PI3K/Akt在C2C12肌细胞生脂转分化中的作用

Role of PI3K/Akt in The Adipogenic Trans-differentiation of C2C12 Myoblasts

本研究的主要目的在于探明PI3K/Akt通路在肌细胞生脂转分化中的调控作用.试验培养并诱导C2C12肌细胞生脂转分化,同时使用抑制剂Wortmannin处理细胞抑制PI3K的激活,或者使用特异性siR NA转染沉默细胞内源PI3K基因的表达,观察其对肌细胞生脂转分化的影响.结果表明,随着C2C12细胞的生脂转分化,PI3K蛋白(P55亚基和P85亚基)和其下游效应分子Akt的磷酸化水平,在转分化前期提高而在转分化后期明显降低.使用Wortmannin处理细胞能够有效抑制PI3K/Akt激活,这导致C2C12细胞的生脂转分化明显受到抑制,细胞内脂肪生成量显著降低,生脂基因PPARγ、C/EBPα、FABP4和FATP1的表达水平均显著下调.使用特异性siR NA转染细胞显著下调PI3K基因表达水平和蛋白质含量,同样明显抑制了C2C12细胞的生脂转分化.此外,在转分化过程中抑制PI3K/Akt的活性和表达还激活了Caspase-3并导致细胞凋亡.综合上述结果可以确认PI3K/Akt的正常表达和激活是肌细胞生脂转分化必不可少的.

The aim of this study was to explore the regulatory role of the PI3K/Akt pathway in adipogenic trans-differentiation of myoblasts. C2C12 myoblasts were cultured and, subsequently, induced for adipogenic trans-differentiation. During trans-differentiation, levels of phosphorylated PI3K （P85 and P55 subunits） were increased progressively with early differentiation, but significantly decreased during late-phase differentiation. There were no changes in Akt protein levels, but its phosphorylation levels changed similarly to those of PI3K. Wortmannin treatment of the cells efficiently suppressed PI3K/Akt activation, resulting in significant inhibition of adipogenesis and to varying extents, downregulated expression of several adipogenic genes （PPAR7, C/EBPa, FABP4 and FATP1）. In addition, silencing the PI3K gene by siRNA transfection also inhibited adipogenic trans-differentiation in C2C12 cells. Moreover, suppressing both activation and expression of PI3K/Akt induced apoptosis. Taken together, our findings indicated that the PI3K/Akt pathway plays a key role in adipogenic trans-differentiation ofmyoblasts.