For naked mole-rats, breeding is longevity

Naked mole-rats that breed live longer than non-breeders of the species, defying the prevailing scientific view on reproduction and ageing.

According to evolutionary theory, there is an energy trade-off between breeding and maintaining the body’s many tissues. Reproduction uses some of the energy needed to keep the body healthy, and lifespan decreases as a result.

New research from Germany’s Leibniz Institute on Ageing shows that, at least for the mole rats (Heterocephalus glaber), this isn’t necessarily the case.

The study published in the journal BMC Biology found that naked mole-rats age at different rates once they reach sexual maturity, with reproduction appearing to actually prolong the animals’ lifespans.

“This goes against the common expectation that mammals either invest resources in a long life or in reproduction,” explains Martin Bens, corresponding author of the study.

Native to the grasslands of tropical East Africa, the naked mole-rat can live for more than 30 years — a lifespan far outpacing those of mice (which average four years) and rats (which rack up five). The present study sought to unravel the genetic mechanisms behind this longevity.

Employing a technique called comparative transcriptome analysis, Bens and colleagues took tissue samples of 10 different organs from breeding and non-breeding naked mole-rats. By examining the RNA in each tissue type, the team could discern which genes were being transcribed to create specific proteins. Samples were also taken from guinea pigs (Cavia porcellus) as a contrasting rodent model.

The analysis revealed stark differences in how gene expression varied among groups. Breeding naked mole-rats showed higher expression of genes relating to muscle regeneration, which may help slow the physical process of ageing and explain why breeders live longer.

Even more remarkable, there was no difference in gene expression between male and female non-breeding naked mole-rats. While the guinea pigs showed a high degree of physical and genetic sexual dimorphism — differences between the sexes — the mole rats only showed sex-specific changes after they started reproducing.

Sexual maturation was also associated with a change in gene expression levels linked to extended life and health span.

The findings add to the naked mole-rat’s already impressive list of biological achievements: it can survive up to 18 minutes without oxygen, numb itself to pain, and has a gene that halts the development of cancerous tumours.

Further studies on naked mole-rats have potential to deepen our understanding of the mechanisms behind puberty in humans.

“Variations in puberty onset have implications for the risk for diseases such as breast cancer or cardiovascular diseases,” explains Bens. “Our data may help identify targets to mitigate these variations.”