Abnormally Elevated PKCδ Delays Diabetic Wound Healing by Inhibiting the GAD1-GABA Pathway.

Background: Diabetic foot ulcer (DFU) represents a challenging complication of diabetes mellitus, characterized by slow healing processes. Protein kinase C delta (PKCδ) has been identified as a significant factor in the pathogenesis of various diabetic complications, including DFU. However, the precise underlying mechanisms remain to be fully elucidated.

Methods: Human umbilical vein endothelial cells (HUVECs) were cultivated under high glucose conditions and PKCδ was knocked down by siRNA. The proliferation, migration, and tube formation of HUVECs were detected. A metabolomics sequencing was done to identify potential metabolites contributing to the changes. HUVECs proliferation, migration, tube formation, and apoptosis were detected after regulating the production of selected metabolite. And finally, the effect of the metabolite on diabetic wound healing was detected.

Results: In vitro, knockdown of PKCδ upregulated glutamate decarboxylase 1 (GAD1) expression and gamma-aminobutyric acid (GABA) levels, which enhanced proliferation, migration, and tube formation and suppressed apoptosis of HUVECs under high glucose conditions. Interestingly, inhibition of GAD1 in normal glucose-treated HUVECs resulted in decreased proliferation, migration, tube formation, and increased apoptosis. Furthermore, in vivo experiments demonstrated that topical administration of GABA accelerated the healing of diabetic wounds in streptozotocin-induced type 2 diabetes mellitus mice, manifested as higher angiogenesis and proliferation.

Conclusion: The inhibition of GAD1-GABA pathway by PKCδ suppresses the proliferation, migration, tube formation and promotes the apoptosis of endothelial cells under high glucose and leads to delayed diabetic wound healing.