Effect of dietary fish oil on tumor-induced hyperlipidemia and tumor growth in rats implanted with a methylcholanthrene-induced sarcoma

Male Fischer 344 rats implanted with a methylcholanthrene-induced sarcoma ( MCS), along with normal (or control) animals, were fed diets containing eit her 10% corn oil (CO) or 2% CO + 8% fish oil (FO), designated as diets CO a nd FO, respectively, in a study designed to determine the effect of dietary FO on serum lipids (in the presence or absence of a tumor) and the growth and fatty acid composition of the MCS. For both diets, MCS-bearing fats had significantly (p<0.05) higher serum levels of triglycerides, cholesterol, phospholipids, and total lipids than controls. For both controls and tumor- bearers, serum levels of all these lipids were, with the exception of chole sterol for the tumor-bearers, significantly lower in rats receiving the FO diet than for the corresponding groups receiving the CO diet. Relative to r ats fed the CO diet, those fed the FO diet had significantly higher serum l evels of some fatty acids (e.g., 20:5n-3) but significantly lower levels of others (e.g., 18:2n-6), regardless of tumor status. For the tumor-bearers, differences in the levels of fatty acids in MCS tissue reflected differenc es in the fatty acid composition of total serum Lipids. Sarcoma growth was unaffected by diet. Thus, feeding dietary FO resulted in changes in the lip id status of both control and tumor-bearing rats. Since sarcoma growth was unaffected by diet the reduction in the severity of MCS-induced hyperlipide mia by FO appears to be due to an effect of the oil per se.