Chrysin loaded nanovesicles ameliorated diabetic peripheral neuropathy. Role of NGF/AKT/GSK-3β pathway

Diabetic peripheral neuropathy (DPN) is a common diabetic complication. Chrysin (CHY) has many biological properties but poor oral bioavailability. This study investigates the effect of CHY and CHY-loaded nanovesicles (CHY-NVs) on streptozotocin (STZ)-induced DPN in rats. CHY-NVs were prepared by using film hydration method. The formula with the best entrapment efficiency%, lowest particle size, highest zeta potential, and highest in vitro CHY released profile was selected, characterized by Differential scanning calorimetry, Fourier transformation infrared spectroscopy analysis, and examined by Transmission electron microscope. Acute toxicity test, pharmacokinetic study and experimental model of diabetes mellitus were performed on the selected formulation. Wistar rats were considered diabetic by administration of a single intraperitoneal dose of STZ (50 mg/kg). 48 h after STZ administration, hyperglycemic rats were randomly assigned into four groups, one group of untreated hyperglycemic rats and the other three groups received daily oral doses of unloaded NVs, CHY-NVs (25 mg/kg), and CHY-NVs (50 mg/kg), respectively for 21 days. Moreover, five additional groups of healthy rats received: distilled water (control), free CHY, unloaded NVs, and CHY-NVs respectively for 21 days. CHY and CHY-NVs maintained body weight and reduced STZ-induced behavioral changes in rotarod, hind paw cold allodynia, tail cold allodynia, tail flick, and hot plate tests. CHY and CHY-NVs lowered blood glucose, glycated hemoglobin, elevated serum reduced glutathione (GSH), and reduced plasma malondialdehyde (MDA) levels. CHY-NVs elevated phosphatidylinositol 3-kinase (Pi3k), phosphorylated protein kinase B (p-AKT), and reduced nuclear factor kappa B (NF-κB), interleukin-6 (IL-6) in sciatic nerve homogenate. CHY and CHY-NVs increased nerve growth factor (NGF) and decreased glycogen synthase kinase-3β (GSK-3β) gene expressions in the sciatic nerve. In conclusion, CHY and CHY-NVs ameliorated STZ-induced DPN behavioral and histopathological changes via attenuating hyperglycemia, exerting anti-oxidant, anti-inflammatory effects, activating NGF/p-AKT/GSK-3β pathway, and its anti-apoptotic effect. The best pharmacokinetic profile and therapeutic effect was observed in rats treated with CHY-loaded NVs.