Introduction: Metabolism, Life History and Aging

Abstract

To an ecologist or evolutionary biologist the notion that the evolution of life history may play an integral role in shaping organismal physiology is elementary; so too the idea that adoption of one life-history strategy over another can have far-reaching effects in terms of aging and life span. For most biomedical researchers, however, this is not so clear. Outside of what they may have gleaned from an introductory ecology course, there is little opportunity (or incentive) for a prototypical biomedical scientist to learn about life-history evolution; rather biomedical scientists are highly proficient in cutting-edge methods in molecular and cellular biology, and ‘‘typical’’ biogerontological research focuses on processes such as cellular senescence using immortalized cell lines or the role of specific signaling pathways via the generation of transgenic animal models. Rarely does it involve the study of free-living organisms under natural conditions. On the other hand, most organismal biologists often fail to appreciate exactly how much their model system has to offer research on aging or to modern biomedical science in general. Using essentially the same starting material, Mother Nature has provided us with a virtual smorgasbord of species with profound differences in numerous traits including life span. What is even more remarkable is that despite the highly conserved organization and function of tissues/organs among species, the rate at which they deteriorate is markedly different even within closely related species. For example, a process that takes a few years in mice or Japanese quail will take decades in humans or parrots, respectively. If one considers higher-level taxonomic groupings, the magnitude of these differences is considerably greater. For example, mouse-sized birds routinely live 5–10 times longer than their mammalian counterparts, while among all the vertebrates life span can vary by as much as 100-fold or more (Holmes and Martin 2009; Austad 2010). Currently, the great unknown lies with the identification of key cellular and molecular attributes that contribute to this differential longevity among species, and even more importantly, it remains to be seen whether or not these mechanisms are altered in a manner that is consistent with the change in species’ life spans. Differences in metabolism and its consequences in terms of oxidative stress, a major theme of this symposium, represents just one of many potentially informative applications of the comparative approach to address questions in experimental biogerontology (see Austad, this issue). Utilizing ‘‘nontraditional’’ animal models in modern biogerontological research—meaning species other than the nematode worm Caenorhabditis elegans, the fruit fly Drosophila melanogaster, and inbred laboratory mouse stocks–has much to offer (Harper 2008; Austad 2010; Miller et al., in press). Unfortunately, despite pleas to the contrary there remains a general lack of enthusiasm to using the comparative approach within biomedical circles. It is largely for this reason that I felt compelled to organize a symposium whose main goal was to bring together individual scientists that are proficient in either the field or at the bench (or both) to discuss the impact of the evolution of life history on metabolism and aging in the unique setting of a meeting about comparative biology. Ultimately, my hope was that this symposium would do much to bridge the gap between laboratory-based and field-based models Integrative and Comparative Biology, volume 50, number 5, pp. 778–782 doi:10.1093/icb/icq136