Phosphatidylethanolamine N-methyltransferase Research Articles

Importance of polymorphic variants of phosphatidylethanolamine N-methyltransferase (PEMT) gene in the etiology of intrauterine fetal death in the Polish population

ObjectivesIntrauterine fetal death (IUFD) is a multifactorial disorder and one of the most severe obstetrical complications. Our primary aim was to study the possible associations between polymorphic variants of the PEMT gene and IUFD in the Polish population. Study designThe case-control study involved 76 mothers with IUFD occurrence and 215 mothers of healthy children. Genetic analysis of the four single nucleotide polymorphisms in the PEMT gene (rs4646406, rs4244593, rs897453 and rs12325817) was performed with the PCR/RFLP method. ResultsThree oef the analyzed PEMT polymorphisms (rs4646406, rs4244593, and rs8974) were significantly associated with IUFD in the Polish population. Among them, PEMT variant rs4244593 was associated with increased risk of IUFD in three genetic inheritance models. Results were statistically significant even after applying Bonferroni correction for multiple comparisons (p < 0.0125). The distribution of all haplotypes except TAGC was not different between cases and controls, however, after applying permutation test, none of the haplotypes showed a relation with IUFD. ConclusionsThe present findings indicate that PEMT polymorphisms may be associated with the susceptibility to IUFD in the Polish population.

Vitamin E alleviates non-alcoholic fatty liver disease in phosphatidylethanolamine N-methyltransferase deficient mice

Phosphatidylethanolamine N-methyltransferase (PEMT) converts phosphatidylethanolamine (PE) to phosphatidylcholine (PC), mainly in the liver. Pemt−/− mice are protected from high-fat diet (HFD)-induced obesity and insulin resistance, but develop severe non-alcoholic fatty liver disease (NAFLD) when fed a HFD, mostly due to impaired VLDL secretion. Oxidative stress is thought to be an essential factor in the progression from simple steatosis to steatohepatitis. Vitamin E is an antioxidant that has been clinically used to improve NAFLD pathology. Our aim was to determine whether supplementation of the diet with vitamin E could attenuate HFD-induced hepatic steatosis and its progression to NASH in Pemt−/− mice. Treatment with vitamin E (0.5 g/kg) for 3 weeks improved VLDL-TG secretion and normalized cholesterol metabolism, but failed to reduce hepatic TG content. Moreover, vitamin E treatment was able to reduce hepatic oxidative stress, inflammation and fibrosis. We also observed abnormal ceramide metabolism in Pemt−/− mice fed a HFD, with elevation of ceramides and other sphingolipids and higher expression of mRNAs for acid ceramidase (Asah1) and ceramide kinase (Cerk). Interestingly, vitamin E supplementation restored Asah1 and Cerk mRNA and sphingolipid levels. Together this study shows that vitamin E treatment efficiently prevented the progression from simple steatosis to steatohepatitis in mice lacking PEMT.

Hepatic Expression of PEMT, but Not Dietary Choline Supplementation, Reverses the Protection against Atherosclerosis in Pemt−/−/Ldlr−/− Mice

Phosphatidylethanolamine N-methyltransferase (PEMT) converts phosphatidylethanolamine to phosphatidylcholine. Pemt-/-/low density lipoprotein receptor (Ldlr)-/- mice have significantly reduced plasma lipids and are protected against atherosclerosis. Recent studies have shown that choline can be metabolized by the gut flora into trimethylamine-N-oxide (TMAO), which is an emerging risk factor for atherosclerosis. The objective of this study was to determine whether ectopic hepatic PEMT expression or choline supplementation would promote atherosclerosis in Pemt-/-/Ldlr-/- mice. Male 8- to 10-wk-old Pemt+/+/Ldlr-/- (SKO) and Pemt-/-/Ldlr-/- (DKO) mice were injected with an adeno-associated virus (AAV) expressing green fluorescent protein (GFP) or human PEMT and fed a Western diet (40% of calories from fat, 0.5% cholesterol) for 8 wk. In a separate experiment, 8- to 10-wk-old SKO and half of the DKO male mice were fed a Western diet with normal (3 g/kg) choline for 12 wk. The remaining DKO mice [choline-supplemented (CS) DKO] were fed a CS Western diet (10 g choline/kg). Plasma lipid concentrations, choline metabolites, and aortic atherosclerosis were measured. Plasma cholesterol, plasma TMAO, and aortic atherosclerosis were reduced by 60%, 40%, and 80%, respectively, in DKO mice compared with SKO mice. AAV-PEMT administration increased plasma cholesterol and TMAO by 30% and 40%, respectively, in DKO mice compared with AAV-GFP-treated DKO mice. Furthermore, AAV-PEMT-injected DKO mice developed atherosclerotic lesions similar to SKO mice. In the second study, there was no difference in atherosclerosis or plasma cholesterol between DKO and CS-DKO mice. However, plasma TMAO concentrations were increased 2.5-fold in CS-DKO mice compared with DKO mice. Reintroducing hepatic PEMT reversed the atheroprotective phenotype of DKO mice. Choline supplementation did not increase atherosclerosis or plasma cholesterol in DKO mice. Our data suggest that plasma TMAO does not induce atherosclerosis when plasma cholesterol is low. Furthermore, this is the first report to our knowledge that suggests that de novo choline synthesis alters TMAO status.

P-89 - A potential novel pathway to regulate cellular concentrations of the redox-active lipid coenzyme Q

Coenzyme Q (CoQ) is an essential redox-active lipid, and its deficiency is implicated in numerous diseases. However, it is largely unknown what regulates CoQ content. To investigate cellular CoQ regulation, we performed a genome-wide screen (~5,000 S. cerevisiae single gene mutants) to isolate genes critical for CoQ homeostasis, and measured CoQ content in each mutant using HPLC-EC detection. Some 30 knockout mutants were identified with significantly higher CoQ content compared to WT including the cho2 mutant. CHO2 encodes a phosphatidylethanolamine (PE) methyltransferase that catalyzes the conversion of PE to phosphatidylcholine (PC). Homologs of CHO2 are found in mammals (PEMT) indicating there may be role for this gene in CoQ regulation in other species. The cho2 mutant contained concentrations of CoQ five times greater than WT, and a significantly increased rate of CoQ synthesis. To investigate if Pemt–/– mice also display elevated CoQ content akin to yeast cho2 mutants, we analyzed the CoQ content in liver and adipose tissue from Pemt+/+ and Pemt–/– mice. In these tissues, CoQ content was approximately double in Pemt–/– compared to Pemt+/+. Taken together, our data suggests a novel role for phosphatidylethanolamine methyltransferases in CoQ content regulation.

PEMT, Δ6 desaturase, and palmitoyldocosahexaenoyl phosphatidylcholine are increased in rats during pregnancy

DHA is important for fetal neurodevelopment. During pregnancy, maternal plasma DHA increases, but the mechanism is not fully understood. Using rats fed a fixed-formula diet (DHA as 0.07% total energy), plasma and liver were collected for fatty acid profiling before pregnancy, at 15 and 20 days of pregnancy, and 7 days postpartum. Phosphatidylethanolamine methyltransferase (PEMT) and enzymes involved in PUFA synthesis were examined in liver. Ad hoc transcriptomic and lipidomic analyses were also performed. With pregnancy, DHA increased in liver and plasma lipids, with a large increase in plasma DHA between day 15 and day 20 that was mainly attributed to an increase in 16:0/DHA phosphatidylcholine (PC) in liver (2.6-fold) and plasma (3.9-fold). Increased protein levels of Δ6 desaturase (FADS2) and PEMT at day 20 and increased Pemt expression and PEMT activity at day 15 suggest that during pregnancy, both DHA synthesis and 16:0/DHA PC synthesis are upregulated. Transcriptomic analysis revealed minor changes in the expression of genes related to phospholipid synthesis, but little insight on DHA metabolism. Hepatic PEMT appears to be the mechanism for increased plasma 16:0/DHA PC, which is supported by increased DHA biosynthesis based on increased FADS2 protein levels.

Abnormal liver phosphatidylcholine synthesis revealed in patients with acute respiratory distress syndrome

Acute respiratory distress syndrome (ARDS) is associated with a severe pro-inflammatory response; although decreased plasma cholesterol concentration has been linked to systemic inflammation, any association of phospholipid metabolic pathways with ARDS has not been characterized. Plasma phosphatidylcholine (PC), the major phospholipid of circulating lipoproteins, is synthesized in human liver by two biologically diverse pathways: the cytidine diphosphocholine (CDP):choline and phosphatidylethanolamine N-methyltransferase (PEMT) pathways. Here, we used ESI-MS/MS both to characterize plasma PC compositions and to quantify metabolic fluxes of both pathways using stable isotopes in patients with severe ARDS and in healthy controls. Direct incorporation of methyl-D9-choline estimated CDP:choline pathway flux, while PEMT flux was determined from incorporations of one and two methyl-D3 groups derived from methyl-D9-choline. The results of MS/MS analysis showed significant alterations in plasma PC composition in patients with ARDS versus healthy controls. In particular, the increased overall methyl-D9-PC enrichment and, most importantly, the much lower methyl-D3-PC and methyl-D6-PC enrichments suggest increased flux through the CDP:choline pathway and reduced flux through the PEMT pathway in ARDS. To our knowledge, this study is the first to demonstrate significant plasma PC molecular compositional changes combined with associated alterations in the dynamics of PC synthetic pathways in patients with ARDS.

Evolution of the Phosphatidylcholine Biosynthesis Pathways in Green Algae: Combinatorial Diversity of Methyltransferases.

Phosphatidylcholine (PC) is one of the most common phospholipids in eukaryotes, although some green algae such as Chlamydomonas reinhardtii are known to lack PC. Recently, we detected PC in four species in the genus Chlamydomonas: C. applanata NIES-2202, C. asymmetrica NIES-2207, C. debaryana NIES-2212, and C. sphaeroides NIES-2242. To reveal the PC biosynthesis pathways in green algae and the evolutionary scenario involved in their diversity, we analyzed the PC biosynthesis genes in these four algae using draft genome sequences. Homology searches suggested that PC in these species is synthesized by phosphoethanolamine-N-methyltransferase (PEAMT) and/or phosphatidylethanolamine-N-methyltransferase (PEMT), both of which are absent in C. reinhardtii. Recombinant PEAMTs from these algae showed methyltransferase activity for phosphoethanolamine but not for monomethyl phosphoethanolamine in vitro, in contrast to land plant PEAMT, which catalyzes the three methylations from phosphoethanolamine to phosphocholine. This suggested an involvement of other methyltransferases in PC biosynthesis. Here, we characterized the putative phospholipid-N-methyltransferase (PLMT) genes of these species by genetic and phylogenetic analysis. Complementation assays using a PC biosynthesis-deficient yeast suggested that the PLMTs of these algae can synthesize PC from phosphatidylethanolamine. These results indicated that the PC biosynthesis pathways in green algae differ from those of land plants, although the enzymes involved are homologous. Phylogenetic analysis suggested that the PEAMTs and PLMTs in these algae were inherited from the common ancestor of green algae. The absence of PC biosynthesis in many Chlamydomonas species is likely a result of parallel losses of PEAMT and PLMT in this genus.

Diverse effect of phosphatidylcholine biosynthetic genes on phospholipid homeostasis, cell autophagy and fungal developments in Metarhizium robertsii.

Phosphatidylcholine (PC) plays an important role in maintaining membrane integrity and functionality. In this study, two key genes (Mrpct and Mrpem) putatively involved in the cytidine diphosphate (CDP)-choline and phosphatidylethanolamine N-methyltransferase (PEMT) pathways for PC biosynthesis were characterized in the insect pathogenic fungus Metarhizium robertsii. The results indicated that disruption of Mrpct did not lead to any reduction of total PC content but impaired fungal virulence and increased cellular accumulation of triacylglycerol. Deletion of Mrpem reduced PC content and impaired fungal conidiation and infection structure differentiation but did not result in virulence defects. Lipidomic analysis revealed that deletion of Mrpct and Mrpem resulted in dissimilar effects on increase and decrease of PC moieties and other phospholipid species accumulations. Interestingly, we found that these two genes played opposite roles in activation of cell autophagy when the fungi were grown in a nutrient-rich medium. The connection between PC metabolism and autophagy was confirmed because PC content was drastically reduced in Mratg8Δ and that the addition of PC could rescue null mutant sporulation defect. The results of this study facilitate the understanding of PC metabolism on fungal physiology.

From masochistic enzymology to mechanistic physiology and disease

The pioneering work of Eugene Kennedy in the 1950s established the choline pathway for phosphatidylcholine (PC) biosynthesis. However, the regulation of PC biosynthesis was poorly understood at that time. When I started my lab at the University of British Columbia in the 1970s, this was the focus of my research. This article provides my reflections on these studies that began with enzymology and the use of cultured mammalian cells, and progressed to utilize the techniques of molecular biology and gene-targeted mice. The research in my lab and others demonstrated that the regulated and rate-limiting step in the choline pathway for PC biosynthesis was catalyzed by CTP:phosphocholine cytidylyltransferase. This enzyme is regulated by its movement from a soluble form (largely in the nucleus) to a membrane-associated form where the enzyme becomes activated. Gene targeting in mice subsequently demonstrated that this gene is essential for development of mouse embryos. The other mammalian pathway for PC biosynthesis is catalyzed by phosphatidylethanolamine N-methyltransferase (PEMT) that converts phosphatidylethanolamine to PC. Understanding of the regulation and function of the integral membrane protein PEMT was improved when the enzyme was purified (a masochistic endeavor) in 1987, leading to the cloning of the Pemt cDNA. Generation of knock-out mice that lacked PEMT showed that they were protected from atherosclerosis, diet-induced obesity, and insulin resistance. The protection from atherosclerosis appears to be due to decreased secretion of lipoproteins from the liver. We continue to investigate the mechanism(s) by which Pemt-/- mice are protected from weight gain and insulin resistance.

Liquid chromatography mass spectrometry-based profiling of phosphatidylcholine and phosphatidylethanolamine in the plasma and liver of acetaminophen-induced liver injured mice

BackgroundAcetaminophen (APAP) overdose is one of the most common causes of acute liver failure in many countries. The aim of the study was to describe the profiling of phosphatidylcholine (PC) and phosphatidylethanolamine (PE) in the plasma and liver of Acetaminophen -induced liver injured mice.MethodsA time course study was carried out using C57BL/6 mice after intraperitoneal administration of 300 mg/kg Acetaminophen 1 h, 3 h, 6 h, 12 h and 24 h. A high-throughput liquid chromatography mass spectrometry (LC-MS) lipidomic method was utilized to detect phosphatidylcholine and phosphatidylethanolamine species in the plasma and liver. The expressions of phosphatidylcholine and phosphatidylethanolamine metabolism related genes in liver were detected by quantitative Reverse transcription polymerase chain reaction (qRT-PCR) and Western-blot.ResultsFollowing Acetaminophen treatment, the content of many PC and PE species in plasma increased from 1 h time point, peaked at 3 h or 6 h, and tended to return to baseline at 24 h time point. The relative contents of almost all PC species in liver decreased from 1 h, appeared to be lowest at 6 h, and then return to normality at 24 h, which might be partly explained by the suppression of phospholipases mRNA expressions and the induction of choline kinase (Chka) expression. Inconsistent with PC profile, the relative contents of many PE species in liver increased upon Acetaminophen treatment, which might be caused by the down-regulation of phosphatidylethanolamine N-methyltransferase (Pemt).ConclusionsAcetaminophen overdose induced dramatic change of many PC and PE species in plasma and liver, which might be caused by damaging hepatocytes and interfering the phospholipid metabolism in Acetaminophen -injured liver.

Insights into the phosphatidylcholine and phosphatidylethanolamine biosynthetic pathways in Leishmania parasites and characterization of a choline kinase from Leishmania infantum.

The protozoan parasite Leishmania infantum is a causative agent of the disease visceral leishmaniasis, which can be fatal if not properly treated. Phosphatidylcholine (PC) and phosphatidylethanolamine (PE) biosynthesis pathways are attractive targets for new antileishmanial compounds since these Leishmania cell membrane phospholipids are important for parasite morphology and physiology. In this work we observed Leishmania synthesize PC and PE from extracellular choline and ethanolamine, respectively, suggesting the presence of CDP-choline and CDP-ethanolamine pathways. In addition, Leishmania converted PE to PC, indicating the parasite possesses phosphatidylethanolamine N-methyltransferase (PEMT) activity. The first step in the biosynthesis of PC or PE requires the phosphorylation of choline or ethanolamine by a kinase. We cloned the gene encoding a putative choline/ethanolamine kinase from Leishmania infantum and expressed and purified the encoded recombinant protein. The enzyme possesses choline kinase activity with a Vmax of 3.52μmol/min/mg and an apparent Km value of 0.089mM with respect to choline. The enzyme can also phosphorylate ethanolamine in vitro, but the apparent Km for ethanolamine is 850-fold greater than for choline. In an effort to probe requirements for small molecule inhibition of Leishmania choline kinase, the recombinant enzyme was evaluated for the ability to be inhibited by novel quaternary ammonium salts. The most effective inhibitor was N-iodomethyl-N,N,-dimethyl-N-(6,6-diphenyl hex-5-en-1-yle) ammonium iodide, denoted compound C6. In the presence of 4mM compound C6, the Vmax/Km decreased to approximately 1% of the wild-type catalytic efficiency. In addition, in Leishmania cells treated with compound C6 choline transport was inhibited.

Abstract LB-095: Genome-wide methylation in colorectal cancer and obesity

Abstract Purpose: The purpose of this new ground-breaking project is to identify different methylation patterns across human genome for oncogenes and genes in the methylation pathways for cancer prevention. Background: Chronic health conditions can lead to cancer with altered epigenetics cardiovascular phenotypes including differential methylation and gene expression patterns that affect health outcomes. In addition to oncogenes, we examined genes in the methylation pathways for cancer prevention. Method: We included subjects from a family-based case-control study for CRC patients and their matched healthy family members, and obese subjects and matched lean controls (n=5 each group) by accessing publically available GEO data, using reduced representation bisulfite sequencing (RRBS). Blood specimen and data processing were completed by using standardized quality programming and analysis. The average coverage of nucleotides was 3.9% of genome. Comparative analyses were performed with a difference of &amp;gt;10% of differentially methylated regions (DMR) between various case and control samples. Results: Few genes in the inflammatory-methylation and obesity pathways such as NOS3, AHCY, MTHFD1, FGR, MiR3648, and MiR4285 had higher methylation levels in the promoter regions than that in the intron regions, as contrary to the majority of other genes. The methylation levels for DMRs of NOS3 gene was higher in the cancer group than other groups for intron region, and PEMT gene was lowest in the cancer group than in other groups in the promoter region, for inflammation and homocysteine toxicity in the cancer group. The patterns for the most validated SEPT9 oncogene was replicated for the cancer group, and extended to other chronic health and heredity conditions in this study; methylation levels in the promoter regions progressively decreased from lean control group to obese group, then to CRC family group, and finally the CRC group, indicating higher oncogene activity. The methylation levels for all mismatch repair genes that are known to cause hereditary Lynch syndrome for CRC were highest in the intron regions, with the microsatellite instability to repair gene mutations. Methylation in DMRs for MSH2 and MSH6 mismatch repair genes were higher in the cancer group than other groups. In addition, methylation rates of the DMRs in few obesity related genes such as HK3 and CAMK1 were also progressively increasing along the health continuum, highest in cancer group. NIH’s David Bioinformatics Resources were used to identify significant biological processes and pathway analyses, related to various metabolic processes. Conclusion: Our study is one of the first studies to present the altered DNA methylation profiles across gene regions in human genome for cardiovascular phenotype in health continuum leading to cancer. Further studies are needed on metabolomic studies to promote health and to prevent cancer. Citation Format: S. Pamela Shiao, Haiyan Xiao, Lixin Dong, Lufei Young. Genome-wide methylation in colorectal cancer and obesity [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr LB-095. doi:10.1158/1538-7445.AM2017-LB-095

A novel mechanism of immunity controls the onset of cinnamycin biosynthesis in Streptomyces cinnamoneus DSM 40646

Streptomyces cinnamoneus DSM 40646 produces the Class II lantibiotic cinnamycin which possesses an unusual mechanism of action, binding to the membrane lipid phosphatidylethanolamine (PE) to elicit its antimicrobial activity. A comprehensive analysis of the cinnamycin biosynthetic gene cluster has unveiled a novel mechanism of immunity in which the producing organism methylates its entire complement of PE prior to the onset of cinnamycin production. Deletion of the PE methyl transferase gene cinorf10, or the two-component regulatory system (cinKR) that controls its expression, leads not only to sensitivity to the closely related lantibiotic duramycin, but also abolishes cinnamycin production, presumably reflecting a fail-safe mechanism that serves to ensure that biosynthesis does not occur until immunity has been established.

Fenofibrate, but not ezetimibe, prevents fatty liver disease in mice lacking phosphatidylethanolamine N-methyltransferase

Mice lacking phosphatidylethanolamine N-methyltransferase (PEMT) are protected from high-fat diet (HFD)-induced obesity and insulin resistance. However, these mice develop severe nonalcoholic fatty liver disease (NAFLD) when fed the HFD, which is mainly due to inadequate secretion of VLDL particles. Our aim was to prevent NAFLD development in mice lacking PEMT. We treated Pemt−/− mice with either ezetimibe or fenofibrate to see if either could ameliorate liver disease in these mice. Ezetimibe treatment did not reduce fat accumulation in Pemt−/− livers, nor did it reduce markers for hepatic inflammation or fibrosis. Fenofibrate, conversely, completely prevented the development of NAFLD in Pemt−/− mice: hepatic lipid levels, as well as markers of endoplasmic reticulum stress, inflammation, and fibrosis, in fenofibrate-treated Pemt−/− mice were similar to those in Pemt+/+ mice. Importantly, Pemt−/− mice were still protected against HFD-induced obesity and insulin resistance. Moreover, fenofibrate partially reversed hepatic steatosis and fibrosis in Pemt−/− mice when treatment was initiated after NAFLD had already been established. Increasing hepatic fatty acid oxidation can compensate for the lower VLDL-triacylglycerol secretion rate and prevent/reverse fatty liver disease in mice lacking PEMT.

Genetic Variation in Choline‐Metabolizing Enzymes Alters Choline Dynamics in Women Meeting Current Dietary Recommendations

Choline Kinase-α (CHKA) rs10791957, choline dehydrogenase (CHDH) rs9001, and CHDH rs12676 are genetic risk factors for disease and choline deficiency. While these single nucleotide polymorphisms are known to alter disease risk and the minimum choline intake needed for prevention of acute muscle and liver pathologies, their underlying metabolic signatures are not well characterized and it is unknown whether metabolic differences persist under conditions of nutrient adequacy. We sought to determine if these genetic risk factors alter choline dynamics in pregnant, lactating, and non-pregnant women consuming choline intakes meeting current recommendations. Women consumed 480 or 930 mg choline/d (22% as choline-d9, a metabolic tracer) for 10–12 weeks in a controlled feeding study and stable isotope methodology was used to investigate the effect of genetic differences on choline dynamics. CHKA rs10791957 (Figure 1), CHDH rs9001 (Figure 2), and CHDH rs12676 (Figure 3) all influenced choline dynamics under the study conditions of nutrient adequacy. Variants associated with decreased risk for choline deficiency (CHKA rs10791957, CHDH rs9001) appeared to favor cytidine diphosphate (CDP)-phosphatidylcholine (PC) synthesis relative to phosphatidylethanolamine N-methyltransferase (PEMT)-PC synthesis as compared to non-variants, while the CHDH rs12676 genotype, which is associated with increased risk, favored PEMT-PC synthesis. These results are consistent with the effect of these variants on choline requirements when one considers efficiency of PC production. While each unit of choline directed to the CDP-choline pathway yields one unit of PC, choline converted to betaine (and eventually S-adenosylmethionine) has many metabolic fates besides PEMT-PC production, and three choline-derived methyl groups are needed to yield just one additional unit of PC via the PEMT pathway. Therefore, greater PEMT-PC production may constitute a drain on choline status and exacerbate disease risk during choline deficiency. Our results indicate that these SNPs have metabolic effects at choline intakes relevant to the general population and such metabolic differences may contribute to disease pathogenesis and prognosis over the long-term. In fact, decreased PEMT activity observed among CHKA rs10791957 variant women (decreased turnover of choline-derived methionine → PEMT-PC; p=0.0005) may provide a metabolic basis for the decreased risk of type 2 diabetes among CHKA rs10791957 variant individuals given that PEMT knockout mice are protected from high-fat diet induced obesity and insulin resistance. Overall, these findings highlight the need for further study to examine the effects of genetic differences in choline metabolism on chronic disease outcomes. Support or Funding InformationThis work was supported by the National Institutes of Health under award T32-DK007158 and by the USDA National Institute of Food and Agriculture, Hatch project 231646. The content is the responsibility of the authors and does not necessarily represent the views of the National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK), the National Institutes of Health or the National Institute of Food and Agriculture (NIFA) or the United States Department of Agriculture(USDA). Figure 1Open in figure viewerPowerPoint Effect of the CHKA rs10791957 variant on the metabolite flux and partitioning of dietary choline Figure 2Open in figure viewerPowerPoint Effect of the CHDH rs9001 variant on the metabolite flux and partitioning of dietary choline. Figure 3Open in figure viewerPowerPoint Effect of the CHDH rs12676 variant on the metabolite flux and partitioning of dietary choline.

Membrane Lipids Speak to Histones

In this issue of Molecular Cell, Ye etal. (2017) use a combination of genetic, metabolomic, and transcriptomic approaches to explore the potential for methionine metabolism to influence signal transduction and gene expression in budding yeast.

Cystathionine beta-synthase deficiency alters hepatic phospholipid and choline metabolism: Post-translational repression of phosphatidylethanolamine N-methyltransferase is a consequence rather than a cause of liver injury in homocystinuria.

Classical homocystinuria (HCU) due to inactivating mutation of cystathionine β-synthase (CBS) is a poorly understood life-threatening inborn error of sulfur metabolism. A previously described cbs-/- mouse model exhibits a semi-lethal phenotype due to neonatal liver failure. The transgenic HO mouse model of HCU exhibits only mild liver injury and recapitulates multiple aspects of the disease as it occurs in humans. Disruption of the methionine cycle in HCU has the potential to impact multiple aspect of phospholipid (PL) metabolism by disruption of both the Kennedy pathway and phosphatidylethanolamine N-methyltransferase (PEMT) mediated synthesis of phosphatidylcholine (PC). Comparative metabolomic analysis of HO mouse liver revealed decreased levels of choline, and choline phosphate indicating disruption of the Kennedy pathway. Alterations in the relative levels of multiple species of PL included significant increases in PL degradation products consistent with enhanced membrane PL turnover. A significant decrease in PC containing 20:4n6 which primarily formed by the methylation of phosphatidylethanolamine to PC was consistent with decreased flux through PEMT. Hepatic expression of PEMT in both the cbs-/- and HO models is post-translationally repressed with decreased levels of PEMT protein and activity that inversely-correlates with the scale of liver injury. Failure to induce further repression of PEMT in HO mice by increased homocysteine, methionine and S-adenosylhomocysteine or depletion of glutathione combined with examination of multiple homocysteine-independent models of liver injury indicated that repression of PEMT in HCU is a consequence rather than a cause of liver injury. Collectively, our data show significant alteration of a broad range of hepatic PL and choline metabolism in HCU with the potential to contribute to multiple aspects of pathogenesis in this disease.

Choline and methionine differentially alter methyl carbon metabolism in bovine neonatal hepatocytes.

Intersections in hepatic methyl group metabolism pathways highlights potential competition or compensation of methyl donors. The objective of this experiment was to examine the expression of genes related to methyl group transfer and lipid metabolism in response to increasing concentrations of choline chloride (CC) and DL-methionine (DLM) in primary neonatal hepatocytes that were or were not exposed to fatty acids (FA). Primary hepatocytes isolated from 4 neonatal Holstein calves were maintained as monolayer cultures for 24 h before treatment with CC (61, 128, 2028, and 4528 μmol/L) and DLM (16, 30, 100, 300 μmol/L), with or without a 1 mmol/L FA cocktail in a factorial arrangement. After 24 h of treatment, media was collected for quantification of reactive oxygen species (ROS) and very low-density lipoprotein (VLDL), and cell lysates were collected for quantification of gene expression. No interactions were detected between CC, DLM, or FA. Both CC and DLM decreased the expression of methionine adenosyltransferase 1A (MAT1A). Increasing CC did not alter betaine-homocysteine S-methyltranferase (BHMT) but did increase 5-methyltetrahydrofolate-homocysteine methyltransferase (MTR) and methylenetetrahydrofolate reductase (MTHFR) expression. Increasing DLM decreased expression of BHMT and MTR, but did not affect MTHFR. Expression of both phosphatidylethanolamine N-methyltransferase (PEMT) and microsomal triglyceride transfer protein (MTTP) were decreased by increasing CC and DLM, while carnitine palmitoyltransferase 1A (CPT1A) was unaffected by either. Treatment with FA decreased the expression of MAT1A, MTR, MTHFR and tended to decrease PEMT but did not affect BHMT and MTTP. Treatment with FA increased CPT1A expression. Increasing CC increased secretion of VLDL and decreased the accumulation of ROS in media. Within neonatal bovine hepatocytes, choline and methionine differentially regulate methyl carbon pathways and suggest that choline may play a critical role in donating methyl groups to support methionine regeneration. Stimulating VLDL export and decreasing ROS accumulation suggests that increasing CC is hepato-protective.

Genetic Variation in Choline-Metabolizing Enzymes Alters Choline Metabolism in Young Women Consuming Choline Intakes Meeting Current Recommendations.

Single nucleotide polymorphisms (SNPs) in choline metabolizing genes are associated with disease risk and greater susceptibility to organ dysfunction under conditions of dietary choline restriction. However, the underlying metabolic signatures of these variants are not well characterized and it is unknown whether genotypic differences persist at recommended choline intakes. Thus, we sought to determine if common genetic risk factors alter choline dynamics in pregnant, lactating, and non-pregnant women consuming choline intakes meeting and exceeding current recommendations. Women (n = 75) consumed 480 or 930 mg choline/day (22% as a metabolic tracer, choline-d9) for 10–12 weeks in a controlled feeding study. Genotyping was performed for eight variant SNPs and genetic differences in metabolic flux and partitioning of plasma choline metabolites were evaluated using stable isotope methodology. CHKA rs10791957, CHDH rs9001, CHDH rs12676, PEMT rs4646343, PEMT rs7946, FMO3 rs2266782, SLC44A1 rs7873937, and SLC44A1 rs3199966 altered the use of choline as a methyl donor; CHDH rs9001 and BHMT rs3733890 altered the partitioning of dietary choline between betaine and phosphatidylcholine synthesis via the cytidine diphosphate (CDP)-choline pathway; and CHKA rs10791957, CHDH rs12676, PEMT rs4646343, PEMT rs7946 and SLC44A1 rs7873937 altered the distribution of dietary choline between the CDP-choline and phosphatidylethanolamine N-methyltransferase (PEMT) denovo pathway. Such metabolic differences may contribute to disease pathogenesis and prognosis over the long-term.

Metabolomic study of the intervention effects of Shuihonghuazi Formula, a Traditional Chinese Medicinal formulae, on hepatocellular carcinoma (HCC) rats using performance HPLC/ESI-TOF-MS

Ethnopharmacological relevanceMetabolomics is the comprehensive assessment of endogenous metabolites of a biological system in a holistic context, and its property consists with the global view of Traditional Chinese Medicine (TCM). Shuihonghuazi Formula (SHHZF) has been used for liver cancer early treatment in clinical for more than thirty years, but its mechanism remains unclear completely. This paper was designed to explore the therapeutic effects of SHHZF on liver cancer and its metabolomic characters. Materials and methodsAll the rats were given diethylnitrosamine (DEN) at the dosage of 70mg/kg for 14 weeks. From the 7th weeks, SHHZF was given to the rats which lasted for 10 weeks. Therapeutic effects of SHHZF was compared with that of cyclophosphamide (CTX). High performance liquid-chromatography/electrospray-ionization time of flight mass spectrometer (HPLC/ESI-TOF-MS) combined with pattern recognition approaches including principal component analysis (PCA), partial least squares-discriminant analysis (PLS-DA), was integrated to approximate the comprehensive metabolic signature and discover differentiating metabolites by Agilent MPP 12.1. The changes in metabolic profiling in plasma were restored to their baseline values after SHHZF treatment according to the PLS-DA score plots. ResultsThe results indicated that 23 ions as “differentiating metabolites”. The alterations in those metabolites were associated with perturbations in fatty acid and bile acid metabolism, in response to liver cancer through immune and nervous system. And SHHZF could increase the uptake and utilization of linoleic acid and oleic acid, increase arachidonic acid-like substance content and enhance organism immunity of liver cancer rats. And it also could increase the translation from phosphatidylethanolamine (PE) to phosphatidylcholine (PC), linoleic acid metabolism and inhibits abnormal metabolism of bile acid. ConclusionsThe mechanism of therapeutic effects of SHHZF on liver cancer by adjusting the activities of PE N-methyl transferase (PEMT), Lysophospholipase D, methylenetetrahydrofolate reductase (MTHFR) and lysophospholipase was elucidated by the method of metabonomics for the first time.