Sirtuin modulators: mechanisms and potential clinical implications

In the last years, studies about longevity have highlighted that caloric restriction can be linked with a less normal agingassociated damage, and in the same way, with the activity of the Silent Information Regulator 2 (SIR2) gene. Sir2-like genes, known as sirtuins (SIRTs), have been found in organisms ranging from bacteria to mammals promoting health and survival. At the moment, it has been identified seven classes of SIRTs in mammalian and the understanding of many of them remains still rudimentary. However, they are in the spotlight by their potential protection against aging-associated diseases and have emerged as key mediators of longevity in evolutionarily distant organisms models. SIRTs are proteins found in numerous compartments within the cell, which are NAD(+)-dependent protein deacetylases and adenosine diphosphate (ADP)-ribosyltransferases. They catalyse a reaction in which NAD(+) and an acetylated substrate are converted into a deacetylated substrate, nicotinamide and a novel metabolite O-acetyl ADP ribose. Therefore, its enzymatic activity requires NAD(+), which is a crucial molecule intermediary of many metabolic reactions in cells. Basically, SIRTs are mediators of aging process, they have the potential of ameliorating and taking part in important cellular processes associated, such as metabolic homeostasis, tumorigenesis and cancer cell proliferation, inflammatory disorders, cardiovascular diseases and neurodegeneration. This background opens up new lines of investigation into the modulation of SIRTs activity in order to develop novel therapeutic targets to these age-related diseases. Current experiments using molecule activators or inhibitors and genetically engineered animals have facilitated new insights into the role of these enzymes and contributed to highlight some of the potentially relevant targets. This review is intended to provide an appreciation of the possible protection against aging-associated diseases by these enzymes, summarize novel underlying mechanisms and evaluate potential clinical applications.