To test the hypothesis that neonatal GLP-1 exposure may program myosin heavy chain (MyHC) composition in adult skeletal muscle, two-day-old rats were transfected intramuscularly with vacant vector plasmid (VP), or recombinant plasmid expressing secretory GLP-1 at the doses of 60 µg (LG) and 120 µg (HG), respectively. Expression of GLP-1 mRNA was detected in muscles of both LG and HG rats 7 days after transfection, with more abundant GLP-1 transcript seen in LG rats. In accordance with the GLP-1 expression, LG rats demonstrated more significant responses to neonatal GLP-1 exposure. Small yet significant growth retardation was observed in LG rats, which is accompanied with significantly reduced serum insulin concentration at 8 weeks of age compared to VP rats. The responses of skeletal muscle were dependent on muscle type. Significant increase of PGC-1? and GLUT4 mRNA expression was detected in soleus of LG rats, whereas a MyHC type switch from ?B to ? was seen in gastrocnemius. These results indicate that neonatal exposure of healthy pups to ectopic GLP-1 causes growth retardation with decreased serum insulin as well as muscle type-dependent modifications in MyHC type composition and metabolic gene expression in adult rats.

Key Lab Animal Biochem Nanjing Agricultural Univ Nanjing

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