Thiazolidinediones can rapidly activate AMP-activated protein kinase in mammalian tissues.
Thiazolidinediones (TZDs) are insulin-sensitizing agents used in the treatment of type 2 diabetes. A widely held view is that their action is secondary to transcriptional events that occur when TZDs bind to the nuclear receptor PPARgamma in the adipocyte and stimulate adipogenesis. It has been proposed that this increases insulin sensitivity, at least in part, by increasing the expression and release of adiponectin, an adipokine that activates the fuel-sensing enzyme AMP-activated protein kinase (AMPK). In this study, we report that TZDs also acutely activate AMPK in skeletal muscle and other tissues by a mechanism that is likely independent of PPARgamma-regulated gene transcription. Thus incubation of isolated rat EDL muscles in medium containing 5 microM troglitazone for 15 min (too brief to be attributable to transcription) significantly increased pAMPK and pACC. At a concentration of 100 microM, troglitazone maximally increased these parameters and caused twofold increases in 2-deoxy-d-glucose uptake and the oxidation of exogenous [(14)C]palmitate. Time course studies revealed that troglitazone-induced increases in pAMPK and pACC abundance at 15 min were paralleled by an increase in the AMP-to-ATP ratio and that by 60 min all of these parameters had returned to baseline values. Increases in pAMPK and pACC were also observed in skeletal muscle, liver, and adipose tissue in intact rats 15 min after the administration of a single dose of troglitazone (10 mg/kg, ip). Likewise, troglitazone and another TZD, pioglitazone, caused rapid increases in pAMPK and pACC of equal magnitude in Swiss 3T3 fibroblasts with and without sufficient PPARgamma to mediate the expression of target genes. The results indicate that TZDs can act within minutes to activate AMPK in mammalian tissues. They suggest that this effect is associated with a change in cellular energy state and that it is not dependent on PPARgamma-mediated gene transcription.
LeBrasseur
Nathan K
NK
Diabetes and Metabolism Research Unit, Boston University School of Medicine, 650 Albany St., X-820, Boston, MA 02118, USA.
Kelly
Meghan
M
Tsao
Tsu-Shuen
TS
Farmer
Stephen R
SR
Saha
Asish K
AK
Ruderman
Neil B
NB
Tomas
Eva
E
D055372:AMP-Activated Protein Kinases; D000103:Acetyl-CoA Carboxylase / Q000378:metabolism; D000244:Adenosine Diphosphate / Q000378:metabolism; D000249:Adenosine Monophosphate / Q000378:metabolism; D000255:Adenosine Triphosphate / Q000378:metabolism; D000818:Animals; D002839:Chromans / Q000494:pharmacology*; D004789:Enzyme Activation; D005227:Fatty Acids / Q000378:metabolism; D005947:Glucose / Q000378:metabolism; D007004:Hypoglycemic Agents / Q000494:pharmacology*; D066298:In Vitro Techniques; D008297:Male; D051379:Mice; D009097:Multienzyme Complexes / Q000378:metabolism*; D018482:Muscle, Skeletal / Q000187:drug effects* / Q000201:enzymology* / Q000378:metabolism; D010084:Oxidation-Reduction; D047495:PPAR gamma / Q000378:metabolism; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism*; D051381:Rats; D017207:Rats, Sprague-Dawley; D041701:Swiss 3T3 Cells; D045162:Thiazolidinediones / Q000494:pharmacology*; D000077288:Troglitazone
D002839:Chromans; D005227:Fatty Acids; D007004:Hypoglycemic Agents; D009097:Multienzyme Complexes; D047495:PPAR gamma; D045162:Thiazolidinediones; D000249:Adenosine Monophosphate; D000244:Adenosine Diphosphate; D000255:Adenosine Triphosphate; D017346:Protein Serine-Threonine Kinases; D055372:AMP-Activated Protein Kinases; D000103:Acetyl-CoA Carboxylase; D000077288:Troglitazone; D005947:Glucose