Zamarrón et al. [1] report that obstructive sleep apnoea syndrome (OSAS) is associated with raised levels of markers of endothelial function. Moreover, some of these markers (intercellular cell adhesion molecule-1 (ICAM-1) and plasminogen activator inhibitor-1 (PAI-1)) improved after nasal continuous positive airway pressure [1]. Some additional comments may be of interest.
Metabolic syndrome (MetS) is highly prevalent in patients with OSAS [2]. In turn, intermittent hypoxia increases insulin resistance [2]. Consequently, it is difficult to identify the contribution of OSAS and MetS to vascular risk, since they share common predisposing factors (e.g. obesity [2] and endothelial dysfunction [3]). Markers of endothelial activation, including ICAM-1, PAI-1 and E-selectin, are raised in MetS [3] and Zamarrón et al. [1] report a similar pattern in OSAS. Platelet activation occurs in MetS due to reduced availability of endothelium-derived nitric oxide (NO) and prostacyclin [4]. Similarly, in OSAS a decrease in NO availability and prostacyclin/thromboxane metabolite ratio has been reported [2, 5]. Markers of platelet activation, including mean platelet volume (MPV) and platelet distribution width (PDW), were increased in OSAS, in parallel with the severity of hypoxia [6]. Therefore, it would be helpful to know how many patients in the control and OSAS group had MetS in the Zamarrón et al. [1] study.
Taken together, all these findings highlight the role of OSAS on endothelial integrity and as a contributor to cardiovascular risk.
References
- 1.Zamarrón C, Riveiro A, Gude F. Circulating levels of vascular endothelial markers in obstructive sleep apnoea syndrome. Effects of nasal continuous positive airway pressure. Arch Med Sci. 2011;7:1023–28. doi: 10.5114/aoms.2011.26615. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 2.Kostapanos MS, Elisaf MS, Mikhailidis DP. Obstructive sleep apnea and cardiovascular risk. Angiology. 2012;63:569–73. doi: 10.1177/0003319711436077. [DOI] [PubMed] [Google Scholar]
- 3.Tziomalos K, Athyros VG, Karagiannis A, Mikhailidis DP. Endothelial dysfunction in metabolic syndrome: prevalence, pathogenesis and management. Nutr Metab Cardiovasc Dis. 2010;20:140–6. doi: 10.1016/j.numecd.2009.08.006. [DOI] [PubMed] [Google Scholar]
- 4.Santilli F, Vazzana N, Liani R, Guagnano MT, Davi G. Platelet activation in obesity and metabolic syndrome. Obes Rev. 2012;13:27–42. doi: 10.1111/j.1467-789X.2011.00930.x. [DOI] [PubMed] [Google Scholar]
- 5.Krieger J, Benzoni D, Sforza E, Sassard J. Urinary excretion of prostanoids during sleep in obstructive sleep apnoea patients. Clin Exp Pharmacol Physiol. 1991;18:551–5. doi: 10.1111/j.1440-1681.1991.tb01490.x. [DOI] [PubMed] [Google Scholar]
- 6.Nena E, Papanas N, Steiropoulos P, et al. Mean platelet volume and platelet distribution width in non-diabetic subjects with obstructive sleep apnoea syndrome: new indices of severity? Platelets. 2012;23:447–54. doi: 10.3109/09537104.2011.632031. [DOI] [PubMed] [Google Scholar]