Monday, February 27, 2012

+25% Increased Quadriceps Weight and Profound Increases in Vascularization in Rodents From Real NO Donor! Study Shows: Nitric Oxide Works, At Least in Old Mice

Image 1: This is what NO boosters
promise, yet mostly don't deliver.
Many people believe that there is some truth to every myth. And in fact, a recently published study rom the Department of Surgery, Biological Sciences and Human Anatomy & Cell Science (quite a mouthful) at the University of Manitoba in Winnipeg, Canada, shows that even there may be a quantum of truth even in the "arginine" or "nitric oxide" or "pre-workout" or "however else you may want to call it" myth, which says that getting a decent pump will help you build muscle (Leiter. 2012). Now, aside from the fact that the latest generation of those pre-workout supplements boasts of having no arginine in them and relies solely on the stimulant rush the various *amines in them will produce, there is not a single study in which supplementation with X, Y, or Z amount of l-arginine (or other forms of the alpha-amino acid) had produced greater increases in skeletal muscle hypertrophy than an iso-nitrious (equal amount of nitrogen) placebo.

If arginine does not work, this does not mean that NO does not work either!

Those of you who have listened to my dissertation on amino acids, in the Amino Acids For Super Humans series on Carl Lanore's Super Human Radio, will yet probably remember that I mentioned a couple of test-tube studies, in which the incubation of intact myotubes with high amounts of l-arginine induced a profound growth response. Moreover, slightly more recent evidence from the Center of Exercise Science at the University of Florida points to the involvement of nitric oxide in the release of PGC-alpha, about the far-reaching metabolic effects (increase in mitochondrial density, effectivity and via irisin "browning of the fat cells", cf. PGC-alpha, irisin) you have read several times, already, here at the SuppVersity - and, as of late, probably even heard of in mainstream media.

Image 2: MP Assault is currently #2 in the Top 50 Best Selling Products over at,  it is yet only 1/3 purported NO-boosters in the Top 10
That those in-vitro results did not yet translate into real-world gains among the millions of consumers who have bought truckloads of NO XPlodes and SuperPumps over the past couple of years, is simple: While our bodies are capable of producing nitric oxide from arginine, simply taking in more than you need, won't increase your total and even less the nitric oxide level in your skeletal muscle tissue to a degree that would have physiological effects beyond "feeling pumped" (and I guess most of you will have noticed that especially on low carbohydrate diets, even this cosmetic effect is oftentimes absent when you consume one of the so called "NO boosters").

Isosorbide dinitrate, a real NO booster

In their study, Jeff R.S. Leiter and his colleagues did not even bother with l-arginine, but chose a pharmacological NO donor, which is usually prescribed to patients suffering from angina pectoris: Isorsorbide dinitrate, a long acting form of nitrates that is sold under the brand names Isordil, Cedocard, Sorbitrate, etc. To evaluate whether the administration of this medication could help combating the age-induced decline in satellite cell activation and subsequent loss of skeletal muscle mass, the scientists treated 18-months old female C57BL/6 mice (in human terms those mice were grannies) with either 66mg/kg isosorbide dinitrate (human equivalent: 5mg/kg) or placebo for 6 weeks. In addition to the "supplementation", half of the mice had free access to one of those tiny wheels, of which mice - contrary to the lazy human beings for whom they are used as a model - usually avail themselves voluntarily. Altogether, this leaves us with 4 groups:
  1. Control group: no wheel running, no NO donor
  2. Exercise group: access to wheel, no NO donor
  3. Treatment group: no access to wheel, 66mg/kg isosorbide dinitrate
  4. T + EX: access to wheel, 66mg/kg isosorbide dinitrate
As you can see in figure 1 the "gains" the old mice made, were far from being earth-shattering, but in view of the fact that they only ran whenever they wanted to (unfortunately there is not data on the exact time the rodents spent on the wheel) an increase in quadriceps weight of +25% over the control group and still +8% over the "exercise-only" group is certainly worth mentioning.
Figure 1: Muscle weight of skeletal muscle of exercised and/or isosorbide dinitrate treated 18-months old mice after 6-weeks (data adapted from Leiter. 2012)
That being said, the increases in muscle DNA synthesis and the VEGF (vascular endothelial growth factor) induced increase in vascular density are probably way more remarkable than the non-negligible increase in muscle weight, anyways.
Figure 2: DNA synthesis and vascular density in skeletal muscle of exercised and/or isosorbide dinitrate treated 18-months old mice after 6-weeks (data adapted from Leiter. 2012)
After all, the angiogenic effects of VEGF and the subsequent permanent (not cosmetic ;-) improvements in capilarization do not only facilitate an improved nutrient delivery to the muscle, the expansion of the "nutrient supply grid" is also a necessary prerequisite for future muscle growth.

Would the combination of an effective NO donor with leucine/HMB work even better?

What is yet interesting, though is that in those "old ladies" the exercise induced skeletal muscle protein synthesis obviously could not keep pace with the increase in DNA expression.
Figure 3: Mean fiber diameter and protein synthesis in skeletal muscle of exercised and/or isosorbide dinitrate treated 18-months old mice after 6-weeks (data adapted from Leiter. 2012)
The decrease in DNA/protein ratio, as well as the non-significant increase in fiber diameter (cf. figure 3) certainly raise the question, whether the additional provision of a significant amount of leucine or - in view of previous promising results in elderly populations - HMB would not result in significantly more pronounced gains in skeletal muscle mass. After all, it seems that the incorporation of protein into the hypertrophying skeletal muscle has been the rate-limiting factor in the study at hand.

Image 3: For patients with angina pectoris,
these small sublingual tablets are life-saving,
for the average physical culturist, they
pose a non-negligible health risk.
It is yet still probably not a good, let alone a healthy idea, to get yourself isosorbide dinitrate (IS) from the various online and offline gray-markets, regardless of whether or not you believe your protein synthesis can keep pace... ah, I almost forgot to mention: Those of you who pop some of those little blue pills on a daily basis - you know, those which help you "perform" - probably won't need the IS, anyways. After all, the results of a 2005 study by Hinkle et al. would suggest that Viagra (and similar phosphodiesterase inhibitors) could exert similar effects (Hinkle. 2005) - whether this is a "healthier" alternative is yet still questionable.