title: Caffeine-induced Ca(2+) release increases AMPK-dependent glucose uptake in rodent soleus muscle.
abstract: Previous studies have proposed that caffeine-induced activation of glucose transport in skeletal muscle is independent of AMP-activated protein kinase (AMPK) because alpha-AMPK Thr172 phosphorylation was not increased by caffeine. However, our previous studies, as well as the present, show that AMPK phosphorylation measured in whole muscle lysate is not a good indicator of AMPK activation in rodent skeletal muscle. In lysates from incubated rat soleus muscle, a predominant model in previous caffeine-studies, both acetyl-CoA carboxylase-beta (ACCbeta) Ser221 and immunoprecipitated alpha(1)-AMPK activity increased with caffeine incubation, without changes in AMPK phosphorylation or immunoprecipitated alpha(2)-AMPK activity. This pattern was also observed in mouse soleus muscle, where only ACCbeta and alpha(1)-AMPK phosphorylation were increased following caffeine treatment. Preincubation with the selective CaMKK inhibitor STO-609 (5 microM), the CaM-competitive inhibitor KN-93 (10 microM), or the SR Ca(2+) release blocking agent dantrolene (10 microM) all inhibited ACCbeta phosphorylation and alpha(1)-AMPK phosphorylation, suggesting that SR Ca(2+) release may work through a CaMKK-AMPK pathway. Caffeine-stimulated 2-deoxyglucose (2DG) uptake reflected the AMPK activation pattern, being increased with caffeine and inhibited by STO-609, KN-93, or dantrolene. The inhibition of 2DG uptake is likely causally linked to AMPK activation, since muscle-specific expression of a kinase-dead AMPK construct greatly reduced caffeine-stimulated 2DG uptake in mouse soleus. We conclude that a SR Ca(2+)-activated CaMKK may control alpha(1)-AMPK activation and be necessary for caffeine-stimulated glucose uptake in mouse soleus muscle.
authors.affiliation: Department of Exercise and Sport Sciences, Copenhagen Muscle Research Center, University of Copenhagen, Universitetsparken 13, 2100 Copenhagen, Denmark.
authors.forename: Thomas E
authors.initials: TE
authors.lastname: Jensen
authors.forename: Adam J
authors.initials: AJ
authors.lastname: Rose
authors.forename: Ylva
authors.initials: Y
authors.lastname: Hellsten
authors.forename: Jørgen F P
authors.initials: JF
authors.lastname: Wojtaszewski
authors.forename: Erik A
authors.initials: EA
authors.lastname: Richter
mesh_terms: D055372:AMP-Activated Protein Kinases; D000818:Animals; D002110:Caffeine / Q000494:pharmacology*; D002118:Calcium / Q000378:metabolism; D020013:Calcium Signaling / Q000187:drug effects / Q000502:physiology*; D054737:Calcium-Calmodulin-Dependent Protein Kinase Kinase; D005260:Female; D005947:Glucose / Q000378:metabolism*; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D008822:Mice, Transgenic; D009097:Multienzyme Complexes / Q000378:metabolism*; D018482:Muscle, Skeletal / Q000187:drug effects* / Q000378:metabolism; D010766:Phosphorylation; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism*; D051381:Rats; D017207:Rats, Sprague-Dawley
chemical_list: D009097:Multienzyme Complexes; D002110:Caffeine; D017346:Protein Serine-Threonine Kinases; D054737:Calcium-Calmodulin-Dependent Protein Kinase Kinase; D055372:AMP-Activated Protein Kinases; D005947:Glucose; D002118:Calcium