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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

Transmethylation pathway: aberrancy in methyltransferase reactions in diet-induced NAFLD.(A) Heat map representation of substrates and methylated products of major SAM-derived transmethylation reactions (PEMT, GNMT, GAMT and PRMT) with HFHC diet for 52 weeks. (B) Levels of glycine, a substrate for GNMT, were decreased (p< 0.01) while the product sarcosine did not change between chow and HFHC group. (C) The gene expression of Gnmt, the most abundant methyltranserase in the liver, decreased significantly but only approached significance at the protein level (p = 0.06). (D) Levels of PE, the substrate for PEMT, was significantly reduced (p< 0.01) while PC trended down, resulting in a significant PC/PE ratio (p< 0.01), which suggests increase in PEMT activity There were no significant changes in the concentrations of guanidinoacetate and creatine, the substrate and product for GAMT, respectively. (E) The methylated products of PRMT activity, MMA and ADMA, were decreased significantly (p< 0.01 and p< 0.05) while the decrease in SDMA approached significance (p = 0.07). (F) The gene expression of Prmt1, mainly responsible for the methylation of MMA and ADMA, decreased (p< 0.01) but the protein levels of PRMT1 increased significantly (p< 0.05). (G) Circulating ADMA was increased toward significance (p = 0.06), suggesting increased export to the circulation. Data are represented as mean ± SEM. Legend: arginine (Arg); asymmetric dimethylarginine (ADMA); creatine (Crea); glycine (Gly); glycine N-methyltransferase (GNMT); guanidinoacetate (GAA); guanidinoacetate methyltransferase (GAMT); homocysteine (Hcy); monomethylarginine (MMA); phosphatidylcholine (PC); phosphatidylethanolamine (PE); phosphatidylethanolamine methyltransferase (PEMT); protein arginine methyltransferase (PRMT); s-adenosylhomocysteine (SAH); s-adenosylmethionine (SAM); sarcosine (Sar); symmetric dimethylarginine (SDMA).
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pone.0136822.g003: Transmethylation pathway: aberrancy in methyltransferase reactions in diet-induced NAFLD.(A) Heat map representation of substrates and methylated products of major SAM-derived transmethylation reactions (PEMT, GNMT, GAMT and PRMT) with HFHC diet for 52 weeks. (B) Levels of glycine, a substrate for GNMT, were decreased (p< 0.01) while the product sarcosine did not change between chow and HFHC group. (C) The gene expression of Gnmt, the most abundant methyltranserase in the liver, decreased significantly but only approached significance at the protein level (p = 0.06). (D) Levels of PE, the substrate for PEMT, was significantly reduced (p< 0.01) while PC trended down, resulting in a significant PC/PE ratio (p< 0.01), which suggests increase in PEMT activity There were no significant changes in the concentrations of guanidinoacetate and creatine, the substrate and product for GAMT, respectively. (E) The methylated products of PRMT activity, MMA and ADMA, were decreased significantly (p< 0.01 and p< 0.05) while the decrease in SDMA approached significance (p = 0.07). (F) The gene expression of Prmt1, mainly responsible for the methylation of MMA and ADMA, decreased (p< 0.01) but the protein levels of PRMT1 increased significantly (p< 0.05). (G) Circulating ADMA was increased toward significance (p = 0.06), suggesting increased export to the circulation. Data are represented as mean ± SEM. Legend: arginine (Arg); asymmetric dimethylarginine (ADMA); creatine (Crea); glycine (Gly); glycine N-methyltransferase (GNMT); guanidinoacetate (GAA); guanidinoacetate methyltransferase (GAMT); homocysteine (Hcy); monomethylarginine (MMA); phosphatidylcholine (PC); phosphatidylethanolamine (PE); phosphatidylethanolamine methyltransferase (PEMT); protein arginine methyltransferase (PRMT); s-adenosylhomocysteine (SAH); s-adenosylmethionine (SAM); sarcosine (Sar); symmetric dimethylarginine (SDMA).

Mentions: Substrates and methylated products of major methyltransferase reactions were quantified: glycine and sarcosine via glycine N-methyltransferase (GNMT); phosphatidylethanolamine (PE) and phosphatidylcholine (PC) via phosphatidylethanolamine methyltransferase (PEMT); guanidinoacetate (GAA) and creatine via guanidinoacetate methyltransferase (GAMT); and arginine and monomethylarginine (MMA), symmetric dimethylarginine (SDMA) and ADMA via protein arginine methyltransferase (PRMT) (Fig 3A).


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)

Transmethylation pathway: aberrancy in methyltransferase reactions in diet-induced NAFLD.(A) Heat map representation of substrates and methylated products of major SAM-derived transmethylation reactions (PEMT, GNMT, GAMT and PRMT) with HFHC diet for 52 weeks. (B) Levels of glycine, a substrate for GNMT, were decreased (p< 0.01) while the product sarcosine did not change between chow and HFHC group. (C) The gene expression of Gnmt, the most abundant methyltranserase in the liver, decreased significantly but only approached significance at the protein level (p = 0.06). (D) Levels of PE, the substrate for PEMT, was significantly reduced (p< 0.01) while PC trended down, resulting in a significant PC/PE ratio (p< 0.01), which suggests increase in PEMT activity There were no significant changes in the concentrations of guanidinoacetate and creatine, the substrate and product for GAMT, respectively. (E) The methylated products of PRMT activity, MMA and ADMA, were decreased significantly (p< 0.01 and p< 0.05) while the decrease in SDMA approached significance (p = 0.07). (F) The gene expression of Prmt1, mainly responsible for the methylation of MMA and ADMA, decreased (p< 0.01) but the protein levels of PRMT1 increased significantly (p< 0.05). (G) Circulating ADMA was increased toward significance (p = 0.06), suggesting increased export to the circulation. Data are represented as mean ± SEM. Legend: arginine (Arg); asymmetric dimethylarginine (ADMA); creatine (Crea); glycine (Gly); glycine N-methyltransferase (GNMT); guanidinoacetate (GAA); guanidinoacetate methyltransferase (GAMT); homocysteine (Hcy); monomethylarginine (MMA); phosphatidylcholine (PC); phosphatidylethanolamine (PE); phosphatidylethanolamine methyltransferase (PEMT); protein arginine methyltransferase (PRMT); s-adenosylhomocysteine (SAH); s-adenosylmethionine (SAM); sarcosine (Sar); symmetric dimethylarginine (SDMA).
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Related In: Results  -  Collection

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Show All Figures
getmorefigures.php?uid=PMC4556375&req=5

pone.0136822.g003: Transmethylation pathway: aberrancy in methyltransferase reactions in diet-induced NAFLD.(A) Heat map representation of substrates and methylated products of major SAM-derived transmethylation reactions (PEMT, GNMT, GAMT and PRMT) with HFHC diet for 52 weeks. (B) Levels of glycine, a substrate for GNMT, were decreased (p< 0.01) while the product sarcosine did not change between chow and HFHC group. (C) The gene expression of Gnmt, the most abundant methyltranserase in the liver, decreased significantly but only approached significance at the protein level (p = 0.06). (D) Levels of PE, the substrate for PEMT, was significantly reduced (p< 0.01) while PC trended down, resulting in a significant PC/PE ratio (p< 0.01), which suggests increase in PEMT activity There were no significant changes in the concentrations of guanidinoacetate and creatine, the substrate and product for GAMT, respectively. (E) The methylated products of PRMT activity, MMA and ADMA, were decreased significantly (p< 0.01 and p< 0.05) while the decrease in SDMA approached significance (p = 0.07). (F) The gene expression of Prmt1, mainly responsible for the methylation of MMA and ADMA, decreased (p< 0.01) but the protein levels of PRMT1 increased significantly (p< 0.05). (G) Circulating ADMA was increased toward significance (p = 0.06), suggesting increased export to the circulation. Data are represented as mean ± SEM. Legend: arginine (Arg); asymmetric dimethylarginine (ADMA); creatine (Crea); glycine (Gly); glycine N-methyltransferase (GNMT); guanidinoacetate (GAA); guanidinoacetate methyltransferase (GAMT); homocysteine (Hcy); monomethylarginine (MMA); phosphatidylcholine (PC); phosphatidylethanolamine (PE); phosphatidylethanolamine methyltransferase (PEMT); protein arginine methyltransferase (PRMT); s-adenosylhomocysteine (SAH); s-adenosylmethionine (SAM); sarcosine (Sar); symmetric dimethylarginine (SDMA).
Mentions: Substrates and methylated products of major methyltransferase reactions were quantified: glycine and sarcosine via glycine N-methyltransferase (GNMT); phosphatidylethanolamine (PE) and phosphatidylcholine (PC) via phosphatidylethanolamine methyltransferase (PEMT); guanidinoacetate (GAA) and creatine via guanidinoacetate methyltransferase (GAMT); and arginine and monomethylarginine (MMA), symmetric dimethylarginine (SDMA) and ADMA via protein arginine methyltransferase (PRMT) (Fig 3A).

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