The Interaction Of Apolipoprotein M With Bile Acids And The Probable Mechanisms

ObjectivesApolipoprotein M (apoM) is a recently discovered apolipoprotein. At present, the regulations and biological functions of apoM and the relationships between apoM and diseases remain unknown. Bile acids (BAs) are a series of products of cholesterol metabolism that participate in the metabolism of lipids by activating the farnesoid X receptor (FXR).The aim of this study was to analyze the correlations between apoM and BAs in healthy individuals, and further investigate the serum levels of apoM in obstructive jaundice (OJ) patients with increased total bile acids (TBA). And then the role of apoM on the expression of FXR, which is a well known regulating factor of BAs, was further analyzed, aiming to discuss the probable mechanisms of the interaction between apoM and BAs.Methods1. Sanwich ELISA method was used to detect the serum levels of apoM in healthy individuals and patients with OJ. The correlations of apoM and TBA were analyzed.2. ApoM plasmid and siRNA were transfected to overexpress and silence the apoM gene in HepG2cells, and the FXR gene expression were observed.Results1. The serum levels of apoM were positively correlated with TBA in healthy individuals (P<0.05).2.Compared to healthy individuals, the serum levels of apoM in patients with OJ was obviousely increased, while the levels of apoAI and Lp (a) were significantly decreased. The levels of apoM were positively correlated with TBA while apoAI and Lp (a) were negatively correlated with it (P<0.05).3. FXR gene was not expressed in control and apoM gene overexpressed HepG2cells. But FXR was expressed after silencing apoM gene by siRNA.Conclusions1. Serum levels of apoM were positively correlated with TBA in healthy individuals. ApoM in patients with OJ were significantly increased and were also positively correlated with TBA. So it is inferred that there are close relationships between apoM and BAs.2. Silencing apoM gene with siRNA upregulated FXR gene expression. So it implies that apoM could regulate the metabolisms of BAs via the FXR pathway.3. FXR may act as a cross point between BAs and apoM.