Tryglycerides
Triglycerides, or triacylglycerols, are natural fats and oils, composed of glycerin (chemically, "glycerol") and fatty acid chains.
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 and health
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.
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.
The American Heart Association has set guidelines for triglyceride levels:
; Less than 150 mg dL-1 : Normal range, lowest risk
; 150-199 mg dL-1 : Borderline high
; 200-499 mg dL-1 : High
; 500 mg dL-1 and above : Very high, increased risk
See also hypertriglyceridaemia.
Reducing triglyceride levels
Cardiovascular exercise and low fat diets are recommended 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.
Sources
- PubMed from http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=10880410&dopt=Abstract
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