Background
Chronic alcohol abuse, a major risk factor for such diseases as hepatitis and cirrhosis, impairs hepatic alcohol dehydrogenase (ADH, key ethanol metabolizing enzyme). Therefore, differentially altered hepatic and plasma proteomes were identified in chronic ethanol feeding model of hepatic ADH-deficient (ADH−) deer mice to understand the metabolic basis of alcoholic liver disease (ALD).
Methods
ADH− deer mice were fed 3.5g% ethanol via Lieber-DeCarli liquid diet daily for three months, and histology of the liver assessed. Liver and plasma proteins were separated by 2-dimensional gel electrophoresis. The proteins differentially expressed were identified by MALDI-TOF/TOF mass spectrometry (MS).
Results
Histology of the liver showed panlobular steatosis and infiltration of T-lymphocytes. Using the criteria of ≥1.5 for fold change (p value ≤0.05) with expectation value (E ≤10−3) and protein score (≥64), eighteen proteins in the livers and five in the plasma of ethanol-fed mice were differentially expressed and identified. Prolyl 4-hydroxylase, cytochrome b-5, endo A cytokeratin, ATP synthase, heat shock 70kD proteins, enoyl CoA hydratase, stress-70 protein, peroxiredoxin 1 and ornithine carbamoyl-transferase were up regulated in the livers. However, carbonic anhydrase 3, mitochondrial ATP synthase, aldolase 2, actin γ, laminin receptor and carbamoyl-phosphate synthase were down regulated. Contrary to the increased expression of creatine kinase m-type, a decreased expression of serine protease inhibitor A3A precursor, sulfated glycoprotein-2 (clusterin) and apolipoprotein E isoforms were found in the plasma of ethanol group.
Conclusions
Chronic ethanol feeding in ADH− deer mice causes steatosis and infiltration of T-lymphocytes in the livers along with increased expression of proteins involved in ER stress, fibrosis, fatty acid β oxidation and biogenesis, and decreased expression of proteins involved in ATP synthesis, carbohydrate metabolism, in cell regulation and architecture. Reduced expression of various carrier proteins as found in the plasma of ethanol group has a biomarker potential.