Effect of Simultaneous Intake of Fish Protein and Fish Oil on Cholesterol Metabolism in Rats Fed High-Cholesterol Diets

This study demonstrated the effect of the simultaneous dietary administration of fish protein and fish oil, two macronutrients found in fish meat, on cholesterol metabolism in rats. Male Wistar rats were divided into four groups and fed an AIN-93G modified hypercholesterolmic diet with casein (20%) + soybean oil (7%), casein (10%) + fish protein (10%) + soybean oil (7%), casein (20%) + soybean oil (5%) + fish oil (2%), and casein (10%) + fish protein (10%) + soybean oil (5%) + fish oil (2%) for four weeks. Cholesterol metabolism was measured through serum and liver cholesterol contents, fecal cholesterol and bile acid excretion levels, and liver mRNA expression levels of enzymes and nuclear receptors involved in cholesterol homeostasis. Dietary fish protein decreased serum and liver cholesterol contents, perhaps through increasing fecal cholesterol and bile acid excretion and liver cholesterol 7 -hydroxylase expression level. Dietary fish oil, on the other hand, decreased liver cholesterol content, perhaps due to the suppression of cholesterol synthesis through a decrease in the 3-hydroxy-3methylglutaryl-coenzyme A reductase expression level; the serum cholesterol content was unchanged. This study found that the simultaneous dietary administration of fish protein and fish oil, which is achieved by the intake of intact fish muscle, has hypocholesterolemic effects that help prevent hyperlipidemia and atherosclerosis.