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May 12, 2008 -- A class of drugs used to treat erectile dysfunction may one day help delay or even prevent heart failure in patients with the most common forms of muscular dystrophy, according to a study published in the May 13 issue of the Proceedings of the National Academy of Sciences.
Duchenne muscular dystrophy is a progressive muscle-wasting disease that primarily strikes boys between ages 2 and 6 years old. It affects all voluntary muscles, including the lungs and heart. Most patients die before age 30. Duchenne muscular dystrophy and a less severe variant called Becker muscular dystrophy affect about one in every 3,500 to 5,000 boys in the United States.
Maya Khairallah of the Montreal Heart Institute and colleagues assigned mice with muscular dystrophy to either a placebo or Viagra. The mice received the drug once a day for six weeks.
Imaging tests showed that the mice that received Viagra had improved heart performance.
Viagra is a type of drug called a phosphodiesterase type-5 (PDE5) inhibitor. It blocks the enzyme PDE5 and prevents the breakdown of a natural substance called cyclic guanosine monophosphate (cGMP).
Khairallah's team also discovered that having a gene that increased cGMP production helped maintain normal heart function in mice with muscular dystrophy.
The findings support existing theories that defects in the cGMP signaling pathway play an important role in the development of muscular dystrophy-related heart muscle problems. The study's authors believe their research suggests that the evolution of heart problems in muscular dystrophy patients could be prevented by partially restoring this pathway. Therefore, medications that increase cGMP signaling, such as Viagra, may prove to be a novel therapeutic approach for the treatment of muscular dystrophy-related cardiomyopathies (heart muscle problems) in the future.
The researchers encourage future studies to determine whether PDE5 inhibitors could delay, prevent, or even reverse the onset of heart injury and loss of function in patients with Duchenne and Becker muscular dystrophies.