Muscle Protein Synthesis, Part 2�Applying Practice to Theory
Can we enhance protein synthesis? Can we improve amino acid utilization?
By David Sandler, MS, CSCS*D, RSCC*D, HFD, HFI, FNSCA, FISSN
Muscle Protein Synthesis, to an athlete, especially a bodybuilder or someone trying to enhance his or her physique, is about the most important thing the human body can do toward ensuring goals are met and performances are surpassed.
Imagine if you were able to take control of the process and affect the rate and frequency of protein synthesis? Well, guess what? By understanding some of the unique properties of this phenomenon, while I can't guarantee miracles, I will promise you will see results happen faster than ever before. But I do throw some caution in that statement�don't come crying to me when shirts get tight around the chest and arms, and people start staring at you in the gym.
If you perused Part 1 of this two-part series, you should have a layman's understanding of what it takes to get the body to process proteins and use it for repairing damaged muscle and rebuilding new. If you didn't see part 1, no worries, you will still get the gist of this, just without the precursory information�besides, this is the fun stuff anyway. In part 1, we spoke about the process and claimed we still have a lot of investigating to go to truly understand the details. Well, we know that must be the case because if it were that easy to predict when and how protein synthesis truly works, researchers wouldn't continually be going to great lengths to try to find the very best formula to make things work better and faster.
The idea of improving or increasing the ability for muscle to synthesize protein has been part of supplementation research for decades. While only recently have we been able to gain a clearer picture of some of the possibilities, the attempt to create novel products has never had a bigger presence than it does now. Can it be done? We believe so, but honestly, I think we are still going to need a little time to really connect the dots. But we do know a few things that can certainly help. So let's identify some of the key players on the field and their specific roles. Then we will come back to the question of how to make them work together as a team.
The Key Players in Muscle Protein Synthesis
Muscle Protein Synthesis (MPS) is initiated by the demand for rebuilding worn down proteins. While there are several mechanisms that are part of the signaling process, the continual demand for "help" comes from cytokines. These are specific molecules similar to hormones but initiated by a different system, with the intent of repairing or combating issues within a cell that have caused disruption such as the case in muscle damage. Next, pathways such as MTOR and AKT are stimulated to begin the protein synthesis process. MTOR, which is short for the Mammalian Target of Rapamyacin (which still doesn't mean much to me either, so don't worry) is the functioning unit that senses nutrient and oxygen levels in cells but also integrates the effect of growth factors and amino acids. The MTOR pathway has garnered much attention lately as its effect on MPS is critical, but more importantly, it may be controlled to some extent, especially through supplementation.
AKT is named such for a reason that has nothing to do with its name, so we will just look at its function. Really, it's not worth getting into. (No seriously, look it up for yourself, and you will see.) But functionally, it is the main signaling pathway for transcription and cell proliferation, which is the actual protein development, so it is the key factor that induces MPS to increase muscle size and strength. Thus, the AKT pathway has profound effects on adaptations specific to training. The building process begins, and the muscle's overall structure and architecture change in accordance to the demands last placed on it. While this discussion is not about training adaptations, it should be noted, again, that since you control the type of training you perform, you also control the adaptations that your muscles undergo. So if you are looking to increase muscle size, then you need to train accordingly. And if you are looking for speed, power, or even endurance, again, the choice is up to you to provide the stimulus that will make your muscles respond favorably.
Possible Ways to Improve Processes
We've isolated some of the moving parts that are responsible for MPS. It would seem prudent to explore the possibilities of how to get those components to connect, fire, and improve pathway activity. We know there are constituents which can affect the process positively, and that is where this discussion will begin. However, one caveat: the research is still incomplete, so what we say today may change tomorrow.
Of mainstream interest has been the seemingly powerful effects of leucine on MTOR function. It is not fully understood whether leucine has a direct effect (although many people suggest it does) on MTOR or if it is mediated by some other factor first. However, leucine also appears to have a secondary method through a peptide connector called eIF4G which directly affects MPS but not through MTOR. Which then begs the question that if leucine has multiple functions, can other amino acids play a specific role in aiding MPS? My gut instinct says yes, but again, time will tell. For now, supplementing with leucine can't be bad, but how much and what other combinations of aminos might be effective is still a matter of debate.
Of course the MTOR pathway is inside the cell, where amino acids can gather as they can freely pass across the cell membrane to their target. Yet, simply having a high level of amino acids in the cell doesn't mean MPS will be optimal. Furthermore, MTOR is only one of the pathways involved in MPS; there are other ways to excite MPS. Many of the key players in MPS still need to get inside the cell and require passage through the membrane channels. These activators bind with their target receptor RTK (receptor tyrosine kinase) that resides in the cell wall and, when properly connected, open up a pathway that directly affects AKT, MTOR, and other pathways by triggering PI3K (phosphatidylinositol 3-kinase) to do its thing.
PI3K plays a vital role that affects many of the pathways responsible for cell proliferation, growth, and function. PI3K itself is primarily activated by Growth Factors but regulated by signaling mechanisms known as Cytokines and G-Protein Coupled Receptors. In all, there are several different external mechanisms that have to be triggered for optimal MPS to occur.
Are you confused? We all are. This is a complicated process that requires precise sequencing, which itself is a bit of a misnomer since we still are uncertain of all of the sequences that may be involved. MPS is timing specific as well, and thus, having all of the players lined up and ready is still part of the challenge.
But, we also believe there may be ways to enhance these sequences by ingesting bioactive peptides (smaller functional units within protein) such as the growth factors and proline-rich peptides (a type of cytokine) themselves, which can be extracted from the larger proteins by special processing. In fact, processing the finer bioactive peptides is not new as it has been done for decades to build-out infant formulas and immune-function-improving products. It is only now the powerful constituents have been considered for muscle-building and exercise applications.
The good news is: if you consume proteins and/or amino acids and/or bioactive peptides along with solid, consistent exercise, you may positively influence MPS. As science continues to understand the processes and practice continues to show positive results, one can expect an explosion of both products and research relating to bioactive peptides and how one can fine tune MPS.
About the Author
David Sandler, MS, CSCS*D, RSCC*D, HFD, HFI, FNSCA, FISSN, has been a consultant and strength and conditioning coach for the past 25 years and has worked with the nation's top organizations and some of the world's best athletes. He is the Director of Science and Education for iSatori. He is the former Chief Operating Officer of the National Strength and Conditioning Association. Sandler has authored 6 books: Sports Power, Weight Training Fundamentals, The Resistance Band Workout Book, Plyo Power, and Strength Training Everyone, Fundamental Weight Training as well as having developed dozens of exercise videos including three coaching developmental videos. David has published more than 20 scientific articles and abstracts and more than 250 articles in power, strength, and fitness training for various magazines and literature. He is a former powerlifter and three-time US National Bench Press Champion, and his research and passion is with strength and power development.