Comprehensive assessment of post-prandial protein handling by the application of intrinsically labelled protein in vivo in human subjects

Abstract

All human tissues are in a constant state of remodelling, regulated by the balance between tissue protein synthesis and breakdown rates. It has been well-established that protein ingestion stimulates skeletal muscle and whole-body protein synthesis. Stable isotope-labelled amino acid methodologies are commonly applied to assess the various aspects of protein metabolism in vivo in human subjects. However, to achieve a more comprehensive assessment of post-prandial protein handling in vivo in human subjects, intravenous stable isotope-labelled amino acid infusions can be combined with the ingestion of intrinsically labelled protein and the collection of blood and muscle tissue samples. The combined application of ingesting intrinsically labelled protein with continuous intravenous stable isotope-labelled amino acid infusion allows the simultaneous assessment of protein digestion and amino acid absorption kinetics (e.g. release of dietary protein-derived amino acids into the circulation), whole-body protein metabolism (whole-body protein synthesis, breakdown and oxidation rates and net protein balance) and skeletal muscle metabolism (muscle protein fractional synthesis rates and dietary protein-derived amino acid incorporation into muscle protein). The purpose of this review is to provide an overview of the various aspects of post-prandial protein handling and metabolism with a focus on insights obtained from studies that have applied intrinsically labelled protein under a variety of conditions in different populations.

Potato Protein Ingestion Increases Muscle Protein Synthesis Rates at Rest and during Recovery from Exercise in Humans

“…4), we attribute this to a more delayed protein digestion and AA absorption, an increased AA retention in splanchnic tissues, and/or a less efficient digestion of potato compared with milk protein. As the intrinsically labeled protein approach (42) simply cannot be applied in the case of plant-derived proteins, it is impossible to directly quantify the exact amount of potato protein-derived AA that were released in the circulation, as we have done previously for milk- (2) and mealworm-derived protein (43).…”

The impact of collagen protein ingestion on musculoskeletal connective tissue remodeling: a narrative review

“…The ingestion of specifically produced highly l -[1- 13 C]-phenylalanine–enriched (> 35 mole percent excess) casein protein combined with tissue sampling allows for the assessment of the metabolic fate of dietary protein–derived amino acids into newly synthesized proteins, termed de novo protein synthesis. 87 , 88 Using this approach, Trommelen et al 14 demonstrated for the first time that dietary protein–derived amino acids are, indeed, incorporated into de novo intramuscular connective tissue protein. Follow-up work demonstrated that the utilization of the ingested protein-derived amino acids for de novo intramuscular connective tissue protein synthesis is further enhanced during recovery from resistance exercise.…”

The Anabolic Response to Plant-Based Protein Ingestion

“…Insects have a high protein content and their protein has an amino acid composition that closely resembles conventional high-quality animal-derived proteins [ 107 ]. Recently, we produced intrinsically labelled lesser mealworms by feeding these larvae with stable isotope labelled amino acids [ 25 ], allowing us to directly quantitate protein digestion and amino acid absorption kinetics and the subsequent muscle protein synthetic response at rest and during recovery from exercise following ingestion of a single bolus of mealworms. The mealworm-derived protein was rapidly digested and absorbed and strongly increased post-prandial muscle protein synthesis rates.…”

“…The differential muscle protein synthetic response to feeding is largely dependent on the post-prandial rise in plasma essential amino acid concentrations [5], with plasma leucine concentrations being of particular importance [18][19][20][21][22][23][24]. The post-prandial rise in circulating amino acids and the subsequent increase in muscle protein synthesis rate are regulated on various levels, ranging from dietary protein digestion, amino acid absorption, splanchnic amino acid sequestration, post-prandial tissue perfusion, uptake of amino acids by the muscle, and the activation of the muscle protein synthetic machinery [4,25]. To date, most studies have focused on assessing the post-prandial muscle protein synthetic response to dairy protein [15,17,21,[26][27][28][29][30][31] and meat [10,[32][33][34] ingestion.…”