Fall 2017

Collaborating for a Cure

Veterinary and human cardiologists at Tufts make the case for studying a heart condition together to accelerate the pace of new treatments.

By Genevieve Rajewski

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John Rush conducts an echocardiogram on a cat at Cummings Veterinary Medical Center. Photo: Anna Miller

Seven years ago, I came home to a terrible surprise: My 10-year-old cat Cosmo lying dead in the hallway. Cosmo had just received a clean bill of health from the veterinarian and was completely normal only an hour before. Although I did not pursue a necropsy to confirm, my veterinarian suspected that Cosmo died from hypertrophic cardiomyopathy.

The cardiac disorder, in which heart muscle becomes abnormally thick and dysfunctional, is very common in cats, affecting at least 1 in 10 pets. My experience also was not unusual: The majority of affected animals have no symptoms at all. “Most of the cats we see with outward symptoms of the disease come in through the emergency room,” said John Rush, a veterinary cardiologist at the Henry and Lois Foster Hospital for Small Animals. “These cats are normal, normal, normal, normal… until there’s a life-threatening issue. The owner will tell us, ‘He was fine yesterday.’”

A similar condition afflicts humans. “Hypertrophic cardiomyopathy is present in about 1 in 500 people,” said Gordon Huggins, a physician researcher at the Molecular Cardiology Research Institute at Tufts Medical Center. The disease is a common cause of sudden cardiac arrest in young people, including among athletes who die on the playing field. Although an echocardiogram can diagnose hypertrophic cardiomyopathy in both humans and cats—and implantable cardiac defibrillators can help safeguard those human patients most at risk for sudden death—there’s no medication or therapy that stops or significantly slows the progression of heart failure. Tufts cardiologists working in both human and veterinary medicine now hope they can change that by encouraging interdisciplinary research—a strategy they outlined in the August 2017 issue of Cardiology Research. “As a rule,” explained Huggins, one of the authors, “the greater the opportunity to collaborate, the greater opportunity to make meaningful, impactful discoveries.”

In both people and cats, hypertrophic cardiomyopathy is often linked to genetic mutations, and nearly all the discovered mutations involve a gene that develops an abnormal protein in the heart muscle. Unlike lab rodents, cats show the same symptoms, disease progression, and response to treatment as affected people, making pets a better model to test novel drugs. “Cats really serve as a great model for us to learn about hypertrophic cardiomyopathy,” said Martin Maron, a coauthor on the paper and director of the Hypertrophic Cardiomyopathy Center at Tufts Medical Center. “There aren’t all that many examples of human heart disease being present in almost exactly the same form in animals.” More clinical trials in pet cats being treated for the condition also would be a potential boon for feline medicine, which has no real public funding to study new veterinary therapies for the heart disorder.

One mystery to unravel is why even affected siblings can have such different outcomes—for example, one brother enjoying a long life free of symptoms of hypertrophic cardiomyopathy, the other dying young from heart trouble. Lisa Freeman, J86, V91, N96, a veterinary nutritionist at Cummings School and the lead author of the Cardiology Research paper, said this may be because other modifier genes or environmental factors affect the disorder’s severity. Several studies by Cummings School veterinarians have demonstrated that, compared with healthy pets, cats with hypertrophic cardiomyopathy have bigger skeletons, larger heads, and higher concentrations of insulin-like hormones related to growth and glucose—and that these animals tend to grow bigger more quickly in early life. Freeman said that these data suggest that diet and growth patterns early in life, even in utero, may play a significant role in how the disease develops.

Unraveling these nutrient-gene interactions may provide a key opportunity for improved therapeutic targets and nutritional strategies for managing hypertrophic cardiomyopathy, Freeman said. And, unlike with people, whose diets are hard to restrict for such studies, “we can control cats’ diets very carefully.” What we learn, she added, may “help not only cats, but ultimately humans.”

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