Muscle protein synthesis
Everything you need to know about protein intake and consumption, including a treatment of protein timing and improvements in protein synthesis rates.
What is it? How does it work? Why is it important?
The science of digestion and utilization has always been confusing - not just to the layperson, but to scientists as well. Some things you consume are digested perfectly and immediately and do what you want them to do. Other stuff just stays put, does nothing or - even worse - is converted into fat...or at least it seems to be. What's going on here? Why this unpredictability? And what can we do to at least ensure that the foods and supplements we eat are doing their job?
Taking into account the problems with general food consumption and digestion, it seems even harder to ensure that protein synthesis is taking place. The truth is that there are uncertainties when it comes to the bioavailability of the necessary components, but we are getting better at understanding when and how we can make it happen. To better understand the whole process, we need to go back to the beginning and look at how food gets from your mouth to your muscles.
On your marks, get set, eat!
As I'm writing this article, I'm eating a 350 gram hunk of turkey breast. No, seriously, really. That amount of turkey breast will give me almost 80 grams of protein. And even though turkey is considered one of the higher protein foods (as well as being a low fat source of meat), it only contains about 22% of its weight in protein. This means that 78% of my lunch contains nothing that I really want. Okay, that might be a bit of an exaggeration, but I still need to break all of this down to get my protein. Even though you may be eating for other reasons, I eat this piece of meat to get a big protein boost while filling my belly (especially since it's not nearly as tasty as a family pack of Lays potato chips). If you're wondering where this is going, let me mention that it should become clear soon enough. At least I hope so... The turkey is chewed first and partially digested by enzymes in my mouth. As it makes its way to my stomach, it is further digested by these enzymes and other enzymes are activated on the way to the stomach. When the turkey reaches my stomach, the actual breakdown begins and more powerful digestive juices (acids) rush in to help out. The smaller fragments are continuously separated further as the turkey mash is transported into the digestive tract where it continues to be broken down into tradable pieces. And this is where the fun - or the not so fun part - begins. What happens next is anyone's guess (okay, I'm just kidding). Some of the stuff just stays there and waits until it's needed.
This is one of the great and not-so-great aspects of protein - but more on that a little later. The rest is converted into sugars or fats (or their components). Oh yes, some is actually excreted as waste - but unfortunately this can't potentially prevent you from getting fatter. From here, the now-digested fragments enter the bloodstream as amino acids, sugars and fats. And from here, each molecule's journey either comes to a safe end at a friendly binding site and gets a chance to penetrate the target tissue and do something useful, or it ends up in chaos and gets piled up with all the other molecules that didn't make it. Of course, the latter refers to the hoarding of molecules to make a larger, more complex substance known as either glycogen (if you're lucky) or fat (which is usually the case).
How protein gets to its destination
Let's get back to the topic of protein and try to understand what my paragraph above has to do with protein synthesis. First of all, time was never an issue in the above scenario, but if you look at the process more closely, the hope that needed molecules penetrate the target tissue is both time-dependent and demand-dependent. If these two factors don't match, then the nutrients are back on the white water ride of the bloodstream, but their fate - the unfortunate part - is now much clearer. Fortunately, the fate of protein is slightly different. Protein will remain in the digestive tract longer than most other food components before it is fully digested. This means that it has a better chance of being used. And no, even if it is not used, it will not be converted to fat (at least not without going through several different processes first) as it will eventually be absorbed and used by the body for something else. But this is where the problems of timing and quantity of protein consumption lie.
Based on the above analogies, it should be clear that the purer the form of protein consumed, the less degradation or breakdown is required. Therefore, instead of choking down a boring, dry, stringy hunk of turkey, it might be a better idea to consume some quickly digestible protein. At least if we do this, we can roughly estimate that absorption will take place in 30 to 45 minutes or less and we now have a known time window.
However, it should be noted that the body can only process a maximum of 10 grams of protein per hour. So extra protein could remain in your small intestine for a while if you consume too much of it. This causes two problems. The first is that if protein remains in the digestive tract for too long (several hours), it can lead to unpleasant side effects such as bloating and a bloated feeling. The second problem is that it could be further digested, transported to the liver and turned into glucose, which means that it is no longer available for building muscle tissue.
This means that it's better to eat small amounts of protein (around 30 grams or so) more frequently rather than huge amounts of protein-rich foods during a meal. In addition to this, if you consume fast-digesting protein around the time of increased need (such as your gym workout), you will see better results.
Muscle protein synthesis
All the protein that muscles need is extracted from the digestive tract into the bloodstream in the form of amino acids. These amino acids are either used on their own or combined into some form of peptide chain (several amino acids linked together) that has a specific function.
This is where there can be further problems. The exact peptide combination necessary for protein synthesis to take place means that the individual amino acids must combine and form an active bond with a specific target receptor and only then can the desired function take place. In the case of muscle protein synthesis, the hope is to first generate a need for the process of protein synthesis through an appropriate stimulus (training) and then provide the necessary combination of amino acids for the process of protein synthesis to take place. The process itself is well understood, but what exactly determines whether it can take place or not is still a bit of a mystery. Let's assume that the proteins you need have made it to the target. What if they are not in the right form? What if they are in the wrong combination? In both cases, muscle protein synthesis cannot take place. Again, timing becomes the critical link in the success rate of muscle protein synthesis.
The detailed process of muscle protein synthesis is quite complicated. There are some known issues and we know that if we can increase the activity of the MTORC1 and ATK pathways, we will get better muscle protein synthesis. Don't worry if you don't know what these shortcuts mean or how these pathways work - most people don't - but there is adequate information for those who are really interested. We also know that certain substances can cross the cell membrane, while others need to activate a different peptide to enter the cell. There are several factors that are interdependent, but we are still learning how they interact and differ. Interestingly, if you do a search to learn how muscle protein synthesis occurs at the cellular level, you'll find several different variations, but they all involve the same components.
In other words, we have some unknowns, but all in all, cytokines and growth factors are needed to start the process and bring the necessary substances across the membrane where the appropriate target receptors are ready for them. Once the passage is open, different pathways are activated and cellular reconstruction takes place. In all cases, it is a must that protein, amino acids and the activator components are available. And last but not least, supplement science will continue to try to determine what is the best combination to effectively increase muscle protein synthesis.
The importance of timing
I have mentioned timing several times throughout this paper. It is an essential component of muscle development, training, healthy eating and a number of other processes. In the case of muscle building, wouldn't it be nice to know what the best timing is for muscle protein synthesis to occur? Well, of the few things we know, this is one of them.
First of all, muscle protein synthesis takes place as a result of muscle tissue destruction, breakdown or stress. Any form of above-normal muscle contraction causes stress (by the way, so do normal muscle contractions, but to a much lesser extent). By "beyond normal" I mean training with weights vs. the activities of daily life. Secondly, training causes the muscle tissue to contract at a higher, stronger and faster rate than normal, resulting in damage to protein structures within the muscle. So now we know when muscle protein synthesis might take place. And that if we have some protein available in the muscle, it is likely to be used as part of muscle protein synthesis to repair the damaged muscle tissue. So the time around exercise - either before, during or immediately after exercise, or all three times - is a good time to make sure you have enough protein (and amino acids) in your blood.
We also know that having extra protein in your blood during the 24 hours after exercise is also beneficial, as muscle protein synthesis continues until the process is complete. And what does this mean for those who train daily? Well, you must always consume protein, be it in the form of whole foods or in the form of supplements. Don't miss the anabolic window of opportunity because you're not prepared. With so many unknowns when it comes to training, you should utilize everything you know with certainty.
Summary of Part 1
While this look at protein synthesis is neither complete nor scientifically detailed, it gives a solid overview of the process and should get you thinking about ways to improve your ability to synthesize protein and use it to increase your athletic performance and the size of your muscles. In the next section, we'll talk about some methods for increasing muscle protein synthesis and training strategies to ensure you maximize your results while minimizing all that complicated processing of food.
Muscle protein synthesis - applying theory to practice
Can we increase protein synthesis? Can we improve the use of amino acids? Muscle protein synthesis is pretty much the most important thing the human body can do for an athlete - especially a bodybuilder - or anyone who wants to improve their body development, to ensure that goals are achieved and previous best performances are surpassed. Imagine if we were able to control this process and influence the rate and frequency of muscle protein synthesis. Now, while I can't promise miracles, I can promise that if you understand some of the unique properties of this phenomenon, you will see faster results than ever before. But I want to warn you in advance - don't come crying to me complaining when your shirts get too tight around the chest and arms and people at the gym start staring at you.
If you've read the first part of this article, then you should have a layman's understanding of what it takes to get the body to process protein and use it to repair damaged muscle and build new muscle tissue. If you haven't read Part 1, then you'll still understand the second part - apart from that, this is the more fun part anyway. In Part 1, we talked about the process and claimed that there was still a lot of research needed to really understand the details. Well, we know this must be the case, because if it was easy to predict when and how protein synthesis really happens, scientists wouldn't continue to go to great lengths to try and find the best formula to make things work better and faster.
The theory
The idea of improving or enhancing the ability of muscles to synthesize protein has been an integral part of supplement research for decades. While it's only in recent years that we've been able to get a clearer picture of some of the possibilities, attempts to develop novel products have never been as extensive as they are today. Is it possible to do this? I think so, but if I'm honest, I think we'll need some time to connect all the dots. However, we already 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'll 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 is initiated by the need to rebuild damaged proteins. Although there are several mechanisms that are part of the signaling process, the most consistent call for "help" comes from cytokines. These are specific molecules that resemble hormones but initiate a different system with the intention of repairing or combating problems within a cell that have caused damage, as is the case with muscle damage.
Next, pathways such as mTOR and AKT are stimulated to start the process of protein synthesis. mTOR - which stands for Mammalian Target of Rapamyacin (which doesn't mean much to me either, so don't worry) - is the functional unit that senses nutrient and oxygen levels in cells, but also integrates the action of growth factors and amino acids. The mTOR pathway has attracted quite a bit of attention recently because its effects on muscle protein synthesis are crucial. More importantly, it can be controlled to a certain extent - especially through supplements. ATK bears its name for a reason that has nothing to do with its function, which is why we're just going to look at its function. Really, it's nothing worth going into more detail about. (No, seriously, look it up yourself and you'll see). Functionally, however, ATK is the primary signaling pathway for transcription and cell proliferation, which is protein development itself. Thus, AKT is the key factor that induces muscle protein synthesis for an increase in muscle mass and strength.
The AKT pathway thus has profound effects on training-specific adaptations. The building process begins and the overall structure and architecture of the muscle changes based on the demands placed on it. Although this is not about training adaptations, it should be noted that since you control the type of training you perform, you can also control the adaptations a muscle undergoes. So if you want to increase your muscle mass, then you need to train accordingly. And if you want to improve speed, speed-strength or even endurance, then it's up to you to choose the stimulus that makes your muscles respond the way you want them to.
Possible ways to improve processes
We have isolated some parts that are responsible for muscle protein synthesis. It would seem wise to explore ways to connect these components and increase pathway activity. We know that there are building blocks that can positively influence the process and that is where the discussion begins. However, there is a caveat: the scientific research is still incomplete in this area, so what we say today may change tomorrow. Of mainstream interest are the seemingly powerful effects of leucine on mTOR function. As yet, it is not known for certain whether leucine has a direct effect on mTOR (although many people think it does) or whether there are other factors involved. Leucine also appears to have a secondary effect via a peptide linker called elF4G, which influences muscle protein synthesis directly and not via mTOR. The fact that leucine has multiple functions begs the question of whether other amino acids also play a specific role in supporting muscle protein synthesis. My first instinct says yes, but time will answer that question. For now, supplementing with leucine can't hurt, but how much is optimal and what other combinations of amino acids might be effective is still hotly debated.
The mTOR pathway naturally occurs within the cell, where amino acids can accumulate as they can pass unhindered through the cell membrane to their target. Nevertheless, high levels of amino acids in the cell do not automatically mean that muscle protein synthesis will be optimal. Furthermore, mTOR is only one of the pathways involved in muscle protein synthesis - there are other ways to stimulate muscle protein synthesis. Many of the key players involved in muscle protein synthesis still need to enter the cell and require passage through the membrane channels. These activators bind to their target receptor RTK (Receptor Tyrosine Konase), which is located in the cell wall and opens a pathway that directly affects AKT, mTOR and other pathways by triggering PI3K (Phosphatidylinositol 3-kinase) to do its job.
PI3K plays a critical role that influences many of the pathways responsible for cell proliferation, growth and function. PI3K is primarily activated by growth factors, but is controlled by signaling mechanisms known as cytokines and G-protein coupled receptors. In addition, insulin and in particular the influence of IGF-1 (Insulin-Like Growth Factor-1) also play a role in receptor activation. All in all, there are several different external factors that need to be activated for optimal muscle protein synthesis.
Are you confused? We all are. This is a complicated process that requires precise sequencing, and we don't yet know exactly which sequences might be involved. Muscle protein synthesis is also dependent on the right timing, so part of the challenge is to have all the players in place and ready to go. However, we also believe that there may be ways to enhance these sequences by consuming bioactive peptides (smaller functional units within proteins) such as growth factors and proline-rich peptides (a type of cytokine), which can be extracted from larger proteins through specialized processing. The production of the finer bioactive peptides is nothing new and has been used for decades in the production of infant formulas and products to improve immune function. But only now have these powerful ingredients begun to be considered for muscle building and sports applications.
The good news is that if you consume proteins and/or amino acids and/or bioactive peptides in combination with solid, consistent training, you could positively impact muscle protein synthesis. As science continues to study and better understand the processes and practice continues to show positive results, we can expect an explosion of both new products and research on bioactive peptides and optimizing muscle protein synthesis.
Source: https://www.muscleandstrength.com/articles/muscle-protein-synthesis-timing-enhancement