Inhibition Of Gsk-3 Beta Restores Delayed Gastric Emptying In Obesity-Induced Diabetic Female Mice

Diabetic gastroparesis (DG) is a clinical syndrome characterized by delayed gastric emptying (DGE). Loss of nuclear factor erythroid 2-related factor 2 (Nrf2) is associated with reduced neuronal nitric oxide synthase-alpha (nNOS alpha)-mediated gastric motility and DGE. Previous studies have shown that nuclear exclusion and inactivation of Nrf2 is partly regulated by glycogen synthase kinase 3 beta (GSK-3 beta). In the current study, the molecular signaling of GSK-3 beta-mediated Nrf2 activation and its mechanistic role on DG were investigated in high-fat diet (HFD)-induced obese/Type 2 diabetes (T2D) female mice. Adult female C57BL/6J mice were fed with HFD or normal diet (ND) with or without GSK-3 beta inhibitor (SB 216763, 10 mg/kg body wt ip) start from the 14th wk and continued feeding mice for an additional 3-wk time period. Our results show that treatment with GSK-3 beta inhibitor SB attenuated DGE in obese/T2D mice. Treatment with SB restored impaired gastric 1) Nrf2 and phase II antioxidant enzymes through PI3K/ERK/AKT-mediated pathway, 2) tetrahydrobiopterin (BH4, cofactor of nNOS) biosynthesis enzyme dihydrofolate reductase, and 3) nNOS alpha dimerization in obese/T2 diabetic female mice. SB treatment normalized caspase 3 activity and downstream GSK-3 beta signaling in the gastric tissues of the obese/T2 diabetic female mice. In addition, GSK-3 beta inhibitor restored impaired nitrergic relaxation in hyperglycemic conditions. Finally, SB treatment reduced GSK3 marker, pTau in adult primary enteric neuronal cells. These findings emphasize the importance of GSK-3 beta on regulating gastric Nrf2 and nitrergic mediated gastric emptying in obese/ diabetic rodents.NEW & NOTEWORTHY Inhibition of glycogen synthase kinase 3 beta (GSK-3 beta) with SB 216763 attenuates delayed gastric emptying through gastric nuclear factor erydroid 2-related factor 2 (Nrf2)phase II enzymes in high-fat diet-fed female mice. SB 216763 restored impaired gastric PI3K/AKT/beta-catenin/caspase 3 expression. Inhibition of GSK-3 beta normalized gastric dihydrofolate reductase, neuronal nitric oxide synthase-alpha expression, dimerization and nitrergic relaxation. SB 216763 normalized both serum estrogen and nitrate levels in female obese/Type 2 diabetes mice. SB 216763 reduced downstream signaling of GSK-3 beta in enteric neuronal cells in vitro.