Role of glycogen content in insulin resistance in human muscle cells.
We have used primary human muscle cell cultures to investigate the role of glycogen loading in cellular insulin resistance. Insulin pre-treatment for 2 h markedly impaired insulin signaling, as assessed by protein kinase B (PKB) phosphorylation. In contrast, insulin-dependent glycogen synthesis, glycogen synthase (GS) activation, and GS sites 3 de-phosphorylation were impaired only after 5 h of insulin pre-treatment, whereas 2-deoxyglucose transport was only decreased after 18 h pre-treatment. Insulin-resistant glycogen synthesis was associated closely with maximal glycogen loading. Both glucose limitation and 5-aminoimidazole-4-carboxamide 1-beta-D-ribofuranoside (AICAR) treatment during insulin pre-treatment curtailed glycogen accumulation, and concomitantly restored insulin-sensitive glycogen synthesis and GS activation, although GS de-phosphorylation and PKB phosphorylation remained impaired. Conversely, glycogen super-compensation diminished insulin-sensitive glycogen synthesis and GS activity. Insulin acutely promoted GS translocation to particulate subcellular fractions; this was abolished by insulin pre-treatment, as was GS dephosphorylation therein. Limiting glycogen accumulation during insulin pre-treatment re-instated GS dephosphorylation in particulate fractions, whereas glycogen super-compensation prevented insulin-stimulated GS translocation and dephosphorylation. Our data suggest that diminished insulin signaling alone is insufficient to impair glucose disposal, and indicate a role for glycogen accumulation in inducing insulin resistance in human muscle cells.
Litherland
Gary J
GJ
Institute of Cellular Medicine, The Medical School, Framlington Place, Newcastle University, Newcastle upon Tyne, United Kingdom. g.j.litherland@ncl.ac.uk
Morris
Nicholas J
NJ
Walker
Mark
M
Yeaman
Stephen J
SJ
D000091162:AMP-Activated Protein Kinase Kinases; D000620:Aminoimidazole Carboxamide / Q000031:analogs & derivatives / Q000494:pharmacology; D002478:Cells, Cultured; D003847:Deoxyglucose / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D004789:Enzyme Activation; D005947:Glucose / Q000378:metabolism; D006003:Glycogen / Q000096:biosynthesis*; D006006:Glycogen Synthase / Q000378:metabolism; D038362:Glycogen Synthase Kinase 3 / Q000378:metabolism; D006801:Humans; D007328:Insulin / Q000378:metabolism* / Q000494:pharmacology; D007333:Insulin Resistance; D032448:Myoblasts, Skeletal / Q000187:drug effects / Q000378:metabolism*; D010766:Phosphorylation; D011494:Protein Kinases / Q000378:metabolism; D021381:Protein Transport; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism; D012265:Ribonucleotides / Q000494:pharmacology; D015398:Signal Transduction / Q000187:drug effects; D013997:Time Factors
D007328:Insulin; D012265:Ribonucleotides; D000620:Aminoimidazole Carboxamide; D006003:Glycogen; D003847:Deoxyglucose; D006006:Glycogen Synthase; D011494:Protein Kinases; D051057:Proto-Oncogene Proteins c-akt; D038362:Glycogen Synthase Kinase 3; D000091162:AMP-Activated Protein Kinase Kinases; C031143:AICA ribonucleotide; D005947:Glucose