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Related Experiment Video

Updated: Jul 11, 2026

Cholesterol Efflux Assay

Cholesterol Efflux Assay

Published on: March 6, 2012

27-hydroxycholesterol: production rates in normal human subjects.

W C Duane¹, N B Javitt

¹Department of Medicine, Veterans Affairs Medical Center and University of Minnesota, Minneapolis, MN 55417, USA.

Journal of Lipid Research

|July 7, 1999

Summary

The 27-hydroxylation pathway contributes minimally to human bile acid synthesis, accounting for only 8.7% of total production. This pathway, primarily in vascular endothelium and macrophages, may aid cholesterol removal.

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Area of Science:

Biochemistry
Human Physiology
Metabolic Pathways

Background:

Bile acids are crucial for digestion and cholesterol homeostasis.
The 27-hydroxylation pathway is a proposed route for bile acid synthesis.
Quantifying the contribution of this pathway in humans is essential.

Purpose of the Study:

To determine the quantitative contribution of the 27-hydroxylation pathway to bile acid production in humans.
To assess the conversion rate of 27-hydroxycholesterol to bile acids.

Main Methods:

Isotope-labeled tracers ([24-14C]cholic acid, [24-14C]chenodeoxycholic acid, [22, 23-3H]-27-hydroxycholesterol, [2H]-27-hydroxycholesterol) were administered intravenously.
Serum levels of labeled compounds and bile acid composition were analyzed.
Fecal acidic sterol output was used for independent measurement in some subjects.

Main Results:

Endogenous 27-hydroxycholesterol production averaged 17.6 mg/day, representing 8.7% of total bile acid synthesis.
Approximately 66% of infused 27-hydroxycholesterol was converted to bile acids, predominantly chenodeoxycholic acid (72.6%).
Significant variability was observed among subjects.

Conclusions:

The 27-hydroxylation pathway plays a minor role in overall bile acid synthesis in healthy humans.
Despite its small contribution, this pathway, active in endothelial cells and macrophages, may be important for clearing excess cholesterol from blood vessels.