Learning the triggers for protein synthesis has been a big focus for the scientific community of late. A recent study in Nutrition & Metabolism took a look at what might seem like an unlikely candidate for a muscle-boosting supplement.
Phosphatidic acid is a part of what’s known as a phospholipid (pictured above), the kind of lipid that makes up your cell membranes and is critical for life. In addition to being a major structural component of the human body, phosphatidic acid is also a signaling molecule, which means its presence can make things happen in your body.
Specifically, phosphatidic acid is known to interact with proteins and their biochemical pathways. One important pathway it affects is mTOR. If that sounds familiar, it’s because mTOR is a protein that triggers protein synthesis and induces hypertrophy. When we work out, the fibers that receive the mechanical stimulus of an external load trigger the release of phosphatidic acid inside the cells. This increase stimulates the mTOR pathway, which causes the growth and repair of muscle.
While the effects of exercise on phosphatidic acid and mTOR are known, there are still a lot of question marks that need to be worked out. For example, it’s possible that some metabolite of phosphatidic acid interacts with mTOR, rather than the acid itself. The researchers in this study wanted to know whether or not supplemental phosphatidic acid would stimulate growth, and exactly how it worked.
Study Design
The study was conducted in two phases. During the first phase, the research team tested multiple phospholipids that are associated with phosphatidic acid, as well as their metabolic precursors for effects on mTOR. During the second phase, the subjects took supplemental phosphatidic acid to see if their workout results were better than without it.
The first phase took place in a petri dish. Cells in the dish were introduced to phosphatydic acid derived from egg, soy, or a host of other related molecules derived from soy. The cells that worked for signaling mTOR were phosphatydic acid from both egg and soy, phosphatidylserine, and lysophosphatidic acid. The egg phosphatidic acid boosted mTOR signaling by 221%, but that paled in comparison to some of the others. Soy-based phosphatidic acid boosted mTOR signaling by 636%. The lysophosphatidic acid performed about the same, followed by the phosphatidylserine, which was at a little under 600%.
So various metabolites of phosphatidic acid work in a petri dish, but what about when we take them as a supplement? To answer that question, the researchers analyzed samples from 28 men who participated in the study. Half of the subjects took a phosphatidic acid supplement and half took a placebo. They worked out three days per week for eight weeks, using a variety of exercises designed to train the whole body. The program they used was a mixed program, utilizing sets of one rep all the way to twelve reps and varying the length of the rest periods. The supplement group consumed 750mg of phosphatidic acid each day.
Results
In the end, the supplement group gained five pounds more than the non-supplement group, had a larger rectus femoris muscle by one centimeter, and had a 114lb-higher leg press strength than the placebo group. Those are large differences over just eight weeks, especially when the other group was working out as well.
It should be noted that two of the authors are patent holders in the company that produces the supplement used in the study. This doesn’t invalidate it, mind you, but it does introduce some bias that future research will hopefully eliminate. As it stands now, the mTOR pathway does indeed seem to be activated not only by phosphatidic acid in its natural form, which we already knew, but also by supplemental phosphatidic acid.
References:
1. Joy et al. “Phosphatidic acid enhances mTOR signaling and resistance exercise induced hypertrophy,” Nutrition & Metabolism 2014, 11:29
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