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Published on: December 6, 2016
Evaluation of continuous positive airway pressure therapy on renin-angiotensin system activity in obstructive sleep
David D M Nicholl1, Patrick J Hanly, Marc J Poulin
11 Department of Medicine.
Rationale:
Obstructive sleep apnea (OSA) has been associated with kidney function loss, which may be related to changes in the renin-angiotensin system (RAS).
Objectives:
We sought to determine the effect of continuous positive airway pressure (CPAP) of patients with OSA on renal hemodynamics at baseline and in response to angiotensin II (AngII), which reflects RAS activity.
Methods:
Twenty normotensive, nondiabetic, newly diagnosed OSA subjects (15 men, 5 women, 50 ± 2 yr, respiratory disturbance index [RDI] > 15 h(-1)) with nocturnal hypoxemia (SaO2 < 90% for >12% of the night) were studied in high-salt balance pre- and post-CPAP therapy (>4 h CPAP use/night for 1 mo). Glomerular filtration rate (GFR), renal plasma flow (RPF), and filtration fraction (FF) (a surrogate marker for intraglomerular pressure) were measured pre- and post-CPAP using inulin and para-aminohippurate clearance techniques at baseline and in response to graded AngII infusion (3 ng/kg/min × 30 min and 6 ng/kg/min × 30 min, respectively).
Measurements And Main Results:
CPAP corrected OSA and hypoxemia (RDI: 42 ± 4 vs. 4 ± 1 h(-1), P < 0.001; duration SaO2 < 90%: 36% ± 5% vs. 6 ± 2%, P < 0.001). CPAP reduced GFR (124 ± 8 ml/min vs. 110 ± 6 ml/min, P = 0.014), increased RPF (692 ± 36 ml/min vs. 749 ± 40 ml/min, P = 0.059), and reduced baseline FF (18.9 ± 1.6% vs. 15.3 ± 1.0%, P = 0.004). Post-CPAP demonstrated a blunted GFR response (-9 ± 3 ml/min vs. -2 ± 2 ml/min, P = 0.033) and augmented RPF response (-182 ± 22 ml/min vs. -219 ± 25 ml/min, P = 0.024) to AngII. FF response was maintained (P = 0.4). CPAP reduced baseline mean arterial pressure (94 ± 2 vs. 89 ± 2 mm Hg, P = 0.002), plasma aldosterone (149 ± 18 vs. 109 ± 10 pmol/L, P = 0.003), and urinary protein excretion (61 [39-341] mg/day vs. 56 [22-204] mg/d, P = 0.003).
Conclusions:
CPAP therapy was associated with improved renal hemodynamics and down-regulation of renal RAS activity, suggesting a potential therapeutic benefit for kidney function.
Insights
Continuous positive airway pressure (CPAP) therapy improved kidney function in obstructive sleep apnea (OSA) patients by enhancing renal hemodynamics and reducing renin-angiotensin system (RAS) activity.
Area of Science:
- Nephrology
- Sleep Medicine
- Cardiovascular Physiology
Background:
- Obstructive sleep apnea (OSA) is linked to kidney function decline.
- Renin-angiotensin system (RAS) overactivity may mediate this association.
- Understanding the impact of OSA treatment on renal hemodynamics is crucial.
Purpose of the Study:
- To investigate the effects of continuous positive airway pressure (CPAP) on renal hemodynamics in OSA patients.
- To assess how CPAP influences the response to angiotensin II (AngII), a marker of RAS activity.
- To determine if CPAP modulates baseline renal function and RAS markers.
Main Methods:
- Twenty OSA patients underwent renal function tests (GFR, RPF, FF) before and after 1 month of CPAP therapy.
- Measurements were taken at baseline and during graded AngII infusion.
- Plasma aldosterone and urinary protein excretion were also assessed.
Main Results:
- CPAP effectively treated OSA and nocturnal hypoxemia.
- CPAP reduced baseline GFR and filtration fraction (FF), while increasing renal plasma flow (RPF).
- Post-CPAP, the renal response to AngII was altered, with a blunted GFR decrease and augmented RPF increase, suggesting RAS down-regulation. Mean arterial pressure, aldosterone, and proteinuria also decreased.
Conclusions:
- CPAP therapy improves renal hemodynamics in OSA patients.
- CPAP down-regulates renal renin-angiotensin system (RAS) activity.
- These findings suggest CPAP may offer therapeutic benefits for kidney function in OSA.
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