Hepatocyte-Specific Deletion of eNOS Impairs Mitochondrial Function and Exacerbates Hepatic Steatosis

Introduction Whole body loss of endothelial nitric oxide synthase (eNOS) worsens hepatic mitochondrial function and exacerbates nonalcoholic fatty liver disease (NAFLD) development and progression. However, the precise role of eNOS in hepatocytes in the contribution to NAFLD has not been established. Here, we examine the effects of in vivo hepatocyte‐specific ablation of eNOS on hepatic steatosis and NAFLD susceptibility. Methods Hepatocyte‐specific eNOS knockout ( eNOS hep − / − ) mice were generated by crossing homozygous eNOS floxed ( eNOS fl/fl ) mice on a C57/BL6J background with albumin‐Cre recombinase transgenic mice. At 10 weeks of age, male eNOS fl/fl and eNOS hep − / − mice ( n = 12–14) were fed a control diet (10% fat) for 16 weeks. Results Body weight, body fat, and food intake did not differ between eNOS fl/fl and eNOS hep − / − mice. eNOS hep − / − mice developed elevated histological hepatic steatosis and increased fasting serum insulin (~30%) compared to eNOS fl/fl mice (p<0.05), along with trends for elevations in serum liver enzymes AST and ALT (p<0.17). Elevated hepatic steatosis in eNOS hep − / − was related to significant reductions (−50%) in hepatic mitochondrial fatty acid oxidation and ADP‐stimulated and maximal uncoupled hepatic mitochondrial respiration (p<0.05). However, hepatic citrate synthase activity, a marker of mitochondrial mass, was significantly elevated in eNOS hep − / − mice compared to eNOS fl/fl mice (p<0.05), while protein content of oxidative phosphorylation complexes and peroxisome proliferator‐activated receptor‐γ coactivator‐1α (PGC‐1α) did not differ between groups. Furthermore, eNOS hep − / − mice presented with significant reductions (p<0.05) in key proteins involved in mitophagy and autophagy including PTEN‐induced kinase 1 (PINK1) and phosphorylated Unc‐51 Like Autophagy Activating Kinase 1 (pUlk1/Ulk1) and tended to have significant reductions in BCL2/adenovirus E1B 19 kDa protein‐interacting protein 3 (BNIP3) compared to eNOS fl/fl mice. Conclusion Here we demonstrate for the first time that hepatocyte‐specific deletion of eNOS impairs hepatic mitochondrial function, reduces markers of autophagy/mitophagy, and exacerbates hepatic steatosis development. Further studies are necessary to determine the mechanisms by which deletion of eNOS regulates mitochondrial homeostasis. Support or Funding Information VA Merit Grant I01BX003271‐01 (R.S.R.) This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal .