Objective Diabetic nephropathy (DN), also known as diabetic kidney disease (DKD), is a major chronic complication of diabetes and is the most frequent cause of kidney failure globally. A better understanding of the pathophysiology of DN would lead to the development of novel therapeutic options. Acrolein, an α,β-unsaturated aldehyde, is a common dietary and environmental pollutant. Design The role of acrolein and the potential protective action of acrolein scavengers in DN were investigated using high-fat diet/ streptozotocin-induced DN mice and in vitro DN cellular models. Methods Acrolein-conjugated proteins (Acr-PCs) in kidney tissues were examined using immunohistochemistry. Renin-angiotensin system (RAS) and downstream signaling pathways were analyzed using quantitative RT-PCR and Western blot analyses. Acr-PCs in DN patients were analyzed using an established Acr-PC ELISA system. Results We found an increase in Acr-PCs in kidney cells using in vivo and in vitro DN models. Hyperglycemia activated the RAS and downstream MAPK pathway, increasing inflammatory cytokines and cellular apoptosis in two human kidney cell lines (HK2 and HEK293). A similar effect was induced by acrolein. Furthermore, acrolein scavengers such as N-acetylcysteine, hydralazine, and carnosine could ameliorate diabetes-induced kidney injury. Clinically, we also found increased Acr-PCs in serum samples or kidney tissues of DKD patients compared to normal volunteers, and the Acr-PCs were negatively correlated with kidney function. Conclusions These results together suggest that acrolein plays a role in the pathogenesis of DN and could be a diagnostic marker and effective therapeutic target to ameliorate the development of DN.

Renal fibrosis is a hallmark of diabetic nephropathy (DN) and is characterized by an epithelial-to-mesenchymal transition (EMT) program and aberrant glycolysis. The underlying mechanisms of renal fibrosis are still poorly understood, and existing treatments are only marginally effective. Therefore, it is crucial to comprehend the pathophysiological mechanisms behind the development of renal fibrosis and to generate novel therapeutic approaches. Acrolein, an α-,β-unsaturated aldehyde, is endogenously produced during lipid peroxidation. Acrolein shows high reactivity with proteins to form acrolein-protein conjugates (Acr-PCs), resulting in alterations in protein function. In previous research, we found elevated levels of Acr-PCs along with kidney injuries in high-fat diet-streptozotocin (HFD-STZ)-induced DN mice. This study used a proteomic approach with an anti-Acr-PC antibody followed by liquid chromatography–tandem mass spectrometry (LC–MS/MS) analysis to identify several acrolein-modified protein targets. Among these protein targets, pyruvate kinase M2 (PKM2) was found to be modified by acrolein at Cys358, leading to the inactivation of PKM2 contributing to the pathogenesis of renal fibrosis through HIF1α accumulation, aberrant glycolysis, and upregulation of EMT in HFD-STZ-induced DN mice. Finally, PKM2 activity and renal fibrosis in DN mice can be reduced by acrolein scavengers such as hydralazine and carnosine. These results imply that acrolein-modified PKM2 contributes to renal fibrosis in the pathogenesis of DN.