Oxysterols: Sources, cellular storage and metabolism, and new insights into their roles in cholesterol homeostasis.

Oxysterols are structurally identical to cholesterol, but with one or more additional oxygen containing functional groups (such as alcohol, carbonyl or epoxide groups). The wide array of oxysterols encountered in human health and disease vary in their origin (either enzymic or non-enzymic), and their putative effects and/or function(s). Some are thought to be damaging, whereas others may play important physiological roles, including in the regulation of cholesterol homeostasis. In this review, we will concentrate on the major cellular oxysterols. We summarise their location, generation, metabolism and elimination, as well as providing insights into the latest research into their regulatory roles in cholesterol homeostasis.