Researchers in the US who explored two ways of extending longevity, dietary restriction and reduced Insulin/IGF-1 signalling, found they had very different effects on memory, and suggest their findings offer scientists a new model, based on the nematode C. elegans, for exploring ways to treat age-related memory decline.

A paper on the study by researchers at Princeton University in New Jersey was published online in the open access journal PLoS Biology on 18 May.

One of the most devastating aspects of aging is memory loss, and while scientists have explored ways to extend life, with many studies using the nematode C. elegans (a type of roundworm) as a model, we know little about how they affect learning and memory.

For this study, the researchers designed new tests (“chemotaxis assays”) of learning and memory in C. elegans to identify components of associative learning, associative short-term and associative long-term memory and found that the molecules required for these functions appear to be conserved from this nematode to mammals, implying that the biology of learning and memory is an ancient one.

The researchers also examined how the components declined with age and tested the effect of two longevity treatments, dietary restriction and reduced Insulin/IGF-1 signalling, on them.

They were surprised when they found that:

  • Dietary restriction impaired memory in early adulthood, but preserved memory with age,

  • Whereas reduced Insulin/IGF-1 signalling improved memory performance in early adulthood but failed to preserve it with age.

They concluded these results suggest that while longevity treatments may help preserve cognitive function with age, they may have distinctly different effects:

“… specific longevity treatments have acute and long-term effects on cognitive functions that decline with age through their regulation of rate-limiting genes required for learning and memory,” wrote the researchers.

The researchers were also pleased that this study suggests C. elegans is useful not only for studying longevity but memory as well.

Coleen Murphy, who heads the lab where the experiments took place, told the media that they hope to use the nematode model to find new drugs and treatments for age-related cognitive decline.

“Maybe targeting more than one longevity pathway would be the right approach,” she said.

“Insulin Signaling and Dietary Restriction Differentially Influence the Decline of Learning and Memory with Age.”
Kauffman AL, Ashraf JM, Corces-Zimmerman MR, Landis JN, Murphy CT
PLoS Biol, 8(5): e1000372; published online 18 May 2010.
DOI:10.1371/journal.pbio.1000372

Source:Public Library of Science.

Written by: Catharine Paddock, PhD