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Triglyceride
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Triglyceride

Triglycerides, or triacylglycerols, are natural fats and oils, composed of glycerin (chemically, "glycerol") and fatty acid chains. 

Table of contents
1 Chemical structure
2 Metabolism
3 Role in disease
4 Industrial uses

Chemical structure

The fatty acids are linked to the glycerol so as to form 3 ester functional groups:

CH2COOR-CHCOOR'-CH2-COOR"

where R, R', and R" are fatty acids; the three fatty acids can be all different, all the same, or only two the same.

R1-COOH + R2-OH <----> R-COO-R2 + H2O

carboxylic acid (= fatty acid) + alcohol (= glycerol) <-----> triglyceride + water

Chain lengths of triglycerides are 16 to 22 C atoms.

Metabolism

Triglycerides play an important role in metabolism as energy sources. They contain twice as much energy (8000 kcal/kg) as carbohydrates. In the intestine, triglycerides are split into glycerol and fatty acids (with the help of lipases and bile secretions), which can then move into blood vessels. The triglycerides are rebuilt in the blood from their fragments and become constituents of lipoproteins. Various tissues can release the free fatty acids and take them up as a source of energy. Fat 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.

Role in disease

See also the main article hypertriglyceridaemia

In the human body, high levels of triglycerides in the bloodstream have been linked to atherosclerosis, and, by extension, to the risk of heart disease and stroke. However, the negative impact of raised levels of triglycerides is lower than that of LDL-cholesterol. The risk can be partly accounted for a strong inverse relationship between triglyceride level and HDL-cholesterol level.

Other diseases caused by high triglycerides include pancreatitis.

Guidelines

The American Heart Association has set guidelines for triglyceride levels:

Level mg/dl Level mmol/L Interpretation
<150 <1.69 Normal range, lowest risk
150-199 1.70-2.25 Borderline high
200-499 2.25-5.63 High
>500 >5.65 Very high, increased risk

Reducing triglyceride levels

Cardiovascular exercise and low-moderate carbohydrate diets containing essential fatty acid are recommended for reducing triglyceride levels. When these fail, fibrate drugs (and some statins) are registered for reducing triglyceride levels.

Industrial uses

Triglycerides are also split into their components via transesterification during the manufacture of biodiesel. The fatty acid monoalkyl ester can be used as fuel in diesel engines. The glycerin can be used for food and in pharmaceutical production, among others.