Lactylation-driven mitochondrial dysfunction promotes diabetic myocardial fibrosis via impairing mitophagy and activating TGF-β1

This study aimed to investigate the role and mechanisms of lactate-derived protein lactylation in promoting myocardial fibrosis in diabetic cardiomyopathy (DCM). We hypothesized that lactylation contributes to fibrosis through dual pathways: impairing PINK1/Parkin-mediated mitophagy and epigenetically activating the TGF-β1 profibrotic axis. Clinical analysis included 80 type 2 diabetes (T2DM) patients with fibrosis and 40 non-fibrotic T2DM controls. Experimental models included Streptozotocin -induced diabetic mice and primary cardiac fibroblasts exposed to high glucose/lactate. Molecular mechanisms were examined using co-immunoprecipitation, lactylation-specific assays, siRNA knockdown, and pharmacological inhibition of lactate dehydrogenase A (LDHA) with GSK2837808A. Fibrosis, mitochondrial function, and mitophagy were assessed via histology, hydroxyproline assay, Western blot, ATP/ROS detection, and echocardiography. Serum lactate was elevated in fibrotic T2DM patients. Diabetic mice showed increased myocardial lactate, suppressed PINK1/Parkin mitophagy, mitochondrial dysfunction (reduced ATP, elevated ROS), and enhanced fibrosis. Mechanistically, lactate induced HSP90 lactylation, disrupting its interaction with PINK1 and thereby contributing to mitophagy impairment. Concurrently, histone H3K18 lactylation enriched at the TGF-β1 promoter, leading to increased transcription and activation of the TGF-β1/Smad3 fibrotic cascade, as evidenced by elevated p-Smad3, α-SMA, collagen I/III, and enhanced fibroblast migration. In vivo , LDHA inhibition with GSK2837808A reduced lactate, improved mitophagy‑related markers, attenuated fibrosis, and improved cardiac function. In vitro, siRNA-mediated knockdown of LDHA or HSP90 suppressed TGF-β1 expression and fibroblast migration. Lactate-driven lactylation is associated with diabetic myocardial fibrosis through dual mechanisms—impairing mitophagy via HSP90 modification and epigenetically activating TGF-β1 via H3K18 lactylation. Targeting the lactate-lactylation-mitophagy-fibrosis axis may represent a potential experimental therapeutic strategy for DCM, though further validation in translational models and assessment of safety and specificity are warranted.