CCAAT/enhancing binding protein beta deletion in mice attenuates inflammation, endoplasmic reticulum stress, and lipid accumulation in diet-induced nonalcoholic steatohepatitis.
Nonalcoholic steatohepatitis (NASH) is characterized by steatosis, inflammation, and oxidative stress. To investigate whether the transcription factor CCAAT/Enhancer binding protein (C/EBPbeta) is involved in the development of NASH, C57BL/6J wild-type (WT) or C/EBPbeta knockout (C/EBPbeta-/-) mice were fed either a methionine and choline deficient (MCD) diet or standard chow. These WT mice fed a MCD diet for 4 weeks showed a 2- to 3-fold increase in liver C/EBPbeta messenger RNA and protein, along with increased expression of lipogenic genes peroxisome proliferators-activated receptor gamma and Fas. WT mice also showed increased levels of the endoplasmic reticulum stress pathway proteins phosphorylated eukaryotic translation initiation factor alpha, phosphorylated pancreatic endoplasmic reticulum kinase, and C/EBP homologous protein, along with inflammatory markers phosphorylated nuclear factor kappaB and phosphorylated C-jun N-terminal kinase compared to chow-fed controls. Cytochrome P450 2E1 protein and acetyl coA oxidase messenger RNA involved in hepatic lipid peroxidation were also markedly increased in WT MCD diet-fed group. In contrast, C/EBPbeta-/- mice fed a MCD diet showed a 60% reduction in hepatic triglyceride accumulation and decreased liver injury as evidenced by reduced serum alanine aminotransferase and aspartate aminotransferase levels, and by H&E staining. Immunoblots and real-time qPCR data revealed a significant reduction in expression of stress related proteins and lipogenic genes in MCD diet-fed C/EBPbeta-/- mice. Furthermore, circulating TNFalpha and expression of acute phase response proteins CRP and SAP were significantly lower in C/EBPbeta-/- mice compared to WT mice. Conversely, C/EBPbeta over-expression in livers of WT mice increased steatosis, nuclear factor-kappaB, and endoplasmic reticulum stress, similar to MCD diet-fed mice.


CONCLUSIONS
Taken together, these data suggest a previously unappreciated molecular link between C/EBPbeta, hepatic steatosis and inflammation and suggest that increased C/EBPbeta expression may be an important factor underlying events leading to NASH.
Rahman
Shaikh Mizanoor
SM
Department of Pediatrics, University of Colorado at Denver and Health Sciences Center, Aurora, CO 80045, USA.
Schroeder-Gloeckler
Jill M
JM
Janssen
Rachel C
RC
Jiang
Hua
H
Qadri
Ishtiaq
I
Maclean
Kenneth N
KN
Friedman
Jacob E
JE
D000210:Acute-Phase Reaction / Q000503:physiopathology; D000818:Animals; D001835:Body Weight; D022782:CCAAT-Enhancer-Binding Protein-beta / Q000172:deficiency / Q000235:genetics* / Q000502:physiology*; D002796:Choline Deficiency / Q000150:complications / Q000503:physiopathology; D019392:Cytochrome P-450 CYP2E1 / Q000096:biosynthesis; D004032:Diet; D004195:Disease Models, Animal; D004721:Endoplasmic Reticulum / Q000502:physiology*; D015852:Eukaryotic Initiation Factor-2 / Q000378:metabolism; D005234:Fatty Liver / Q000209:etiology / Q000503:physiopathology*; D007249:Inflammation / Q000209:etiology; D048031:JNK Mitogen-Activated Protein Kinases / Q000378:metabolism; D008049:Lipase / Q000378:metabolism; D008099:Liver / Q000473:pathology; D008297:Male; D008715:Methionine / Q000172:deficiency; D051379:Mice; D008810:Mice, Inbred C57BL; D016328:NF-kappa B / Q000378:metabolism; D051742:Transcription Factor CHOP / Q000378:metabolism; D014409:Tumor Necrosis Factor-alpha / Q000378:metabolism; D019892:eIF-2 Kinase / Q000378:metabolism
D022782:CCAAT-Enhancer-Binding Protein-beta; D019392:Cytochrome P-450 CYP2E1; D015852:Eukaryotic Initiation Factor-2; D048031:JNK Mitogen-Activated Protein Kinases; D008049:Lipase; D008715:Methionine; D016328:NF-kappa B; D051742:Transcription Factor CHOP; D014409:Tumor Necrosis Factor-alpha; D019892:eIF-2 Kinase; C497250:Ddit3 protein, mouse