Homocysteine methionine. Medical search. Frequent questions

The mRNA expression of methionine synthase was significantly increased after methionine or methionine plus quercetin supplementation, while its enzymatic activity was significantly increased after methionine plus quercetin supplementation. (hindawi.com)
The mRNA expression and enzymatic activity of cystathionine β -synthase and cystathionine γ -lyase were upregulated after quercetin, methionine, or quercetin plus methionine treatment and a more significant increase was observed for hepatic cystathionine β -synthase in the methionine plus quercetin treated rats, suggesting an interaction between methionine and quercetin. (hindawi.com)
In remethylation pathway, Hcy can be remethylated to form Met via methionine synthase (MS) or betaine-homocysteine methyltransferase (BHMT), in which cofactors such as folic acid and vitamin B 12 or betaine are required. (hindawi.com)
Variants in the CBS gene disrupt the function of cystathionine beta-synthase, preventing homocysteine from being used properly. (medlineplus.gov)
Remethylation requires 5, 10-methylenetetrahydrofolate reductase and methionine synthase. (bmj.com)
The underlying enzymological abnormality, a deficit of cystathionine β synthase, results in impairment of homocysteine transsulfuration. (bmj.com)
Vitamin B12 acts as a coenzyme for methionine synthase, which produces methionine from homocysteine. (theepochtimes.com)
MeCbl is also a cofactor, but for an enzyme known as methionine synthase. (medlineplus.gov)
Because both of these cofactors are missing, the enzymes that require them (methylmalonyl CoA mutase and methionine synthase) do not function normally. (medlineplus.gov)
Vitamin B12 functions as a cofactor for two enzymes, methionine synthase and L-methylmalonyl-CoA mutase [ 1-3 , 5 ]. (nih.gov)
Methionine synthase catalyzes the conversion of homocysteine to the essential amino acid methionine [ 1 , 2 ]. (nih.gov)
deficiency of cystathionine beta-synthase, which catalyzes cystathionine formation from homocysteine and serine. (msdmanuals.com)
Plasma homocysteine levels are usually severely elevated in homozygous cystathionine-β synthase deficiency and moderately elevated in heterozygous cystathionine-β synthase deficiency. (medscape.com)

It is synthesized from ATP and methionine by S-Adenosylmethionine synthetase enzyme through the following reaction: ATP + L-methionine + H2O ⇌ {\displaystyle \rightleftharpoons } phosphate + diphosphate + S-adenosyl-L-methionine The sulfonium functional group present in S-adenosyl methionine is the center of its peculiar reactivity. (wikipedia.org)
Depending on the enzyme, S-adenosyl methionine can be converted into one of three products: adenosyl radical, which converts to deoxyadenosine (AdO): classic rSAM reaction, also cogenerates methionine S-adenosyl homocysteine, releasing methyl radical methylthioadenosine (SMT), homoalanine radical The reactions that produce, consume, and regenerate SAM are called the SAM cycle. (wikipedia.org)
This enzyme helps break down the amino acid methionine. (medlineplus.gov)
This enzyme converts the amino acid homocysteine to another amino acid, methionine. (medlineplus.gov)
The build up of homocysteine causes the formation of homocysteine thiolactone made from methionine in the liver by an enzyme that participates in protein formation and other processes. (healthy.net)
Vitamin B12 (B12) is an essential cofactor for two enzymes involved in one-carbon metabolism: methylmalonyl CoA mutase (reduced function of this enzyme results in increased serum methylmalonic acid (MMA) levels) and methionine synthetase (this enzyme catalyzes the remethylmation of homocysteine to methionine) (IOM 1998). (cdc.gov)
this conversion requires the enzyme methionine adenosyltransferase. (msdmanuals.com)

In most cases, vitamin B-12 deficiency is associated with an elevation in plasma homocysteine and methylmalonic acid levels, whereas folate deficiency is associated with elevated homocysteine levels only. (medscape.com)

The conversion of homocysteine to methionine is controlled by vitamin B12 and folic acid, which remethylate homocysteine to methionine. (healthy.net)
B vitamins control homocysteine levels by stimulating the conversion of homocysteine to methionine. (fatsoflife.com)

In bacteria, SAM is bound by the SAM riboswitch, which regulates genes involved in methionine or cysteine biosynthesis. (wikipedia.org)
The methionine metabolism cycle (MMC) plays important roles in regulating both methionine and cysteine homeostasis [ 1 ], and is related with functions in terms of cell growth and development under normal conditions [ 2 , 3 ]. (biomedcentral.com)
As a universal key intermediate in the MMC, homocysteine is not obtained from the diet, but is remethylated to methionine, or converted to cysteine by the trans-sulfuration pathway. (biomedcentral.com)
in plasma, it undergoes oxidization and transforms to disulfides homocystine and cysteine-homocysteine, the measured plasma level reflects these 3 components. (medscape.com)

It is concluded that quercetin reduces serum homocysteine by increasing remethylation and transsulfuration of homocysteine in rats exposed to a methionine-enriched diet. (hindawi.com)
S-Adenosyl methionine (SAM), also known under the commercial names of SAMe, SAM-e, or AdoMet, is a common cosubstrate involved in methyl group transfers, transsulfuration, and aminopropylation. (wikipedia.org)
Various defects in remethylation or transsulfuration can cause homocysteine to accumulate, resulting in disease. (msdmanuals.com)

Folic acid, together with vitamins B 6 and B 12 , helps break down homocysteine, and may help reverse the problems associated with elevated levels. (encyclopedia.com)
Whether or not your homocysteine levels are elevated depends upon the total methionine content of dietary protein and the amount of vitamin B6, B12 and folic acid in your diet. (healthy.net)
But with the help of several B vitamins (B6, B12 and folic acid), our bodies convert homocysteine into glutathione, a valuable antioxidant, or "remethylate" it back into methionine. (healthyplace.com)
Plasma homocysteine levels are elevated in vitamin B-12 deficiency, vitamin B-6 deficiency and in folic acid deficiency. (medscape.com)

Association of Long-term Exposure to Air Pollution and Dementia Risk: The Role of Homocysteine, Methionine, and Cardiovascular Burden. (bvsalud.org)
We investigated the role played by homocysteine (tHcy) and methionine in this association and explored whether this could be explained by cardiovascular diseases (CVDs). (bvsalud.org)
Elevated homocysteine is also a risk factor for cardiovascular disease. (theepochtimes.com)
High levels of circulating homocysteine are associated with an increased risk of cardiovascular disease . (oregonstate.edu)
However, homocysteine lowering by B vitamins has failed to lower the risk of adverse cardiovascular outcomes in high-risk individuals. (oregonstate.edu)
Homocysteine, generated in the metabolism of methionine, may have a role in the development of cardiovascular disease. (unboundmedicine.com)
Methylation, also, protects against the dangerous homocysteine molecule that can build up in people's blood stream and cause cardiovascular diseaes. (healthy-living.org)
The primary such as hs-CRP, total homocysteine, as well enzymatic defences are intracellular, but as oxidative stress, have been proposed other antioxidant defences are largely ex- as risk factors for the development and tracellular, including antioxidative sub- progression of atherosclerosis and athero- strates such as uric acid and unconjugated thrombotic cardiovascular disease [10-13]. (who.int)
Whether elevated plasma and urine homocysteine levels represent a cardiovascular risk factor is debatable. (medscape.com)

Betaine supplementation has a lowering effect on post-methionine load tHcy. (nih.gov)
The data shown that plasma homocysteine levels both basal and post-methionine load were significantly higher in the two groups of demented patients than in the control group. (unicatt.it)

Betaine is a significant determinant of plasma tHcy, particularly in case of folate deficiency, methionine load, or alcohol consumption. (nih.gov)
Recent studies in test tubes brings into question whether there is a connection between elevated homocysteine (and, therefore, folate deficiency) in the mother and Down's syndrome in the child. (healthyplace.com)

Deficiency in B12 (or folate) results in the accumulation of homocysteine. (theepochtimes.com)
A number of defects in methionine metabolism lead to accumulation of homocysteine (and its dimer, homocystine) with adverse effects including thrombotic tendency, lens dislocation, and central nervous system and skeletal abnormalities. (msdmanuals.com)

Changes in plasma concentrations of total homocysteine (tHcy) reflect one aspect of the metabolic consequences of methyl group deficiency or nutrient supplementations. (nih.gov)
a serum homocysteine level higher than 15 micromol/L, for example, suggests vitamin B12 deficiency [ 11 ]. (nih.gov)

People who have this disorder should not take methionine supplements because methionine might cause homocysteine to build up in these people. (rxlist.com)

Using the methionine loading test, in which 0.1 mg/kg body weight of this amino acid is administered orally, they found that the prevalence of high circulating homocysteine concentrations, or hyperhomocysteinaemia, was higher than in normal controls. (bmj.com)

An alternative remethylation pathway also exists using the cobalamin independent betaine-homocysteine methyltransferase. (bmj.com)
Disorders of cobalamin (vitamin B 12 )/propionate/homocysteine metabolism result from defects in the vitamin B 12 metabolic pathway. (arupconsult.com)
Molecular testing is used to confirm suspected cobalamin/propionate/homocysteine metabolism-related disorders in individuals with clinical symptoms and/or biochemical findings. (arupconsult.com)
Pathogenic germline variants in genes associated with the cobalamin metabolic pathway cause disorders of cobalamin (vitamin B 12 )/propionate/homocysteine metabolism. (arupconsult.com)
MTHFR polymorphisms and serum cobalamin affect plasma homocysteine concentrations differentially in females and males. (medscape.com)
Pirouzpanah S, Taleban FA, Mehdipour P, Atri M, Foroutan-Ghaznavi M. Plasma Total Homocysteine Level in Association With Folate, Pyridoxine, and Cobalamin Status Among Iranian Primary Breast Cancer Patients. (medscape.com)

Conversion of S-adenosyl-L-homocysteine (SAH) to homocysteine increased and the metabolism of homocysteine was reduced under diabetic conditions, and consequently homocysteine accumulated in the elimination phase. (biomedcentral.com)
Pathways for the metabolism of homocysteine. (bmj.com)

Under the catalysis of methionine adenosyltransferase, Met is converted to S-adenosylmethionine (SAM), which is an important methyl donor in vivo . (hindawi.com)
It is made from adenosine triphosphate (ATP) and methionine by methionine adenosyltransferase. (wikipedia.org)

Serum homocysteine was significantly increased after methionine treatment and decreased after the addition of quercetin. (hindawi.com)

The aim of the current study was to predict changes in plasma methionine and homocysteine concentrations after simulated consumption of methionine-rich foods, following the development of a mathematical model for MMC in Zucker Diabetic Fatty (ZDF) rats, as a representative T2DM animal model. (biomedcentral.com)
Using our model, we performed simulations to compare the changes in plasma methionine and homocysteine concentrations between ZDF and normal rats, by multiple administrations of the methionine-rich diet of 1 mmol/kg, daily for 60 days. (biomedcentral.com)

This study was aimed at investigating the effects of quercetin on mRNA expression and activity of critical enzymes in homocysteine metabolism in rats fed a methionine-enriched diet. (hindawi.com)
The enzymes made by the MTHFR , MTR , MTRR , and MMADHC genes play roles in converting homocysteine to methionine. (medlineplus.gov)
Variants in any of these genes prevent the enzymes from functioning properly, which leads to a buildup of homocysteine in the body. (medlineplus.gov)
Even where diagnosed by history, medical examina- hyper homocysteinaemia is a well estab- tion, electrocardiogram, echocardiogram lished risk factor, we do not know the exact and blood tests, including enzymes (tro- mechanism whereby high homocysteine ponin T and creatine phosphokinase). (who.int)

Methionine can increase blood levels of a chemical called homocysteine, especially in people who don't have enough folate, vitamin B12 , or vitamin B6 in their bodies, or in people whose bodies have trouble processing homocysteine. (rxlist.com)
Predictive value of folate, vitamin B12 and homocysteine. (cambridge.org)

Researchers have not determined how excess homocysteine and related compounds lead to the signs and symptoms of homocystinuria. (medlineplus.gov)
The body uses methionine to make proteins and other important compounds. (medlineplus.gov)
This dual defect results in a buildup of toxic compounds, including homocysteine, and a decrease in the production of methionine within the body. (medlineplus.gov)

The aim of the study is to compare the basal homocysteine levels in patients with impairment of cognitive status, and in controls, to evaluate if the methionine loading test is able to identify any differences between patients with Alzheimers disease and patients with vascular dementia. (unicatt.it)
Although alterations in the methionine metabolism cycle (MMC) have been associated with vascular complications of diabetes, there have not been consistent results about the levels of methionine and homocysteine in type 2 diabetes mellitus (T2DM). (biomedcentral.com)
The levels of methionine and homocysteine were elevated approximately two- and three-fold, respectively, in ZDF rats, while there were no changes observed in the normal control rats. (biomedcentral.com)
To verify this hypothesis, mathematical modeling of methionine metabolism was required to predict the levels of homocysteine derived from given amounts of methionine. (biomedcentral.com)
Methionine can increase blood levels of homocysteine , a chemical that might cause heart disease . (rxlist.com)
The role of folate, vitamin B 12 and homocysteine levels in depression is not clear. (cambridge.org)
To investigate cross-sectional and prospective associations between folate, B 12 and homocysteine levels and late-life depression. (cambridge.org)
Serum folate, serum vitamin B 12 and plasma homocysteine levels were assayed at both baseline and follow-up. (cambridge.org)
Lower levels of folate and vitamin B 12 and higher homocysteine levels at baseline were associated with a higher risk of incident depression at follow-up. (cambridge.org)
Incident depression was associated with a decline in vitamin B 12 and an increase in homocysteine levels over the follow-up period. (cambridge.org)
Lower folate, lower vitamin B 12 and raised homocysteine levels may be risk factors for late-life depression. (cambridge.org)
Randomized controlled trials have demonstrated that supplementation with B vitamins, including vitamin B 6 , could effectively reduce homocysteine levels. (oregonstate.edu)
Vitamin B9 works closely with vitamins B6 and B12 as well as the nutrients betaine and S-adenosylmethionine (SAMe) to control blood levels of the amino acid homocysteine. (healthyplace.com)
When our cells are well stocked with B vitamins, the brisk pace of methylation keeps homocysteine levels low. (healthyplace.com)
Of interest, the VITACOG trial revealed that the efficacy of the B vitamins in lowering cognitive decline was better in people with higher levels of homocysteine . (fatsoflife.com)
Plasma homocysteine levels can be elevated in vitamin B-12, folate (vitamin B-9), and vitamin B-6 deficiencies. (medscape.com)
Zhang F, Li X, Dong Q, Wang Y, Zhang H. Risk of Acute Cerebral Infarction and Plasma Asymmetrical Dimethylarginine and Homocysteine Levels: A Clinical Correlation Analysis of Chinese Population. (medscape.com)

Animal proteins, and particularly those from egg whites, are high in the troublesome, sulfur-containing amino acids, such as methionine. (drmcdougall.com)
whereas normal cells can grow on a methionine-free diet (feeding off other sulfur-containing amino acids). (drmcdougall.com)
As a result, certain amino acids, fatty acids, and cholesterol are not broken down and homocysteine cannot be converted to methionine. (medlineplus.gov)
Methione molecules are beneficial amino acids that in turn become mood enhancing SAMe (S-adenosyl-L-methionine) molecules. (healthy-living.org)
Defects in Metabolism of Amino Acids, Methionine. (medscape.com)

Thus, 0we hypothesized that long-term administration of a high-methionine diet to T2DM rats with normal renal function may create metabolic changes, culminating in an elevated level of circulating homocysteine. (biomedcentral.com)
It is an intermediate in the metabolic pathway of methionine. (ebi.ac.uk)
Homocysteine is actually a by product of certain normal metabolic amino acid breakdown and processing. (ecopolitan.com)
Homocysteine play an important role in many metabolic pathways, mainly the methionine cycle to the folate cycle (see image below). (medscape.com)
simplified picture, showing Homocysteine involvement in different metabolic pathways as well as the role of vitamin B6, B12 and Folate as a co-factor in this pathways. (medscape.com)
Caption: Homocysteine involvement in different metabolic pathways, as well as the role of vitamin B-6, vitamin B-12, and folate as cofactors in these pathways. (medscape.com)

Meanwhile, hepatic ratio of S-adenosylmethionine to S-adenosylhomocysteine was significantly decreased in response to methionine supplementation and normalized after the addition of quercetin. (hindawi.com)

Folate, vitamin B 12 , homocysteine and methylenetetrahydrofolate reductase (MTHFR) are involved in one-carbon transfer (methylation) reactions necessary for the production of monoamine neurotransmitters, phospholipids and nucleotides. (cambridge.org)

Even if the methionine loading test revealed an abnormal homocysteine metabolism in demented patients, it didnt show any difference among patients with Alzheimers disease and vascular dementia. (unicatt.it)
About 10 years after the discovery of homocystinuria it was hypothesised by McCully 4 that high plasma homocysteine might be causally related to the vascular complications of the disease. (bmj.com)
Homocysteine is a known risk factor for vascular damage and associated with hypoperfusion of the neocortex and atrophy of the medial temporal lobe in AD patients. (fatsoflife.com)

Because remethylation is intact, some of the additional homocysteine is converted to methionine, which accumulates in the blood. (msdmanuals.com)

These results can be interpreted to mean that both methionine and homocysteine will accumulate in patients with T2DM, who regularly consume high-methionine foods. (biomedcentral.com)

Some of the excess homocysteine is excreted in urine. (medlineplus.gov)

Low dietary choline loweres methionine formation and causes a marked increase in S-adenosylmethionine utilization in the liver. (nih.gov)
Women who consume more dietary methionine during pregnancy seem to have a lower risk of neural tube birth defects. (rxlist.com)

A sulfonium compound that is the S -adenosyl derivative of L -methionine. (ebi.ac.uk)

Homocysteine accumulates and dimerizes to form the disulfide homocystine, which is excreted in the urine. (msdmanuals.com)
Plasma and urine homocysteine tests are indicated in the screening and diagnosis of different types of homocystinuria. (medscape.com)
The reference range of urine homocysteine (24-hour urine collection) varies with the technique used, from 0-9 µmol/g creatinine. (medscape.com)

It is POSSIBLY UNSAFE to self-medicate with methionine if you use larger amounts than those typically found in food. (rxlist.com)
When excessive amounts of homocysteine build up, it can damage blood vessels and lead to heart problems. (medicalnewstoday.com)

1 By receiving a methyl group from 5′-methyltetrahydrofolate, it is reconverted to methionine (fig 1), which is essential for many biochemical reactions critical to the formation of protein, nucleic acids, and creatinine. (bmj.com)
Our bodies make SAMe from methionine, an amino acid found in protein-rich foods, then continually recycle it. (healthyplace.com)

Methylation changes homocysteine molecules into methionine molecules. (healthy-living.org)

Methionine is used to prevent liver damage in acetaminophen ( Tylenol ) poisoning . (rxlist.com)
In acetaminophen poisoning, methionine prevents the breakdown products of acetaminophen from damaging the liver. (rxlist.com)
Methionine might make liver disease worse. (rxlist.com)
When LDL homocysteine thiolactone aggregates are released from the blood into the liver, they are taken up by the macrophages of the artery walls to form the foam cells that are seen in early arteriosclerotic plaques.These foam cells then degrade these aggregates and release fat and cholesterol into the developing plaques. (healthy.net)

The reference range of plasma homocysteine may vary with the technique used. (medscape.com)

Rats were fed for 6 weeks the following diets, that is, control, 0.5% quercetin, 1.0% methionine, and 1.0% methionine plus 0.5% quercetin diets. (hindawi.com)

In the first step of this cycle, the SAM-dependent methylases (EC 2.1.1) that use SAM as a substrate produce S-adenosyl homocysteine as a product. (wikipedia.org)

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