The mysterious relationship between reproduction and longevity.

A negative correlation between fertility and longevity has been documented in many species under a variety of conditions, but the association is not always observed,(1) leading to heated discussion about the nature of the reproduction-longevity relationship.(2) This debate is further fueled by the fact that no genes or molecules have been clearly shown to link the 2 traits. A recent study by Thondamal et al., in the nematode C. elegans has identified one potential link. The authors showed that the steroid signaling pathway, which regulates reproduction, is activated in response to dietary restriction (DR) and is in fact required for DR-induced lifespan extension.(3) Steroid signaling mutants subjected to DR not only failed to undergo lifespan extension but also exhibited altered germline plasticity. Interestingly, the requirement for steroid signaling was bypassed when germline plasticity was restored, suggesting that the DR response is mediated, at least in part, by signals from the germline. In this commentary, I discuss the implications of these findings. Several theories of aging have proposed the existence of an energetic trade-off between reproduction and lifespan,(4,5) but mechanistic details are lacking. I propose that revisiting and dissecting at the molecular level the link between reproduction, nutrition, and lifespan, will lead to a better understanding of the aging process and its connection to reproduction.