This article is available online at http://www.jlr.orgCholesterol metabolism is regulated mainly by intestinal absorption, hepatic synthesis, and biliary excretion of cholesterol. The negative interaction between cholesterol synthesis and absorption combined with the regulation of LDL receptor activity control the cellular cholesterol contents ( 1 ). Depletion of cellular cholesterol activates sterol regulatory element-binding protein 2 (SREBP2) resulting in increased cholesterol synthesis, whereas excess cholesterol activates the liver X receptor (LXR) -system, resulting in increased bile acid synthesis and increased biliary transport of cholesterol ( 1 ). Furthermore, glucose metabolism and insulin action are associated with cholesterol metabolism with unknown mechanism(s). In type 2 diabetes (T2D), cholesterol metabolism is disturbed so that cholesterol absorption effi ciency is low ( 2-4 ), and cholesterol synthesis is elevated ( 2-6 ). Even in subjects without diabetes, low absorption effi ciency and high synthesis of cholesterol are related to high-normal serum glucose level, insulin resistance, and obesity ( 7-9 ). We wanted to investigate whether the alterations in cholesterol metabolism are continuous from normoglycemia through impaired glucose tolerance to type 2 diabetes. Accordingly, we assayed serum cholesterol precursors (squalene, cholestenol, desmosterol, and lathosterol), markers of cholesterol synthesis in subjects without ( 10 ) and with T2D ( 4 ), and serum plant sterols and cholestanol, markers of cholesterol abAbstract Cholesterol synthesis is upregulated and absorption downregulated in insulin resistance and in type 2 diabetes. We investigated whether alterations in cholesterol metabolism are observed across the glucose tolerance status, from normoglycemia through impaired glucose tolerance to type 2 diabetes, in 781 randomly selected men 45 to 70 years of age from a population-based Metabolic Syndrome in Men Study. Cholesterol metabolism was assayed using surrogate serum markers, squalene, and noncholesterol sterols. The study population was classifi ed into subgroups according to glucose tolerance as follows: normoglycemia, impaired fasting glucose, impaired glucose tolerance, and type 2 diabetes. LDL cholesterol did not differ between the groups. Cholesterol synthesis markers were lowest and absorption markers highest in normoglycemia. Sitosterol was lower in subjects with impaired fasting glucose compared with normoglycemic subjects (113 ± 7 vs. 136 ± 3 10 2 mol/mmol of cholesterol, P < 0.05). LDL cholesterol was not associated with lathosterol/sitosterol ratio, a marker of cholesterol metabolism. Peripheral insulin sensitivity evaluated by the Matsuda index was associated with the lathosterol/sitosterol ratio in the entire population ( r = ؊ 0.457, P < 0.001) and with that of lathosterol/cholestanol independently of obesity. In conclusion, cholesterol metabolism was altered already from subjects with impaired fasting glucose. Upregulated cholesterol synthesis was associated with perip...