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Conference on 'Nutrition and healthy ageing'
Plenary Lecture 3
15-18 July 2013
The Nutrition Society Annual Summer Meeting
Newcastle University
Lifespan, survival ability and phenotypic plasticity
Lifespan, and the underlying processes of ageing, are tremendously variable among species, populations and among individuals within populations(1-5). For example, some tree species live thousands of years and some tortoises of the order of 150 years, whereas on the more short-lived end of the spectrum we have species such as fruit flies, which live on average 40-50 d, and some mayflies which only live for about 30 min(1-5). We know that much of this variation, even among individuals within a single population, is ultimately due to genetic differences. Consequently, most of the work on the mechanisms of ageing has focused on the genetic factors that influence longevity in yeast, nematode worms, fruit flies, mice and even human subjects, resulting in the identification of hundreds of genes that influence lifespan and ageing(6,7). In particular, this research programme has led to the discovery of genes that have evolutionarily conserved effects on lifespan and ageing, for example in the i nsulin/i nsulin-like growth factor signalling pathway(6,7). However, this focus on genetic factors distracts from the important but often neglected fact that ageing and lifespan can also be strongly influenced and modified by environmental factors(1,2,4-6). Importantly, such environmental effects can interact with genetic determinants to affect ageing and lifespan in ways that cannot be understood from considering the genetic (or environmental) factors alone.
Indeed, in many organisms survival and lifespan react highly sensitively (plastically) to changes in the environment, for example to changes in diet, temperature etc.(1,2,4-6,8). In small poikilotherms such as insects, for instance, reduced temperature tends to increase lifespan within the range of sustainable temperatures(9,10). Such phenotypic responses of lifespan (or, more generally, of somatic maintenance and survival ability) to environmental changes are specific examples of a more general phenomenon which evolutionary...