Life span lengthens when mice feel less pain

Mice with less pain live longer. When the animals lack a certain pain-sensing protein, their life span increases by an average of 10 to 15 percent, scientists report May 22 in Cell.

With age, many people suffer more frequent bouts of pain, says study coauthor Andrew Dillin of the University of California, Berkeley. He and his team wondered about pain’s connection to getting older. “We simply just asked, is pain actually driving the aging process or is it part of the process, just going along for the ride?” Dillin says.

The team studied mice genetically engineered to lack the protein Trpv1, a molecule important for sensing pain. Perched on the outsides of nerve cells, Trpv1 senses scalding heat and spicy chili peppers, among other things. It also helps detect body temperature and influences insulin-producing cells in the pancreas.

Mice lacking Trpv1 appeared normal, except that male mice fought one another viciously. But the team uncovered a big difference in their metabolic health. Mice without Trpv1 were able to process sugar more effectively than mice with TrpV1. This benefit remained even as the animals aged. Old mice lacking Trpv1 also had more insulin-producing cells, which help the body metabolize sugar, in their pancreas than older mice with Trpv1.

This link between pain sensation, metabolism and life span is exciting because the same connection may occur in other animals, says molecular physiologist Rochelle Buffenstein of the University of Texas Health Science Center at San Antonio. “It might be a global mechanism that they’re picking up on.”

Evidence from studies on a subterranean rodent supports a link between pain sensing and life span. Buffenstein and others have found that the naked mole-rat, a small rodent that lives to the unusually old age of 30 years, lacks a typical pain response.

Favorable metabolic changes that come with a reduced-pain existence might be driving life span extension in the mice. Male mice that lack Trpv1 live about 10.6 percent longer than males with the protein, from an average of 937 days to 1,036 days. In females, the average increase was about 15.6 percent, from 828 days to 957 days, the team found.

It’s unclear whether metabolic effects alone alter life span or the experience of pain, and the stress and anxiety that come with it, also contribute.

“All we know is that when we reduce pain, we increase metabolic health,” Dillin says. When a person or animal experiences pain, changing aspects of metabolism might help get through the rough patch, Dillin says.

Drugs that combat migraines in people might tap into this pathway, possibly improving metabolism and even life span, Dillin says. These drugs block the action of a protein called CGRP that’s released when nerve cells containing Trpv1 become active.