Transmethylation Research Articles

Variation in DNA Methylation in Avian Nestlings Is Largely Determined by Genetic Effects.

As environmental fluctuations are becoming more common, organisms need to rapidly adapt to anthropogenic, climatic, and ecological changes. Epigenetic modifications and DNA methylation in particular provide organisms with a mechanism to shape their phenotypic responses during development. Studies suggest that environmentally induced DNA methylation might allow for adaptive phenotypic plasticity that could last throughout an organism's lifetime. Despite a number of studies demonstrating environmentally induced DNA methylation changes, we know relatively little about what proportion of the epigenome is affected by environmental factors, rather than being a consequence of genetic variation. In the current study, we use a partial cross-foster design in a natural great tit (Parus major) population to disentangle the effects of common origin from common rearing environment on DNA methylation. We found that variance in DNA methylation in 8,315 CpG sites was explained by a common origin and only in 101 by a common rearing environment. Subsequently, we mapped quantitative trait loci for the brood of origin CpG sites and detected 754 cis and 4,202 trans methylation quantitative trait loci, involving 24% of the CpG sites. Our results indicate that the scope for environmentally induced methylation marks independent of the genotype is limited and that the majority of variation in DNA methylation early in life is determined by genetic factors instead. These findings suggest that there may be little opportunity for selection to act on variation in DNA methylation. This implies that most DNA methylation variation likely does not evolve independently of genomic changes.

Parent of origin genetic effects on methylation in humans are common and influence complex trait variation

Parent-of-origin effects (POE) exist when there is differential expression of alleles inherited from the two parents. A genome-wide scan for POE on DNA methylation at 639,238 CpGs in 5,101 individuals identifies 733 independent methylation CpGs potentially influenced by POE at a false discovery rate ≤ 0.05 of which 331 had not previously been identified. Cis and trans methylation quantitative trait loci (mQTL) regulate methylation variation through POE at 54% (399/733) of the identified POE-influenced CpGs. The combined results provide strong evidence for previously unidentified POE-influenced CpGs at 171 independent loci. Methylation variation at 14 of the POE-influenced CpGs is associated with multiple metabolic traits. A phenome-wide association analysis using the POE mQTL SNPs identifies a previously unidentified imprinted locus associated with waist circumference. These results provide a high resolution population-level map for POE on DNA methylation sites, their local and distant regulators and potential consequences for complex traits.

Substitution of Dietary Sulfur Amino Acids by DL-2-hydroxy-4-Methylthiobutyric Acid Increases Remethylation and Decreases Transsulfuration in Weaned Piglets

ABSTRACTBackgroundDL-2-hydroxy-4-methylthiobutyric acid (DL-HMTBA), an L-methionine (L-Met) hydroxyl analogue, has been suggested to be a dietary L-Met source. How dietary DL-HMTBA compared with L-Met affects whole-body L-Met kinetics in growing individuals is unknown.ObjectivesWe determined to what extent DL-HMTBA supplementation of an L-Met–deficient diet affects whole-body L-Met and L-cysteine (L-Cys) kinetics, protein synthesis (PS), and the L-Met incorporation rate in liver protein (L-MetInc) compared with L-Met and DL-Met supplementation in a piglet model.MethodsForty-five, 28-d-old weaned piglets (male, German Landrace) were allocated to 4 dietary groups: L-Met-deficient diet [Control: 69% of recommended L-Met plus L-Cys supply; 0.22% standardized ileal digestible (SID) L-Met; 0.27% SID L-Cys; n = 12] and Control diet supplemented equimolarly to 100% of recommended intake with either L-Met (n = 12; LMET), DL-Met (n = 11; DLMET), or DL-HMTBA (n = 10; DLHMTBA). At 47 d of age, the piglets were infused with L-[1-13C; methyl-2H3]-Met and [3,3-2H2]-Cys to determine the kinetics and PS rates. Plasma amino acid (AA) concentrations, hepatic mRNA abundances of L-Met cycle and transsulfuration (TS) enzymes, and L-MetInc were measured.ResultsDuring feed deprivation, L-Met kinetics did not differ between groups, and were ≤3 times higher in the fed state (P < 0.01). Remethylation (RM) was 31% and 45% higher in DLHMTBA than in DLMET and Control pigs, respectively, and the RM:transmethylation (TM) ratio was 50% higher in DLHMTBA than in LMET (P < 0.05). Furthermore, TS and the TS:TM ratio were 32% lower in DLHMTBA than in LMET (P < 0.05). L-MetInc was 42% lower in DLMET and DLHMTBA than in L-Met-deficient Control pigs, whereas plasma AA and hepatic mRNA abundances were similar among DL-HMTBA–, L-Met–, and DL-Met–supplemented pigs.ConclusionsIn piglets, DL-HMTBA compared with L-Met and DL-Met supplementation increases RM and reduces the TS rate to conserve L-Met, but all 3 Met isomers support growth at a comparable rate.

Epigenome-wide association study of serum cotinine in current smokers reveals novel genetically driven loci

BackgroundDNA methylation alteration extensively associates with smoking and is a plausible link between smoking and adverse health. We examined the association between epigenome-wide DNA methylation and serum cotinine levels as a proxy of nicotine exposure and smoking quantity, assessed the role of SNPs in these associations, and evaluated molecular mediation by methylation in a sample of biochemically verified current smokers (N = 310).ResultsDNA methylation at 50 CpG sites was associated (FDR < 0.05) with cotinine levels, 17 of which are novel associations. As cotinine levels are influenced not only by nicotine intake but also by CYP2A6-mediated nicotine metabolism rate, we performed secondary analyses adjusting for genetic risk score of nicotine metabolism rate and identified five additional novel associations. We further assessed the potential role of genetic variants in the detected association between methylation and cotinine levels observing 124 cis and 3898 trans methylation quantitative trait loci (meQTLs). Nineteen of these SNPs were also associated with cotinine levels (FDR < 0.05). Further, at seven CpG sites, we observed a trend (P < 0.05) that altered DNA methylation mediates the effect of SNPs on nicotine exposure rather than a direct consequence of smoking. Finally, we performed replication of our findings in two independent cohorts of biochemically verified smokers (N = 450 and N = 79).ConclusionsUsing cotinine, a biomarker of nicotine exposure, we replicated and extended identification of novel epigenetic associations in smoking-related genes. We also demonstrated that DNA methylation in some of the identified loci is driven by the underlying genotype and may mediate the causal effect of genotype on cotinine levels.

Research status on hypermethioninemia

Hypermetioninemia is a group of rare diseases defined by plasma methionine elevation.The causes of hypermethioninemia include genetic and non-genetic factors.Affecting the transmethylation process in the metabolic pathway between methionine and homocysteine is the common inherited methylation disorders.Most patients had completely asymptomatic and only biochemical abnormalities, others with clinical symptoms were also non-specific, such as mental retardation, cognitive impairment, moderate hepatomegaly, dystonia, Marfans syndrome type, osteoporosis, and cardiovascular disease, and etc.A low methionine diet treatment is recommended, the importance of neonatal screening is emphasized and the birth defects can be reduced through prenatal diagnosis, but the necessity remains controversial.The long-term prognosis of this disorders is unknown, the plasma of methionine should be measured at regular intervals, and the individualized follow-up is very important. Key words: Hypermethioninemia; Methionine adenosyltransferase MAT Ⅰ and Ⅲ deficiency; Glycine N-methyltrasferase deficiency; S-adenosylhomocysteine hydrolase deficiency; Cystathionine β-synthase deficiency

Disease variants alter transcription factor levels and methylation of their binding sites.

Most disease-associated genetic variants are noncoding, making it challenging to design experiments to understand their functional consequences. Identification of expression quantitative trait loci (eQTLs) has been a powerful approach to infer the downstream effects of disease-associated variants, but most of these variants remain unexplained. The analysis of DNA methylation, a key component of the epigenome, offers highly complementary data on the regulatory potential of genomic regions. Here we show that disease-associated variants have widespread effects on DNA methylation in trans that likely reflect differential occupancy of trans binding sites by cis-regulated transcription factors. Using multiple omics data sets from 3,841 Dutch individuals, we identified 1,907 established trait-associated SNPs that affect the methylation levels of 10,141 different CpG sites in trans (false discovery rate (FDR) < 0.05). These included SNPs that affect both the expression of a nearby transcription factor (such as NFKB1, CTCF and NKX2-3) and methylation of its respective binding site across the genome. Trans methylation QTLs effectively expose the downstream effects of disease-associated variants.

Arginine or Guanidinoacetic Acid Can Serve as Precursors for Creatine Synthesis in Parenteral Nutrition, but Only with Excess Methionine to Facilitate Transmethylation

Creatine synthesis in neonates demands high amounts of its precursors, arginine and methionine. Parenteral nutrition (PN) is typically marginal in these amino acids and devoid in creatine. The present study investigated the effectiveness of creatine supplementation of PN compared to supplementation with arginine, methionine and the unmethylated intermediate guanidinoacetic acid (GAA). The goal of this study was to determine if PN supplementation with creatine or GAA can spare methionine and/or arginine for other functions. Yucatan miniature‐piglets (6–10 d old; n=31) were fed 1 of 5 elemental PN diets: 1) low arginine and low methionine (Low Arg&amp;Met), 2) low arginine and methionine plus GAA, 3) low arginine and methionine plus creatine, 4) high arginine and high methionine (High Arg&amp;Met), or 5) low arginine with high methionine plus GAA (Met&amp;GAA). After 7 d of feeding, a primed, constant infusion of [3H‐methyl]‐methionine was intravenously infused for 4 h and label incorporation in transmethylation products (creatine, phosphatidylcholine, DNA) and protein were measured. Both High Arg&amp;Met and Met&amp;GAA pigs had greater daily weight gain compared to GAA‐ and creatine‐supplemented pigs (p &lt; 0.05), indicating methionine was deficient in low methionine groups. Moreover, 72‐h nitrogen retention was significantly greater in High Met&amp;Arg and Met&amp;GAA pigs compared to GAA (p &lt; 0.05). These results suggest that because methionine is heavily transmethylated in the neonatal piglet, excess methionine is needed to promote protein synthesis and increase growth. As expected, plasma methionine and arginine concentrations were significantly higher in High Met&amp;Arg compared to Low Arg&amp;Met, GAA and creatine treatments (p &lt; 0.05). Plasma levels of ornithine were significantly higher and glutamine levels were significantly lower in High Met&amp;Arg compared to all other treatments (p &lt; 0.05) suggesting urea cycle metabolism was limited in the low arginine groups. Hepatic fractional synthetic rate of creatine was ~30–40% higher in High Met&amp;Arg and Met&amp;GAA pigs, suggesting creatine synthesis was limited by precursor availability. These results also suggest that PN supplementation of GAA requires excess levels of methionine to facilitate transmethylation to creatine. These results suggest that arginine or GAA is needed to adequately synthesize creatine in PN‐fed piglets, but only when sufficient methionine is fed to provide methyl groups. Moreover, it is clear that the methionine and arginine requirements during PN feeding need to accommodate creatine synthesis.Support or Funding InformationSupported by Canadian Institutes of Health Research and the Janeway Research Foundation

Examination of Global Methylation and Targeted Imprinted Genes in Prader-Willi Syndrome.

Methylation changes observed in Prader-Willi syndrome (PWS) may impact global methylation as well as regional methylation status of imprinted genes on chromosome 15 (in cis) or other imprinted obesity-related genes on other chromosomes (in trans) leading to differential effects on gene expression impacting obesity phenotype unique to (PWS). Characterize the global methylation profiles and methylation status for select imprinted genes associated with obesity phenotype in a well-characterized imprinted, obesity-related syndrome (PWS) relative to a cohort of obese and non-obese individuals. Global methylation was assayed using two methodologies: 1) enriched LINE-1 repeat sequences by EpigenDx and 2) ELISA-based immunoassay method sensitive to genomic 5-methylcytosine by Epigentek. Target gene methylation patterns at selected candidate obesity gene loci were determined using methylation-specific PCR. Study participants were recruited as part of an ongoing research program on obesity-related genomics and Prader-Willi syndrome. Individuals with non-syndromic obesity (N=26), leanness (N=26) and PWS (N=39). A detailed characterization of the imprinting status of select target genes within the critical PWS 15q11-q13 genomic region showed enhanced cis but not trans methylation of imprinted genes. No significant differences in global methylation were found between non-syndromic obese, PWS or non-obese controls. None. Percentage methylation and the methylation index. The methylation abnormality in PWS due to errors of genomic imprinting effects both upstream and downstream effectors in the 15q11-q13 region showing enhanced cis but not trans methylation of imprinted genes. Obesity in our subject cohorts did not appear to impact global methylation levels using the described methodology.

The effects of dietary methyl donors on methionine partitioning in the neonatal piglet

The metabolism of the indispensable amino acid methionine is critical during development. Methionine is used to synthesize protein for growth and, using the methionine cycle, it is the precursor of &gt;50 critical nutrients and contributes to epigenetic regulation. Therefore, the dietary methionine requirement must factor all the potential roles of methioine. Three major processes summarize the methionine cycle: transmethylation (TM), which transfers methyl groups to nutrient precursors and DNA; transsulfuration (TS), which represents methionine disposal; and remethylation (RM), which resynthesizes methionine using the dietary methyl donors folate and choline (via betaine). Dietary intakes of folate vary drastically, and choline intakes are often below the adequate intakes during pregnancy and in early life, which we hypothesized would influence the methionine requirement. To test our hypothesis, we fed 4- to 8-day-old neonatal piglets a low-methionine diet that was either deficient (MD−) or replete (MS+) in dietary methyl donors. We evaluated how methionine was balanced between the major TM reactions and protein synthesis. The MD− group exhibited marked differences in TM as creatine synthesis was ≈30% less (p &lt; 0.05) and phosphatidylcholine synthesis was ≈60% more (p &lt; 0.05) during MD− feeding. Interestingly, while MD− feeding did not affect liver protein synthesis, the methionine availability and protein synthesis were lower in skeletal muscle of the MD− versus MS+ animals (p &lt; 0.05). Furthermore, whole-body protein turnover was also reduced during MD− feeding (p &lt; 0.05), which is significant as protein turnover is especially critical during infancy. Next, we measured the effect of methyl donors on the rates of TM, TS, and RM. The rates of RM and TM were reduced by ≈75% in the MD− group (p &lt; 0.05), while TS was unchanged. To evaluate the effectiveness of individual methyl donors on RM, we “rescued” a second group of MD− animals with betaine (MD + B), folate (MD + F) or both (MD + FB). The rate of RM and TM increased by ≈2-fold after rescue (p &lt; 0.05) and reduced protein breakdown (p &lt; 0.05). These studies showed that dietary methyl donors affect neonatal methionine metabolism, which should be considered when defining the dietary requirements of methionine during development.

EXPLORING MECHANISM OF RESISTANCE TO ISOPROTHIOLANE IN MAGNAPORTHE ORYZAE, THE CAUSAL AGENT OF RICE BLAST

The fungicide isoprothiolane (IPT) has widely been used to control the rice blast fungus Magnaporthe oryzae for decades. However, the molecular mechanism of resistance is still unexplained and was only believed to be associated with transmethylation in the biosynthesis of phosphatidylcholine. In this study we tested IPT sensitivity of hundreds of M. oryzae isolates collected from Yunnan and Hubei provinces of China. Three IPT-resistant mutants were generated by exposing the mycelium to increasing concentrations of IPT. No fitness penalty was observed in these resistant mutants. In consideration of the role on transmethylation in the biosynthesis of phosphatidylcholine, three candidate genes, PEAMT, CHO2, and OPI3, were sequenced, and their expression profile determined. There was no significant difference in the expression of these genes between resistant mutants and sensitive parental isolates. Additionally, Solexa sequencing was conducted to screen potential target genes. MGG_09793 was the most frequently changed gene between resistant mutant H08-1a_mut and sensitive parental isolate H08-1a after IPT treatment. After knockout, this gene in H08-1a_mut and H08-1a, resistance status did not change. This study indicates that the expected PEAMT, CHO2 and OPI3 genes were not responsible for IPT resistance. Interestingly, the DJ-1/PfpI family protein MGG_09793 was specifically and strongly induced by IPT treatment in sensitive isolates.

Remethylation with dietary methyl donors contributes a significant proportion of methionine for the synthesis of protein and creatine in neonatal piglets (258.3)

Methionine is an essential amino acid that is in high demand in neonates for both protein synthesis and as the primary methyl donor for transmethylation (TM) reactions. The vast majority of methyl groups are used for synthesis of creatine (CR) and phosphatidylcholine (PC). The demethylated methionine can be remethylated by dietary methyl donors such as folate, choline and betaine, but to what extent is unclear. We hypothesized that these methyl donors provide a nutritionally significant proportion of available methionine for TM and protein synthesis. 4‐8 d old piglets were fed a diet devoid (n=8) or replete (n=7) of methyl donors at 80% of the methionine requirement; methionine and phenylalanine isotopes were infused to calculate flux to products. Whole body protein synthesis and breakdown were respectively, 15% (p&lt;0.05) and 20% (p&lt;0.04) lower during methyl deficiency, corresponding to a ~70% reduction in fractional protein synthesis (Ks) in muscle (p&lt;0.03) and unchanged Ks in liver. Methyl deficiency also led to 25% lower hepatic TM to creatine (p&lt;0.02), which was offset by a 2‐fold greater TM to PC (p&lt;0.03), due to choline deficiency which increases PC synthesis via TM. In conclusion, dietary methyl donors can re‐synthesize a substantial proportion of methionine that is used primarily for protein synthesis and potentially growth.Grant Funding Source: Supported by CIHR

Betaine is as effective as folate at re‐synthesizing methionine for protein synthesis during moderate methionine deficiency in piglets (827.15)

Methionine is an essential amino acid that is in high demand in neonates for protein synthesis as well as for transmethylation (TM) reactions, such as creatine synthesis and DNA methylation. TM reactions produce homocysteine, which can be either converted to cysteine or re‐methylated to methionine via folate or betaine (synthesized from choline). It is unclear whether both remethylation pathways are equally important in neonates for remethylation. The objective of this study was to determine whether supplementation with folate, betaine or a combination of both (n=6) can re‐synthesize methionine for protein synthesis when dietary methionine is limiting. In piglets adapted to low‐methionine diets devoid of folate, choline and betaine, we measured 13C‐phenylalanine oxidation pre‐ and post‐supplementation as an indicator of protein synthesis. Prior to supplementation, plasma folate (‐60%), betaine (‐95%), dimethylglycine (‐95%), choline (‐60%) and cysteine (‐45%) were all lower (p&lt;0.05) compared to baseline with no change in homocysteine. Post‐supplementation, phenylalanine oxidation levels were ~30% lower (p&lt;0.05) with any methyl donor supplementation with no difference among groups. This demonstrates an equal capacity for betaine and folate to remethylate methionine for protein synthesis and warrants future research on betaine in the infant diet.Grant Funding Source: Supported by Canadian Institutes of Health Research

Transitive RNA silencing signals induce cytosine methylation of a transgenic but not an endogenous target

Post-transcriptional gene silencing of a primary target gene in plants can coincide with the production of secondary small interfering RNAs (siRNAs) of coding sequences adjacent to the target region and with de novo RNA-directed DNA methylation (RdDM) thereof. Here, we analyzed the susceptibility of transgenic and endogenous targets to RdDM induced by primary and secondary silencing signals. In three different configurations, primary silencing signals were able to direct in trans methylation of chimeric transgenes and the CATALASE2 (CAT2) endogene; however, extensive spreading of methylation occurred only in the transgene, resulting in the methylation of the flanking CAT2 sequence, whereas methylation of the CAT2 endogene was restricted to the target region and the enclosed introns. The secondary silencing signals arising from this transgenic primary target simultaneously silenced a secondary transgene target and the CAT2 endogene, but were only capable of directing RdDM to the transgene. Our data indicate that RdDM is correlated with the in situ generation of secondary siRNAs, occurring in P35S-driven transgenes but not in most endogenes. We conclude that although both endogenes and transgenes are equally sensitive to transitive silencing, differences exist in their susceptibility to undergo secondary RdDM.

Methyl group partitioning during insufficient and excess availability via guanidinoacetate and creatine supplementation in young pigs

Methionine is an essential amino acid that provides methyl groups for transmethylation (TM) reactions via S‐adenosylmethionine (SAM), resulting in S‐adenosylhomocysteine (SAH), an inhibitor of TM reactions. Methylation of guanidinoacetate (GAA) to produce creatine (Cr) is proportional to GAA availability while Cr supplementation reduces GAA production and spares methyl groups. Our objective was to determine the partitioning of methyl groups among TM reactions under conditions of excess and insufficient methyl group availability. Three mo‐old pigs (n=18) were fed control, GAA‐ or Cr‐supplemented diets twice daily. On day 18, anesthesia was induced 1–3 h post feeding and a bolus of [methyl‐3H]methionine was intravenously infused. After 30 min, the liver was analyzed for methyl‐3H incorporation into protein, Cr, phosphatidylcholine (PC) and DNA. Compared to control (P&lt;0.05), Cr and GAA led to a 200% and 700% increase in hepatic Cr concentration, respectively; GAA caused a 400% increase in total hepatic Cr methyl‐3H incorporation. Unlike Cr pigs, GAA supplementation decreased methyl‐3H incorporation into PC and decreased hepatic SAM concentration with no change in SAH, suggesting that creatine synthesis resulted in a limited methyl supply for PC synthesis (P&lt;0.05). Creatine supplementation did not spare methyl groups, but GAA did lead to a limited methyl supply (CIHR).Grant Funding Source: CIHR

SAM-e AND ITS THERAPEUTIC PRINCIPLES

S-Adenosylmethionine (SAM-e) which is an well-known super nutrient in countries like Europe , Italy, but unfortunately it is unknown in many countries, which is mainly available as nutrient supplement, same though it is not a completely new compound but can be found in our tissues performing trans methylation reaction(methyl donor) with  Iupac name as  [(3S)-3-amino-3-carboxypropyl]({[(2S,3S,4R,5R)-5-(6-amino-9H-purin-9-yl)-3,4-dihydroxyoxolan-2-yl]methyl})methylsulfanium .SAM-e stands first among all other drugs in treating depression, cirrhosis, osteoarthritis, Alzheimer disease, Though it was discovered in 1952 it self but it does not came in to lime light, much more studies are to be conducted to evaluate it uses and even the way it works can be inspiring to us in preparing its derivatives. Alcoholic cirrhosis patients when given SAM-e miraculously cured just by increasing the regeneration efficacy of the liver, this article mainly discuss the uses of SAMe and the principle mechanism involved in it.

Whole body methionine kinetics, transmethylation, transulfuration and remethylation during pregnancy

There is evidence from a study of pregnant American women that methionine transmethylation (TM) and remethylation (RM) rates increases and transulfuration (TS) decreases as pregnancy progresses from trimester 1 to 3. To determine whether pregnant Indian women can make this adaptation successfully, methionine kinetics, TS, TM, and RM were measured in Indian women in early and late pregnancy. Measurements were made in the postabsorptive and fed states in the 1st and 3rd trimesters of pregnancy by infusing 1-(13)C,(2)H3-methionine in 24 women, 12 with low (≤150 pmol L(-1)) and 12 with normal (≥200 pmol L(-1)) vitamin B12 status at recruitment. From trimester 1 to 3, except RM which decreased significantly, there was no change in any weight-specific methionine kinetic parameter. When expressed per whole body, methionine flux from protein breakdown increased significantly from trimester 1 to 3 in the fed and postabsorptive states. Flux to protein synthesis also increased significantly in the fed state. Rates of TM, TS and RM did not change, regardless of vitamin B12 status at recruitment. Protein and methionine intakes correlated with TM and RM rates and the change in RM from trimester 1 to 3 correlated with the change in dietary protein intake. These results suggest that methionine flux and its utilization for protein synthesis increases in Indian women as pregnancy progresses from trimester 1 to 3. TM and RM rates do not increase however, possibly because of inadequate protein intake and not because of vitamin B12 deficiency at trimester 1.

Epigenetic Alterations caused by Decreased Cellular Methylation Potential Induce Fas‐FasL‐mediated Apoptotic Death in Leukemic T Lymphocytes

The transmethylation (TM) pathway is up regulated in proliferating T cells and transformed T leukemic cells but not in resting T cells, making it an ideal target to eliminate leukemic T cells. The TM pathway involves methyltransferase‐mediated conversion of S‐adenosylmethionine (SAM) to S‐adenosylhomocysteine (SAH). SAH is a potent feedback inhibitor of methyltransferases and is hydrolyzed by S‐adenosylhomocysteine hydrolase (SAHH), which determines the SAM: SAH ratio, known as the cellular methylation potential.The role of cellular methylation potential in the regulation of cell death in T leukemic cell lines was examined by inhibiting SAHH using pharmacologic SAHH inhibitors and RNAi. We demonstrate that a decrease in cellular methylation potential induces apoptosis in leukemic T lymphocytes. SAHH inhibitor treatment increases expression of FasL protein and activates the Fas‐FasL signaling pathway. Additionally, we observed an up regulation of FasL mRNA expression in leukemic T cells. ChIP analysis of histone H3 modifications at the FasL promoter showed increased transcriptional activation marks, namely acetylation at lysine 9 and 14, trimethylation at lysine 4 and increased recruitment of RNA Polymerase II. Overall, the data indicate the mechanistic role of cellular methylation potential in transcriptional regulation of FasL gene resulting in enhanced leukemic T cell death.

The biochemical and toxicological significance of hypermethionemia: new insights and clinical relevance

Importance of the field: Disrupted l-methionine (Met) metabolism can lead to hepatic, neurological and cardiovascular dysfunction in humans. Aberrant methyl group flux likely contributes to the development of these pathologies, but when patients also become hypermethionemic, additional toxicological mechanisms may be relevant.Areas covered in this review: Following a discussion of the causes of hypermethionemia in humans, evidence for the toxicological roles and clinical significance of the Met transmethylation (TM), transamination (TA) and sulfoxidation (SO) pathways will be presented.What the reader will gain: Recent data from freshly isolated mouse hepatocytes (FIMHs) confirmed previous in vivo results in rodents that Met TM is a detoxification pathway while Met TA leads to toxicity. Gender-related differences in Met accumulation and metabolism in FIMHs correlated with gender differences in toxicity. Data obtained from FIMHs also implicated Met SO in Met metabolism and toxicity. Currently, little is known about the mechanisms and biological significance of Met sulfoxidation in humans.Take home message: In hypermethionemic patients, clinical and dietary interventions should focus on increasing Met TM and decreasing Met TA and SO. Novel biomarkers of hypermethionemia in humans that correlate with pathological end points are needed to better understand the impact of the condition.

B‐vitamin deficiency is protective in experimental colitis

Methionine (Met) cycle activity is critical for normal cell functions and requires B‐vitamin (B6/B12) as cofactors. S‐adenosylhomocysteine (SAH) is a Met cycle intermediates that is known to inhibit methyltransferases. Met metabolism is altered in patients with inflammatory bowel disease (IBD), but Met's role in IBD is poorly understood. We hypothesize that accumulation of Met metabolites due to B‐vitamin deficiency is protective in experimental colitis. Mice received either a control diet (C) or a B6/B12‐deficient diet (D) to disrupt Met metabolism for 2 weeks and were challenged for 5 days with 3% dextran sulfate sodium (DSS) to induce colitis. Clinical and histological disease indices were reduced in D compared to C, along with the colonic expression of the proinflammatory genes (TNFα and iNOS) and myeloperoxidase activity. Whole body Met flux was assessed by infusing 13C‐2H3‐Met and measuring transmethylation (TM), transsulfuration (TS) and remethylation (RM). Plasma TS was reduced but RM was increased in D mice. TM was not different between groups. Colonic SAH and plasma Met abundance also were elevated in D mice compared to C. The protective effect of B‐vitamin deficiency is associated with reduced inflammation and tissue injury. We postulate that colonic SAH accumulation reduces methyltransferase activity and leads to epigenetic suppression of proinflammatory gene expression. Funded by USDA.Grant Funding Source: USDA

Inhibition Of Transmethylation (TM) Leads To Histone Modifications And Plays A Critical Role In The Epigenetic Regulation Of IL‐2 Gene Expression In Primary Human CD4+ T Lymphocytes

IL‐2 is a critical lymphokine that exerts a wide spectrum of regulatory effects on the immune system. Recent work done in our laboratory has demonstrated that S‐adenosylmethionine (SAM) dependent transmethylation (TM) is essential for the function of CD4+ T lymphocytes including IL‐2 expression. SAM dependent TM impacts epigenetic changes involving histone modifications which play a key role in altering chromatin structure and transcriptional activity. The TM pathway can be significantly inhibited by the SAM metabolite S‐adenosylhomocysteine (SAH). Accordingly, the present work was carried out to examine the effect of decreased TM due to increased cellular SAH levels on IL‐2 gene expression in primary human CD4+ T cells.Decreased SAM‐dependent methylation due to an increase in cellular SAH levels was achieved by treating the cells with an SAHH inhibitor, 3‐deazaadenosine (DZA). Examination of histone modifications occurring due to decreased SAM‐dependent methylation showed a decrease in the acetylated state of histone H3 at the IL‐2 proximal promoter region which is associated with the induction of gene transcription and expression. These data strongly support the notion that histone H3 acetylation is a critical epigenetic modification that regulates IL‐2 gene expression in primary human CD4+ T cells.