Viagra keeps ailing hearts pumping

By Alison Motluk It keeps a penis erect, reduces pulmonary hypertension, staves off altitude sickness and keeps a plant from wilting. As if that weren’t enough, Viagra could yet win another accolade: in mice, the drug appears to prevent the heart damage caused by muscular dystrophy. Viagra (sildenafil citrate) is known to inhibit the breakdown of cyclic GMP, an enzyme that not only dilates the blood vessels in the penis, but is also involved in the signalling pathways that keep the heart healthy. This led Christine Des Rosiers at the Montreal Heart Institute, Canada, and colleagues to wonder whether the drug could help prevent degeneration of heart muscle, a factor that kills increasing numbers of people born with muscular dystrophy (MD). To do this, she turned to mice that had been engineered to develop features of human MD. Mice were given an adrenaline-like substance that increased the workload on the heart – up to levels that would typically cause injury in animals with muscular dystrophy. Des Rosiers found that mice given a dose of Viagra – equivalent to the amount a man would receive for erectile dysfunction – coped significantly better than animals not given the drug. Echocardiography and other measures showed that the heart function was better, suggesting that Viagra had protected the heart muscle. “It makes perfect sense that it would work in these mouse models,” says Elizabeth McNally, at the University of Chicago Medical Center, Illinois. “It fits.” She notes, however, that the success doesn’t mean a drug for humans is just around the corner – it is hard to run clinical trials in patients with muscular dystrophy, since their numbers are small. Des Rosiers speculates that, since PDE5 inhibitors (a group of drugs that includes Viagra) target cyclic GMP in other parts of the body too, it might be more useful in muscular dystrophy than her study indicates. “It could also be good for other aspects of the disease,” she says. Muscular dystrophy is a catch-all name for a group of inherited muscle-wasting diseases. Over time, face, arm, leg, spine and heart muscles weaken and wither. Research has traditionally focused on the skeletal muscles, but with increasing life expectancy – now well into the 20s – heart failure has become a major cause of death. Journal reference: Proceedings of the National Academy of Sciences (DOI:
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