Caloric restriction or resveratrol supplementation and ageing in a non-human primate: first-year outcome of the RESTRIKAL study in Microcebus murinus.

A life-long follow-up of physiological and behavioural functions was initiated in 38-month-old mouse lemurs (Microcebus murinus) to test whether caloric restriction (CR) or a potential mimetic compound, resveratrol (RSV), can delay the ageing process and the onset of age-related diseases. Based on their potential survival of 12 years, mouse lemurs were assigned to three different groups: a control (CTL) group fed ad libitum, a CR group fed 70% of the CTL caloric intake and a RSV group (200 mg/kg.day(-1)) fed ad libitum. Since this prosimian primate exhibits a marked annual rhythm in body mass gain during winter, animals were tested throughout the year to assess body composition, daily energy expenditure (DEE), resting metabolic rate (RMR), physical activity and hormonal levels. After 1 year, all mouse lemurs seemed in good health. CR animals showed a significantly decreased body mass compared with the other groups during long day period only. CR or RSV treatments did not affect body composition. CR induced a decrease in DEE without changes in RMR, whereas RSV induced a concomitant increase in DEE and RMR without any obvious modification of locomotor activity in both groups. Hormonal levels remained similar in each group. In summary, after 1 year of treatment CR and RSV induced differential metabolic responses but animals successfully acclimated to their imposed diets. The RESTRIKAL study can now be safely undertaken on a long-term basis to determine whether age-associated alterations in mouse lemurs are delayed with CR and if RSV can mimic these effects.

Behavioral thermoregulation in a non human primate: effects of age and photoperiod on temperature selection.

Deficits in autonomic thermoregulatory capacities have been identified in aged humans and animals, but little is known about the effect of aging on behavioral thermoregulation and the potential effect of season. Preferred ambient temperature (T(a)) in a thermal gradient (available T(a)s from 10 to 30 degrees C) was measured in the mouse lemur, a nocturnal Malagasy primate. Male mouse lemurs (40 adults and 40 aged) were studied under short (SP, resting season) and long photoperiod (LP, breeding season). Additionally, daily body temperature rhythm was telemetrically recorded in 30 individuals of both age categories. In adults exposed to SP, a choice for warm climates was observed, with a mean diurnal T(a) of 26 degrees C. Day-night differences in selected T(a) occurred only in animals exposed to SP. In LP, selection of a warm environment did not seem to be a necessary factor for maintenance of normothermia. Aged animals selected warmer T(a)s than adults during the night like during the day, whatever the photoperiod. In relation to changes in body temperature rhythm according to age, aged animals would select warmer environments possibly to compensate autonomic deficiencies. Further studies on age-related changes in hormonal and cellular functions involved in energy balance and thermoregulation will help decipher the causes of insufficient responses to thermal stress observed in the elderly.