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What are eicosanoids?
biologically active 20c fatty acids
What prostanoids are made from them?
prostaglandins
thromboxanes
leukotrienes
What do these substances do?
act locally as paracrines via g-protein linked cellular receptors
usu cGMP
What are the three series of eicosanoids?
1: linoleic
2: alpha linolenic
3: arachidonic
Which one of the three is conditionally essential?
arachidonic
meat eaters get plenty in diet
can be synthesized from DHGLA in series I if enzyme pathway intact
Each series gives rise to its own set of prostaglandins, leukotrienes and thromboxanes.
Code for those are PG1, LK2, TX3, etc.
Series 2 mostly inflammatory, series 1 & 3 mostly antiinflammatory.
SERIES 1
linoleic acid
omega-6
found in vegetables, seeds, nuts
converted by delta-6 desaturase-->gamma-linolenic (GLA)-->DHGLA-->series 1 cytokines
delta-6 desaturase inhibited by trans fats, stimulated by insulin
GLA found in EPO, borage, black currant???
enzyme for DHGLA-->PG1, TX1 and LK1 is cox or lipox
anti-inflammatory
DHGLA can convert to series 2 which is why arachidonic conditionally essential
SERIES 2
arachidonic acid
sources: animal fats
delta-5 desaturase stim by insulin, blocked by EPA, DHA, glucagon
What is PLA-2?
phospholipase A2
removes lipids from phospholipid bilayer that is the cell membrane
generates arachidonate
What stimulates phospholipase A2?
angiotensin 2, bradykinin, epi, thrombin
What inhibits phospholipase A2?
corticosteroids
What does lipoxygenase make from arachidonate?
leukotrienes
What does cyclo-oxygenase make from arachidonate?
PGs and TXs
What inhibits cyclo-oxygenase?
NSAIDS
SERIES 3
alpha-linolenic acid
omega 3
sources: seed oils: walnuts, flaxseed, perilla, chia, hemp, also green leaves
delta-6 desaturase blocked by stress hormones, age, cancer, stim by B6, Mg, Zn
inhibited by trans fats
alpha linolenic-->EPA-->DHA-->PG, TX, LK 3
EPA in salmon, herring, mackerel