2496-P: Hepatocyte-Specific Estrogen Receptor Alpha Knockdown Exacerbates HFD-Induced MASLD

Introduction and Objective: Metabolic Dysfunction-Associated Steatotic Liver Disease (MASLD) exhibits distinct sexual dimorphism, with premenopausal women displaying significant protection compared to men. This study investigated the impact of hepatocyte-specific Estrogen Receptor Alpha (ERα) knockdown on MASLD development. Methods: Female C57BL/6J mice were treated with AAV8-TBG-GFP-mESR1-shRNAmir to knockdown ERα (AAV) or Vehicle (V) and fed a Regular Chow (RC) or High-Fat Diet (HFD) for 9 weeks. Statistical analyses: Two-way ANOVA followed by Fisher’s LSD test (p<0.05). Results: HFD-AAV presented ~49% and ~59% lower liver ERα vs.HFD-V and RC-AAV, respectively. RC-AAV showed ~20% lower liver ERα vs. RC-V. HFD-AAV exhibited ~43% lower Esr1 mRNA expression vs. HFD-V, while RC-AAV exhibited a ~70% reduction vs. RC-V. Compared to their respective RC controls, HFD-V and HFD-AAV showed higher final body weight (~31%; ~30%), body fat (~116%; ~119%), and lean mass (~21%; ~24%). HFD-V and HFD-AAV displayed increased glucose intolerance (~52%; ~56%) vs. RC controls. AUC of insulinemia during oGTT did not differ. However, HFD-V and HFD-AAV had higher fasting plasma glucose (~20%; ~23%), lower fasting plasma insulin (~11%; ~6%) and HOMA-β (~33%; ~52%) vs. RC controls. HFD-AAV showed increased fasting plasma glucose (~15%) and HOMA-IR (~22%) vs. HFD-V. Insulin-stimulated hepatic levels of p-AKT2/Total AKT, plasma triglycerides and hepatic cholesterol did not differ between groups. HFD-V and HFD-AAV displayed increased plasma cholesterol (~10%; ~17%) vs. RC controls. Hepatic triglycerides and ORO area were ~39% and ~77%, respectively, higher in HFD-AAV vs. HFD-V. Plasma ALT and AST levels increased by ~66% and ~15%, respectively, while hepatic Tgfb mRNA expression increased ~200% in HFD-AAV vs. HFD-V. Conclusion: Hepatocyte-specific ERα knockdown worsens HFD-induced hepatic steatosis, liver injury, and glucose metabolism. These findings underscore the critical protective role of hepatic ERα signaling against MASLD progression in females. Disclosure F.N. Camargo: None. L.F. Amaro: None. A.L. Dias Maciel: None. A.R. Melo Santos: None. A. Goncalves da Cruz: None. J.D. dos Santos: None. S.L. Matos: None. F. Sucupira: None. J.F. Model: None. J. Camporez: None. Funding Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP); Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq); Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES).