Effect of dietary fish oil on serum lipids and lipoproteins of rats fed diets differing in cholesterol and fat

Abstract

The investigation was attempted to clarify the effects of fish oil on the concentration of lipids in serum and lipoproteins in rats fed diets differing in cholesterol and fat. Male Sprague-Dawley rats were maintained on low-fat/high-fat diets without and with 1.5% cholesterol (base diets) for 28 days. Half of each group was then switched to a fish oil diet for 20 days with 5.6% fish oil for exchange of coconut oil and beef tallow. Total cholesterol in rat serum was increased following feeding high amounts of dietary cholesterol. This increase was due to raised VLDL and LDL cholesterol. Rats fed the high-cholesterol/high-fat diet had lower HDL cholesterol concentration than groups fed the other base diets. Dietary fish oil lowered serum and lipoprotein cholesterol, even in the presence of dietary cholesterol. In rats fed the high-fat/cholesterol-free diet triglyceride levels in total serum and VLDL were higher than in rats fed the other base diets. The hypertriglyceridemia in rats was diminished fed dietary cholesterol. Serum triglyceride concentration was markedly lowered by fish oil, whereas, this effect reached significance only using cholesterol-free diets. This was mainly associated with a reduction in VLDL triglycerides. Fish oil lowered HDL triglycerides only in rats fed the low-fat diet without cholesterol. Lipid components in the base diets did not influence serum and LDL phospholipids. Rats fed the high-fat/cholesterol-free diet had a higher VLDL phospholipid level than the other base groups. Irrespective of the base diet, phospholipid levels in serum and lipoproteins were markedly reduced by dietary fish oil. In conclusion, this study suggests that other dietary lipids should be considered when examining the hypolipemic effect of fish oil.

The effect of a combined dietary treatment with cholesterol and cholic acid on the lipid metabolism of geese at low or high choline concentrations

“…The composition of VLDL of geese fed cholesterol and cholic acid, containing more than 70% of cholesterol and only 5% of triglycérides is completely different from normal VLDL which contain predominately triglycérides. There are several investigations with rats (Rönnemaa, 1976;Hulbron et al, 1982;Martins and Dhopeshwarkar, 1982;Huang et al, 1984;Beynen et al, 1986;Stangl et al, 1993Stangl et al, , 1994a, rabbits (Gupta et al, 1976) and monkeys (Myers et al, 1990), which also demonstrated markedly increased concentrations of cholesterol in plasma after feeding diets rich in cholesterol. Most of those investigations did not study isolated lipoproteins; however, a few of them (Beynen et al, 1984;Myers et al, 1990;Stangl et al, 1993Stangl et al, , 1994a demonstrated also cholesterol-enriched VLDL after feeding diets rich in cholesterol.…”

“…Several studies in rats (Rönnemaa, 1976;Hulbron et al, 1982;Martins and Dhopeshwarkar, 1982;Beynen et al, 1984;Huang et al, 1984;Garg et al, 1985;Stangl et al, 1993Stangl et al, , 1994a, hamsters (Ohtani et al, 1990) and rabbits (Gupta et al, 1976) demonstrated that diets rich in cholesterol markedly raise plasma cholesterol 286 K. EDER concentrations. Therefore, dietary treatment with cholesterol is a widely used model for the study of the development of atherosclerosis {e.g., Stangl et al, 1993;1994a;Loria and Padgett, 1997;Munilla and Herrera, 1997;Munday et al, 1998).…”

“…Therefore, dietary treatment with cholesterol is a widely used model for the study of the development of atherosclerosis {e.g., Stangl et al, 1993;1994a;Loria and Padgett, 1997;Munilla and Herrera, 1997;Munday et al, 1998). Most of those studies besides markedly raised plasma cholesterol concentrations also exhibited fatty livers in animals treated with cholesterol (Lee and Ho, 1975;Huang et al, 1984;Stangl et al, 1994b).…”

Effects of Various Dietary Arginine and Lysine Concentrations on Plasma and Liver Cholesterol Concentrations in Rats

“…It has been well established that supplementation of cholesterol and sodium cholate as hypercholesterolaemic compounds causes an increase in the concentration of cholesterol in plasma, VLDL and LDL, a reduction of cholesterol in HDL and a strong accumulation of cholesterol in the liver [5,42,43] . All these effects were observed in the rats fed the diet supplemented with cholesterol and sodium cholate of experiment 2 compared to those fed the cholesterol-free diet of experiment 1.…”

Effect of dietary fish oil on the expression of genes involved in lipid metabolism in liver and skeletal muscle of lactating sows

“…As a result of these effects, n‐3 PUFA stimulate β ‐oxidation of fatty acids and inhibit lipogenesis in the liver, resulting in a reduction of liver and plasma TAG concentrations (Sampath and Ntambi, ; Fernandez and West, ). In rodent studies, dietary n‐3 PUFA also caused a reduction of plasma cholesterol concentration (Stangl et al., ; Kawasaki et al., ; Hosomi et al., ). Genes of cholesterol homeostasis, including those involved in cholesterol synthesis and cellular cholesterol uptake, are controlled by SREBP‐2.…”