Malondialdehyde modified proteins and their antibodies in the plasma of control and streptozotocin induced diabetic rats.

One of the possible mechanisms of diabetes-related tissue damage is modification of various proteins via lipid peroxidation byproducts such as malondialdehyde (MDA). To determine the extent of MDA derivatization of plasma proteins, Western blots were carried out using anti-MDA antisera to study plasma proteins in control and streptozotocin (STZ)-induced diabetic rats. Since MDA can modify proteins and may alter or enhance their antigenicity, we screened plasma samples for anti-MDA antibodies using enzyme-linked immunosorbent assay (ELISA), and confirmed antibody specificity by inhibition ELISA. Circulating immune complexes containing MDA were also assayed. This study is the first demonstration of the existence in plasma of MDA-modified proteins with a molecular weight of approximately 100 Kd. Both control and diabetic rats have similar concentrations of plasma anti-MDA antibodies and circulating immune complexes. These results do not support the notion that diabetes alters the immune response to MDA modified proteins. Whether MDA modification of proteins participate in immunological processes that lead to tissue injury remains to be demonstrated.