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ARS Home » Northeast Area » Boston, Massachusetts » Jean Mayer Human Nutrition Research Center On Aging » Research » Publications at this Location » Publication #37726

Title: INTERACTION OF DIETARY FAT SATURATION AND CHOLESTEROL LEVEL ON CHOLESTEROL SYNTHESIS MEASURED USING DEUTERIUM INCORPORATION

Author
item JONES PETER J H - UNIV OF BRITISH COLUMBIA
item LICHTENSTEIN ALI - TUFTS-HNRCA
item SCHAEFER ERNST J - TUFTS-HNRCA

Submitted to: Journal of Lipid Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/7/1994
Publication Date: N/A
Citation: N/A

Interpretive Summary: The effect of dietary cholesterol intake on formation of cholesterol in the blood was studied during periods when subjects consumed a relatively low fat diet (30% of calories) containing either corn oil or beef tallow. Study subjects had a mean age of 63 years and a mean cholesterol concentrations of 238 mg/ml indicating that, at the time of selection for the study, they had cholesterol levels in the borderline or high risk range. The amount of cholesterol added to the diet was modest and equivalent to about 1.5 eggs per day. Cholesterol levels went from lowest to highest when subjects consumed the corn-oil, corn-oil-plus-cholesterol, beef-tallow, and beef-tallow-plus-cholesterol-enriched diets. The outcome of the study indicated that the consumption of corn-oil-enriched diets resulted in lower blood cholesterol levels than during periods when the subjects consumed the beef-tallow-enriched diet. The addition of cholesterol to diets enriched in either of the fats had no additional effect on the rates of newly formed cholesterol.

Technical Abstract: To examine the interactive effects of dietary fat saturation and choles- terol level on serum lipids and de novo cholesterogenesis, moderately hypercholesterolemic subjects were fed solid-foods diets containing 30% fat (80mg C.1000 Kcal**-1) in which 2/3 fat was either corn oil or beef tallow, with and without 120mg C.1000 Kcal**-1, for 5 wks. At the end of each diet period, subjects were given deuterium (D) oxide orally, and de novo cholesterol synthesis was measured over 24 h from D incorporation into cholesterol as fractional synthesis rates (FSR) and absolute synthetic rate (ASR) into the rapid exchangeable cholesterol pool. Plasma total and low density lipoprotein levels were elevated (p<0.01) with both beef tallow and cholesterol feeding. High density lipoprotein (HDL) levels were not influenced by fat saturation or cholesterol level; however, HDL was higher with addition of cholesterol to corn oil vs. beef tallow (p<0.02). Plasma triglycerides were higher (p<0.02) with beef tallow feeding but were not influenced by cholesterol level. FSR was increased (p<0.02) by feeding corn oil, versus beef fat, but not by dietary cholesterol level. Cal- culated cholesterol pools sizes did not differ across groups; however, ASR was also elevated with corn oil versus beef tallow feeding (p<0.02). Results indicate that corn oil feeding lowers circulating cholesterol by mechanisms other than reduced synthesis, and that cholesterol at the level of supplementation used is not associated with feedback inhibition of cholesterogenesis. However, with the exception of HDL levels, dietary fat saturation and cholesterol levels do not interactively influence circulating lipoprotein cholesterol levels and cholesterol synthesis.