Arachidonic acid
From Wikipedia, the free encyclopedia
| Arachidonic acid | |
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| IUPAC name |
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| Identifiers | |
| CAS number | [] |
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| Properties | |
| Molecular formula | C20H32O2. |
| Molar mass | 304.5 g/mol |
| Melting point |
-49.5 °C |
| Boiling point |
°C (dec.) |
| Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa) Infobox references |
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Arachidonic acid (AA, sometimes ARA) is an omega-6 fatty acid 20:4(ω-6). It is the counterpart to the saturated arachidic acid found in peanut oil, (L. arachis – peanut.)[1]
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[edit] Chemistry
In chemical structure, arachidonic acid is a carboxylic acid with a 20-carbon chain and four cis double bonds; the first double bond is located at the sixth carbon from the omega end.
Some chemistry sources define 'arachidonic acid' to designate any of the eicosatetraenoic acids. However, almost all writings in biology, medicine and nutrition limit the term to all-cis 5,8,11,14-eicosatetraenoic acid.
[edit] Biology
Arachidonic acid is a polyunsaturated fatty acid that is present in the phospholipids (especially phosphatidylethanolamine, phosphatidylcholine and phosphatidylinositides) of membranes of the body's cells, and is abundant in the brain.
In addition to being involved in cellular signaling as a lipid second messenger involved in the regulation of signaling enzymes, such as PLC-ɣ, PLC-δ and PKC-α, -β and -ɣ isoforms, arachidonic acid is a key inflammatory intermediate. [2] (Note separate synthetic pathways, as described in section below)
[edit] Synthesis and cascade
Arachidonic acid is freed from a phospholipid molecule by the enzyme phospholipase A2 (PLA2), which cleaves off the fatty acid, but can also be generated from DAG by DAG lipase. [2]
Arachidonic acid generated for signaling purposes appears to be derived by the action of a phosphatidylcholine-specific cytosolic phospholipase A2 (cPLA2, 85 kDa), whereas inflammatory arachidonic acid is generated by the action of a low-molecular-weight secretory PLA2 (sPLA2, 14-18 kDa). [2]
Arachidonic acid is a precursor in the production of eicosanoids:
- the enzymes cyclooxygenase and peroxidase lead to Prostaglandin H2, which in turn is used to produce the prostaglandins, prostacyclin, and thromboxanes.
- the enzyme 5-lipoxygenase leads to 5-HPETE, which in turn is used to produce the leukotrienes.
- arachidonic acid is also used in the biosynthesis of anandamide.
- some arachidonic acid is converted into hydroxyeicosatetraenoic acids (HETEs) and epoxyeicosatrienoic acids (EETs) by epoxygenase. [3]
The production of these derivatives and their action in the body are collectively known as the arachidonic acid cascade; see essential fatty acid interactions for more details.
[edit] PLA2 activation
PLA2, in turn, is activated by ligand binding to receptors, including:
Furthermore, any agent increasing intracellular calcium may cause activation of some forms of PLA2.[5]
[edit] PLC activation
Alternatively, arachidonic acid may be cleaved from phospholipid by phospholipase C (PLC), yielding diacylglycerol (DAG), which subsequently is cleaved by DAG lipase to yield arachidonic acid. [4]
Receptors that activate this pathway include:
PLC may also be activated by MAP kinase. Activators of this pathway include PDGF and FGF.[5]
[edit] Explaining its Role in Muscle Anabolism
One of the lead researchers in the Baylor study on arachidonic acid, Mike Roberts MS, CSCS, has authored an article published under the title Arachidonic Acid, The New Mass Builder explaining the potential role of this nutrient in muscle anabolism. [1].
'"From a bird's eye perspective, the concept of the "no pain, no gain" paradigm is simple: a training stimulus that does not elicit localized inflammation and soreness will not yield optimal muscle growth. So, what about arachidonic acid's role in muscle inflammation? Well for starters, arachidonic acid (AA, 20:4n-6) is an essential Omega-6 (1-6) polyunsaturated fatty acid that is abundant in skeletal muscle membrane phospholipids (figure 2). It is also the body's principle building block for the production of prostaglandins, which are known to have various physiological roles including a close involvement in inflammation.
Furthermore, recent evidence suggests that the prostaglandin isomer PGF2a has a potent ability to stimulate muscle growth. As such, arachidonic acid is a regulator of localized muscle inflammation, and may be a central nutrient controlling the intensity of the anabolic/tissue-rebuilding response to weight training."
[edit] Essential fatty acid
Arachidonic acid is one of the essential fatty acids required by most mammals. Some mammals lack the ability to—or have a very limited capacity to—convert linoleic acid into arachidonic acid, making it an essential part of their diet. Since little or no arachidonic acid is found in plants, such animals are obligate carnivores; the cat is a common example.[6][7]
[edit] Metabolic defect possible link to Alzheimer's disease
Arachidonic acid intake in the diet is not known to be a cause of Alzheimer's disease. Research based on feeding arachidonic acid to mice, however, suggests a possible link between defective ArA metabolism in affected individuals and progression of the disease. Alzheimer's disease.[8]
[edit] Use in Bodybuilding
Arachidonic acid is marketed under patent (#6,841,573) as an anabolic bodybuilding supplement in products such as X-Factor (Molecular Nutrition), Halodrol Liquigels (Gaspari Nutrition), Animal Test (Universal Nutrition), Hemodraulix (Axis Labs), Mass Caps (IDS), Max Out (iForce), and Thermaphoria (EST Nutrition). The first clinical study concerning the use of arachidonic acid as a sport supplement was conducted at Baylor University and published in the 'Journal of the International Society of Sports Nutrition'. The conclusion of the study reads: "AA supplementation during resistance-training may enhance anaerobic capacity and lessen the inflammatory response to training. However, AA supplementation did not promote statistically greater gains in strength, muscle mass, or influence markers of muscle hypertrophy."
The performance data results from the paper include the following statistically significant improvement, and statistically strong trends:
"A significant group × time interaction for relative Wingate peak power was observed among groups (P = 0.02) with gains in peak power being significantly greater in the AA group (0.3 ± 1.2 W·kg-1) vs. PLA (0.2 ± 0.7 W·kg-1, Figure 1). Using repeated measures ANOVA with delta scores, AA experienced significantly greater increases in comparison to the PLA group at day 50 (P < 0.05). Statistical trends were seen in Wingate total work (AA: 1,292 ± 1,206 vs. PLA: 510 ± 1,249 J, P = 0.09, ηp 2 = 0.052), favoring the AA group."
WIth regard to inflammation, the paper reported a statistiically significant reduction as measured by IL-6:
"IL-6 levels experienced a significant group × time interaction (P = 0.04) among groups with subsequent post-hoc analyses revealing that IL-6 was significantly lower at day 25 of the study. One way ANOVA of IL-6 delta values at day 25 revealed significantly greater increases in PLA when compared to AA group (AA: 0.8 ± 13.5 pg·ml-1 vs. PLA: 52.5 ± 1.6 pg·ml-1, P = 0.01; Figure 2)"
While many of the performance variables failed to reach statistical significance, arachidonic acid was shown to improve peak muscle power, reduce systemic inflammation, and produce statistically strong trends of improvements in muscle endurance, average power, and bench press 1-rep maximum lift, suggesting a definite role in muscle metabolism and performance.
[http://www.jissn.com/content/pdf/1550-2783-4-21.pdf Effects of arachidonic acid supplementation on training adaptations in resistance-trained males]
[edit] See also
- Polyunsaturated fat
- Polyunsaturated fatty acid
- Aspirin - inhibits cyclooxygenase enzyme to prevent the conversion of arachidonic acid to other signal molecules
[edit] References
- ^ "Dorland's Medical Dictionary – 'A'". http://www.mercksource.com/pp/us/cns/cns_hl_dorlands.jspzQzpgzEzzSzppdocszSzuszSzcommonzSzdorlandszSzdorlandzSzdmd_a_56zPzhtm. Retrieved on 2007-01-12.
- ^ a b c Baynes, John W.; Marek H. Dominiczak (2005). Medical Biochemistry 2nd. Edition. Elsevier Mosby. p. 555. ISBN 0723433410.
- ^ Page 108 in: Walter F., PhD. Boron (2003). Medical Physiology: A Cellular And Molecular Approaoch. Elsevier/Saunders. pp. 1300. ISBN 1-4160-2328-3.
- ^ a b c d e f Walter F., PhD. Boron (2003). Medical Physiology: A Cellular And Molecular Approaoch. Elsevier/Saunders. pp. 1300. ISBN 1-4160-2328-3. Page 103
- ^ a b c d e f Walter F., PhD. Boron (2003). Medical Physiology: A Cellular And Molecular Approaoch. Elsevier/Saunders. pp. 1300. ISBN 1-4160-2328-3. Page 104
- ^ MacDonald M, Rogers Q, Morris J (1984). "Nutrition of the domestic cat, a mammalian carnivore". Annu Rev Nutr 4: 521–62. doi:. PMID 6380542. http://nutr.annualreviews.org/doi/abs/10.1146/annurev.nu.04.070184.002513. Retrieved on 2007-02-09.
- ^ Rivers J, Sinclair A, Crawford M (1975). "Inability of the cat to desaturate essential fatty acids". Nature 258 (5531): 171–3. doi:. PMID 1186900. http://www.nature.com/nature/journal/v258/n5531/abs/258171a0.html.
- ^ The Press Association Fatty acid 'link' to Alzheimer's 19 October 2008
[edit] External links
- Arachidonic Acid at acnp.org
- MeSH Arachidonic+Acid
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