Overexpression of miR-22 attenuates oxidative stress injury in diabetic cardiomyopathy via Sirt 1

Background/Aims: Oxidative stress injury is believed to be important in diabetic car- diomyopathy. Recent evidence indicates that miR- 22 plays an important role in vari- ous cardiovascular diseases, but the protective role of miR- 22 in diabetic cardiomyopathy remains undetermined. Methods: Diabetes was induced in male C57BL/6 mice by intraperitoneal injection with streptozotocin combined with a high- fat diet, and miR- 22 was overexpressed fol- lowing transfection with adeno- associated virus. Cardiac function was assessed by echocardiography and a cardiac catheter system. In vitro study, H9c2 cells were treated with normal or high glucose (HG), and cell viability or apoptosis was detected using the Cell Counting Kit- 8 (CCK- 8) assay and flow cytometry, respectively. Reactive oxygen species, malondialdehyde, and superoxide dismutase were also detected in diabetic mice and H9c2 cells. The expression level of miR- 22 was detected by real- time PCR. The protein expression of Sirt 1, oxidative stress injury- related proteins (GRP78, CHOP, ATF 3), and apoptosis- related proteins Bax/Bcl- 2, cl- casp- 9/casp- 9, and cl- casp- 3/casp- 3 were determined by Western blotting analysis. Results: HG- induced oxidative stress injury and apoptosis were observed in H9c2 cells, which were ameliorated by miR- 22. Cardiac dysfunction and severely altered heart structure were also observed in diabetic mice and were dramatically reversed by overexpression of miR- 22. The expression of Sirt 1 decreased significantly in diabetic mice and HG- treated H9c2 cells. Overexpression of miR- 22 restored the level of Sirt 1. Bioinformatics analysis predicted that Sirt 1 was a potential target gene of miR- 22. Luciferase reporter assay verified that miR- 22 promoted Sirt 1 expression by direct binding to the Sirt 1 3′untranslated repeats. Upregulation of Sirt 1 could improve cell viability and attenuate oxidative stress injury and apoptosis in the HG- treated H9c2 cells, similar to the effect of miR- 22. However, the protective effects of miR- 22 against HG- induced oxidative stress injury and apoptosis were abrogated by knockdown of Sirt 1. Conclusions: Overexpression of miR- 22 can attenuate oxidative stress injury in dia- betic cardiomyopathy by upregulation of Sirt 1 in vivo and in vitro.