Thiamin , also known as thiamin or vitamin B 1 , is a vitamin found in foods, and is produced as a supplement food and medicine. Food sources include whole grains, peas, and some meat and fish. Grain processing eliminates a lot of thiamine content, so in many countries, cereals and flour are fortified with thiamine. Supplements and medications are available to treat and prevent the thiamine deficiency and disorders resulting from it, including beriberi and Wernicke encephalopathy. Other uses include the treatment of maple syrup urine and Leigh syndrome. They are usually taken, but may also be given by intravenous or intramuscular injection.
Thiamine supplements are generally well tolerated. Allergic reactions, including anaphylaxis, can occur when repeated doses are given by injection. Thiamine is in the B complex family. Thiamine is an important micronutrient, which can not be made in the body. This is necessary for metabolism including glucose, amino acids, and lipids.
Thiamine was discovered in 1897, was the first vitamin isolated in 1926, and was first made in 1936. It is on the World Health Organization's Essential Drug List, the most effective and safe medication needed in the health system. Thiamine is available as a generic drug, and as an over-the-counter remedy. The cost of grocery in developing countries (per 2016) is about 2.17 USD per one bottle of gm. In the United States, a month's supply is less than 25 USD.
Video Thiamine
Medical use
Lack of tiamina
Thiamine is used to treat thiamine deficiency which when severe can be fatal. In less severe cases, the nonspecific signs include malaise, weight loss, irritability, and confusion. Famous disorders caused by thiamine deficiency include beriberi, Wernicke-Korsakoff syndrome, and optic neuropathy. In Western countries, thiamine deficiency is seen primarily in chronic alcoholism. Also at risk are older adults, people with HIV/AIDS or diabetes, and people undergoing bariatric surgery. Different levels of thiamine deficiency have been associated with long-term use of high-dose diuretics, particularly furosemide in the treatment of heart failure.
Other uses
Thiamine is a treatment for some types of maple syrup urine and Leigh disease.
Maps Thiamine
Adverse effects
Side effects are generally slight. Allergic reactions including anaphylaxis may occur.
Chemistry
Thiamine is a colorless organosulfur compound with the chemical formula C 12 H 17 N 4 OS. The structure consists of aminopyrimidine and thiazole ring which are connected by a methylene bridge. Thiazoles are replaced with methyl and hydroxyethyl side chains. Thiamine is soluble in water, methanol, and glycerol and is practically insoluble in less polar organic solvents. It is stable at acidic pH, but unstable in alkaline solution. Thiamine, which is a persistent carbene, may be used instead of cyanide as a catalyst for benzoin condensation. Thiamine is unstable for heating, but stable during frozen storage. It is unstable when exposed to ultraviolet light and gamma irradiation. Thiamine strongly reacts with Maillard type reactions.
Biosynthesis
The complex thiamine biosynthesis occurs in bacteria, some protozoa, plants, and fungi. Thiazole and pyrimidine thiesia in biosynthesis separately and then combined to form thiamine monophosphate (ThMP) by thiamin-phosphate synthase action (EC2.5.1.3). Biosynthetic pathways may differ among organisms. In E. coli and other enterobacteriaceae, ThMP may be phosphorylated with thiamine diphospate cofactors (ThDP) by thiamine-phosphate kinase (ThMP ATP -> ThDP ADP, EC 2.7.4.16). In most bacteria and in eukaryotes, ThMP is hydrolysed into thiamine, which can then be thiophosphorylated into ThDP by thiamine diphosphinase (thiamine ATP -> ThDP AMP, EC 2.7.6.2).
The biosynthetic pathway is governed by the riboswitch. If there is enough thiamine present in the cell then thiamine binds mRNA to the necessary enzymes in the pathway and prevents its translation. If no thiamine is present then there is no inhibition, and the enzymes necessary for biosynthesis are produced. A special riboswitch, TPP riboswitch (or ThDP), is the only riboswitch identified in both eukaryotic and prokaryotic organisms.
Nutrition
Occurrences in food
Thiamine mononitrate salts, rather than thiamine hydrochloride, are used for food fortification, because mononitrate is more stable, and does not absorb water from natural (non-hygroscopic) moisture, whereas thiamine hydrochloride is hygroscopic. When the tiamina mononitrate dissolves in water, it releases nitrate (about 19% by weight) and is then absorbed as thiamine cation.
Dietary recommendations
In the US, the Average Estimates of Needs (EAR) and Recommended Dietary Allowances (RDAs) for thiamine were updated in 1998, by the Institute of Medicine now known as the National Academy of Medicine (NAM). Current EAR for thiamine for women and men aged 14 and above is 0.9 mg/day and 1.0 mg/day, respectively; RDAs are 1.1 and 1.2 mg/day, respectively. RDA is higher than EAR so it can identify the amount that would include people with higher than average requirements. The RDA for pregnancy is 1.4 mg/day. RDA for lactation is also 1.4 mg/day. For infants up to 12 months, Adequate Intake (AI) is 0.2 to 0.3 mg/day. For children aged 1-13 years, AKG increases with age from 0.5 to 0.9 mg/day. As for safety, IOM establishes a tolerable upper intake level (ULs) for vitamins and minerals when evidence is sufficient. In the case of thiamine there is no UL, because there is no human data for side effects of high doses. Collectively, EARs, RDAs, AIs and ULs are referred to as Dietary Reference Intakes (DRIs).
The European Food Safety Authority (EFSA) refers to a collection of collective information as a Dietary Reference Value, with a Population Reference Intake (PRI), not an RDA, and an Average Need, not an EAR. AI and UL are defined just like in the United States. For women (including those who are pregnant or breastfeeding), men and children PRI is 0.1 mg of thiamine per megajoule (MJ) of energy consumed. Since the conversion is 1 MJ = 238.8 kcal, an adult consuming 2,388 calories should consume 1.0 mg tiamine. This is slightly lower than the US RDA. EFSA reviews the same security question and also reaches the conclusion that there is no sufficient evidence to establish UL for thiamine.
For the labeling of food and US dietary supplements, the amount in the presentation is expressed as a percentage of the Daily Value (% DV). For the purpose of labeling 100% thiamine from the Daily Value is 1.5 mg, but on May 27, 2016 it was revised to 1.2 mg to make it agree with the RDA. The old and new daily Adult Value table is given in Daily Intake References. The original deadline to meet is July 28, 2018, but on September 29, 2017 the FDA released the proposed rule that extends the deadline to January 1, 2020 for large companies and 1 January 2021 for small companies.
Antagonist
Thiamine in foods can be degraded in various ways. Sulfites, which are added to food usually as preservatives, will attack thiamine in the methylene bridge in the structure, splitting the pyrimidine ring from the thiazole ring. The rate of this reaction increases in acidic conditions. Thiamine is degraded by thermolabile thiaminase (present in raw fish and shellfish). Some thiaminases are produced by bacteria. Bacterial Tiaminases are cell surface enzymes that must dissociate from the membrane before activation; dissociation may occur in ruminants under acidic conditions. The rumen bacteria also reduce sulfate to sulfite, therefore a high food intake of sulfate can have tiamine-antagonist activity.
The thiamine antagonist plant is heat-stable and occurs as both ortho- and para-hydroxyphenol. Some examples of this antagonist are caffeic acid, chlorogenic acid, and tannic acid. This compound interacts with thiamine to oxidize the thiazole ring, thus making it unabsorbed. Two flavonoids, quercetin and routine, have also been implicated as thiamine antagonists.
Food fortification
Purifying grains eliminates the bran and germs, and thus reduces natural vitamins and minerals. In the United States, vitamin B deficiency became common in the first half of the 20th century because of the consumption of white flour. The American Medical Association successfully lobbied to restore this vitamin with grain enrichment, which began in the United States in 1939. Britain followed it in 1940 and Denmark in 1953. By 2016, about 85 countries have passed legislation requiring fortification wheat flour with at least some nutrients, and 28% of industrial flour enriched, often with thiamine and other B vitamins.
Absorption and transport
Absorption
Thiamine is released by the action of phosphatase and pyrophosphatase in the upper small intestine. At low concentrations, this process is mediated by the operator. At higher concentrations, absorption also occurs through passive diffusion. Active transport is the largest in jejunum and ileum, but can be inhibited by alcohol consumption or by folate deficiency. The decrease in thiamine absorption occurs in the intake above 5 mg/day. On the serosal side of the intestine, the release of vitamins by the cells depends on Na -ATPase independent.
Binded to serum protein
The majority of thiamine in the serum is bound to proteins, especially albumin. About 90% of the total thiamine in the blood is in erythrocytes. A specific binding protein called thiamine binding protein (TBP) has been identified in rat serum and is believed to be an important hormone-regulated carrier protein for the distribution of thiamine tissue.
Mobile ingestion
The absorption of thiamine by blood cells and other tissues takes place through active transport and passive diffusion. About 80% of intracellular thiamine is phosphorylated and is largely bound to proteins. In some tissues, thiamine and secretion absorption appears to be mediated by a soluble thiamine transporter that depends on Na and a transcellular proton gradient.
Network distribution
The storage of human tiamina is about 25 to 30 mg, with the largest concentration in skeletal muscle, heart, brain, liver, and kidney. Thyme and free (unphosphorylated) Thiamine is present in plasma, milk, cerebrospinal fluid, and, presumably, all extracellular fluids. In contrast to the highly phosphorylated form of tiamina, ThMP and thiamine are free to cross the cell membrane. Thiamine content in human tissue is less than that of other species.
Excression
Thiamin and its acid metabolites (2-methyl-4-amino-5-pyrimidine carboxylic acids, 4-methyl-thiazol-5-acetic acid, and thiamine acetic acid) are excreted mainly in the urine.
Function
Phosphate derivatives are involved in many cellular processes. The most distinctive forms are thiamine pyrophosphate (TPP), coenzymes in the catabolism of sugars and amino acids. In yeast, TPP is also required in the first step of alcohol fermentation. All organisms use thiamine, but are only made on bacteria, fungi, and plants. Animals must get it from their food, and thus, for humans, it is an essential nutrient. Insufficient intake in birds produces typical polyneuritis.
Thiamine is usually regarded as a form of transport of vitamins. There are five known natural phosphate tiamina derivatives: thiamine monophosphate (ThMP), thiamine diphosphate (ThDP), also sometimes called thiamin pyrophosphate (TPP), thiamin triphosphate (THTP), and novel thiamine adenosine triphosphate (ATHTP), and adenosine thiamine diphosphate (AThDP). While the coenzyme role of tiamine diphosphate is well known and extensively characterized, the noncoenzyme action of thiamine and its derivatives can be realized by binding to a number of newly identified proteins that do not use the catalytic action of tiamine diphosphate.
Thiamine diphosphate
There is no known physiological role for thiamin monophosphate (ThMP); however, phosphologically relevant phosphates. The synthesis of tiamine diphosphate (ThDP), also known as thiamine pyrophosphate (TPP) or cocarboxylase , is catalyzed by an enzyme called thiamine diphosphokinase according to thiamine reaction ATP -> ThDP AMP (EC 2.7.6.2). ThDP is a coenzyme for several enzymes that catalyze the transfer of two carbon units and in particular dehydrogenation (decarboxylation and subsequent conjugation with coenzyme A) of 2-oxoacides (alpha-keto acid). Examples include:
- Present in most species
- pyruvate dehydrogenase and 2oxoglutarate dehydrogenase (also called? -ketoglutarate dehydrogenase)
- branched chain? acid-dehydrogenase acid
- 2-hydroxyphytanoyl-CoA lyase
- transketolase
- Comes in several species:
- decarboxylase pyruvate (in yeast)
- some additional bacterial enzymes
Transcetolase enzymes, pyruvate dehydrogenase (PDH), and 2-oxoglutarate dehydrogenase (OGDH) are all important in carbohydrate metabolism. The enzyme cytosol transketolase is a key player in the phosphate pentose pathway, the main route for the biosynthesis of deoxyribose and ribose pentoses. The mitochondrial PDH and OGDH are part of a biochemical pathway that produces the generation of adenosine triphosphate (ATP), which is the primary form of energy for cells. PDH connects glycolysis with the citric acid cycle, while the reaction catalyzed by OGDH is a step that limits the rate in the citric acid cycle. In the nervous system, PDH is also involved in the production of acetylcholine, neurotransmitters, and mielin synthesis.
Thiamine triphosphate
Thiamine triphosphate (ThTP) has long been regarded as a specific neuroactive tiamina form. However, it has recently been shown that ThTP exists in bacteria, fungi, plants and animals that exhibit a much more common role of cellular. Particularly in E. coli , it seems to play a role in the response to amino acid famine.
Adenosine thiamine triphosphate
Adenosine thiamine triphosphate (AThTP) or thiaminylated adenosine triphosphate was recently discovered in Escherichia coli , where it accumulates as a result of carbon hunger. At E. coli , AThTP can reach up to 20% of the total thiamine. It also exists in less amounts in yeast, the roots of higher plants and animal tissues.
Adenosine thiamine diphosphate
Adenosine thiamine diphosphate (AThDP) atau thiaminylated adenosine diphosphate ada dalam jumlah kecil di vertebrata hati, tetapi perannya masih belum diketahui.
Histori
- Beberapa kontributor untuk penemuan tiamin
Thiamine is the first of water-soluble vitamins to be explained, leading to the discovery of more important nutrients and the idea of ​​vitamins.
In 1884, Takaki Kanehiro (1849-1920), a general surgeon in the Japanese navy, rejected the earlier germ theory for beriberi and hypothesized that the disease was caused by insufficiency in the diet. Turning the diet on a navy ship, he found that replacing a white rice diet with just one also contained barley, meat, milk, bread, and vegetables, almost eliminated beriberi on a nine-month sea journey. However, Takaki has added a lot of food to a successful diet and he wrongly attributes the benefits to increased nitrogen intake, because vitamins are unknown substances at the time. The Navy was not convinced of the need for expensive food-raising programs, and many people continued to die of beriberi, even during the 1904-5 Russian-Japanese war. It was not until 1905, after the anti-beriberi factor had been found in rice bran (dumped with polishes into white rice) and in bran barley, was Takaki's experiment which was rewarded by making him a baron in the Japanese noble system, after which he was summoned by full of love. "Barley Baron".
A special relationship with grain was made in 1897 by Christiaan Eijkman (1858-1930), a military physician in the Dutch East Indies, who found that poultry fed with cooked rice, polished rice developed paralysis, which could be reversed by stopping rice polish. He connects beriberi to high levels of starch in rice to be poisonous. He believed that the toxicity was offset in the presence of compounds in rice polishings. A colleague, Gerrit Grijns (1865-1944) correctly interpreted the relationship between excessive consumption of rice and berries in 1901: He concluded that rice contained essential nutrients in the outer layer of grain removed by polishing. Eijkman was finally awarded the Nobel Prize in Physiology and Medicine in 1929, as his observations led to the discovery of vitamins.
In 1910 a Japanese scientist Umetaro Suzuki first isolated the compound he described as aberic acid . In a translation of Japanese paper that is claimed to be a new discovery, this claim is omitted. In 1911 a Polish biochemist Casimir Funk isolated an antineuritic substance from rice bran, which he called "vitamine" (because it contained an amino group.) The Dutch chemist Barend Coenraad Peter Jansen (1884-1962) and his closest collaborator Willem Frederik Donath. 1889-1957), then isolated and crystallized the active agent in 1926, whose structure was determined by Robert Runnels Williams (1886-1965), a US chemist, in 1934. Tiamin ("sulfur-containing vitamin") synthesized in 1936 by the same group.
Thiamin is first called "aneurin" (for anti-neuritic vitamins). Sir Rudolph Peters, in Oxford, introduced pigeon tiamina as a model to understand how thiamine deficiency can cause physiological-physiological symptoms of beriberi. Indeed, feeding pigeons on polished rice leads to a recognizable head retraction behavior, a condition called opisthotonos. If left untreated, the animals die after a few days. Administration of thiamine at the opisthotonos stage results in complete healing within 30 minutes. Since no morphological modification was observed in pigeon brain before and after treatment with thiamine, Peters introduced the concept of biochemical lesions.
When Lohman and Schuster (1937) demonstrated that the diphosphorylated tiamine derivative (thiamine diphosphate, ThDP) is the cofactor necessary for oxidative decarboxylation of pyruvate, a reaction now known to be catalyzed by pyruvate dehydrogenase, the mechanism of thiamine action in metabolic cells seems to be explained. Currently, this view seems overly simplified: Pyruvate dehydrogenase is just one of several enzymes that require thiosine diphosphate as a cofactor; In addition, other thiamine phosphate derivatives have been found since then, and they can also contribute to the symptoms observed during thiamine deficiency. Finally, the mechanism by which Thiamine moiety of ThDP provides its coenzyme function with proton substitution at position 2 of the thiazole ring was described by Ronald Breslow in 1958.
See also
- Vitamin B 1 analog
References
External links
Source of the article : Wikipedia
0 Comments