Difference between revisions of "Choline" - New World Encyclopedia

From New World Encyclopedia
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==Function==
 
==Function==
 
[[Image:Choline_metabolism.png|thumb|300px|right|Choline metabolism. (Choline is green box at left, second from the bottom.)]]
 
[[Image:Choline_metabolism.png|thumb|300px|right|Choline metabolism. (Choline is green box at left, second from the bottom.)]]
Choline and its [[metabolites]] are needed for three main [[physiology|physiological]] purposes: structural integrity and [[cell signaling|signaling]] roles for cell membranes, cholinergic [[neurotransmission]] ([[acetylcholine]] [[protein biosynthesis|synthesis]]), and as a major source for [[methyl group]]s via its metabolite, [[trimethylglycine]] (betaine) that participates in the [[S-adenosylmethionine]] synthesis [[metabolic pathway|pathways]].  
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Choline and its [[metabolites]] are needed for three main [[physiology|physiological]] purposes: structural integrity and [[cell signaling|signaling]] roles for cell membranes, cholinergic [[neurotransmission]] ([[acetylcholine]] [[protein biosynthesis|synthesis]]), and as a major source for [[methyl group]]s via its metabolite.
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Choline is involved in the synthesis of phospholipids ''phosphatidylcholine'' and ''sphingomyelin'', which are are structural components of cell membranes (Higdon and Drake 2008). These two choline-containing phospholipids also are precursors for intracellular messenger molecules (diacyglycerol and ceramide) and two other choline metabolites, sphingophosphorylcholine and platelet activating factor (PAF) also are known as cell-signaling molecules (Higdon and Drake 2008).
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Choline is a precursor for synthesis of acetylcholine, which is a key [[neurotransmitter]]. A derivative of both choline and [[acetic acid]], acetylcholine is active both at the synapses between neurons and in the stimulation of muscle cells at the neuromuscular junction, and also stimulates secretion of glands.
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[[trimethylglycine]] (betaine) that participates in the [[S-adenosylmethionine]] synthesis [[metabolic pathway|pathways]].  
  
 
When choline is [[metabolism|metabolized]] by the [[body]], it may form [[trimethylamine]], a compound with a fishy odor. Hence, when large amounts of choline are taken the person may suffer from a fishy [[body odor]].
 
When choline is [[metabolism|metabolized]] by the [[body]], it may form [[trimethylamine]], a compound with a fishy odor. Hence, when large amounts of choline are taken the person may suffer from a fishy [[body odor]].

Revision as of 14:56, 17 July 2008

Choline
Choline-skeletal.png
IUPAC name (2-Hydroxyethyl)trimethylammonium
Identifiers
CAS number [62-49-7]
PubChem 305
MeSH Choline
SMILES C[N+](C)(C)CCO
Properties
Molecular formula C5H14NO+
Molar mass 104.17 g/mol
Except where noted otherwise, data are given for
materials in their standard state
(at 25 °C, 100 kPa)

Choline is a water-soluble organic compound that is classified as an essential nutrient for humans (Higdon and Drake 2008; PDR 2008; Swan and Zeisel 2000). This natural amine is involved in a number of important functions, including used in the synthesis of phospholipids and other structural components of cell membranes, is a precursor for the important neurotransmitter acetylcholine, and serves as a major source of methyl groups (Higdon and Drake 2008).

While historically choline had been grouped within the Vitamin B complex (vitamin Bp), it is not technically a vitamin (Higdon and Drake 2008). Vitamins are organic (carbon-containing) nutrients obtained through the diet and essential in small amounts for normal metabolic reactions. While choline is essential in small amounts for humans, it can be synthesized in the human body from other starting materials, rather than obtained through the diet. However, choline often cannot be manufactured at sufficient rates to meet the demands of the body, and thus must be consumed in the diet for optimal health. The Food and Nutrition Board of the Institute of Medicine of the National Academy of Sciences established an Adequate Intake level (AI) of 550 milligrams per day for adult males and 425 milligrams per day for adult females (450 mg/day for pregnant females and 550 mg/day for those breast-feeding) (Higdon and Drake 2008).

Although dietary intake often is necessary for humans, choline is a ubiquitous component of cell membranes and common in foods, and thus dietary deficiency is rare (Bender and Bender 2005).

Chemistry

Choline (C5H14NO+)

Choline is a quaternary saturated amine (organic compounds and functional groups that contain a basic nitrogen atom with a lone pair) with the chemical formula C5H14NO+, or (CH3)3N+CH2CH2OHX. where X is a counterion such as chloride (see choline chloride), hydroxide or tartrate. It is a derivative of the amino acid serine (Bender and Bender 2005), but is not a protein or amino acid (Swan and Zeisel 2000).

Choline is used in the synthesis of phosphatidylcholine, which is also known popularly as lecithin (although lecithin technically refers to a broader group of substances, one of which is phosphatidylcholine). Lecithin is common in health food stores and the lecithin from peanuts and soya beans is used as an emulsifying agent (Bender and Bender 2005; Swan and Zeisel 2000). Choline chloride, in mixture with urea is used as a solvent ( DES ) and the salicylate salt is used topically for pain relief of aphthous ulcers.

Choline was discovered by Andreas Strecker in 1864 and chemically synthesized in 1866. In the human body, it can be manufactured in the liver.

Dietary requirements and sources

In 1998, choline was classified as an essential nutrient by the Food and Nutrition Board (FNB) of the Institute of Medicine (U.S.A.) (Higdon and Drake 2008). While this board found insufficient scientific evidence to calculate a RDA (Recommended Daily Allowance, now Reference Daily Intake), they did set an Adequate Intake level (AI) (Higdon and Drake 2008). This ranged from 125 milligrams per day for infants 0 to 6 months of age to 550 milligrams per day for adolescent (14 to 18 years old) and adult males (19 and above) and breastfeeding females (Higdon and Drake 2008). The level for adult females was set at 425 milligrams per day. The FNB also established the tolerable upper intake level (UL) for choline at 3.5 grams per day for adults, based primarily on preventing hypotension (low blood pressure), as well as the fishy body order when it is broken down by bacteria in the large intestine, resulting in increased excretion of trimethylamine (Hidgon and Drake 2008; Swan and Zeisel 2000).

The foods richest in phosphatidylcholine—the major delivery form of choline—are egg yolks, soy, and cooked beef, chicken, veal and turkey livers. Many foods contain trace amounts of free choline, even iceberg lettuce. To what extent these trace forms are usable by human digestion is still debated. In 2004, the USDA released its first database of the choline content in common foods (Howe et al. 2004).

The most often available choline dietary supplement is lecithin, derived from soy or egg yolks, often used as a food additive. Phosphatidylcholine (often used synonymously with lecithin, although it is just one of the compounds classified as lecithin) is also available as a supplement, in pill or powder form. Supplementary choline is also available as choline chloride, which comes as a liquid due to its hydrophilic properties. Choline chloride is sometimes preferred as a supplement because phosphatidylcholine can have gastrointestinal side effects.

Function

Choline metabolism. (Choline is green box at left, second from the bottom.)

Choline and its metabolites are needed for three main physiological purposes: structural integrity and signaling roles for cell membranes, cholinergic neurotransmission (acetylcholine synthesis), and as a major source for methyl groups via its metabolite.

Choline is involved in the synthesis of phospholipids phosphatidylcholine and sphingomyelin, which are are structural components of cell membranes (Higdon and Drake 2008). These two choline-containing phospholipids also are precursors for intracellular messenger molecules (diacyglycerol and ceramide) and two other choline metabolites, sphingophosphorylcholine and platelet activating factor (PAF) also are known as cell-signaling molecules (Higdon and Drake 2008).

Choline is a precursor for synthesis of acetylcholine, which is a key neurotransmitter. A derivative of both choline and acetic acid, acetylcholine is active both at the synapses between neurons and in the stimulation of muscle cells at the neuromuscular junction, and also stimulates secretion of glands.


trimethylglycine (betaine) that participates in the S-adenosylmethionine synthesis pathways.

When choline is metabolized by the body, it may form trimethylamine, a compound with a fishy odor. Hence, when large amounts of choline are taken the person may suffer from a fishy body odor.

Choline as a supplement

It is well established that supplements of methyl group transfer vitamins B6, B12, folic acid reduce the blood titer of homocysteine and prevent heart disease. Choline is a necessary source of methyl groups for methyl group transfer. Supplements of lecithin/choline by Central Soya scientists reduced heart disease in laboratory studies. The reduction in heart disease with lecithin supplements may however relate more to the cholesterol carrying capacity of lecithin than to the methyl group transfer role of choline.

Choline supplements are often taken as a form of 'smart drug' or nootropic, due to the role that the neurotransmitter acetylcholine plays in various cognition systems within the brain. Choline is a chemical precursor or "building block" needed to produce the neurotransmitter acetylcholine, and research suggests that memory, intelligence and mood are mediated at least in part by acetylcholine metabolism in the brain. The compound's quaternary amine renders it lipid insoluble which might suggest it would be unable to cross the blood-brain barrier. However, despite choline's lipid insolubility, a choline transporter exists that allows transport across the blood-brain barrier. The efficacy of these supplements in enhancing cognitive abilities is a topic of continuing debate.

Lakhan & Vieira (2008)[1] link choline deficiency to bipolar disorder and report efficacy in lecithin supplementation based on a double-blind, placebo controlled trial.

Some people who practice lucid dreaming use Galantamine with choline bitartrate or Alpha GPC to increase their odds of having a lucid dream. Acetylcholine precursors such as choline work synergistically with Galantamine to help improve memory and the symptoms of Alzheimer's Disease (AD).

The Food and Drug Administration (FDA) requires that infant formula be made from cow's milk containing choline.[2]

Due to its role in lipid metabolism, choline has also found its way into nutritional supplements which claim to reduce body fat; but there is little or no evidence to prove that it has any effect on reducing excess body fat or that taking high amounts of choline will increase the rate at which fat is metabolised.

Fish odor syndrome

Choline is a precursor to trimethylamine, which some persons are not able to break down due to a genetic disorder. Persons suffering from this disorder, called trimethylaminuria, may suffer from a strong fishy or otherwise unpleasant body odor due to the body's release of odorous trimethylamine. A body odor will occur even on a normal diet - i.e., one that is not particularly high in choline. Persons with trimethylaminuria are advised to restrict the intake of foods high in choline; this may help to reduce the sufferer's body odor.

Choline hydroxide

Choline hydroxide is one of the class of phase transfer catalysts which are used to carry the hydroxide ion into organic systems. It is far and away the least costly phase transfer catalyst, and gets a lot of use in stripping photoresists in printed circuit board production. Choline hydroxide is not completely stable and it spontaneously, slowly breaks down to release trimethylamine. It is a strong base.


Additional images

References
ISBN links support NWE through referral fees

  1. Lakhan SE; Vieira KF. Nutritional therapies for mental disorders. Nutrition Journal 2008;7(2).
  2. Isadora B. Stehlin, "Infant Formula: Second Best but Good Enough," U.S. Food and Drug Administration.
  • Bender, D. A., and A. E. Bender. 2005. A Dictionary of Food and Nutrition. New York: Oxford University Press. ISBN 0198609612.


  • Physicians Desk Reference (PDR). 2008. Choline. PDRHealth. Retrieved July 17, 2008.



Vitamins
All B vitamins | All D vitamins
Retinol (A) | Thiamine (B1) | Riboflavin (B2) | Niacin (B3) | Pantothenic acid (B5) | Pyridoxine (B6) | Biotin (B7) | Folic acid (B9) | Cyanocobalamin (B12) | Ascorbic acid (C) | Ergocalciferol (D2) | Cholecalciferol (D3) | Tocopherol (E) | Naphthoquinone (K)

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