Changes Of Insulin Resistance And Islet β Cell Function In Subjects With Impaired Glucose Tolerance

Objective To investigate the changes of insulin resistance and islet B-cell function in subjects with impaired glucose tolerance(IGT) in order to explore the pathogenic mechanisms of IGT. Methods Oral glucose tolerance test(OGTT) and insulin release test were carried out in 101 subjects with normal glucose tolerance(NGT) , 96 subjects with IGT and 97 patients with newly diagnosed type 2 diabetes(T2DM), among them 23 subjects with NGT, 41 subjects with IGT and 30 subjects with T2DM were selected to carry out c-peptide release test and proinsulin release test, then Homa insulin resistance index(Homa-IR), insulin action index(IAI), Homa B cell function index(HBCI), I30/ G30, insulin area under curve(INSAUC) c-peptide area under curve(CPAuc) proinsulin area under curve(PIAuc), and PI/CP were calculated. Some comparisons and correlations were done among the three groups and between obese and non-obese subgroups in each group. Results (1) Adjusted with age, sex and body mass index(BMI), Homa-IR, PIAUC, and PI/CP were increased, while IAI, HBCI and I30/G30 were decreased gradually from NGT, IGT to T2DM. (P<0.05). INSAuc and CPAuc in IGT group were the highest among three groups (P<0.05). (2) In comparison with non-obese subgroups, Homa-IR, HBCI, INSauc, CPauc and PIauc were increased in obese subgroups; In comparison with obese subgroups, IAI was increased in non-obese subgroups. (3) Correlation analysises showed that Homa-IR was correlated with SBP, DBP, BMI, FINS, 2h INS, INSauc and PIAUC ( r =0. 191, 0. 161, 0. 199, 0. 870, 0. 344, 0. 357, 0. 471); HBCI was correlated with FBG , OGTT 2h plasma glucose, I30/ G30, fasting PI/CP and 2h PI/CPC r = -0. 587, -0. 447, 0. 327, 0. 226, 0. 244); I30/ G30 was positively correlated with OGTT 2h plasma glucose ( r = -0. 453, P<0. 01). (4) Multiple logisticregression analysis demonstrated that SBP, DBP, BMI, Homa-IR, IAI, INSAuc, CPAuc, PIauc HBCI, I30/ G30 and PI/CP are factors for the development of IGT, especially Homa-IR, I30/ G30 and HBCI. Conclusion There exist insulin resistance and impaired B cell function in the stage of IGT, decreased I30/G30 may be one of index of impaired early insulin secretion increased PI may be one of indications of B cell dysfunction, PI/CP is a better index of the assessment of B cell function.