Alteration of serum semicarbazide-sensitive amine oxidase activity in chronic renal failure.

Despite recent intensive investigations, physiological and pathological role of semicarbazide-sensitive amine oxidase (SSAO) is far from clear. In this study, serum SSAO activity was determined, radiochemically, in various groups of uremic patients: haemodialysed (HD), peritoneally dialysed (PD) and those receiving conservative treatment but still not dialysed (ND), as well as in controls. Reduced enzyme activity was found in HD uremic patients before and after dialysis treatment, compared to controls (5260 +/- 862 and 6011 +/- 958 pmol/h/ml vs. 8601 +/- 283 pmol/h/ml, p < 0.01 and p < 0.05, respectively). The activity was slightly lower in PD, and normal in ND patients. In HD patients SSAO activity was also determined by an assay based on the formation of hydrogen peroxide, and was found to be elevated compared to controls (2384 +/- 323 pmol/h/ml vs. 1437 +/- 72 pmol/h/ml, p < 0.05). The elevated serum SSAO activity measured through the detection of the enzyme-generated hydrogen peroxide in HD patients might indicate its contribution to the accelerated atherosclerotic disease observed in uremia.

Studies on the insulinomimetic effects of benzylamine, exogenous substrate of semicarbazide-sensitive amine oxidase enzyme in streptozotocin induced diabetic rats.

Semicarbazide-sensitive amine oxidase/vascular adhesion protein-1 (SSAO) is believed to be a bifunctional membrane protein. It is localized extracellularly and preferentially oxidizes short chain primary amines to aldehydes, hydrogen peroxide and ammonia, but also functions as an adhesion molecule, which is involved in leukocyte migration. Serum SSAO activity is increased in diabetic patients and animals and the aldehydes formed in the enzyme reaction may contribute to vascular damage. However, administration of exogenous substrates has been shown to improve glucose tolerance and reduce hyperglycaemia in diabetic animals. Hydrogen peroxide and/or its vanadate complexes have been suggested responsible for these effects. Streptozotocin induced diabetic rats were treated with benzylamine (BZA) +/- vanadate (V) or insulin. In contrast to insulin, BZA + V treatment did not reduce HbA(1C) levels. However, it reduced the elevated serum SSAO activity, decreased the accumulation of advanced-glycation end products and increased the bioavailability of nitric oxide in diabetic animals, similarly to insulin. BZA alone did not affect any of these parameters.