Key result
In patients with obstructive sleep apnea, 12 weeks of CPAP therapy significantly reduced microcirculatory endothelial AT1 expression from 873 to 393 fluorescence units (P=0.02).
Why the study?
Does CPAP therapy reduce microcirculatory endothelial AT-1 expression in patients with recently diagnosed OSA and low CVD risk?
Observational (n=11)
Does CPAP therapy reduce microcirculatory endothelial AT-1 expression in patients with recently diagnosed OSA and low CVD risk?
In OSA patients with minimal CVD risk, CPAP therapy reverses the upregulation of AT-1 expression associated with vascular endothelial dysfunction.
Answers are grounded in this paper and cite their sources.
Hypothesis-generating for CPAP effects on endothelial AT1 in OSA; larger studies needed before clinical relevance.
BACKGROUND: Obstructive sleep apnea (OSA) is associated with vascular endothelial dysfunction (VED) in otherwise healthy patients. The role of renin-angiotensin system (RAS) in the OSA induced VED is not well understood. METHODS: Recently diagnosed OSA patients with very low cardiovascular disease (CVD) risk (Framingham score <5%) were studied at diagnosis and after 12 weeks of verified continuous positive airway pressure (CPAP) therapy. Participants underwent biopsy of gluteal subcutaneous tissue at baseline and after CPAP. Microcirculatory endothelial expression of angiotensin receptors type-1 (AT-1) and type-2 (AT-2) was measured in the subcutaneous tissue using quantitative confocal microscopy techniques. The ex-vivo effect of AT-1 receptor blockade (ARB) on endothelial superoxide production was also measured before and after CPAP treatment. RESULTS: In OSA patients (n = 11), microcirculatory endothelial AT1 expression decreased from 873 (200) (fluorescence units) at baseline to 393 (59) units after 12 weeks of CPAP (P = 0.02). AT2 expression did not decrease significantly in these patients (479 (75) to 329 (58) post CPAP (P = 0.08)). The ex-vivo addition of the losartan to the microcirculatory endothelium resulted in decreased superoxide expression in the vascular walls from 14.2 (2.2) units to 4.2 (0.8) P < 0.001; while it had no effect on post-CPAP patient tissue (P = 0.64). CONCLUSIONS: In OSA patients with no to minimal CVD risk, VED is associated with upregulation of AT-1 expression that is reversible with CPAP. Endothelial oxidative stress was reversible with ARB. RAS activation may play an important role in the development of early CVD risk in OSA patients.
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Khayat et al. (2017) conducted an observational in Obstructive Sleep Apnea (n=11). Continuous positive airway pressure (CPAP) therapy vs. Baseline was evaluated on Microcirculatory endothelial AT1 expression (fluorescence units) (p=0.02). In patients with obstructive sleep apnea, 12 weeks of CPAP therapy significantly reduced microcirculatory endothelial AT1 expression from 873 to 393 fluorescence units (P=0.02).
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