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| [[Image:Fat triglyceride shorthand formula.PNG|thumb|Example of an unsaturated fat triglyceride. Left part: [[glycerol]], right part from top to bottom: [[palmitic acid]], [[oleic acid]], [[alpha-linolenic acid]], chemical formula: C<sub>55</sub>H<sub>98</sub>O<sub>6</sub>]]
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| {{SI}}
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| {{CMG}}
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| __NOTOC__ | | __NOTOC__ |
| | | {{Triglyceride}} |
| | {{CMG}}; {{AE}} [[Priyamvada Singh|Priyamvada Singh, M.B.B.S.]] [mailto:psingh13579@gmail.com]; {{Rim}} |
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| ==Overview== | | ==Overview== |
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| '''Triglyceride''' (more properly known as '''triacylglycerol''', '''TAG''' or '''triacylglyceride''') is [[glyceride]] in which the [[glycerol]] is [[ester]]ified with three [[fatty acid]]s.<ref>{{cite web | title=Nomenclature of Lipids |publisher=IUPAC-IUB Commission on Biochemical Nomenclature (CBN) | url=http://www.chem.qmul.ac.uk/iupac/lipid/ |accessdate=2007-03-08}}</ref> It is the main constituent of [[vegetable oil]] and [[animal fat]]s.
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| ==Chemical structure==
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| The chemical formula is RCOO-'''CH<sub>2</sub>CH'''(-OOCR')'''CH'''<sub>2</sub>-OOCR",
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| where R, R', and R" are longer [[alkyl]] chains. The three '''fatty acids''' RCOOH, R'COOH and R"COOH can be all different, all the same, or only two the same.
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| Chain lengths of the fatty acids in naturally occurring triglycerides can be of varying lengths but 16, 18 and 20 [[carbon]]s are the most common. Natural fatty acids found in plants and animals are typically composed only of even numbers of carbon atoms due to the way they are bio-synthesised from [[acetyl CoA]]. Bacteria, however, possess the ability to synthesise odd- and branched-chain fatty acids. Consequently, [[ruminant]] animal fat contains odd numbered fatty acids, such as 15, due to the action of [[bacteria]] in the [[rumen]].
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| Most natural fats contain a complex mixture of individual triglycerides; because of this, they melt over a broad range of temperatures. Cocoa butter is unusual in that it is composed of only a few triglycerides, one of which contains [[Palmitic acid|palmitic]], [[Oleic acid|oleic]] and [[Stearic acid|stearic]] acids in that order. This gives rise to a fairly sharp melting point, causing [[chocolate]] to melt in the mouth without feeling greasy.
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| <div align="left">
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| <gallery heights="175" widths="175">
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| Image:Triglyceride-GeneralStructure.png|General structure of a triglyceride
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| </gallery>
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| </div>
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| ==Metabolism ==
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| :''See also [[fatty acid metabolism]]''
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| Triglycerides, as major components of [[very low density lipoprotein]] (VLDL) and [[chylomicron]]s, play an important role in [[metabolism]] as energy sources and transporters of dietary fat. They contain more than twice as much energy (9 [[calorie|kcal]]/g) as [[carbohydrate]]s and [[protein]]s. In the [[intestine]], triglycerides are split into glycerol and fatty acids (this process is called [[lipolysis]]) (with the help of [[lipase]]s and [[bile]] secretions), which are then moved into the cells lining the intestines (absorptive enterocytes). The triglycerides are rebuilt in the enterocytes from their fragments and packaged together with [[cholesterol]] and proteins to form [[chylomicron]]s. These are excreted from the cells and collected by the lymph system and transported to the large vessels near the heart before being mixed into the blood. Various tissues can capture the chylomicrons, releasing the triglycerides to be used as a source of energy. Fat and liver cells can synthesize and store triglycerides. When the body requires [[fatty acid]]s as an energy source, the hormone [[glucagon]] signals the breakdown of the triglycerides by hormone-sensitive lipase to release free fatty acids. As the [[brain]] can not utilize fatty acids as an energy source, the [[glycerol]] component of triglycerides can be converted into [[glucose]], via [[gluconeogenesis]], for brain fuel when it is broken down. Fat cells may also be broken down for that reason, if the brain's needs ever outweigh the body's.
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| Triglycerides cannot pass through cell membranes freely. Special enzymes on the walls of blood vessels called lipoprotein lipases must breakdown triglycerides into fatty acids and glycerol. Fatty acids can then be taken up by cells via the fatty acid transporter (FAT).
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| ==Role in disease==
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| :''See also the main article [[hypertriglyceridemia]]''
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| In the human body, high levels of triglycerides in the bloodstream have been linked to [[atherosclerosis]], and, by extension, the risk of [[Coronary heart disease|heart disease]] and [[stroke]]. The negative impact of raised levels of triglycerides is higher than that of LDL:HDL ratios. The risk can be partly accounted for by a strong inverse relationship between triglyceride level and HDL-cholesterol level.
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| Another disease caused by high triglycerides is [[pancreatitis]].
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| ===Guidelines===
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| The [[American Heart Association]] has set guidelines for triglyceride levels:<ref>[http://www.americanheart.org/presenter.jhtml?identifier=183 What Your Cholesterol Levels Mean<!-- Bot generated title -->]</ref>
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| {| cellpadding=3 cellspacing=0 border=1 style="border-collapse:collapse"
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| |bgcolor="#cccccc"| '''Level''' [[Milligram|mg]]/[[Decilitre|dL]]
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| |bgcolor="#cccccc"| '''Level''' [[Mole (unit)|mmol]]/[[Litre|L]]
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| |bgcolor="#cccccc"| '''Interpretation'''
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| |-
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| | <150
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| | <1.69
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| | Normal range, low risk
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| |-
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| | 150-199
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| | 1.70-2.25
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| | Borderline high
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| |-
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| | 200-499
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| | 2.26-5.65
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| | High
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| |-
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| | >500
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| | >5.65
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| | Very high: high risk
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| |}
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| Please note that this information is relevant to triglyceride levels as tested after [[fasting#medical fasting|fasting]] 8 to 12 hours. Triglyceride levels remain temporarily higher for a period of time after eating.
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| When some fatty acids are converted to ketone bodies, overproduction can result in ketoacidosis in diabetics.
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| === Reducing triglyceride levels ===
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| Moderating the consumption of fats, alcohol and carbohydrates and partaking of aerobic exercise are considered essential to reducing triglyceride levels. [[Omega-3 fatty acids]] from fish, flax seed oil or other sources, (up to 3g per day in US, but up to 2g in Europe where it should be associated with Omega-6 with a ideal ω_6/ω_3 ratio near 5, unless under physician care)<ref name="omega3-aha">[http://www.americanheart.org/presenter.jhtml?identifier=4632 Fish and Omega-3 Fatty Acids]. American Heart Association.</ref>, [[Omega-6 fatty acids]], one or more grams of [[niacin]] (mega-dose vitamin B-3) per day and some [[statin]]s reduce triglyceride levels.
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| Unlike Japan, it is generally admitted that most populations in western countries are lacking omega-3 nutritional sources. As a result ingesting of excessively high levels of saturated or monounsaturated fatty acids in order to assimilate enough omega-6 fatty acids is common. The ideal ratio ω_6/ω_3 = 5 is almost never met and is most often too high (about 12 in France, up to 80 in the caucasian population of the US and Canada), and unused high levels of saturated or monounsaturated fatty acids accumulate in the body in the form of triglycerides that do not participate in the needed syntheses in the body.
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| In some cases [[Fibrates]] have been used as they can bring down TGs substantially. However they are not used as a first line measure as they can have unpleasant or dangerous side effects. In one case due to an increase in mortality, clofibrate was withdrawn from the North American market.
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| Alcohol abuse can cause elevated levels of triglycerides.
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| Triglycerides are formed from a single molecule of glycerol, combined with three fatty acids on each of the OH groups, and make up most of fats digested by humans. A triglyceride is shown in the diagram[2].
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| Ester bonds form between each fatty acid and the glycerol molecule.
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| This is where the enzyme pancreatic lipase acts, hydrolysing the bond and ‘releasing’ the fatty acid.
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| In triglyceride form, lipids cannot be absorbed by the duodenum. Fatty acids, monoglycerides (one glycerol, one fatty acid) and some diglycerides are absorbed by the duodenum, once the triglycerides have been broken down.
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| ==Industrial uses==
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| Triglycerides are also split into their components via [[transesterification]] during the manufacture of [[biodiesel]]. The fatty acid mono[[alkyl]] [[ester]] can be used as fuel in diesel engines. The glycerin has many uses, such as in the manufacture of food and in the production of pharmaceuticals.
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| Other examples are the Triglyceride process in the decaffeination of coffee beans.
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| ==Staining==
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| Staining for fatty acids, triglycerides, lipoproteins, and other lipids is done through the use of [[lysochrome]]s (fat-soluble dyes). These dyes can allow the qualification of a certain fat of interest by staining the material a specific color. Some examples: [[Sudan IV]], [[Oil Red O]], and [[Sudan Black B]].
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| == References ==
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| <references/>
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| ==See also==
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| *[[Diglyceride acyltransferase]] - enzyme responsible for triglyceride biosynthesis
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| *[[Medium chain triglycerides]]
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| {{Glycerides}}
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| {{Electrocardiography}}
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| {{Circulatory system pathology}}
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| [[Category:Triglycerides| ]]
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| [[Category:Lipid disorders]]
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| [[Category:Cardiology]]
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| [[bg:Мазнина]]
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| [[ca:Triacilglicèrid]]
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| [[da:Triglycerid]]
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| [[de:Triglyceride]]
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| [[es:Triglicérido]]
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| [[eo:Triglicerido]]
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| [[fr:Triglycéride]]
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| [[hr:Trigliceridi]]
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| [[id:Trigliserida]]
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| [[it:Trigliceride]]
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| [[he:טריגליצריד]]
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| [[lt:Trigliceridas]]
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| [[mk:Триглицерид]]
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| [[nl:Triglyceride]]
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| [[ja:トリアシルグリセロール]]
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| [[pl:Triacyloglicerole]]
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| [[pt:Triacilglicerol]]
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| [[ru:Жиры]]
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| [[fi:Triglyseridi]]
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| [[tl:Trayglisirayd]]
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| [[zh:三酸甘油脂]]
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