Objective Short Sleep Duration is Related to the Peripheral Inflammasome Dysregulation in Patients with Chronic Insomnia

Objective: Insomnia with objective short sleep duration (IOSSD) is associated with an increased risk of cardiovascular morbidity, diabetes, neurocognitive impairment, and mortality. Inflammation is believed to be one of the main links between IOSSD and these diseases. The role of nucleotide-binding domain and leucine-rich repeat protein-3 (NLRP3) inflammasome in inducing activation of inflammatory signaling in IOSSD is not clear. In this study, we investigated the expression of NLRP3 inflammasome in patients with IOSSD to clarify this issue. Methods: Thirty-six patients with insomnia and 20 age- and sex-matched healthy controls were sequentially recruited. Subjects were categorized into three groups: IOSSD (sleep duration < 6h, n=20), insomnia with objective normal sleep duration (IONSD, sleep duration [greater than or equal to] 6h, n=16) and healthy controls (n=20). Objective sleep parameters were measured by overnight polysomnography. Peripheral NLRP3 inflammasome protein levels [NLRP3, apoptosis-associated speck-like protein containing a CARD (ASC), caspase 1] and cytokines [interleukin (TL)-l[beta] and IL-18] were assessed by Western blotting and ELISA, respectively. Results: IOSSD group showed significantly increased protein expressions of ASC and caspase-1 compared to IONSD and healthy controls and significantly increased IL-18 levels compared to healthy controls. On correlation analysis, total sleep time showed an inverse correlation with NLRP3, ASC, IL-18, and IL-1[beta] levels. Wake after sleep onset (WASO) showed a positive correlation with NLRP3, ASC, caspase-1, and IL-1[beta] levels. N3 sleep ratio showed a significant negative correlation with NLRP3, ASC, and IL-18 levels. Conclusion: The current study demonstrated upregulation of NLRP3 inflammasome in IOSSD. Short sleep duration, decreased slow wave sleep, and sleep fragmentation may contribute to dysregulation of NLRP3 inflammasome. Keywords: insomnia, short sleep duration, polysomnography, fragmentation, inflammation, NLRP3