4-HNE induces cell death through the VCP-related ubiquitination pathway in diabetic cardiomyopathy and the protective effect of metformin

Metformin is an approved anti diabetes drug and has potential cardioprotective effects. It is unclear whether the antioxidant effect plays a role in this process. The lipid peroxidation product 4-HNE has been implicated in the pathology of heart diseases, such as diabetic cardiomyopathy, although the exact mechanisms remain unclear. In this study, we identified 4-HNE protein adducts by mass spectrometry in cardiomyocytes, and investigated the mechanism of 4-HNE induced cell death and the protective effect of metformin in cardiomyocytes and diabetic cardiomyopathy models. We found that in the 4-HNE-treated H9C2 cells, 4-HNE covalently binds to the key protein VCP to mediate cardiomyocyte death. 4-HNE also inhibits the ATPase activity of VCP and disrupted its downstream signaling pathway, including increased ubiquitinated protein levels, unfolded protein response, and ultimately leads to cardiomyocyte death. In contrast, overexpression of VCP in H9C2 cardiomyocytes protected 4-HNE induced protein ubiquitination and cell death. Mass spectrometry analysis revealed that 4-HNE binds to VCP at residues K336. In addition, metformin reduced the ubiquitination and death of cardiomyocytes induced by 4-HNE through activation of Nrf2-GSTP1 pathway. In HFD-STZ diabetic cardiomyopathy mice, metformin treatment significantly improved cardiac function, reduced cardiac fibrosis and apoptosis, accompanied by a decrease in the levels of 4-HNE adducts and protein ubiquitination. Overall, our results show that 4-HNE directly binds to VCP and disrupts its signaling pathway, which ultimately leads to cardiomyocyte death. Metformin effectively alleviates the damaging effect of 4-HNE on diabetic cardiomyopathy both in vitro and in vivo, demonstrating potential therapeutic effects.