Mammary tumor lipids and plasma lipoproteins in DMBA‐intubated rats fed olive or safflower oils

Abstract

The effects of feeding olive and safflower oils on lipid and fatty acid composition of mammary tumors, plasma lipids and lipoproteins, and the nuclear magnetic resonance (NMR) spectra of plasma were investigated in rats. 7-12-Dimethylbenz[a]anthracene (DMBA)- and placebo-intubated male Sprague-Dawley rats were fed 20% fat diets containing 18:2n-6 (wt/wt) from either high-linoleic safflower oil (SL, 14.6% 18:2n-6), high oleic safflower oil (SO, 3.4% 18:2n-6), olive oil (OO, 1.1% 18:2n-6), or olive oil supplemented with 18:2n-6 (OL, 3.4% 18:2n-6) for 16 weeks. Our result indicated that tumor composition of 18:1n-9 and 18:2n-6 reflected the diet, but tumor neutral lipid (NL) was more reflective of diet than was tumor phospholipid (PL). The 20:4n-6 content of tumor PL was constant in all of the dietary groups despite threefold higher levels of 18:2n-6 in tumor PL from animals fed SL than from those fed SO, OO, or OL diets. This suggests a possible feedback inhibition of delta 6-desaturase by the higher content of 18:2n-6 associated with SL feeding No diet effects were obtained for tumor total lipid, NL, PL, cholesterol, and triglyceride contents. Plasma lipoprotein changes were more reflective of diet than tumorigenesis except for apolipoprotein-E, which was lower, and for very low-density lipoprotein cholesterol and low-density lipo protein, which were higher in tumor-bearing rats. Plasma NMR analysis indicated no difference in the average line widths of the methyl and methylene resonances for tumor-bearing and nontumor-bearing rats fed any of the diets.