Effects of the Esterification of Supplemental Cholesterol and Sitosterol in the Diet

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Abstract
Serum and liver cholesterol levels of rats were determined at the end of 14 days' maintenance on the following diets: low cholesterol, 1% cholesterol, and equivalent amounts of cholesteryl acetate, benzoate, palmitate, stearate and oleate. The liver cholesterol in the animals fed free cholesterol, cholesteryl acetate and cholesteryl oleate was significantly elevated as compared to the other groups. The cholesteryl benzoate, palmitate and stearate resulted in only minimal elevation of liver cholesterol as compared to low cholesterol diet. The increment in liver cholesterol was almost entirely in the ester fraction, without regard to whether the cholesterol added to the diet was free or esterified. In a second study serum and liver cholesterol levels were determined at the end of 14 days' maintenance on a 1% cholesterol diet to which was added 5% sitosterol or equivalent amounts of sitosteryl acetate, propionate, palmitate and oleate. Free sitosterol and the several esters all resulted in mean liver cholesterol levels lower than that of the cholesterol-fed controls. Free sitosterol and the acetate and oleate displayed the greatest inhibitory effect on cholesterol absorption, mean liver cholesterol levels in these groups not differing appreciably from that of the group fed a low-cholesterol diet. Sitosteryl propionate was a less effective inhibitor of cholesterol absorption, and the palmitate least effective. The differences in absorption of the several cholesterol esters appear to be related to their relative rates of hydrolysis by pancreatic cholesterol esterase, the more rapidly hydrolyzed esters being more readily absorbed. Similarly, the effectiveness of sitosterol esters in inhibiting cholesterol absorption may be related to their relative rates of enzymatic hydrolysis, the more rapidly hydrolyzed esters being the more effective inhibitors.