Human muscle fibre type-specific regulation of AMPK and downstream targets by exercise

J Physiol. 2015 Apr 15;593(8):2053-69. doi: 10.1113/jphysiol.2014.283267. Epub 2015 Feb 27.

Abstract

AMP-activated protein kinase (AMPK) is a regulator of energy homeostasis during exercise. Studies suggest muscle fibre type-specific AMPK expression. However, fibre type-specific regulation of AMPK and downstream targets during exercise has not been demonstrated. We hypothesized that AMPK subunits are expressed in a fibre type-dependent manner and that fibre type-specific activation of AMPK and downstream targets is dependent on exercise intensity. Pools of type I and II fibres were prepared from biopsies of vastus lateralis muscle from healthy men before and after two exercise trials: (1) continuous cycling (CON) for 30 min at 69 ± 1% peak rate of O2 consumption (V̇O2 peak ) or (2) interval cycling (INT) for 30 min with 6 × 1.5 min high-intensity bouts peaking at 95 ± 2% V̇O2 peak . In type I vs. II fibres a higher β1 AMPK (+215%) and lower γ3 AMPK expression (-71%) was found. α1 , α2 , β2 and γ1 AMPK expression was similar between fibre types. In type I vs. II fibres phosphoregulation after CON was similar (AMPK(Thr172) , ACC(Ser221) , TBC1D1(Ser231) and GS(2+2a) ) or lower (TBC1D4(Ser704) ). Following INT, phosphoregulation in type I vs. II fibres was lower (AMPK(Thr172) , TBC1D1(Ser231) , TBC1D4(Ser704) and ACC(Ser221) ) or higher (GS(2+2a) ). Exercise-induced glycogen degradation in type I vs. II fibres was similar (CON) or lower (INT). In conclusion, a differentiated response to exercise of metabolic signalling/effector proteins in human type I and II fibres was evident during interval exercise. This could be important for exercise type-specific adaptations, i.e. insulin sensitivity and mitochondrial density, and highlights the potential for new discoveries when investigating fibre type-specific signalling.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • AMP-Activated Protein Kinases / genetics
  • AMP-Activated Protein Kinases / metabolism*
  • Adaptation, Physiological / physiology
  • Adult
  • Exercise / physiology*
  • Gene Expression Regulation
  • Glycogen / metabolism
  • Humans
  • Male
  • Muscle, Skeletal / metabolism*
  • Phosphorylation
  • Protein-Serine-Threonine Kinases / genetics
  • Protein-Serine-Threonine Kinases / metabolism
  • Young Adult

Substances

  • Glycogen
  • STK11 protein, human
  • Protein-Serine-Threonine Kinases
  • AMP-Activated Protein Kinases