ApoM, short for apolipoprotein M, is a member of the apolipoprotein family. It is primarily expressed and secreted from the liver and kidneys. ApoM is the main chaperone of sphingosine-1-phosphate (S1P), a small signalling molecule involved in numerous physiologic and pathophysiologic processes. It is also associated with lipid metabolism, and 95% of plasma ApoM is found associated with high-density lipoproteins (HDL) [1,2,3].

ApoM-deficient mice display an increased activity in brown adipose tissue and a concomitant fast turnover of triglycerides, suggesting that the ApoM/S1P axis plays a significant role in maintaining a balanced triglyceride metabolism [4]. In addition, in a female human ApoM transgenic mouse model with increased plasma ApoM and S1P levels, there was a reduced plasma triglyceride turnover rate and lower free fatty acid uptake in subcutaneous adipocytes [4].

In conclusion, ApoM is essential for transporting S1P and is involved in lipid metabolism. Mouse models, such as ApoM-deficient and ApoM transgenic mice, have revealed its role in triglyceride metabolism. Understanding ApoM's function can potentially provide new insights into the treatment of diseases related to lipid metabolism disorders [4].