Three principal findings have resulted from this study: (1.) The plasma insulin response to glucose loading is lower in prediabetics than in normal individuals. This phenomenon, while apparent when the glucose and insulin curves are expressed as a function of time, can be better demonstrated and quantitated by expressing plasma insulin concentration as a function of glucose concentration during the early portion of the glucose tolerance curve. The findings in this report suggest the sensitivity of the pancreatic β cells of prediabetics to glucose stimulation is lower than that of normal persons.
(2.) A low plasma insulin response to glucose loading is also seen in nonobese diabetic subjects. However, since these patients had elevated plasma glucose concentrations with insulin levels like those of the prediabetics, one must suspect that insulin in this group was less effective than in prediabetics in exerting its influence on blood glucose. Whether this is due to antagonists to insulin action or to physiologic defects in the immunoreactive insulin molecule has not been determined in this study.
(3.) The same method of relating plasma insulin to glucose concentration was used in assessing the insulin secretion in an obese diabetic population. Diabetics with fasting glucose values in excess of 150 mg. per 100 ml. reveal a decreased insulin response to glucose stimulation. These findings suggest a decreased sensitivity of the β cells to glucose stimulation in this group.