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A mouse eats its fill—but calorie-restricted rodents typically live longer.

A mouse eats its fill—but calorie-restricted rodents typically live longer.

Steve Berger/Wikimedia

U.S. aging researchers prepare for loss of hungry mouse colony

The National Institute on Aging (NIA), part of the U.S. National Institutes of Health, revealed earlier this month that it will be phasing out its colony of calorie-restricted rodents. Although most researchers who study aging won’t be affected by the decision, some scientists will have to pay substantially more for experimental mice, and some may be priced out of the field.

In the 1930s, researchers first noticed that a very low-cal diet prolongs the life of some animals. This regimen, known as calorie restriction (CR), also delays age-related maladies such as cardiovascular disease and cancer. For nearly 20 years, NIA has sponsored a colony of calorie-restricted rodents, which are available only to its grantees. The price was right: Until this year, researchers paid $6 per month of the animal’s age plus shipping. And because of a rule change that went into effect in January 2014, the rodents are now free.

Despite the low prices, there isn’t much appetite for the CR mice. Just eight to 10 researchers request animals from the colony each year, says NIA’s Nancy Nadon, chief of the Biological Resources Branch. On 11 June, NIA announced it would not renew the contract with the company that houses the rodents, Charles River Laboratories in Wilmington, Massachusetts. “The way the usage has changed over the last few years,” Nadon says, “it wasn’t the best way to go about using NIA funds.” (She had no estimate of what maintaining the colony costs.)

The decision won’t immediately foreclose researchers’ access to CR mice. New rodents will enter the colony until 2018, so older mice should be available into 2020. And NIA will continue to maintain a separate colony of aged rodents. If NIA-funded researchers desperately need CR animals, Nadon says it might be possible to shift some of those mice to a reduced diet.

Few researchers are likely to miss the colony. Most scientists who rely on CR rodents raise them at their own institutions, so “for the majority of researchers, this shutdown will not have any effect,” writes gerontological researcher Valter Longo of the University of Southern California in Los Angeles in an e-mail to ScienceInsider. In addition, the colony didn’t produce enough strong science, says Roger McDonald, a physiologist and cell biologist who is about to retire from the University of California, Davis.

Still, some researchers will be sad to see the colony go, although they understand NIA’s financial constraints. “I think it’s a valuable and unique resource, and I hate to see it lost,” says physiologist Arlan Richardson of the University of Oklahoma Health Sciences Center in Oklahoma City.

Hardest hit will be researchers who can’t raise their own CR animals, or “who are early in their careers or are just starting out in CR research,” says Richard Weindruch, a gerontologist at the University of Wisconsin, Madison.

Vascular physiologist Anthony Donato of the University of Utah School of Medicine in Salt Lake City agrees. “They are closing down the ability of some young investigators to pursue calorie restriction research,” he says. In large part, that’s because of the often higher cost of raising CR mice yourself. He notes that the NIA animals, which were about 30 months old, cost him about $120 to $130 apiece. But raising them at his university, which Donato now plans to do, will run about $1 per day—and the mice will have to stay on the severe diet for more than 2 years. He can afford the higher cost, but other researchers can’t.

Another user of the NIA’s CR colony, nutritional immunologist Elizabeth Gardner of Michigan State University in East Lansing, is also rethinking plans and budgets. She has received the NIA mice since the late 1990s, using them for three or four projects, including for a 2011 paper that showed calorie restriction reduced the animals’ ability to recover from flu shots. Now, Gardner says, she intends to obtain mice from NIA’s aged animal colony and calorically restrict them herself, “but it will be more expensive.”

Gerontologist Richard Miller of the University of Michigan, Ann Arbor, worries that the CR colony shutdown presages shortages at NIA’s colony of aged rodents, which more scientists depend on. Because NIA can no longer charge for the animals, it can’t recoup any of the cost of providing them. “I don’t see how they [NIA] can afford to give away mice that they used to sell,” he says. He’s concerned that NIA will also eventually have to slash the number of aged animals it furnishes.