Caffeine activates preferentially alpha1-isoform of 5'AMP-activated protein kinase in rat skeletal muscle.
- Abstract Aim: Caffeine activates 5'AMP-activated protein kinase (AMPK), a signalling intermediary implicated in the regulation of glucose, lipid, and energy metabolism in skeletal muscle. Skeletal muscle expresses two catalytic alpha subunits of AMPK, alpha1 and alpha2, but the isoform specificity of caffeine-induced AMPK activation is unclear. The aim of this study was to determine which alpha isoform is preferentially activated by caffeine in vitro and in vivo using rat skeletal muscle. Methods: Rat epitrochlearis muscle was isolated and incubated in vitro in the absence or presence of caffeine. In another experiment, the muscle was dissected after intravenous injection of caffeine. Isoform-specific AMPK activity, the phosphorylation status of AMPKalpha Thr(172) and acetyl-CoA carboxylase (ACC) Ser(79), the concentrations of ATP, phosphocreatine (PCr), and glycogen, and 3-O-methyl-d-glucose (3MG) transport activity were estimated. Results: Incubation of isolated epitrochlearis muscle with 1 mM of caffeine for 15 min increased AMPKalpha1 activity, but not AMPKalpha2 activity; concentrations of ATP, PCr and glycogen were not affected. Incubation with 3 mM of caffeine activated AMPKalpha2 and reduced PCr and glycogen concentrations. Incubation with 1 mM of caffeine increased the phosphorylation of AMPK and ACC and enhanced 3MG transport. Intravenous injection of caffeine (5 mg kg(-1)) predominantly activated AMPKalpha1 and increased 3MG transport without affecting energy status. Conclusion: Our results suggest that of the two alpha isoforms of AMPK, AMPKalpha1 is predominantly activated by caffeine via an energy-independent mechanism and that activation of AMPKalpha1 increases glucose transport and ACC phosphorylation in skeletal muscle.
- Document Type:
- Reference
- Product Catalog Number:
- 07-303
- Product Catalog Name:
- Anti-phospho-Acetyl CoA Carboxylase (Ser79) Antibody - (Anti-phospho-Acetyl CoA Carboxylase (Ser79) Antibody)