Essential Amino Acids and Protein Synthesis: Insights into Maximizing the Muscle and Whole-Body Response to Feeding

• Published in: Nutrients Vol. 12; no. 12; p. 3717
• Main Authors: Church, David D, Hirsch, Katie R, Park, Sanghee, Kim, Il-Young, Gwin, Jess A, Pasiakos, Stefan M, Wolfe, Robert R, Ferrando, Arny A
• Format: Journal Article
• Language: English
• Published: Switzerland MDPI 02.12.2020; MDPI AG
• Subjects: Aging - physiology; amino acid kinetics; Amino Acids - metabolism; Amino Acids - pharmacokinetics; Amino Acids, Essential - biosynthesis; Amino Acids, Essential - pharmacology; Dietary Supplements; Eating; essential amino acids; Food; Humans; Kinetics; Male; Metabolism; muscle protein synthesis; Muscle Proteins - biosynthesis; Muscle Proteins - pharmacokinetics; Muscle, Skeletal - metabolism; Phenylalanine; Postprandial Period; protein; Protein Biosynthesis; protein quality; Whey Proteins; whole body protein synthesis; muscle protein synthesis; whole body protein synthesis; nutrition; essential amino acids; amino acid kinetics; protein; aging; protein quality; anabolism
• ISSN: 2072-6643; 2072-6643
• DOI: 10.3390/nu12123717

Ingesting protein-containing supplements and foods provides essential amino acids (EAA) necessary to increase muscle and whole-body protein synthesis (WBPS). Large variations exist in the EAA composition of supplements and foods, ranging from free-form amino acids to whole protein foods. We sought to investigate how changes in peripheral EAA after ingesting various protein and free amino acid formats altered muscle and whole-body protein synthesis. Data were compiled from four previous studies that used primed, constant infusions of L-(ring- H )-phenylalanine and L-(3,3- H )-tyrosine to determine fractional synthetic rate of muscle protein (FSR), WBPS, and circulating EAA concentrations. Stepwise regression indicated that max EAA concentration (EAAC ; R = 0.524, < 0.001), EAAC (R = 0.341, < 0.001), and change in EAA concentration (ΔEAA; R = 0.345, < 0.001) were the strongest predictors for postprandial FSR, Δ (change from post absorptive to postprandial) FSR, and ΔWBPS, respectively. Within our dataset, the stepwise regression equation indicated that a 100% increase in peripheral EAA concentrations increases FSR by ~34%. Further, we observed significant ( < 0.05) positive (R = 0.420-0.724) correlations between the plasma EAA area under the curve above baseline, EAAC , ΔEAA, and rate to EAAC to postprandial FSR, ΔFSR, and ΔWBPS. Taken together our results indicate that across a large variety of EAA/protein-containing formats and food, large increases in peripheral EAA concentrations are required to drive a robust increase in muscle and whole-body protein synthesis.