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Agonist of RORA Attenuates Non-Alcoholic Fatty Liver Progression in Mice via Upregulation of microRNA 122.

BACKGROUND AND AIMS
Development of non-alcoholic steatohepatitis (NASH) is associated with reductions in hepatic microRNA122 (MIR122); the RAR related orphan receptor A (RORA) promotes expression of MIR122. Increasing expression of RORA in livers of mice increases expression of MIR122 and reduces lipotoxicity. We investigated the effects of a RORA agonist in mouse models of NASH.


METHODS
We screened a chemical library to identify agonists of RORA and tested their effects on a human hepatocellular carcinoma cell line (Huh7). C57BL/6 mice were fed a chow or high-fat diet for 4 weeks to induce fatty liver. Mice were given hydrodynamic tail vein injections of a MIR122 antagonist (antagomiR-122) or a control antagomiR once each week for 3 weeks while still on the HFD or chow diet, or intraperitoneal injections of the RORA agonist RS-2982 or vehicle, twice each week for 3 weeks. Livers, gonad white adipose, and skeletal muscle were collected and analyzed by RT-PCR, histology and immunohistochemistry. A separate group of mice were fed an atherogenic diet, with or without injections of RS-2982 for 3 weeks; livers were analyzed by immunohistochemistry and plasma was analyzed for levels of aminotransferases. We analyzed data from liver tissues from patients with NASH included in the RNAseq databases GSE33814 and GSE89632.


RESULTS
Injection of mice with antagomiR-122 significantly reduced levels of MIR122 in plasma, liver, and white adipose tissue; in mice on a HFD, antagomiR-122 injections increased fat droplets and total triglyceride content in liver and reduced β-oxidation and energy expenditure, resulting in significantly more weight gain than in mice given the control microRNA. We identified RS-2982 as an agonist of RORA and found it to increase expression of MIR122 promoter activity in Huh7 cells. In mice fed a HFD or atherogenic diet, injections of RS-2982 increased hepatic levels of MIR122 precursors and reduced hepatic synthesis of triglycerides, by reducing expression of biosynthesis enzymes. In these mice, RS-2982 significantly reduced hepatic lipotoxicity, reduced liver fibrosis, increased insulin resistance, and reduced body weight, compared with mice injected with vehicle. Patients who underwent cardiovascular surgeries had increased levels of plasma MIR122 compared to its levels before the surgeries; increased expression of plasma MIR122 was associated with increased levels of plasma free fatty acids and levels of RORA.


CONCLUSIONS
We identified the compound RS-2982 as an agonist of RORA that increases expression of MIR122 in cell lines and livers of mice. Mice fed a HFD or atherogenic diet given injections of RS-2982 had reduced hepatic lipotoxicity, liver fibrosis, and body weight, compared with mice given the vehicle. Agonists of RORA might be developed for treatment of NASH.