Determination of human serum semicarbazide-sensitive amine oxidase activity: a possible clinical marker of atherosclerosis

Abstract

Semicarbazide-sensitive amine oxidase (SSAO) is present in the plasma membrane of several human tissues, e.g. vascular smooth muscle cell adipocytes, and is also found in human serum. Some previous studies on cultured endothelial cells indicate that cytotoxic metabolites (e.g. hydrogen peroxide, formaldehyde, acrolein) formed by serum SSAO may cause endothelial injury and subsequently induce atherosclerosis. To investigate the role of this enzyme in the pathogenesis of macrovascular complications in diabetes, a simple and sensitive radiometric procedure was adapted for human serum measurements. Serum SSAO activity of 35 patients with non-insulin dependent diabetes mellitus (NIDDM) and that of 30 controls was determined using [14C]-benzylamine as substrate. The severity of atherosclerosis was assessed by carotid sonography. Diabetic patients with atherosclerosis exhibited a higher SSAO activity compared to diabetic patients without complications (212.91 +/- 90.54 pmol/mg protein/h versus 133.17 +/- 65.40 pmol/mg protein/h, P <0.04). In diabetic patients without complications, serum SSAO activity was elevated compared to control subjects (133.17 +/- 65.40 pmol/mg protein/h versus 91.79 +/- 31.70 pmol/mg protein/h, P <0.01). These results suggest that determination of human serum SSAO activity might be a useful marker in the prognostic evaluation of diabetic angiopathy and atherosclerosis.

Insulin-Regulated Increase of Soluble Vascular Adhesion Protein-1 in Diabetes

“…34,35 In these reports, however, only the total SSAO enzyme activity in serum has been analyzed by radioisotopic assays. Because there are at least three different SSAO genes reported so far in man, 11,36 -38 our molecular definition of VAP-1 allows for the first time the measurement of a specific SSAO enzyme.…”

Assay of plasma semicarbazide-sensitive amine oxidase and determination of its endogenous substrate methylamine by liquid chromatography

“…Quantitative HPLC methods had been reported for the determination of plasma formaldehyde [23,24]. Radiometric procedure using 14 C-benzylamine as substrate has been reported for human serum SSAO activity assay [25]. HPLC methods with fluorescence detection have also been reported for human plasma monoamine oxidase (MAO) and SSAO activity assay [26,27].…”

Probing the Catalytic Mechanism of Copper Amine Oxidase from Arthrobacter globiformis with Halide Ions

“…Eukaryotic CAOs have versatile functions, being involved in the detoxification of bio-active amines, such as histamine (4); cell adhesion (5); cell death (6); collagen cross-linking in animals (7); and germination, root growth, and healing of wounded cell walls in plants (8). It has been reported that human serum CAOs cause angiopathy in diabetes (9). Therefore, various CAO inhibitors have been developed as therapeutic drugs (10,11).…”