Abstract
There is controversy over the existance of a deficiency of early insulin release in prediabetes and diabetes mellitus. One reason for this controversy may be the lack of examination of the stimulus-response relationship in glucose-stimulated insulin release. Our study was designed to examine the relationship between glucose dose, arterial plasma glucose changes and subsequent early phase insulin release.
Five normal male subjects were given 5 increasing doses of glucose, from 0.25 gm to 5 gm per square metre body surface area intravenously over 20 second time periods. Frequent arterial and venous blood samples were obtained and assayed for glucose and insulin. Both maximal rise in insulin and increase in area under the insulin curve were used as indices of insulin secretion.
It was found that the venous plasma glucose level was an inaccurate measure of the glucose stimulus to the beta cell. Early insulin release in normal subjects, in response to the administered intravenous glucose loads, was found to be related to the change in arterial plasma glucose concentration. Both early insulin release and changes in arterial glucose were found to be related to the administered glucose dose. The relationships between early insulin release and either (I) change in arterial plasma glucose or (II) glucose dose were found to have little variation between normal subjects and we hypothesise that these relationships are measures of total pancreatic beta cell secretory function in man. We propose the term "Early Insulin Index" for the gradient of the early insulin-glucose dose relationship: a measure which has simplicity of derivation and potential diagnostic use in prediabetic states.
Key words
Glucose - Insulin - Beta Cell - Prediabetes - Diabetes
1 This work was supported in part by a grant from the National Health and Medical Research Council.
2 Research Fellow, National Health and Medical Research Council Postgraduate Scholar.
3 Director
