Abstract: Objective To investigate the downstream molecular mechanisms by which the adiponectin(APN)/APPL1 signaling axis alleviates diabetic vascular endothelial injury. Methods APPL1-knockout diabetic mice were treated with APN. Hindlimb ischemia models were established to evaluate vascular regeneration. Endothelial injury and apoptosis were assessed by Western blot and caspase-3 activity. Human umbilical vein endothelial cells (HUVECs) were transfected with APPL1 siRNA to examine the effects of APN on apoptosis and permeability. Transcriptomic profiling was performed followed by GO and KEGG enrichment analyses. Selected targets were validated by RT-qPCR. Results APN markedly improved hindlimb blood flow recovery, increased CD31 expression and suppressed caspase-3 activity in diabetic mice, whereas these protective effects were completely abrogated in the absence of APPL1(P＜0.01). Consistently, in HUVECs, APN reduced high glucose/high lipid-induced apoptosis and permeability, but APPL1 silencing abolished these injury-suppressive effects (P＜0.01). Transcriptomic analysis identified 1 559 genes regulated by the APN/APPL1 signaling axis, predominantly enriched in tight junctions, cell adhesion and Hippo signaling pathways. Validation studies highlighted Occludin, a central tight junction protein, whose expression was strictly dependent on APPL1. Conclusions APN alleviates diabetic vascular endothelial injury through an APPL1-dependent signaling mechanism, with Occludin emerging as a pivotal downstream molecular target.

Key words: adiponectin(APN), APPL1, diabetes, vascular endothelium, tight junction