Dietary protein and cholesterol metabolism in small intestines

Effect of quality and quantity of dietary protein on blood cholesterol and cholesterol metabolism in small intestines of rat was examined. Compared to casein, bengalgram in the diet decreased blood and intestinal cholesterol. It is suggested that this effect may be due to low levels of leucine in bengalgram protein and less release of insulin, an activator of HMG CoA Reductase. Low casein in the diet (12%) caused a decrease of blood and intestinal cholesterol while high casein in the diet (24%) caused a decrease of intestinal cholesterol only. It is suggested that both qualitywise and quantitywise, dietary protein influences body cholesterol. It is known that the nature and the quality of dietary fat and carbohydrates directly influence the metabolism of cholesterol. The dietary proteins might also have a significant role. Proteins are needed for the synthesis of enzymes required for the anabolism and catabolism of cholesterol and a few protein-aminoacids like leucine have a direct influence on cholesterol metabolism. Bengalgram was chosen for studying the effect of the quality of protein on cholesterol metabolism as there are reports in the literature that bengalgram feeding reduces blood cholesterol. Different amounts of casein-containing diet were used in a separate set of experiments to investigate the effects of low and high protein diets on cholesterol metabolism i.e. quantitative effects of dietary protein. For many years, liver was enjoying the privilege of maintaining the homeostasis of blood cholesterol. Recently it has been shown that small intestines also synthesises considerable amounts of cholesterol. Hence, cholesterol metabolism was investigated separately in duodenum, jejunum and ileum.