Effects of age on thermoregulatory responses during cold exposure in a nonhuman primate, Microcebus murinus.

Jérémy Terrien (1) , Philippe Zizzari (2) , Marie-Thérèse Bluet-Pajot (2) , Pierre-Yves Henry (1) , Martine Perret (1) , Jacques Epelbaum (2) , Fabienne Aujard (1)

1 MAOAC - Mécanismes adaptatifs : des organismes aux communautés
2 Neurobiologie de la Croissance et de la Senescence

Cold resistance appears altered with aging. Among existing hypotheses, the impaired capacity in response to cold could be related to an altered regulation of plasma IGF-1 concentration. The combined effects of age and cold exposure were studied in a short-living primate, the gray mouse lemur (Microcebus murinus), which adjusts its energy balance using a daily torpor phase, to avoid high energy cost of normothermia maintenance. Changes in body mass, core temperature, locomotor activity, and caloric intake were monitored under 9-day exposures to 25 degrees C and 12 degrees C in captive animals in winter conditions. Short-term (after 2 days) and long-term (after 9 days) cold-induced changes in IGF-1 levels were also evaluated. In thermoneutral conditions (25 degrees C), general characteristics of the daily rhythm of core temperature were preserved with age. At 12 degrees C, age-related changes were mainly characterized by a deeper hypothermia and an increased frequency of torpor phases, associated with a loss of body mass. A short-term cold-induced decrease in plasma IGF-1 levels was observed. IGF-1 levels returned to basal values after 9 days of cold exposure. No significant effect of age could be evidenced on IGF-1 response. However, IGF-1 levels of cold-exposed aged animals were negatively correlated with the frequency of daily torpor. Responses exhibited by aged mouse lemurs exposed to cold revealed difficulties in the maintenance of normothermia and energy balance and might involve modulations of IGF-1 levels.

Keywords: autonomic thermoregulation; cold exposure; insulin-like growth factor; aging; Microcebus murinus; autonomic thermoregulation

Domains: Life Sciences [q-bio]; Human health and pathology; Endocrinology and metabolism

Jérémy Terrien, Philippe Zizzari, Marie-Thérèse Bluet-Pajot, Pierre-Yves Henry, Martine Perret, et al.. Effects of age on thermoregulatory responses during cold exposure in a nonhuman primate, Microcebus murinus.. AJP - Regulatory, Integrative and Comparative Physiology, 2008, 295 (2), pp.R696-703. ⟨10.1152/ajpregu.00629.2007⟩. ⟨hal-00426197⟩