| AMP-activated protein kinase (AMPK) stimulates development of skeletal muscle and plays a main role on postmortem glycolysis. However, there are two isoforms of the AMPKa catalytic subunit, and their roles in development of skeletal muscle and glycolysis of postmortem muscle remain unclear. The objective was to identify the isoform specific roles of AMPK in development of skeletal muscl and postmorterm glycolysis. Wild type, AMPKα1, and AMPKα2knockout (ko) mice were used in the current study.To compared the patterns of the body weight development and the muscle weight between WT mice and AMPKα ko mice. AMPKaα1ko mice grew slower than that of wild-type mice at0d,7d and15d (P<0.05), the body weight of AMPKα1ko mice amount to19.92g,while the WT mice weight was23.98g at two month(adult), which was dramatically larger than that of AMPKα1ko mice(P<0.01); the difference between the AMPKα2ko mice and WT mice was not significant at0d,7d and15d. However, the body weight of WT mice (23.75g) was dramatically smaller than that of AMPKα2ko mice (28.38g) at two month(P<0.01). Compared to adult wild-type mice, both Vastu lateralis muscle weight and Gastroncnmius muscle weight of adult AMPKα1ko was more smaller (P<0.01), while both these two muscle weight of adult AMPKα2ko was larger than that of adult wild-type mice(P<0.01).The data of paraffin slice and HE stain demonstrated that the muscle fibre diameter of AMPKal ko Tibialis anterior muscle was smaller than that of wild-type mice at0d,7d and15d (P<0.05), while the difference between the AMPKα2ko mice and WT mice was not significant at the same time. At two month, the fibre diameter of AMPKal koTibialis anterior muscle was dramatically smaller than that of wild-type mice(P<0.01),while AMPKα2ko Tibialis anterior muscle fibre diameter was dramatically larger than that of wild-type mice(P<0.01). The difference of the muscle fibre diameter of Soleus muscle in adult mice was same as the Tibialis anterior muscle. Soleus muscle fibre diameter in adult AMPKal ko mice was samller than that in wild-type mice (P<0.01), While the muscle fibre diameter in Soleus muscle of adult AMPKa2ko mice was larger than that in adult wild-type mice (P<0.01). Compared to adult wild-type mice, adult AMPKal ko Soleus muscle fibre density was much greater(P<0.01), while the muscle fibre density in adult AMPKa2ko Soleus muscle was dramatically smaller(P<0.01). The muscle fibre number in Soleus muscle of adult AMPKal ko mice was samller than that in adult wild-type mice(P<0.01). However, the difference of muscle fibre number between adult AMPKa2ko mice and adult wild-type mice was not significant.The data of Western blots showed that AMPK activity was activated shortly and enhanced at20min and1h postmortem in both wild-type and AMPKal ko mice, On the contrary to AMPKal ko mice, no significant increase in AMPK activity over time was detected in AMPKa2ko muscle,In addition, the total content of AMPKa subunits which include both al and a2subunits was dramatically reduced after AMPKa2ko(P<0.01)but not al ko. ACC phosphorylation was increased at20min and1h postmortemin both Wild-type and AMPKal ko mice,which was highly correlated with AMPK phosphorylation.While there was no significant increase of ACC phosphorylation in AMPKa2ko mice (P<0O.01).To compared the index difference of postmortem glycolysis, we found:1) The pH decline in AMPKa2ko mice was less than wild-type mice, the difference was singnifcant between wild-type and AMPKa2ko mice (P<0.01). However, there was no difference in glycolysis between wild-type and AMPKal ko mice.2) Consistent with pH change, the content of lactate was largly increased both AMPKal ko and wild-type mice, while AMPKa2ko reduced lactate production, there was significant difference between AMPKa2ko and wild-type mice at20min (P<0.01).3) The glycogen content was reduced in AMPK a2ko mice compared to wild-type mice (p<0.01). While there was no difference between AMPKα1ko mice and wild-type mice.4) The glycolytic potential was higher in wild-type compared to AMPKa2ko mice (p<0.01), but there was no difference between wild-type and AMPKα1ko mice.In summary, our data demonstrate that AMPKα1catalytic subunit is the main regulator in skeletal muscle development, not AMPKa2subunit. AMPKa2subunit promote adult muscle hypertrophy and it is also an important regulator of postmortem glycolysis in muscle. |
