Insulin function in obese children within the low and high ranges of impaired fasting glycemia

Background/Objective Impaired fasting glycemia (IFG) reflects an intermediate hyperglycemia in the fasting state. Which fasting glucose level that actually is associated with impaired insulin-glucose homeostasis in children and adolescents with obesity is unknown. The aim of this study was to investigate how insulin and glucose homeostasis in children and adolescents with obesity in Sweden varies within different fasting glucose levels in the non-diabetic range. Subjects The subjects, n = 333, were divided into three groups based on their fasting glucose level. Normoglycemic range: up to 5.5 mmol/L (n = 268); the exclusive range the American Diabetes Association (ADA) has for IFG diagnosis: 5.6-6.0 mmol/L (n = 44); and IFG according to World Health Organization: 6.1-6.9 mmol/L (n = 21). The three groups were of similar age, degree of obesity, fasting insulin levels, sex, and migrant background distribution. Methods We used an insulin-modified frequent sample intravenous glucose tolerance test to study acute insulin response (AIR), insulin sensitivity (SI), and disposition index (DI) in children and adolescents with obesity. The main outcome measures were AIR, SI, and DI in three groups based on fasting glucose level. Results Fasting glucose levels ranging from 5.6 to 6.0 mmol/L were not associated with a lower AIR, SI, or DI compared with the normoglycemic range. However, glucose levels ranging from 6.1 to 6.9 mmol/L were associated with lower AIR and lower DI, but no statistical differences in SI were present. Conclusions IFG in the exclusive ADA range was not associated with disturbed glucose metabolism. This suggests that IFG contributes to adverse metabolic profile in children differently to what has been described previously in adult obese populations.