{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,9,27]],"date-time":"2026-09-27T07:19:05Z","timestamp":1790493545778,"version":"4.1.0"},"reference-count":62,"publisher":"American Physiological Society","issue":"5","funder":[{"name":"Shun Tak District Ming Yuen Tong of Hong Kong"},{"name":"Stanley Ho Matching Grant from The University of Hong Kong"},{"name":"Small Project Fund from the University of Hong Kong"}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Journal of Applied Physiology"],"published-print":{"date-parts":[[2018,11,1]]},"abstract":"<jats:p> Obstructive sleep apnea is characterized by intermittent hypoxia (IH) during sleep and predisposes to endothelial dysfunction. Obesity is a major risk factor for the occurrence of sleep apnea. The present study compared the functional impact of low- (IH10; 10 hypoxic events\/h) and high-frequency (IH60; 60 hypoxic events\/h) IH for 4 wk on endothelial function in male C57BL\/6 mice with or without high-fat (HF) diet-induced obesity. Mean arterial blood pressure (tail cuff method) was increased in obese mice after IH60 exposure, i.e., HF + IH60 group. The serum levels of the oxidative stress marker malondialdehyde were augmented in lean IH60 and HF groups, with a further increase in HF + IH60 but a reduction in HF + IH10 mice compared with the HF group. Vascular responsiveness was assessed as changes in isometric tension in isolated arteries. Relaxations to the endothelium-dependent vasodilator acetylcholine were impaired in HF + IH60 aortae. Endothelium-dependent contractions (EDC; response to acetylcholine in the presence of the nitric oxide synthase inhibitor l-NAME) in carotid arteries were augmented in the HF group, but this HF-induced augmentation was suppressed by low-frequency IH exposure. The addition of apocynin (antioxidant) reduced EDC in HF and HF + IH60 groups but not in HF + IH10 group. In conclusion, these findings suggest that exposure of obese mice to mild IH exerts preconditioning-like suppression of endothelium-dependent and oxidative stress-mediated contractions. When IH severity increases, this suppression diminishes and endothelial dysfunction accelerates. <\/jats:p><jats:p> NEW &amp; NOTEWORTHY The present study demonstrates, for the first time, that low-frequency intermittent hypoxia may exert a preconditioning-like suppression of oxidative stress-induced endothelium-dependent contractions in mice with diet-induced obesity. This relative suppression was diminished as intermittent hypoxia became more severe, and a deleterious effect on endothelial function emerged. <\/jats:p>","DOI":"10.1152\/japplphysiol.00224.2018","type":"journal-article","created":{"date-parts":[[2018,8,9]],"date-time":"2018-08-09T10:44:37Z","timestamp":1533811477000},"page":"1384-1395","source":"Crossref","is-referenced-by-count":9,"title":["Low but not high frequency of intermittent hypoxia suppresses endothelium-dependent, oxidative stress-mediated contractions in carotid arteries of obese mice"],"prefix":"10.1152","volume":"125","author":[{"given":"Mary Y. 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