Five diabetic beagles no longer needed insulin injections after being given two extra genes, with two of them still alive more than four years later.

Several attempts have been made to treat diabetes with gene therapy but this study is "the first to show a long-term cure for diabetes in a large animal", says Ftima Bosch, who treated the dogs at the Autonomous University of Barcelona, Spain.

The two genes work together to sense and regulate how much glucose is circulating in the blood. People with type 1 diabetes lose this ability because the pancreatic cells that make insulin, the body's usual sugar-controller, are killed by their immune system.

Delivered into muscles in the dogs' legs by a harmless virus, the genes appear to compensate for the loss of these cells. One gene makes insulin and the other an enzyme that dictates how much glucose should be absorbed into muscles.

Dogs which received just one of the two genes remained diabetic, suggesting that both are needed for the treatment to work.

Bosch says the findings build on an earlier demonstration of the therapy in mice. She hopes to try it out in humans, pending further tests in dogs.

Other diabetes researchers welcomed the results but cautioned that the diabetes in the dogs that underwent the treatment doesn't exactly replicate what happens in human type 1 diabetes. That's because the dogs' pancreatic cells were artificially destroyed by a chemical, not by their own immune systems.

"This work is an interesting new avenue which may give us a completely new type of treatment," says Matthew Hobbs, head of research at the charity Diabetes UK. "The researchers' plan to test the treatment in a larger number of dogs with naturally occurring [type 1] diabetes is a sensible way to gather stronger evidence that will be needed before this experimental treatment is ready to be tested in humans."

Journal reference: Diabetes, doi.org/kf3

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Gene therapy cures diabetic dogs