Wednesday, April 6, 2011

Linoleic Acid and Pain

Heat generates oxidized linoleic acid metabolites that activate TRPV1 and produce pain in rodents:

"...Our data demonstrate, for what we believe is the first time, that oxidized linoleic acid metabolites constitute a family of endogenous TRPV1 ligands that are released under physiological conditions in the periphery. The activation of TRPV1 may explain the role of these metabolites in inflammatory or degenerative diseases such as arthritis, atherosclerosis, and psoriasis (22–23, 28). In rat and mouse TG neurons, the excitatory effect of 9-HODE and 9-oxoODE was almost entirely dependent on the presence of TRPV1. Thus, it is conceivable that oxidized linoleic acid metabolites may be formed by heat or even other stimuli (29) and contribute to ongoing pain or hyperalgesia in inflammatory diseases. This hypothesis suggests that agents blocking either the production or action of these substances could lead to pharmacological interventions for many inflammatory diseases or pain disorders. Indeed, our recent studies demonstrate efficacy of such an approach in blocking TRPV1-mediated central sensitization in the spinal cord (7).

"Previous studies have demonstrated that leukotrienes activate TRPV1, epoxyeicosatrienoic acids activate TRPV4, and 4-hydroxynonenal and 15d-PGJ2 activate TRPA1 (30–32). Our results add HODEs as endogenous ligands for TRPV1. It is noteworthy that all these TRP ligands are lipid oxidation products. It is therefore tempting to speculate that one of the major roles of certain TRP channels in mammals is to act as sensors of membrane lipid oxidation as a surrogate for cellular damage."
Therefore:

"...These data collectively reveal a mechanism by which an endogenous family of lipids activates TRPV1 in the spinal cord, leading to the development of inflammatory hyperalgesia. These findings may integrate many pain disorders and provide an approach for developing analgesic drugs."

Wow. Is there nothing linoleic acid can't do? (Oxidized linoleic acid is also known as heated vegetable oils.)

Of course this is speculation and hypothesis, and I already avoid eating the stuff, so I can be cavalier...

I will note that since these are scientists who must find funding to do research, their response to these findings are to suggest that drugs may be developed to block this process.  This is the insanity of the modern "iron triangle" of the Modern American Diet: eat food that makes you sick (the food industry); so that the researchers can figure out why you're getting sick (institutional science); then you can take a drug that sort of works at blocking the effects of the poison (er, the drug companies).  If you stop doing the first part, you can skip the drama of the other two sides of the triangle (for the most part, anyway).

(One of my little hobbies in the diet arena involves googling for various diseases and cross-referencing the terms "wheat", "gluten", and "linoleic acid".  In this case the search I used was "oxidised linoleic acid".)