Levels of DNA damage in groups of 10 patients with insulin-dependent d
iabetes mellitus and 10 matched controls were compared using the comet
assay; DNA strand breaks, oxidized pyrimidines (endonuclease m-sensit
ive sites) and altered purines (sites sensitive to formamidopyrimidine
glycosylase) were measured. Mean values of strand breaks and oxidized
pyrimidines were significantly higher in diabetics. Strand breaks cor
related with body mass index in the diabetic group. A strong correlati
on was seen between formamidopyrimidine glycosylase-sensitive sites an
d serum glucose concentrations. When three patients with normal glucos
e levels were excluded from the statistical analysis, the mean value o
f formamidopyrimidine glycosylase-sensitive sites was very significant
ly elevated compared with normal. DNA damage ill lymphocytes is thus a
useful marker of oxidative stress, and in particular formamidopyrimid
ine glycosylase-sensitive sites seem to represent changes specifically
related to hyperglycemia. (C) 1998 Elsevier Science Inc.