|
Methylenetetrahydrofolate Reductase Deficiency
Methylenetetrahydrofolate reductase deficiency is the most common genetic cause of elevated serum levels of homocysteine (hyperhomocysteinemia). It is caused by genetic defects in MTHFR, which is an important enzyme in the methyl cycle. Common variants of MTHFR deficiency are asymptomatic and have only minor effects on disease risk. Severe variants (from nonsense mutations) are rare. Symptoms and signs The common MTHFR deficiencies are usually asymptomatic, although the 677T variant can cause a mildly increased risk of some diseases. For individuals homozygous in the 677T variant, there is a mildly elevated risk of thromboembolism (odds ratio 1.2), and stroke (odds ratio 1.26). There is also an elevated risk of neural tube defects among children of individuals with the C677T polymorphism (odds ratio 1.38). Common MTHFR deficiencies were once thought to be associated with cardiovascular risk, but meta-analyses indicate that correlation this was an artifact of publication bias. ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Homocysteine
Homocysteine (; symbol Hcy) is a non-proteinogenic α-amino acid. It is a homologous series, homologue of the amino acid cysteine, differing by an additional methylene bridge (). It is biosynthesized from methionine by the removal of its terminal Cε methyl group. In the body, homocysteine can be recycled into methionine or converted into cysteine with the aid of Vitamin B6, vitamin B6, Folate, B9, and Vitamin B12, B12. High levels of homocysteine in the blood (hyperhomocysteinemia) is regarded as a marker of cardiovascular disease, likely working through atherogenesis, which can result in Ischemia, ischemic injury. Therefore, hyperhomocysteinemia is a possible risk factor for coronary artery disease. Coronary artery disease occurs when an atherosclerotic plaque blocks blood flow to the Coronary artery, coronary arteries, which supply the heart with oxygenated blood. Hyperhomocysteinemia has been correlated with the occurrence of blood clots, heart attacks, and strokes, although ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
5-methyltetrahydrofolate
Levomefolic acid (INN, also known as L-5-MTHF, L-methylfolate and L-5-methyltetrahydrofolate and (6''S'')-5-methyltetrahydrofolate, and (6''S'')-5-MTHF) is the primary biologically active form of folate used at the cellular level for DNA reproduction, the cysteine cycle and the regulation of homocysteine. It is also the form found in circulation and transported across membranes into tissues and across the blood–brain barrier. In the cell, L-methylfolate is used in the methylation of homocysteine to form methionine and tetrahydrofolate (THF). THF is the immediate acceptor of one carbon unit for the synthesis of thymidine-DNA, purines (RNA and DNA) and methionine. The un-methylated form, folic acid (vitamin B9), is a synthetic form of folate, and must undergo enzymatic reduction by dihydrofolate reductase ( DHFR) to become biologically active. Systematic reviews suggest that adjunctive L-methylfolate modestly improves symptoms in major depressive disorder. It is synthesized in the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
DNA Methylation
DNA methylation is a biological process by which methyl groups are added to the DNA molecule. Methylation can change the activity of a DNA segment without changing the sequence. When located in a gene promoter (genetics), promoter, DNA methylation typically acts to repress gene Transcription (genetics), transcription. In mammals, DNA methylation is essential for normal development and is associated with a number of key processes including genomic imprinting, X-chromosome inactivation, repression of transposable elements, aging, and carcinogenesis. As of 2016, two nucleobases have been found on which natural, enzymatic DNA methylation takes place: adenine and cytosine. The modified bases are N6-methyladenine,D. B. Dunn, J. D. Smith: "The occurrence of 6-methylaminopurine in deoxyribonucleic acids". In: ''Biochem J.'' 68(4), Apr 1958, S. 627–636. [//www.ncbi.nlm.nih.gov/pubmed/13522672?dopt=Abstract PMID 13522672]. . 5-methylcytosineB. F. Vanyushin, S. G. Tkacheva, A. N. Belozers ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cystathionine Beta Synthase
Cystathionine-β-synthase, also known as CBS, is an enzyme () that in humans is encoded by the ''CBS'' gene. It catalyzes the first step of the transsulfuration pathway, from homocysteine to cystathionine: : L-serine + L-homocysteine \rightleftharpoons L-cystathionine + H2O CBS uses the cofactor pyridoxal-phosphate (PLP) and can be allosterically regulated by effectors such as the ubiquitous cofactor ''S''-adenosyl-L-methionine (adoMet). This enzyme belongs to the family of lyases, to be specific, the hydro-lyases, which cleave carbon-oxygen bonds. CBS is a multidomain enzyme composed of an N-terminal enzymatic domain and two CBS domains. The ''CBS'' gene is the most common locus for mutations associated with homocystinuria. Nomenclature The systematic name of this enzyme class is L-serine hydro-lyase (adding homocysteine; L-cystathionine-forming). Other names in common use include: * β-thionase, * cysteine synthase, * L-serine hydro-lyase (adding homocysteine), * ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Homocystinuria
Homocystinuria (HCU) is an inherited disorder of the metabolism of the amino acid methionine due to a deficiency of cystathionine beta synthase or methionine synthase. It is an inherited autosomal recessive trait, which means a child needs to inherit a copy of the defective gene from both parents to be affected. Symptoms of homocystinuria can also be caused by a deficiency of vitamins B6, B12, or folate. Signs and symptoms This defect leads to a multi-systemic disorder of the connective tissue, muscles, central nervous system (CNS), and cardiovascular system. Homocystinuria represents a group of hereditary metabolic disorders characterized by an accumulation of the amino acid homocysteine in the serum and an increased excretion of homocysteine in the urine. Infants appear to be normal and early symptoms, if any are present, are vague. Signs and symptoms of homocystinuria that may be seen include the following: Cause It is usually caused by the deficiency of the enzyme cyst ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hyperhomocysteinemia
Hyperhomocysteinemia is a medical condition characterized by an abnormally high level of total homocysteine (that is, including homocystine and homocysteine-cysteine disulfide) in the blood, conventionally described as above 15 μmol/L. As a consequence of the biochemical reactions in which homocysteine is involved, deficiencies of vitamin B6, folic acid (vitamin B9), and vitamin B12 can lead to high homocysteine levels. Other possible causes of hyperhomocysteinemia include genetics, excessive methionine intake, and other diseases. Hyperhomocysteinemia is typically managed with vitamin B6, vitamin B9 and vitamin B12 supplementation. Hyperhomocysteinemia is a risk factor for cardiovascular disease; supplements of these vitamins may slightly reduce stroke outcome but not myocardial infarction, death from any cause or adverse events. Signs and symptoms Elevated levels of homocysteine have been associated with a number of disease states: more than 100 adverse outcomes have ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
5-MTHF
Levomefolic acid ( INN, also known as L-5-MTHF, L-methylfolate and L-5-methyltetrahydrofolate and (6''S'')-5-methyltetrahydrofolate, and (6''S'')-5-MTHF) is the primary biologically active form of folate used at the cellular level for DNA reproduction, the cysteine cycle and the regulation of homocysteine. It is also the form found in circulation and transported across membranes into tissues and across the blood–brain barrier. In the cell, L-methylfolate is used in the methylation of homocysteine to form methionine and tetrahydrofolate ( THF). THF is the immediate acceptor of one carbon unit for the synthesis of thymidine-DNA, purines (RNA and DNA) and methionine. The un-methylated form, folic acid (vitamin B9), is a synthetic form of folate, and must undergo enzymatic reduction by dihydrofolate reductase ( DHFR) to become biologically active. Systematic reviews suggest that adjunctive L-methylfolate modestly improves symptoms in major depressive disorder. It is synthesized ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Levomefolic Acid
Levomefolic acid (INN, also known as L-5-MTHF, L-methylfolate and L-5-methyltetrahydrofolate and (6''S'')-5-methyltetrahydrofolate, and (6''S'')-5-MTHF) is the primary biologically active form of folate used at the cellular level for DNA reproduction, the cysteine cycle and the regulation of homocysteine. It is also the form found in circulation and transported across membranes into tissues and across the blood–brain barrier. In the cell, L-methylfolate is used in the methylation of homocysteine to form methionine and tetrahydrofolate ( THF). THF is the immediate acceptor of one carbon unit for the synthesis of thymidine-DNA, purines (RNA and DNA) and methionine. The un-methylated form, folic acid (vitamin B9), is a synthetic form of folate, and must undergo enzymatic reduction by dihydrofolate reductase ( DHFR) to become biologically active. Systematic reviews suggest that adjunctive L-methylfolate modestly improves symptoms in major depressive disorder. It is synthesized in th ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Mutation
In biology, a mutation is an alteration in the nucleic acid sequence of the genome of an organism, virus, or extrachromosomal DNA. Viral genomes contain either DNA or RNA. Mutations result from errors during DNA or viral replication, mitosis, or meiosis or other types of damage to DNA (such as pyrimidine dimers caused by exposure to ultraviolet radiation), which then may undergo error-prone repair (especially microhomology-mediated end joining), cause an error during other forms of repair, or cause an error during replication ( translesion synthesis). Mutations may also result from substitution, insertion or deletion of segments of DNA due to mobile genetic elements. Mutations may or may not produce detectable changes in the observable characteristics ( phenotype) of an organism. Mutations play a part in both normal and abnormal biological processes including: evolution, cancer, and the development of the immune system, including junctional diversity. Mutati ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Zygosity
Zygosity (the noun, zygote, is from the Greek "yoked," from "yoke") () is the degree to which both copies of a chromosome or gene have the same genetic sequence. In other words, it is the degree of similarity of the alleles in an organism. Most eukaryotes have two matching sets of chromosomes; that is, they are diploid. Diploid organisms have the same locus (genetics), loci on each of their two sets of homologous chromosomes except that the sequences at these loci may differ between the two chromosomes in a matching pair and that a few chromosomes may be mismatched as part of a chromosomal Sex-determination system#Chromosomal determination, sex-determination system. If both alleles of a diploid organism are the same, the organism is #Homozygous, homozygous at that locus. If they are different, the organism is #Heterozygous, heterozygous at that locus. If one allele is missing, it is #Hemizygous, hemizygous, and, if both alleles are missing, it is #Nullizygous, nullizygous. The ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Folate
Folate, also known as vitamin B9 and folacin, is one of the B vitamins. Manufactured folic acid, which is converted into folate by the body, is used as a dietary supplement and in food fortification as it is more stable during processing and storage. Folate is required for the body to make DNA and RNA and metabolise amino acids necessary for cell division and maturation of blood cells. As the human body cannot make folate, it is required in the diet, making it an essential nutrient. It occurs naturally in many foods. The recommended adult daily intake of folate in the U.S. is 400 micrograms from foods or dietary supplements. Folate in the form of folic acid is used to treat anemia caused by folate deficiency. Folic acid is also used as a supplement by women during pregnancy to reduce the risk of neural tube defects (NTDs) in the baby. NTDs include anencephaly and spina bifida, among other defects. Low levels in early pregnancy are believed to be the cause of more tha ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hyperhomocysteinemia
Hyperhomocysteinemia is a medical condition characterized by an abnormally high level of total homocysteine (that is, including homocystine and homocysteine-cysteine disulfide) in the blood, conventionally described as above 15 μmol/L. As a consequence of the biochemical reactions in which homocysteine is involved, deficiencies of vitamin B6, folic acid (vitamin B9), and vitamin B12 can lead to high homocysteine levels. Other possible causes of hyperhomocysteinemia include genetics, excessive methionine intake, and other diseases. Hyperhomocysteinemia is typically managed with vitamin B6, vitamin B9 and vitamin B12 supplementation. Hyperhomocysteinemia is a risk factor for cardiovascular disease; supplements of these vitamins may slightly reduce stroke outcome but not myocardial infarction, death from any cause or adverse events. Signs and symptoms Elevated levels of homocysteine have been associated with a number of disease states: more than 100 adverse outcomes have ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
