Grey mouse lemurs on calorie restricted diets live longer, study suggests
Cutting calories linked to longer lifespans, but also slightly less grey matter in the brain
Several studies have suggested that long-term calorie restriction can extend lifespan and slow age-related chronic diseases in a variety of animals in the lab, including rats,mice, fish and worms.
Now, French researchers conducting a 10-year experiment have recorded a significant increase in the lifespan of grey mouse lemurs that had their calorie intake moderately reduced, starting in early adulthood.
They began the study in 2006, giving one group of 15 males a "standard" daily diet. Nineteen other males were fed the same food, with 30 per cent fewer calories.
Researchers at the National Centre for Scientific Reserch and the French National Museum of Natural History, worked in partnership with other French teams to study the animals' longevity, age-related pathologies, cognitive abilities, motor skills and brain matter atrophy.
By the end of the study, all 15 mouse lemurs on the standard balanced diet had died, while seven that were on calorie-restricted diets were still alive.
The grey mouse lemur has a median survival in captivity of 5.7 years for males, and a maximum lifespan of 12 years.
Researchers found the calorie-restricted lemurs lived to 9.6 years on average, compared to 6.4 years for those on the standard diet.
"Caloric restriction had a strong positive effect on mouse lemur lifespan," the research team said in a paper published Thursday in the journal Communications Biology.
Compared to the control animals, moderate calorie restriction extended lifespan by 50 per cent, compared to their non-dieting peers, and reduced aging-associated diseases, the study found.
In addition, the researchers noticed the preservation of motor capacities in the calorie restricted group, without any alteration to cognitive performance, and a reduction in the incidence of pathologies usually associated with aging, such as cancer and diabetes.
Effect on brain's grey and white matter
Calorie restriction accelerated the loss of the grey matter in the lemurs' brains — neuronal cell bodies that processes motor function, language and problem-solving. However, the researchers could find no change in cognition or motor skills and said brain imaging data showed only a "slight loss" of grey matter in the oldest of the lemurs on restricted diets.
On the other hand, caloric restriction slowed the loss of white matter, the neuronal fibres through which messages pass between different areas of the brain.
The researchers were not able to explain the effects.
The grey matter images show "a potential negative impact of caloric restriction on brain integrity that deserves more investigation," the team said.
More whitening of the fur
Included in the summary of the paper were photos of two nine-year-old grey mouse lemurs under observation.
The lemur on a "normal" balanced diet throughout its life had cataracts and widespread whitening of the fur, commonly seen in elderly mouse lemurs, while the second lemur living on fewer calories had the appearance of a younger animal, with clear eyes and a lot less white in its fur.
Research into a link between calorie restriction and living longer has a long history.
In the 1930s, researchers found that lab rats and mice lived up to 40 per cent longer when fed a calorie-restricted diet.
Whether or not calorie restriction will extend lifespan in humans is not yet known, although it has been shown to lower cholesterol and blood pressure and reduce metabolic risk factors associated with cell damage and cancer.