GLYCOXIDATION IN AORTIC COLLAGEN FROM STZ-INDUCED DIABETIC RATS AND ITS RELEVANCE TO VASCULAR DAMAGE

Glycoxidation reactions lead to the formation of permanent, irreversib le chemical modifications and cross-links in protein, such as the glyc oxidation products carboxymethyllysine (CML) and pentosidine. It has b een implicated that CML as well as Amadori products play a role in the formation of superoxidative products, such as H2O2, and advanced glyc osylation endproducts in trapping LDL. Therefore, a possible relations hip between glycoxidation and lipoperoxidation might exist because oxi dized lipoprotein, which has been directly linked to atheroma formatio n, could be produced by the superoxidative products released from the pathway of CML formation. Using a CML-specific monoclonal antibody (6D 12) and a specific antiserum against hexitol-lysine (HL), an Amadori p roduct, we studied the relationship between glycoxidation and lipopero xidation by determining the aortic CML contents with ELISA and the flu orescence levels of lipoperoxidation side products, malondialdehyde (M DA) and hydroxynonenal (HNE) from STZ-induced diabetic rats and age-ma tched control rats. The immunohistochemical and ultrastructural change s relevant to glycoxidation and lipoperoxidation were also studied. Th e CML content measured by ELISA in DM rats was significantly higher th an that in the control rats at 28 weeks (n = 11, P < 0.01). The levels of MDA-linked and HNE-linked fluorescence in the DM rats increased in a similar way and were significantly higher than the levels in contro l rats at 28 weeks (n = II, both P < 0.01 at 28 weeks). The CML conten ts correlated with the fluorescence levels of both MDA-linked (n = 19, r = 0.638, P < 0.01) and HNE-linked fluorescence (n = 19, r = 0.629, P < 0.01) only in the DM rats, but not in the control rats. Our immuno histochemical study thus demonstrated that CML was initially formed in the aortic media of diabetic rats in the 16th week of diabetes, local ized primarily in the extracellular matrix surrounding the aortic smoo th muscle cells after HL occurred early in the 2nd week of diabetes. C onsequently, a significant increase in the extracellular matrix and de crease in the area of the SMCs were observed in the aortic media in th e DM rats by a morphometrical study. The in vivo results of this study provided the first evidence that CML correlated with fluorescence lev els of MDA and HNE, and thus suggested the existence of a close relati onship between glycoxidation and lipoperoxidation in vivo. This inform ation is thus considered to shed some new light on the etiology of ath erogenesis in diabetes. (C) 1998 Elsevier Science Ireland Ltd.