Isoamylases in diabetes mellitus

Summary We have evaluated the relationship between diabetes mellitus and exocrine pancreatic insufficiency in diabetic subjects by measuring a specific isoamylase arising from the pancreas. The pancreatic- and salivary-type isoamylase activity in serum and urine were evaluated and related to duration of disease, sex, age, weight, blood glucose level and glycosuria in 153 diabetics. In the insulin-dependent diabetics diagnosed between 15 and 24 years of age, a significant decrease in pancreatic isoamylase activity was found in serum and urine (means with 2 SD range, 50 U/l, 19–137 U/l, and 47 U/l, 4–607 U/l, respectively), as compared with control subjects (79 U/l, 45–140 U/l, and 183 U/l, 43–789 U/l, respectively). In this group of patients a low stimulated output of amylase into the duodenum was also observed (mean with range, 537 U, 87–1808 U), compared with controls (the lower limit of normal 2183 U). A significant positive correlation was found between stimulated output of amylase into the duodenum and pancreatic isoamylase activity in serum (r = 0.84, p < 0.01). In the non-insulin dependent diabetics, a significant negative correlation was found between blood glucose levels and pancreatic isoamylase activity in serum (r = -0.46, p < 0.01). In the diet-treated non-insulin dependent diabetics the pancreatic isoamylase activity in serum was increased compared with controls (mean and 2 SD range, 102 U/l, 49–211 U/l). In patients with blood glucose level above 12 mmol/l, however, a lowered pancreatic isoamylase activity in serum, and no apparent rise in serum immunoreactive insulin in glucose loading test was observed. The results suggest that production of pancreatic amylase is related to endocrine pancreatic function in diabetes mellitus.