Angiotensinogen in hepatocytes contributes to Western diet-induced liver steatosis

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Nonalcoholic fatty liver disease (NAFLD) is considered as a liver manifestation of metabolic disorders. Previous studies indicate that the renin-angiotensin system (RAS) plays a complex role in NAFLD. As the only precursor of the RAS, decreased angiotensinogen (AGT) profoundly impacts RAS bioactivity. Here, we investigated the role of hepatocyte-derived AGT in liver steatosis. AGT floxed mice (hepAGT+/+) and hepatocyte-specific AGT-deficient mice (hepAGT−/−) were fed a Western diet and a normal laboratory diet for 12 weeks, respectively. Compared with hepAGT+/+ mice, Western diet-fed hepAGT−/− mice gained less body weight with improved insulin sensitivity. The attenuated severity of liver steatosis in hepAGT−/− mice was evidenced by histologic changes and reduced intrahepatic triglycerides. The abundance of SREBP1 and its downstream molecules, acetyl-CoA carboxylase and FASN, was suppressed in hepAGT−/− mice. Furthermore, serum derived from hepAGT+/+ mice stimulated hepatocyte SREBP1 expression, which could be diminished by protein kinase B (Akt)/mammalian target of rapamycin (mTOR) inhibition in vitro. Administration of losartan did not affect diet-induced body weight gain, liver steatosis severity, and hepatic p-Akt, p-mTOR, and SREBP1 protein abundance in hepAGT+/+ mice. These data suggest that attenuation of Western diet-induced liver steatosis in hepAGT−/− mice is associated with the alternation of the Akt/mTOR/SREBP-1c pathway.