ABSTRACT
Objective To investigate the expression of peroxisome proliferator-activated rec eptor γ (PPARγ) and glucokinase (GK) induced by Wnt signaling pathway in mice NIT-1 β-cells,and to explore the interaction between PPARγ and Wnt signaling pathways.Methods Recombinant Wnt3a protein was applied to NIT-1 beta-cells to activate Wnt signaling pathway.The expression of PPARγ was determined by real-time PCR and Western blotting.The expression of GK was determined by real time PCR.Results Wnt3a rapidly activated Wnt/β-catenin/TCF signaling pathway,and increased PPARγ and GK mRNA expression by 41.2％ and 65.0％ in NIT-1cells,with PPARγ protein expression increasing by 97.8％ (P＜0.01).These effects were abrogated by Wnt and PIK3 inhibitors,dickkopf 1 and wortmannin treatment (P＜ 0.01).Conclusions PPARγ and GK can be upregulated by Wnt singnaling,and the effects might partially be PI3K-dependent.
ABSTRACT
Objective To establish whether Wnt-signaling pathway plays a role in mice β-cell function and/or survival in vitro. Methods Mice NIT-1 beta cells were cultured in media with glucose concentration of 33.3 mmol/L and the cytokines interleukin-1β, interferon-γand tumor necrosis factor-α with or without the addition of purified Wnt3a protein in vitro. Subsequently, β-cell apoptosis by Tunnel and flow cytometry, and β-cell proliferation by BrdU were analyzed. Total RNA was extracted to measure gene expressions by real-time PCR.Results Incubations of NIT-1 cells with high glucose and cytokines resulted in an increase in β-cell apoptosis and decrease in β-cell proliferation (P<0.01). In contrast, treatment with Wnt3a protein protected β-cell from glucose and cytokines-induced apoptosis through up-regulating the expressions of above Pitx2、 TCF7L2. Conclusions Wnt-signaling regulates the proliferation of pancreatic β-cell, and protectes β-cell from glucotoxicity and cytokine toxicity with respect to proliferation and apoptosis.