Mechanisms of cholesterol transport, uptake and tissue distribution in miniature pigs fed two proteins and two fats

Abstract

<p>In a 2 x 2 factorial arrangement, miniature pigs were fed four diets containing vegetable protein and fat (soybean) and animal protein (egg white) and fat (beef tallow) to investigate the effects of protein and fat source on transport of cholesterol in the plasma, uptake of cholesterol from the plasma by tissues and distribution of cholesterol in tissues;Beef tallow consumption resulted in greater plasma cholesterol concentrations, decreased low density lipoprotein-cholesterol concentrations and lower ratios of cholesterol to protein in low density lipoprotein than did consumption of soybean oil. The ratio of high density lipoprotein-cholesterol to low density lipoprotein-cholesterol was increased by beef tallow consumption. The percentage by weight of cholesterol in low density lipoprotein was significantly greater in pigs consuming soybean oil than in pigs consuming beef tallow. Dietary protein source had no significant effect on plasma cholesterol concentration or on lipoprotein cholesterol. Dietary fat source had no consistent effect on removal of low density lipoprotein from plasma whereas egg white consumption tended to decrease the fractional catabolic rate and irreversible loss of low density lipoprotein-cholesterol and -protein when compared with consumption of soy protein;Soybean oil feeding, compared with beef tallow feeding, resulted in greater concentrations of cholesterol in aorta, heart and large and small intestines. Similar trends were seen in liver, adipose tissue and skeletal muscle. Dietary protein had no significant effect on tissue cholesterol concentrations. Uptake of intact low density lipoprotein tended to be greater when soybean oil or soy protein was fed, compared with beef tallow or egg white. Net exchange of free cholesterol from low density lipoprotein to tissues tended to be greater when the vegetable products were fed;Dietary protein and fat seemed to influence lipoprotein metabolism by different mechanisms: Fat source altered lipoprotein concentrations and low density lipoprotein composition whereas protein source affected the removal rate of low density lipoprotein from plasma. The association between soybean oil or soybean protein consumption and increased cholesterol concentration and greater uptake of intact low density lipoprotein in some tissues may have implications for the development of atherosclerosis.</p>