Effects Of Adiponectin On Insulin Secretion Function And Apoptosis Of Islet β Cells

Objective: To observe the effects of adiponectin on insulin secretion function and cell apoptosis in pancreaticβcells exposed to high glucose level,and investigate the possible mechanism.Methods:Rat insulinoma cell line RIN-m5F (passage4-11)was cultured in RPMI 1640 medium supplemented with 15% heat-inactivated fetal bovine serum (FBS),100U/ml penicillin, 100μg/ml streptomycin and 2mmol/l glutamine in an incubator with saturated humidity in the atmosphere of 5% CO₂ at 37℃. Cells were cultured in 5.6mmol/L glucose and 16.7mmol/ L glucose respectively, with or without different concentration of recombinant rat globular adiponectin (0,30μg / L,100μg / L,500μg /L,2500μg /L) for 48 hours. Basal and high glucose-stimulated mediated insulin secretion (GSIS)in the medium was measured by radio-immunity assay( RIA ). UCP-2,PPARγmRNA expression inβcells was detected by RT-PCR. Cell apoptosis was detected by flow cytometric analysis and the protein expression level of cleaved Caspase 3 was detected by Western Blot.Results:1. Adiponectin did not affect basal and glucose- stimulated insulin secretion in the control group.2. Cells exposed to high glucose concentration showed an significantly increased basal(P <0.05)and a significantly decreased glucose-stimulated insulin secretion (P <0.05) compared with the control group. Glucose-stimulated insulin secretion in the high glucose treated group significantly increased with adiponectin (100-2500μg/L) intervention(P <0.05).3.Compared with the control group, UCP-2, PPARγmRNA expression was significantly up-regulated in the high glucose treated group(P <0.05), but it was significantly down-regulated with adiponectin intervention(P <0.05).4. Compared with the control group,the number of apoptosis cells in the high glucose treated group were significantly increased than the control group(P<0.05), but it significantly decreased with adiponectin intervention(P <0.05).5. Compared with the control group, the protein expression level of cleaved Caspase 3 in the high glucose group was significantly up-regulated (P<0.05), but it was significantly down-regulated with adiponectin intervention(P <0.05).Conclusions:1. Adiponectin can restore the insulin secretion fuction of pancreaticβcells impaired by exposure to high glucose level,which may be related to the mechanism of reduced UCP-2mRNA expression regulated by adiponectin through PPARγpathway. 2. Adiponectin can counteract high glucose-induced apoptosis in the pancreaticβcells, which may be related to the mechanism by inhibiting the activation of Caspase 3.