Objective: To explore the association between serum lipoprotein lipase (LPL) level and dyslipidemia in patients with obstructive sleep apnea syndromes (OSAS).
Methods: Overnight polysomnography (PSG) was performed for 158 patients with snoring at our Sleep Center from June 2011 to April 2013. Based on the results of apnea-hypopnea index (AHI) assessment, they were divided into 4 groups: primary snoring (AHI<5/h, n = 26), mild (5/h ≤ AHI ≤ 15/h, n = 23), moderate (15/h < AHI ≤ 30/h, n = 31) and severe (AHI>30/h, n = 78) OSAS. According to body mass index (BMI), primary snoring group was further divided into normal BMI and overweight (obese) groups. The level of LPL was determined by enzyme-linked immunosorbent assay (ELISA) and the correlations were observed with OSAS, blood total cholesterol (TC), triglyceride (TG), high density lipoprotein (HDL), low density lipoprotein (LDL) and very low density lipoprotein (VLDL).In normal weight OSAS patients, the relationship was analyzed between different conditions, plasma lipid and serum LPL.In 49 OSAS groups, the level of LPL was observed after 6-month continuous positive airflow pressure (CPAP).
Results: From a comparison of four groups, it was found that AHI, night blood lowest oxygen saturation (L-SaO2) and time ratio of lowest SaO2<90% (TS90%) had statistical significance (all P < 0.01). The serum LPL gradually decreased in four groups. Compared with primary snoring group, there was a significant increase of serum LPL level in severe OSAS group ((37 ± 15) vs (45 ± 17) µg/L, P = 0.022). And severe OSAS group had significantly higher serum levels of TC, TG and LDL (P = 0.025,0.001,0.049).HDL of OSAS group was significantly lower than that of primary snoring group (all P < 0.05). Additionally, after adjustment for BMI and age, serum LPL levels showed significant negative correlations with TC and LDL (r = 0.221,0.199) .Serum LPL level was negative correlated with AHI and TS90 % and oxygen decrease index (ODI) (r = 0.231,0.228,0.184). Compared with normal BMI patients, there was a significant increase of VLDL ((0.77 ± 0.30) vs (0.46 ± 0.23) mmol/L, P = 0.034) and decrease of LPL ((37 ± 10) vs (523 ± 23) µg/L, P = 0.047) in weight (obesity) in primary snoring group. Compared with primary snoring group in normal BMI groups, there was a significant increase of TG,VLDL and decrease of LPL, HDL in OSAS group (all P < 0.05). The level of LPL significantly increased after 6-month CPAP ((60 ± 6) vs (38 ± 3) µg/L, P = 0.001).
Conclusions: Serum LPL and plasma lipid decrease in OSAS patients. And serum LPL level is correlated significantly with the severity of OSAS and nocturnal hypoxia. Thus LPL may play some roles in dyslipidemia of OSAS patients.