10 - Mice Deficient in Pde3a Develop Characteristic Findings of Nonalcoholic Steatohepatitis

Poster Number: 10
Publication Number: 10.207

Gabrielle McGeorge, Nationwide Children's Hospital, Westerville, OH, United States; Xiaomei Meng, Ohio State University College of Medicine, Columbus, OH, United States; Krista LaPerle, Takeda Pharmaceutical Company, Worthington, OH, United States; Leif D. Nelin, Nationwide Children's Hospital, Coumbus, OH, United States; Yusen Liu, Nationwide Children's Hospital, Columbus, OH, United States; Bernadette Chen, The Ohio State University College of Medicine, Columbus, OH, United States

Background: Nonalcoholic fatty liver disease (NAFLD) is the most common form of chronic liver disease in children. NAFLD comprises a spectrum of diseases based on histology, ranging from NAFL to the inflammatory subtype nonalcoholic steatohepatitis (NASH). We found that global phosphodiesterase 3A (Pde3a)-deficient mice are small, develop rectal prolapse and have histologic evidence of NASH with micro/macrovesicular fatty changes, hepatocellular coagulation necrosis with inflammatory infiltrates, and fibrosis.

Objective: To explore molecular pathways mediating NASH in Pde3a-deficient mice.

Design/Methods: Male (M) and female (F) 3-5 wk-old C57bl/6J (WT) and Pde3a-/- (KO) mice with early and late progression of disease, defined by absence or presence of rectal prolapse, were sacrificed. Liver was weighed and protein harvested. PDE3A, PDE3B, FASN, SREB1c, phosphorylated (p) and total AMPK, PDK1-4, DGAT-2, and β-actin expression were quantified by Western blot (n=3 per group/gender).

Results: M+F KO liver/body weight ratios were lower than WT (0.037 vs 0.041, p< 0.0001). PDE3B protein levels were higher in M+F KO livers compared to WT (M, p< 0.001; F, p<0.02). FASN was decreased by ~60% in M+F KO vs WT livers (p < 0.05), while SREB1c was not different. AMPK phosphorylation was increased ~14-fold in F KO relative to WT livers (p < 0.001). PDK1-4 were each increased in F KO relative to WT livers (p < 0.04) and PDK2-4 were increased in M KO relative to WT livers (p < 0.05). Nonetheless, liver PDK1 and AMPK activation in M KO mice with prolapse were higher than either WT (p < 0.005) or KO mice without prolapse (p < 0.02). DGAT-2 expression increased ~4.5-fold (p < 0.03) in M and ~16-fold in F KO relative to WT livers (p < 0.002).Conclusion(s): These data suggest NASH in KO mice is unlikely a result of de novo lipogenesis based on its inhibition by AMPK and the absence of SREB1c and FASN induction in KO livers. Upregulated DGAT-2, which catalyzes the final step to convert FFA into triglycerides (TG), suggests that the fatty liver is likely the result of reassembly of TG from circulating FFA. This is consistent with the elevated PDK expression, as PDKs can be induced by high FFA for metabolic switch from carbohydrate to lipid utilization. Both PDKs and AMPK activation directly enhance FFA β-oxidation. We speculate that Pde3a deficiency results in an abnormal distribution of TG, high circulating FFA, and TG accumulation in the liver, and increased β-oxidation, which trigger production of mitochondrial reactive oxygen and toxic lipid species, lipotoxicity, and hepatic inflammation.