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Updated: Jul 11, 2026
07:54
Cholesterol Efflux Assay
Published on: March 6, 2012
27-hydroxycholesterol: production rates in normal human subjects
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.
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.
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