1985 Volume 52 Issue 6 Pages 683-699
In an attempt to define clinically the heterogeneity of age-related glucose intolerance, the plasma insulin responses to glucose load were studied mainly in relation to the atherosclerosis.
Both oral (OGTT) and continuous intravenous (C-IVGTT) glucose tolerance tests were performed in 87 non-obese subjects whose ages ranged from 23 to 83 years. For the C-IVGTT a 10% glucose solution was administered at a constant rate of 8.7 ml/min via an antecubital vein for 20 min. The insulin responses to glucose during both tests were calculated as SIRI/SBs ratios (the area under the plasma insulin curve/the area under the plasma glucose curve). The results obtained were as follows :
1) The mean SIRI/Sss values during both the OGTT and the C-IVGTT in elderly (60 years and over) borderline diabetics were not significantly different from those for elderly normal subjects, and were significantly higher than those for adult (59 years and under) borderline diabetics.
2) The insulin response curve during the C-IVGTT resulted in a uniphasic pattern in normal subjects and borderline diabetics, and was flat in diabetics.
3) There were significantly positive correlations between the SIRI/SBs values of the OGTT and the C-IVGTT in both adult and elderly subjects.
4) In elderly subjects, the mean SIRI/Sss values of both the OGTT and the C-IVGTT for borderline diabetics with atherosclerosis were not significantly different from those for normal subjects with atherosclerosis, and were significantly higher than those for borderline diabetics without atherosclerosis. On the other hand, they were significantly lower for borderline diabetics without 'atherosclerosis than for normal subjects without atherosclerosis.
5) In order to confirm the effect of atherosclerosis on insulin response, an additional OGTT was performed in 34 non-obese elderly subjects whose HbA1 values were 7.0 to 7.9%. The mean STRI/Sss values were significantly higher for those subjects with atherosclerosis than for those without.
These findings suggest that there is a subgroup, which has clinically evident atherosclerosis without low insulin response to glucose load, in elderly subjects with mild impaired glucose tolerance. The subgroup may have decreased insulin sensitivity to peripheral tissues.
