Dietary Methionine Intake Research Articles

Association of MTHFR polymorphism, folic acid and vitamin B12 with serum homocysteine levels in pregnant women.

Homocysteine is known to be associated with adverse vascular and metabolic effects, as well as pregnancy complications. Its serum levels are influenced by the function of the enzyme methylenetetrahydrofolate reductase (MTHFR) and the dietary intake of folic acid, vitamin B12, and methionine. In this cross-sectional study, we investigated the association of genetic polymorphisms of the MTHFR gene with vitamin status in pregnant women during mandatory folic acid supplementation. The study included 102 pregnant women between 24 and 28 weeks of gestation who were attending regular outpatient examinations at the maternity clinic. Homocysteine, folic acid, vitamin B12 levels, and MTHFR gene polymorphisms (C677T and A1298C) were analyzed. Significant associations were found between vitamin B12 and folic acid levels with homocysteine (P < 0.001), with lower serum levels of these vitamins being associated with higher homocysteine levels. Surprisingly, there was no significant association between MTHFR genetic polymorphisms and serum homocysteine levels, likely attributed to the supplementation of folic acid and vitamin B12 in vitamin supplements for pregnant women, which counteracts the effect of the mutation. Remarkably, a high prevalence of MTHFR gene mutations was found, with the C677T polymorphism present in 56.9% and the A1298C polymorphism in 87.2% of pregnant women. These findings emphasize the importance of adequate folic acid and vitamin B12 intake during pregnancy to regulate homocysteine levels. Although the MTHFR gene mutations were highly prevalent, their influence on homocysteine levels in this population appears to be mitigated by vitamin supplementation. Further research is warranted to explore the impact of these mutations on other aspects of pregnancy outcomes. The trial is registrated at Clinicaltrail.gov (NCT04952324).

Dietary intakes of methionine, threonine, lysine, arginine and histidine increased risk of type 2 diabetes in Chinese population: does the mediation effect of obesity exist?

BackgroundPublished studies have shown positive associations of branched chain and aromatic amino acids with type 2 diabetes mellitus (T2DM), and the findings remain consistent. However, the associations of other essential and semi-essential amino acids, i.e., methionine (Met), threonine (Thr), lysine (Lys), arginine (Arg) and histidine (His), with T2DM remain unknown. Obesity is an important independent risk factor for T2DM, and excessive amino acids can convert into glucose and lipids, which might underlie the associations of amino acids with obesity. Therefore, we aimed to estimate the associations between dietary intakes of these 5 amino acids and T2DM risk, as well as the mediation effects of obesity on these associations, in a Chinese population.MethodsA total of 10,920 participants (57,293 person-years) were included, and dietary intakes of 5 amino acids were investigated using 24-h dietary recalls. Anthropometric obesity indices were measured at both baseline and the follow-up endpoints. Associations of amino acids with T2DM were estimated using COX regression models, hazard ratios (HRs) and 95% confidence intervals (95% CIs) were shown. The mediation effects of obesity indices were analyzed, and the proportion of the mediation effect was estimated.ResultsHigher intakes of the 5 amino acids were associated with increasing T2DM risk, while significant HRs were only shown in men after adjustments. No interaction by gender was found. Regression analyses using quintiles of amino acids intakes showed that T2DM risk was positively associated with amino acids intakes only when comparing participants with the highest intake levels of amino acids to those with the lowest intake levels. Adjusted correlation coefficients between amino acid intakes and obesity indices measured at follow-up endpoints were significantly positive. Mediation analyses showed that mediation effects of obesity indices existed on associations between amino acids intakes and T2DM risk, and the mediation effect of waist circumference remained strongest for each amino acid.ConclusionsWe found positive associations of dietary intakes of Met, Thr, Lys, Arg and His with increasing T2DM risk in general Chinese residents, on which the mediation effect of obesity existed. These findings could be helpful for developing more constructive guidance in the primary prevention of T2DM based on dietary interventions.

Effects of methionine intake on cognitive function in mild cognitive impairment patients and APP/PS1 Alzheimer's Disease model mice: Role of the cystathionine-β-synthase/H2S pathway

As a dietary intervention, methionine restriction (MR) has been reported to increase longevity and improve metabolism disorders. However, the effects of MR on alleviating neurodegenerative diseases such as Alzheimer's disease (AD) are largely unexplored. Here we sought to investigate the neuroprotective effects of low methionine intake in mild cognitive impairment (MCI) patients and APP/PS1 AD model mice, and to uncover the underlying mechanisms. In a cohort composed of 45 individuals diagnosed with MCI and 61 healthy controls without cognitive impairment, methionine intake was found to be positively associated with the increased risk of MCI, where no sex differences were observed. We further conducted a 16-week MR intervention (0.17% methionine, w/w) on APP/PS1 AD model mice. Although MR reduced Aβ accumulation in the brain of both male and female APP/PS1 mice, MR improved cognitive function only in male mice, as assessed by the Morris water maze test. Consistently, MR restored synapse ultrastructure and alleviated mitochondrial dysfunction by enhancing mitochondrial biogenesis in the brain of male APP/PS1 mice. Importantly, MR effectively balanced the redox status and activated cystathionine-β-synthase (CBS)/H2S pathway in the brain of male APP/PS1 mice. Together, our study indicated that lower dietary methionine intake is associated with improved cognitive function, in which CBS/H2S pathway plays an essential role. MR could be a promising nutritional intervention for preventing AD development.

Comparative analysis of methyl–donor nutrient intakes and RCPM cognitive performance among school-aged children

Evidence shows a link between methyl-donor nutrient intakes and a child's cognitive ability. However, this is less known among Ghanaian children who might be at higher risk of methyl-donor nutrient deficiencies. This study showed comparative analysis of methyl-donor nutrient intakes and Raven's Coloured Progressive Matrices (RCPM) test performance among 2073 Ghanaian school children aged 9-13 years across four regions of Ghana. Data for the present study were obtained from the Child Nutrition, Fitness, and Cognition project; a cross-sectional survey conducted in four regions of Ghana. Dietary methyl-donor nutrient values were based on repeated 24h recall data collected during the study periods. Cognitive tests were performed on the 2073 children using Raven's Coloured Progressive Matrices (RCPM) test. We found dietary zinc (adjusted: β=0.21, p=0.003) and methionine (adjusted: β=0.60, p=0.044) intakes to be associated with RCPM scores in the linear regression model. School children living in Northern Region (adjusted OR=0.6, p<0.001, 95% CI=0.4-0.7) and Volta Region (adjusted OR=0.7, p=0.006, 95% CI=0.5-0.9) had lower odds of scoring above the 50th percentile on the RCPM test compared with those living in Greater Accra Region. Children who consumed below the RDA for dietary folate (unadjusted OR=0.8, p=0.055, 95% CI=0.7-1.0) and zinc (unadjusted OR=0.8, p=0.049, 95%CI=0.7-1.0) had lower odds of scoring above the 50th percentile on the RCPM test compared with those who consumed above the RDA for dietary folate and zinc respectively. Children who consumed below the EAR for dietary vitamin B12 (unadjusted OR=0.7, p=0.004, 95% CI=0.6-0.9) had reduced odds of scoring above the 50th percentile on the RCPM test compared with those who consumed above the EAR for dietary vitamin B12. Higher dietary methionine intake was strongly associated with higher RCPM scores. Regional differences, and children's dietary consumption below the EAR/RDA for dietary folate, vitamin B12, and zinc were associated with poor RCPM test performance. School children's nutrient intake should be prioritized for improved cognition.

Cysteine restriction-specific effects of sulfur amino acid restriction on lipid metabolism.

Decreasing the dietary intake of methionine exerts robust anti-adiposity effects in rodents but modest effects in humans. Since cysteine can be synthesized from methionine, animal diets are formulated by decreasing methionine and eliminating cysteine. Such diets exert both methionine restriction (MR) and cysteine restriction (CR), that is, sulfur amino acid restriction (SAAR). Contrarily, SAAR diets formulated for human consumption included cysteine, and thus might have exerted only MR. Epidemiological studies positively correlate body adiposity with plasma cysteine but not methionine, suggesting that CR, but not MR, is responsible for the anti-adiposity effects of SAAR. Whether this is true, and, if so, the underlying mechanisms are unknown. Using methionine- and cysteine-titrated diets, we demonstrate that the anti-adiposity effects of SAAR are due to CR. Data indicate that CR increases serinogenesis (serine biosynthesis from non-glucose substrates) by diverting substrates from glyceroneogenesis, which is essential for fatty acid reesterification and triglyceride synthesis. Molecular data suggest that CR depletes hepatic glutathione and induces Nrf2 and its downstream targets Phgdh (the serine biosynthetic enzyme) and Pepck-M. In mice, the magnitude of SAAR-induced changes in molecular markers depended on dietary fat concentration (60% fat >10% fat), sex (males > females), and age-at-onset (young > adult). Our findings are translationally relevant as we found negative and positive correlations of plasma serine and cysteine, respectively, with triglycerides and metabolic syndrome criteria in a cross-sectional epidemiological study. Controlled feeding of low-SAA, high-polyunsaturated fatty acid diets increased plasma serine in humans. Serinogenesis might be a target for treating hypertriglyceridemia.

Changes in Dietary Intake of Methionine, Folate/Folic Acid and Vitamin B12 and Survival in Postmenopausal Women with Breast Cancer: A Prospective Cohort Study.

Previous experimental studies showed that limiting methionine in the diet of animals or in cell culture media suppresses mammary cancer cell proliferation or metastasis. However, no previous study has investigated the associations of changes in methionine intake with survival among breast cancer survivors. We aimed to examine the association between changes in dietary intake of methionine, folate/folic acid, and vitamin B12 from before to after diagnosis of breast cancer, and mortality among breast cancer survivors. We included 1553 postmenopausal women from the Women's Health Initiative who were diagnosed with invasive breast cancer and completed a food frequency questionnaire both before and after breast cancer diagnosis. Multivariable Cox proportional hazards regression models were used to estimate adjusted hazard ratios (HRs) and 95% confidence (CIs) of all-cause and breast cancer mortality associated with changes in methionine intake and changes in folate/folic acid and vitamin B12 intake. Relative to pre-diagnosis, 28% of women decreased methionine intake by ≥20%, 30% of women increased methionine intake by ≥20%, and 42% of women had a relatively stable methionine intake (±19.9%) following breast cancer diagnosis. During a mean 16.1 years of follow up, there were 772 deaths in total, including 195 deaths from breast cancer. Compared to women with relatively stable methionine intake, women with decreased methionine intake had lower risks of all-cause (HR 0.78, 95% CI 0.62-0.97) and breast cancer mortality (HR 0.58, 95% CI 0.37-0.91) in fully adjusted models. In contrast, increased methionine intake or changes in folate/folic acid or vitamin B12 intake were not associated with all-cause or breast cancer mortality. Among breast cancer survivors, decreased methionine intake after breast cancer diagnosis was associated with lower risk of all-cause and breast cancer mortality.

High water temperature raised the requirements of methionine for spotted seabass (Lateolabrax maculatus).

This study evaluated the effects of dietary methionine level and rearing water temperature on growth, antioxidant capacity, methionine metabolism, and hepatocyte autophagy in spotted seabass (Lateolabrax maculatus). A factorial design was used with six methionine levels [0.64, 0.85, 1.11, 1.33, 1.58, and 1.76%] and two temperatures [moderate temperature (MT): 27 ℃, and high temperature (HT): 33 ℃]. The results revealed the significant effects of both dietary methionine level and water temperature on weight gain (WG) and feed efficiency (FE), and their interaction effect was found on WG (P < 0.05). In both water temperatures tested, fish WG increased with increasing methionine level up to 1.11% and decreased thereafter. The groups of fish reared at MT exhibited dramatically higher WG and FE than those kept at HT while an opposite trend was observed for feed intake. Liver antioxidant indices including reduced glutathione and malondialdehyde (MDA) concentrations, and catalase and superoxide dismutase (SOD) activities remarkably increased in the HT group compared to the MT group. Moreover, the lowest MDA concentration and the highest SOD activity were recorded at methionine levels between 1.11% and 0.85%, respectively, regardless of water temperatures. Expression of methionine metabolism-related key enzyme genes (mat2b, cbs, ms, and bhmt) in the liver was increased at moderate methionine levels, and higher expression levels were detected at MT compared to HT with the exception of ms gene relative expression. Relative expression of hepatocyte autophagy-related genes (pink1, atg5, mul1, foxo3) and hsp70 was upregulated by increasing methionine level up to a certain level and decreased thereafter and increasing water temperature led to significantly enhanced expression of hsp70. In summary, HT induced heat stress and reduced fish growth, and an appropriate dietary methionine level improved the antioxidant capacity and stress resistance of fish. A second-order polynomial regression analysis based on the WG suggested that the optimal dietary methionine level for maximum growth of spotted seabass is 1.22% of the diet at 27 ℃ and 1.26% of the diet at 33 ℃, then 1.37g and 1.68g dietary methionine intake is required for 100g weight gain at 27 ℃ or 33 ℃, respectively.

Association between dietary intake of one-carbon metabolism nutrients and hyperglycemia in coal-burning fluorosis areas of Guizhou, China.

Background and aimsThere are limited studies describing the association between dietary intake of one-carbon metabolism nutrients and hyperglycemia. The present study aimed to investigate the association of habitual dietary intake of one-carbon metabolism nutrients with hyperglycemia in a fluorosis area in China, and explored the interaction between these nutrients and fluorosis related to hyperglycemia.MethodIn a cross-sectional study, we recruited 901 villagers, ages ranging from 18–75, in Guizhou Province. Dietary data and other covariate data were obtained through an interviewer-administered questionnaire. We collected venous blood samples from participants who had fasted for one night to obtain fasting blood glucose levels and we categorized dietary intake of betaine, total choline, methionine, folate, vitamins B6 and B12, and choline subclasses into quartiles (Q1–Q4). The lowest quartile (Q1) served as the reference group. An unconditional logistic regression model was used to evaluate the protective effects of a dietary intake of one-carbon nutrients against hyperglycemia. We calculated Odds Ratios (ORs) with 95% confidence intervals (CIs). A presence or absence of fluorosis subgroup analysis was performed to determine the potential effect of fluorosis on hyperglycemia.ResultAfter adjusting for potential confounding factors, we found that a greater intake of dietary vitamin B6, total choline and methyl-donor index was inversely associated with the occurrence of hyperglycemia (P-trend <0.05). However, there were no significant associations between hyperglycemia and the dietary intake of folate, vitamin B12, methionine, and betaine. As for the choline subgroups, it showed that the dietary intake of free choline, phosphatidylcholine, and glycerol phosphatidylcholine was negatively correlated with the occurrence of hyperglycemia (P < 0.05). In contrast, there was no statistical association between dietary phosphatidylcholine and sphingomyelin and hyperglycemia (all P > 0.05). The results of subgroup analysis showed that dietary intake of folate, vitamin B6, total choline, free choline, glycerol phosphorylcholine, and phosphocholine had a protective effect against the occurrence of hyperglycemia in the non-fluorosis subgroup, although no effects were observed in the fluorosis subgroup. There were significant interactions between these nutrients and fluorosis (P = 0.010–0.048).ConclusionThe study demonstrated that higher dietary intake of vitamin B6, total choline, methyl-donor index, free choline, glycerol phosphorylcholine, and phosphocholine in choline compounds were associated with a lower incidence of hyperglycemia. Moreover, the associations were modified by the presence or absence of fluorosis. Further investigation is needed to test the association in large-scale follow-up studies.

High dietary methionine intake may contribute to the risk of nonalcoholic fatty liver disease by inhibiting hepatic H2S production

Methionine, an essential sulfur-containing amino acid, is associated with hepatic lipid accumulation; however, the underlying mechanism is unknown. This study aimed to investigate the effects of different dietary methionine levels on hepatic lipid accumulation in mice and clarify the possible mechanisms involved. The Institute of Cancer Research (ICR) mice were fed a normal diet (ND, 0.86% methionine), high-methionine diet (HMD, 2.58% methionine), or methionine-restricted diet (MRD, 0.17% methionine) for 11 consecutive weeks. Our results showed that HMD increased the liver weight and liver index, plasma and hepatic lipid profiles, and hepatic fatty infiltration area and perirenal fat volume. In addition, HMD promoted lipid synthesis, inhibited lipid catabolism and glycolysis metabolism, reduced the activities of mitochondrial respiratory chain enzyme complexes (Ⅰ and Ⅴ) and adenosine triphosphate (ATP) production, and elevated oxidative stress and inflammation in the liver. Moreover, HMD inhibited homocysteine metabolism and significantly decreased the expression and activity of cystathionine γ-lyase (CSE) and 3-mercaptopyruvate sulfurtransferase (3-MST), thereby reducing endogenous H2S production in the liver. Interestingly, MRD reversed these adverse effects, and promoted endogenous H2S production. In conclusion, inhibition of hepatic H2S production may be the mechanism behind an increased risk of nonalcoholic fatty liver disease (NAFLD) associated with high dietary methionine intake. Therefore, it is necessary to reduce methionine intake in the daily diet to prevent NAFLD and maintain good physical health.

Pre-diagnosis Dietary One-Carbon Metabolism Micronutrients Consumption and Ovarian Cancer Survival: A Prospective Cohort Study.

Background and AimsEpidemiological evidence on the relation between one-carbon metabolism (OCM) micronutrients intake and ovarian cancer (OC) survival are limited and conflicting. We evaluated the aforementioned associations in a prospective cohort-the Ovarian Cancer Follow-Up Study.MethodsA total of 635 newly diagnosed OC patients aged 18–79 y were enrolled in the present study. Dietary intake related to one-carbon metabolism, including methionine, vitamins B2, B3, B6, B9, B12, choline, and betaine, was assessed using a validated 111-item food frequency questionnaire. Deaths were ascertained until March 31, 2021, via medical records and active follow-up. Cox proportional hazards regression model was used to evaluate the hazard ratios (HRs) and 95% confidence intervals (CIs) for these aforementioned associations.ResultsDuring a median follow-up of 37.2 months (interquartile: 24.7–50.2 months), 114 deaths were identified. We observed an improved survival with the highest compared with the lowest tertile of dietary vitamin B6 (HR = 0.52, 95%CI: 0.32–0.84, P-trend <0.05) and choline intake (HR = 0.50, 95%CI: 0.30–0.83, P-trend <0.05). No significant associations with OC survival were observed for dietary vitamins B2, B3, B9, B12, methionine, and betaine intake. We also observed a curvilinear association between vitamin B6 intake and OC survival (P non-linear <0.05).ConclusionOur study suggests that pre-diagnosis higher intake of vitamin B6 and choline may improve OC survival. Further clarification of these associations is warranted.

Association of B Vitamins and Methionine Intake with the Risk of Gastric Cancer: The Japan Public Health Center-based Prospective Study.

Dietary intake of B vitamins and methionine might associate with carcinogenesis due to their role in DNA synthesis and methylation. Owing to the previous inconsistent findings on gastric cancer risk, we aimed to examine the associations between dietary intakes of B vitamins and methionine and the risk of gastric cancer, according to sodium intake.We included 86,820 Japanese individuals who completed a validated food frequency questionnaire with 138 food items in the Japan Public Health Center-based Prospective Study. Cox proportional hazards regression was used to obtain HRs and 95% confidence intervals (CI) of gastric cancer according to separate intakes of folate, vitamin B6, vitamin B12, and methionine after adjusting for confounding factors, including Helicobacter pylori and atrophic gastritis in the subgroup analysis.We identified 2,269 gastric cancer cases within a median of 15.4 years of follow-up. We found no association between any of the dietary intakes of folate, vitamin B6, vitamin B12, or methionine with the risk of gastric cancer. In the stratified analysis by sodium intake, we observed a positive association between folate intake and risk of gastric cancer among participants with a high sodium intake (≥4.5 g/day) [HR = 1.28 (95% CI, 1.06-1.56), P trend = 0.001; P interaction = 0.02]. Meanwhile, there was no association between folate intake and risk of gastric cancer among participants with low sodium intake (<4.5 g/day) [HR = 0.94 (95% CI, 0.73-1.21), P trend = 0.49].In conclusion, we found no association between any dietary intakes of folate, vitamin B6, vitamin B12, and methionine with the risk of gastric cancer. PREVENTION RELEVANCE: The increased intake of B vitamins and methionine in populations with adequate dietary intake of these nutrients showed no association with the risk of gastric cancer.

Dietary intake of one-carbon metabolism-related nutrients and hepatocellular carcinoma survival in the Guangdong Liver Cancer Cohort.

Dietary intake of one-carbon metabolism-related nutrients has been linked to cancer-related outcomes, but their effects on hepatocellular carcinoma (HCC) mortality are still unknown. The objective was to assess whether pre-diagnostic dietary intakes of methionine, folate, Vitamin B6, Vitamin B12, riboflavin and niacin are associated with HCC survival in this prospective cohort study. In total, 905 newly diagnosed HCC patients were recruited in the Guangdong Liver Cancer Cohort study between September 2013 and April 2017. Dietary intake was assessed using a validated 79-item food frequency questionnaire. Cox proportional hazard regression models were utilized to calculate hazard ratios (HRs) and 95% confidence intervals (CIs) for the overall and HCC-specific mortality. During a median of 791 days of follow-up, we documented 395 deaths, 353 (89%) of which resulted from HCC. The multivariate-adjusted HRs in the highest vs. the lowest quartile of methionine intake were 0.59 (95% CI: 0.42-0.80; P for trend = 0.001) for overall mortality and 0.68 (95% CI: 0.49-0.93; P for trend = 0.027) for HCC-specific mortality. However, no significant association of other micronutrients involved in one-carbon metabolism with HCC survival was observed. Our research suggests that a high level of methionine intake, but no other one-carbon metabolism-related nutrients, may improve survival in patients with newly diagnosed HCC.

Association of dietary intakes of vitamin B12, vitamin B6, folate, and methionine with the risk of esophageal cancer: the Japan Public Health Center-based (JPHC) prospective study

BackgroundB vitamins and methionine are essential substrates in the one-carbon metabolism pathway involved in DNA synthesis and methylation. They may have essential roles in cancer development. We aimed to evaluate the associations of dietary intakes of vitamin B12, vitamin B6, folate, and methionine with the risk of esophageal cancer (EC) using data from the Japan Public Health Center-based Prospective Study.MethodsWe included 87,053 Japanese individuals who completed a food frequency questionnaire and were followed up from 1995–1998 to 2013 and 2015. Hazard ratios (HRs) and 95% confidence intervals (CIs) were calculated by Cox proportional-hazard regression across quintiles of dietary intakes of B vitamins and methionine.ResultsAfter 1,456,678 person-years of follow-up, 427 EC cases were documented. The multivariable HR (95% CI) of incident EC in the highest versus lowest quintile of dietary intake of vitamin B12 was 1.75 (1.13–2.71; p-trend=0.01). Stratification analysis based on alcohol consumption showed that higher dietary intakes of vitamin B12 and methionine were associated with an increased risk of EC among never-drinkers; HRs (95% CIs) were 2.82 (1.18–6.74; p-trend=0.009; p-interaction=0.18) and 3.45 (1.32–9.06; p-trend=0.003; p-interaction 0.02) for vitamin B12 and methionine, respectively. Meanwhile, there was no association between vitamin B12 and methionine intake with the risk of EC among drinkers. There were no associations between dietary intake of folate or vitamin B6 and the risk of EC.ConclusionDietary intake of vitamin B12 was positively associated with the risk of EC in the Japanese population.

Exploiting the metabolic dependencies of the broad amino acid transporter SLC6A14

Tumor cells typically enhance their metabolic capacity to sustain their higher rate of growth and proliferation. One way to elevate the nutrient intake into cancer cells is to increase the expression of genes encoding amino acid transporters, which may represent targetable vulnerabilities. Here, we study the regulation and function of the broad amino acid transporter SLC6A14 in combination with metabolic stress, providing insights into an uncharacterized aspect of the transporter activity. We analyze the pattern of transcriptional changes in a panel of breast cancer cell lines upon metabolic stress and found that SLC6A14 expression levels are increased in the absence of methionine. Methionine deprivation, which can be achieved via modulation of dietary methionine intake in tumor cells, in turn leads to a heightened activation of the AMP-activated kinase (AMPK) in SLC6A14-deficient cells. While SLC6A14 genetic deficiency does not have a major impact on cell proliferation, combined depletion of AMPK and SLC6A14 leads to an increase in apoptosis upon methionine starvation, suggesting that combined targeting of SLC6A14 and AMPK can be exploited as a therapeutic approach to starve tumor cells.

Lessons Learned from Inherited Metabolic Disorders of Sulfur-Containing Amino Acids Metabolism

The metabolism of sulfur-containing amino acids (SAAs) requires an orchestrated interplay among several dozen enzymes and transporters, and an adequate dietary intake of methionine (Met), cysteine (Cys), and B vitamins. Known human genetic disorders are due to defects in Met demethylation, homocysteine (Hcy) remethylation, or cobalamin and folate metabolism, in Hcy transsulfuration, and Cys and hydrogen sulfide (H2S) catabolism. These disorders may manifest between the newborn period and late adulthood by a combination of neuropsychiatric abnormalities, thromboembolism, megaloblastic anemia, hepatopathy, myopathy, and bone and connective tissue abnormalities. Biochemical features include metabolite deficiencies (e.g. Met, S-adenosylmethionine (AdoMet), intermediates in 1-carbon metabolism, Cys, or glutathione) and/or their accumulation (e.g. S-adenosylhomocysteine, Hcy, H2S, or sulfite). Treatment should be started as early as possible and may include a low-protein/low-Met diet with Cys-enriched amino acid supplements, pharmacological doses of B vitamins, betaine to stimulate Hcy remethylation, the provision of N-acetylcysteine or AdoMet, or experimental approaches such as liver transplantation or enzyme replacement therapy. In several disorders, patients are exposed to long-term markedly elevated Met concentrations. Although these conditions may inform on Met toxicity, interpretation is difficult due to the presence of additional metabolic changes. Two disorders seem to exhibit Met-associated toxicity in the brain. An increased risk of demyelination in patients with Met adenosyltransferase I/III (MATI/III) deficiency due to biallelic mutations in the MATIA gene has been attributed to very high blood Met concentrations (typically >800μmol/L) and possibly also to decreased liver AdoMet synthesis. An excessively high Met concentration in some patients with cystathionine β-synthase deficiency has been associated with encephalopathy and brain edema, and direct toxicity of Met has been postulated. In summary, studies in patients with various disorders of SAA metabolism showed complex metabolic changes with distant cellular consequences, most of which are not attributable to direct Met toxicity.

Interplay of Enzyme Therapy and Dietary Management of Murine Homocystinuria.

Albeit effective, methionine/protein restriction in the management of classical homocystinuria (HCU) is suboptimal and hard to follow. To address unmet need, we developed an enzyme therapy (OT-58), which effectively corrected disease symptoms in various mouse models of HCU in the absence of methionine restriction. Here we evaluated short- and long-term efficacy of OT-58 on the background of current dietary management of HCU. Methionine restriction resulted in the lowering of total homocysteine (tHcy) by 38–63% directly proportional to a decreased methionine intake (50–12.5% of normal). Supplemental betaine resulted in additional lowering of tHcy. OT-58 successfully competed with betaine and normalized tHcy on the background of reduced methionine intake, while substantially lowering tHcy in mice on normal methionine intake. Betaine was less effective in lowering tHcy on the background of normal or increased methionine intake, while exacerbating hypermethioninemia. OT-58 markedly reduced both hyperhomocysteinemia and hypermethioninemia caused by the diets and betaine in HCU mice. Withdrawal of betaine did not affect improved metabolic balance, which was established and solely maintained by OT-58 during periods of fluctuating dietary methionine intake. Taken together, OT-58 may represent novel, highly effective enzyme therapy for HCU performing optimally in the presence or absence of dietary management of HCU.

Hypermethioninemia Leads to Fatal Bleeding and Increased Mortality in a Transgenic I278T Mouse Model of Homocystinuria.

Severely elevated plasma homocysteine and methionine lead to thromboembolic events and strokes in homocystinuric (HCU) patients. Mouse models of HCU failed to exhibit prothrombotic phenotype, presumably due to lack of hypermethioninemia. We evaluated the impact of hypermethioninemia together with hyperhomocysteinemia on murine HCU phenotype and compared the efficacy of the current and novel therapies for HCU. High methionine intake decreased survival of I278T mice, which died from intestinal bleeding with hepatic and pancreatic failure. I278T mice on normal or increased methionine intake developed endothelial dysfunction, but paradoxically demonstrated delayed occlusion in an induced arterial thrombosis model. RNA-seq analysis suggested that expression of coagulation factor XI (FXI) is downregulated in livers of I278T mice. Indeed, plasma concentrations of FXI were decreased in I278T mice on normal diet and further reduced by increased methionine intake. Dietary methionine restriction normalized the observed phenotype. Similarly, treatment with OT-58, a novel enzyme therapy for HCU, corrected the phenotype in I278T mice regardless of their dietary methionine intake. Hypermethioninemia does not contribute to prothrombotic phenotype in murine HCU. Downregulation of FXI may contribute to the lack of prothrombotic tendency in I278T mice. Methionine restriction or treatment with OT-58 corrects vascular disease in the I278T mouse model of HCU.

Cystathionine beta synthase deficiency and brain edema associated with methionine excess under betaine supplementation: Four new cases and a review of the evidence

CBS deficient individuals undergoing betaine supplementation without sufficient dietary methionine restriction can develop severe hypermethioninemia and brain edema. Brain edema has also been observed in individuals with severe hypermethioninemia without concomitant betaine supplementation. We systematically evaluated reports from 11 published and 4 unpublished patients with CBS deficiency and from additional four cases of encephalopathy in association with elevated methionine. We conclude that, while betaine supplementation does greatly exacerbate methionine accumulation, the primary agent causing brain edema is methionine rather than betaine. Clinical signs of increased intracranial pressure have not been seen in patients with plasma methionine levels below 559 μmol/L but occurred in one patient whose levels did not knowingly exceed 972 μmol/L at the time of manifestation. While levels below 500 μmol/L can be deemed safe it appears that brain edema can develop with plasma methionine levels close to 1000 μmol/L. Patients with CBS deficiency on betaine supplementation need to be regularly monitored for concordance with their dietary plan and for plasma methionine concentrations. Recurrent methionine levels above 500 μmol/L should alert clinicians to check for clinical signs and symptoms of brain edema and review dietary methionine intake. Levels approaching 1000 μmol/L do increase the risk of complications and levels exceeding 1000 μmol/L, despite best dietetic efforts, should be acutely addressed by reducing the prescribed betaine dose.

Methyl Donor Nutrient Intake and Risk of Type 2 Diabetes: Results from 3 Large US Cohorts (OR15-02-19)

ObjectivesDNA methylation may play a role in the development of type 2 diabetes (T2D). DNA methylation can be influenced by methyl donor nutrients such as vitamins B2, B6, B12, folate, and methionine, which are all central to one carbon metabolism. Using 3 large cohorts of US health professionals, we examined whether intake of these nutrients from food or supplements is associated with T2D risk. MethodsWe included 69,949 women from the Nurses’ Health Study (1984–2012), 90,239 women from the Nurses’ Health Study II (1991–2011), and 40,539 men from the Health Professionals Follow-Up Study (1986–2010). Dietary data were collected every 2–4 years using a validated semi-quantitative FFQ, from which dietary intakes of vitamin B2, vitamin B6, vitamin B12, folate, and methionine were calculated. We used Cox proportional hazards model with time-varying covariates and adjusted for several sociodemographic and lifestyle variables. We also adjusted for cereal fiber, animal protein, polyunsaturated and saturated fatty acids ratio. Food sources of vitamins were additionally adjusted for multivitamin use while supplemental sources of vitamins were adjusted for a measure of overall diet quality. ResultsDuring 1763,428 years of follow-up, we documented 8141 T2D cases. In pooled multivariable-adjusted analyses, compared to those in the lowest quintile, those in the highest quintile of vitamins B2 and B6 had a 10% (95% CI 3%–16%) and 11% (95% CI 3%–16%) lower T2D risk, respectively. Total vitamin B12 intake was not associated with T2D. However, when analyses were stratified by source, vitamin B12 from food sources was associated with a higher T2D risk (HR [95% CI] = 1.11 [1.02–1.19]). On the other hand, supplemental vitamin B12 was associated with lower T2D risk (HR [95% CI] for Q5 vs Q1 = 0.92 [0.85–0.98]). We found no evidence for an association between intakes of folate and methionine and T2D risk. ConclusionsOur study suggests that higher intakes of vitamin B2 and vitamin B6 are associated with a lower T2D risk. A higher vitamin B12 intake from food seems to be associated with a higher T2D risk, which may be due to consumption of animal products. Funding SourcesThe analysis was supported by grants from the National Institutes of Health.

Modulation of dietary methionine intake elicits potent, yet distinct, anticancer effects on primary versus metastatic tumors

Methionine dependency describes the characteristic rapid in vitro death of most tumor cells in the absence of methionine. Combining chemotherapy with dietary methionine deprivation [methionine-deficient diet (MDD)] at tolerable levels has vast potential in tumor treatment; however, it is limited by MDD-induced toxicity during extended deprivation. Recent advances in imaging and irradiation delivery have created the field of stereotactic body radiotherapy (SBRT), where fewer large-dose fractions delivered in less time result in increased local-tumor control, which could be maximally synergistic with an MDD short course. Identification of the lowest effective methionine dietary intake not associated with toxicity will further enhance the cancer therapy potential. In this study, we investigated the effects of MDD and methionine-restricted diet (MRD) in primary and metastatic melanoma models in combination with radiotherapy (RT). In vitro, MDD dose-dependently sensitized mouse and human melanoma cell lines to RT. In vivo in mice, MDD substantially potentiated the effects of RT by a significant delay in tumor growth, in comparison with administering MDD or RT alone. The antitumor effects of an MDD/RT approach were due to effects on one-carbon metabolism, resulting in impaired methionine biotransformation via downregulation of Mat2a, which encodes methionine adenosyltransferase 2A. Furthermore, and probably most importantly, MDD and MRD substantially diminished metastatic potential; the antitumor MRD effects were not associated with toxicity to normal tissue. Our findings suggest that modulation of methionine intake holds substantial promise for use with short-course SBRT for cancer treatment.