Effects of dietary saturated fat on erucic acid induced myocardial lipidosis in rats.

ABSTRACT

Male Sprague-Dawley rats were fed for one week diets containing 20% by weight fat/oil mixtures with different levels of erucic acid (221n-9) (approximately 2.5 or 9%) and total saturated fatty acids (approximately 8 or 35%). Corn oil and high erucic acid rapeseed (HEAR) oil were fed as controls. The same hearts were evaluated histologically using oil red O staining and chemically for cardiac triacylglycerol (TAG) and 221n-9 content in cardiac TAG to compare the three methods for assessing lipid accumulation in rat hearts. Rats fed corn oil showed trace myocardial lipidosis by staining, and a cardiac TAG content of 3.6 mg/g wet weight in the absence of dietary 221n-9. An increase in dietary 221n-9 resulted in significantly increased myocardial lipidosis as assessed histologically and by an accumulation of 221n-9 in heart lipids; there was no increase in cardiac TAG except when HEAR oil was fed. An increase in saturated fatty acids showed no changes in myocardial lipid content assessed histologically, the content of cardiac TAG or the 221n-9 content of TAG at either 2.5 or 9% dietary 221n-9. The histological staining method was more significantly correlated to 221n-9 in cardiac TAG (r = 0.49; P less than 0.001) than to total cardiac TAG (r = 0.40; P less than 0.05). The 221n-9 content was highest in cardiac TAG and free fatty acids. Among the cardiac phospholipids, the highest incorporation was observed into phosphatidylserine, followed by sphingomyelin. With the addition of saturated fat, the fatty acid composition showed decreased accumulation of 221n-9 and increased levels of arachidonic and docosahexaenoic acids in most cardiac phospholipids, despite decreased dietary concentrations of their precursor fatty acids, linoleic and linolenic acids.