Since 50 percent of TSC patients also suffer from autism, the findings offer new hope for addressing learning disorders due to autism, according to researchers.
Using a mouse model for TSC, the researchers tested rapamycin, a drug approved by the FDA to fight tissue rejection following organ transplants.
Rapamycin is well-known for targeting an enzyme involved in making proteins needed for memory and researchers went for it because the same enzyme is also regulated by TSC proteins.
"This is the first study to demonstrate that the drug rapamycin can repair learning deficits related to a genetic mutation that causes autism in humans. The same mutation in animals produces learning disorders, which we were able to eliminate in adult mice," Nature quoted principal investigator Dr. Alcino Silva, professor of neurobiology and psychiatry at the David Geffen School of Medicine at UCLA, as saying.
"Our work and other recent studies suggest that some forms of mental retardation can be reversed, even in the adult brain," Silva added.
First author Dan Ehninger, postgraduate researcher in neurobiology, said: "These findings challenge the theory that abnormal brain development is to blame for mental impairment in tuberous sclerosis."
"Our research shows that the disease's learning problems are caused by reversible changes in brain function -- not by permanent damage to the developing brain," Ehninger added.
Researchers studied mice bred with TSC and verified that the animals suffered from the same severe learning difficulties as human patients.
Next, the UCLA team traced the source of the learning problems to biochemical changes sparking abnormal function of the hippocampus, a brain structure that plays a key role in memory.
"Memory is as much about discarding trivial details as it is about storing useful information. Our findings suggest that mice with the mutation cannot distinguish between important and unimportant data. We suspect that their brains are filled with meaningless noise that interferes with learning," Silva said.
Ehninger said: "After only three days of treatment, the TSC mice learned as quickly as the healthy mice. The rapamycin corrected the biochemistry, reversed the learning deficits and restored normal hippocampal function, allowing the mice's brains to store memories properly."
The study is published in the online June 22 edition of Nature Medicine.