Increased Glutaminolysis Marks Active Scarring in Nonalcoholic Steatohepatitis Progression.

Published online

Journal Article

BACKGROUND & AIMS: Nonalcoholic steatohepatitis (NASH) occurs in the context of aberrant metabolism. Glutaminolysis is required for metabolic reprograming of hepatic stellate cells (HSCs) and liver fibrogenesis in mice. However, it is unclear how changes in HSC glutamine metabolism contribute to net changes in hepatic glutaminolytic activity during fibrosis progression, or whether this could be used to track fibrogenic activity in NASH. We postulated that increased HSC glutaminolysis marks active scarring in NASH. METHODS: Glutaminolysis was assessed in mouse NASH fibrosis models and in NASH patients. Serum and liver levels of glutamine and glutamate and hepatic expression of glutamine transporter/metabolic enzymes were correlated with each other and with fibrosis severity. Glutaminolysis was disrupted in HSCs to examine if this directly influenced fibrogenesis. 18F-fluoroglutamine positron emission tomography was used to determine how liver glutamine assimilation tracked with hepatic fibrogenic activity in situ. RESULTS: The serum glutamate/glutamine ratio increased and correlated with its hepatic ratio, myofibroblast content, and fibrosis severity. Healthy livers almost exclusively expressed liver-type glutaminase (Gls2); Gls2 protein localized in zone 1 hepatocytes, whereas glutamine synthase was restricted to zone 3 hepatocytes. In fibrotic livers, Gls2 nearly disappeared and glutamine synthase zonality was lost, but both Slc1a5 (glutamine transporter) and kidney-type Gls1 were up-regulated; Gls1 protein was restricted to stromal cells and accumulated in fibrotic septa. Hepatocytes did not compensate for decreased Gls2 by inducing Gls1. Limiting glutamine or directly inhibiting GLS1 inhibited growth and fibrogenic activity in cultured human HSCs. Compared with healthy livers, fibrotic livers were 18F-fluoroglutamine-avid by positron emission tomography, suggesting that glutamine-addicted myofibroblasts drive increased hepatic utilization of glutamine as fibrosis progresses. CONCLUSIONS: Glutaminolysis is a potential diagnostic marker and therapeutic target during NASH fibrosis progression.

Full Text

Duke Authors

Cited Authors

  • Du, K; Chitneni, SK; Suzuki, A; Wang, Y; Henao, R; Hyun, J; Premont, RT; Naggie, S; Moylan, CA; Bashir, MR; Abdelmalek, MF; Diehl, AM

Published Date

  • December 25, 2019

Published In

PubMed ID

  • 31881361

Pubmed Central ID

  • 31881361

Electronic International Standard Serial Number (EISSN)

  • 2352-345X

Digital Object Identifier (DOI)

  • 10.1016/j.jcmgh.2019.12.006

Language

  • eng

Conference Location

  • United States