Common polymorphisms in the CYP7A1 gene do not contribute to variation in rates of bile acid synthesis and plasma LDL cholesterol concentration

Transcriptional regulation of the cholesterol 7α-hydroxylase (CYP7AI) gene is of critical importance for bile acid and cholesterol metabolism. We evaluated the physiological significance of two common polymorphisms (−203C/A and −469T/C) in the promoter region of the CYP7AI gene. No evidence was found for physiological differences between either the −203C and −203A alleles or the −469T and −469C alleles in transient transfection studies using native 834 bp promoter constructs. Moreover, no association was observed between the CYP7AI promoter polymorphisms and the hepatic cholesterol 7α-hydroxylase activity and parameters of bile acid synthesis rates, as analyzed in subjects with gallstone disease. In addition, no relationships were found between the promoter polymorphisms and plasma LDL cholesterol concentration in association studies conducted in three different groups of middle-aged Swedish men. Finally, near complete allelic association was found between the two promoter polymorphisms and the IVS6 + 363G/A polymorphism at the 3′ end of the CYP7AI gene (D′ = 0.98), indicating strong linkage disequilibrium across the whole CYP7AI gene. It is concluded that common polymorphisms of the CYP7A1 gene do not contribute to variation in cholesterol 7α-hydroxylase activity, rates of bile acid synthesis and plasma LDL cholesterol concentration in humans.