(PO14-39-22) Indicator Amino Acid Oxidation Does Not Require a Lengthy Period of Adaptation When Estimating Amino Acid Requirements in Healthy Young Men

The ePoster content is available to NUTRITION 2022 LIVE ONLINE attendees who are logged in.<br><br>If you are registered, log in and then come back here to use this button.

Presenting Author(s)

SS

Sylwia Szwiega, BASc, MSc(c)
– PhD Candidate , University of Toronto & The Hospital for Sick Children, Markham, Ontario, Canada

Co-Author(s)

RB

Ronald Ball, PhD
– University of Alberta, Edmonton, Alberta, Canada
GC

Glenda Courtney-martin, PhD, RD
– The Hospital for Sick Children Research Institute, Toronto, British Columbia, Canada
Rajavel Elango, PhD
– Associate Professor, School of Population and Public Health, Department of Pediatrics, University of British Columbia, Vancouver, British Columbia, Canada
DK

Dehan Kong
– University of Toronto
PP

Paul Pencharz, PhD
– The Hospital for Sick Children Research Institute, Toronto, Ontario, Canada
CT

Christopher Tomlinson, MB ChB, B.Sc., PhD
– University of Toronto
LX

Libai Xu
– University of Toronto

Disclosure(s):

Sylwia Szwiega, BASc, MSc(c): No relevant financial relationship(s) with ineligible companies to disclose.

Objectives: The objective of the current study was to determine whether 3 or 7 days, compared to 8 hours of adaptation to the test level of threonine intake alters the threonine requirement in healthy young men.

Methods: 11 men (19 – 35 years) were studied at 6 levels of threonine intake (5, 10, 15, 20, 25 and 35 mg.kg^-1.d^-1), in random order. Participants were first habituated to a diet containing intact milk protein (1.0 g.kg^-1.d^-1) and adequate calories for 2 days. Subjects then received an experimental diet containing the test threonine intakes for 7 days, with IAAO studies performed on days 1, 3, and 7. A total of 162 IAAO studies were completed; 54 for each length of adaptation. The rate of release of ¹³CO₂ from the oxidation of L-[1-13C]phenylalanine (F¹³CO₂) was measured. Phenylalanine flux and kinetics were determined from urinary enrichment of L-[1-¹³C]phenylalanine. The threonine requirement was determined by applying mixed effect change-point regression in R to the F¹³CO₂ data. The 95% CI of each breakpoint was calculated using parametric bootstrap and the threonine requirement estimates measured on days 1, 3, and 7 were compared using ANOVA. The effect of threonine intake and days of adaptation on phenylalanine flux and kinetics were assessed using marginal linear mixed models and ANOVA.

Results: The mean threonine requirement (upper, lower 95% CI) for days 1, 3, and 7 was 10.2 (5.4, 15), 10.6 (8, 13.3), and 12.1(9.5, 14.7) mg.kg^-1.d^-1 respectively, and were not statistically different from each other (p = 0.502). Phenylalanine flux was not affect by threonine intake, however flux significantly decreased with increasing length of adaptation (p = 0.000). The interaction between threonine intake and days of adaptation on phenylalanine balance was significant (p = 0.0015); decreased with increasing length of adaptation at intakes below 10 mg.kg^-1.d^-1 threonine, and increased with increasing length of adaptation above 15 mg.kg^-1.d^-1.

Conclusions: We have demonstrated that the short, 8 hour IAAO protocol is valid for the determination of amino acid requirements in humans. This length of adaptation is better positioned to study the amino acid needs of vulnerable populations such as infants, children, and older adults.

Funding Sources: This study was funded by The Canadian Institute of Health Research.