Sharpe, M. C. | bioRxiv Science

bioRxiv2022

Enhancing Hepatic MBOAT7 Expression Does Not Improve Nonalcoholic Steatohepatitis in Mice

Background & AimsGenetic analyses of human NASH have revealed polymorphisms near the membrane bound O-acyl transferase domain containing 7 (MBOAT7) gene associated with worsened liver injury. NAFLD/NASH also appears to decrease MBOAT7 expression or activity independent of these polymorphisms. Thus, we hypothesized that enhancing MBOAT7 function in NASH would improve pathology. Approach & ResultsMale C57BL6/J mice were infected with adeno-associated virus 8 (AAV8) expressing MBOAT7 under control of the hepatocyte-specific thyroid hormone-binding globulin promoter, or control virus expressing green fluorescent protein (GFP). Mice were infected after NASH induction with either choline-deficient high-fat diet or Gubra Amylin NASH diet and compared to low-fat fed control mice. Both NASH diets increased liver weights, liver triglycerides, and plasma alanine and aspartate aminotransferase (ALT and AST) markers of liver injury, which were modestly yet significantly improved by MBOAT7 overexpression. However, NASH liver histology assessed by categorical scoring was not substantially improved by MBOAT7 overexpression. MBOAT7 regulates the formation of phosphatidylinositol (PI) predominantly by arachidonoylation of lysophosphatidylinositol (LPI). Shotgun lipidomics of NASH GFP-control livers suggested decreased MBOAT7 activity in that LPI content was elevated, and both total and arachidonoylated-PI were reduced. Surprisingly, MBOAT7 overexpression did not rescue the content of most arachidonoylated PI species but did normalize or increase the abundance of several oleate and linoleate-containing PI species. Free arachidonic acid was elevated but the MBOAT7 substrate arachidonoyl-CoA was found to be low in all NASH livers compared to low-fat fed mice, likely due to decreased expression of both long-chain acyl-CoA synthetases (ACSL) 1 and 4 in NASH livers compared to controls. ConclusionsThese results suggest MBOAT7 overexpression fails to measurably improve NASH pathology potentially due to insufficient abundance of its arachidonoyl-CoA substrate in fatty livers.

pathology↗

bioRxiv2020

MSDC-0602K, A Novel Insulin-Sensitizer Improves Insulinemia and Fatty Liver Disease Alone and in Addition to Liraglutide in Mice

Aims/hypothesisInsulin sensitizers and incretin mimetics are antidiabetic agents with vastly different mechanisms of action. Additionally, while thiazolidinedione (TZD) insulin sensitizers are associated with the side-effect of weight gain, glucagon-like peptide-1 receptor agonists (GLP-1RAs) can induce weight loss. We hypothesized that combination therapy with a novel TZD insulin sensitizer and the GLP-1RA Liraglutide would more significantly improve mouse models of diabetes and nonalcoholic steatohepatitis (NASH) compared to individual therapy. Methodsdb/db mice were treated with the novel TZD MSDC-0602K by oral gavage, Liraglutide (Lira) by s.c. injection, combination 0602K+Lira, or both vehicle solutions. Vehicle-treated db/+ mice were included as non-obese controls. To assess treatment effects on nonalcoholic fatty liver disease, MS-NASH mice were similarly treated with vehicle, either drug individually, or in combination. Lastly, islets were isolated from C57BL/6J mice to assess glucose-stimulated insulin secretion (GSIS). Results0602K-treated db/db mice displayed slight weight gain but completely corrected glycemia and markedly improved glucose tolerance. Lira slightly reduced body weights and modestly improved glycemia. 0602K+Lira combination still induced slight weight gain but completely corrected glycemia and improved glucose tolerance beyond lean db/+ levels. As expected, 0602K resulted in reduced plasma insulin, whereas Lira further increased the hyperinsulinemia of db/db mice. Surprisingly, 0602K+Lira treatment reduced plasma insulin and C-peptide to the same extent as mice treated with 0602K alone. 0602K did not directly reduce GSIS in isolated islets, thus the reduced insulinemia with 0602K is likely compensatory due to improved insulin action. In the MS-NASH mouse model, both 0602K or Lira alone improved plasma ALT and AST, and liver histology, but more significant improvements were observed with 0602K+Lira combination therapy. 0602K or 0602K+Lira also increased pancreatic insulin content in both db/db and MS-NASH mice. ConclusionsMSDC-0602K corrected glycemia and reduced insulinemia when given alone, or in combination with Lira. However, 0602K+Lira combination more significantly improved glucose tolerance in db/db mice, and more significantly improved liver histology in MS-NASH mice.

pharmacology and toxicology↗