Regulation of Diurnal Variation of Cholesterol 7 alpha-hydroxylase (CYP7A1) Activity in Healthy Subjects

Abstract

To better understand the regulation of CYP7A1 activity, three day-long examinations were carried out in 12 healthy men. The concentrations of 7 alpha-hydroxycholest-4-en-3-one (C4), a surrogate marker of CYP7A1 activity, bile acids (BA), insulin, glucose, nonesterified fatty acids, triglycerides, and cholesterol were measured in serum in 90-min intervals from 7 AM till 10 PM.

To lower and to increase CYP7A1 activity, the investigations were also performed after cholestyramine or chenodeoxycholic acid administration. Area under the curve of C4 correlated positively with that of insulin.Our results suggest that insulin is involved in the regulation of diurnal variation of CYP7A1 activity in humans.