The Level Of Serum Leptin And Its Correlation With Insulin Resistance In OSAHS Patients

Objectives: 1.To investigate the changes of fasting serum leptin and insulin level in obstructive sleep apnea-hypopnea syndrome (OSAHS) patients. 2.To study the correlation between serum leptin level and insulin resistance in OSAHS patients. 3.To assess the role of serum leptin and insulin resistance in the development of OSAHS. Methods: Fifty males with OSAHS and fifty age-matched male normal controls were included in the study. Subjects in each group were divided into two sub-groups according to body mass index (BMI): obese group(BMI≥25 kg/m2, n=30)and non-obese group (BMI<25 kg/m2, n=20). Their height, weight, circumferences of neck, waist and hip were measured. Meanwhile, BMI, waist/hip ratio(WHR) and percentage of body fat(%FAT) were calculated. All the subjects underwent an overnight sleep study in the sleep laboratory. OSAHS was defined by apnea-hypopnea index (AHI)≥5 events/h. The main sleep parameters were recorded including: AHI, the minimum oxygen saturation, the longest apnea/hypopnea duration and microarousal index. On the morning right after the sleep study, venous blood was sampled in the fasting state for the measurement of glucose, leptin and insulin. Fasting plasma glucose(FPG) was measured by glucose oxidase method. The levels of serum leptin and insulin were measured by ELISA and radioimmunoassay, respectively. Insulin resistance was assessed by Homeostasis Model Assessment method. Serum leptin level, FPG, fasting insulin level, HOMA-IR, circumferences of neck and waist, WHR, BMI and age were compared respectively between OSAHS patients and non-OSAHS controls. The correlations of serum leptin level, fasting insulin level, HOMA-IR and sleep parameters were analyzed. Then the correlation between serum leptin level and insulin resistance was evaluated in OSAHS patients. Results: 1. Except for neck circumference, there were no significant differences in age, BMI, %FAT, waist circumference and WHR between OSAHS patients and non-OSAHS controls(p＞0.05). Compared with control subjects, levels of fasting leptin and insulin were significantly higher in obese and non-obese OSAHS subjects (p<0.01). Similarly, HOMA-IR was significantly higher in the OSAHS patients than that in control subjects (p<0.01). Moreover, the level of fasting glucose in the OSAHS patients showed a significantly higher trend(p<0.01). 2. In obese OSAHS sub-group, serum leptin level was positively correlated with AHI, the longest apnea/hypopnea duration and microarousal index (AHI: r=0.518, p<0.01; the longest apnea/hypopnea duration: r=0.500, p<0.01; microarousal index: r=0.432, p<0.05). However, serum leptin level was negatively correlated with the minimum oxygen saturation (r=-0.481, p<0.01). There were similar correlations between serum leptin level and sleep parameters in non-obese OSAHS sub-group (AHI: r=0.529, p<0.05; the longest apnea/hypopnea duration: r=0.519, p<0.05; microarousal index: r=0.693, p<0.01; the minimum oxygen saturation: r=-0.521, p<0.05). 3. Statistical correlations between fasting insulin level and sleep parameters were similar in both obese and non-obese OSAHS subjects. Fasting insulin level was positively correlated with AHI (obese OSAHS sub-group: r=0.473, p<0.01; non-obese OSAHS sub-group: r=0.606, p<0.01), the longest apnea/hypopnea duration (obese OSAHS sub-group: r=0.429, p<0.05; non-obese OSAHS sub-group: r=0.491, p<0.05), microarousal index (obese OSAHS sub-group: r=0.398, p<0.05; non-obese OSAHS sub-group: r=0.503, p<0.05), and negatively correlated with the minimum oxygen saturation(obese OSAHS sub-group: r=-0.513, p<0.01; non-obese OSAHS sub-group: r=-0.525, p<0.05). 4. In obese OSAHS sub-group, HOMA-IR was correlated with the severity of OSAHS as follows: AHI, r=0.461, p<0.05; the longest apnea/hypopnea duration, r=0.446, p<0.05; microarousal index, r=0.371, p<0.05; the minimum oxygen saturation, r=-0.521, p<0.01. There were similar correlations between HOMA-IR and sleep parameters in non-obese OSAHS sub-group. 5. In whichever sub-group, obese OSAHS sub-group...