Reperfusion‑targeted AnxA1sp restores mitochondrial resilience through mitoKATP activation to limit diabetic...

Diabetes exacerbates myocardial ischemia-reperfusion (I/R) injury and undermines conventional cardioprotective stimuli, largely via mitochondrial dysfunction and impaired antioxidant defenses. While the annexin A1-derived tripeptide (AnxA1sp) exhibits potent anti-inflammatory and cytoprotective properties in nondiabetic settings, its therapeutic efficacy and underlying mechanisms against I/R injury in the uniquely vulnerable diabetic myocardium remain poorly characterized.

A type 2 diabetes rat model, induced by a high-fat/high-sucrose diet and low-dose streptozotocin, was subjected to in vivo LAD occlusion or ex vivo Langendorff I/R. AnxA1sp (10 µM) was administered at the onset of reperfusion, either alone or with the mitoKATP blocker 5-hydroxydecanoate (5-HD). To evaluate efficacy and mechanism, we systematically assessed myocardial infarction, hemodynamic recovery, oxidative stress burden (ROS, MDA, SOD), mitochondrial bioenergetics (ATP, respiratory chain activity, ΔΨm, mPTP dynamics), and apoptotic signaling, alongside Sirt3/Kir6.1 expression profiles.

In vivo, AnxA1sp administration significantly restricted infarct size (by ~ 12-15 absolute %, P < 0.01) and rescued systolic function (LVEF + 8-12%, P < 0.05), accompanied by a marked decline in myocardial injury enzymes (CK-MB, LDH; both P < 0.05). Similarly, in the ex vivo diabetic heart, AnxA1sp enhanced hemodynamic recovery (LVDP + 25-35%, P < 0.01) and limited tissue necrosis. Across both models, the peptide profoundly blunted oxidative stress (ROS/MDA reduced by ~ 20-40%, P < 0.01) while restoring intrinsic antioxidant capacity (SOD + 20-30%, P < 0.05). Crucially, AnxA1sp preserved mitochondrial integrity-evidenced by stabilized membrane potential (ΔΨm + 25-35%, P < 0.01), delayed mPTP opening, and replenished ATP stores (+ 20-30%, P < 0.05)-which concurrently abrogated cytochrome c release and apoptotic signaling. Notably, the pharmacological blockade of mitoKATP with 5-HD effectively abolished these cardioprotective and bioenergetic benefits (all P < 0.05 vs. AnxA1sp). Furthermore, AnxA1sp significantly upregulated Sirt3 and Kir6.1 protein expression (both P < 0.05), mechanistically linking channel activation to deacetylase pathways.

Targeting reperfusion with AnxA1sp confers robust, mitochondria-centric cardioprotection against diabetic I/R injury. By preserving redox and bioenergetic homeostasis, the peptide markedly limits infarction and rescues cardiac function. Crucially, this protection is strictly dependent on a novel mitoKATP-Sirt3 mechanistic axis. These findings establish AnxA1sp as a highly promising adjunct candidate for reperfusion therapy in high-risk diabetic populations.