Synergistic steatohepatitis by moderate obesity and alcohol in mice despite increased adiponectin and p-AMPK.
OBJECTIVE
Mechanisms underlying synergistic liver injury caused by alcohol and obesity are not clear. We have produced a mouse model of synergistic steatohepatitis by recapitulating the natural history of the synergism seen in patients for mechanistic studies.


METHODS
Moderate obesity was induced in mice by 170% overnutrition in calories using intragastric overfeeding of high fat diet. Alcohol (low or high dose) was then co-administrated to determine its effects.


RESULTS
Moderate obesity plus alcohol intake causes synergistic steatohepatitis in an alcohol dose-dependent manner. A heightened synergism is observed when a high alcohol dose (32g/kg/d) is used, resulting in plasma ALT reaching 392±28U/L, severe steatohepatitis with pericellular fibrosis, marked M1 macrophage activation, a 40-fold induction of iNos, and intensified nitrosative stress in the liver. Hepatic expression of genes for mitochondrial biogenesis and metabolism are significantly downregulated, and hepatic ATP level is decreased. Synergistic ER stress evident by elevated XBP-1, GRP78 and CHOP is accompanied by hyperhomocysteinemia. Despite increased caspase 3/7 cleavage, their activities are decreased in a redox-dependent manner. Neither increased PARP cleavage nor TUNEL positive hepatocytes are found, suggesting a shift of apoptosis to necrosis. Surprisingly, the synergism mice have increased plasma adiponectin and hepatic p-AMPK, but adiponectin resistance is shown downstream of p-AMPK.


CONCLUSIONS
Nitrosative stress mediated by M1 macrophage activation, adiponectin resistance, and accentuated ER and mitochondrial stress underlie potential mechanisms for synergistic steatohepatitis caused by moderate obesity and alcohol.
Southern California Research Center for ALPD and Cirrhosis, Department of Pathology, Keck School of Medicine of the University of Southern California, USA. Electronic address: junx@usc.edu.
Jun
J
Xu
Southern California Research Center for ALPD and Cirrhosis, Department of Pathology, Keck School of Medicine of the University of Southern California, USA.
Keane K Y
KKY
Lai
Southern California Research Center for ALPD and Cirrhosis, Department of Pathology, Keck School of Medicine of the University of Southern California, USA.
Alla
A
Verlinsky
Southern California Research Center for ALPD and Cirrhosis, Department of Pathology, Keck School of Medicine of the University of Southern California, USA; Veterans Affairs Greater Los Angeles Healthcare System, Los Angeles, CA, USA.
Aurelia
A
Lugea
Southern California Research Center for ALPD and Cirrhosis, Department of Pathology, Keck School of Medicine of the University of Southern California, USA; Harbor-UCLA Medical Center, Torrance, CA, USA.
Samuel W
SW
French
Division of Cardiovascular Medicine, University of Massachusetts Medical School, Worcester, MA, USA.
Marcus P
MP
Cooper
Department of Medicine, Keck School of Medicine of the University of Southern California, USA.
Cheng
C
Ji
Southern California Research Center for ALPD and Cirrhosis, Department of Pathology, Keck School of Medicine of the University of Southern California, USA; Veterans Affairs Greater Los Angeles Healthcare System, Los Angeles, CA, USA.
Hidekazu
H
Tsukamoto
D055372:AMP-Activated Protein Kinases / Q000378:metabolism; D000255:Adenosine Triphosphate / Q000378:metabolism; D052242:Adiponectin / Q000378:metabolism; D052436:Adipose Tissue, White / Q000378:metabolism; D000410:Alanine Transaminase / Q000097:blood; D000818:Animals; D015703:Antigens, CD / Q000378:metabolism; D015214:Antigens, Differentiation, Myelomonocytic / Q000378:metabolism; D001119:Arginase / Q000235:genetics / Q000378:metabolism; D004195:Disease Models, Animal; D015536:Down-Regulation / Q000235:genetics; D000091342:Endoplasmic Reticulum Chaperone BiP; D059865:Endoplasmic Reticulum Stress / Q000187:drug effects; D000431:Ethanol / Q000494:pharmacology*; D005234:Fatty Liver / Q000209:etiology / Q000235:genetics / Q000378:metabolism* / Q000473:pathology; D015870:Gene Expression / Q000187:drug effects*; D016753:Interleukin-10 / Q000235:genetics / Q000378:metabolism; D008099:Liver / Q000378:metabolism*; D008262:Macrophage Activation / Q000187:drug effects / Q000235:genetics; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D008928:Mitochondria / Q000235:genetics* / Q000378:metabolism; D052248:Nitric Oxide Synthase Type I / Q000235:genetics / Q000378:metabolism; D009765:Obesity / Q000150:complications* / Q000235:genetics; D015398:Signal Transduction; D014409:Tumor Necrosis Factor-alpha / Q000235:genetics / Q000378:metabolism; D000097382:CD68 Molecule
D055372:AMP-Activated Protein Kinases; D000255:Adenosine Triphosphate; D052242:Adiponectin; D000410:Alanine Transaminase; D015703:Antigens, CD; D015214:Antigens, Differentiation, Myelomonocytic; D001119:Arginase; D000091342:Endoplasmic Reticulum Chaperone BiP; D000431:Ethanol; D016753:Interleukin-10; D052248:Nitric Oxide Synthase Type I; D014409:Tumor Necrosis Factor-alpha; C067980:CD68 antigen, human; D000097382:CD68 Molecule; C000717247:HSPA5 protein, human; C000717248:Hspa5 protein, mouse; C544448:Arg1 protein, mouse
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