Tirzepatide attenuates cardiac microvascular injury and ferroptosis-related lipid peroxidation in diabetic mice: endothelial responses in the context of partial PRKN silencing

Background Diabetic metabolic stress damages the cardiac microvasculature. We evaluated tirzepatide-associated cardiac and endothelial effects, including endpoint patterns after partial silencing of parkin RBR E3 ubiquitin protein ligase (PRKN) and lipidated microtubule-associated protein 1 light chain 3 beta (LC3B-II) accumulation during lysosomal blockade.Methods Male C57BL/6J mice received a normal diet, a high-fat diet (HFD), or HFD/streptozotocin (STZ); HFD and HFD/STZ cohorts received tirzepatide or vehicle for 8 weeks. Metabolic, cardiac, microvascular, lipid-peroxidation, iron, and protein endpoints were assessed; ultrastructure was evaluated descriptively. Human cardiac microvascular endothelial cells (HCMECs) underwent high glucose/palmitic acid (HG/PA), PRKN-silencing, and bafilomycin A1 (BafA1) experiments.Results In HFD/STZ mice, tirzepatide improved selected glycemic and lipid measures and attenuated ventricular dilation, systolic dysfunction, myocardial fibrosis, and microvascular injury. Myocardial 4-hydroxynonenal, malondialdehyde, and ferrous iron were lower, and mitochondrial quality-control and ferroptosis-related protein profiles shifted toward control levels. In HG/PA-exposed HCMECs, tirzepatide increased the JC-1 aggregate/monomer ratio, decreased 4-hydroxynonenal and acyl-CoA synthetase long-chain family member 4, and increased glutathione peroxidase 4 and ferritin heavy chain 1. Among tirzepatide-treated cultures, endpoints were less favorable with partial PRKN silencing than with control small interfering RNA, although treatment-associated differences remained within the PRKN-silenced background. BafA1 increased LC3B-II in control and HG/PA + tirzepatide cultures; the increase under HG/PA alone was not significant.Conclusions Tirzepatide was associated with less cardiac microvascular injury and ferroptosis-related lipid peroxidation. PRKN-silencing status was associated with endothelial endpoint patterns after tirzepatide treatment; effect modification and requirement were not established. Receptor dependence, mitophagic flux, and independence from systemic metabolic improvement remain unresolved.