New gene therapy research helps battle Muscular Dystrophy, Glycogen Storage Disease

The next big medical breakthrough could come from an unusual place, your pet. Find out how in Tuesday’s Medical Moment.

They keep us company, make us smile, and are always there to lend a paw, but could dogs do even more? Right now, our four-legged friends are also helping scientists find cures for serious diseases.

On the outside, she's like any other five-year-old. On the inside, Haylee Fiske's body can't keep up. Haylee suffers from Glycogen Storage Disease. Her liver can't release sugar fast enough.

"Their brains end up with hypoglycemia, and they can either end up developmentally delayed, or unfortunately, even dying,” Dr. David Weinstein said.

The only treatment for Haylee's condition is a strict meal schedule.

Dr. Weinstein at the University of Florida is pioneering a treatment. After two injections of genes designed to restore a faulty enzyme, a dog with the same condition can now eat a normal diet.

"The disease is so mild now that we have not had to do any medical
Intervention," Weinstein said.

Another treatment in dogs brings hope to patients with Muscular Dystrophy. A new drug cocktail helped dogs go from struggling to walk, to running.

Experts say the injection works like a band-aid that covers up the genetic mutation linked to muscle weakness.

"It's almost as if you were reading a recipe, and instead of putting salt, your mutation said put in lots of hot pepper instead. Well, your cake wouldn't be so great. This band-aid lets it skip over that wrong pepper instruction," Eric Hoffman PhD from Children’s National Medical Center said.

Trials of the treatment have begun in humans and could eventually help people like Drew Bonner.

"How's life any fun if you're just going to be a downer? Why not just live it and be happy?” patient Drew Bonner said.

For now, Drew takes on his obstacles with a smile and waits for medicine's next solution.

Before Dr. Weinstein's treatment, the longest a dog had lived with this disease was 28 days. The treated dog is now two-and-a-half years old.

TREATING DOGS, CURING HUMANS?

BACKGROUND : Although numbers have declined in recent years, dogs are widely used in biomedical research, often as "models" for human disease. The U.S. Department of Agriculture (USDA) reports close to 65,000 dogs were used as research subjects at USDA-registered facilities in 2004, the most recent year for which data is available. Dogs are used as models for human diseases in the areas of cardiology, endocrinology, and bone and joint studies, according to the Humane Society of the United States. As of 2006, only 20 medical schools in the
U.S. used live animals like dogs in elective courses.

GLYCOGEN STORAGE DISEASE : Glycogen storage disease type 1A is a rare genetic disease that prevents the body from being able to correctly store and use sugar between meals. In order to survive, children and adults with the disease have to abide to a strict meal schedule and take precise doses of cornstarch every few hours. Dogs with the condition have to be fed sugar every 30 minutes, or they can die. If children aren't diagnosed with the condition as babies, they often experience developmental delays and an enlarged liver. If not diagnosed when those symptoms appear, the child will most likely end up with brain damage, or die, David Weinstein, M.D., director of the Glycogen Storage Disease Program at the University of Florida in Gainesville, explained to Ivanhoe.

Dr. Weinstein is the co-investigator of a study testing gene therapy as a treatment -- and possibly a cure -- for dogs and humans with glycogen storage disease. Since the condition stems from a faulty enzyme that doesn't convert stored sugar into glucose -- the type of sugar the body uses for energy -- researchers administered two injections of genes meant to restore this enzyme to a dog. The dog received one dose at birth and another at five months old. Six weeks after the second injection, the dog was weaned of glucose supplements entirely. The dog hasn't required any supplementation since then, and is now two-and-a-half years old. Researchers plan to test the gene therapy in dogs for at least another year before entering human trials.

MUSCULAR DYSTROPHY : Muscular dystrophy is a group of inherited muscle diseases that cause muscle fibers to be unusually susceptible to damage and thus become progressively weaker. Duchenne's muscular dystrophy is the most severe type of the condition, occurring mostly in young boys. Symptoms – which include frequent falls, large calf muscles, difficulty getting up and a waddling gait -- most often first appear between the ages of 2 and 3, according to the Mayo Clinic.

Researchers have successfully treated a dog with a condition similar to Duchenne's muscular dystrophy using a drug that "covers up" the mutation that causes muscular dystrophy. "It's almost like a Band-Aid over the dog's problem with the gene or the mutation to get the dog's cells or its muscles to skip over the mutation and, as a result, repair the gene and make new protein to save the muscle," Eric Hoffman, Ph.D., director of the Research Center for Genetic Medicine at Children's National Medical Center in Washington, D.C., explained. Dr. Hoffman says this is the first therapy that has helped a large animal with a muscular dystrophy-type disease, and the treatment bodes well for human trials.

For More Information, Contact:
David Weinstein, MD, MSc
University of Florida
Gainesville, FL
weinsda@peds.ufl.edu


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