Cell study: more arachidonic acid, more muscle growth
William Llewellyn was right. About ten years ago Llewellyn came up with the theory that the fatty acid arachidonic acid might just be a key factor in muscle growth. Llewellyn launched a supplement containing arachidonic acid on the market, and financed a study which, although it didn't discover any anabolic effects, did show that the substance enhances performance levels. But arachidonic acid probably does have an anabolic effect too, according to researchers at the University of Auckland in New Zealand.
The body converts the n-6 fatty acid linoleic acid into gamma-linolenic acid, or GLA, which is then converted into arachidonic acid. Arachidonic acid in turn is a precursor of hormone-like signal substances such as PGE2 and PGF2a. The diagram below shows how this all works.
Arachidonic acid has a bad reputation. The fatty acid, or rather, its metabolites are believed to whip up inflammation, and are therefore regarded as being responsible to the negative effects of a diet containing too much n-6 fatty acids. Llewellyn has always maintained that the story isn't as simple as that. Some metabolites of arachidonic acid actually inhibit inflammation. [vpxsports.com January 4, 2013]
Seven years ago Llewellyn's company Molecular Nutrition sponsored a study in which young strength athletes were given arachidonic acid. Their anaerobic capacity increased dramatically, although they didn't become more muscular. In January 2013 a New Zealand PhD researcher James Markworth published the results of an in-vitro study which showed that Llewellyn's theory does seem to hold water.
Markworth exposed C2C12 muscle cells to various concentrations of arachidonic acid. The higher the concentration, the thicker the muscle fibres were that the cells forms and the more muscle protein they manufactured.
Exposure to arachidonic acid inhibited the increase in the total number of muscle fibres, the figure above shows. Click on it for a larger version. Dark bars = muscle cells that were exposed to arachidonic acid.
On the right above you can see that arachidonic acid caused an increase in the number of larger muscle fibres – ones with more than five cell nuclei. That means that arachidonic acid causes muscle fibres to become bigger.
The researchers repeated their experiments with compounds that inhibit the COX-2 enzyme. COX converts arachidonic acid into PGE2. By blocking this almost all of the anabolic effect of arachidonic acid was taken away. Experiments with a non-metabolisable version of arachidonic acid produced no results either.
"The findings of the present study show that an increased availability of free arachidonic acid and subsequent metabolism by the COX-2 pathway have a net stimulatory effect on in vitro skeletal muscle cell growth", the researchers conclude.
Am J Physiol Cell Physiol. 2013 Jan 1;304(1):C56-67.
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