Evidence for an increased glycation of IgG in diabetic patients.

The levels of non-enzymatically glycated total plasma proteins, albumin and IgG were determined in diabetic and non-diabetic patients using affinity chromatography on boronate-agarose gels. A significant increase in both glycated albumin and IgG, and in total glycated plasma proteins was demonstrated. A good correlation between glycated albumin and glycated hemoglobin was observed, while the correlation between glycated IgG and glycated albumin (or hemoglobin) was lower. This was found probably related to wide variations of glycated IgG for diabetics patients who have high glycated hemoglobin levels. These variations were inversely correlated with total serum IgG. Determination of fructosamine or 5-hydroxymethylfurfural content of IgG showed a significant increase in diabetics. Glycated IgG was found to contain approximately one mole of glucose. The main site of glycation was determined to be present in the Fab (more precisely the Fd) part of the IgG molecule.