Plasma and hepatic lipid analysis

Plasma cholesterol was measured using an enzymatic kit (DiaSys Diagnostic Systems, Holzheim, Germany), and the same assay was used to measure hepatic cholesterol after extraction of cholesterol from liver homogenates according to the method of Bligh and Dyer (37). Separation of the lipoproteins was performed with fast-protein liquid chromatography (FPLC) using a Superose 6 10/300 GL column (GE Healthcare, Uppsala, Sweden) as described (38). Triglycerides in the lipoprotein fractions were measured using a commercially available kit (Roche Diagnostics, Mannheim, Germany).