Astragalus polysaccharide stimulates glucose uptake in L6 myotubes through AMPK activation and AS160/TBC1D4 phosphorylation

Acta Pharmacol Sin. 2013 Jan;34(1):137-45. doi: 10.1038/aps.2012.133. Epub 2012 Oct 29.


Aim: To establish the mechanism responsible for the stimulation of glucose uptake by Astragalus polysaccharide (APS), extracted from Astragalus membranaceus Bunge, in L6 myotubes in vitro.

Methods: APS-stimulated glucose uptake in L6 myotubes was measured using the 2-deoxy-[(3)H]-D-glucose method. The adenine nucleotide contents in the cells were measured by HPLC. The phosphorylation of AMP-activated protein kinase (AMPK) and Akt substrate of 160 kDa (AS160) was examined using Western blot analysis. The cells transfected with 4P mutant AS160 (AS160-4P) were constructed using gene transfer approach.

Results: Treatment of L6 myotubes with APS (100-1600 μg/mL) significantly increased glucose uptake in time- and concentration-dependent manners. The maximal glucose uptake was reached in the cells treated with APS (400 μg/mL) for 36 h. The APS-stimulated glucose uptake was significantly attenuated by pretreatment with Compound C, a selective AMPK inhibitor or in the cells overexpressing AS160-4P. Treatment of L6 myotubes with APS strongly promoted the activation of AMPK. We further demonstrated that either Ca(2+)/calmodulin-dependent protein kinase kinase β (CaMKKβ) or liver kinase B1 (LKB1) mediated APS-induced activation of AMPK in L6 myotubes, and the increased cellular AMP: ATP ratio was also involved. Treatment of L6 myotubes with APS robustly enhanced the phosphorylation of AS160, which was significantly attenuated by pretreatment with Compound C.

Conclusion: Our results demonstrate that APS stimulates glucose uptake in L6 myotubes through the AMP-AMPK-AS160 pathway, which may contribute to its hypoglycemic effect.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • AMP-Activated Protein Kinases / metabolism*
  • Adenosine Triphosphate / metabolism
  • Animals
  • Astragalus Plant / chemistry*
  • Biological Transport / drug effects
  • Calcium-Calmodulin-Dependent Protein Kinase Kinase / metabolism
  • Cell Line
  • Enzyme Activation / drug effects
  • GTPase-Activating Proteins / genetics
  • GTPase-Activating Proteins / metabolism*
  • Glucose / metabolism*
  • Muscle Fibers, Skeletal / drug effects*
  • Muscle Fibers, Skeletal / metabolism
  • Phosphorylation / drug effects
  • Polysaccharides / isolation & purification
  • Polysaccharides / pharmacology*
  • Rats
  • Up-Regulation


  • GTPase-Activating Proteins
  • Polysaccharides
  • TBC1D4 protein, rat
  • Adenosine Triphosphate
  • Calcium-Calmodulin-Dependent Protein Kinase Kinase
  • AMP-Activated Protein Kinases
  • Glucose