Friedreich’s ataxia (FRDA) patients have less mitochondria than other people because of the mutation in the frataxin (FXN) gene that is associated with the disorder, according to two studies.
University of California at Davis researchers also said that a multiple sclerosis therapy the United States and Europe have already approved could increase mitochondria and therefore alleviate the disease’s symptoms.
The studies were published in the journal Human Molecular Genetics. One was titled “Frataxin deficiency impairs mitochondrial biogenesis in cells, mice and humans.” The other was “Dimethyl fumarate mediates Nrf2-dependent mitochondrial biogenesis in mice and humans.”
“This represents groundbreaking work that provides an important contribution to understanding the pathology of both Friedreich’s ataxia and mitochondrial diseases,” Mike Murphy, principal investigator of the University of Cambridge’s MRC Mitochondrial Biology Unit, said in a news release written by Pat Bailey.
“The advances in these two papers are exciting because they suggest that a current drug could be used to treat FRDA and mitochondrial DNA diseases, for which there are few therapies,” Murphy said.
FRDA is characterized by low levels of the mitochondrial protein frataxin, which is caused by a variation in the FXN gene. The abnormality leads to dysfunction of mitochondria, the cell’s powerhouses — a process that ultimately results in increased oxidative damage and cell death.
Despite advances in understanding the mechanism underlying FRDA, scientists are unsure how it leads to the death of neurons and degeneration of muscles. With no therapies approved for treating these patients, FRDA is clearly an unmet medical need.
The California researchers discovered that low levels of frataxin are associated with down-regulation — or lower production — of mitochondria. They saw this not only in animal models of FRDA but also in blood and skin samples from patients with FRDA. The lower mitochondria production help explains the neurodegenerative and neuron cell death effects seen in these patients.
“Knowing now that the frataxin deficiency causes a shortage of mitochondria, we and others may be able to use the number of mitochondria as a biomarker for determining the disease severity and progression in Friedreich’s ataxia patients,” said Gino Cortopassi, a professor at the UC Davis School of Veterinary Medicine who was senior author of the study.
“Such a biomarker could also be used to evaluate the effectiveness of new drugs for treating the disease,” Cortopassi added.
Researchers also discovered that Tecfidera (dimethyl fumarate, or DMF), which is used to treat multiple sclerosis, promotes the production of mitochondria.
The two studies not only shed light on the mechanisms that underlie FRDA but also suggest a way to tackle the disease.
“Taken together, these findings suggest that DMF, by increasing mitochondria, has the potential to lessen the symptoms of muscle diseases, which are caused at least in part by mitochondrial abnormalities,” Cortopassi said.
“DMF is a well-known drug approved by regulatory agencies in both the U.S. and Europe and clinically used worldwide for many years,” said Franco Taroni, a physician and researcher at the Carlo Besta Neurological Institute in Milan. “Thus, the finding that it stimulates mitochondrial biogenesis in multiple sclerosis patients is very important and provides great perspectives for the treatment of patients with the many rare disorders affecting mitochondrial function, including the devastating Friedreich’s ataxia.”
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