Athletes feature greater rates of muscle glucose transport and glycogen synthesis during lipid infusion

Esther Phielix, Paul Begovatz, Sofiya Gancheva, Alessandra Bierwagen, Esther Kornips, Gert Schaart, Matthijs K. C. Hesselink, Patrick Schrauwen, Michael Roden*

*Corresponding author for this work

Research output: Contribution to journalArticleAcademicpeer-review

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Abstract

BACKGROUND. Insulin resistance results from impaired skeletal muscle glucose transport/phosphorylation, linked to augmented lipid availability. Despite greater intramuscular lipids, athletes are highly insulin sensitive, which could result from higher rates of insulin-stimulated glycogen synthesis or glucose transport/phosphorylation and oxidation. Thus, we examined the time course of muscle glycogen and glucose-6-phosphate concentrations during low and high systemic lipid availability.

METHODS. Eight endurance-trained and 9 sedentary humans (VO2 peak: 56 +/- 2 vs. 33 +/- 2 mL/kg/min, P <0.05) underwent 6-hour hyperinsulinemic-isoglycemic clamp tests with infusions of triglycerides or saline in a randomized crossover design. Glycogen and glucose-6-phosphate concentrations were monitored in vastus lateralis muscles using C-13/P-31 magnetic resonance spectroscopy.

RESULTS. Athletes displayed a 25% greater (P<0.05) insulin-stimulated glucose disposal rate (Rd) than sedentary participants. During Intralipid infusion, insulin sensitivity remained higher in the athletes (Delta Rd: 25 +/- 3 vs.17 +/- 3 mu mol/kg/min, P<0.05), supported by higher glucose transporter type 4 protein expression than in sedentary humans. Compared to saline infusion, AUC of glucose-6-phosphate remained unchanged during Intralipid infusion in athletes (1.6 +/- 0.2 mmol/L vs.1.4 +/- 0.2 [mmol/L] x h, P = n.s.) but tended to decrease by 36% in sedentary humans (1.7 +/- 0.4 vs.1.1 +/- 0.1 [mmol/L] x h, P<0.059). This drop was accompanied by a 72% higher rate of net glycogen synthesis in the athletes upon Intralipid infusion (47 +/- 9 vs.13 +/- 3 mu mol/kg/min, P <0.05).

CONCLUSION. Athletes feature higher skeletal muscle glucose disposal and glycogen synthesis during increased lipid availability, which primarily results from maintained insulin-stimulated glucose transport with increased myocellular glucose-6-phosphate levels for subsequent glycogen synthesis.

Original languageEnglish
Article number127928
Number of pages12
JournalJCI INSIGHT
Volume4
Issue number21
DOIs
Publication statusPublished - 1 Nov 2019

Keywords

  • FREE FATTY-ACIDS
  • INDUCED INSULIN-RESISTANCE
  • HUMAN SKELETAL-MUSCLE
  • PROLONGED SEVERE EXERCISE
  • OXIDATIVE CAPACITY
  • GLUT4 EXPRESSION
  • SENSITIVITY
  • PHOSPHORYLATION
  • METABOLISM
  • DIACYLGLYCEROLS

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