CXXC4 Mediates Glucose-induced Proliferation In Rat Pancreatic β-cells

Background and objective Islet beta cell proliferation is the main source of islet beta cells in adulthood.Glucose is an important factor promoting early compensatory proliferation of islet β cells,but the exact mechanism of regulating pancreatic β-cell proliferation is still unclear.In our previous study,we promoted the proliferation of islet βcell on rat through short-term high glucose perfusion,on which we found that the expression of CXXC4 which is a negative regulator of the canonical Wnt signaling pathway was significantly decreased It was mainly studied in the field of oncology,whether it involved in the proliferation of isletβcell has not been reported.This study aimed to determine whether the CXXC4 involved in high glucose-induced pancreatic β-cell proliferation and to explore the possible mechanism.Then to provide a new theoretical basis and therapeutic target for the treatment of diabetes.Materials and Methods Firstly,in order to study the expression of CXXC4 gene in the proliferation of islet β-cell induced by glucose in vivo.50% glucose was infused into the jugular vein to promote the proliferation of islet on rat in a short-term,secondly,to study the influence of glucose on islet β-cells in vitro,islet β-cell tumor cell line INS-1 cells and isolated rat primary islet cells were cultured with different glucose concentrations,then using CCK-8 and Ed U to test the cell proliferation.The expression of CXXC4 gene and protein and the downstream gene of Wnt signaling pathway were detected by Realtime PCR and Western Blot.Then,after overexpression of CXXC4 in INS-1 cells by adenovirus transfection,CCK-8 and flow cytometry were applied to tested the proliferation and cell-cycle.The expression changes of β-catenin and Cyclin D1 and Cyclin D2 in the Wnt signaling pathway were detected by Western Blot.Results 1.Short-term high glucose infusion could induce the proliferation of rat islet with decreased expression.of CXXC4 2.High glucose promote the proliferation of INS-1 cells and inhibit the expression of CXXC4 3.High glucose promotes the proliferation of primary cell isolated from rat islets and decreases the expression of CXXC4.4.Overexpression of CXXC4 could inhibit the proliferation of INS-1 cells induced by high glucose.5.Overexpression of CXXC4 inhibits the activation of the canonical Wnt signaling pathway and the expression of Cyclin D2 in INS-1 cellsConclusion 1.Glucose promotes the proliferation of islet β cells by down-regulating the expression of CXXC4.2.Wnt signaling pathway with the downstream cyclin D2 involved in the inhibition mediated by CXXC4 on β cell proliferation induced by high glucose.