Hepatic transmethylation reactions in micropigs with alcoholic liver disease

Alcoholic liver disease is associated with abnormal hepatic methionine metabolism, including increased levels of homocysteine and S‐adenosylhomocysteine (SAH) and reduced levels of S‐adenosylmethionine (SAM) and glutathione (GSH). The concept that abnormal methionine metabolism is involved in the pathogenesis of alcoholic liver disease was strengthened by our previous findings in a micropig model where combining dietary folate deficiency with chronic ethanol feeding produced maximal changes in these metabolites together with early onset of microscopic steatohepatitis and an eightfold increase in plasma aspartate aminotransferase. The goal of the present study was to determine potential mechanisms for abnormal levels of these methionine metabolites by analyzing the transcripts and activities of transmethylation enzymes in the livers of the same micropigs. Ethanol feeding or folate deficiency, separately or in combination, decreased transcript levels of methylenetetrahydrofolate reductase (MTHFR), methionine adenosyltransferase (MAT1A), glycine‐N‐methyltransferase (GNMT) and S‐adenosylhomocysteine hydrolase (SAHH). Ethanol feeding alone reduced the activities of methionine synthase (MS) and MATIII and increased the activity of GNMT. Each diet, separately or in combination, decreased the activities of MTHFR and SAHH. In conclusion, the observed abnormal levels of methionine metabolites in this animal model of accelerated alcoholic liver injury can be ascribed to specific effects of ethanol with or without folate deficiency on the expressions and activities of hepatic enzymes that regulate transmethylation reactions. These novel effects on transmethylation reactions may be implicated in the pathogenesis of alcoholic liver disease. (HEPATOLOGY 2004;39:1303–1310.)

[1]  N. Kaplowitz,et al.  Betaine decreases hyperhomocysteinemia, endoplasmic reticulum stress, and liver injury in alcohol-fed mice. , 2003, Gastroenterology.

[2]  S. J. James,et al.  Folate deficiency disturbs hepatic methionine metabolism and promotes liver injury in the ethanol-fed micropig , 2002, Proceedings of the National Academy of Sciences of the United States of America.

[3]  R. Matthews.  Methylenetetrahydrofolate reductase: a common human polymorphism and its biochemical implications. , 2002, Chemical record.

[4]  Zhoutao Chen,et al.  Effects of common polymorphisms on the properties of recombinant human methylenetetrahydrofolate reductase , 2001, Proceedings of the National Academy of Sciences of the United States of America.

[5]  Thomas D. Schmittgen,et al.  Real-Time Quantitative PCR , 2002 .

[6]  F. Santolaria,et al.  High prevalence of hyperhomocysteinemia in chronic alcoholism: the importance of the thermolabile form of the enzyme methylenetetrahydrofolate reductase (MTHFR). , 2001, Alcohol.

[7]  J H Eckfeldt,et al.  The 1298A-->C polymorphism in methylenetetrahydrofolate reductase (MTHFR): in vitro expression and association with homocysteine. , 2001, Atherosclerosis.

[8]  Yuan-Yuan Shi,et al.  Homocysteine-induced endoplasmic reticulum stress causes dysregulation of the cholesterol and triglyceride biosynthetic pathways. , 2001, The Journal of clinical investigation.

[9]  C. Cunningham,et al.  Chronic ethanol consumption alters the glutathione/glutathione peroxidase-1 system and protein oxidation status in rat liver. , 2001, Alcoholism, clinical and experimental research.

[10]  Shelly C. Lu,et al.  Methionine adenosyltransferase 1A knockout mice are predisposed to liver injury and exhibit increased expression of genes involved in proliferation , 2001, Proceedings of the National Academy of Sciences of the United States of America.

[11]  A. Devlin,et al.  Reduced folate carrier: tissue distribution and effects of chronic ethanol intake in the micropig. , 2001, Alcoholism, clinical and experimental research.

[12]  E. Quadros,et al.  Radioenzymatic assay for reductive catalysis of N(5)N(10)-methylenetetrahydrofolate by methylenetetrahydrofolate reductase. , 2000, Journal of biochemical and biophysical methods.

[13]  I. Pogribny,et al.  Increase in Plasma Homocysteine Associated with Parallel Increases in Plasma S-Adenosylhomocysteine and Lymphocyte DNA Hypomethylation* , 2000, The Journal of Biological Chemistry.

[14]  Shelly C. Lu,et al.  Changes in methionine adenosyltransferase and S-adenosylmethionine homeostasis in alcoholic rat liver. , 2000, American journal of physiology. Gastrointestinal and liver physiology.

[15]  Shelly C. Lu,et al.  Liver‐specific methionine adenosyltransferase MAT1A gene expression is associated with a specific pattern of promoter methylation and histone acetylation: implications for MAT1A silencing during transformation , 2000, FASEB journal : official publication of the Federation of American Societies for Experimental Biology.

[16]  I. Graham.  Homocysteine in Health and Disease , 1999, Annals of Internal Medicine.

[17]  F. Corrales,et al.  Selective glutathione depletion of mitochondria by ethanol sensitizes hepatocytes to tumor necrosis factor. , 1998, Gastroenterology.

[18]  H. Osswald,et al.  Effects of ions on adenosine binding and enzyme activity of purified S-adenosylhomocysteine hydrolase from bovine kidney. , 1998, Biochemical pharmacology.

[19]  Shelly C. Lu,et al.  Changes in methionine adenosyltransferase during liver regeneration in the rat. , 1998, American journal of physiology. Gastrointestinal and liver physiology.

[20]  A. Nicolaou,et al.  The effect of ethanol and its metabolites upon methionine synthase activity in vitro. , 1998, Alcohol.

[21]  L. Boscá,et al.  Regulation of rat liver S‐adenosylmethionine synthetase during septic shock: Role of nitric oxide , 1997, Hepatology.

[22]  M. Pajares,et al.  Site-directed mutagenesis of rat liver S-adenosylmethionine synthetase. Identification of a cysteine residue critical for the oligomeric state. , 1996, The Biochemical journal.

[23]  L. Klassen,et al.  Acetaldehyde and malondialdehyde react together to generate distinct protein adducts in the liver during long‐term ethanol administration , 1996, Hepatology.

[24]  S. J. James,et al.  Ethanol feeding of micropigs alters methionine metabolism and increases hepatocellular apoptosis and proliferation , 1996, Hepatology.

[25]  L. Glória,et al.  Hyperhomocysteinemia in chronic alcoholism: correlation with folate, vitamin B-12, and vitamin B-6 status. , 1996, The American journal of clinical nutrition.

[26]  B. Ruebner,et al.  Sequential acetaldehyde production, lipid peroxidation, and fibrogenesis in micropig model of alcohol‐induced liver disease , 1995, Hepatology.

[27]  N. Kaplowitz,et al.  Feeding S‐adenosyl‐l‐methionine attenuates both ethanol‐induced depletion of mitochondrial glutathione and mitochondrial dysfunction in periportal and perivenous rat hepatocytes , 1995, Hepatology.

[28]  J. Thompson,et al.  CLUSTAL W: improving the sensitivity of progressive multiple sequence alignment through sequence weighting, position-specific gap penalties and weight matrix choice. , 1994, Nucleic acids research.

[29]  B. Ruebner,et al.  Centrilobular distribution of acetaldehyde and collagen in the ethanol‐fed micropig , 1993, Hepatology.

[30]  D. Weir,et al.  The effect of ethanol on one‐carbon metabolism: Increased methionine catabolism and lipotrope methyl‐group wastage , 1993, Hepatology.

[31]  M. Pajares,et al.  Modulation of rat liver S-adenosylmethionine synthetase activity by glutathione. , 1992, The Journal of biological chemistry.

[32]  M. Shimoda,et al.  Tetrahydrofolic acid as the principal congener of plasma folates in pigs. , 1991, The American journal of physiology.

[33]  J. Marin,et al.  Influence of backward perfusion on ursodeoxycholate-induced choleresis in isolated in situ rat liver. , 1990, Journal of hepatology.

[34]  Cho-il Kim,et al.  S‐Adenosyl‐L‐methionine attenuates alcohol‐induced liver injury in the baboon , 1990, Hepatology.

[35]  W. R. Bates,et al.  Effects of chronic ethanol and diet treatment on urinary folate excretion and development of folate deficiency in the rat. , 1989, The Journal of nutrition.

[36]  D. Tuma,et al.  Covalent binding of acetaldehyde to proteins: participation of lysine residues. , 1987, Alcoholism, clinical and experimental research.

[37]  P. Chomczyński,et al.  Single-step method of RNA isolation by acid guanidinium thiocyanate-phenol-chloroform extraction. , 1987, Analytical biochemistry.

[38]  D. Tuma,et al.  Effects of prolonged ethanol feeding on methionine metabolism in rat liver. , 1987, Biochemistry and cell biology = Biochimie et biologie cellulaire.

[39]  D. A. Jencks,et al.  Allosteric inhibition of methylenetetrahydrofolate reductase by adenosylmethionine. Effects of adenosylmethionine and NADPH on the equilibrium between active and inactive forms of the enzyme and on the kinetics of approach to equilibrium. , 1987, The Journal of biological chemistry.

[40]  R. Cook,et al.  Inhibition of glycine N-methyltransferase activity by folate derivatives: implications for regulation of methyl group metabolism. , 1985, Biochemical and biophysical research communications.

[41]  R. Matthews,et al.  Methylenetetrahydrofolate reductase. Evidence for spatially distinct subunit domains obtained by scanning transmission electron microscopy and limited proteolysis. , 1984, The Journal of biological chemistry.

[42]  R. Cook,et al.  Glycine N-methyltransferase is a folate binding protein of rat liver cytosol. , 1984, Proceedings of the National Academy of Sciences of the United States of America.

[43]  H Ogawa,et al.  Purification and properties of glycine N-methyltransferase from rat liver. , 1982, The Journal of biological chemistry.

[44]  Elaine,et al.  Nitrous oxide has multiple deleterious effects on cobalamin metabolism and causes decreases in activities of both mammalian cobalamin-dependent enzymes in rats. , 1981, The Journal of clinical investigation.

[45]  D. Marion,et al.  S-Adenosylmethionine and S-adenosylhomocystein metabolism in isolated rat liver. Effects of L-methionine, L-homocystein, and adenosine. , 1980, The Journal of biological chemistry.

[46]  B. Mannervik,et al.  Purification and characterization of the flavoenzyme glutathione reductase from rat liver. , 1975, The Journal of biological chemistry.

[47]  J. Finkelstein,et al.  Ethanol-induced changes in methionine metabolism in rat liver. , 1974, Biochemical and biophysical research communications.

[48]  E. Eichner,et al.  Effect of alcohol on serum folate level. , 1973, The Journal of clinical investigation.

[49]  E. Mezey,et al.  Decreased jejunal uptake of labeled folic acid ( 3 H-PGA) in alcoholic patients: roles of alcohol and nutrition. , 1971, The New England journal of medicine.