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Genetic basis of sitosterolemia.
1Medical University of South Carolina, Charleston, South Carolina 29405, USA.
Current Opinion in Lipidology
|March 27, 2001
Summary
The body selectively absorbs cholesterol while excluding other sterols via a mechanism involving ABCG5 and ABCG8 genes. Mutations in these genes cause sitosterolemia, leading to hyperabsorption of all sterols.
Area of Science:
- Molecular Biology
- Genetics
- Biochemistry
Background:
- Dietary cholesterol absorption and selective sterol excretion mechanisms are poorly understood.
- Western diets contain significant cholesterol and non-cholesterol sterols (e.g., plant sterols).
- Normal individuals absorb 50-60% of dietary cholesterol but <1% of non-cholesterol sterols.
Purpose of the Study:
- To elucidate the molecular mechanisms governing selective dietary cholesterol absorption and retention.
- To understand the genetic basis of sitosterolemia and its impact on sterol metabolism.
Main Methods:
- Genetic mapping of the STSL locus to human chromosome 2p21.
- Identification and analysis of mutations in the ABCG5 and ABCG8 genes in sitosterolemia patients.
Main Results:
- Sitosterolemia is caused by mutations in the tandem ABC genes, ABCG5 and ABCG8, encoding sterolins.
- These mutations lead to hyperabsorption and retention of both cholesterol and non-cholesterol sterols.
- Patients exhibit elevated plasma plant sterol levels, xanthomas, accelerated atherosclerosis, and premature coronary artery disease.
Conclusions:
- The identification of ABCG5 and ABCG8 provides insight into the molecular regulation of sterol absorption and excretion.
- Sitosterolemia serves as a critical model for understanding the body's selective cholesterol handling.
- These findings support the existence of a specific molecular pathway for dietary cholesterol absorption and sterol elimination.