Correlation between total nitrite/nitrate concentrations and monoamine oxidase (types A and B) and semicarbazide-sensitive amine oxidase enzymatic activities in human mesenteric arteries from non-diabetic and type 2 diabetic patients

Abstract

The aim of this study was to determine the correlation between total nitrite/nitrate concentrations (NOx) and the kinetic parameters of monoamine oxidase enzymes (MAO-A and MAO-B) and semicarbazide-sensitive amine oxidase (SSAO) in human mesenteric arteries. Arteries were from non-diabetic and type 2 diabetic patients with sigmoid or rectum carcinoma for whom surgery was the first option and who were not exposed to neo-adjuvant therapy. Segments of human inferior mesenteric arteries from non-diabetic (61.1 ± 8.9 years old, 7 males and 5 females, N = 12) and type 2 diabetic patients (65.8 ± 6.2 years old, 8 males and 4 females, N = 12) were used to determine NOx concentrations and the kinetic parameters of MAO-A, MAO-B and SSAO by the Griess reaction and by radiochemical assay, respectively. The NOx concentrations in arteries from diabetic patients did not differ significantly from those of the non-diabetic group (10.28 ± 4.61 vs 10.71 ± 4.32 nmol/mg protein, respectively). In the non-diabetic group, there was a positive correlation between NOx concentrations and MAO-B parameters: Km (r = 0.612, P = 0.034) and Vmax (r = 0.593, P = 0.042), and a negative correlation with the SSAO parameters: Km (r = -0.625, P = 0.029) and Vmax (r = -0.754, P = 0.005). However, in the diabetic group no correlation was found between NOx concentrations and the three kinetic parameters of the enzymes. These results suggest an important function of sympathetic nerves and vascular NOx concentrations in arteries of non-diabetic patients. Thus, these results confirm the importance of a balance between oxidants and antioxidants in the maintenance of vascular homeostasis to prevent oxidative stress.

Is nitrate a good biomarker of the nitric oxide status? / Este ionul nitrat un bun biomarker al producţiei endogene de monoxid de azot?

“…The experiments made with the blank suggest that the changes in nitrite concentrations are more predictable than those of nitrate, and should, therefore, be used preferentially when an spontaneous change in the nitric oxide status is tracked. In this case, NOx concentrations measured as a sum of nitrite and nitrate, as it is done frequently in scientific literature for assessment of human nitric oxide status (8)(9)(10)(11)(12), could lead to misinterpretation of data. Literature data shows that epilepsy, multiple sclerosis (9), changes in the mesenteric arteries of diabetic patients (10), were correlated with the concentration of NOx.…”

“…There are several cases described in the literature, in which NOx concentrations measured as a sum are linked to several diseases (8)(9)(10)(11)(12), but in these cases long term changes in nitric oxide formation is tracked. In such cases, nitrate concentrations increase if high nitrite amounts are generated continuously, due to its far higher half life (5.8 hours) compared with that of nitrite (0.58 hours).…”

“…This is based on the reduction of nitrate to nitrite by various reagents, followed by the well known Griess reaction when a colored azo dye is formed after the reaction of nitrite with sulphanilic acid and 1-naphtylamine (8)(9)(10)(11)(12).…”