Levels of peripheral blood cell DNA damage in insulin dependent diabetes mellitus human subjects

Abstract

Increased production of reactive oxygen species (ROS) in vivo can lead to cellular biomolecule damage. Such damage has been suggested to contribute to the pathogenesis of insulin dependent diabetes mellitus (IDDM). In this study, we used the alkaline comet assay to measure DNA damage (single-stranded DNA breaks and alkali-labile sites) in freshly isolated whole blood, lymphocytes, monocytes, and neutrophils from 23 subjects with IDDM and 32 age- and sex-matched controls. Analysis of the results showed elevated levels of DNA damage (expressed as % comet tail DNA) in the lymphocyte (4.10±0.47, 3.22±0.22), monocyte (4.28±0.47, 3.49±0.18), and whole blood (4.93±0.51, 4.51±0.23) fractions from IDDM subjects compared to controls, respectively, but the increases observed were not statistically significant. However, we found significantly elevated basal levels of DNA damage in the neutrophil fraction (8.38±0.64, 4.07±0.23; p<0.001, Mann–Whitney U test) in IDDM subjects compared to controls. Given these novel neutrophil findings, we extended the study to include a total of 50 IDDM subjects and 50 age- and sex-matched control subjects and determined basal levels of DNA damage in the neutrophils of all 100 subjects. We found significantly elevated mean levels of DNA damage (8.40±0.83, 4.34±0.27; p<0.001, Mann–Whitney U test) in the neutrophils from the IDDM subjects when compared to controls. Our results show that even with acceptable glycaemic control there is a significantly elevated level of DNA damage within diabetic neutrophils in vivo.