Born to be young? Prenatal thyroid hormones influence the “biological age” at birth

The environment provided by the mother during the development of the embryo has important consequences on health and life span in old age. This may result from the effects on cellular aging which is often estimated with telomere length. Telomeres are the protective caps of chromosomes and their length is an indicator of biological age.

While telomeres normally shorten with age, short telomeres at a given age predict higher disease and mortality risks. Previously, it was found that prenatal exposure to maternal stress hormones and instability during embryo development results in short telomeres, i.e. accelerated cellular aging.

A new study funded by the Academy of Finland and the Turku Collegium for Science and Medicine manipulated prenatal exposure to maternal thyroid hormones using egg injection in an avian model.

“The telomere biology of humans is closer to the telomere biology of birds than those of traditional laboratory models. In both humans and birds, telomere length is minimally invasively measured from small blood samples.” , says Collegium researcher Antoine Stier of the University of Turku (Finland), the lead author of the research paper.

While the study authors had reasons to expect shorter telomeres in chicks hatched from eggs injected with thyroid hormones, they were somewhat surprised to find that those chicks actually exhibited longer telomeres soon after birth.

“Based on the natural decline in telomere length observed with age in the same collared flycatcher population, we estimated that chicks hatching from thyroid hormone-injected eggs were about four years younger at birth than hatched chicks. control eggs, ”adds Collegium researcher Suvi Ruuskanen.

While the molecular mechanisms underlying these effects remain to be discovered, the new findings suggest that prenatal thyroid hormones may play a role in defining the “biological age” at birth.

“Considering the interest and controversy surrounding gene therapy studies in humans to elongate telomeres as an anti-aging therapy, this discovery opens up potential avenues to better understand the influence of telomere elongation in animal models,” he says. Stier.

The study was conducted on a long-term monitored breeding population of wild flycatchers on the island of Gotland and was based on extensive collaborations with the University of Uppsala (Sweden), Lyon, Glasgow and Aberdeen.