The practice of calorie restriction slows aging to a degree that scales with species life span. Short lived species exhibit a sizable gain in maximum life span, while long-lived species do not. In this paper, researchers report on a study of calorie restriction in grey mouse lemurs, one of our more distant and short-lived primate cousins. The effects are about as dramatic as those observed in mice, and the study is interesting on that point: lab mice normally reach 50% mortality due to aging after 2-3 years while the lemurs used here reach that point at 6-7 years, so one might have expected the lemurs to exhibit much smaller gains in life span as a result of calorie restriction. Nonetheless, by the end of the study, the longest surviving non-calorie-restricted lemurs had been dead for a year, while more than a third of the calorie restricted animals were still alive. Calorie restriction extended the 50% mortality age from 6-7 years to 9-10 years in this species, quite similar to the relative size of results in mice.
Caloric restriction, i.e., reducing calorie availability by ~20-50%, is one of the rare known strategies that can extend lifespan. In short-lived species such as rodents, caloric restriction can increase maximal lifespan up to 50% while improving general health and decreasing aging-associated diseases. Beneficial effects of caloric restriction on age-related diseases have also been reported for long-lived species, including rhesus monkeys.
Here we examine the effects of caloric restriction on the health and lifespan of the grey mouse lemur Microcebus murinus, a small lemurid primate with a median survival in captivity of 5.7 years for males and maximum lifespan of 12 years. Mouse lemurs are widely used models for human ageing. They display age-related alterations of their sensorial system, motor functions, biological rhythms, and immune and endocrine systems. In this species, aging leads to increased prevalence of diseases such as neoplasia or sarcopenia and glucoregulatory function alterations that also increase with aging in humans. Finally, their cerebral aging profile is similar to that of humans.
Because of their reduced lifespan (as compared to rhesus macaque), cohorts of calorie-restricted lemurs can be easily created to evaluate mechanisms leading to caloric restriction-related changes. Here we provide the first complete set of caloric restriction-related survival data for a non-human primate in association with a longitudinal follow-up of age-associated alterations in cognition and brain volumes.
In 2006, 34 captive adult male mouse lemurs (age 3.2 ± 0.1 years) were randomly assigned to either a control diet or a chronic 30% caloric restriction diet. Compared to control animals, caloric restriction extended lifespan by 50% (from 6.4 to 9.6 years, median survival), reduced aging-associated diseases and preserved loss of brain white matter in several brain regions. However, caloric restriction accelerated loss of grey matter throughout much of the cerebrum. Cognitive and behavioural performances were, however, not modulated by caloric restriction. Thus chronic moderate caloric restriction can extend lifespan and enhance health of a primate, but it affects brain grey matter integrity without affecting cognitive performances.