“We are what we eat” has been common for hundreds of years and the relationship between body composition and food consumption has been studied for a long time. The synthesis and decomposition of human proteins (systemic protein dynamics) in response to dietary consumption has been studied for nearly a century. Nevertheless, controversy over the best way to determine systemic protein dynamics remains.
Here, the University of Arkansas scientists: Professor Robert Wolf, Professor Alney Ferlando, Dr. David Ferlando, Dr. David Church, and Professor Il Yoo King, from Gacheng University A critical review of the most extensive use of methods for determining systemic protein dynamics response to dietary protein consumption, presented by Professor Sanger Parker and Massey University in New Zealand, published in the Journal Clinical Nutrition Open Science 36 (2021): 78-90.
According to a review by Wolfe and colleagues, the general principles of the systemic protein model focus on the overall process of protein synthesis and decomposition rather than components and various pools. Basically, labeled molecules are used as tracers, and the appearance rate of endogenous traces can be quantified by somatic protein decomposition and trace uptake rates during protein synthesis. Tracers are usually intravenous, but in some cases oral. Estimation of net protein balance throughout the body (i.e., an anabolic reaction) is equal to protein synthesis minus decomposition. Lead author Professor Wolf said: “Quantitizing the anabolic response to dietary protein intake is an important application. There are different models that can achieve this, each with advantages and limitations.”
Nitrogen (N)-Fluorescence has the excellent advantage of requiring only oral tracer, so the method is noninvasive. Furthermore, the model can calculate all aspects of systemic protein dynamics with minimal hypothesized. However, it is difficult to quantify changes in a single meal in this way. Professor Wolf emphasized that despite the advantages of this approach using this approach over a long period of time, “rapid changes in protein dynamics, such as after a single diet protein, cannot be reliably determined by the N-frequency treatment method. ”
Initiator infusion of essential amino acid tracers can be used to quantify rapid changes in basal state in systemic protein kinetics that occur after intake of a single meal containing diet protein. Professor Wolfe mentioned that science shows that the response to representing data as a basis state has a clear advantage, that is, taking into account differences in the basic dynamics of protein dynamics among individual subjects. A fast time frame that can be used based on models of intravenous injection of essential amino acid tracers is also an important advantage. The main challenge of model based on essential amino acid tracers after meals is to distinguish unlabeled traces in the blood from protein decomposition in the body rather than absorption of digested dietary proteins. The consumption of essentially labeled proteins helps distinguish whether the traces observed in the blood come from ingested proteins or the breakdown of the body proteins. However, the lack of the availability of essentially labeled proteins is a limitation of this approach. Fundamentally, the dilution of essentially labeled proteins may lead to a significant underestimation of dietary protein absorption due to the overestimation of the rate of protein decomposition in humans.
Another method of using essentially labeled proteins is called the “bioavailability” method, which calculates the absorption of essential amino acids of Tracee based on the proteins intake known to be consumed, the amount of trace amino acids contained in the diet protein and The true digestibility of protein. “One of the advantages of bioavailability approaches is that the responses of a combination of multiple proteins that may be included in a normal meal can be quantified. In addition, no physiological homeostasis is required, which means that the approach is ideal for quantifying responses to meals.” Professor Wolf said. He added: “On the other hand, the total anabolic response can only be determined, as the total contribution of exogenous phenylalanine to the peripheral cycle can only be estimated, not the rate at which it absorbs. Again, the method usually has to rely on literature value. To achieve true ileal digestibility, in some cases, may be inaccurate. “On the other hand, the above figure shows that using the upper or lower limit of the possible true digestibility does not usually significantly affect the conclusion.
In summary, the most appropriate method for quantifying systemic protein dynamics depends on the degree of uncertainty in the required assumptions in a given situation. In this review, it has been shown that all methods of obtaining overall protein have certain limitations. Professor Wolfe and colleagues recommend using the realistic maximum and minimum values of assumed parameters to calculate all upper and lower limits of systemic protein dynamics. Using two models that require different assumptions simultaneously can also help verify the results of the calculation.
Journal Reference and Image Credit:
Wolfe, Robert R. “System-body protein dynamics model quantifies the anabolic response to dietary protein consumption.” Clinical Nutrition Open Science 36 (2021): 78-90.
About the Author
Dr. Robert R. Wolfe, Professor
Dr. Wolfe is the chairman of Jane and Edward Warmack’s nutritional longevity, University of Arkansas Medical Sciences, Little Rock. Dr. Wolf previously served as John Cially Distinguished Clinical Research Chair at the University of Texas Medical Branch in Galveston, Texas. Dr. Wolfe is a world leader in human metabolism and stable isotope tracing methods, with over 600 publications, five books and nine patents. According to Google Scholar, his paper has been cited over 77,000 times (H Factor = 137). NIH has funded him over his 40-year career. He has served as a member of several government and industry committees responsible for determining dietary protein needs and has received numerous honors and awards for his work. Disclosure: Dr. Wolfe is Essential Blends, LLC and Amino Company, Inc. Dr. Wolfe, shareholder, has received a Research grant and remuneration from the National Cattleman’s Beef Association. No other disclosures.
