How low-cal diets lengthen life

Scientists are uncovering the secrets of using low-calorie diets to increase lifespan.

The team, from the Max Planck Institute for Biology of Ageing in Cologne, Germany, say a reduced caloric intake increases life expectancy in many species, including fruit flies and roundworms – but the underlying mechanisms are a mystery.

Now they have tested roundworms and found that a hormone receptor plays a vital role.

Roundworms are ideal for researching lifespan, as they live only about 20 days. They also have fewer than a thousand cells, and their genes have similarities to those in humans and are well-understood. The researchers focused on hormone receptors in the cell nucleus which regulate genes for metabolism.

They showed that when calorie intake is reduced, the receptor protein NHR-62 works to increase the roundworms’ lifespan by 20%. When NHR-62 is inactive, dietary restriction does not increase lifespan.

Another hormone receptor, called NHR-8, was also shown to affect maturation and lifespan of the worms, so other receptors linked to these may be responsible for regulating life expectancy in humans.

Team leader, Professor Adam Antebi, said: "It seems that there is an as yet unknown hormone which regulates lifespan using NHR-62. If we can identify this hormone and administer it to the worm, we may prolong its life without having to change its calorie intake."

Full details appear in the journals PLoS Genetics and Cell Metabolism today (7 August).

The team adds that dietary restriction affects gene expression. Roundworms have about 20,000 worm genes, of which 3,000 change their activity. Of these, 600 are linked to the protein NHR-62. Hence, the team believes: "There are many other candidates for improving life expectancy."

Heestand, B.N. et al. Dietary Restriction Induced Longevity is Mediated by Nuclear Receptor NHR-62 in Caenorhabditis elegans. PLoS Genetics 7 August 2013 9(7): e1003651.

Magner, D. B. et al. The NHR-8 Nuclear Receptor Regulates Cholesterol and Bile Acid Homeostasis in C. elegans. Cell Metabolism 7 August 2013