AMPK alpha1 activation is required for stimulation of glucose uptake by twitch contraction, but not by H2O2, in mouse skeletal muscle.
BACKGROUND
AMPK is a promising pharmacological target in relation to metabolic disorders partly due to its non-insulin dependent glucose uptake promoting role in skeletal muscle. Of the 2 catalytic alpha-AMPK isoforms, alpha(2) AMPK is clearly required for stimulation of glucose transport into muscle by certain stimuli. In contrast, no clear function has yet been determined for alpha(1) AMPK in skeletal muscle, possibly due to alpha-AMPK isoform signaling redundancy. By applying low-intensity twitch-contraction and H(2)O(2) stimulation to activate alpha(1) AMPK, but not alpha(2) AMPK, in wildtype and alpha-AMPK transgenic mouse muscles, this study aimed to define conditions where alpha(1) AMPK is required to increase muscle glucose uptake.


RESULTS
Following stimulation with H(2)O(2) (3 mM, 20 min) or twitch-contraction (0.1 ms pulse, 2 Hz, 2 min), signaling and 2-deoxyglucose uptake were measured in incubated soleus muscles from wildtype and muscle-specific kinase-dead AMPK (KD), alpha(1) AMPK knockout or alpha(2) AMPK knockout mice. H(2)O(2) increased the activity of both alpha(1) and alpha(2) AMPK in addition to Akt phosphorylation, and H(2)O(2)-stimulated glucose uptake was not reduced in any of the AMPK transgenic mouse models compared with wild type. In contrast, twitch-contraction increased the activity of alpha(1) AMPK, but not alpha(2) AMPK activity nor Akt or AS160 phosphorylation. Glucose uptake was markedly lower in alpha(1) AMPK knockout and KD AMPK muscles, but not in alpha(2) AMPK knockout muscles, following twitch stimulation.


CONCLUSIONS
These results provide strong genetic evidence that alpha(1) AMPK, but not alpha(2) AMPK, Akt or AS160, is necessary for regulation of twitch-contraction stimulated glucose uptake. To our knowledge, this is the first report to show a major and essential role of alpha(1) AMPK in regulating a physiological endpoint in skeletal muscle. In contrast, AMPK is not essential for H(2)O(2)-stimulated muscle glucose uptake, as proposed by recent studies.
Jensen
Thomas E
TE
Molecular Physiology Group, Copenhagen Muscle Research Centre, Department of Exercise and Sport Sciences, Section of Human Physiology, University of Copenhagen, Copenhagen, Denmark.
Schjerling
Peter
P
Viollet
Benoit
B
Wojtaszewski
Jørgen F P
JF
Richter
Erik A
EA
D055372:AMP-Activated Protein Kinases; D000818:Animals; D003847:Deoxyglucose / Q000378:metabolism; D004789:Enzyme Activation; D005947:Glucose / Q000378:metabolism*; D006861:Hydrogen Peroxide / Q000494:pharmacology*; D007527:Isoenzymes / Q000378:metabolism; D051379:Mice; D018345:Mice, Knockout; D008822:Mice, Transgenic; D009097:Multienzyme Complexes / Q000172:deficiency / Q000235:genetics / Q000378:metabolism*; D009119:Muscle Contraction / Q000187:drug effects / Q000502:physiology*; D018482:Muscle, Skeletal / Q000201:enzymology*; D017346:Protein Serine-Threonine Kinases / Q000172:deficiency / Q000235:genetics / Q000378:metabolism*; D015398:Signal Transduction
D007527:Isoenzymes; D009097:Multienzyme Complexes; D003847:Deoxyglucose; D006861:Hydrogen Peroxide; D017346:Protein Serine-Threonine Kinases; D055372:AMP-Activated Protein Kinases; D005947:Glucose