Application of the Indicator Amino Acid Oxidation Technique for the Determination of Metabolic Availability of Sulfur Amino Acids from Casein versus Soy Protein Isolate in Adult Men ,

Abstract

Our objective was to determine the metabolic availability (MA) of sulfur amino acids in dietary proteins using the indicator amino acid oxidation (IAAO) technique. Five to seven men received graded levels (20, 40, 60, and 70%) of the mean total sulfur amino acid (TSAA) requirement of 13 mg x kg(-1) x d(-1) as a crystalline AA mixture, casein, and soy protein isolate (SPI) (40, 50, 60, and 70%), respectively. Five of these subjects received 40% of TSAA requirement from SPI supplemented with methionine to the level of 40% of requirement. These 5 subjects also repeated the level of 60% TSAA requirements from both casein and SPI to assess repeatability. The mean MA of TSAA from SPI (71.8 +/- 3.6%) was lower than from casein (87.4 +/- 3.8%, P < 0.05). Supplementation of SPI with methionine decreased the IAAO (11.5 +/- 0.3% administered dose) compared with unsupplemented SPI (12.8 +/- 0.5% administered dose, P < 0.05). IAAO was similar for repeated measurements of casein and SPI, respectively, at the 60% TSAA intake level (10.8 +/- 1.0 vs. 10.7 +/- 1.2% for casein; 12.7 +/- 1.3 vs. 12.9 +/- 2.6% for SPI). In conclusion, the IAAO technique can be used to determine the MA of AA for protein synthesis in test proteins for humans.

Bioavailability of threonine and tryptophan in peanut meal for starter pigs using slope-ratio assay

“…Changes in the oxidation of indicator amino acid following the intake of test and reference proteins will reflect the whole-body metabolic availability of the limiting amino acid at the site of protein synthesis and, thus, account for all losses of dietary amino acids during digestion, absorption and metabolism of the test amino acid. Using this method, Moehn et al (2005) determined that the metabolic availability of lysine in peas for pigs is 88% and Humayun et al (2007) reported that the metabolic availabilities of the sulphuramino acids in casein and soy protein isolate for pigs are 87% and 72%, respectively.…”

Protein Supplementation of a High-Carbohydrate Diet during Resistance Training Enhances Muscle Mass and Function by Increasing Essential Amino Acids

“…With increases in carbohydrate and protein intake, a progressively greater anabolic response with inconstant increases in the insulin response and suppression of protein breakdown occurs [61]. However, most studies indicated that the net protein synthesis is related to the availability of amino acids [51,62,63].…”

The challenge of diabetes in Asia

“…The most recent protein requirement report (WHO, 2007) noted the potential promise of using 24-hour IAAO balance instead of or in addition to 24-hour nitrogen balance for the determination of amino acid requirements of humans. A method, based upon the IAAO technique, was developed to measure the metabolic availability of the limiting amino acid in the diet of pigs (Levesque et al, 2010;Moehn et al, 2005Moehn et al, , 2007 and subsequently adapted to humans (Humayun et al, 2007, Prolla et al, 2013. In the pig, the values obtained by IAAO are not different from those obtained by 'true' ileal digestibility.…”

“…Phenylalanine, in the presence of excess tyrosine, fi ts all four criteria. L-1-13 C-Phenylalanine has been successfully used to measure metabolic availability in pigs (Levesque et al, 2011;Moehn et al, 2005Moehn et al, , 2007 and humans (Humayun et al, 2007;Prolla et al, 2013). It is possible that other amino acids, such as leucine, are usable as tracers; however, to date phenylalanine has been used in these protocols to determine dietary bioavailability of amino acids.…”