title: What do changes in concentrations of serum surfactant proteins A and D in OSA mean?
abstract: OBJECTIVE
  Previous studies have shown that surfactant proteins are affected by oxygen concentration and mechanic stretches, although the alteration of serum surfactant proteins in individuals with obstructive sleep apnea (OSA) is still unclear. Therefore, the aim of this study is to examine whether serum concentrations of surfactant proteins A and D are altered and related to hypopnea index (HI) in OSA.
  
  
  METHODS
  This is a cross-sectional study. Consecutive 140 males, suspicious of OSA, were studied. OSA was determined by PSG and polysomnographic data examined. Subjects with HI ≥ 10.1/h were classified as higher HI group and those with HI < 10.1/h as lower HI group. Hs-CRP, HbA1C, and FBG were determined by standard methods and Krebs von den Lungen-6 (KL-6), surfactant protein-A (SP-A), and surfactant protein-D (SP-D) by ELISA.
  
  
  RESULTS
  OSA was diagnosed in 110 patients (78.5%). Mild, moderate, and severe OSA constitutes 26.4, 27.8, and 24.3%, respectively. Mean age was 44.6 ± 7.65 years. Subjects with higher HI had lower SP-A (139.54. ± 32.94 vs 158.2 ± 38.9 ng/L, p = 0.005) and SP-D (16.54 ± 3.67 vs 18.10 ± 3.48 ng/L, p = 0.014) compared to those with lower HI. Nocturnal HI was strongly correlated with serum levels of SP-A (r = 0.343, p = 0.012) and SP-D (r = 0.504, p < 0.001) and are inversely associated with circulating SP-A and SP-D levels, even after adjusting for age and body mass index in nonsmoking subjects.
  
  
  CONCLUSIONS
  Circulating SP-A and SP-D levels are decreased in some individuals with higher HI in OSA, possibly reflecting severity of hypoxia in OSA.
authors.affiliation: The Center of Hypertension of the People's Hospital of Xinjiang Uygur Autonomous Region, The Center of Diagnosis, Treatment and Research of Hypertension in Xinjiang, Tianchi Road No. 91 Tianshan District, Urumqi, 830001, Xinjiang, China.
authors.forename: Shao
authors.initials: S
authors.lastname: Liang
authors.forename: Nanfang
authors.initials: N
authors.lastname: Li
authors.forename: Mulalibieke
authors.initials: M
authors.lastname: Heizhati
authors.forename: Xiaoguang
authors.initials: X
authors.lastname: Yao
authors.forename: Arikin
authors.initials: A
authors.lastname: Abdireim
authors.forename: Yingchun
authors.initials: Y
authors.lastname: Wang
authors.forename: Zufeiya
authors.initials: Z
authors.lastname: Abulikemu
authors.forename: Delian
authors.initials: D
authors.lastname: Zhang
authors.forename: Guijuan
authors.initials: G
authors.lastname: Chang
authors.forename: Jianqiong
authors.initials: J
authors.lastname: Kong
authors.forename: Ling
authors.initials: L
authors.lastname: Zhou
authors.forename: Jing
authors.initials: J
authors.lastname: Hong
authors.forename: Ting
authors.initials: T
authors.lastname: Ying
authors.forename: Yongping
authors.initials: Y
authors.lastname: Zhang
mesh_terms: D000328:Adult; D003430:Cross-Sectional Studies; D006801:Humans; D016014:Linear Models; D008170:Lung Compliance / Q000502:physiology; D008297:Male; D008875:Middle Aged; D010100:Oxygen / Q000097:blood; D017286:Polysomnography; D037662:Pulmonary Surfactant-Associated Protein A / Q000097:blood*; D037663:Pulmonary Surfactant-Associated Protein D / Q000097:blood*; D012044:Regression Analysis; D020181:Sleep Apnea, Obstructive / Q000097:blood* / Q000145:classification / Q000175:diagnosis*; D013223:Statistics as Topic
chemical_list: D037662:Pulmonary Surfactant-Associated Protein A; D037663:Pulmonary Surfactant-Associated Protein D; D010100:Oxygen