Relationships of orexigenic and anorexigenic hormones with body fat distribution in patients with obstructive sleep apnea syndrome.

PURPOSE: We aimed to examine the relationships of disease activity and risk factors with serum levels of orexigenic and anorexigenic hormones in patients with obstructive sleep apnea syndrome (OSAS). METHODS: Fasting blood samples were taken for hormonal analysis of all participants, abdominal/neck bioimpedance measurements were recorded, and polysomnography (PSG) analyses were performed. According to the apnea-hypopnea index (AHI), 34 patients with newly diagnosed OSAS and 34 participants without OSAS were compared. RESULTS: The median body mass index (BMI) measured in the OSAS group was 30.39 kg/m2 and AHI was 18.95 and these values were 25.40 kg/m2 and 1.55 in the control group. There was a higher level of visceral adiposity and neuropeptide Y (NPY) in the moderate-to-severe OSAS group compared to the mild OSAS and control groups, and in the mild OSAS group compared to the control group (p = 0.001, p < 0.001). A positive correlation between the level of NPY and AHI and BMI (p < 0.001, p = 0.011), and a negative correlation between NPY levels and oxygen saturation (p = 0.001) was found. Oxygen saturation and desaturation rates were correlated with body fat percentage, body fat mass, abdominal adiposity, visceral adiposity, resting metabolic rate, and NPY levels. CONCLUSIONS: The visceral adiposity ratio and increase in NPY levels are important parameters that increase the severity of OSAS. Considering the negative effects of NPY on vascular endothelium, measurement of basal NPY level before PSG in patients with OSAS is considered a parameter related to disease severity.

The Saliva Cortisol and Amylase Levels Related with Stress Response Compared by Different Analytical Methods.

Sampling of salivary cortisol and amylase is a non-invasive method and important for the evaluation of the hypothalamic-pituitary-adrenal axis function and stress levels. This study aimed to compare the values of the salivary cortisol and amylase levels which were measured by three different analytical methods to discuss the alterations of stress levels of samples. The saliva samples of young adults (n = 23) were collected between 08.00 and 09.00 a.m., noon at 12.00 (before exam) and between 14.00 and 15.00 p.m. (after unaware exam). The samples were measured within the first 48 h, and no freezing/thawing was done. Salivary cortisol and amylase levels of subjects were measured by three different analytical methods as ELISA, chemiluminescence and biosensor methods. Comparison of ELISA and biosensor methods in order to determine the salivary cortisol levels showed a good correlation y = 2.971 + 0.748x (R2 = 0.839). Salivary amylase concentrations were only detected by ELISA method. Biosensor can be offered as an alternative analytic method to the conventional determination method ELISA. It can be preferred because of the detection/information effectiveness, low cost, fast results and specificity characteristics.

The evaluation of serum brain-derived neurotrophic factor and neurofilament light chain levels in patients with obstructive sleep apnea syndrome.

OBJECTIVES: This study aimed to compare serum levels of brain-derived neurotrophic factor (BDNF) and neurofilament light (NfL) chain in normal individuals and patients with mild and moderate-severe obstructive sleep apnea syndrome (OSAS). METHODS: We enrolled 81 subjects referred to Otorhinolaryngology (Ear-Nose-Throat), Gazi University Faculty of Medicine, between 2017 and 2019. Based on the severity of OSAS, patients were divided into three groups: group 1 with mild OSAS (apnea-hypopnea index [AHI] 5-15; n = 26), group 2 with moderate-severe OSAS (AHI > 15; n = 32), and group 3 with normal individuals (AHI scores < 5; n = 23). RESULTS: Serum NfL and BDNF levels were evaluated together with the clinical data for all subjects. Significant differences were seen in the oxygen desaturation index (ODI), apnea index, hypopnea index, sleep efficiency, and NfL levels (P < .05) between the three groups. In the moderate-severe group, NfL levels showed a significant positive correlation with apnea index (P < .05, r = .389), hypopnea index (P < .05, r = .455), and ODI (P = .04; r = .362). CONCLUSIONS: Our findings clarify the pathophysiology of OSAS in cases of repetitive hypoxia and chronic neuronal damage. Based on our results, we recommend that in addition to BDNF, NfL should also be evaluated in different and larger patient cohorts.

The evaluation of serum tryptophan and kynurenine levels in patients with obstructive sleep apnea syndrome.

PURPOSE: The kynurenine (Kyn) pathway may play a role in certain physiological functions such as behavior, sleep, thermoregulation, and pregnancy. Tryptophan (Trp) is oxidized with tryptophan 2,3-dioxygenase and indolamine 2,3-dioxygenase (IDO). Under normal conditions, hepatic kynurenine is a transcription factor and IDO expression in healthy tissues is very low. The ratio of Kyn to Trp can be used as an indicator to assess IDO activity. This study aimed to determine the relationship between Kyn/Trp ratio and obstructive sleep apnea syndrome (OSAS) disease activity. METHODS: Study participants were categorized in 3 groups: Group 1 included patients with mild OSAS, Group 2, patients with moderate to severe OSAS, and Group 3, individuals considered normal to serve as controls. The demographic characteristics of the patients were recorded. Apnea-hypopnea index (AHI) and oxygen desaturation index (ODI) measurements were performed by diagnostic polysomnography (PSG). Trp and Kyn levels were determined by HPLC-UV method. RESULTS: Group 1 included 30 patients (18 men) with mild OSAS; Group 2 included 42 patients (31 men) with moderate to severe OSAS; and Group 3 included 25 controls (13 men). While there was no statistically significant difference between the levels of tryptophan and kynurenine in the groups, a significant difference was found between the Kyn/Trp ratios. A significant correlation was observed in individuals with a body mass index less than 25 with the Kyn/Trp ratio. In individuals with mild OSAS, a significant correlation was observed between ODI and BMI. In individuals with moderate to severe OSAS, there was a significant correlation between ODI, AHI, and BMI. CONCLUSION: In this study, there was no relationship between OSAS disease severity and IDO activity as assessed by immunoreactivity via the Kyn/Trp pathway.