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Proof-of-principle demonstration of endogenous circadian system and circadian misalignment effects on human oral microbiota.

ABSTRACT: Circadian misalignment-the misalignment between the central circadian "clock" and behavioral and environmental cycles (including sleep/wake, fasting/eating, dark/light)-results in adverse cardiovascular and metabolic effects. Potential underlying mechanisms for these adverse effects include alterations in the orogastrointestinal microbiota. However, it remains unknown whether human oral microbiota has endogenous circadian rhythms (i.e., independent of sleep/wake, fasting/eating, and dark/light cycles) and whether circadian misalignment influences oral microbiota community composition. Healthy young individuals [27.3 ± 2.3 years (18-35 years), 4 men and 2 women, body-mass index range: 18-28 kg/m² ] were enrolled in a stringently controlled 14-day circadian laboratory protocol. This included a 32-h constant routine (CR) protocol (endogenous circadian baseline assessment), a forced desynchrony protocol with four 28-h "days" under ~3 lx to induce circadian misalignment, and a post-misalignment 40-h CR protocol. Microbiota assessments were performed on saliva samples collected every 4 h throughout both CR protocols. Total DNA was extracted and processed using high-throughput 16S ribosomal RNA gene amplicon sequencing. The relative abundance of specific oral microbiota populations, i.e., one of the five dominant phyla, and three of the fourteen dominant genera, exhibited significant endogenous circadian rhythms. Importantly, circadian misalignment dramatically altered the oral microbiota landscape, such that four of the five dominant phyla and eight of the fourteen dominant genera exhibited significant circadian misalignment effects. Moreover, circadian misalignment significantly affected the metagenome functional content of oral microbiota (inferred gene content analysis), as indicated by changes in specific functional pathways associated with metabolic control and immunity. Collectively, our proof-of-concept study provides evidence for endogenous circadian rhythms in human oral microbiota and show that even relatively short-term experimental circadian misalignment can dramatically affect microbiota community composition and functional pathways involved in metabolism and immune function. These proof-of-principle findings have translational relevance to individuals typically exposed to circadian misalignment, including night shift workers and frequent flyers.

SUBMITTER: Chellappa SL

PROVIDER: S-EPMC8938955 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Project description:BackgroundCircadian system contributes to the regulation of inflammatory processes, but the role of circadian misalignment as a risk factor for contracting Covid-19 has up to now been poorly studied. The aim of this study was to explore the relationship between circadian misalignment (chronic disturbance of the circadian system) and the risk of Covid-19 infection in a population of subjects suspected of contact or infection with SARS-CoV-2.MethodsCross-sectional single-center study conducted during a period without lockdown in winter 2021. Recruitment took place in a Covid-19 outpatient testing center. Subjects between 18 and 45 years old were included whether they were symptomatic or not, healthcare workers or not, in contact with a Covid-19 case or not. To determine social jetlag, a proxy of circadian misalignment, they were asked about their usual sleep-wake behaviors. Usual sleep duration and sleep-wake timing were explored on workdays and free days. Social jetlag was defined as at least 2 h shift of circadian alignment (defined as the difference between mid-sleep on workdays and mid-sleep on free days, mid-sleep as the median between bedtime and rise time).ResultsOne thousand fourteen subjects were included (sampling rate: 10.8%, 39% men, mean age 28 ± 8) with 56 subjects positive for Covid-19 (positivity rate: 5.5%). Usual mean sleep duration was equivalent in both groups (7h47 versus 7h49, p = 0.733). Social jetlag greater than 2 h comprised 33.3% of subjects in the Covid-19 group versus 20.6% in the control group (p = 0.026). After adjustment on age, gender, BMI and work schedules, subjects presenting with social jetlag greater than 2 h had a 2.07-fold higher likelihood to test positive than subjects who had identical sleep-wake timing on workdays and free days (OR = 2.07, 95%CI = [1.12-3.80], p = 0.024).ConclusionCircadian misalignment not only is present in subjects infected by Covid-19 but could also be responsible for a higher likelihood of being infected. The chronobiological impact on the immune system or a higher likelihood of being exposed to social contacts during nocturnal activities could explain our findings, which need to be confirmed in a future large cohort study. Regular sleep-wake timing could ultimately become a target for preventing Covid-19 infection.

Project description:BackgroundPhysiological circadian rhythms (CRs) are complex processes with 24-hour oscillations that regulate diverse biological functions. Chronic weekly light/dark (LD) shifting (CR disruption; CRD) in mice results in colonic hyperpermeability. However, the mechanisms behind this phenomenon are incompletely understood. One potential innovative in vitro method to study colonic CRs are colon organoids. The goals of this study were to utilize circadian clock gene Per2 luciferase reporter (Per2::Luc) mice to measure the effects of chronic LD shifting on colonic tissue circadian rhythmicity ex vivo and to determine if organoids made from shifted mice colons recapitulate the in vivo phenotype.MethodsNon-shifted (NS) and shifted (S) BL6 Per2::Luc mice were compared after a 22-week experiment. NS mice had a standard 12h light/12h dark LD cycle throughout. S mice alternated 12h LD patterns weekly, with light from 6am-6pm one week followed by shifting light to 6pm-6am the next week for 22 weeks. Mice were tested for intestinal permeability while colon tissue and organoids were examined for CRs of bioluminescence and proteins of barrier function and cell fate.ResultsThere was no absolute difference in NS vs. S 24h circadian period or phase. However, chronic LD shifting caused Per2::Luc S mice colon tissue to exhibit significantly greater variability in both the period and phase of Per2::Luc rhythms than NS mice colon tissue and organoids. Chronic LD shifting also resulted in increased colonic permeability of the Per2::Luc mice as well as decreased protein markers of intestinal permeability in colonic tissue and organoids from shifted Per2:Luc mice.ConclusionsOur studies support a model in which chronic central circadian disruption by LD shifting alters the circadian phenotype of the colon tissue and results in colon leakiness and loss of colonic barrier function. These CRD-related changes are stably expressed in colon stem cell derived organoids from CRD mice.

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Proof-of-principle demonstration of endogenous circadian system and circadian misalignment effects on human oral microbiota.

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