title: Possible involvement of AMPK in acute exercise-induced expression of monocarboxylate transporters MCT1 and MCT4 mRNA in fast-twitch skeletal muscle.
abstract: OBJECTIVE
  The regulatory mechanisms responsible for acute exercise-induced expression of monocarboxylate transporters MCT1 and MCT4 mRNA in skeletal muscle remain unclear. 5'-adenosine-activated protein kinase (AMPK) is a key signaling molecule that regulates gene expression at the mRNA level. We examined whether AMPK activation is involved in acute exercise-induced expression of MCT1 and MCT4 mRNA in fast-twitch muscle.
  
  
  METHODS
  Male Sprague-Dawley rats were subjected to an acute bout of either 5min high-intensity intermittent swimming (HIS) or 6-h low-intensity prolonged swimming (LIS). The effects of acute exercise on the phosphorylation of AMPK (p-AMPK), calcium/calmodulin pendent kinase II (p-CaMKII), p38 mitogen-activated protein kinase (p-p38MAPK), and MCTs mRNA were analyzed in vivo. To observe the direct effects of AMPK activation on MCTs mRNA, the effects of 5-aminoimidazole-4-carboxamide-1-beta-D-ribofuranoside (AICAR), caffeine, and dantrolene were analyzed in vitro using an isolated muscle incubation model.
  
  
  RESULTS
  The p-AMPK increased in response to both HIS and LIS, although the p-CaMKII and p-p38MAPK were increased only following HIS. Irrespective of exercise intensity, MCT1 and MCT4 mRNA was also transiently upregulated by both HIS and LIS. Direct exposure of the epitrochlearis muscle to 0.5mmol/L AICAR or 1mmol/L caffeine, which activated p-AMPK increased both MCT1 and MCT4 mRNA levels. When pAMPK was inhibited by dantrolene, neither MCT1 nor MCT4 mRNA was increased.
  
  
  CONCLUSIONS
  These results suggest that acute exercise-induced increases in MCT1 and MCT4 mRNA expression may be possibly mediated by AMPK activation, at least in part in fast-twitch muscle.
authors.affiliation: Laboratory of Exercise Physiology and Biochemistry, Graduate School of Sport and Exercise Sciences, Osaka University of Health and Sport Sciences (OUHS), Osaka, Japan.
authors.forename: Masaki
authors.initials: M
authors.lastname: Takimoto
authors.forename: Mirei
authors.initials: M
authors.lastname: Takeyama
authors.forename: Taku
authors.initials: T
authors.lastname: Hamada
mesh_terms: D055372:AMP-Activated Protein Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism*; D000620:Aminoimidazole Carboxamide / Q000031:analogs & derivatives / Q000494:pharmacology; D000818:Animals; D015153:Blotting, Western; D054732:Calcium-Calmodulin-Dependent Protein Kinase Type 2 / Q000378:metabolism*; D003620:Dantrolene / Q000494:pharmacology; D005786:Gene Expression Regulation / Q000187:drug effects; D008297:Male; D027501:Monocarboxylic Acid Transporters / Q000378:metabolism*; D009124:Muscle Proteins / Q000378:metabolism*; D009125:Muscle Relaxants, Central / Q000494:pharmacology; D018482:Muscle, Skeletal / Q000378:metabolism* / Q000502:physiology; D010766:Phosphorylation / Q000187:drug effects; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D060888:Real-Time Polymerase Chain Reaction; D012265:Ribonucleotides / Q000494:pharmacology; D015398:Signal Transduction / Q000187:drug effects; D013550:Swimming / Q000502:physiology*; D027981:Symporters / Q000378:metabolism*; D013997:Time Factors; D048051:p38 Mitogen-Activated Protein Kinases / Q000378:metabolism*; D000099233:Monocarboxylate Transport Protein 1
chemical_list: D055372:AMP-Activated Protein Kinases; D000620:Aminoimidazole Carboxamide; D054732:Calcium-Calmodulin-Dependent Protein Kinase Type 2; D003620:Dantrolene; D027501:Monocarboxylic Acid Transporters; D009124:Muscle Proteins; D009125:Muscle Relaxants, Central; D012333:RNA, Messenger; D012265:Ribonucleotides; D027981:Symporters; D048051:p38 Mitogen-Activated Protein Kinases; D000099233:Monocarboxylate Transport Protein 1; C516342:Slc16a3 protein, rat; C031143:AICA ribonucleotide
keywords: 5-aminoimidazole-4-carboxamide-1-beta-D-ribofuranoside; 5′-adenosine-activated protein kinase; ACC; AICAR; AMPK; Acetyl-CoA carboxylase; Acute exercise; CaMKII; MCT; MCTs; PGC1α; Signaling; Skeletal muscle; calcium/calmodulin-dependent kinase II; monocarboxylate transporters; p38 mitogen-activated protein kinase; p38MAPK; peroxisome proliferator activated receptor gamma coactivator