The Qualitative Diagnosis Of Insulinoma And The Role Of IGF2 In Insulinoma Pathogenesis

Objective:Our aim was to evaluate the value of prolonged 5-hour oral glucose tolerance test(5-hour OGTT)in qualitative diagnosis of insulinoma,and to explore the simple and easy diagnostic indicators.IGF2 can promote tumor growth,not only promotes tumor cell division and differentiation,but also inhibits the apoptosis of tumor cells,and plays a vital role in the development of tumor.The hypermethylation in the IGF2 differentially methylation region(DMR)2 in insulinomas were correlated with the overexpression of IGF2.Therefore,in this study,we focused on the role of IGF2 in pathogenesis of insulinoma.Study object and method:Initially,15 patients with insulinoma and 12 subjects with reactive hypoglycemia were enrolled in the study.In addition,a further 75 subjects with symptoms of hypoglycemia as a chief complaint at their first clinic visit were subsequently screened.The expression and location of IGF2 were detected by RT-PCR,immunohistochemistry and immunofluorescence.Cell proliferation was detected by CCK8,EdU,Western blotting.Results:1.Insulin-to-glucose ratio at 5-hour post load combined with C-peptide-to-glucose ratio at 0 min turned out to be the best model.The AUC of 0.94 was highest of all models.The sensitivity,specificity,negative predictive value,positive predictive value,negative likelihood ratio,positive likelihood ratio of this model was 100.00%,83.30%,100.00%,88.20%,0.00,6.00 respectively,and we established that the cut-off of the insulin-to-glucose ratio at 5-hour post load was 20.45 pmol/mmol and C-peptide-to-glucose ratio at 0 min was 0.19 nmol/mmol.2.Higher specifcity(73.08% vs.55.77%)was reached in insulin-to-glucose ratio at 5-hour post load combined with C-peptide-to-glucose ratio at 0 min model when compared with insulin-to-glucose ratio at 5-hour post load combined with insulin-to-glucose ratio at 0 min model.However,the corresponding sensitivity negative predictive value,positive predictive value,negative likelihood ratio and positive likelihood ratio were 90.48%,57.58%,0.24,3.07 respectively.3.IGF2 expressions in human insulinoma were significantly increased when compared with para-insulinoma,and the Min6 and INS1 cells also expressed the IGF2.Insulin and IGF2 immunofluorescence showed that the normal islet structure had been disrupted,and the IGF2 is mainly located in the cytoplasm.4.Overexpression of IGF2 in Min6 and INS1 cells,the results of CCK8,EdU and PCNA suggested that IGF2 can promote cell proliferation.5.The Min6 and INS1 cells were treated with PA after the overexpression of IGF2,Western blotting results showed Bax expression levels were reduced compared with the control group,and increased expression of Bcl-2.In addition,the Bcl-2/Bax ratio was significantly increased(all P<0.05),suggesting that overexpression of IGF2 may be improved,to some extent,PA-induced apoptosis.Conclusion:1.Ratios of insulin and C-peptide release relative to blood glucose levels,measured during a 5-hour OGTT,may have important clinical value in the diagnosis of insulinoma.2.High expression of IGF2 may play an important role in in pathogenesis of insulinoma by promoting cell proliferation.