Investigation of Insulin Sensitivity in Children of Different Ages by Glucose, Insulin, and Somatostatin Infusion

Abstract

We evaluated age-related insulin resistance in obese and non-obese children of different ages using the insulin sensitivity test to determine the glucose clearance (GC) calculated for the steady-state plasma glucose level (SSPG). Concomitant infusion of glucose, insulin and somatostatin should virtually eliminate endogenous glucose formation. At steady-state, glucose utilization should be equal to the infusion rate. The higher the SSPG is, the lower the insulin sensitivity is. GC calculated for SSPG reflects the insulin resistance. Thirty-one boys (7-17 years) and 29 girls (5-18 years) were recruited for the study. The subjects of each sex were divided into three groups, according to the level of percentage of body fat (%fat) (boys; <30%, 30%~40%, >40%, girls; <20%, 20%~30%, >30%). Body composition was determined using bio-electrical impedance analysis (BIA). We investigated the correlation between glucose clearance (GC) and age. In girls, an inverse correlation was found between GC and age for the group with %fat<20% (y=-9.95x + 190.7, P=0.0073, r=0.728), but no correlation were found in the other groups. Also, no correlation was found in any group of boys. However GC tended to decrease as %fat increased irrespective of the age. Both an increase of %fat and age were important factors related to the decrease of insulin sensitivity in children. We consider that evaluation of body composition, nutrition, and lifestyle in children are important for the prevention of diseases such as syndrome X (comprising hyperinsulinemia, hypertension, and type 2 diabetes) and the deadly quartet (type 2 diabetes, obesity, hypertension, dyslipidemia, and atherosclerosis) caused by insulin resistance.