Observations on the Fate of Ingested Cholesterol in Man

Abstract

Tritium-labeled Cholesterol has been used to study several aspects of exogenous cholesterol metabolism in man. The rate and magnitude of the appearance of ingested cholesterol in the various blood compartments has been followed. Fecal excretion of the labeling material was measured. Cholesterol of dietary origin was demonstrated in a human atherosclerotic aorta.

The Intestinal Absorption of Dietary Cholesterol by Hypercholesterolemic (Type II) and Normocholesterolemic Humans

“…The metabolic defect in type II hypercholesterolemia was clearly not exaggerated cholesterol absorption. Nor was absorption more rapid in the hypercholesterolemic patients since their plasma radioactivity curves peaked at 48 h, as did those of our normal subjects and those of the subjects of other studies (18,19). In the recent paper by Quintao, Grundy, and Ahrens, the measurement of the intestinal absorption of five hypercholesterolemic patients and one normocholesterolemic subject also indicated a similarity (6).…”

Isotopic Studies of Plasma Cholesterol of Endogenous and Exogenous Origins 1

“…The data of Biggs and his co-workers (13) who fed tritium labeled cholesterol are essentially similar to those reported here except that the specific activity of total plasma cholesterol was measured rather than that of ester cholesterol. Since 60 to 75 per cent of plasma cholesterol is esterified, measurements of total cholesterol give a good approximation of the specific activity of the ester fraction.…”

“…These.values are higher than those reported for the absorption of one granmi doses of tritium labeled cholesterol (13). With the exception of-CHC-5, the subjects in this study received approximately 10 mg. of labeled cholesterol and the efficiency of absorption may be related to the large difference in the amount fed.…”

“…This suggests either that absorption is slow, that absorbed cholesterol is retained in the intestinal mucosa, or that newly absorbed cholesterol is rapidly removed from the blood and then later reintroduced' into the circulation. Biggs and his co-workers (13) concluded that cholesterol absorption was slow, since they observed a sustained fecal excretion of radioactivity after feeding tritium labeled cholesterol. However, these authors measured either the total fecal radioactivity, or in one instance, the activity of a crude extract that contained cholesterol, coprosterol and possibly other steroids.…”

In vivo influx of free and esterified plasma cholesterol into human aortic tissue without atherosclerotic lesions.

“…The in vivo transfer of free and esterified cholesterol from plasma lipoproteins into the arterial wall of humans are therefore important to an understanding of the pathophysiology of atherosclerosis. This transfer process has been studied by only a few investigators, who administered labeled cholesterol orally or intravenously to patients (1)(2)(3). Arterial specimens were obtained days or months later when the patients died or underwent arterial surgery (4).…”