Fluorescence-determined kinetics of plasma high oxidability in diabetic patients.

The peroxidative potential of whole plasma was studied in thirteen control subjects and twenty-three diabetic patients divided into two groups on the basis of their metabolic control, defined as good (n = 12) or poor (n = 11) according to the fasting blood glucose, glycated hemoglobin and fructosamine levels. The amounts of thiobarbituric reactive substances (TBARS) were determined before and after an exhaustive peroxidation induced by incubation with cupric sulfate; the kinetics of Cu-dependent plasma peroxidation, determined by the time course of endogenous fluorescence emission at 430 nm, were also evaluated. Our data indicate that in diabetic patients, and particularly in those with a long-lasting poor metabolic control, a significant increase in plasma susceptibility to peroxidative stress is evident only when we consider the lag-time of fluorescence emission in the course of Cu-induced plasma peroxidation. A good inverse correlation was observed between the lag-time and the blood glucose concentration, the glycated hemoglobin and the fructosamine blood levels. Furthermore a multivariate analysis, performed by Principal Component Analysis, strongly supports the relation between the extent and duration of the diabetic pathology, and the decrease in the lag-time of oxidation.