Hepatocyte X-box binding protein 1 deficiency increases liver injury in mice fed a high-fat/sugar diet

Am J Physiol Gastrointest Liver Physiol. 2015 Dec 15;309(12):G965-74. doi: 10.1152/ajpgi.00132.2015. Epub 2015 Oct 15.

Abstract

Fatty liver is associated with endoplasmic reticulum stress and activation of the hepatic unfolded protein response (UPR). Reduced hepatic expression of the UPR regulator X-box binding protein 1 spliced (XBP1s) is associated with human nonalcoholic steatohepatitis (NASH), and feeding mice a high-fat diet with fructose/sucrose causes progressive, fibrosing steatohepatitis. This study examines the role of XBP1 in nonalcoholic fatty liver injury and fatty acid-induced cell injury. Hepatocyte-specific Xbp1-deficient (Xbp1(-/-)) mice were fed a high-fat/sugar (HFS) diet for up to 16 wk. HFS-fed Xbp1(-/-) mice exhibited higher serum alanine aminotransferase levels compared with Xbp1(fl/fl) controls. RNA sequencing and Gene Ontogeny pathway analysis of hepatic mRNA revealed that apoptotic process, inflammatory response, and extracellular matrix structural constituent pathways had enhanced activation in HFS-fed Xbp1(-/-) mice. Liver histology demonstrated enhanced injury and fibrosis but less steatosis in the HFS-fed Xbp1(-/-) mice. Hepatic Col1a1 and Tgfβ1 gene expression, as well as Chop and phosphorylated JNK (p-JNK), were increased in Xbp1(-/-) compared with Xbp1(fl/fl) mice after HFS feeding. In vitro, stable XBP1-knockdown Huh7 cells (Huh7-KD) and scramble control cells (Huh7-SCR) were generated and treated with palmitic acid (PA) for 24 h. PA-treated Huh7-KD cells had increased cytotoxicity measured by lactate dehydrogenase release, apoptotic nuclei, and caspase3/7 activity assays compared with Huh7-SCR cells. CHOP and p-JNK expression was also increased in Huh7-KD cells following PA treatment. In conclusion, loss of XBP1 enhances injury in both in vivo and in vitro models of fatty liver injury. We speculate that hepatic XBP1 plays an important protective role in pathogenesis of NASH.

Keywords: endoplasmic reticulum stress; fatty liver; nonalcoholic steatohepatitis; steatosis; unfolded protein response.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Alanine Transaminase / blood
  • Animals
  • Apoptosis
  • Cell Line, Tumor
  • Collagen Type I / genetics
  • Collagen Type I / metabolism
  • DNA-Binding Proteins / deficiency*
  • DNA-Binding Proteins / genetics
  • Diet, High-Fat*
  • Dietary Sucrose*
  • Gene Expression Regulation
  • Hepatocytes / drug effects
  • Hepatocytes / metabolism*
  • Hepatocytes / pathology
  • Humans
  • JNK Mitogen-Activated Protein Kinases / metabolism
  • Liver / drug effects
  • Liver / metabolism*
  • Liver / pathology
  • Liver Cirrhosis, Experimental / genetics
  • Liver Cirrhosis, Experimental / metabolism*
  • Liver Cirrhosis, Experimental / pathology
  • Male
  • Mice, Inbred C57BL
  • Mice, Knockout
  • Non-alcoholic Fatty Liver Disease / etiology
  • Non-alcoholic Fatty Liver Disease / genetics
  • Non-alcoholic Fatty Liver Disease / metabolism*
  • Non-alcoholic Fatty Liver Disease / pathology
  • Palmitic Acid / toxicity
  • Phosphorylation
  • RNA, Messenger / metabolism
  • Regulatory Factor X Transcription Factors
  • Signal Transduction
  • Time Factors
  • Transcription Factor CHOP / genetics
  • Transcription Factor CHOP / metabolism
  • Transcription Factors / deficiency*
  • Transcription Factors / genetics
  • Transfection
  • Transforming Growth Factor beta1 / genetics
  • Transforming Growth Factor beta1 / metabolism
  • X-Box Binding Protein 1

Substances

  • Collagen Type I
  • DDIT3 protein, human
  • DNA-Binding Proteins
  • Ddit3 protein, mouse
  • Dietary Sucrose
  • RNA, Messenger
  • Regulatory Factor X Transcription Factors
  • Tgfb1 protein, mouse
  • Transcription Factors
  • Transforming Growth Factor beta1
  • X-Box Binding Protein 1
  • XBP1 protein, human
  • Xbp1 protein, mouse
  • collagen type I, alpha 1 chain
  • Transcription Factor CHOP
  • Palmitic Acid
  • Alanine Transaminase
  • JNK Mitogen-Activated Protein Kinases