Nitric oxide metabolites and erythrocyte deformability in a group of subjects with obstructive sleep apnea syndrome

Abstract

Our aim was to evaluate nitric oxide metabolites (nitrite and nitrate), expressed as NOx, and erythrocyte deformability, expressed as elongation index, in a group of subjects with obstructive sleep apnea syndrome (OSAS). We enrolled 48 subjects (36 men and 12 women; mean age 50.3 ± 14.68 yrs) with OSAS diagnosed after a 1-night cardiorespiratory sleep study. OSAS severity was assessed evaluating the apnea/hypopnea index (AHI) and subjects were subdivided in two subgroups: Low (L = AHI <30) and High (H = AHI >30). NOx was examined converting nitrate into nitrite with a nitrate reductase and then assessing nitrite with spectrophotometry after the addition of Griess reagent. The elongation index was obtained using the diffractometer Rheodyn SSD of Myrenne at shear stresses of 30 and 60 Pa and it was expressed as elongation index (EI). We found no difference in NOx among the entire group of OSAS subjects and normal controls, while we observed a NOx decrease in the H subgroup in comparison with L subgroup, but not in comparison with normal controls. We noted a significant decrease in EI at each shear stress in the entire group and also in the two subgroups in comparison with controls. The decrease in NO bioavailability and in erythrocyte deformability might contribute to explain the increased cardiovascular risk in OSAS subjects.

Association of matrix metalloproteinase‐9 and nitric oxide with hypertension in obstructive sleep apnea

“…However, the results are controversial. Some researchers found that circulating NO was reduced in OSA patients, 40,41 whereas another study did not find difference of plasma stable NO products nitrite (NOx) between OSA subjects and controls 42 . In our research, we only found lower serum NO level in patients with severe OSA.…”

Obstructive Sleep Apnea Syndrome: Links Betwen Pathophysiology and Cardiovascular Complications

“…Similarly, Cifci et al in 69 OSAS subjects with an AHI ≥ 15 [33]. Canino et al [36] found decreased NOx in subjects with AHI >30 in comparison with subjects with AHI<30, but not in comparison with normal controls. They also observed a negative correlation between NOx and AHI and a positive correlation between NOx and mean nocturnal SO 2 .…”

“…Tazbirek et al found elevated blood viscosity and erythrocyte aggregation in obese men with OSAS, in comparison with those without OSAS [79] while Sinnapah et al [80] found a correlation between erythrocyte aggregation and AHI and between erythrocyte aggregation and BMI in overweight OSAS subjects. The erythrocyte deformability, obtained with a diffractometric method and expressed as elongation index (EI), was significantly reduced in 48 OSAS subjects (mean AHI 38.47±25.66) [36], even if other authours [79,81] did not find this alteration in erythrocyte deformability when employing other techniques. It has been demonstrated that treatment with cPAP reduces plasma fibrinogen [76] and blood and plasma viscosity [79].…”

Metabolic Influences Modulating Erythrocyte Deformability and Eryptosis

“…Another situation associated with a decrease in RBC deformability which is probably multifactorial is obstructive sleep apnea syndrome (OSAS). This syndrome has emerged over recent decades as an important risk factor for atherosclerosis and cardiovascular disorders [231][232][233]. In OSAS, endothelial dysfunction is markedly disturbed due to recurrent hypoxemic events, and there is a decrease in erythrocyte deformability [231].…”

“…In OSAS, endothelial dysfunction is markedly disturbed due to recurrent hypoxemic events, and there is a decrease in erythrocyte deformability [231]. Additionally, a decrease in NO bioavailability is also observed and may be both a consequence and a worsening factor of the defect in RBC deformability [232]. In this disease, there is also an increase in plasma viscosity and an increase in RBC aggregation [231].…”