Improved insulin-stimulated glucose uptake and glycogen synthase activation in rat skeletal muscles after adrenaline infusion: role of glycogen content and PKB phosphorylation.
OBJECTIVE
Effects of in vivo adrenaline infusion on subsequent insulin-stimulated glucose uptake and glycogen synthase activation was investigated in slow-twitch (soleus) and fast-twitch (epitrochlearis) muscles. Furthermore, role of glycogen content and Protein kinase B (PKB) phosphorylation for modulation insulin sensitivity was investigated.


METHODS
Male Wistar rats received adrenaline from osmotic mini pumps ( approximately 150 microg kg(-1) h(-1)) for 1 or 12 days before muscles were removed for in vitro studies.


RESULTS
Glucose uptake at physiological insulin concentration was elevated in both muscles after 1 and 12 days of adrenaline infusion. Insulin-stimulated glycogen synthase activation was also improved in both muscles. This elevated insulin sensitivity occurred despite the muscles were exposed to hyperglycaemia in vivo. After 1 day of adrenaline infusion, glycogen content was reduced in both muscles; insulin-stimulated PKB ser(473) phosphorylation was increased in both muscles only at the highest insulin concentration. After 12 days of adrenaline infusion, glycogen remained low in epitrochlearis, but returned to normal level in soleus; insulin-stimulated PKB phosphorylation was normal in both muscles.


CONCLUSIONS
Insulin-stimulated glucose uptake and glycogen synthase activation were increased after adrenaline infusion. Increased insulin-stimulated glucose uptake and glycogen synthase activation after adrenaline infusion cannot be explained by a reduction in glycogen content or an increase in PKB phosphorylation. The mechanisms for the improved insulin sensitivity after adrenaline treatment deserve particular attention as they occur in conjunction with hyperglycaemia.
Jensen
J
J
Department of Physiology, National Institute of Occupational Health, Oslo, Norway. jorgen.jensen@stami.no
Ruzzin
J
J
Jebens
E
E
Brennesvik
E O
EO
Knardahl
S
S
D000818:Animals; D001786:Blood Glucose / Q000032:analysis; D001835:Body Weight / Q000502:physiology; D004837:Epinephrine / Q000008:administration & dosage* / Q000097:blood; D005947:Glucose / Q000493:pharmacokinetics*; D006003:Glycogen / Q000032:analysis / Q000378:metabolism*; D006006:Glycogen Synthase / Q000378:metabolism*; D007262:Infusions, Intravenous; D007328:Insulin / Q000378:metabolism*; D007773:Lactates / Q000097:blood; D008297:Male; D018482:Muscle, Skeletal / Q000378:metabolism*; D009638:Norepinephrine / Q000097:blood; D010766:Phosphorylation; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism*; D011518:Proto-Oncogene Proteins / Q000378:metabolism*; D051057:Proto-Oncogene Proteins c-akt; D051381:Rats; D017208:Rats, Wistar; D011943:Receptors, Adrenergic, beta / Q000032:analysis
D001786:Blood Glucose; D007328:Insulin; D007773:Lactates; D011518:Proto-Oncogene Proteins; D011943:Receptors, Adrenergic, beta; D006003:Glycogen; D006006:Glycogen Synthase; D017346:Protein Serine-Threonine Kinases; D051057:Proto-Oncogene Proteins c-akt; D005947:Glucose; D009638:Norepinephrine; D004837:Epinephrine