There is no evidence whether humans absorb cholesterol oxidation products (COPS) from food sources. Therefore, (after-meal) absorption of COPS in humans was studied following consumption of a powdered egg meal containing 30-90 ppm each of four different COPS. Both total plasma and plasma chylomicron COPS concentrations increased. By contrast, subjects consuming fresh eggs containing very low levels of the same four COPS (O-2 ppm) demonstrated no significant rise in plasma COPS. We concluded that the human subjects studied had the capacity to absorb COPS from food sources. The brief residence time of COPS observed in both chylomicrons and plasma suggested rapid transfer of COPS among lipoprotein fractions and/or clearance from plasma.

Dietary high viscosity hydroxypropyl methylcellulose (HPMC) lowered plasma and liver cholesterol concentrations in cholesterol-fed hamsters. To determine the level of viscosity needed to effect a significant reduction in total plasma cholesterol, hamsters were fed for 3 wk diets containing 0.12% cholesterol and either 4% cellulose or one of four preparations of HPMC that varied in viscosity between 14 and 1698 centipoise (cP), as estimated in vitro. Blood was collected for plasma cholesterol determination, and intestinal contents were obtained by finger-stripping of the excised small intestine. Contents were centrifuged and the supernatant (ex vivo) viscosity determined. In vitro and ex vivo viscosities were correlated (R2 = 0.96). Plasma cholesterol concentrations declined as in vitro or ex vivo viscosity increased. Maximal plasma cholesterol reduction occurred at an ex vivo viscosity of approximately 150 cP. There was a linear relationship between plasma cholesterol and the logarithm of ex vivo viscosity (R2 = 0.98). Our results suggest that materials that increase the viscosity of intestinal contents can be effective in reducing plasma cholesterol and that only moderate increases in viscosity are necessary to achieve this effect.

This study was conducted to test the hypothesis that increased intestinal contents viscosity lowers plasma cholesterol concentrations by decreasing cholesterol absorption. Male Golden Syrian hamsters were fed for 4 wk diets containing 0.12% cholesterol, and either 4% cellulose or four different viscosity grades of hydroxypropyl methylcellulose (HPMC). Dietary HPMC confers viscosity in the small intestine but is resistant to fermentation. Cholesterol absorption efficiency was measured using the dual isotope ratio method, and plasma and liver cholesterol concentrations were determined enzymatically. Ex vivo viscosity of intestinal contents supernatants was measured using a Wells-Brookfield cone/plate viscometer, and the means of treatment groups ranged from 6 to 6532 mPa.s. Relative to dietary cellulose, all viscosity grades of HPMC resulted in significantly lower cholesterol absorption efficiency, lower plasma cholesterol concentration, and lower liver cholesteryl ester content. The logarithm of intestinal contents ex vivo viscosity was inversely correlated with dietary cholesterol absorption (r2 = 0.84, P = 0.028). Furthermore, dietary cholesterol absorption was positively correlated with plasma cholesterol concentration (r2 = 0.89, P = 0.017) and liver cholesteryl ester content (r2 = 0.96, P = 0.0031). Thus, the data suggest an independent role of intestinal contents viscosity in lowering plasma cholesterol concentration and liver cholesteryl ester content by reducing cholesterol absorption efficiency.

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