High frequency of a retinoid X receptor γ gene variant in familial combined hyperlipidemia that associates with atherogenic dyslipidemia

Abstract

OBJECTIVE - The genetic background of familial combined hyperlipidemia (FCHL) has not been fully clarified. Because several nuclear receptors play pivotal roles in lipid metabolism, we tested the hypothesis that genetic variants of nuclear receptors contribute to FCHL. METHODS AND RESULTS - We screened all the coding regions of the PPARα, PPARγ2, PPARδ, FXR, LXRα, and RXRγ genes in 180 hyperlipidemic patients including 60 FCHL probands. Clinical characteristics of the identified variants were evaluated in other 175 patients suspected of coronary disease. We identified PPARα Asp140Asn and Gly395Glu, PPARγ2 Pro12Ala, RXRγ Gly14Ser, and FXR -1g->t variants. Only RXRγ Ser14 was more frequent in FCHL (15%, P<0.05) than in other primary hyperlipidemia (4%) and in controls (5%). Among patients suspected of coronary disease, we identified 9 RXRγ Ser14 carriers, who showed increased triglycerides (1.62±0.82 versus 1.91±0.42 [mean±SD] mmol/L, P<0.05), decreased HDL-cholesterol (1.32±0.41 versus 1.04±0.26, P<0.05), and decreased post-heparin plasma lipoprotein lipase protein levels (222±85 versus 149±38 ng/mL, P<0.01). In vitro, RXRγ Ser14 showed significantly stronger repression of the lipoprotein lipase promoter than RXRγ Gly14. CONCLUSION - These findings suggest that RXRγ contributes to the genetic background of FCHL. © 2007 American Heart Association, Inc.