Urinary proteomics in obstructive sleep apnoea and obesity

Background: Obstructive sleep apnoea (OSA) is a common complication of obesity and can have a substantial negative impact on a patient's quality of life and risk of cardiovascular disease. The aim of this case-control study was to undertake discovery profiling of urinary peptides using capillary electrophoresis-mass spectrometry (CE-MS) in obese subjects with and without OSA, without a history of coronary artery disease.

Materials and methods: Urinary samples were analysed by CE-MS. Body composition and blood pressure measurements were recorded. Overnight polysomnography was conducted to confirm or refute OSA. OSA patients were naïve to continuous positive airway pressure treatment.

Results: Sixty-one subjects with OSA (age 47 ± 9 years, BMI 43 ± 8 kg/m(2)) and 31 controls (age 49 ± 10 years, BMI 40 ± 5 kg/m(2)) were studied; P = ns for age and BMI. Apnoea-hypopnoea Index was higher in patients with OSA (24 ± 18·6) than controls without OSA (non-OSA) (2·6 ± 1·1; P < 0·0001). Metabolic syndrome was present in 35 (57%) of those with OSA compared with 4 (13%) of controls (P < 0·0001). Twenty-four polypeptides were candidates for differential distribution (P < 0·01), although these differences did not reach significance after multiple testing. Sequences were determined for eight peptides demonstrating origins from collagens and fibrinogen alpha.

Conclusions: In this study, we report for the first time, urinary proteomic profile analyses using CE-MS in OSA and non-OSA obese groups. The differences in urinary proteomic profiles prior to adjustment for multiple testing, with increased metabolic syndrome in obese OSA subjects, suggest that there may be a role for CE-MS in characterising urinary profiles in severely obese populations with OSA.