Abstract
The effects of stress exposure are likely to vary depending on life-stage and stressor. While it has been postulated that mild stress exposure may have beneficial effects, the duration of such effects and the underlying mechanisms are unclear. While the long-term effects of early-life stress are relatively well studied, we know much less about the effects of exposure in adulthood since the early- and adult-life environments are often similar. We previously reported that repeated experimental exposure to a relatively mild stressor in female zebra finches, first experienced in young adulthood, initially had no effect on mortality risk, reduced mortality in middle age, but the apparently beneficial effects disappeared in old age. We show here that this is underpinned by differences between the control and stress-exposed group in the pattern of telomere change, with stress-exposed birds showing reduced telomere loss in middle adulthood. We thereby provide novel experimental evidence that telomere dynamics play a key role linking stress resilience and aging.
Highlights
Exposure to challenging environmental circumstances can accelerate the rate of aging and increase the likelihood of disease and thereby mortality risk
While exposure to severe and/ or chronic stress is generally detrimental, relatively milder forms of stress exposure can, in some circumstances, have positive rather than negative effects on aging and lifespan.1-4 A substantial body of evidence across a range of taxa, including humans, shows that stress exposure during early life can alter coping abilities and have long-term phenotypic consequences, the fitness effects of which can be contingent on the adult environment.5-7 Surprisingly, we know much less about variation in outcomes that results from environmentally generated stress exposure during different periods of adult life and how changes in stress resistance with increasing adult age might interact with the potentially beneficial effects of mild stress exposure.[3,8]
In an experimental study in female zebra finches (Taeniopygia guttata) on the influence of persistently challenging environmental circumstances in adulthood on mortality risk, we found that effects on mortality risk varied at different stages of adult life; no initial effect of the challenging environment was observed during relatively young adulthood (5-1 3 months), a reduced mortality risk observed during middle age (13-36 months), and no effect in old age (36-48 months).[25,26]
Summary
Exposure to challenging environmental circumstances can accelerate the rate of aging and increase the likelihood of disease and thereby mortality risk. Telomeres comprise tandem repeats of a short DNA sequence (commonly TTAGGG), plus associated proteins found at the end of the linear chromosomes of eukaryotes They play a key role in genome integrity and cell stability, protecting genes from the loss of coding sequences that occurs at the chromosome ends during cell division and preventing end-to-end joining of chromosomes by the DNA repair machinery.9-11 Telomeres shorten with progressing age within somatic tissues of many species, and this shortening is a recognized hallmark of aging (recently reviewed by Ref. 12), since individuals with shorter telomeres, or with higher rates of telomere erosion, often have shorter lifespans13-15 and show greater susceptibility to infection and disease.16-18. We predicted that, if this was so, exposure to the persistently challenging conditions would have no effect on telomere shortening in early or old adulthood in comparison with control groups but would reduce telomere shortening in middle age
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
