Combined in vivo and in silico investigation of activation of glycolysis in contracting skeletal muscle

J.P.J. Schmitz, W. Groenendaal, B. Wessels, R.W. Wiseman, P.A.J. Hilbers, K. Nicolay, J.J. Prompers, J.A.L. Jeneson, N.A.W. Riel, van

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Abstract

The hypothesis was tested that the variation of in vivo glycolytic flux with contraction frequency in skeletal muscle can be qualitatively and quantitatively explained by calcium-calmodulin activation of phosphofructokinase (PFK-1). Ischemic rat tibialis anterior muscle was electrically stimulated at frequencies between 0 and 80 Hz to co-vary the ATP turnover rate and calcium concentration in the tissue. Estimates of in vivo glycolytic rates and cellular free energetic states were derived from dynamic changes in intramuscular pH and phosphocreatine content, respectively, determined by phosphorus magnetic resonance spectroscopy (31P MRS). Computational modeling was applied to relate these empirical observations to understanding of the biochemistry of muscle glycolysis. Hereto, the kinetic model of PFK activity in a previously reported mathematical model of the glycolytic pathway (Vinnakota et al., J Physiol 2010) was adapted to contain a calcium-calmodulin binding sensitivity. The two main results were: introduction of regulation of PFK-1 activity by binding of a calcium – calmodulin complex in combination with activation by increased concentrations of AMP and ADP was essential to qualitatively and quantitatively explain the experimental observations. Secondly, the model predicted that shutdown of glycolytic ATP production flux in muscle post-exercise may lag behind deactivation of PFK-1 (timescales: 5-10 s versus 100 – 200 ms, respectively) as a result of accumulation of glycolytic intermediates downstream of PFK during contractions.
Original languageEnglish
Pages (from-to)C180-C193
Number of pages14
JournalAmerican Journal of Physiology : Cell Physiology
Volume304
Issue number2
DOIs
Publication statusPublished - 2013

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