Lipids 8: Essential Fatty Acids II Flashcards
Where are most EFAs contained?
In phospholipids (n-6»>n-3)
What is a good biomarker of EFAs?
phosphlipids since this is where they are mostly contained
What are examples of EFA biomarkers?
- Platelet & RBC phospholipids (easiest to extract)
- Adipose tissue ~10% EFAs (4-24%) (long term reflection of diet)
- Plasma lipids (Chylomicrons, VLDLs) (indicates diet depending what types of FAs extracted; CM short term; VLDL long term)
- Cheek cell phospholipid DHA and AA: correlated with plasma, RBCs & diet EFAs – excellent biomarker, esp in children
What is the availability of EFA dependant on?
dietary intake!
* ↑consumption changes membrane composition to a certain extent whereas adipose tissue has no limit
What is the FA composition of phospholipid membranes?
organelle specific + influenced by diet
Where are EFAs on phospholipids?
EFAs are absorbed, transported, metabolized and incorporated in the sn-2 position on PPLs
Why are PPLs so heavily influenced by the diet?
PPLs are continuously synthesized & degraded
* head groups & fatty acyl groups can be remodelled making FA available to cell
* phospholipase A1 & A2 hydrolyze sn-1 and sn-2 respectively
What occurs with modifying the FA profile of PPLs?
Results in modified structure & function
What occurs with modifying the FA profile of PPLs?
Results in modified structure & function
What are the main pathways of ecosanoid synthesis?
- cyclooxygenase (COX) pathway: prostaglandins & thromboxanes synthesized via the cyclic pathway
- lipoxygenase (LOX) pathway: leukotrienes by th linear pathway)
What is the general synthesis for ecosanoids?
- binding of a hormone or cytokine to the plasma membrane activates PLA2
- AA released from PPL sn-2 and undergo oxidative reactions via COX or LOX (EPA and DHA too)
- produces ecosanoid which has paracine or autocrine response
Where do ecosanoids act?
Eicosanoids are released into extracellular fluid & act mostly locally on adjacent cells (where synthesized); autocrine (itself) &/or paracrine (cell nearby)
What is the main activity of ecosanoids?
cell-to-cell communication
Extremely potent lipid mediators acting as local messengers via signaling pathways
What are some physiological effect of ecosanoids?
profound physiological effects at very dilute concentrations:
* Inflammatory responses (esp joints, skin, eyes)
* Blood flow and coagulation (vascular function, regulation of blood pressure)
* Pain intensity and fever
* Reproductive function (induction of labour)
* Smooth muscle contraction and relaxation
* Gut health and integrity (inhibition of gastric acid secretion)
What is the difference between COX1 and COX2?
COX1: generates prostaglandins that are involved in the protection of gastrointestinal mucosa (normal maintenance of tissue)
COX2: generates prostaglandins that mediate inflammation and pain in sites throughout the body (acts on substrates)
