Oxysterols. Players in different metabolic leagues

In animals, cholesterol (C27H46O; 3b-Hydroxy-5-cholestene/5- Cholesten-3b-ol) is a widely present molecule. Iitially named cholesterine, cholesterol was discovered in 1815 by Eugène Chevreul. The oxidation of cholesterol through enzymatic or free radical-mediated processes gives rise to oxidized compounds, namely oxysterols [1,2]. Cholesterol can also be identified in plants where the main sterol compounds are phytosterols [3]. Oxysterols as well as phytosterols molecules have several and specific biological activities. Phytosterols, taken moderately as dietary supplements, have cholesterol lowering properties [4] and could help to prevent and treat cancers [5]. In addition, as they can cross the blood brain barrier, they can prevent amyloid-beta formation, which contributes to the development of Alzheimer’s disease [6– 8]. As for oxysterols, they are mediators of inflammation [9], potent inducers of oxidative stress, and can trigger cell death associated with endoplasmic reticulum stress and autophagy on different cell types [10]. Therefore, the contribution of oxysterols is widely suspected in major diseases such as cancer, metabolic syndrome, osteoporosis, cataract, age related macular degeneration, cardiovascular and neurodegenerative diseases [11]. Consequently, it is expected that a better knowledge of the biological activities of phytosterols, of the metabolism of oxysterols, and of their associated signaling pathways will permit to identify new drugs and to develop efficient treatments, mainly in pathologies where the therapeutic arsenal is weak (neurodegenerative diseases, metabolic syndrome) or needs to be improved (cancer, aged related diseases (cardiovascular and eye diseases, osteoporosis, etc.)). In addition, the possibility to use some oxysterols as disease and therapeutic biomarkers is very promising