Background and aim: Metabolic characteristics and rate of progression to overt Type 2 diabetes (T2D) in low-risk European obese children are not well documented. Aim of the study was to investigate differences in insulin sensitivity and secretion in Italian obese children and youngsters with pre-diabetes.
Methods: Ninety-six obese children and youngsters with pre-diabetes, pair-matched with individuals with normal glucose tolerance (NGT) were included in the present study. Participants were screened by oral glucose tolerance. Pre-diabetes was classified as impaired fasting glucose (IFG), impaired glucose tolerance (IGT) and combined IFG-IGT. Homeostasis model assessment of insulin resistance (HOMA-IR), 2-h insulin, insulin sensitivity index (ISI) and disposition index (DI) were calculated to estimate fasting, peripheral and whole body insulin sensitivity and capacity of pancreatic islets to compensate for lower insulin sensitivity, respectively. One-way analysis of variance was used to compare groups.
Results: Eleven subjects had IFG (11.5%), 79 IGT (82.3%), 6 combined IFG-IGT (6.3%). Individuals with IFG showed the highest HOMA-IR (p=0.0007), those with IGT the highest 2-h insulin (p<0.0001), those with IFG-IGT the lowest ISI (p<0.0001), with severely reduced DI (p=0.0003). Compared with NGT, DI was 60% lower in those with IFG-IGT.
Conclusion: IFG is linked primarily to fasting insulin resistance, IGT to peripheral insulin resistance. IFG-IGT is hallmarked by reduced whole body insulin sensitivity and an additional severe defect in DI. Further longitudinal studies are needed to understand whether the different categories of pre-diabetes in European obese adolescents represent real pre-diabetic alterations.