The Changes Of Gnrh, Gnrhr, Bcl2 And Bax In Pancreas And The Function Of Islet β Cells In The Evolution Of Pancreatic Fibrosis Of Sd Rats

Pancreatic diabetes is one kind of secondary diabetes, whose endocrine insufficiency is secondary to pancreatic exocrine diseases. Chronic pancreatitis is a primary cause of pancreatic diabetes and its basic pathological character pancreatic fibrosis. Previous studies show that Bcl2 and Bax are involved in cell apoptosis in pancreas tissue of chronic pancreatitis and the decreas of Bcl2:Bax suggests cell apoptosis increase. Researches on gonadotropin-releasing hormone(GnRH) and gonadotropin-releasing hormone receptor(GnRHR) report that both have effects on cell proliferation directly in tumor tissues. At present, scholars consider GnRH and GnRHR of pancreas may have an effect on the function of isletβcell through paracrine and /or autocrine pathway however which specific signal is not clear.AimThe expressions of GnRH, GnRHR, Bcl2 and Bax in pancreas and the changes of isletβcells function in pancreatic fibrosis rat after intraperitoneally treated with diethyldithiocarbamate (DDC) repeatedly were studied. The relationships between the changes of GnRH and GnRHR and the changes of isletβcell function and Bcl2 and Bax in pancreas were observed.MethodsTwenty-five male SD (Sprague Dawley) rats were divided into five groups randomly and equally. Group A are normal controls and other groups were administrated with diethyldithiocarbamate(DDC). DDC were treated with 500mg/kg i.p., twice a week.The groups B-E were treated with DDC for one, two, three and six weeks respectively. Oral glucose tolerance tests were carried out and blood glucose and serum insulin were assayed. After finishing the OGTT, the rats were sacrificed in fasting respectively, one part of the pancreas was flxed in 4% formaldehyde solutions,embedded in paraffin and stained with hematoxylin-eosin (HE). And the remain pancreas was used to detect the expressions of GnRH,GnRHR,Bcl-2 and Bax mRNA levels in all groups with Real-time quantitative PCR(SYBR Green).Results1. Pathological changes Examined pancreatic specimens by optical microscope, the morphology of pancreatic acina cells and isletβcelsl are intact in A group, and there are several changes such as inflammatory cell infiltration, pancreatic acinar cell atrophy, vacuolar change,and lobular gap widened in B,C and D groups, and acinar cells appear cellulose-like arrangement in E group.2. The changes of isletβcell function In OGTT, there are no significant differences in blood glucose (P> 0.05)and there are significant differences in serum insulin(P <0.05) among all groups. Compared with A group, FINS/FBG and HOMA-IR (P <0.05) increases significantly in D group;FINS/FBG in C group and INS/PG(30min),△IRI/△BS(30min) and INS-AUC in C and E group decreased(P<0.05), HOMA-S% decreases in D group (P =0.05).3. The changes of GnRH ,GnRHR,Bcl2 and Bax mRNA level of pancreasANOVA analyze showed that there are significant differences in the expression of GnRH betwen all groups (P<0.05). Compared with E group, there are significant differences in B and D group respectively (P<0.05). The mRNA level of GnRH in E group is the highest. Compared with A group, the expressions of GnRHR decline in B and D groups, the expressions of Bcl2 increase in D and E groups, the expressions of Bax increase in B and E groups, the ratios of Bcl2 to Bax rise in the groups treated with medicine. Those four differences above are all significant and P values are all less than 0.05.4. Pearson correlation analysis results GnRH mRNA levels are negatively associated with fast blood glucose. (r= -0.443, P<0.05); GnRHR mRNA levels are associated with serum insulin at 15 min in OGTT positively (r=0.435, P<0.05) and with Bcl2: Bax negatively(r= -0.813, P<0.05); Serum insulin at 15 min in OGTT are associated with Bcl2:Bax positively (r=0.431, P<0.05),Consulsion1. Isletβcell function decline in the pancreatic fibrosis early.2. In the evolution of pancreatic fibrosis, the ratio of Bcl2 to Bax increase and show cell proliferation mainly in this stage.3. GnRHR are correlated with the increase of Bcl2:Bax negatively, which suggest GnRHR may be involved in cells apoptosis in the evolution of pancreatic fibrosis. And GnRHR are correlated with 15 min serum insulin in OGTT positively which suggest GnRHR maybe related to the decline of isletβcell function in the pancreatic fibrosis early.