Evaluation of insulin release and relative peripheral resistance with use of the oral glucose tolerance test: a study in subjects with normoglycaemia, glucose intolerance and non-insulin-dependent diabetes mellitus.

With use of 75 g oral glucose tolerance tests (OGTTs), insulin release and relative peripheral resistance were evaluated in groups of normoglycaemic subjects, subjects with glucose intolerance (GI) and patients with non-insulin-dependent diabetes mellitus (NIDDM). Insulin release was expressed as the total area under the insulin curve (AUCI) and as the area under the insulin curve above the fasting insulin level (delta AUCI). The insulin response to glucose was expressed as the ratio of the area under the insulin curve to that of the glucose curve above fasting levels (delta AUCI/delta AUCG). The glucose uptake rate during the OGTT (M) was measured as the difference between the glucose load and the increase of the amount of glucose in the glucose space after, compared to before, the OGTT. The relative peripheral resistance against glucose uptake promoting factors (rel-R) was expressed as 1/M. With application of these indices in the non-obese groups, there was an increased mean total insulin release (AUCI, delta AUCI) while the mean insulin response to glucose (delta AUCI/delta AUCG) was decreased in GI-subjects compared with normoglycaemic subjects. The mean relative peripheral resistance (rel-R) was higher in GI-subjects than in normoglycaemics. Mean values of AUCI and delta AUCI were decreased (lower than in the normoglycaemics, NS), mean values of delta AUCI/delta AUCG were further decreased and mean values of rel-R were further increased in the NIDDM-groups compared with the GI-group. Insulin release was delayed in GI and NIDDM. Obese normal and obese GI-subjects with similar rel-R values as the corresponding non-obese normal and non-obese GI-subjects, had higher mean values of insulin release than the non-obese counterparts. Thus, it seemed possible to use a technique in general use, the OGTT, with a partly new approach to simultaneously obtain indices for insulin release and relative peripheral resistance, which may have clinical applicability.