Triglyceride
1
Triglyceride
A triglyceride (triacylglycerol, TAG or triacylglyceride) is an ester
derived from glycerol and three fatty acids.[1] It is the main constituent
of vegetable oil and animal fats.[2]
Chemical structure
Triglycerides are formed by combining glycerol with three molecules
of fatty acid. The glycerol molecule has three hydroxyl (HO-) groups.
Each fatty acid has a carboxyl group (HOOC-). In triglycerides, the
hydroxyl groups of the glycerol join the carboxyl groups of the fatty
acid to form ester bonds:
Example of an unsaturated fat triglyceride. Left
part: glycerol, right part from top to bottom:
palmitic acid, oleic acid, alpha-linolenic acid,
chemical formula: C55H98O6
HOCH2CH(OH)CH2OH + RCO2H + R'CO2H + R''CO2H → RCO2CH2CH(O2CR')CR'' + 2O
The three fatty acids (RCO2H, R'CO2H, R''CO2H in the above equation) are usually different, but many kinds of
triglycerides are known. The chain lengths of the fatty acids in naturally occurring triglycerides vary, but most
contain 16, 18, or 20 carbon atoms. Natural fatty acids found in plants and animals are typically composed only of
even numbers of carbon atoms, reflecting the pathway for their biosynthesis from the two-carbon building block
acetyl CoA. Bacteria, however, possess the ability to synthesise odd- and branched-chain fatty acids. As a result,
ruminant animal fat contains odd-numbered fatty acids, such as 15, due to the action of bacteria in the rumen. Many
fatty acids are unsaturated, some are polyunsaturated, e.g., those derived from linoleic acid.
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, derived from palmitic,
oleic, and stearic acids.
Metabolism
The enzyme pancreatic lipase acts at the ester bond, hydrolysing the bond and "releasing" the fatty acid. 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.
Triglycerides, as major components of very-low-density lipoprotein (VLDL) and chylomicrons, play an important
role in metabolism as energy sources and transporters of dietary fat. They contain more than twice as much energy (9
kcal/g or 38 kJ/g ) as carbohydrates and proteins. In the intestine, triglycerides are split into monoacylglycerol and
free fatty acids in a process called lipolysis, with the secretion of lipases and bile, which are subsequently moved to
absorptive enterocytes, cells lining the intestines. The triglycerides are rebuilt in the enterocytes from their fragments
and packaged together with cholesterol and proteins to form chylomicrons. 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 acids 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 cannot utilize fatty acids as an energy source (unless converted to a ketone), 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.
Triglycerides cannot pass through cell membranes freely. Special enzymes on the walls of blood vessels called
lipoprotein lipases must break down triglycerides into free fatty acids and glycerol. Fatty acids can then be taken up
by cells via the fatty acid transporter (FAT).
Triglyceride
2
Role in disease
In the human body, high levels of triglycerides in the bloodstream have been linked to atherosclerosis, and, by
extension, the risk of heart disease and stroke. However, the relative negative impact of raised levels of triglycerides
compared to that of LDL:HDL ratios is as yet unknown. The risk can be partly accounted for by a strong inverse
relationship between triglyceride level and HDL-cholesterol level.
Guidelines
The American Heart Association has set guidelines for triglyceride levels:[3]
Level mg/dL Level mmol/L Interpretation
<150
<1.69
Normal range, low risk
150-199
1.70-2.25
Borderline high
200-499
2.26-5.65
High
>500
>5.65
Very high: high risk
Please note that this information is relevant to triglyceride levels as tested after fasting 8 to 12 hours. Triglyceride
levels remain temporarily higher for a period of time after eating.
Reducing triglyceride levels
Diets high in carbohydrates, with carbohydrates accounting for more than 60% of the total caloric intake, can
increase triglyceride levels.[3] Of note is how the correlation is stronger for those with higher BMI (28+) and insulin
resistance (more common among overweight and obese) is a primary suspect cause of this phenomenon of
carbohydrate-induced hypertriglyceridemia.[4]
There is evidence that carbohydrate consumption causing a high glycemic index can cause insulin overproduction
and increase triglyceride levels in women.[5]
Adverse changes associated with carbohydrate intake, including triglyceride levels, are stronger risk factors for heart
disease in women than in men.[6]
Triglyceride levels are also reduced by exercise, omega-3 fatty acids from fish, flax seed oil, and other sources.
Recommendation in the U.S. is that one ingest up to 3 grams a day of such oils. It has been found that residents in
Western countries do not ingest sufficient quantity of food with omega-3. In Europe, the recommendation is for up to
2 grams. However, omega-3 consumption should be balanced with omega-6 fatty acids, in a ω-6/ω-3 ratio between
1:1 and 4:1 (i.e., no more than four grams omega-6 for every one of omega-3).[7] [8]
Carnitine has the ability to lower blood triglyceride levels.[9] In some cases, fibrates have been used to bring down
triglycerides substantially.[10]
Heavy use of alcohol can elevate triglycerides levels.[11]
Triglyceride
3
Industrial uses
Linseed oil and related oils are important components of useful products used in oil paints and related coatings.
Linseed oil is rich in di- and triunsaturated fatty acid components, which tend to harden in the presence of oxygen.
The hardening process is peculiar to these so-called "drying oils". It is caused by a polymerization process that
begins with oxygen attacking the carbon backbone.
Triglycerides are also split into their components via transesterification during the manufacture of biodiesel. The
resulting fatty acid esters 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.
Staining
Staining for fatty acids, triglycerides, lipoproteins, and other lipids is done through the use of lysochromes
(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.
Interactive pathway map
Click on genes, proteins and metabolites below to link to respective Wikipedia articles. [12]
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Triglyceride
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Statin Pathway edit [13]
Triglyceride
See also
•
•
•
•
Diglyceride acyltransferase – enzyme responsible for triglyceride biosynthesis
Medium chain triglycerides
Lipids
Vertical Auto Profile
References
[1] "Nomenclature of Lipids" (http:/ / www. chem. qmul. ac. uk/ iupac/ lipid/ ). IUPAC-IUB Commission on Biochemical Nomenclature (CBN).
. Retrieved 2007-03-08.
[2] Nelson, D. L.; Cox, M. M. "Lehninger, Principles of Biochemistry" 3rd Ed. Worth Publishing: New York, 2000. ISBN 1-57259-153-6.
[3] "Your Triglyceride Level" (http:/ / www. americanheart. org/ presenter. jhtml?identifier=183#Triglyceride). What Your Cholesterol Levels
Mean. American Heart Association. . Retrieved 2009-05-22.
[4] Parks, E.J. (2002). "Dietary carbohydrate’s effects on lipogenesis and the relationship of lipogenesis to blood insulin and glucose
concentrations". British Journal of Nutrition 87: S247–S253. doi:10.1079/BJN/2002544. PMID 12088525. "Those with a body mass index
(BMI) equal to or greater than 28 kg/m2 experienced a 30% increase in TAG concentration, while those whose BMI was less than 28,
experienced no change...These data demonstrate that certain characteristics (e.g. BMI) can make some individuals more sensitive with respect
to lipid and lipoprotein changes when dietary CHO is increased. Such characteristics that have been identified from previous work in this field
and include BMI, insulin sensitivity (Coulston et al. 1989), concentration of TAG before the dietary change is made (Parks et al. 2001),
hormone replacement therapy (Kasim-Karakas et al. 2000), and genetic factors (Dreon et al. 2000).".
[5] "Focusing on Fiber?" (http:/ / www. drweil. com/ drw/ u/ id/ QAA298788). Drweil.com. . Retrieved 2010-08-02.
[6] "Dietary Glycemic Load and Index and Risk of Coronary Heart Disease in a Large Italian Cohort" (http:/ / archinte. ama-assn. org/ cgi/
content/ abstract/ 170/ 7/ 640). Archives of internal medicine. . Retrieved 2010-05-01.
[7] "Fish and Omega-3 Fatty Acids" (http:/ / www. americanheart. org/ presenter. jhtml?identifier=4632). American Heart Association. .
Retrieved 2009-05-22.
[8] Daley, C.A.; Abbott, A.; Doyle, P.; Nader, G.; and Larson, S. (2004). A literature review of the value-added nutrients found in grass-fed beef
products (http:/ / www. csuchico. edu/ agr/ grassfedbeef/ health-benefits/ index. html). California State University, Chico (College of
Agriculture). . Retrieved 2008-03-23.
[9] Balch, Phyllis A. Prescription for nutritional healing. 4th ed. New York: Avery, 2006. p. 54 Carnitine
[10] "Fibrates: Where Are We Now?: Fibrates and Triglycerides" (http:/ / www. medscape. com/ viewarticle/ 587134_7). Medscape.com. .
Retrieved 2010-08-02.
[11] Hemat, R A S (2003). Principles of Orthomolecularism (http:/ / books. google. com/ ?id=ED_xI-CEzFYC& pg=PA254& lpg=PA254&
dq=alcohol+ consumption+ can+ elevate+ triglyceride+ levels). Urotext. p. 254. ISBN 1903737060. .
[12] The interactive pathway map can be edited at WikiPathways: "StatinPathway_WP430" (http:/ / www. wikipathways. org/ index. php/
Pathway:WP430). .
[13] http:/ / www. wikipathways. org/ index. php/ Pathway:WP430
6
Article Sources and Contributors
Article Sources and Contributors
Triglyceride Source: http://en.wikipedia.org/w/index.php?oldid=394452762 Contributors: Acornford, AirdishStraus, Alansohn, Anchoress, AnthonyQBachler, Anurag Garg, Arbitrarily0,
Arcadian, Arkwatem, Armend, Atran Lab, AxelBoldt, BWernham, Bensaccount, BillBigfoot, Biophys, Bomac, BrandonKuhl1979, Brian Sayrs, Bubba73, C.Fred, Can't sleep, clown will eat me,
CaptainVindaloo, Choij, Clam0p, CliffC, Cmh, Corruptcopper, DaGizza, Danielle dk, Danny-w, DarkoV, Davidruben, Dethroned Buoy, Djsasso, Donarreiskoffer, Drphilharmonic, E0steven,
Edgar181, Eric Yurken, Esperant, Ethridgela, Euryalus, Fluppy, Frankg, FrummerThanThou, Gene Nygaard, Gilliam, Grandia01, Gruber76, Gurch, Guy Harris, HexaChord, Hexum, Ibbn, Isnow,
Itecle, J.delanoy, Jag123, Jaganath, JeLuF, Jeffq, JesseW, Jeversol, Jfdwolff, Joanjoc, Jpgordon, Jrtayloriv, Juliancolton, Justin W Smith, Kairos, Kazkaskazkasako, Kenmcl2, Killer666xxx5,
Kilo-Lima, Kimiko, Kokkogdrit, Kpjas, KristinaHanspers, Ksheka, LEitK, La hapalo, Lagalag, Lapo3399, LeaveSleaves, Linas, Lwoauis, Lysy, Mac, Magog the Ogre, Marj Tiefert, Markp93,
Martian.knight, Maximus Rex, Mctt, Mey Pey, Mikael Häggström, Milkfish, Mlpearc, Musicality213, Mwhenson, N.hong.phuc, Nbauman, Nick125, Nishkid64, Nk, Olivier, Openlander,
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Rick Block, Rifleman 82, Roadnottaken, Rochellelim84, Rod57, RubyQ, Sadiq786, Sakkura, Scodocs2, SemperBlotto, Shenme, Sifaka, Skaaii, Smokefoot, Snigbrook, Stepa, Superccs,
Supertouch, SvenAERTS, Svizac, Switchscribe, Taskualads, Taxman, Tempodivalse, The Rambling Man, Theamazingandy, They aside, ThomasWinwood, TimVickers, Tlesher,
TonyRobinson787, Travis.Thurston, Tyciol, Verdy p, Versus22, WhatamIdoing, WolfmanSF, Xezbeth, Yekrats, ‫کشرز‬, आशीष भटनागर, 289 anonymous edits
Image Sources, Licenses and Contributors
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