Pain-free mouse? (Image: Getty)

Many researchers suspect a link between pain and lifespan. We know, for instance, that people experiencing chronic pain often die young. We also know that worms and flies lacking certain sensory neurons live longer than expected.

Now Andrew Dillin at the University of California, Berkeley, and his colleagues have shown that similar findings apply in mammals too.

He found that male mice genetically engineered to lack TRPV1 pain receptors – which are activated in response to high temperatures and hot chilli peppers in food – live almost 12 per cent longer than those with the receptor. Female mice lacking TRPV1 do even better: they live 16 per cent longer than other females.

Youthful characteristics

What's more, mice lacking the TRPV1 receptors retain some youthful features into old age. For instance, older mice without TRPV1 could metabolise oxygen far more efficiently than typical mice of the same age. They also had more pancreatic beta cells – these release insulin, which makes cells absorb glucose from the blood.

Further investigation revealed what was going on. Without the TRPV1 pain receptor, two proteins involved in the production of a neuropeptide called CGRP cannot be activated, says Dillin, so the mice produce less CGRP. As this neuropeptide inhibits insulin release, mice lacking TRPV1 are able to produce more insulin – which has beneficial knock-on effects for their metabolism.

As well as these advantages to lacking TRPV1 there are disadvantages too, says Dillin. For example, being able to sense pain helps animals avoid harmful objects and life-threatening situations. This probably explains why natural selection has retained the pain receptors in mammals.

"Pain is very important for animals living in the wild and probably outweighs the benefits of a youthful metabolism," he says.

A longer life?

But the results do suggest that reducing levels of TRPV1 or CGRP might be a way to improve our metabolism in old age, and perhaps even boost lifespan.

The lifespan-boosting properties of TRPV1 come as a surprise, says Gerard Ahern at Georgetown University in Washington DC, who has also explored the link between TRPV1 and metabolism in mice.

But he thinks finding ways to apply the discoveries to human health won't be easy. "Pharmacological antagonists [that block] TRPV1 have failed safety [testing]," Ahern says – people who took the therapy experienced short-lived hyperthermia and were prone to burning themselves because of their impaired heat sensation. "CGRP antagonists, currently being developed for migraine treatment, might be useful," he says.

Journal reference: Cell, DOI: 10.1016/j.cell.2014.03.051

Source: New Scientist URL: http://www.newscientist.com/article/dn25616-lifespan-boost-for-mice-that-feel-less-pain.html#.U4Lf7dIW3mU