Determination of glycated plasma proteins in normal and diabetic subjects utilizing aminophenylboronic acid columns

The characteristcs and clinical utility of a commercially prepared method for measuring glycated plasma proteins (glyc PP) by aminophenylboronic acid affinity chromatography is described. The measured glyc PPs after loading columns with 0.05 ml (5.9%) or 0.025 ml (6.1%) plasma were greater than the glyc PP values when using 0.20 ml (4.5%) or 0.10 ml (5.0%). The glyc PPs in otherwise identical plasma containing 0, 1 gm/l, 2 gm/l and 4 gm/l glucose were not significantly different. Elimination of the aldimine component by dialyzing plasma against saline did not alter the amount of glyc PP. In vitro glycosylation of plasma proteins was dependent on glucose concentration and length of incubation. Maximum in vitro glycosylation (19.5%) occurred at 14 days of incubation with 5.7 gm/l glucose. The mean glyc PP (8.2%) of 24 diabetic subjects was greater than the mean glyc PP (2.7%) of 15 normal controls. Glyc PP and HbA₁ values positively correlated (n = 39 r = 0.89 p<0.01). After 2 weeks of improved glycemic control, the glyc PPs from 5 patients diminished from 6.8% to 3.3% (p<0.01). In conclusion, we characterize an aminophenylboronic acid affinity chromatographic method of assaying glyc PP which is simple, reproducible, requires a maximal protein load of 0.05 mg, is uneffected by ambient glucose, and measures the ketoamine composent of glyc PP. This is an ideal method to evaluate 2 week alterations of glycemic control of diabetic patients.