Arginase activity and nitric oxide levels in patients with obstructive sleep apnea syndrome.
OBJECTIVE
Obstructive sleep apnea syndrome is characterized by repetitive obstruction of the upper airways, and it is a risk factor for cardiovascular diseases. There have been several studies demonstrating low levels of nitric oxide in patients with obstructive sleep apnea syndrome compared with healthy controls. In this study, we hypothesized that reduced nitric oxide levels would result in high arginase activity. Arginase reacts with L-arginine and produces urea and L-ornithine, whereas L-arginine is a substrate for nitric oxide synthase, which produces nitric oxide.


METHODS
The study group consisted of 51 obstructive sleep apnea syndrome patients (M/F: 43/8; mean age 49±10 years of age) and 15 healthy control subjects (M/F: 13/3; mean age 46±14 years of age). Obstructive sleep apnea syndrome patients were divided into two subgroups based on the presence or absence of cardiovascular disease. Nitric oxide levels and arginase activity were measured via an enzyme-linked immunosorbent assay of serum samples.


RESULTS
Serum nitric oxide levels in the control subjects were higher than in the obstructive sleep apnea patients with and without cardiovascular diseases (p<0.05). Arginase activity was significantly higher (p<0.01) in obstructive sleep apnea syndrome patients without cardiovascular diseases compared with the control group. Obstructive sleep apnea syndrome patients with cardiovascular diseases had higher arginase activity than the controls (p<0.001) and the obstructive sleep apnea syndrome patients without cardiovascular diseases (p<0.05).


CONCLUSIONS
Low nitric oxide levels are associated with high arginase activity. The mechanism of nitric oxide depletion in sleep apnea patients suggests that increased arginase activity might reduce the substrate availability of nitric oxide synthase and thus could reduce nitric oxide levels.
Department of Medical Laboratory Techniques, Vocational School of Health Services, Marmara University, Istanbul, Turkey.
Meral
M
Yüksel
Chest Diseases Clinics, Fatih Sultan Mehmet Research and Education Hospital, Istanbul, Turkey.
Hacer Kuzu
HK
Okur
Vocational School of Health-related Professions, Gazikent Hasan Kalyoncu University, Gaziantep, Turkey.
Zerrin
Z
Pelin
Department of Medical Laboratory Techniques, Vocational School of Health Services, Marmara University, Istanbul, Turkey.
Ayliz Velioğlu
AV
Öğünç
Department of Physiology, Faculty of Medicine, Trakya University, Edirne, Turkey.
Levent
L
Öztürk
D000328:Adult; D000704:Analysis of Variance; D001119:Arginase / Q000097:blood*; D001120:Arginine / Q000378:metabolism; D015992:Body Mass Index; D002318:Cardiovascular Diseases / Q000378:metabolism; D016022:Case-Control Studies; D004797:Enzyme-Linked Immunosorbent Assay; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009569:Nitric Oxide / Q000097:blood*; D019001:Nitric Oxide Synthase / Q000097:blood*; D017286:Polysomnography; D020181:Sleep Apnea, Obstructive / Q000097:blood* / Q000201:enzymology
D009569:Nitric Oxide; D001120:Arginine; D019001:Nitric Oxide Synthase; D001119:Arginase