Analysis of cholesterol oxidation products in biological samples

Cholesterol oxidation products, or oxysterols, have gained increased attention since it was suggested that they participate in cell signaling as ligands for the nuclear receptors liver X receptor alpha and beta. In addition, oxysterols serve as important intermediates in bile acid biosynthesis and are also involved in cholesterol transport. Several studies have suggested that certain oxysterols may be used as markers for oxidative stress, and still other oxysterols may be of use in diagnosing neurological diseases. This broad spectrum of functions in health and disease has created a demand for accurate and reliable methods to measure oxysterols in complex biological matrixes. At present, the most reliable and sensitive method for oxysterol determination in biological materials is isotope-dilution gas chromatography-mass spectrometry using deuterium-labeled internal standards. With this technique, the major oxysterols in human blood plasma and atherosclerotic plaques have been carefully determined. The knowledge of oxysterol contents in other tissues and organs is still very scarce. As oxysterols are found to participate in an increasing number of cellular events, it is obvious that improved methods are needed for their analysis to understand their roles in the living cell.