Reduced glucose effectiveness as a feature of glucose intolerance: Evidence in elderly Type-2 diabetic subjects

One of the factors determining glucose tolerance is glucose disappearance independent from the dynamic insulin (glucose effectiveness); the debate on its role in the development of Type-2 diabetes is still open. The aim of the present study was to evaluate insulin delivery, insulin sensitivity (S(1)), and glucose effectiveness S(G) in a group of elderly Type-2 diabetic patients (D, 4/6 F/M, age 67+/-2 years, 64+/-2 kg, BMI 23.8+/-0.5 kg/m(2)), compared to young controls (C, 4/6 F/M, 25+/-2 years, 72+/-4 kg, 23.7+1.1 kg/m(2)) and elderly controls (E, 2/4 F/M, 73+/-3 years, 63+/-4 kg, 23.1+/-0.5 kg/m(2)). We performed oval (OGTT) and intravenous (FSIGT) glucose tolerance tests. The OGTT showed that C and E were normotolerant, while D had a markedly reduced glucose tolerance. This teas also confirmed in the FSIGT where the glucose tolerance index K(G) was 0.6+/-0.1% min(-1) in D us 1.8+/-0.2 in C and 1.5+/-0.2 in E (p<0.0002). Total insulin area of D and the overall insulin delivery were not different from those of the control groups. The early phase area was instead significantly reduced (0.19+/-0.02 mU min/mL vs 0.61+/-0.06 of C and 0.46+/-0.06 of E, p<0.001) given the reduction in the dynamic first-phase insulin delivery (0.86+/-0.17 min(mu U/mL)/(mg/dL) us 3.95+/-0.61 in C (p<0.005) and 2.61+/-0.66 (p<0.001) in E). Si of D was 3.4+/-0.4 10(-4)min(-1)/(mu U/mL), not different from that of C (4.7+/-0.6) and E (3.5+/-0.2). This study showed a marked difference between SG of D and that of both control groups [0.010+/-0.001 min(-1) vs 0.026+/-0.004 (p<0.001) of C and 0.020+/-0.003 (p<0.002) of E] mostly due to the zero-insulin component GEZI which was 0.006+/-0.001 in D vs 0.021+/-0.004 in C and 0.016+/-0.003 in E (p<0.003). In the elderly groups, when taken together, SG exhibited a positive correlation with the area under insulin concentration during the early phase and with KG (r=0.6, p=0.0032 and r=0.90, p=0.0001, respectively), demonstrating the importance of the first-phase insulin delivery in modulating glucose effectiveness and glucose tolerance. (C) 1999, Editrice Kurtis.