The Hepatokine Orosomucoid 2 Mediates Beneficial Metabolic Effects of Bile Acids.

Abstract

Bile acids (BAs) are pleiotropic regulators of metabolism. Elevated levels of hepatic and circulating BAs improve energy metabolism in peripheral organs, but the precise mechanisms underlying the metabolic benefits and harm still need to be fully understood. In the present study, we identified orosomucoid 2 (ORM2) as a liver-secreted hormone (i.e., hepatokine) induced by BAs and investigated its role in BA-induced metabolic improvements in mouse models of dietinduced obesity. Contrary to our expectation, under a high-fat diet (HFD), our Orm2 knockout (Orm2-KO) exhibited a lean phenotype compared to C57BL/6J control, partly due to the increased energy expenditure. However, when challenged with HFD supplemented with cholic acid (HFDCA), Orm2-KO eliminated the anti-obesity effect of BAs, indicating that ORM2 governs BA-induced metabolic improvements. Moreover, hepatic ORM2 overexpression partially replicated BA effects by enhancing insulin sensitivity. Mechanistically, ORM2 suppressed IFNγ/STAT1 activities in inguinal WAT (iWAT) depots, forming the basis for anti-inflammatory effects of BAs and improving glucose homeostasis. In conclusion, our study provides new insights into the molecular mechanisms of BA-induced liver-adipose crosstalk through ORM2 induction.