The Study On The Adaptation Of Pancreatic Islets During Pregnancy In Rats

Objectives:1. To elucidate the adaptive changes of the pancreatic islets duringpregnancy in rats.2. To investigate the profiles of islet gene expressions at variousstages of pregnancy in rats, explore differential gene expressions duringpregnancy,and to analyze the characteristics of key genes relevant toislet regeneration.Methods:1. On the basis of oral glucose tolerance test (OGTT) and insulinreleasing test (IRT), serum insulin was detected by ELISA to investigatechanges of islet function during pregnancy in rats.2. Pancreatic islets of SD rats during pregnancy at day 10.5,12.5,14.5,18.5,20.5 and non-pregnant female rats were isolated and purified,respectively.3. On the basis of glucose-stimulated insulin secretion test (GSIS),supernatant insulin was measured by radioimmunoassay to investigatechanges in glucose stimulated insulin secretion in pregnant rats.4. Rat pancreatic tissues of each group were double-stained for5-bromodeoxyuridine (BrdU) and insulin using immunohistochemistry technique to study the changes of isletβ-cell proliferation duringpregnancy at day 10.5, 12.5, 14.5, 18.5 and 20.5.5. Genechips from Affymetrix company were applied to exploregene expression profiles. Data, especially genes related to isletregeneration, were then analyzed by bioinformatical methods.6. Expressions of genes were studied by RT-PCR and Real-time PCRto verify the results of genechips.Results:1. Compared with normal control group, the levels of fasting glucoseand fasting insulin were significantly decreased whereas glucosetolerance was not impaired during pregnancy in rats. Areas under theglucose tolerance curve were also decreased remarkably. Moreover,insulin secretion after the glucose load and areas under the insulinreleasing curve were increased from gestational day 14.5 to 20.5.2. Glucose-stimulated insulin secretion was enhanced from day 12.5to day 18.5 of gestation in rats.3. Compared with normal control group, the proliferation index(PI),the average photodensity of insulin-expression positive zone and insulinrelative concentration (IRC) of pancreatic islets were all significantlyincreased by day 12.5, rose continuously to a peak at day 14.5 ofpregnancy, and then gradually returned to control levels.Insulin-expression positive cell density (PCD) was also increased remarkably at gestational day 12.5 and 14.5. In addition, areas ofinsulin-expression positive cells were much greater during pregnancy atday 14.5 to day 20.5 than in non-pregnant rat.4. There were 31099 genes included in the Affymetrix Rat Genome230 2.0 Array. The detection rates in each group such as normal femalerats(N),pregnant rats at day 10.5(P10.5) and day 14.5(P14.5) were45.3％,38.2％and 37.2％, respectively. The differentially expressedgenes identified were distributed into 8 main categories:(1)genes involvedin apoptosis or tumor; (2)genes related to binding; (3)genes involved inmetabolism; (4)genes related to cell cycle; (5)genes for signal transduceractivity; (6)genes related to structural molecule activity; (7)genes involvedin transcription regulator activity; (8)genes for transporter activity.5. Some regulatory genes in pancreatic islets were analyzed andwere divided into several categories according to their biologicalfunctions: pancreatic hormone-related genes, insulin release-related genes,islet proliferation-related genes and so on. Among these genes,expressions of insulin 1 and insulin 2 genes were up-regulated duringpregnancy especially at day 14.5. Gene expressions of potassiuminwardly rectifying channel (Kir6.2), Rab3a, Glucokinase(Gck) weresignificantly decreased at gestational day 14.5 compared with normalcontrol, while B-cell translocation gene 2(BTG2) was increased duringpregnancy. In addition, regenerating islet-derived 3 alpha (Reg3a) was statistically up-regulated during pregnancy compared with normalcontrol.Conclusions:1. Both pancreatic islet function and proliferation are considerablyincreased in middle and late pregnancy.2. Compared with normal control group, expressions of hundreds ofgenes are changed during pregnancy. These differentially expressedgenes may play an important role in adaptation of pancreatic isletsduring pregnancy in rats.3,Gene expression of Reg3a is markedly increased duringpregnancy, suggesting that this gene may be related to isletregeneration.