TAT-PBX1 Reverses Hyperglycemia Through β-Cell Regeneration and Functional Restoration in an STZ-Induced Diabetic Model

<b>Objective:</b> β-cell dysfunction and loss are major pathological determinants of impaired islet function and hyperglycemia in diabetes. Given the inability of current therapies to restore β-cell viability or glucose-responsive insulin secretion, this study aimed to investigate whether a cell-permeable PBX1 fusion protein (TAT-PBX1) could rescue streptozotocin (STZ)-induced β-cell injury and restore β-cell functional integrity. <b>Methods:</b> A TAT-PBX1 recombinant fusion protein was produced using a prokaryotic expression system. Its protective effects were assessed in STZ-treated MIN6 β cells and in a mouse model of STZ-induced diabetes, with the glucokinase (GK) activator dorzagliatin included as a positive control. We evaluated β-cell apoptosis, DNA damage, ATP and NAD⁺/NADH levels, insulin signaling (IRS1/PI3K/Akt), and the expression of PDX1 and GK. Glucose-stimulated insulin secretion (GSIS), glucose tolerance, islet morphology, and β-cell proliferation were also examined in vivo. <b>Results:</b> TAT-PBX1 was detectable and significantly enriched in pancreatic tissue and mitigated STZ-induced cytotoxicity by reducing DNA damage, PARP1-associated energy depletion, and β-cell apoptosis. It restored intracellular ATP and NAD⁺/NADH ratios and reactivated IRS1/PI3K/Akt signaling. TAT-PBX1 further enhanced PDX1 protein levels and upregulated GK, resulting in improved glucose uptake and GSIS. In addition, it increased Ki67⁺ β-cell proliferation. In diabetic mice, TAT-PBX1 improved glucose tolerance, preserved islet morphology and number, and improved insulin signaling responsiveness. <b>Conclusions:</b> TAT-PBX1 restores β-cell function through coordinated protection of cellular metabolism and insulin signaling, leading to improved β-cell survival, glucose responsiveness, and regenerative capacity. These findings support TAT-PBX1 as a promising molecular strategy for β-cell-protective and β-cell-restorative diabetes therapy.