Abstract
ObjectivesIntermittent hypoxia (IH), resulted from recurring episodes of upper airway obstruction, is the hallmark feature and the most important pathophysiologic pathway of obstructive sleep apnea (OSA). IH is believed to be the most important factor causing systemic inflammation. Studies suggest that insulin resistance (IR) is positively associated with OSA. In this study, we hypothesized that the recurrence of IH might result in cellular and systemic inflammation, which was manifested through the levels of proinflammatory cytokines and adipokines after IH exposure, and because IR is linked with inflammation tightly, this inflammatory situation may implicate an IR status.MethodsWe developed an IH 3T3-L1 adipocyte and rat model respectively, recapitulating the nocturnal oxygen profile in OSA. In IH cells, nuclear factor kappa B (NF-κB) DNA binding reactions, hypoxia-inducible factor-1α (HIF-1α), glucose transporter-1 (Glut-1), necrosis factor alpha (TNF-α), interleukin (IL) -6, leptin, adiponectin mRNA transcriptional activities and protein expressions were measured. In IH rats, blood glucose, insulin, TNF-α, IL-6, leptin and adiponectin levels were analyzed.ResultsThe insulin and blood glucose levels in rats and NF-κB DNA binding activities in cells had significantly statistical results described as severe IH>moderate IH>mild IH>sustained hypoxia>control. The mRNA and protein levels of HIF-1α and Glut-1 in severe IH group were the highest. In cellular and animal models, both the mRNA and protein levels of TNF-α, IL-6 and leptin were the highest in severe IH group, when the lowest in severe IH group for adiponectin.ConclusionsOxidative stress and the release of pro-inflammatory cytokines/adipokines, which are the systemic inflammatory markers, are associated with IH closely and are proportional to the severity of IH. Because IR and glucose intolerance are linked with inflammation tightly, our results may implicate the clinical relationships between OSA and IR.
Highlights
Obstructive sleep apnea (OSA) is a common condition characterized by repeated episodes of upper airway obstruction which result in interruptions of breathing during sleep, recurring episodes of hypoxemia, sleep fragmentation, and daytime sleepiness
The insulin and blood glucose levels in rats and nuclear factor kappa B (NF-kB) DNA binding activities in cells had significantly statistical results described as severe intermittent hypoxia (IH).moderate IH.mild IH.sustained hypoxia.control
Because insulin resistance (IR) and glucose intolerance are linked with inflammation tightly, our results may implicate the clinical relationships between OSA and IR
Summary
Obstructive sleep apnea (OSA) is a common condition characterized by repeated episodes of upper airway obstruction which result in interruptions of breathing during sleep, recurring episodes of hypoxemia, sleep fragmentation, and daytime sleepiness. Growing evidence from cellular, tissular and animal models of OSA shows that intermittent hypoxia (IH), resulted from recurring episodes of upper airway obstruction, the hallmark feature and the most important pathophysiologic pathway of OSA, is believed to be the most important factor causing systemic inflammation [11,12] which may play the key role in the development and progression of metabolic dysfunction [13,14,15,16,17]. Potential mechanisms may include hypoxia per se, sympathetic activation, and resultant systemic inflammation, involving the activation of inhibitory kappa
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