Insulin and contraction directly stimulate UCP2 and UCP3 mRNA expression in rat skeletal muscle in vitro.
To study the regulation of the mitochondrial uncoupling protein 2 and 3 (UCP2 and UCP3), we studied the effect of insulin and muscle contraction on UCP mRNA expression in rat skeletal muscle in vitro. Insulin dose-dependently increased skeletal muscle UCP2 and UCP3 mRNA expression in m. extensor digitorum longus (EDL) with maximal stimulation obtained at around 0.6-6 nM. The concentration of insulin giving half-maximal stimulation was 60 pM for the UCP2 and 48 pM for the UCP3 mRNA expression. The effect of insulin was maximal after 2 h and the effect was sustained during the whole study period (6 h). The insulin-induced increase in UCP mRNA was independent of the glucose uptake (as UCP mRNA was stimulated even in incubations without glucose). In addition, electrically induced contractions (in vitro) increased UCP2 and UCP3 mRNA expression 60-120 min after a single bout of contraction (for 10 min). Both the increment of UCP2 and UCP3 mRNA were sustained throughout the study period (4 h) (153 +/- 62 and 216 +/- 71% above basal, P < 0.05 respectively). Finally, 5-aminoimidazole-4-carboxamid-ribosid (AICAR), an activator of the AMP-activated protein kinase (AMPK), that is activated during exercise, was able to mimic the increase in UCP2 and UCP3 mRNA expression. In conclusion, UCP2 and UCP3 mRNA expression in skeletal muscle are stimulated rapidly by insulin and contraction in vitro, thus the stimulation is direct and not caused by changes in other hormones or metabolites. Even a brief bout of contraction induces an increase in UCP2 and UCP3 expression, an effect that could be mimicked by activation of the AMP-activated protein kinase by AICAR.
Pedersen
S B
SB
Department of Endocrinology and Metabolism C, Aarhus Amtssygehus, Aarhus University Hospital, Aarhus C, DK-8000, Denmark. amtssp@aau.dk
Lund
S
S
Buhl
E S
ES
Richelsen
B
B
D055372:AMP-Activated Protein Kinases; D000318:Adrenergic beta-Agonists / Q000494:pharmacology; D000620:Aminoimidazole Carboxamide / Q000031:analogs & derivatives* / Q000494:pharmacology; D000818:Animals; D002352:Carrier Proteins / Q000235:genetics / Q000378:metabolism*; D004305:Dose-Response Relationship, Drug; D004558:Electric Stimulation; D015870:Gene Expression / Q000187:drug effects; D005947:Glucose / Q000378:metabolism / Q000493:pharmacokinetics; D013006:Growth Hormone / Q000494:pharmacology; D007004:Hypoglycemic Agents / Q000494:pharmacology; D066298:In Vitro Techniques; D007328:Insulin / Q000378:metabolism* / Q000494:pharmacology; D007473:Ion Channels; D007545:Isoproterenol / Q000494:pharmacology; D020738:Leptin / Q000494:pharmacology; D008297:Male; D026901:Membrane Transport Proteins; D024101:Mitochondrial Proteins; D009097:Multienzyme Complexes / Q000378:metabolism; D009119:Muscle Contraction / Q000187:drug effects / Q000502:physiology*; D018482:Muscle, Skeletal / Q000187:drug effects / Q000378:metabolism*; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism; D011506:Proteins / Q000235:genetics / Q000378:metabolism*; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar; D012265:Ribonucleotides / Q000494:pharmacology; D014284:Triiodothyronine / Q000494:pharmacology; D000071246:Uncoupling Protein 2; D000071247:Uncoupling Protein 3
D000318:Adrenergic beta-Agonists; D002352:Carrier Proteins; D007004:Hypoglycemic Agents; D007328:Insulin; D007473:Ion Channels; D020738:Leptin; D026901:Membrane Transport Proteins; D024101:Mitochondrial Proteins; D009097:Multienzyme Complexes; D011506:Proteins; D012333:RNA, Messenger; D012265:Ribonucleotides; C000604391:Ucp2 protein, rat; C000604394:Ucp3 protein, rat; D000071246:Uncoupling Protein 2; D000071247:Uncoupling Protein 3; D014284:Triiodothyronine; D000620:Aminoimidazole Carboxamide; D013006:Growth Hormone; D017346:Protein Serine-Threonine Kinases; D055372:AMP-Activated Protein Kinases; C031143:AICA ribonucleotide; D005947:Glucose; D007545:Isoproterenol