Redox-Driven Blood-Nerve Barrier Dysfunction in Diabetic Peripheral Neuropathy: Mechanisms and Therapeutic Opportunities.

Diabetic peripheral neuropathy (DPN) remains a leading cause of disability in diabetes, yet current care is largely symptomatic and does not directly address early neurovascular-immune pathology. This narrative review synthesizes clinical, redox, vascular, and immunological evidence into a peripheral nerve neurovascular unit (PNVU)/blood-nerve barrier (BNB)-centered framework for DPN. First, the review outlines the diagnostic and translational endpoint landscape of DPN, emphasizing that commonly used clinical, neurophysiological, small-fiber, and imaging-based tools capture important disease domains but do not directly assess early BNB dysfunction. It then reviews the anatomical and functional basis of the PNVU and BNB, including endoneurial microvascular endothelial cells, pericytes, basement membrane components, immune cells, and tight-junction proteins. Next, it discusses how chronic hyperglycemia and dyslipidemia drive metabolic-to-vascular coupling, redox imbalance, antioxidant defense failure, advanced glycation end products (AGEs), receptor for AGEs (RAGE), and nuclear factor-κB (NF-κB) signaling, endothelial activation, leukocyte recruitment, macrophage polarization, and junctional disassembly, culminating in increased BNB permeability and exposure of peripheral nerves to pro-inflammatory and neurotoxic mediators. Finally, it evaluates incretin-based therapies-including glucagon-like peptide-1 receptor agonists (GLP-1RAs), dipeptidyl peptidase-4 inhibitors (DPP-4 inhibitors, DPP-4is), and emerging multi-agonists-as potential modulators of oxidative and inflammatory stress within this framework. Although semaglutide and related agents show mechanistic plausibility and preclinical promise, direct evidence for incretin-mediated BNB stabilization in human DPN remains limited. By reframing DPN as a redox-driven neurovascular-immune disorder, this review highlights barrier-focused biomarkers, translational endpoints, and hypothesis-generating therapeutic opportunities that require clinical validation.