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PostPosted: Thu Mar 07, 2024 3:00 pm 
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The omega-6, Linoleic fatty acid has been demonized of late to amazing extents. Researchers seem not to understand that it is vital for our life for many reasons, but mainly as a component of the cellular membrane allowing difussion of oxygen into the cell and mitochondria. Without it, cells suffer hypoxia opening us up to all types of problems, including cancer, etc. Most researchers will deny that this oxygen reversibility of cis-LA happens, but there are several studies that seem to prove other wise. Below is one from 2009:

Quote:
Mol Nutr Food Res. Author manuscript; available in PMC 2010 May 12.
Published in final edited form as:
Mol Nutr Food Res. 2009 Mar; 53(3): 315–321.
doi: 10.1002/mnfr.200800131
PMCID: PMC2868362
NIHMSID: NIHMS200637
PMID: 19006094
An update on products and mechanisms of lipid peroxidation
Claus Schneider

The initial hydrogen abstraction from the pentadiene is essentially irreversible and commits the fatty acid to a reaction with oxygen one way or other. In the case of linoleic acid, hydrogen abstraction occurs at the methylene group (C11) in between the 9,10cis and 12,13cis double bonds and gives a fatty acid radical (pentadienyl radical) that is delocalized over carbons 9 through 13 (Fig. 3, step 1) [12]. Addition of oxygen to the carbon-centered radical is “diffusion-controlled” meaning that it is exceedingly fast, and the rate of reaction is only limited by how fast oxygen can get to the fatty acid radical; but there is essentially no energy barrier for formation of the peroxyl radical (step 2) [13]. (This is true for addition of oxygen to all three carbons 9, 11, and 13, but in this section we will only consider formation of the conjugated hydroperoxides 9-HPODE and 13-HPODE.) The reaction with oxygen is reversible, such that the peroxyl radical can lose O2 and revert back to the carbon radical. This reaction of the peroxyl radical is called β-fragmentation since the bond that breaks is in β-position to where the radical is located [14]. Still, depending on the reaction conditions, peroxyl radicals have a considerable half life which ranges from milliseconds to seconds, opening up the possibility to follow different reaction pathways [15]. Competing with β-fragmentation is the trapping of the peroxyl radical as the hydroperoxide product by transfer of a hydrogen atom, i.e., the peroxyl radical abstracts a hydrogen atom from an available bis-allylic methylene group (step 3). This is the rate-limiting (i.e., slowest) step of the radical reactions during autoxidation [12]. Nevertheless, it is the dominating reaction for the peroxyl radical during the early stages of autoxidation, and it is the step that propagates the chain by passing the radical on to the next molecule of fatty acid.


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Another paper writes:

Paquette, D.B. Kupranycz, F.R. van de Voort,
The Mechanisms of Lipid Autoxidation I. Primary Oxidation Products,
Canadian Institute of Food Science and Technology Journal,
Volume 18, Issue 2,
1985,

The Mechanisms of Lipid Autoxidation I. Primary Oxidation Products



Quote:
It is somewhat surprising that the possibility of the reversible oxygen addition proposed for linoleic and linoleic hydroperoxides (Porter et al., 1980, 1981; Potter and Wujek 1984; Chan et al., 1979, 1982; Coxon et al, 1981; Bascetta et al, 1983) has not been proposed for oleic acid. In a paper on linoleate hydroperoxide rearrangement, Chan et al. (1979) mentioned the fact that oleate hydroperoxide did rearrange, possibly by a similar mechanism, but this avenue does not seem to have been pursued.


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reversibility in oxygen uptake is necessary for proper oxygenation of the tissues. A 1974 study (Campbell, I.M., Caton, R.B. & Crozier, D.N. Lipids (1974) 9: 916. https://doi. org/10.1007/BF02532619) found that:
Quote:
". . . prior to true oxidation, unsaturated fatty acids undergo an oxygenation which is reversible in response to changes in oxygen pressure. The oxygenation seems to result from the oxygen molecule having a specific affinity for pairs of olefinic bonds."


Olefinic bonds, as described here, are the unsaturated hydrocarbon that contains a carbon-carbon double bond as is characteristic of unsaturated fatty acids. In short, this study suggests that the oxygen-carrying reversibility of linoleic acid is a fact.

A 1976 study (Campbell & Crozier, Abnormal fatty acid composition and impaired oxygen supply in cystic fibrosis patients, Pediatrics. 1976 Apr;57(4):480-6.) supports how important the two double-bonded structure characteristic of linoleic acid (linoleates) was in the membrane of red blood cells (erythrocytes) when compared to oleic acid (Oleates found in many modern seed oils) which has one double-bond (a monounsaturated fatty acid). It would be presumed that the three double-bonds found in the Omega-3, linolenic acid, would likewise be too reactive to perform properly in oxygen transfer. This study involves Cystic fibrosis patients who all typically show reduced circulating levels of linoleic acid levels in their red blood cells. It may logically be assumed that the reduced linoleic levels observed in red blood cells would equate with reduced levels in other tissues found in the body.

Quote:
"Impaired oxygen supply and deteriorating health, in cystic fibrosis patients, correlates with abnormal changes in the fatty acid composition of blood lipids. As the proportion of oleates increases and that of linoleates decreases, erythrocyte membrane interference with the formation of intracellular oxyhemoglobin increases and arterial oxygen pressure decreases. The physical-chemical basis for these changes seems to be that oleic and linoleic acid differ in their ability to undergo reversible oxygenation in response to changes in oxygen pressure. The oxygen complex of linoleic acid dissociates at relatively high pressures, whereas that of oleic dissociates only at low pressures. Accordingly, excessive substitution of oleic for linoleic acid in membrane lipids would be expected to decrease the intra-cellular oxygen pressure to a level where hemoglobin oxygenation and any other oxygen-requiring processes would be impaired."

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