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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. It is synthesized in the absorptive cells of the small intestine from polyglutamylated dietary folate. It is a methylated derivative of t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Methylenetetrahydrofolate Reductase
Methylenetetrahydrofolatereductase (MTHFR) is the rate-limiting enzyme in the methyl cycle, and it is encoded by the ''MTHFR'' gene. Methylenetetrahydrofolate reductase catalyzes the conversion of 5,10-methylenetetrahydrofolate to 5-methyltetrahydrofolate, a cosubstrate for homocysteine remethylation to methionine. Natural variation in this gene is common in otherwise healthy people. Although some variants have been reported to influence susceptibility to occlusive vascular disease, neural tube defects, Alzheimer's disease and other forms of dementia, colon cancer, and acute leukemia, findings from small early studies have not been reproduced. Some mutations in this gene are associated with methylenetetrahydrofolate reductase deficiency. Complex I deficiency with recessive spastic paraparesis has also been linked to ''MTHFR'' variants. In addition, the aberrant promoter hypermethylation of this gene is associated with male infertility and recurrent spontaneous abortion. ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
MTHFR Metabolism
Methylenetetrahydrofolatereductase (MTHFR) is the rate-limiting enzyme in the methyl cycle, and it is encoded by the ''MTHFR'' gene. Methylenetetrahydrofolate reductase catalyzes the conversion of 5,10-methylenetetrahydrofolate to 5-methyltetrahydrofolate, a cosubstrate for homocysteine remethylation to methionine. Natural variation in this gene is common in otherwise healthy people. Although some variants have been reported to influence susceptibility to occlusive vascular disease, neural tube defects, Alzheimer's disease and other forms of dementia, colon cancer, and acute leukemia, findings from small early studies have not been reproduced. Some mutations in this gene are associated with methylenetetrahydrofolate reductase deficiency. Complex I deficiency with recessive spastic paraparesis has also been linked to ''MTHFR'' variants. In addition, the aberrant promoter hypermethylation of this gene is associated with male infertility and recurrent spontaneous abortion. Bioche ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Methionine Synthase
Methionine synthase also known as MS, MeSe, MTR is responsible for the regeneration of methionine from homocysteine. In humans it is encoded by the ''MTR'' gene (5-methyltetrahydrofolate-homocysteine methyltransferase). Methionine synthase forms part of the S-adenosylmethionine (SAMe) biosynthesis and regeneration cycle, and is the enzyme responsible for linking the cycle to one-carbon metabolism via the folate cycle. There are two primary forms of this enzyme, the Vitamin B12 (cobalamin)-dependent (MetH) and independent (MetE) forms, although minimal core methionine synthases that do not fit cleanly into either category have also been described in some anaerobic bacteria. The two dominant forms of the enzymes appear to be evolutionary independent and rely on considerably different chemical mechanisms. Mammals and other higher eukaryotes express only the cobalamin-dependent form. In contrast, the distribution of the two forms in Archaeplastida (plants and algae) is more complex. P ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
5,10-methylenetetrahydrofolate
5,10-Methylenetetrahydrofolate (N5,N10-Methylenetetrahydrofolate; 5,10-CH2-THF) is cofactor in several biochemical reactions. It exists in nature as the diastereoisomer R5,10-methylene-THF. As an intermediate in one-carbon metabolism, 5,10-CH2-THF interconverts to 5-methyltetrahydrofolate, 5-formyltetrahydrofolate, and methenyltetrahydrofolate. It is substrate for the enzyme methylenetetrahydrofolate reductase (MTHFR) It is mainly produced by the reaction of tetrahydrofolate with serine, catalyzed by the enzyme serine hydroxymethyltransferase. Selected functions Formaldehyde detoxification Methylenetetrahydrofolate is an intermediate in the detoxification of formaldehyde. Pyrimidine biosynthesis It is the one-carbon donor for thymidylate synthase, for methylation of 2-deoxy-uridine-5-monophosphate (dUMP) to 2-deoxy-thymidine-5-monophosphate (dTMP). The coenzyme is necessary for the biosynthesis of thymidine and is the C1-donor in the reactions catalyzed by TS and thymid ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Homocysteine
Homocysteine is a non-proteinogenic α-amino acid. It is a homologue of the amino acid cysteine, differing by an additional methylene bridge (-CH2-). 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 certain B-vitamins. High levels of homocysteine in the blood ( hyperhomocysteinemia) is regarded as a marker of cardiovascular disease, likely working through atherogenesis, which can result in 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 arteries, which supply the heart with oxygenated blood. Hyperhomocysteinemia has been correlated with the occurrence of blood clots, heart attacks, and strokes, although it is unclear whether hyperhomocysteinemia is an independent risk factor for these c ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Methylation
In the chemical sciences, methylation denotes the addition of a methyl group on a substrate, or the substitution of an atom (or group) by a methyl group. Methylation is a form of alkylation, with a methyl group replacing a hydrogen atom. These terms are commonly used in chemistry, biochemistry, soil science, and the biological sciences. In biological systems, methylation is catalyzed by enzymes; such methylation can be involved in modification of heavy metals, regulation of gene expression, regulation of protein function, and RNA processing. In vitro methylation of tissue samples is also one method for reducing certain histological staining artifacts. The reverse of methylation is demethylation. In biology In biological systems, methylation is accomplished by enzymes. Methylation can modify heavy metals, regulate gene expression, RNA processing and protein function. It has been recognized as a key process underlying epigenetics. Methanogenesis Methanogenesis, the proces ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Atypical Antipsychotic
The atypical antipsychotics (AAP), also known as second generation antipsychotics (SGAs) and serotonin–dopamine antagonists (SDAs), are a group of antipsychotic drugs (antipsychotic drugs in general are also known as major tranquilizers and neuroleptics, although the latter is usually reserved for the '' typical antipsychotics'') largely introduced after the 1970s and used to treat psychiatric conditions. Some atypical antipsychotics have received regulatory approval (e.g. by the FDA of the US, the TGA of Australia, the MHRA of the UK) for schizophrenia, bipolar disorder, irritability in autism, and as an adjunct in major depressive disorder. Both generations of medication tend to block receptors in the brain's dopamine pathways. Atypicals are less likely than haloperidol — the most widely used typical antipsychotic — to cause extrapyramidal motor control disabilities in patients such as unsteady Parkinson's disease-type movements, body rigidity, and invo ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Selective Serotonin Reuptake Inhibitor
Selective serotonin reuptake inhibitors (SSRIs) are a class of drugs that are typically used as antidepressants in the treatment of major depressive disorder, anxiety disorders, and other psychological conditions. SSRIs increase the extracellular level of the neurotransmitter serotonin by limiting its reabsorption (reuptake) into the presynaptic cell. They have varying degrees of selectivity for the other monoamine transporters, with pure SSRIs having strong affinity for the serotonin transporter and only weak affinity for the norepinephrine and dopamine transporters. SSRIs are the most widely prescribed antidepressants in many countries. The efficacy of SSRIs in mild or moderate cases of depression has been disputed and may or may not be outweighed by side effects, especially in adolescent populations. Medical uses The main indication for SSRIs is major depressive disorder; however, they are frequently prescribed for anxiety disorders, such as social anxiety disorder, gen ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Serotonin–norepinephrine Reuptake Inhibitor
Serotonin–norepinephrine reuptake inhibitors (SNRIs) are a class of antidepressant drugs used to treat major depressive disorder (MDD), anxiety disorders, obsessive–compulsive disorder (OCD), social phobia, attention-deficit hyperactivity disorder (ADHD), chronic neuropathic pain, fibromyalgia syndrome (FMS), and menopausal symptoms. SNRIs are monoamine reuptake inhibitors; specifically, they inhibit the reuptake of serotonin and norepinephrine. These neurotransmitters are thought to play an important role in mood regulation. SNRIs can be contrasted with the more widely used selective serotonin reuptake inhibitors (SSRIs), which act upon serotonin only. The human serotonin transporter (SERT) and noradrenaline transporter (NAT) are membrane transport proteins that are responsible for the reuptake of serotonin and noradrenaline from the synaptic cleft back into the presynaptic nerve terminal. Dual inhibition of serotonin and noradrenaline reuptake can offer advantages o ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Colorectal Cancer
Colorectal cancer (CRC), also known as bowel cancer, colon cancer, or rectal cancer, is the development of cancer from the colon or rectum (parts of the large intestine). Signs and symptoms may include blood in the stool, a change in bowel movements, weight loss, and fatigue. Most colorectal cancers are due to old age and lifestyle factors, with only a small number of cases due to underlying genetic disorders. Risk factors include diet, obesity, smoking, and lack of physical activity. Dietary factors that increase the risk include red meat, processed meat, and alcohol. Another risk factor is inflammatory bowel disease, which includes Crohn's disease and ulcerative colitis. Some of the inherited genetic disorders that can cause colorectal cancer include familial adenomatous polyposis and hereditary non-polyposis colon cancer; however, these represent less than 5% of cases. It typically starts as a benign tumor, often in the form of a polyp, which over time becomes cancer ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Adjunctive Therapy
Combination therapy or polytherapy is therapy that uses more than one medication or modality. Typically, the term refers to using multiple therapies to treat a ''single'' disease, and often all the therapies are pharmaceutical (although it can also involve non-medical therapy, such as the combination of medications and talk therapy to treat depression). 'Pharmaceutical' combination therapy may be achieved by prescribing/administering separate drugs, or, where available, dosage forms that contain more than one active ingredient (such as fixed-dose combinations). Polypharmacy is a related term, referring to the use of multiple medications (without regard to whether they are for the same or separate conditions/diseases). Sometimes "polymedicine" is used to refer to pharmaceutical combination therapy. Most of these kinds of terms lack a universally consistent definition, so caution and clarification are often advisable. Uses Conditions treated with combination therapy include tubercul ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
