| Objectives: To investigate the serum 8-OHdG and serum MnSOD concentrations in patients with obstructive sleep apnea-hypopnea syndrome (OSAHS) without complications and in those with obsturctive sleep apnea-hypopnea associated hypertension (OSAHS+HT). To evaluate the relationship between three biochemical parameters and OSAHS and OSAHS+HT in order to explore the change of oxidant stress and oxidative DNA damage in patients with OSAHS and OSAHS+HT. To study the role of serum 8-OHdG and serum MnSOD in the pathogenesis and progress of OSAHS+HT.Methods: Forty males with OSAHS were included randomly in the study and twenty age-matched and body mass index (BMI) -matched healthy men served as control subjects. OSAHS patients with nocturnal snoring, apnea and excessive daytime sleepiness syndrome and control subjetcs without those syndromes underwent overnight polysomnography (PSG) and portal sleep apnea monitoring, respectively. Inclusion criteria for the present study were apnea-hypopnea index (AHI)≥5/h for OSAHS patients and AHI<5/h for control subjects. Apnea was defined as an absence of airflow for≥10s, and hypopnea was defined as a reduction of airflow associated with a reduction of oxygen saturation by 4% from baseline. The AHI was defined as the average of apneic and hypopneic events per sleep hour. All patients with OSAHS were divided into two subgroups:20 OSAHS patients without complications (age= 49.40±9.31, BMI=29.81±3.38kg/m2) and 20 OSAHS+HT patients (age =43.95±9.17, BMI=28.49±3.18kg/m2). Occurrence of hypertension was later than that of OSAHS in patients with OSAHS+HT. Other secondary hypertension (such as renovascular and endocrinic hypertension) were excluded in OSAHS+HT patients. There were no significant differences in age and BMI among control subjects (age=47.55±11.18, BMI=28.62±3.27kg/m2), OSAHS and OSAHS+HT subjects. Smoking, drinking, diets, drugs and other disturbance factors were excluded in this study. Fasting venous blood were obtained from all observed subjects after sleep-breathing monitoring within the following 5 minutes in the next morning. The serum 8-OHdG concentrations were measured by ELISA, the serum MnSOD contents were detected by xanthine oxidase method, respectively. Differences in serum 8-OHdG and MnSOD among three groups were assessed by using one-way analysis of variance and further multiple comparisons were performed with SNK-q test. Sleep-breathing parameters of patients with OSAHS without complications were compared with those of patients with OSAHS+HT by using student's two- tailed t test. Furthermore, linear correlations were performed between three biochemical parameters and sleep-breathing parameters of patients with OSAHS and OSAHS+HT, respectively.Results: 1. the serum 8-OHdG and serum MnSOD concentrations were 1.50±1.33ng/ml,12.45±5.15U/ml in control subjects, were 2.69±2.11ng/ml,10.49±6.60U/ml,in patients with OSAHS and 3.16±2.54ng/ml,7.18±4.34 U/ml in patients with OSAHS+HT, respectively. The serum 8-OHdG concentrations were higher, serum MnSOD concentrations were lower in patients with OSAHS compared with those in control subjects. There were statistical significances (q=7.405, 3.934, respectively; p<0.01). There were similar results in patients with OSAHS+HT compared with those in control subjects and significant differences were found (q=10.290, 10.579, respectively; p<0.01). Compared with OSAHS patients, there was a decreased trend of serum MnSOD concentrations in the patients with OSAHS+HT, but this difference reached statistical significance (q=2.885, 6.644, respectively; p<0.01). 2. Compared with OSAHS patients, both AHI and percentage of sleep time below 90% oxygen saturation (SaO2<90%) and percentage of sleep time the total duration of apnea/hyponea were higher in OSAHS+HT patients (t=2.95, 2.18, 2.24, repectively; p<0.01), both the lowest SaO2 and average the lowest SaO2 were lower in OSAHS+HT patients (t=2.96, p<0.05; t=2.33, p<0.05). But there were no differences in the longest duration of apnea/hypopnea between two subgroups(p>0.05). 3. The linear correlations were found between three biochemical parameters and sleep-breathing parameters in patients with OSAHS and OSAHS+HT as follows:①The serum 8-OHdG levels were correlated positively with AHI both in OSAHS and OSAHS+HT patients (r=0.974, p<0.01; r=0.765, p<0.01), were correlated positively with SaO2<90% (r=0.739, p<0.01; r=0.702, p<0.01), were correlated positively with percentage of sleep time the total duration of apnea/hyponea (r=0.829, p<0.01; r=0.583, p<0.01), were correlated negatively with the lowest SaO2 (r=-0.751, p<0.01; r=-0.560, p<0.05) and were correlated negatively with average the lowest SaO2 (r=-0.718, p<0.01; r=-0.808, p<0.01). The correlations were not found between the longest dutation of apnea/hypopnea and levels of three biochemical parameters in patients with OSAHS and OSAHS+HT. (r=0.185, p>0.05; r=0.023, p>0.05).②The correlations between serum MnSOD and sleep-breathing parameters were not as same as those of 8-OHdG. MnSOD levels levels were correlated negatively with AHI both in OSAHS and OSAHS+HT patients (r=-0.806, p<0.01; r=-0.929, p<0.01), were correlated negatively with SaO2<90% both in OSAHS and OSAHS+HT patients (r=-0.567, p<0.01; r=-0.758, p<0.01), were correlated negatively with percentage of sleep time the total duration of apnea/hyponea (r=-0.738, p<0.01; r=-0.809, p<0.01), were correlated positively with the lowest SaO2 (r=0.612, p<0.01; r=0.567, p<0.01), and were correlated positively with average the lowest SaO2 (r=0.518, p<0.05; r=0.742, p<0.01). And there were no correlations with the longest dutation of apnea/hypopnea (r=-0.210, p > 0.05; r=-0.099, p>0.05).Conclusions: 1. Despite controlling for age, BMI and excluding disturbance factors such as smoking, drinking, diets and drugs, the resum 8-OHdG concentrations in patients with OSAHS and OSAHS+HT were higher than those in control subjects. The resum 8-OHdG levels were correlated positively to both AHI and SaO2<90% and were correlated negatively to both the lowest SaO2 and average the lowest SaO2 . which showed a strong correlation between 8-OHdG increasing with the degree of hypoxemia. Both the MnSOD levels in patients with OSAHS and OSAHS+HT were lower than those in control subjects. MnSOD levels were correlated negatively to AHI and SaO2<90% and correlated positively to the lowest SaO2 and average the lowest SaO2 , which showed a strong correlation between MnSOD reducing with the degree of hypoxemia. 2. MnSOD,as an important antioxidant enzyme in mitochondria,which can catalyze the dismutation of superoxide ion,and protect the cells from oxidative damage.It is important that the stable level of MnSOD maitaining the normal physiology function of the cells. The content of 8-hydroxydeoxyguanosine (8-OHdG) by which the cellular DNA damage caused by active oxygen species. The serum MnSOD contents in patients with OSAHS+HT was lower than those in patients with OSAHS. The serum 8-OHdG contents in patients with OSAHS+HT was higher than those in patients with OSAHS.Our study demonstrated the change of oxidative /anti- oxidative imbalance between oxidative stress and oxidative DNA damage in patients with OSAHS no matter with or without hypertension. The imbalance of oxidative /anti- oxidative was more obvious in patients with OSAHS+HT. Our study documents the existence of oxidative damage in OSAHS, which suggests that important oxidative stress of OSAHS occur independent of , and possibly prior to, the development of systemic hypertension. Several studies showed oxidative stress was significantly correlated with many of disease. The information of the severity of sleep disordered breathing and the degree of oxidative stress can be obtained by measuring the change of two biochemical parameters, which has important value to advice the early treatment and to improve the prognosis.
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