Immunological evidence for increased oxidative stress in diabetic rats

The role of oxidative stress in aging and diabetes mellitus is currently under discussion. We previously showed age-dependent accumulations of fluorescent protein adducts with lipoperoxidative aldehydes, (malondialdehyde (MDA), and hydroxynonenal (HNE)) in rat skin collagen with diabetic BB rats exhibiting faster accumulation. Modified proteins have been shown to be immunogenic: antibody titres against rat serum albumin modified by MDA and HNE (MDA-RSA and HNE-RSA) or oxidized by reactive oxygen species were measured by ELISA as markers of oxidative damage in BB diabetic and non- diabetic rats. Each tested antibody titre was significantly higher in the diabetic than in the non-diabetic rats. A significant correlation existed between anti-MDA-RSA and anti-HNE-RSA antibody titers. Only the anti-HNE-RSA antibody titre increased significantly with age (p = 0.052) in diabetic animals, while no titres increased significantly in non-diabetic animals. A major factor which correlated with the development of these antibodies was diabetes duration: this was significant (p = 0.032) for anti-HNE-RSA antibody titre and slightly significant (p = 0.05) for anti-MDA-RSA antibody titre. Thus, chronic hyperglycaemia is probably fundamental in the increase of oxidative stress. There is correlation between anti-aldehyde-RSA antibody titres and the corresponding aldehyde-related collagen-linked fluorescence: modified collagen may play a part in the observed immune response. Our data indicate a stronger immune response of diabetic rats against proteins modified by lipoperoxidative aldehydes and oxygen free radicals, and they support the hypothesis of increased oxidative damage in diabetes.