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Dysregulated Hepatic Methionine Metabolism Drives Homocysteine Elevation in Diet-Induced Nonalcoholic Fatty Liver Disease.

Pacana T, Cazanave S, Verdianelli A, Patel V, Min HK, Mirshahi F, Quinlivan E, Sanyal AJ - PLoS ONE (2015)

Bottom Line: SAH hydrolase protein levels decreased significantly (p <0.01).The protein levels of protein arginine methytransferase 1 (PRMT1) increased significantly, but its products, monomethylarginine (MMA) and asymmetric dimethylarginine (ADMA), decreased significantly.Although gene expression of the DNA methyltransferase Dnmt3a decreased, the global DNA methylation was unaltered.

View Article: PubMed Central - PubMed

Affiliation: Div. of Gastroenterology, Hepatology and Nutrition, Dept. of Internal Medicine, Virginia Commonwealth University School of Medicine, Richmond, VA, 23298, United States of America.

ABSTRACT
Methionine metabolism plays a central role in methylation reactions, production of glutathione and methylarginines, and modulating homocysteine levels. The mechanisms by which these are affected in NAFLD are not fully understood. The aim is to perform a metabolomic, molecular and epigenetic analyses of hepatic methionine metabolism in diet-induced NAFLD. Female 129S1/SvlmJ;C57Bl/6J mice were fed a chow (n = 6) or high-fat high-cholesterol (HFHC) diet (n = 8) for 52 weeks. Metabolomic study, enzymatic expression and DNA methylation analyses were performed. HFHC diet led to weight gain, marked steatosis and extensive fibrosis. In the methionine cycle, hepatic methionine was depleted (30%, p< 0.01) while s-adenosylmethionine (SAM)/methionine ratio (p< 0.05), s-adenosylhomocysteine (SAH) (35%, p< 0.01) and homocysteine (25%, p< 0.01) were increased significantly. SAH hydrolase protein levels decreased significantly (p <0.01). Serine, a substrate for both homocysteine remethylation and transsulfuration, was depleted (45%, p< 0.01). In the transsulfuration pathway, cystathionine and cysteine trended upward while glutathione decreased significantly (p< 0.05). In the transmethylation pathway, levels of glycine N-methyltransferase (GNMT), the most abundant methyltransferase in the liver, decreased. The phosphatidylcholine (PC)/ phosphatidylethanolamine (PE) ratio increased significantly (p< 0.01), indicative of increased phosphatidylethanolamine methyltransferase (PEMT) activity. The protein levels of protein arginine methytransferase 1 (PRMT1) increased significantly, but its products, monomethylarginine (MMA) and asymmetric dimethylarginine (ADMA), decreased significantly. Circulating ADMA increased and approached significance (p< 0.06). Protein expression of methionine adenosyltransferase 1A, cystathionine β-synthase, γ-glutamylcysteine synthetase, betaine-homocysteine methyltransferase, and methionine synthase remained unchanged. Although gene expression of the DNA methyltransferase Dnmt3a decreased, the global DNA methylation was unaltered. Among individual genes, only HMG-CoA reductase (Hmgcr) was hypermethylated, and no methylation changes were observed in fatty acid synthase (Fasn), nuclear factor of kappa light polypeptide gene enhancer in B-cells 1 (Nfκb1), c-Jun, B-cell lymphoma 2 (Bcl-2) and Caspase 3. NAFLD was associated with hepatic methionine deficiency and homocysteine elevation, resulting mainly from impaired homocysteine remethylation, and aberrancy in methyltransferase reactions. Despite increased PRMT1 expression, hepatic ADMA was depleted while circulating ADMA was increased, suggesting increased export to circulation.

No MeSH data available.


Related in: MedlinePlus

Stable global DNA methylation and hydroxymethylation and HMG-CoA reductase DNA hypermethylation in diet-induced NAFLD.(A-B) Although the gene expression for Dnmt1 and Dnmt3a tended to decrease and decreased, respectively, the percent methyldeoxycytidine did not change between chow and HFHC group. (C) The relative 5hmdC concentrations also did not change. (D) Among the individual genes involved in the pathogenesis of NAFLD, Hmgcr was hypermethylated (p< 0.01) but there were no methylation changes for Fasn, Nfκb1, c-Jun, Bcl-2, and Caspase 3in HFHC group. Data are represented as mean ± SEM. Legend: B-cell lymphoma 2 (Bcl-2); DNA methyltransferase 1 and 3a (Dnmt 1 and Dnmt3a); fatty acid synthase (Fasn); 5-hydroxymethyl-2’-deoxycytidine (5hmdC); 3-hydroxy-3-methylglutaryl-coenzyme A reductase (HMG-CoA reductase, Hmgcr); nuclear factor of kappa light polypeptide gene enhancer in B-cells 1 (Nfkb1).
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pone.0136822.g004: Stable global DNA methylation and hydroxymethylation and HMG-CoA reductase DNA hypermethylation in diet-induced NAFLD.(A-B) Although the gene expression for Dnmt1 and Dnmt3a tended to decrease and decreased, respectively, the percent methyldeoxycytidine did not change between chow and HFHC group. (C) The relative 5hmdC concentrations also did not change. (D) Among the individual genes involved in the pathogenesis of NAFLD, Hmgcr was hypermethylated (p< 0.01) but there were no methylation changes for Fasn, Nfκb1, c-Jun, Bcl-2, and Caspase 3in HFHC group. Data are represented as mean ± SEM. Legend: B-cell lymphoma 2 (Bcl-2); DNA methyltransferase 1 and 3a (Dnmt 1 and Dnmt3a); fatty acid synthase (Fasn); 5-hydroxymethyl-2’-deoxycytidine (5hmdC); 3-hydroxy-3-methylglutaryl-coenzyme A reductase (HMG-CoA reductase, Hmgcr); nuclear factor of kappa light polypeptide gene enhancer in B-cells 1 (Nfkb1).

Mentions: The methyl groups of SAM are also used by DNA methyltransferases to methylate DNA that can lead to epigenetic modifications. The status of global DNA methylation and hydroxymethylation was determined in both groups of mice. Although the mRNA expression of Dnmt1 and Dnmt3a, respectively, tended to decrease or decreased significantly (Fig 4A), there were no differences in percent 5-methyldeoxycytidine between the chow and HFHC group (Fig 4B). No differences in relative 5-hydroxymethyl-2'-deoxycytidine (5hmdC) concentrations was also observed (Fig 4C). We also investigated the methylation status of individual genes, which play important roles in the pathogenesis of human NAFLD, at promoter CpG islands for lipogenic (HMG-CoA reductase, HMGCR; and fatty acid synthase, FASN), inflammatory (NFkB1and c-Jun), and apoptosis (Bcl-2 and Caspase 3) targets. There was a significant increase in Hmgcr methylation in HFHC group (p<0.01), whereas no methylation changes for Fasn, Nfκb1, c-Jun, Bcl-2, and Caspase 3 were observed (Fig 4D).


Dysregulated Hepatic Methionine Metabolism Drives Homocysteine Elevation in Diet-Induced Nonalcoholic Fatty Liver Disease.

Pacana T, Cazanave S, Verdianelli A, Patel V, Min HK, Mirshahi F, Quinlivan E, Sanyal AJ - PLoS ONE (2015)

Stable global DNA methylation and hydroxymethylation and HMG-CoA reductase DNA hypermethylation in diet-induced NAFLD.(A-B) Although the gene expression for Dnmt1 and Dnmt3a tended to decrease and decreased, respectively, the percent methyldeoxycytidine did not change between chow and HFHC group. (C) The relative 5hmdC concentrations also did not change. (D) Among the individual genes involved in the pathogenesis of NAFLD, Hmgcr was hypermethylated (p< 0.01) but there were no methylation changes for Fasn, Nfκb1, c-Jun, Bcl-2, and Caspase 3in HFHC group. Data are represented as mean ± SEM. Legend: B-cell lymphoma 2 (Bcl-2); DNA methyltransferase 1 and 3a (Dnmt 1 and Dnmt3a); fatty acid synthase (Fasn); 5-hydroxymethyl-2’-deoxycytidine (5hmdC); 3-hydroxy-3-methylglutaryl-coenzyme A reductase (HMG-CoA reductase, Hmgcr); nuclear factor of kappa light polypeptide gene enhancer in B-cells 1 (Nfkb1).
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Related In: Results  -  Collection

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getmorefigures.php?uid=PMC4556375&req=5

pone.0136822.g004: Stable global DNA methylation and hydroxymethylation and HMG-CoA reductase DNA hypermethylation in diet-induced NAFLD.(A-B) Although the gene expression for Dnmt1 and Dnmt3a tended to decrease and decreased, respectively, the percent methyldeoxycytidine did not change between chow and HFHC group. (C) The relative 5hmdC concentrations also did not change. (D) Among the individual genes involved in the pathogenesis of NAFLD, Hmgcr was hypermethylated (p< 0.01) but there were no methylation changes for Fasn, Nfκb1, c-Jun, Bcl-2, and Caspase 3in HFHC group. Data are represented as mean ± SEM. Legend: B-cell lymphoma 2 (Bcl-2); DNA methyltransferase 1 and 3a (Dnmt 1 and Dnmt3a); fatty acid synthase (Fasn); 5-hydroxymethyl-2’-deoxycytidine (5hmdC); 3-hydroxy-3-methylglutaryl-coenzyme A reductase (HMG-CoA reductase, Hmgcr); nuclear factor of kappa light polypeptide gene enhancer in B-cells 1 (Nfkb1).
Mentions: The methyl groups of SAM are also used by DNA methyltransferases to methylate DNA that can lead to epigenetic modifications. The status of global DNA methylation and hydroxymethylation was determined in both groups of mice. Although the mRNA expression of Dnmt1 and Dnmt3a, respectively, tended to decrease or decreased significantly (Fig 4A), there were no differences in percent 5-methyldeoxycytidine between the chow and HFHC group (Fig 4B). No differences in relative 5-hydroxymethyl-2'-deoxycytidine (5hmdC) concentrations was also observed (Fig 4C). We also investigated the methylation status of individual genes, which play important roles in the pathogenesis of human NAFLD, at promoter CpG islands for lipogenic (HMG-CoA reductase, HMGCR; and fatty acid synthase, FASN), inflammatory (NFkB1and c-Jun), and apoptosis (Bcl-2 and Caspase 3) targets. There was a significant increase in Hmgcr methylation in HFHC group (p<0.01), whereas no methylation changes for Fasn, Nfκb1, c-Jun, Bcl-2, and Caspase 3 were observed (Fig 4D).

Bottom Line: SAH hydrolase protein levels decreased significantly (p <0.01).The protein levels of protein arginine methytransferase 1 (PRMT1) increased significantly, but its products, monomethylarginine (MMA) and asymmetric dimethylarginine (ADMA), decreased significantly.Although gene expression of the DNA methyltransferase Dnmt3a decreased, the global DNA methylation was unaltered.

View Article: PubMed Central - PubMed

Affiliation: Div. of Gastroenterology, Hepatology and Nutrition, Dept. of Internal Medicine, Virginia Commonwealth University School of Medicine, Richmond, VA, 23298, United States of America.

ABSTRACT
Methionine metabolism plays a central role in methylation reactions, production of glutathione and methylarginines, and modulating homocysteine levels. The mechanisms by which these are affected in NAFLD are not fully understood. The aim is to perform a metabolomic, molecular and epigenetic analyses of hepatic methionine metabolism in diet-induced NAFLD. Female 129S1/SvlmJ;C57Bl/6J mice were fed a chow (n = 6) or high-fat high-cholesterol (HFHC) diet (n = 8) for 52 weeks. Metabolomic study, enzymatic expression and DNA methylation analyses were performed. HFHC diet led to weight gain, marked steatosis and extensive fibrosis. In the methionine cycle, hepatic methionine was depleted (30%, p< 0.01) while s-adenosylmethionine (SAM)/methionine ratio (p< 0.05), s-adenosylhomocysteine (SAH) (35%, p< 0.01) and homocysteine (25%, p< 0.01) were increased significantly. SAH hydrolase protein levels decreased significantly (p <0.01). Serine, a substrate for both homocysteine remethylation and transsulfuration, was depleted (45%, p< 0.01). In the transsulfuration pathway, cystathionine and cysteine trended upward while glutathione decreased significantly (p< 0.05). In the transmethylation pathway, levels of glycine N-methyltransferase (GNMT), the most abundant methyltransferase in the liver, decreased. The phosphatidylcholine (PC)/ phosphatidylethanolamine (PE) ratio increased significantly (p< 0.01), indicative of increased phosphatidylethanolamine methyltransferase (PEMT) activity. The protein levels of protein arginine methytransferase 1 (PRMT1) increased significantly, but its products, monomethylarginine (MMA) and asymmetric dimethylarginine (ADMA), decreased significantly. Circulating ADMA increased and approached significance (p< 0.06). Protein expression of methionine adenosyltransferase 1A, cystathionine β-synthase, γ-glutamylcysteine synthetase, betaine-homocysteine methyltransferase, and methionine synthase remained unchanged. Although gene expression of the DNA methyltransferase Dnmt3a decreased, the global DNA methylation was unaltered. Among individual genes, only HMG-CoA reductase (Hmgcr) was hypermethylated, and no methylation changes were observed in fatty acid synthase (Fasn), nuclear factor of kappa light polypeptide gene enhancer in B-cells 1 (Nfκb1), c-Jun, B-cell lymphoma 2 (Bcl-2) and Caspase 3. NAFLD was associated with hepatic methionine deficiency and homocysteine elevation, resulting mainly from impaired homocysteine remethylation, and aberrancy in methyltransferase reactions. Despite increased PRMT1 expression, hepatic ADMA was depleted while circulating ADMA was increased, suggesting increased export to circulation.

No MeSH data available.


Related in: MedlinePlus