Mead acid
Encyclopedia
Mead acid is an omega-9 fatty acid
, first characterized by James F. Mead. Like some other omega-9 polyunsaturated fatty acid
s animals can make Mead acid de novo. Its elevated presence in the blood is an indication of essential fatty acid
deficiency. Mead acid is found in large quantities in cartilage
.
with a 20-carbon
chain and three methylene
-interrupted cis double bonds. The first double bond is located at the ninth carbon from the omega end. In physiological literature, it is given the name 20:3(n-9). See Fatty Acid#Nomenclature for an explanation of the naming system. In the presence of lipoxygenase
, cytochrome p450 or cyclooxygenase
Mead acid can form various hydroxy (HETE) and hydoperoxy (HpETE) products .
and alpha-linolenic acid
, are considered essential in humans and other mammals. Both are 18 carbon fatty acids unlike mead acid, which has 20 carbons. Linoleic is an ω-6 fatty acid whereas linolenic is ω-3 and mead is ω-9.
Under severe conditions of essential fatty acid deprivation, mammals will elongate and desaturate oleic acid
to make mead acid, (20:3, n−9). This also occurs to a lesser extent in vegetarians and semi-vegetarians.
One study examined patients with intestinal fat malabsorption
and suspected EFA deficiency. They were found to have blood-levels of Mead acid 1263% higher than reference subjects.
) are enzymes known to play a large role in inflammatory processes through oxidation of unsaturated fatty acids. Most notably, the formation of Prostaglandin H2
from arachidonic acid
which is very similar in structure to mead acid. When physiological levels of arachidonic acid are low, other unsaturated fatty acids including mead and linoleic acid are oxidized by COX.
Mead acid is also converted to Leukotrienes C3 and D3.
Omega-9 fatty acid
n−9 fatty acids are a family of unsaturated fatty acids which have in common a final carbon–carbon double bond in the n−9 position; that is, the ninth bond from the end of the fatty acid.-Background:Some n−9s are common components of animal fat and vegetable oil...
, first characterized by James F. Mead. Like some other omega-9 polyunsaturated fatty acid
Polyunsaturated fatty acid
Polyunsaturated fatty acids are fatty acids that contain more than one double bond in their backbone. This class includes many important compounds, such as essential fatty acids and those that give drying oils their characteristic property....
s animals can make Mead acid de novo. Its elevated presence in the blood is an indication of essential fatty acid
Essential fatty acid
Essential fatty acids, or EFAs, are fatty acids that humans and other animals must ingest because the body requires them for good health but cannot synthesize them...
deficiency. Mead acid is found in large quantities in cartilage
Cartilage
Cartilage is a flexible connective tissue found in many areas in the bodies of humans and other animals, including the joints between bones, the rib cage, the ear, the nose, the elbow, the knee, the ankle, the bronchial tubes and the intervertebral discs...
.
Chemistry
Chemically, Mead acid is a carboxylic acidCarboxylic acid
Carboxylic acids are organic acids characterized by the presence of at least one carboxyl group. The general formula of a carboxylic acid is R-COOH, where R is some monovalent functional group...
with a 20-carbon
Carbon
Carbon is the chemical element with symbol C and atomic number 6. As a member of group 14 on the periodic table, it is nonmetallic and tetravalent—making four electrons available to form covalent chemical bonds...
chain and three methylene
Methylene
Methylene is a chemical species in which a carbon atom is bonded to two hydrogen atoms. Three different possibilities present themselves:* the -CH2- substituent group: e.g., dichloromethane ....
-interrupted cis double bonds. The first double bond is located at the ninth carbon from the omega end. In physiological literature, it is given the name 20:3(n-9). See Fatty Acid#Nomenclature for an explanation of the naming system. In the presence of lipoxygenase
Lipoxygenase
Lipoxygenases are a family of iron-containing enzymes that catalyse the dioxygenation of polyunsaturated fatty acids in lipids containing a cis,cis-1,4- pentadiene structure. It catalyses the following reaction:...
, cytochrome p450 or cyclooxygenase
Cyclooxygenase
Cyclooxygenase is an enzyme that is responsible for formation of important biological mediators called prostanoids, including prostaglandins, prostacyclin and thromboxane. Pharmacological inhibition of COX can provide relief from the symptoms of inflammation and pain...
Mead acid can form various hydroxy (HETE) and hydoperoxy (HpETE) products .
Physiology
Two fatty acids, linoleic acidLinoleic acid
Linoleic acid is an unsaturated n-6 fatty acid. It is a colorless liquid at room temperature. In physiological literature, it has a lipid number of 18:2...
and alpha-linolenic acid
Alpha-linolenic acid
α-Linolenic acid is an organic compound found in many common vegetable oils. In terms of its structure, it is named all-cis-9,12,15-octadecatrienoic acid. In physiological literature, it is given the name 18:3 ....
, are considered essential in humans and other mammals. Both are 18 carbon fatty acids unlike mead acid, which has 20 carbons. Linoleic is an ω-6 fatty acid whereas linolenic is ω-3 and mead is ω-9.
Under severe conditions of essential fatty acid deprivation, mammals will elongate and desaturate oleic acid
Oleic acid
Oleic acid is a monounsaturated omega-9 fatty acid found in various animal and vegetable fats. It has the formula CH37CH=CH7COOH. It is an odorless, colourless oil, although commercial samples may be yellowish. The trans isomer of oleic acid is called elaidic acid...
to make mead acid, (20:3, n−9). This also occurs to a lesser extent in vegetarians and semi-vegetarians.
One study examined patients with intestinal fat malabsorption
Malabsorption
Malabsorption is a state arising from abnormality in absorption of food nutrients across the gastrointestinal tract.Impairment can be of single or multiple nutrients depending on the abnormality...
and suspected EFA deficiency. They were found to have blood-levels of Mead acid 1263% higher than reference subjects.
Role in inflammation
Prostaglandin H synthases (also known as COXCox
- People :*Cox , for information on the origins of the family name and a list of people with the name- Places :* Cox, Alicante, Spain* Cox, Florida, United States* Cox, Haute-Garonne, France* Cox Island, Nunavut, Canada...
) are enzymes known to play a large role in inflammatory processes through oxidation of unsaturated fatty acids. Most notably, the formation of Prostaglandin H2
Prostaglandin H2
Prostaglandin H2 is a type of Prostaglandin which is derived from arachidonic acid and is a precursor for many other biologically significant molecules.It is acted upon by:* prostacyclin synthase to create prostacyclin...
from arachidonic acid
Arachidonic acid
Arachidonic acid is a polyunsaturated omega-6 fatty acid 20:4.It is the counterpart to the saturated arachidic acid found in peanut oil, Arachidonic acid (AA, sometimes ARA) is a polyunsaturated omega-6 fatty acid 20:4(ω-6).It is the counterpart to the saturated arachidic acid found in peanut oil,...
which is very similar in structure to mead acid. When physiological levels of arachidonic acid are low, other unsaturated fatty acids including mead and linoleic acid are oxidized by COX.
Mead acid is also converted to Leukotrienes C3 and D3.
See also
- Polyunsaturated fatty acidPolyunsaturated fatty acidPolyunsaturated fatty acids are fatty acids that contain more than one double bond in their backbone. This class includes many important compounds, such as essential fatty acids and those that give drying oils their characteristic property....
– lists of ω-3, -6 and -9 fatty acids; some others. - EicosanoidEicosanoidIn biochemistry, eicosanoids are signaling molecules made by oxidation of twenty-carbon essential fatty acids, ....
- ProstaglandinProstaglandinA prostaglandin is any member of a group of lipid compounds that are derived enzymatically from fatty acids and have important functions in the animal body. Every prostaglandin contains 20 carbon atoms, including a 5-carbon ring....