Variable glycation of serum proteins in patients with diabetes mellitus

To determine whether there were variations in vivo and in vitro in the glycation process among patients with diabetes mellitus and to assess the characteristics of patients with high and low glycation, if this was observed.

Patients (n = 185) attending a Diabetes Day Care Centre or Notre-Dame Hospital in Montreal participated in the in vivo study. Patients found to have high and low glycation were asked to allow the use of their serum for the in vitro part of the study.

Capillary blood glucose levels were determined by nursing staff 4 times a day over 7.3 (standard deviation [SD]5.3) consecutive days with commercially available glucose oxydase reagent strips and meters. The ratio of the fructosamine concentration to the protein concentration (the F/P ratio) and the glycated hemoglobin were also determined at the same time as the capillary blood glucose level. Glycation was defined as the mean capillary blood glucose/F/P ratio. Patients with high and low glycation (higher or lower than [SD], of the mean) were compared. For the in vitro study, incorporation of carbon-14 glucose in serum proteins incubated with a 30-mmol/L glucose concentration was studied in some of the patients with low and high glycation.

The mean capillary blood glucose/F/P ratio was a mean of 2.30 (SD 0.29) g/mL. Of the 185 subjects 31 had high glycation (1.46 [SD 0.19] g/mL) and 27 had low glycation (2.97 [SD 0.035] g/mL, p < 0.001). There was no significant difference in age, sex, diabetic treatment and glycated hemoglobin levels between the 2 groups. However, patients with low glycation had a greater body mass index (29.4 [SD 5.7] kg/m2 v. 26.4 [SD 4.3] kg/m2, p < 0.05). In vitro, incorporation of 14C glucose in serum proteins incubated with a 30mmol/L glucose concentration was higher in the 9 patients with high glycation than in that of the 7 with low glycation (0.031% [SD 0.03%] per gram of proteins v. 0.028% [SD 0.03%] per gram of proteins, p < 0.02).

Glycation may vary among patients with diabetes mellitus who have similar capillary blood glucose concentrations. Glycation appears to be lower in patients with a greater body mass index. Furthermore, alternation in the glycation process itself may explain, in addition to the mean blood glucose level, the difference in fructosamine levels.