Glucose dependent insulinotropic polypeptide in impaired glucose tolerance and its association with insulin secretion and sensitivity
Background and aims: The abnormalities of incretin effects have been established as major determinants of insulin secretion and sensitivity which starts early in prediabetes. However, the pathophysiology of these states with incretin in Bangladeshi population has only been started to be investigated. The present study was undertaken to explore the association of glucose dependent insulinotropic polypeptide (GIP) with glycemic and insulinemic status in impaired glucose tolerance (IGT). Material and Methods: The analytic observational study was conducted under a case-control design with age and body mass index (BMI) matched 51 IGT and 47 control subjects. Serum C-peptide and GIP were measured by enzyme linked immunosorbent assay (ELISA). Insulin secretory capacity (HOMA-%B) and insulin sensitivity (HOMA-%S) were calculated by homeostasis model assessment. Results: IGT subjects showed significantly higher serum fasting GIP (FGIP) level compared to controls [pgm/ml, 74.21(10-190) vs. 49.62(6.1-278), (p = 0.001)]. There was no significant difference of postprandial GIP (PGIP) in the study subjects, however, the ratio analysis revealed reduced secretion of PGIP to FGIP (p < 0.001), and fasting C-peptide (FC-peptide) to FGIP (p < 0.05) respectively in IGT. In addition, serum PGIP and postprandial glucose (PSG) ratio was also significantly reduced in IGT compared to controls [7.0 (2.87-18.42) vs. 10.08 (1.88-23.25), (p < 0.01)]. In multiple regression, a significant positive association between FC-peptide and FGIP (p < 0.01) and negative association between FGIP and HOMA-%S (p = 0.05) were demonstrated. Conclusion: The incretin effect of GIP is diminished in IGT and it is associated with insulin resistance in Bangladeshi type 2 diabetic population.