Treatment of non-alcoholic steatohepatitis with recombinant Orosomucoid 2, an acute phase protein that attenuates the Erk1/2-PPARγ-Cd36 signaling pathway

Therapeutic administration of recombinant proteins has been used for the treatment of various diseases in multiple studies. Herein, we investigated the function of the acute phase protein Orosomucoid 2 (Orm2), which is mainly secreted by hepatocytes, and evaluated its potential as a therapeutic strategy for non-alcoholic fatty liver disease (NAFLD) and non-alcoholic steatohepatitis (NASH). We here revealed that a high expression of Orm2 protected mice from high-fat diet (HFD)-induced obesity. The pharmacological administration of recombinant ORM2 protein attenuated hepatic steatosis, inflammation, hepatocyte injury, and fibrosis in mouse livers, which suffered NAFLD and NASH under dietary challenge conditions. Orm2 knockout mice spontaneously underwent obese after 16 weeks under normal diet. Orm2 deficiency exacerbated HFD-induced steatosis, steatohepatitis, and fibrosis in mice. Mechanistically, the deletion of Orm2 led to the activation of the Erk1/2-PPARγ-Cd36 signaling pathway, which in turn increased fatty acid uptake and absorption in hepatocytes and mice. Collectively, our results provide Orm2 is an essential factor for preventing NASH and associated NAFLD under obesity. ### Competing Interest Statement The authors have declared no competing interest. * Acsl1 : acyl-CoA synthetase long chain family member 1 ALT : alanine aminotransferase Ap2 : integrase-type DNA-binding superfamily protein AST : aspartate aminotransferase Atgl : Adipose triglyceride lipase BAT : brown adipose tissue BCA : bicinchoninic acid Cpt1ɑ : carnitine palmitoyltransferase 1A Cxcl10 : C-X-C motif chemokine ligand 10 Dgat : diacylglycerol O-acyltransferase ECL : enhanced chemiluminescence Erk1/2 : mitogen-activated protein kinase eWAT : epididymal white adipose tissue Fasn : Fatty Acid Synthase FFA : free fatty acid FGF : fibroblast growth factor HDL : high-density lipoprotein H&E : hematoxylin and eosin HFD : high fat diet IL1β : interleukin 1 beta IP-ITT : intraperitoneal insulin-tolerance tests IPTG : isopropyl-β-D-1-thiogalactopyranoside ITPR2 : inositol 1,4,5-trisphosphate receptor type 2 KO : Orm2 knockout mice LDL : low-density lipoprotein MCD : methionine and choline-deficient L-amino acid diet Mcp1 : Monocyte chemoattractant protein-1 NAFLD : non-alcoholic fatty liver disease NASH : non-alcoholic steatohepatitis NCBI : national center for biotechnology information OA : oleic acid O-GTT : oral glucose tolerance Orm2 : Orosomucoid 2 PA : palmitic acid PMSF : phenylmethanesulfonylfluoride or phenylmethylsulfonyl fluorid PPAR : peroxisome proliferator activated receptor RT-qPCR : real time quantitative PCR SHBG : sex hormone-binding globulin SMA : smooth muscle STAT1 : Signal Transducer And Activator Of Transcription TBST : Tris buffered saline with Tween-20 TC : total cholesterol TG : triglyceride T2DM : type 2 diabetes mellitus WT : wild type mice