Abstract
A possible relationship between change in dietary cholesterol absorption and plasma lipoprotein responsiveness was examined in 18 normal subjects fed low fat low cholesterol, high fat low cholesterol, and high fat high cholesterol diets. For the group, neither dietary cholesterol nor dietary fat affected the percentage dietary cholesterol absorption, whereas dietary cholesterol intake raised total and LDL-C and dietary fat raised total, LDL, and HDL-C. On a fixed diet there was approximately a 2-fold variation among subjects in percentage dietary cholesterol absorption. Subjects also varied in response to dietary cholesterol and fat with regard to dietary cholesterol absorption and plasma lipoprotein responsiveness. There was a U-shaped parabolic relationship between dietary cholesterol-induced percent change in LDL-C and the change in percentage dietary cholesterol absorption (R2 = 0.62, P = 0.005). A similar but weaker relationship characterized the responsiveness of HDL-C (R2 = 0.38, P = 0.05). For the group, increased cholesterol intake raised dietary cholesterol mass absorption from 1.6 to 4.6 mg/kg per day, but the range of increase was from 1 to 4.7 mg/kg per day. Increased fat intake also affected dietary cholesterol mass absorption with most subjects displaying a strong inverse relationship between fat intake and mass absorption (r = -0.77, P < 0.003). In summary: i) the percentage change in dietary cholesterol absorption in response to dietary cholesterol does appear to regulate diet responsiveness of LDL and HDL-C, and ii) the large variability in percent absorption and changes in percentage and mass absorption in response to dietary cholesterol suggest the presence of genetically determined differences among individuals in the regulation of dietary cholesterol absorption.
Highlights
A possible relationship between change in dietary cholesterol absorption and plasma lipoprotein responsiveness was examined in 18 normal subjects fed low fat low cholesterol, high fat low cholesterol, and high fat high cholesterol diets
It has been suggested that the ability to down-regulate endogenous cholesterol synthesis in response to a dietary challenge limits an individual’s plasma lipoprotein responsiveness [9, 10]
The genes that control them, that regulate individual differences in endogenous cholesterol synthesis may be fundamental to understanding plasma lipoprotein responsiveness to dietary challenge
Summary
A possible relationship between change in dietary cholesterol absorption and plasma lipoprotein responsiveness was examined in 18 normal subjects fed low fat low cholesterol, high fat low cholesterol, and high fat high cholesterol diets. It has been repeatedly observed that there is great interindividual variation in plasma lipoprotein responsiveness to dietary cholesterol and saturated fat. This variation is presumably genetic but the specific genes involved are largely unknown. It has been previously shown in humans that for each 100 mg/day increase in dietary cholesterol the mean plasma cholesterol level rises 7 mg/dl, but some individuals are unresponsive and have even decreasing cholesterol levels, while others show an exaggerated response, with increases of more than 2-fold the mean [2,3,4,5,6]. The genes that control them, that regulate individual differences in endogenous cholesterol synthesis may be fundamental to understanding plasma lipoprotein responsiveness to dietary challenge
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