The objective of this study was to assess the role of AMPK in intramuscular fat(IMF) and fiber type in chicken muscle. The chickens were slaughtered and their muscles were collected at the ages of 4, 8, and 16 weeks so as to determine the IMF contents, as well as the expression levels of AMPK subunits, regulators of adipogenesis. In addition, the myosin heavy chains(My HCs) in thigh muscle tissues were also measured. The results showed that the IMF contents in 16-week old chickens were higher than those in 4 and 8-week-old chickens(P<0.05).The expression levels of fatty acid synthase(FAS) and fatty aicd translocase CD36(FAT/CD36) m RNA were increased significantly in samples collected at the ages of4 and 16 weeks(P<0.05). The expression levels of My HC IIa and IIb differed significantly among all the developmental stages(P <0.05). The AMPKα2, AMPKγ1,and AMPKγ3 m RNA levels were dramatically decreased with the increase of age(P <0.05). To examine the role of AMPK in adipogenesis regulation, the SV cells were cultured in an adipogenesis medium and treated with AICAR and Compound C respectively, the specific activator and inhibit of AMPK. The Compound C induced dramatically a greater expression of C/EBPβ, SREBP1 and PPARγ(P <0.05). In conclusion, the expression of AMPKα2, AMPKγ1, and AMPKγ3 m RNA is significantly correlated with the adipogenesis in skeletal muscle of chickens.
Intramuscular fat(IMF) content in chickens significantly contributes to meat quality. The main objective of this study was to assess the expression of calcineurin(Ca N) and Ca2+/calmodulin-dependent protein kinase(Ca MK) in lipogenesis in chicken muscle. The chickens were slaughtered and sampled at the ages of4, 8, and 16 weeks, respectively. IMF content and the expression of Ca N subunits and Ca MK isoforms were measured in thigh muscle tissue. The results showed that the IMF contents were higher in chickens at the age of 16 weeks compared with those in chickens at the ages of 4 and 8 weeks(P <0.05). The expression levels of fatty acid synthase(FAS) and fatty acid translocase CD36(FAT/CD36)m RNA in 16-week-old chickens were all significantly up-regulated compared with those in 4-week-old chickens(P<0.05). The m RNA levels of Ca NB and Ca MK IV in 16-week-old chickens were significantly lower than those in 4-week-old chickens(P<0.05). But the Ca MK II m RNA levels in 16-week-old chickens were significantly higher than those in 4-week-old chickens(P <0.05). To investigate the roles of Ca MK and Ca N in adipogenesis, SV cells were incubated in standard adipogenesis medium for 24 h and treated with specific inhibitor of Ca MK and Ca N. The expressions of CCAAT/enhancer binding protein β(C/EBPβ), sterol regulatory elementbinding protein 1(SREBP1) and peroxisome proliferation-activated receptor γ(PPARγ) were dramatically enhanced by Cs A and Ca N inhibitor(P <0.05). KN93,a Ca MK II inhibitor, dramatically repressed the expression of those lipogenic genes(P<0.05). All the results above indicated that Ca N and Ca MK had different effects on adipogenesis in the muscle of chickens.
