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In biochemistry, eicosanoids (preferred IUPAC name icosanoids) are signaling molecules made by oxidation of 20-carbon fatty acids. They exert complex control over many bodily systems; mainly in growth during and after physical activity, inflammation or immunity after the intake of toxic compounds and pathogens, and as messengers in the central nervous system. The networks of controls that depend upon eicosanoids are among the most complex in the human body. Eicosanoids are derived from either omega-3 (ω-3) or omega-6 (ω-6) fatty acids. In general, the ω-6 eicosanoids are pro-inflammatory; ω-3s are much less so. The amounts and balance of these fats in a person's diet will affect the body's eicosanoid-controlled functions, with effects on cardiovascular disease, triglycerides, blood pressure, and arthritis. There are multiple subfamilies of eicosanoids, including the prostaglandins, thromboxanes, and leukotrienes, as well as the lipoxins and eoxins, and others. For each, there are two or three separate series, derived from either an ω-3 or an ω-6 EFA. These series' different activities largely explain the health effects of ω-3 and ω-6 fats. ==Nomenclature== :''See related detail at Essential Fatty Acid Interactions—Nomenclature'' "Eicosanoid" (''eicosa-'', Greek for "twenty"; ''see icosahedron'') is the collective term for oxygenated derivatives of three different 20-carbon fatty acids: *Eicosapentaenoic acid (EPA), an ω-3 fatty acid with 5 double bonds; *Arachidonic acid (AA), an ω-6 fatty acid, with 4 double bonds; *Dihomo-gamma-linolenic acid (DGLA), an ω-6, with 3 double bonds. Current usage limits the term eicosanoid to leukotrienes (LT), eoxins (EX), and three types of prostanoids—prostaglandins (PG), prostacyclins (PGI) and thromboxanes (TX). This is the definition used in this article. However, several other classes can technically be termed eicosanoid, including the hepoxilins, resolvins, isofurans, isoprostanes, lipoxins, epi-lipoxins, epoxyeicosatrienoic acids (EETs) and endocannabinoids. LTs and prostanoids are sometimes termed 'classic eicosanoids' in contrast to the 'novel', 'eicosanoid-like' or 'nonclassic eicosanoids'. A particular eicosanoid is denoted by a four-character abbreviation, composed of: * Its two-letter abbreviation (above),〔Prostacyclin—PGI—was previously classified as prostaglandin and retains its old identifier.〕 *One A-B-C sequence-letter;〔Eicosanoids with different letters have placement of double-bonds and different functional groups attached to the molecular skeleton. Letters indicate roughly the order the eicosanoids were first described in the literature. For diagrams for PG () see (【引用サイトリンク】author=Cyberlipid Center )〕 and *A subscript, indicating the number of double bonds. Examples are: * The EPA-derived prostanoids have three double bonds, (e.g., PGG3, PGH3, PGI3, TXA3) while its leukotrienes have five, (LTB5). *The AA-derived prostanoids have two double bonds, (e.g., PGG2, PGH2, PGI2, TXA2) while its leukotrienes have four, (LTB4). Furthermore, stereochemistry may differ among the pathways, indicated by Greek letters, e.g. for (PGF2α). 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「eicosanoid」の詳細全文を読む スポンサード リンク
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