INSULIN SENSITIVITY, INSULIN-SECRETION, AND GLUCOSE EFFECTIVENESS IN SUBJECTS WITH IMPAIRED GLUCOSE-TOLERANCE - A MINIMAL MODEL ANALYSIS

The aim of the present study was to estimate insulin secretion, insulin sensitivity (SI), and glucose effectiveness (SG) in non-obese Japanese subjects with impaired glucose tolerance (IGT). Ten IGT subjects (five men, five women) and 15 normal-tolerance subjects (seven men, eight women) without a family history of diabetes were studied. They underwent a modified frequently sampled intravenous glucose tolerance test (FSIGT); glucose (300 mg/kg body weight) was administered, and insulin (20 mU/kg over 5 minutes) was infused from 20 to 25 minutes after the administration of glucose. SI and SG were estimated by Bergman's minimal model method. No significant difference was observed in body mass index ([BMI] 22.1 ± 0.8 v 21.1 ± 0.5 kg/m2), fasting plasma glucose (5.19 ± 0.18 v 5.07 ± 0.11 mmol/L), and insulin levels (50.7 ± 7.3 v 45.2 ± 4.5 pmol/L) of subjects with IGT and normal controls. The glucose disappearance rate (KG) was significantly lower in subjects with IGT than in normal-tolerance subjects (1.57 ± 0.20 v 2.09 ± 0.15%/min, P < .05). Pancreatic insulin secretion expressed as the integrated area of plasma insulin above the basal level during the first 20 minutes was lower in IGT subjects (2,556 ± 572 p pmol/L × min) than in normal-tolerance subjects (4,957 ± 800 pmol/L × min, P < .05). SI was not statistically different between the two groups (0.84 ± 0.13 × 10-4 v 1.14 ± 0.15 × 10-4 · min-1 · pmol/L-1). However, SG was significantly lower in subjects with IGT than in normal controls (0.013 ± 0.002 v 0.023 ± 0.002 min-1, P < .01). The basal insulin effect (BIE) of IGT subjects was not significantly different from that of normal subjects (0.004 ± 0.0004 v 0.005 ± 0.001 × min-1), whereas glucose effectiveness at zero insulin (GEZI) was significantly lower in IGT subjects than in normal subjects (0.010 ± 0.002 v 0.018 ± 0.002 min-1, P < .01). Thus, Japanese IGT subjects with normal SI are characterized by mild impairments in pancreatic insulin secretion and decreased SG and GEZI. © 1994.