EFFECT OF AGE ON PLASMA PROINSULIN-LIKE MATERIAL AFTER ORAL GLUCOSE

Abstract

The total plasma insulin and proinsulin-like material after oral glucose was studied in 68 lean subjects of varying ages with normal glucose tolerance tests. Although each subject had a normal test, the mean glucose levels increased with increasing age. When younger subjects (ages 15-44) were compared with older (45-74), no significant differences in total insulin responses were seen, but plasma proinsulin-like material was significantly higher in the older age subjects. All values after stimulation were significantly greater in subjects 45-74 yr of age than in those 15-44 yr of age (P < 0.01). A significant correlation between the amount of proinsulin and the age of the subject was seen. These findings may reflect a decreased conversion of proinsulin to insulin in the aging pancreas or could relect decreased clearance of proinsulin in older subjects.