Abstract:

Objective To discuss the effect of metformin on the hypertrophy of the H9C2 cardiomyocytes induced by isoproterenol （ISO）， and to clarify its possible molecular mechanism. Methods The H9C2 cells were cultured； 50 μmol·L^－1 ISO was used to establish the cardiomyocyte hypertrophy model，and they were used as ISO group；the cells without any treatment were used as control group. The expression levels of brain natriuretic peptide （BNP） in the H9C2 cardiomyocytes in two groups were detected by Western blotting method.The cells were divided into control group， ISO group， ISO+metformin group， and metformin group.The viabilities of the H9C2 cardiomyocytes in two groups were detected by CCK-8 method； the optimal drug intervention concentration and time of metformin were selected；crystal violet staining was used to observe the morphology and cross-sectional area of the H9C2 cardiomyocytes；real-time fluorescence qualitative PCR（RT-qPCR） method was used to detect the expression levels of atrial natriuretic peptide （ANP） in the cells in various groups；the morphology of mitochondriums in the H9C2 cardiomyocytes was observed by fluorescence probes； Western blotting method was used to detect the expression levels of optic atrophy 1 （OPA1） and mitofusin（MFN） proteins in the cells in various groups. Results Compared with control group，the cross-sectional area of the H9C2 cardiomyocytes in ISO group was increased significantly （P<0.05）， and the expression level of BNP protein was increased significantly （P<0.05）， suggesting that the cardiomyocyte hypertrophy model was successfully modeled. The RT-qPCR results showed that compared with control group， the expression level of ANP mRNA in the cells in ISO group was increased（P<0.05）； compared with ISO group， the expression levels of ANP mRNA in the cells in metformin+ISO and metformin groups were decreased（P<0.05）. The mitochondrium fluorescence probe observing results showed that the punctate mitochondrum in control group showed green fluorescence， mostly short rod-shaped， and a few mitochondrum were filamentously connected；compared with control group， the number of punctate mitochondrum in the H9C2 cells in ISO group was significantly increased，and the numbers of punctate mitochondrium in ISO+meformin and meformin groups were significantly decreased.The Western blotting results showed that compared with control group，the expression levels of OPA1 and MFN2 proteins in the cells in ISO group were decreased （P<0.05）；compared with ISO group， the expression levels of OPA1 and MFN2 proteins in the cells in ISO+metformin and metformin groups were increased（P<0.05）. Conclusion Metformin can alleviate the ISO-induced hypertrophy of the H9C2 cardiomyocytes，and its mechanism may be related to improving the mitochondrium fusion by up-regulating the expression levels of OPA1 and MFN2 proteins.

Key words: Cardiomyocyte hypertrophy, Metformin, Mitochondrial fusion, Isoproterenol, Atrial natriuretic peptide