SREBP-1c gene polymorphism is associated with increased inhibition of cholesterol-absorption in response to ezetimibe treatment.

Author(s): Berthold HK, Laaksonen R, Lehtimaki T, Gylling H, Krone W, Gouni-Berthold I

Affiliation(s): Medical Faculty of the University of Bonn, Clinical Pharmacology, Bonn, Germany.

Publication date & source: 2008-05, Exp Clin Endocrinol Diabetes., 116(5):262-7. Epub 2007 Dec 10.

Publication type: Randomized Controlled Trial; Research Support, Non-U.S. Gov't

OBJECTIVE: Sterol regulatory binding proteins 1 and 2 (SREBPs) are transcription factors regulating lipid metabolism. A recent study has associated the CC genotype of the SREBP-1c polymorphism G952G with increased cholesterol synthesis. Further evidence suggests that SREBPs play a role in cholesterol absorption and that SREBP polymorphisms modulate the response to statin therapy. The present study examines whether the G952G polymorphism alters cholesterol synthesis and/or absorption and whether it modulates the response to widely used lipid-lowering drugs such as inhibitors of cholesterol synthesis (simvastatin) or absorption (ezetimibe). METHODS: Seventy-two healthy male subjects with LDL cholesterol <190 mg/dL participated in the study. Twenty four subjects were treated with ezetimibe (10 mg), simvastatin (40 mg) or their combination, respectively, for two weeks. Blood was drawn before and after the 2-week treatment period. RESULTS: Eleven CC homozygous carriers of the gene were found (15%).There were no differences in cholesterol synthesis or absorption between the CC homozygotes and the G allele-carriers, as measured by the ratios to cholesterol of serum lathosterol, desmosterol and cholestenol (synthesis markers) and cholestanol, sitosterol and campesterol (absorption markers). Ezetimibe had a significantly more potent effect in blocking cholesterol absorption in the CC homozygotes compared to the G-carriers ( P=0.002). CONCLUSIONS: The G/C (G952G) polymorphism of the SREBP-1 gene is not associated with cholesterol synthesis or absorption in a German male population. The CC homozygotes have a significantly increased response to the effects of ezetimibe on cholesterol absorption compared to the G allele-carriers, suggesting that SREBP-1 may be implicated in ezetimibe's mechanism of action.