Biology subjects

HOZER, C.

Publications and source records attributed to HOZER, C..

3 recordsLinked to original sources

bioRxiv2021

Relationships between endogenous circadian period, physiological and cognitive parameters and sex in aged non-human primates

The biological clock exhibits circadian rhythms, with an endogenous period tau close to 24h. The circadian resonance theory proposes that lifespan is reduced when endogenous period goes far from 24h. It has been suggested that daily resetting of the circadian clock to the 24h external photoperiod might induce marginal costs that would accumulate over time and forward accelerate aging and affect fitness. In this study, we aimed to evaluate the link between the endogenous period and biomarkers of aging in order to investigate the mechanisms of the circadian resonance theory. We studied 39 middle-aged and aged Microcebus murinus, a nocturnal non-human primate whose endogenous period is about 23.1h, measuring the endogenous period of locomotor activity, as well as several physiological and behavioral parameters (rhythm fragmentation and amplitude, energetic expenditure, oxidative stress, insulin-like growth factor-1 (IGF-1) concentrations and cognitive performances) in both males and females. We found that aged males with tau far from 24h displayed increased oxidative stress. We also demonstrated a positive correlation between tau and IGF-1 concentrations, as well as learning performances, in males and females. Together these results suggest that a great deviation of tau from 24h leads to increased biomarkers of age-related impairments. Summary StatementThis manuscript describes how the misalignment between the endogenous circadian period and the 24h of the environmental periodicity impacts aging biomarkers and accelerates cognitive decline.

physiology↗

bioRxiv2020

Adult survival is reduced when endogenous period deviates from 24h in a non-human primate (Microcebus murinus), depending on sex and season

SummaryCircadian rhythms are ubiquitous attributes across living organisms and allow the coordination of internal biological functions with optimal phases of the environment, suggesting a significant adaptive advantage. The endogenous period called tau lies close to 24h and is thought to be implicated in individuals’ fitness: according to the circadian resonance theory, fitness is reduced when tau gets far to 24h. In this study, we measured the endogenous period of 142 mouse lemurs (Microcebus. murinus), and analyzed how it affects their survival. We found different effects according to sex and season. No impact of tau on mortality was found in females. However, in males, the deviation of tau from 24h substantially increased mortality, particularly during the inactive season (winter). These results, comparable to other observations in mice or drosophila, show that captive gray mouse lemurs enjoy better fitness when their circadian period closely matches the environmental periodicity. In addition to their deep implications in health and aging research, these results raise further ecological and evolutionary issues regarding the relationships between fitness and circadian clock.Competing Interest StatementThe authors have declared no competing interest.View Full Text

physiology↗

bioRxiv2020

Physiological and cognitive consequences of a daily 26h photoperiod in a primate (M. murinus)

Daily resetting of the circadian clock to the 24h natural photoperiod might induce marginal costs that would accumulate over time and forward affect fitness. It was proposed as the circadian resonance theory by Pittendrigh in 1972. For the first time, we aimed to evaluate these physiological and cognitive costs that would partially explain the mechanisms of the circadian resonance hypothesis. We evaluated the potential costs of imposing a 26h photoperiodic regimen compared to the classical 24h entrainment measuring several physiological and cognitive parameters (body temperature, energetic expenditure, oxidative stress, cognitive performances). We found significant higher resting body temperature and energy expenditure and lower cognitive performances when the photoperiodic cycle length was 26h. Together these results suggest that a great deviation of external cycles from 24h leads to daily greater synchronization costs, and lower cognitive capacities. To our knowledge, this study is the first to highlight potential mechanisms of circadian resonance theory.

physiology↗