A Study On The Relationship Between Islet Autoantibodies And β Cell Function

Objective By measuring islet autoantibodies, insulin in the fasting and 2h blood samples during oral 75g glucose tolerance test (OGTT),calculating insulin secretion index(HOMA-IS)and insulin resistance index (HOMA-IR),to analyze islet autoantibodies in relation to β cell function and investigate the diagnostic value of glutamic acid decarboxylase antibody(GADA) and islet cell antibody (ICA) determination in latent autoimmune diabetes in adults (LADA) which is similar to type 2 diabetes in order to guide type diagnosis and treatment.Methods 70 patients with newly diagnosed type 2 diabetes(2DM) and 70 subjects with normal glucose tolerance (NGT) were included.. ICA/GADA were determinded by ELISA and insulin by RIA.HOMA-IS, HOMA-IR ,the positive rates of ICA and GADA were calculated.HOMA-IS=20×FINS/(FBG-3.5).HOMA-IR=(FINS×FBG)/22.5.The clinical characteristics such as age,body mass index(BMI),waist-to-hip ratio (WHR),HbA1C,FINS, INS2h,HOMA-IS and HOMA-IR were investigated between subjects with NGT and patients with 2DM ,the same as between the group with positive antibodies and the group with negative antibodies.Results The positive rate of ICA in 2DM (11.4%,8/70) was significantly higher than that of normal control group(0%,0/70)(P<0.01).The same result in GADA (18.6% versus 4.3%,P<0.01). There were significantly difference between subjects with NGT and patients with 2DM in HbA1C ,fasting insulin,HOMA-IS and HOMA-IR(P<0.001).Fasting and postprandial 2h insulin of antibody positive group were significantly lower than those of antibody negative group.HOMA-IS and HOMA-IR were successively reduced in antibody negative group,single positive group and double positive group(P<0.001).Conclusion Some patients initially diagnosed as type 2DM may actually be LADA.The islet function of diabetics with positive antibodies was significantly lower than that of diabetics with negative antibodies,indicating that in the former islet function was markedly damaged,in the later insulin resistance was of importance.Those results suggest that islet antibodies combined with islet β cell function is of practical value in identifying LADA at the earliest stage of disease.Patients with LADA should avoid taking sulphonylurea and take insulin as early as possible in order to prevent from further destroy of residue islet β cells and reduce diabetic complications.