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Hyperglycemia may induce diabetic cardiomyopathy (DC). In the current study, the mechanism underlying the alleviation of high glucose (HG)-induced impairments in the proliferation of H9c2 embryo cardiomyocyte proliferation by small ubiquitin-like modifier 2 (SUMO2) overexpression was investigated. H9c2 cell morphology was identified as classical long shuttle type by optical microscopy. The viability of HG-injured H9c2 cells was evaluated by a Cell Counting Kit-8 assay and the results indicated that viability was inhibited in a dose-dependent (5.6, 10, 20 and 30 mmol/l) and time-dependent (6, 12 and 24 h) manner. H9c2 cells treated with 20 mmol/l HG for 24 h were selected for subsequent experiments due to the extent of injury caused at a low density. Flow cytometry was conducted to confirm cell cycle arrest between G1/S phases and apoptosis promotion in HG-injured H9c2 cells, and the subsequent alleviating effect of SUMO2 overexpression on these HG-induced effects. Reverse transcription-quantitative polymerase chain reaction (RT-qPCR) and western blot analysis were performed to detect mRNA and protein expression levels of cell cycle-and apoptosis-associated factors. The results indicated that the expression ofthe cell cycle-associated factors CyclinA2 and C-Myc was upregulated, and cyclin-dependent kinase inhibitor 1a was downregulated. The expression of the apoptosis-associated factor Bcl-2 was upregulated, while Bcl-2-associated X and caspase-3 expression was downregulated, by SUMO2 overexpression. Furthermore, the effect of SUMO2 overexpression on the transforming growth factor (TGF)-β/Smad pathway was also determined using RT-qPCR and western blot analysis. The results indicated the mRNA and protein levels of TGF-β1 and Smad3 in HG-injured H9c2 cells were significantly decreased following SUMO2 overexpression. Thus, the results demonstrated that overexpression of SUMO2 may alleviate H9c2 cardiomyocyte cell cycle arrest and apoptosis promotion induced by HG via regulation of cell cycle- and apoptosis-associated factors, as well as inhibition of the TGF-β/Smad pathway. These results may therefore provide a novel strategy for the protection of cardiomyocytes and may aid the diagnosis and prognosis of patients with DC.