title: Chronic elevated calcium blocks AMPK-induced GLUT-4 expression in skeletal muscle.
abstract: Muscle contraction stimulates glucose transport independent of insulin. Glucose uptake into muscle cells is positively related to skeletal muscle-specific glucose transporter (GLUT-4) expression. Therefore, our objective was to determine the effects of the contraction-mediated signals, calcium and AMP-activated protein kinase (AMPK), on glucose uptake and GLUT-4 expression under acute and chronic conditions. To accomplish this, we used pharmacological agents, cell culture, and pigs possessing genetic mutations for increased cytosolic calcium and constitutively active AMPK. In C2C12 myotubes, caffeine, a sarcoplasmic reticulum calcium-releasing agent, had a biphasic effect on GLUT-4 expression and glucose uptake. Low-concentration (1.25 to 2 mM) or short-term (4 h) caffeine treatment together with the AMPK activator, 5-aminoimidazole-4-carboxamide-1-beta-D-ribonucleoside (AICAR), had an additive effect on GLUT-4 expression. However, high-concentration (2.5 to 5 mM) or long-term (4 to 30 h) caffeine treatment decreased AMPK-induced GLUT-4 expression without affecting cell viability. The negative effect of caffeine on AICAR-induced GLUT-4 expression was reduced by dantrolene, which desensitizes the ryanodine receptor. Consistent with cell culture data, increases in GLUT-4 mRNA and protein expression induced by AMPK were blunted in pigs possessing genetic mutations for both increased cytosolic calcium and constitutively active AMPK. Altogether, these data suggest that chronic exposure to elevated cytosolic calcium concentration blocks AMPK-induced GLUT-4 expression in skeletal muscle.
authors.affiliation: Department of Animal Sciences, Purdue University, West Lafayette, IN 47907, USA.
authors.forename: S
authors.initials: S
authors.lastname: Park
authors.forename: T L
authors.initials: TL
authors.lastname: Scheffler
authors.forename: A M
authors.initials: AM
authors.lastname: Gunawan
authors.forename: H
authors.initials: H
authors.lastname: Shi
authors.forename: C
authors.initials: C
authors.lastname: Zeng
authors.forename: K M
authors.initials: KM
authors.lastname: Hannon
authors.forename: A L
authors.initials: AL
authors.lastname: Grant
authors.forename: D E
authors.initials: DE
authors.lastname: Gerrard
mesh_terms: D009327:4-Chloro-7-nitrobenzofurazan / Q000031:analogs & derivatives / Q000378:metabolism; D055372:AMP-Activated Protein Kinases / Q000235:genetics / Q000378:metabolism*; D000103:Acetyl-CoA Carboxylase / Q000378:metabolism; D000620:Aminoimidazole Carboxamide / Q000031:analogs & derivatives / Q000494:pharmacology; D000818:Animals; D018955:CD36 Antigens / Q000378:metabolism; D002110:Caffeine / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism*; D054732:Calcium-Calmodulin-Dependent Protein Kinase Type 2 / Q000378:metabolism; D002460:Cell Line; D002470:Cell Survival / Q000187:drug effects; D003847:Deoxyglucose / Q000031:analogs & derivatives / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D004789:Enzyme Activation; D020536:Enzyme Activators / Q000494:pharmacology; D005947:Glucose / Q000378:metabolism*; D051275:Glucose Transporter Type 4 / Q000235:genetics / Q000378:metabolism*; D051379:Mice; D009119:Muscle Contraction / Q000187:drug effects; D018482:Muscle, Skeletal / Q000187:drug effects / Q000201:enzymology*; D010766:Phosphorylation; D017354:Point Mutation; D012333:RNA, Messenger / Q000378:metabolism; D012265:Ribonucleotides / Q000494:pharmacology; D013552:Swine; D013997:Time Factors; D015854:Up-Regulation
chemical_list: D018955:CD36 Antigens; D020536:Enzyme Activators; D051275:Glucose Transporter Type 4; D012333:RNA, Messenger; D012265:Ribonucleotides; C495693:Slc2a4 protein, mouse; D000620:Aminoimidazole Carboxamide; D002110:Caffeine; D003847:Deoxyglucose; D054732:Calcium-Calmodulin-Dependent Protein Kinase Type 2; D055372:AMP-Activated Protein Kinases; D000103:Acetyl-CoA Carboxylase; D009327:4-Chloro-7-nitrobenzofurazan; C031143:AICA ribonucleotide; D005947:Glucose; C098340:2-(N-(7-nitrobenz-2-oxa-1,3-diazol-4-yl)amino)-2-deoxyglucose; D002118:Calcium