MHO(L-CHOL) + E]; and (iii) the MHO(L-CHOL + E) with added cholesterol (595 mg/kg) [MHO(L-CHOL) + CHOL + E] to match the cholesterol content of the MHO(H-CHOL). The MHO(L-CHOL) + E and MHO(L-CHOL) + CHOL + E diet groups showed lower concentrations of serum cholesterol, triglycerides, and hepatic lipid peroxides than the MHO(H-CHOL)-treated group. Moreover, in contrast to the hypercholesterolemia caused by the MHO(H-CHOL) feeding, the MHO(L-CHOL)+ E and MHO(L-CHOL) + CHOL + E diets did not show a serum cholesterol-elevating action. This study supports the hypothesis that oxidative stress in the Syrian hamster could play a causal role in dietary-induced hyperlipidemia which can be inhibited by high vitamin E intake.

Nutritional value of micro-encapsulated fish oils in rats

The nutritional value of a micro-encapsulated fish oil product has been investigated. Three groups of 10 male Wistar rats each were fed diets containing 20% (w/w) of fat, and only the type and form of the fat added was different. In the test groups 5% (w/w) of fish oil either as such or in a micro-encapsulated form was incorporated in the diets. The remaining fat was lard supplemented with corn oil to a dietary content of linoleic acid at 10% (w/w). The control group received lard and corn oil only. A mixture similar to the dry matter in the micro-encapsulated product was also added to the diets not containing this product. The uptake of marine (n-3) polyunsaturated fatty acids (PUFA) from both types of fish oil supplement was reflected in the fatty acid profiles of liver phosphatidyl cholines (PC), phosphatidyl ethanolamines (PE), triglycerides (TG) and cardiolipin (CL). A suppression of the elongation of linoleic acid leading to a higher concentration of this fatty acid in liver PC and PE was also observed. The concentration of total lipids, triglycerides, cholesterol and phospholipids in liver was similar in all groups. Supplements of long chain (n-3) PUFA did not influence the concentration of plasma TG but lowered the level of plasma cholesterol. No change in the oxidative status, measured as glutathione peroxidase activity and cytochrome P450 concentration in the liver, was found after feeding with fish oil either directly or in the micro-encapsulated form. Intake of (n-3) PUFA lowered the concentration of vitamin E in plasma while the content of vitamin E in the liver was unchanged. Overall, fish oil and micro-encapsulated fish oil resulted in the same fatty acid pattern in the major lipid classes and the same concentrations of liver and plasma lipids. Furthermore, supplementation of fish oil or micro-encapsulated fish oil did not induce oxidative stress when the diets were supplemented with ambient concentrations of anti-oxidants. It is concluded that micro-encapsulated fish oil is suitable for increasing the intake of (n-3) PUFA by fortification of normal daily food ingredients.

gamma-Tocotrienol as a hypocholesterolemic and antioxidant agent in rats fed atherogenic diets

This study was designed to determine whether incorporation of gamma-tocotrienol or alpha-tocopherol in an atherogenic diet would reduce the concentration of plasma cholesterol, triglycerides and fatty acid peroxides, and attenuate platelet aggregability in rats. For six weeks, male Wistar rats (n = 90) were fed AIN76A semisynthetic test diets containing cholesterol (2% by weight), providing fat as partially hydrogenated soybean oil (20% by weight), menhaden oil (20%) or corn oil (2%). Feeding the ration with menhaden oil resulted in the highest concentrations of plasma cholesterol, low and very low density lipoprotein cholesterol, triglycerides, thiobarbituric acid reactive substances and fatty acid hydroperoxides. Consumption of the ration containing gamma-tocotrienol (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 decreased significantly (P < 0.001). Plasma thiobarbituric acid reactive substances decreased significantly (P < 0.01), as did the fatty acid hydroperoxides (P < 0.05), when the diet contained both chromanols. Supplementation with gamma-tocotrienol resulted in similar, though quantitatively smaller, decrements in these plasma values. Plasma alpha-tocopherol concentrations were lowest in rats fed menhaden oil without either chromanol. Though plasma alpha-tocopherol did not rise with gamma-tocotrienol 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 supplemented with alpha-tocopherol at 500 mg/kg.(ABSTRACT TRUNCATED AT 250 WORDS)