Apolipoprotein M is a secreted protein which belongs to the Lipocalin family. ApoM often presents in high density lipoprotein (HDL) and to a lesser extent in triglyceride-rich lipoproteins (TGRLP) and low density lipoproteins (LDL). The ApoM gene encoded protein is expressed in liver and kidney, secreted through the plasma membrane but remains membrane-bound. ApoM probably involved in lipid transport. ApoM can bind sphingosine-1-phosphate, myristic acid, palmitic acid and stearic acid, retinol, all-trans-retinoic acid and 9-cis-retinoic acid. The expression of ApoM could be regulated by platelet activating factor (PAF), Transforming Growth Factors (TGF), Insulin-Like Growth factor (IGF) and Leptin.