Effects of various high-fat diets on myocardial contractility and morphology in rats.

The effects of various high-fat diets (20% w/w) containing commercially available fats and oils (butter, corn oil, corn oil margarine, canola oil, canola oil margarine, soybean oil, soybean oil margarine, sunflower oil, sunflower oil margarine) on myocardial contractility and morphology and on plasma lipids were investigated in male Sprague-Dawley rats fed the diets for 16 weeks. Diets containing corn oil caused significantly (P less than or equal to .05) higher plasma total cholesterol levels than diets containing butter. Significant differences were also determined in lipoprotein levels. Plasma triglyceride levels were significantly (P less than or equal to .05) higher with butter than with sunflower oil or sunflower margarine. No significant differences among the groups occurred in blood pressure, heart rate, or myocardial contractility. Histological evaluation revealed that animals fed canola oil had the highest incidence and severity of myocarditis and fibrosis and that the degree of cardiac lipidosis was not correlated to the erucic-acid content of the diet. Myocardial damage was significantly (P less than or equal to .05) negatively correlated with stearic and palmitic acids and positively correlated with oleic acid. The results indicate that diets low in saturated fats may have adverse long-term effects on the heart.