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Pump It Up With GPLC and NO

Perhaps some of the more exciting avenues of research regarding NO and the potential benefits of GPLC are in the area of skeletal muscle satellite cells, which hover around muscle fibers.

First off, don’t confuse nitric oxide with nitrous oxide, which is an anesthetic. You might know nitrous oxide as laughing gas. Okay, now that you know we’re not talking about laughing gas, let’s get down to the business of nitric oxide, or NO.

What is NO? It’s a key molecule that is manufactured in the body and plays numerous roles in nearly all physiological systems. In the cardiovascular system it is a vasodilator, which means it expands the internal diameter of blood vessels. Vasodilation leads to an increase in blood flow, oxygen transport and delivery of nutrients to surrounding tissue, including skeletal muscle. That’s why you’ll see NO products touted as “giving you a pump like you’ve never felt before!” Or, “it’ll give you such a pump ‘down under’ that your girlfriend, wife or both will be begging for more.” Okay, perhaps not, but you get the picture. Most NO supplements are a mix of L-arginine powder and alpha-ketoglutaric acid; however, the newest kid on the block is glycine propionyl-L-carnitine, or GPLC.

We know that taking GPLC increases plasma nitrate/nitrite—a.k.a. NOx—a surrogate measure of nitric oxide production. In a university investigation that used a double-blind crossover design, 15 healthy men, 24 years of age, were given GPLC and a placebo for four weeks each, with a two-week washout between supplement assignments. Blood samples were taken from subjects at rest and at 0, three and 10 minutes following an ischemia-reperfusion protocol—six minutes of upper-arm cuff occlusion at 200 mmHg followed by rapid reperfusion with cuff removal. Don’t try it at home, kids.

An ischemia-reperfusion protocol is a model that scientists use to study damage caused by blocking blood flow (the ischemia part) then subsequently reflowing it (the reperfusion part). Odd but true: Tissue damage is caused by both ischemia and the reperfusion. An early event during reperfusion is the development of what scientists call endothelial dysfunction. The bioavailability of the endothelium-derived vasodilator nitric oxide rapidly diminishes during reperfusion, due to either decreased production or enhanced inactivation of NO by superoxide. That, in turn, may contribute to the injury to tissues seen during the protocol.

Scientists analyzed blood samples for total nitrate/nitrite. Eleven of the 15 subjects experienced an increase in NOx with GPLC treatment. The researchers concluded that short-term oral GPLC supplementation can increase NOx in resistance-trained men. What’s intriguing is that the study showed both responders and nonresponders to treatment. You see that even with creatine monohydrate—the issue of response and nonresponse. What’s fascinating about the effects of GPLC is its potential to elevate NO perhaps more than any other ingredient. Its potential effect on satellite cells may be the next avenue of GPLC research.

The leading studies so far have come from the University of Memphis lab headed by Dr. Rick Bloomer. He’s discovered that GPLC can increase blood levels of NOx at a daily dosage of 4.5 grams. Also, folks taking GPLC had lower levels of “oxidant stress,” likely due to its potent antioxidant properties. Some subjects have even experienced a slight decrease in blood triglycerides, which, of course, has dramatic implications for cardiovascular disease risk. An eight-week study showed that GPLC has no untoward effects.

Perhaps some of the more exciting avenues of research regarding NO and the potential benefits of GPLC are in the area of skeletal muscle satellite cells, which hover around muscle fibers. Typically activated in response to muscle fiber damage, exercise and stretching, they can fuse to form new muscle fibers—muscle fiber hyperplasia, fuse with existing muscle fibers to make even bigger ones—muscle fiber hypertrophy, or help repair damaged muscle fibers.

Moreover, there is scientific evidence to show that NO assists the activation of satellite cells, which can occur within one minute of injury. The perfect blend of ingredients in a supplement might include GPLC and creatine monohydrate, potential activators of satellite cells. Add some arginine to further enhance the NO effect, and top it off with the essential amino acids for promoting dramatic increases in muscle protein synthesis, beta-alanine to enhance exercise capacity during superintense exercise and some phosphatidylserine and alpha-GPC to help focus your noggin on the task at hand, and you have a muscle-building combination second to none.

Editor’s note: Jose Antonio, Ph.D., is a writer, teacher, radio host and frequent speaker on the subject of sports supplements. Go to for more information.


1 Bloomer, R.J., et al. (2007). Glycine propionyl-L-carnitine increases plasma nitrate/nitrite in resistance trained men. J Int Soc Sports Nutr. 4:22.
2 Anderson, J.E. (2000). A role for nitric oxide in muscle repair: Nitric oxide-mediated activation of muscle satellite cells. Mol Biol Cell. 11:1859-74.
3 Wozniak, A.C., and Anderson, J.E. (2007). Nitric oxide-dependence of satellite stem cell activation and quiescence on normal skeletal muscle fibers. Dev Dyn. 236:240-50.

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