When Daniel Promislow jogs with his Weimaraner, Silver, it pains him to see age creeping up on the 11-year-old canine.
“Month by month, he gets slower and slower,” said Promislow, an evolutionary geneticist at the University of Washington. His other dog, Frisbee, still frolics like a pup – but at 10, she also qualifies as elderly.
It’s a sad reality of pet ownership that our beloved companions never live as long we would wish.
But Promislow and his colleagues think it might be possible to shift those mortality curves – at least a little.
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Drawing on developments in the field of anti-aging science, they hope to find out whether a chemical that extends the life spans of yeast, fruit flies, worms and mice will do the same for dogs.
“We’re not talking about doubling the healthy life spans of pets,” said UW molecular biologist Matthew Kaeberlein. “But at a minimum I would predict that you would get a 10 to 15 percent increase in average life span, and I think bigger effects are possible.”
Kaeberlein and Promislow hosted a meeting in Seattle recently where experts from across the country brainstormed about the best way to gauge the effects of the drug rapamycin on the health and longevity of pet dogs.
Currently used along with several other medications to prevent rejection in organ-transplant patients, rapamycin has emerged as the most promising candidate among dozens of substances studied for anti-aging effects. Nearly 50 laboratory studies have shown that the compound can delay the onset of some diseases and degenerative processes and restore vigor to elderly animals, as well as extend average life spans by 9 to 40 percent.
No one knows if the drug might have similar effects in people. At the high doses used for organ transplants, rapamycin is associated with potentially serious side effects, including poor wound healing and an increased risk of diabetes.
The low doses used in anti-aging research with mice and other lab animals cause few side effects, but studies in people at those dose levels are lacking. Large-scale human trials are costly and would take decades to complete.
But with dogs, who suffer from many of the same old-age ailments as their masters, it could be possible to find out in a few years whether rapamycin is beneficial.
“I think it’s worth a go, not just from what it can teach us about humans but for the sake of the animals themselves,” said Steven Austad, chairman of the University of Alabama Biology Department. “It may not work in dogs, but if it did, boy, it’s going to be huge,” said Austad, an expert in aging research who is not part of the UW project.
Rapamycin functions partly by inactivating a protein that promotes cell growth, Kaeberlein explained. As a result, cells grow more slowly, which retards the spread of cancer. The same mechanism is very likely activated by caloric restriction – another approach that has been shown to extend the lives of laboratory animals, including monkeys.
Rapamycin also seems to have an anti-inflammatory effect. And in elderly mice, it caused marked improvement in heart function.
Cardiovascular effects are among the first things the researchers hope to track in dogs, Promislow said.
Some breeds, including Newfoundlands and Dobermans, are particularly vulnerable to heart failure. Across most breeds, though, cancer is the leading cause of death. And large dogs generally have shorter life spans than the small breeds.
“We’re trying to understand why some dogs age better than others, and help all dogs age in a better way,” Promislow said.
The researchers, who got $200,000 in seed money from the University of Washington, plan to start as soon as possible with a pilot study of 30 large, middle-aged dogs. The dogs would be pets, not laboratory animals. Half would get low doses of rapamycin, and half would get placebos.
The animals would be monitored closely to see if the treatment causes any side effects and whether it improves heart function or delays the onset of heart problems or cancer.
Simply postponing disease could boost dogs’ “health span” – the period of healthy, active life they enjoy – even if the drug doesn’t increase their overall life spans, Promislow pointed out.
The researchers eventually hope to persuade hundreds of dog owners, probably in different parts of the country, to enroll their pets in a much larger experiment. The goal would be to study the normal aging process of dogs, as well as the long-term effects of rapamycin and how the drug functions in canines.
But that’s not the kind of project federal agencies like the National Institutes of Health, with a focus on human disease, are likely to finance, Austad said.
So the UW team is looking for unconventional sources of money.
Drug companies aren’t very interested in rapamycin, because it’s no longer under patent. But dog-food companies and some foundations might be willing to contribute. Most of all, the scientists are pinning their hopes on fellow dog lovers.
“Given how I feel about my pets, I see this as a unique project where there’s a real potential for citizen science,” Kaeberlein said. “I think it would be great if pet owners who are really interested in improving the health of their animals would help fund this work.”
The study is still in the planning stages, and the researchers don’t have a funding goal yet. But they set up a website, dogagingproject.com, where people can donate – and sign up their dogs for possible inclusion in the research.
The UW project sounds logical and well-thought-out, said Jeffrey Halter, director of the University of Michigan Geriatrics Center. But he cautioned that it’s important to remember that the path to new drugs and treatments for animals and humans alike is “long, winding and difficult.”
A few years ago, the compound resveratrol – from grapes and red wine – was hailed as an anti-aging breakthrough. But follow-up studies have been disappointing.
“I think most of us who work in this field are not looking for an instant miracle,” Halter said.