Nonenzymatic glucosylation of serum proteins in diabetes mellitus.

The extent of nonenzymatic glucosylation of serum protein in control and diabetic subjects was measured by a chemical procedure using thiobarbituric acid. A mean value of 0.81 (+/- 0.21 SD) nmol glucose per milligram serum protein was observed in the control group. Diabetics displayed elevated levels of glucosylated serum proteins, up to 4 nmol glucose per milligram protein. Glucosylation of serum protein correlated strongly with fasting blood sugar (r = 0.71), percent hemoglobin A1 (r = 0.79), and percent glucosylated albumin (r = 0.99). There was no overlap between control and diabetic groups, i.e., within 3 SD of the mean of controls. These studies indicate that the assay for glucosylated serum protein appears to be an especially sensitive indicator of the degree of hyperglycemia in diabetes.