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Amino acid metabolism and protein turnover in lean and obese humans during exercise ─ effect of IL-6 receptor blockade

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  • Beckey Trinh
  • Merel Peletier
  • Casper Simonsen
  • Peter Plomgaard
  • Kristian Karstoft
  • Bente Klarlund Pedersen
  • Gerrit van Hall
  • Helga Ellingsgaard
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CONTEXT: Interleukin-6 (IL-6) is implicated in skeletal muscle wasting and in regulating skeletal muscle hypertrophy in the healthy state.

OBJECTIVE: This work aimed to determine the role of IL-6 in regulating systemic protein and amino acid metabolism during rest, exercise, and recovery in lean and obese humans.

METHODS: In a nonrandomized, single-blind design, 12 lean and 9 obese individuals were infused first with 0.9% saline (Saline), secondly with the IL-6 receptor antibody tocilizumab (Acute IL-6R ab), and 21 days later with saline while still under tocilizumab influence (Chronic IL-6R ab). Outcome measures were determined before, during, and after 90 minutes of exercise at 40% Wattmax by isotope dilution technique, using primed continuous infusion of L-[ring-D5]phenylalanine and L-[D2]tyrosine. Main outcomes measures included systemic protein turnover and plasma amino acid concentrations.

RESULTS: We saw no effect of acute or chronic IL-6 receptor blockade on protein turnover. In lean individuals, chronic IL-6 receptor blockade increased plasma concentrations of total amino acids (rest Δ + 186 μmol/L; 95% CI, 40-332; recovery Δ + 201 μmol/L; 95% CI, 55-347) and essential amino acids (rest Δ + 43 μmol/L; 95% CI, 12-76; recovery Δ + 45 μmol/L; 95% CI, 13-77) independently of exercise but had no such effect in obese individuals (total amino acids rest Δ + 63 μmol/L; 95% CI, -170 to 295, recovery Δ - 23 μmol/L, 95% CI, -256 to 210; essential amino acids rest Δ + 26 μmol/L; 95% CI, -21 to 73, recovery Δ + 11 μmol/L; 95% CI, -36 to 58).

CONCLUSION: IL-6 receptor blockade has no effect on protein turnover in fasting lean and obese humans during rest, exercise, and recovery. Chronic IL-6 receptor blockade increases total and essential amino acid concentrations only in lean individuals.

Original languageEnglish
JournalThe Journal of clinical endocrinology and metabolism
Issue number7
Pages (from-to)1854-1864
Number of pages11
Publication statusPublished - 1 Jul 2022

Bibliographical note

© The Author(s) 2022. Published by Oxford University Press on behalf of the Endocrine Society. All rights reserved. For permissions, please e-mail:

    Research areas

  • Amino Acids/metabolism, Humans, Interleukin-6/metabolism, Muscle, Skeletal/metabolism, Obesity/metabolism, Phenylalanine, Receptors, Interleukin-6/metabolism, Single-Blind Method, rest, exercise, recovery, IL-6, obese, protein turnover, tocilizumab

ID: 78362543