Shortened Seasonal Photoperiodic Cycles Accelerate Aging of the Diurnal and Circadian Locomotor Activity Rhythms in a Primate

Abstract

The gray mouse lemur (Microcebus murinus), a prosimian primate, exhibits seasonal rhythms strictly controlled by photoperiodic variations. Previous studies indicated that longevity can be altered by long-term acceleration of seasonal rhythms, providing a model for assessing various aspects of aging. To assess the effect of aging and accelerated aging on the circadian system of this primate, we compared the circadian rhythm of the locomotor activity in adult mouse lemurs (2-4.5 years, n = 9), aged mouse lemurs (5-9 years, n = 10), and adult mouse lemurs that had been exposed from birth to a shortened seasonal photoperiodic cycle (2-4.5 years, n = 7). Compared to adult animals, aged mouse lemurs showed a significant increase in intradaily variability and an advanced activity onset. Aging was characterized by a decrease in amplitude, with both a decrease in nocturnal activity and an increase in daytime activity. When maintained in constant dim red light, aged animals exhibited a shortening of the free-running period (22.8 +/- 0.1 h) compared to adult animals (23.5 +/- 0.1 h). A 3- to 5-year exposure to an accelerated seasonal photoperiodic rhythm ("annual" duration of 5 months) in accelerated mouse lemurs produced disturbances of the locomotor activity rhythm that resembled those of aged mouse lemurs, whether animals were studied in entrained or in free-running conditions. The present study demonstrated a weakened and fragmented locomotor activity rhythm during normal aging in this primate. Increasing the number of expressed seasonal cycles accelerated aging of parameters related to circadian rhythmicity in adult animals.

Attenuated effect of increased daylength on activity rhythm in the old mouse lemur, a non-human primate

“…Moreover, a recent study demonstrated that thermoregulation differed according to photoperiod and age in this species , see comments in (Van Someren, 2007). Several of these studies indicate that daily and seasonal biological rhythms are altered in old mouse lemurs in ways that are remarkably similar to what is observed in human aging (Huang et al, 2002;Cayetanot et al, 2005): a decrease in amplitude of the locomotor activity level, an increased activity during the resting diurnal phase and an increase in fragmentation. For these and other reasons, the mouse lemur can be regarded as a model of primary importance for human aging (Bons et al, 2006).…”

Vieillissement et rythmes biologiques chez les primates

“…Chez le microcèbe âgé (âge > 5 ans), l'activité locomotrice, strictement nocturne chez l'adulte, survient en avance de phase, se fragmente et des séquences d'activité sont présen-tes pendant le repos diurne (Figure 3). La resynchronisation des rythmes journaliers lors d'avance ou de retard de phase est également modifiée [13]. En outre, les résultats révèlent un dysfonctionnement des répon-ses à l'entraînement photopériodique, phénomène rarement mentionné dans les études sur le vieillissement des rythmes d'activité.…”

A review on ocular findings in mouse lemurs: potential links to age and genetic background

“…Their maximum life expectancy of about 8 years in the wild and up to 18.5 years in captivity (Weigl and Jones, 2005) is much shorter than for other nonhuman primates (Weigl and Jones, 2005;Zimmermann and Radespiel, 2015). Consequently, mouse lemurs represent an important animal model for aging (Perret, 1997;Cayetanot et al, 2005;Languille et al, 2012;Zimmermann and Radespiel, 2014;Zimmermann et al, 2016) and biomedical research, e.g. on Alzheimer's disease (Austad and Fischer, 2011;Verdier et al, 2015).…”