Abstract
Background and Aims Nonalcoholic steatohepatitis (NASH) is a chronic liver disease characterized by hepatic lipid accumulation, inflammation, and progressive fibrosis. However, the pathomechanisms underlying NASH are incompletely explored. Phosphoenolpyruvate carboxykinase 1 (PCK1) catalyzes the first rate-limiting step of gluconeogenesis in the cytoplasm. This study was designed to determine the role of PCK1 in regulating NASH progression.
Methods Liver metabolism, hepatic steatosis, and fibrosis were evaluated at 24 weeks in liver-specific Pck1-knockout (L-KO) mice fed with NASH diet (high fat diet with ad libitum consumption of water containing glucose and fructose). AKT and RhoA inhibitors were evaluated for disease treatment in L-KO mice fed NASH diet.
Results PCK1 is downregulated in patients with NASH and mouse models of NASH. L-KO mice displayed hepatic lipid disorder and liver injury fed with normal diet, while fibrosis and inflammation were aggravated when fed NASH diet. Mechanistically, transcriptome analysis revealed PCK1 deficiency upregulated genes involved in fatty acid transport and lipid droplet formation. Moreover, untargeted metabolomics analysis showed the accumulation of glycerol 3-phosphate, the substrate of triglyceride synthesis. Furthermore, the loss of PCK1 could activate the RhoA/PI3K/AKT pathway, which leads to increased secretion of PDGF-AA and promotes the activation of hepatic stellate cells. RhoA and AKT inhibitors alleviated NASH progression in L-KO mice fed NASH diet.
Conclusions PCK1 deficiency plays a key role in the development of hepatic steatosis and fibrosis by facilitating the RhoA/PI3K/AKT/PDGF-AA axis. These findings provide a novel insight into therapeutic approaches for the treatment of NASH.
Lay summary Non-alcoholic steatohepatitis (NASH) is currently the most common chronic liver disease, which is correlated with progressing chronic disorder of lipid metabolism and a persistent inflammatory response. In the present study, decreased PCK1 is observed in patients with NASH and mouse NASH models, and its loss aggravates steatohepatitis in NASH mice fed high-fat, high-fructose diet by stimulating expression of lipogenic genes and lipid synthesis. Inhibitors of proteins involved in the underlying molecular process alleviated the liver disease, highlighting a new therapeutic strategy for NASH.
Graphical abstractHighlights
Gluconeogenic enzyme PCK1 is downregulated in both human patients and NASH mice.
PCK1 depletion promotes hepatic steatosis by dysregulating lipid metabolism and synthesis.
PCK1 loss promotes hepatic fibrosis by activating RhoA/PI3K/AKT/PDGF-AA axis.
Targeting RhoA/AKT alleviates NASH progression in liver-specific Pck1-knockout mice.
Competing Interest Statement
The authors have declared no competing interest.
Abbreviations
- AKT
- protein kinase B
- ALT
- Alanine transaminase
- AST
- aspartate transaminase
- α-SMA
- alpha-smooth muscle actin (ACTA2)
- ATF3
- Activating Transcription Factor 3
- bZIP
- Basic Leucine Zipper Domain
- ChIP
- chromatin immunoprecipitation
- CIDEC and CIDEA
- cell death inducing DFFA like effector C and A
- COL1A1, COL1A3
- recombinant collagen type I alpha 1 and alpha 3
- CD36
- fatty acid translocase
- DNL
- de novo lipogenesis
- FFA
- free fatty acid
- G3P
- glycerol 3-phosphate
- GTT
- glucose tolerance test
- GSEA
- Gene Set Enrichment Analysis
- HE
- hematoxylin and eosin
- ITT
- insulin tolerance test
- Lama2
- laminin subunit alpha 2
- L-KO
- liver-specific Pck1-knockout mice
- NASH
- non-alcoholic steatohepatitis
- NAFLD
- non-alcoholic fatty liver disease
- NAS
- NAFLD activity score
- PCK1
- Phosphoenolpyruvate carboxykinase 1
- PCK1
- Phosphoenolpyruvate carboxykinase 1
- PDGF-AA
- platelet-derived growth factor AA
- PI3K
- phosphatidylinositol 3-kinase
- PPAR
- Peroxisome Proliferator-Activated Receptor
- RhoA
- Ras homolog family member A
- SLC27A1
- solute carrier family 27 member 1
- TC
- total cholesterol
- TG
- Triglyceride