Elevated plasma semicarbazide-sensitive amine oxidase (SSAO) activity in Type 2 diabetes mellitus complicated by retinopathy

Aims To measure plasma semicarbazide-sensitive amine oxidase (SSAO) activit ies and detect retinopathy in Type 2 diabetes mellitus (DM). Methods Cross-sectional, population-based. study of 65 diabetes patients (6 1 diagnosed from the age of 30 years) with or without retinopathy as determ ined by fundus photography in primary care. HbA(1c) was analysed by ion exc hange chromatography on a Mono S for HbA(1c) column. SSAO activities were a ssayed radiometrically and formaldehyde-albumin adducts by ELISA in plasma samples from patients and 136 healthy controls. Results Subjects with diabetes had higher plasma SSAO activity, measured as nmol benzylamine.ml plasma(-1).h(-1) (mean 20.6), than controls (mean 14.3 ), P<0.0001; 95%;, confidence interval (CI) for difference 4.9-7.7. SSAO ac tivity was higher in patients with retinopathy (mean 23.2) than in those wi thout (mean 18.9), P=0.012; 95% CI for difference 1.0-7.5, and related to t he HbA(1c) value, No statistically significant relationship between diabete s duration and SSAO activity was found. With HbA(1c) values and insulin tre atment entered into a multiple logistic regression model, SSAO activity no longer predicted retinopathy, P increasing from 0.025 to 0.17. SSAO activit y and the presence of any retinopathy were unrelated to titres of antibodie s against formaldehyde-treated human serum albumin. Conclusions SSAO activity, earlier found to be elevated in Type 1 DM, is al so elevated in Type 2 DM. The SSAO family of enzymes may be involved in the development of diabetic retinopathy, possibly by catalysing the formation of toxic metabolites. A potent and specific inhibitor of human SSAO might h elp prevent retinopathy in Type 1 and Type 2 DM.