Effects And Mechanism Of ATP-sensitive Potassium Channels On The Proliferation And Differentiation Of Rat Preadipocytes

Part1 Involvement of ATP-sensitive potassium channels in the proliferation and differentiation of rat preadipocytesObjective: To investigate the effects of ATP-sensitive potassium channels on the proliferation and differentiation of rat preadipocytes.Methods: We discriminated the subtype of sulphonylurea receptor (SUR) mRNA, which is the receptor of ATP-sensitive potassium channels, in brain and adipose tissue, preadipocytes and adipocytes obtained by inducing for 5 days of rat. The expression of sulphonylurea receptor mRNA in preadipocytes and adipocytes obtained by inducing for 5 days and the effects of the inhibitor (glibenclamide) and opener (diazoxide) of ATP-sensitive potassium channels on the expression of SUR mRNA in preadipocytes were measured by Real-time Q-PCR. Preadipocytes proliferation and cell cycle were measured by MTT spectrophotometry and flow cytometer. The content of lipid was measured by Oil Red O staining , and cell diameter was determined by Image-Pro plus5.0 software.Results: SUR2 mRNA and SUR1 mRNA were expressed in brain tissue. SUR2 mRNA, not SUR1 mRNA was expressed in adipose tissue, preadipocytes and adipocytes obtaining by inducing 5 days, and the expression in adipocytes was obviously higher than it in preadipocytes. Glibenclamide inhibited the expression of SUR2 mRNA in preadipocytes, promoted preadipocytes proliferation in a dose-dependent manner, increased the cell percentages in G2/M+S phase, increased lipid content, augmented adipocyte diameter. But the actions of diazoxide were contrary to those of glibenclamide.Conclusion: ATP-sensitive potassium channels can regulate the proliferation and differentiation in preadipocytes. Part 2. Mechanism that ATP-sensitive potassium channels involve in the proliferation and differentiation of rat preadipocytesObjective: To explore the mechanism that ATP-sensitive potassium channels involve in the proliferation and differentiation of rat preadipocytes.Methods: After preadipocytes in the course of induction were treated by diazoxide and glibenclamide for 5 days, the expression of peroxisome proliferator-activated receptorγmRNA (PPARγmRNA) and leptin mRNA was estimated by RT-PCR. P21 and P27 in preadipocytes treated by diazoxide and glibenclamide were determined by western blot.Results: In the course of the differentiation in rat preadipocytes, leptin mRNA in the diazoxide group increased greatly (p<0.05), while leptin mRNA in the glibenclamide group decreased obviously (p<0.05). PPARγmRNA in glibenclamide group was raised (p<0.05), compared with control group. But PPARγmRNA in diazoxide group was lowered (p<0.05). When diazoxide took effect on the preadipocytes, P21 and P27 were promoted, whereas P21 and P27 were inhibited in glibenclamideConclusion: ATP-sensitive potassium channels involve in the proliferation of rat preadipocytes.This might be related to the increasing of P21, P27 and the decreasing of PPAR-γmRNA.