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

Triglyceride (help·info) (more properly known as triacylglycerol (help·info), TAG or triacylglyceride) is glyceride in which the glycerol is esterified with three fatty acids. Palmitic acid,CH3(CH214COOH or hexadecanoic acid in IUPAC nomenclature, is one of the most common saturated Fatty acids found in animals Oleic acid is a Monounsaturated omega-9 Fatty acid found in various animal and vegetable sources α -Linolenic acid ( ALA) is an organic compound found in many common vegetable oils. Glycerides, more correctly known as acylglycerols, are Esters formed from Glycerol and Fatty acids Glycerol has three Hydroxyl Esters are a class of Chemical compounds and Functional groups Esters consist of an inorganic or organic Acid in which at least In Chemistry, especially Biochemistry, a fatty acid is a Carboxylic acid often with a long unbranched Aliphatic tail ( chain) which ^[1] It is the main constituent of vegetable oil and animal fats. Animal fat s are rendered tissue fats that can be obtained from a variety of Animals Human nutrition Animal fats are often claimed to be

Chemical structure

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]. Ester bonds form between each fatty acid and the glycerol molecule. This is where the enzyme pancreatic lipase acts, 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.

General structure of a triglyceride

The chemical formula is RCOO-CH₂CH(-OOCR')CH₂-OOCR", where R, R', and R" are longer alkyl chains. An alkyl is a Univalent radical consisting of Carbon and Hydrogen atoms arranged in a chain The three fatty acids RCOOH, R'COOH and R"COOH can be all different, all the same, or only two the same.

Chain lengths of the fatty acids in naturally occurring triglycerides can be of varying lengths but 16, 18 and 20 carbons are the most common. Carbon (kɑɹbən is a Chemical element with the symbol C and its Atomic number is 6 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. Acetyl-CoA is an important molecule in metabolism used in many biochemical reactions 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. Physiologically a ruminant is a Mammal of the order Artiodactyla that digests plant-based food by initially softening it within the animal's first stomach known The Bacteria ( singular: bacterium) are a large group of unicellular Microorganisms Typically a few Micrometres in length bacteria have The rumen, also known as a paunch, forms the larger part of the Reticulorumen, which is the first chamber in the Alimentary canal of Ruminant

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, oleic and stearic acids in that order. Palmitic acid,CH3(CH214COOH or hexadecanoic acid in IUPAC nomenclature, is one of the most common saturated Fatty acids found in animals Oleic acid is a Monounsaturated omega-9 Fatty acid found in various animal and vegetable sources Stearic acid (first syllable rhymes with either bear or gear) ( IUPAC Systematic name: octadecanoic acid) is a saturated This gives rise to a fairly sharp melting point, causing chocolate to melt in the mouth without feeling greasy. Chocolate ( pronounced or /-ˈələt/ comprises a number of raw and processed foods that are produced from the seed of the tropical Cacao tree

Metabolism

See also fatty acid metabolism

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. Fatty acids are an important source of Energy for many organisms Chylomicrons are large lipoprotein particles that transport dietary lipids from the intestines to other locations in the body Metabolism is the set of Chemical reactions that occur in living Organisms in order to maintain Life. They contain more than twice as much energy (9 kcal/g) as carbohydrates and proteins. This article is about the unit of energy For its use in Nutrition and Food labelling regulations, see the article on Food energy. Carbohydrates (from ' Hydrates of Carbon ' or saccharides ( Greek σάκχαρον meaning " Sugar " are the most Proteins are large Organic compounds made of Amino acids arranged in a linear chain and joined together by Peptide bonds between the Carboxyl In the intestine, triglycerides are split into glycerol and fatty acids (this process is called lipolysis) (with the help of lipases and bile secretions), which are then moved into the cells lining the intestines (absorptive enterocytes). In Anatomy, the intestine is the segment of the alimentary canal extending from the Stomach to the Anus and in humans and other mammals consists Lipolysis is the breakdown of fat stored in fat cells During this process Free fatty acids are released into the bloodstream and circulate throughout the body A lipase is a Water-soluble Enzyme that Catalyzes the Hydrolysis of Ester bonds in water–insoluble Lipid Bile or gall is a bitter yellow or green Alkaline fluid secreted by Hepatocytes from the Liver of most Vertebrates In many species The triglycerides are rebuilt in the enterocytes from their fragments and packaged together with cholesterol and proteins to form chylomicrons. Cholesterol is a Lipid found in the Cell membranes and transported in the Blood plasma of all Animals It is an essential component of mammalian Chylomicrons are large lipoprotein particles that transport dietary lipids from the intestines to other locations in the body 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. In Chemistry, especially Biochemistry, a fatty acid is a Carboxylic acid often with a long unbranched Aliphatic tail ( chain) which Glucagon is an important Hormone involved in Carbohydrate metabolism. 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. The brain is the center of the Nervous system in animals All Vertebrates and the majority of Invertebrates have a brain Glucose (Glc a Monosaccharide (or simple Sugar) also known as grape sugar, is an important Carbohydrate in Biology. Gluconeogenesis (abreviated GNG) is a Metabolic pathway that results in the generation of Glucose from non- Carbohydrate carbon substrates such 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 breakdown triglycerides into fatty acids and glycerol. Fatty acids can then be taken up by cells via the fatty acid transporter (FAT).

Role in disease

See also the main article hypertriglyceridemia

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. In Medicine, hypertriglyceridemia (or "Hypertriglyceridaemia" denotes high ( hyper-) blood levels ( -emia) of Triglycerides the most Atherosclerosis is a Disease affecting arterial Blood vessels It is a chronic inflammatory response in the walls of arteries in large part due to the accumulation Coronary disease (or coronary heart disease) refers to the failure of Coronary circulation to supply adequate circulation to Cardiac muscle and surrounding A stroke is the rapidly developing loss of brain functions due to a disturbance in the blood vessels supplying blood to the brain However, the negative impact of raised levels of triglycerides is lower 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.

Another disease caused by high triglycerides is pancreatitis. Pancreatitis is the Inflammation of the Pancreas. See also Acute pancreatitis and Chronic pancreatitis for more details

Guidelines

The American Heart Association has set guidelines for triglyceride levels:^[2]

Please note that this information is relevant to triglyceride levels as tested after fasting 8 to 12 hours. Fasting is primarily the act of willingly abstaining from some or all Food, Drink, or both for a period of time Triglyceride levels remain temporarily higher for a period of time after eating.

When some fatty acids are converted to ketone bodies, overproduction can result in ketoacidosis in diabetics.

Reducing triglyceride levels

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)^[3], Omega-6 fatty acids, one or more grams of niacin (mega-dose vitamin B-3) per day and some statins reduce triglyceride levels. n −3 fatty acids (popularly referred to as ω−3 fatty acids or omega-3 fatty acids) are a family of unsaturated Fatty acids that n −6 fatty acids (popularly referred to as ω−6 fatty acids or omega-6 fatty acids) are a family of unsaturated Fatty acids Niacin, also known as vitamin B3, is a water-soluble vitamin which prevents the deficiency disease Pellagra. The statins (or HMG-CoA reductase inhibitors) form a class of hypolipidemic drugs used to lower Cholesterol levels in people with or at risk of Cardiovascular

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.

In some cases Fibrates have been used as they can bring down TGs substantially. In Pharmacology, the fibrates are a class of amphipathic Carboxylic acids They are used for a range of metabolic disorders mainly Hypercholesterolemia 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.

Alcohol abuse can cause elevated levels of triglycerides.

Industrial uses

Triglycerides are also split into their components via transesterification during the manufacture of biodiesel. In Organic chemistry, transesterification is the process of exchanging the Alcohol group of an Ester compound with another Alcohol. Biodiesel refers to a non-petroleum-based Diesel fuel consisting of short chain Alkyl ( Methyl or ethyl) Esters made by The fatty acid monoalkyl ester can be used as fuel in diesel engines. An alkyl is a Univalent radical consisting of Carbon and Hydrogen atoms arranged in a chain Esters are a class of Chemical compounds and Functional groups Esters consist of an inorganic or organic Acid in which at least A diesel engine is an Internal combustion engine which operates using the Diesel cycle (named after Dr The glycerin has many uses, such as in the manufacture of food and in the production of pharmaceuticals. Other examples are the Triglyceride process in the decaffeination of coffee beans. Decaffeination is the act of removing Caffeine from coffee beans, mate, Cocoa, Tea leaves and other caffeine-containing materials

Staining

Staining for fatty acids, triglycerides, lipoproteins, and other lipids is done through the use of lysochromes (fat-soluble dyes). A lysochrome is a Soluble dye used for biochemical staining of Triglycerides, Fatty acids and Lipoproteins Lysochromes 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. Sudan IV (C24H20N4O is a Lysochrome (fat-soluble dye Diazo dye used for the staining of Lipids, Oil Red O ( Solvent Red 27, Sudan Red 5B, CI 26125, C26H24N4O is a Lysochrome (fat-soluble dye Diazo Sudan Black B (C26H24N4O is a Lysochrome (fat-soluble dye Diazo dye used for staining of neutral Triglycerides

References

1. ^ Nomenclature of Lipids. IUPAC-IUB Commission on Biochemical Nomenclature (CBN). Retrieved on 2007-03-08. Year 2007 ( MMVII) was a Common year starting on Monday of the Gregorian calendar in the 21st century. Events 1618 - Johannes Kepler discovers the third law of planetary motion.
2. ^ What Your Cholesterol Levels Mean
3. ^ Fish and Omega-3 Fatty Acids. American Heart Association.

See also

• Diglyceride acyltransferase - enzyme responsible for triglyceride biosynthesis
• Medium chain triglycerides