Wild worms respond positively to CR

A longstanding controversy about the benefits of calorie restriction (CR) involves a concern about the experimental animals used in CR studies: Most of them have been bred in the lab for generations, potentially resulting in substantial genetic changes, and they may not be particularly good representatives of their wild counterparts.

Mice, for example, have been bred for a century to select for fast and fecund reproduction. Studies by Steven Austad, one of the world’s leading experts on mouse longevity, have suggested that wild-caught mice don’t experience longevity benefits from CR.

The situation may be different in the nematode C. elegans, grand-hermaphrodite of the genetic study of aging and a key model in the analysis of CR’s role in longevity. Sutphin and Kaeberlein report that wild-derived strains of C. elegans as well as field-caught isolates of a related nematode species all benefit to some extent from CR:

Dietary restriction by bacterial deprivation increases life span in wild-derived nematodes.

Dietary restriction is known to promote longevity in a variety of eukaryotic organisms. Most studies of dietary restriction have been performed on animals bred for many generations under conditions that differ substantially from their natural environment, raising the possibility that some apparent beneficial effects of dietary restriction are due to adaptation to laboratory conditions. To address this question in an invertebrate model, we determined the effect of dietary restriction by bacterial deprivation on life span in five different wild-derived Caenorhabditis elegans strains and two strains of the related species Caenorhabditis remanei. Longevity was enhanced in each of the wild-derived C. elegans strains, in most cases to a degree similar to that observed in N2, the standard laboratory strain. Both strains of C. remanei were substantially longer lived any of the C. elegans isolates, produced larger brood sizes, and retained the ability to produce offspring for a longer period of time. Dietary restriction failed to increase mean life span in one C. remanei isolate, but significantly increased the maximum life span of both C. remanei strains. Thus, we find no evidence that adaptation to laboratory conditions has significantly altered the aging process in C. elegans under either standard or food-restricted conditions.

This paper demonstrates fairly conclusively that N2, the lab strain of C. elegans, isn’t unusual in its response to CR, and is therefore a good model for the study of the phenomenon in “true wild-type” worms. The question that remains, however, is whether C. elegans are a good model for a phenomenon that actually occurs in true wild-type mammals, like Steve Austad’s mice…or us.