April 12, 2000 (Atlanta) -- If results of a new animal study translate even in part to human beings, those who've inherited the Huntington's disease gene may be able to delay the onset of symptoms. Scientists found that mice genetically engineered to develop the disease remain symptom-free significantly longer when they live in a specially enhanced, stimulating environment than when they are kept in a regular cage. The findings appear in the April 13 issue of the journal Nature.
Huntington's disease is an inherited disorder that manifests later in life with severe jerking movements and psychiatric symptoms like psychosis, dementia, personality changes, and depression. The disease is very disabling and results in an early death. It typically appears between the ages of 30 to 40 but can occur either in childhood or in the elderly.
"What we did was take a group of mice in which the gene for Huntington's disease had been inserted, and exposed one set to normal conditions and another set to a novel, or enriched, environment. There was a profound delay in disease onset in the enriched-environment mice," says lead author Anton van Dellen, MD, a Rhodes scholar and researcher at Oxford University in England.
Young Huntington's disease and normal mice were housed in groups either in standard laboratory cages or in enhanced cages where "every two days they were exposed to a new set of sensory stimuli including cardboard sheets, paper to shred, and colorful plastic objects to climb on and explore," says van Dellen.
To judge what effect environment had on the disease, the mice underwent a weekly test to examine their coordination. By the time every one of the non-enriched animals had failed the test, indicating they had gone on to develop Huntington's, only one of the mice living in the enriched environment showed any symptoms at all.
The researchers then examined the animals' brains and found the area that normally worsens in the wake of Huntington's disease was 13% larger in the mice living in the stimulating environment. Van Dellen tells WebMD that he is currently investigating "how connections [in the brain] are altered in the disease and how environmental enrichment affects those changes."
Although this is the very first time that scientists have been able to delay disease onset, van Dellen tells WebMD that it's far too early to tell Huntington's disease patients with any certainty that a particular activity or lifestyle will keep symptoms at bay. Environmental enrichment is quite complex, he says, and any number of potentially important factors could be at work.
"Enriched-environment mice were continually exposed to new sensory stimuli," van Dellen tells WebMD. "They exercised more. They used fine-motor skills." Much harder to quantify, but also worth investigating, is what he calls "the enjoyment factor." Perhaps the benefit came not from any one factor, but rather from the "pleasure" or stress-relief of the overall environment. "You're in a less stressful environment if you're running on a wheel than if you're sitting all day in the corner of a box," he says.
Even though this finding is only the beginning of extensive future work, van Dellen tells WebMD that there is most definitely cause for optimism. "I think the fact that there's been such a clear link shown between environment and disease onset shows that we're not just products of our genetic makeup, but also of how we interact with our environment. We can steer our own fate by the environment we choose."
- Scientists have been able to delay the onset of Huntington's disease in mice by providing them with a stimulating environment.
- With Huntington's disease, certain areas of the brain degenerate, but these stimulated mice showed less degeneration than other mice with the disease.
- Researchers do not yet know how the findings will translate to humans, partly because an enriched environment is difficult to quantify, as it encourages more exercise, more fine-motor skills, more enjoyment, and less overall stress.