DIETARY PROTEINS MODULATE THE EFFECTS OF FISH-OIL ON TRIGLYCERIDEMIA IN THE RAT

Sprague-Dawley rats were fed purified diets varying in both protein (2 0%) and lipid (11%)content for 28 d to verify the independent and inte ractive effects of dietary proteins and lipids on serum and hepatic li pids, and on tissue lipoprotein lipase (LPL) activity in both fasted a nd postprandial states. These diets consisted of either casein-menhade n oil, casein-coconut oil, soy protein-menhaden oil (SPMO), soy protei n-coconut oil, cod protein-menhaden oil, or cod protein-coconut oil. A randomized 3 x 2 factorial design was used. A significant protein-lip id interaction was seen on serum triglyceride levels: menhaden oil, co mpared with coconut oil, induced a decrease in serum triglyceride leve ls when combined with soy protein but not when combined with cod prote in and casein. The lower serum triglyceride concentrations observed in the SPMO-fed rats could be the result of decreased hepatic triglyceri des when soy protein was compared with casein and when menhaden oil wa s compared with coconut oil. Total LPL activity in the heart was highe r in menhaden oil-fed rats than in coconut oil-fed rats in the postpra ndial state. The higher LPL activity in the heart could, however, expl ain only 10% of the reduction of serum triglycerides, contributing sli ghtly to the lowering effects of SPMO diet on serum triglycerides. The refore, the present results indicate that dietary proteins can modulat e the effects of fish oil on triglyceridemia in the rat, and that coul d be mainly related to specific alterations in hepatic lipid concentra tions.