Fed-state clamp stimulates cellular mechanisms of muscle protein anabolism and modulates glucose disposal in normal men

Olasunkanmi A.J. Adegoke, Stéphanie Chevalier, José A. Morais, Réjeanne Gougeon, Scot R. Kimball, Leonard S. Jefferson, Simon S. Wing, Errol B. Marliss

Research output: Contribution to journalArticlepeer-review

20 Scopus citations

Abstract

Since maximum anabolism occurs postprandially, we developed a simulated fed state with clamped hyperinsulinemia, physiological hyperglycemia, and hyperaminoaci-demia (Hyper-3) and explored muscle cellular mechanisms. Whole body [1-13C]leucine and [3-3H]glucose kinetics in healthy men were compared between hyperinsulinemic, euglycemic, isoaminoacidemic (Hyper-1, n = 10) and Hyper-3 (n = 9) clamps. In Hyper-3 vs. Hyper-1, nonoxidative leucine Rd [rate of disappearance (synthesis)] was stimulated more (45 ± 4 vs. 24 ± 4 μmol/min, P < 0.01) and endogenous Ra [rate of appearance (breakdown)] was inhibited similarly; hence net balance increased more (86 ± 6 vs. 49 ± 2 μmol/min, P < 0.001). Glucose Rd was similar; thus Hyper-3 metabolic clearance rate (331 ± 23 vs. 557 ± 41 ml/min, P < 0.0005) and Rd/insulin (M, 0.65 ± 0.10 vs. 1.25 ± 0.10 mg· min-1·pmol-1· l, P < 0.001) were less, despite higher insulin (798 ± 74 vs. 450 ± 24 pmol/l, P < 0.005). In vastus lateralis muscle biopsies, phosphorylation of Akt (P = 0.025), mammalian target of rapamycin (mTOR), ribosomal protein S6 kinase (p70S6K1; P = 0.008), S6 (P = 0.049), and 4E-binding protein 1 (4E-BP1; P = 0.001) increased. With decreased eukaryotic initiation factor-4E (eIF4E) ·4E-BP1 complex (P = 0.01), these are consistent with increased mTOR complex 1 (mTORC1) signaling and translation initiation of protein synthesis. Although mRNA expression of ubiquitin, MAFbx 1, and MuRF-1 was unchanged, total ubiquitinated proteins decreased 20% (P < 0.01), consistent with proteolysis suppression. The Hyper-3 clamp increases whole body protein synthesis, net anabolism, and muscle protein translation initiation pathways and decreases protein ubiquitination. The main contribution of hyperaminoacidemia is stimulation of synthesis rather than inhibition of proteolysis, and it attenuates the expected increment of glucose disposal.

Original languageEnglish (US)
Pages (from-to)E105-E113
JournalAmerican Journal of Physiology - Endocrinology and Metabolism
Volume296
Issue number1
DOIs
StatePublished - Jan 2009

All Science Journal Classification (ASJC) codes

  • Endocrinology, Diabetes and Metabolism
  • Physiology
  • Physiology (medical)

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