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Session: Amino Acid and Protein Metabolism (Oral 6)

(OR06-03-24) Compartmental Analysis Estimates Higher Postabsorptive Protein Breakdown in Healthy Individuals, Affecting Its Balance With Dietary Protein Needs

Saturday, June 29, 2024
5:00 PM – 5:12 PM CT
Location:  W183

    Presenting Author(s)

  • Nicolaas Deutz, MD, PhD (he/him/his)

    Director for the Center of Translational Research in Aging and Longevity
    Texas A&M University
    College Station, Texas, United States

    Disclosure(s): Abbott Nutrition: Speaker/Speaker's Bureau (Ongoing)
    Danone/Nutricia: Advisory Committee/Board Member (Ongoing)

    • Co-Author(s)

  • Savanah Knezek, B.S. (she/her/hers)

    PhD Student
    Center for Translational Research in Aging and Longevity, Texas A&M University
    College Station, Texas, United States

  • Raven A. Wierzchowska-McNew, MS

    Graduate Research Assistant
    Texas A&M University
    College Station, Texas, United States

  • Minchae C. Kang, BS

    Graduate Research Assistant
    Center for Translational Research in Aging & Longevity, Department of Health & Kinesiology, Texas A&M University
    College Station, Texas, United States

  • Sofie M. De Wandel, M.S.

    Doctoral Student
    Texas A&M University
    College Station, Texas, United States

  • ME

    Marielle Engelen

    Center for Translational Research in Aging and Longevity, Texas A&M University, United States

Objectives: Whole body amino acid rate of appearance (Ra) in healthy individuals has predominantly been calculated using primed-constant and continuous stable isotope infusion of phenylalanine (PHE) and tyrosine (TYR). We used a new pulse tracer approach to compare the Ra and intracellular production of PHE and TYR to better understand the balance between protein breakdown rate and dietary protein intake.

Methods: (Net) protein breakdown in the postabsorptive condition was measured in 49 healthy individuals (~50y, 22 f) using the pulse tracer approach with L-[ring-13C6]PHE and L-[ring-2H4]TYR stable isotopes. We calculated both the intracellular production of PHE and the Ra. PHE was used to estimate per gram protein breakdown, and PHE to TYR conversion for net protein loss. Lean body mass (LBM) by DEXA. Data are mean [95% CI].

Results: Using Ra, daily protein breakdown was 292 [286, 305] gram protein/individual which is comparable to previously estimated 300 gram protein/individual. However, when calculating intracellular production, daily protein breakdown was 642 [592, 691] gram protein/individual. Daily 75 gram protein intake/represents thus only 12% of intracellular protein breakdown.

Calculating net protein loss was using Ra: 44 [42, 47] and using intracellular production: 87 [82, 92] gram protein/day/individual. Using net intracellular protein loss when no food is provided, daily LBM loss was 577 [544, 611] gram/individual.

Conclusions: We conclude that using the estimation of daily human protein breakdown with the rate of appearance (Ra) as was done in the past is too low. We hypothesize that healthy human protein breakdown is more in the range of 600 gram protein/day.

Funding Sources: ESPEN