Significantly increased levels of the NADPH oxidase, decreased expression of eNOS and inducible nitric oxide synthase (iNOS) genes, increased activity of angiotensin-converting enzyme (ACE)-1 were noticed in saline-treated OSA rats, indicating that OSA-induced oxidative stress and dysfunction of renin-angiotensin system were mainly responsible for aortic remodeling [35]. Here, REN is linked to obstructive sleep apnea syndrome.