摘要
more than 20 years ago,and immediately emerged as a master regulator of aging-related processes,which basically operates as an anti-aging factor.It is expressed through the entire human body,representing the choroid plexus and the kidney as the most active sources at the central nervous system(CNS)and periphery level respectively.To a lesser extent,also the parathyroid gland,the adipose tissue,and the liver express KL.KL is a transmembrane protein serving as an essential co-receptor for fibroblast growth factor receptors,but,in general,it mediates a number of molecular pathways and biological functions at a multisystem level.In fact,even a soluble form exists,originated by the extracellular domain cleavage,which circulates in human fluids,allowing a sort of systemic signaling.Although all the tissue-specific actions have not been completely clarified,there is solid evidence that KL regulates basic mineral homeostasis and internal metabolism pathways.
