From the Fountain of Youth and Shangri-La, to plastic surgery and cryogenic freezing, humans have long been obsessed with circumventing the natural process of ageing. At the cellular level, ageing occurs as the protective DNA at the ends of chromosomes – called telomeres – gets shorter with each round of cell division. Telomeres act as physical shields to keep the important coding regions of DNA safe from unnecessary intervention by the enzymes that repair damaged DNA. Eventually, telomeres become too short to offer any protection, causing DNA integrity to decline and ultimately cell function to fail. Interestingly, a recent study from the laboratory of Pat Monaghan at the University of Glasgow, UK, showed that telomere length at early life stages can accurately predict future longevity in zebra finches. In a follow-up study just published in the Proceedings of the Royal Society B, a team from Monaghan's group – lead by post-docs Katherine Herborn and Britt Heidinger – tested whether early life stress enhances telomere loss. If so, this could explain why adverse early life experiences often lead to accelerated ageing – a phenomenon observed in many vertebrates that remains poorly understood.
The team headed out to the field to study a wild population of nesting European shags. They selected about 50 nests from the breeding colony of birds and stealthily monitored them to determine when individual chicks hatched. Ten days after the chicks hatched, the researchers moved in to obtain a blood sample from each one in the nest, and then they assigned the nest to one of three treatment groups. Shag chicks in nests from the control group were left undisturbed after the initial sampling, while chicks in the experimental groups were handled daily in order to administer an oral dose of corticosterone (the principal stress hormone in birds) dissolved in oil, or simply oil alone. The researchers knew that the handling/dosing procedure itself is an acute stresssor and causes a transient increase in plasma corticosterone, but they included a corticosterone-supplemented group to ensure that continual daily increases in this hormone occurred even when the chicks became accustomed to handling over the course of the experiment. For the next 20 days, the researchers handled and dosed the chicks in the experimental groups every day, but were careful not to disturb the chicks in the control nests. On the last day of the experiment, the researchers obtained a final blood sample from all of the chicks before waving ‘bye-bye’ to the birdies and heading back to the lab.
Back in Glasgow, the researchers processed the blood samples in order to measure plasma corticosterone levels and telomere length of red blood cell DNA. The initial pre-treatment corticosterone levels and telomere lengths were similar in all chicks, meaning they all started on a level playing field. However, when the team measured telomere lengths from red blood cell DNA collected on the last day of the experiment, they discovered that chicks that were handled for 20 days on a daily basis – regardless of the contents of their oral dose – had significantly shorter telomeres compared with undisturbed chicks. This means that an acute stressor, such as brief handling, experienced early in post-natal life can accelerate the loss of telomere length and ultimately impact the individual's longevity. So, the secret to a long life is a peaceful childhood! (Excuse me while I go enroll my kids in a yoga class…)