Comparison of the effects of range of dietary lipids upon serum and tissue lipid composition in the rat

Since the type of fat consumed in the diet may play a role in the development of several disorders, it is important to ascertain the effects of different dietary fats upon parameters such as serum lipid levels and adipose deposition. The aim of this study was to determine the effects of feeding rats a range of fats with differing fatty acid compositions. Weanling male rats were fed for 10 weeks on a low fat (LF) diet or on one of five high fat diets, which contained 20% by weight of either by hydrogenated coconut oil (HCO), olive oil (OO), safflower oil (SO), evening primrose oil (EPO) or menhaden (fish) oil (MO). Food intake, animal growth, tissue weights at sacrifice, serum and liver lipid concentrations and serum, heart, brain and adipose tissue fatty acid compositions were studied. The food intake of the LF-fed animals was greater than that of animals fed on the high fat diets; there were no differences in food intake between animals fed the high fat diets. The total energy intake was lower for animals fed on the HCO diet than for those fed on the LF, OO, EPO or MO diets; there were no other differences in energy intake between the groups. Animals fed the different diets had almost identical rates of weight gain up to 5 weeks; after this period of rapid growth, the increase in weight was slower in all groups but especially in the LF-fed animals. The LF-fed rats had a lower total weight gain and smaller final weights than rats fed on the high fat diets. Animals fed on the MO diet had a greater weight gain than those fed on the OO or EPO diets and their final weights were greater. The MO diet resulted in greatly increased liver weight compared with each of the other diets. The HCO, OO and EPO diets also increased liver weight compared with the LF diet. The total lipid content of the livers from rats fed the high fat diets was greater than that of those from rats fed the LF diet; the livers from animals fed the MO diet contained more lipid than those from animals fed each of the other diets. MO feeding increased the free cholesterol, cholesterol ester and triacylglycerol contents of the liver. Each of the high fat diets resulted in an increase in epididymal fat pad weight compared with the LF diet, but the high fat diets resulted in different degrees of adipose deposition; the EPO and MO diets resulted in smaller epididymal fat pads than the HCO, OO and SO diets. Serum total cholesterol concentrations were higher after feeding the OO, SO or EPO diets than after feeding the LF or MO diets. The MO diet resulted in a total serum cholesterol concentration which was lower than that of animals fed each of the other diets. The serum cholesterol ester concentration of the MO-fed animals was lower than that of the LF-, SO- or EPO-fed animals. Serum triacylglycerol concentrations of the HCO- and OO-fed rats were higher than those of the LF-, SO-, EPO- or MO-fed animals. The fatty acid compositions of the serum, adipose tissue and the neutral lipid and phospholipid fractions of the heart reflected those of the diets themselves, apart from those from the HCO-fed animals, which contained much lower proportions of medium chain fatty acids than did the diet. The fatty acid composition of the phospholipid fraction of the brain was not affected by dietary lipid manipulation. The fatty acid composition of the diet affects animal growth, tissue weights, serum cholesterol, cholesterol ester and triacylglycerol concentrations and the fatty acid compositions of the serum, adipose tissue and heart. The fatty acid composition of the brain is relatively resistant to dietary modification.