For optimal survival, an animal has to process complex environmental information to generate the appropriate physiological responses. An interesting demonstration of this sensory influence on physiology is the observation that subsets of gustatory and olfactory neurons can either shorten or lengthen the lifespan of the nematode C. elegans, responses that are also present in the fruit fly Drosophila.
Accordingly, the nature of these neurons suggests that some of the cues that affect lifespan are food-derived and that perception of these cues alone can exert different effects on lifespan. Consistent with this idea, we have recently found that the sensory system influences lifespan through food-type recognition, which is distinct from food-level restriction, also more commonly known as calorie restriction. In addition, we have shown that the sensory influence on lifespan via food-type recognition involves the activities of specific neuropeptide signaling pathways under particular environmental conditions.
Sensory neurons affect lifespan presumably by promoting physiological changes that alter organismal homeostasis, which is also known to be modulated by neuropeptide signaling. Besides the neuropeptide neuromedin U pathway that processes food-type information that alters C. elegans lifespan, other neuropeptides that affect physiology and lifespan include the many insulin-like peptides (ILPs) of C. elegans and Drosophila. Indeed, our recent data suggest the existence of a C. elegans ILP code that regulates distinct developmental switches, which can lead to physiological state(s) that affect lifespan. In the future, we aim to determine the molecular and cellular bases through which these different neuropeptides process sensory information and promote physiological changes, such as developmental or lifespan changes. Thus, considering that age and environment are significant risk factors in many diseases, our studies should yield insight into mechanisms of many age-related diseases.