An Innovative Liver-Specific GalNAc-RNAi Suppression of UGT1A1 in Obese Mice Improves Metabolic-Associated Fatty Liver Disease (MAFLD)

Several population studies have found lower serum bilirubin levels to be associated with the pathology of metabolic-associated fatty liver disease (MAFLD). Yet, treatments to target this metabolic trend have not been explored. In our study, we hypothesized that inhibition of hepatic UGT1A1 would increase serum bilirubin levels and improve conditions like MAFLD and hepatic insulin resistance. Therefore, we designed an RNAi targeting murine Ugt1a1 expression in the liver. The RNAi molecule was constructed by conjugating it with an amino sugar derivative of galactose, N-Acetylgalactosamine (GalNAc) [GalNAc-UGT1A1-RNAi]. GalNAc covalently linked to the siRNA enables delivery through the asialoglycoprotein receptor (ASGPR)-mediated targeting to hepatocytes in vivo. Hence, the treatment of the GalNAc-UGT1A1-RNAi primarily targets the liver. In this study, male C57BL/6J mice were fed a high-fat diet (HFD, 60%) for 30 weeks for diet-induced obesity (DIO) and were treated subcutaneously with GalNAc-UGT1A1-RNAi (3mg/kg, n=7) or sham control (n=6) once weekly the final 4 weeks while on the HFD. The results show that GalNAc-UGT1A1-RNAi treatment significantly raised serum bilirubin levels compared to sham control-treated (0.38±0.01 vs. 1.36±0.08 mg/dL, Sham vs. GalNAc-UGT1A1-RNAi, p<0.05), decreased hepatic fat content (26 ± 1.4 vs. 18 ± 1 %, p<0.05) and hepatic triglycerides (17±1.5 vs. 11.5±1 nM, p<0.05), and improved fasting blood glucose (261±11 vs. 201±8 mg/dL, p<0.05) and insulin (9.9±0.1 vs. 3.5±0.3 ng/ml, p<0.05) levels. We performed extensive kinase activity analyses using PamGene PamStation technology and found a significant increase in insulin receptor downstream mediators such as SRC, AKT, and ERK kinase families with the GalNAc-UGT1A1-RNAi treatment, indicating improved hepatic insulin sensitivity. These results show that GalNAc-UGT1A1-RNAi improves MAFLD, increases serum bilirubin, reduces its catabolized produce urobilin in the plasma, and reduces hyperglycemia and hyperinsulinemia. These indicate that UGT1A1 antagonism might serve as a treatment for MAFLD and hepatic insulin resistance, which could improve obesity-associated comorbidities. This work was supported by the National Institutes of Health 1R01DK121797-01A1 (T.D.H.) and 1R01DK126884-01 (D.E.S.), the National Heart, Lung and Blood Institute K01HL-125445 (T.D.H.) and P01 HL05197-11 (D.E.S.), and the National Institute of General Medical Sciences P20GM104357-02 (D.E.S.). The content is solely the responsibility of the authors and does not necessarily represent the official views of the National Institutes of Health. This is the full abstract presented at the American Physiology Summit 2023 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.