Cystic Fibrosis Linked to Fatty Acid Imbalance
Discovery on genes and fatty acids no cure
WEDNESDAY, Feb. 4, 2004 (HealthDayNews) -- People with cystic fibrosis (CF), and even people who are just carriers of the cystic fibrosis gene, have an imbalance of fatty acids.
In the Feb. 5 issue of the New England Journal of Medicine, researchers report that the cystic fibrosis gene is linked to an overabundance of arachidonic acid (AA) and too little docosahexaenoic acid (DHA) in the body's tissue.
Fatty acids, such as AA and DHA, are essential to the development of healthy cells. They are important in many biological functions, including helping the body regulate inflammation.
"We've found at least one pathway by which mutations in the CF gene can lead to disease, and it will hopefully give rise to at least one new treatment," says one of the study's authors, Dr. Steven Freedman, director of the Pancreas Center at Beth Israel Deaconess Medical Center in Boston, Mass.
However, he adds, "It probably won't be a cure-all."
Dr. Preston Campbell, executive vice president of medical affairs for the Cystic Fibrosis Foundation, says that lung function in people with cystic fibrosis decreases by about 2 percent to 3 percent a year. So if a powerful anti-inflammatory therapy could be developed from this discovery that could "reduce the decline by 1 percent a year, you could add decades to CF patients' lives," he says.
About 30,000 people in the United States have cystic fibrosis, according to the CF Foundation. That means they inherited the cystic fibrosis gene, CFTR, from both parents. Another 10 million people are believed to be carriers of the disease, which means they inherited the CFTR gene from only one parent.
Cystic fibrosis causes mucus to collect in the lungs, resulting in wheezing, coughing and a susceptibility to serious infections. The pancreas is also often involved, which often results in malabsorption of the nutrients in food. The average life span for someone with cystic fibrosis is 33 years, according to the CF Foundation.
Freedman and his colleagues had previously studied fatty acid levels in mice that had been given cystic fibrosis. They found that the mice didn't have adequate DHA levels and had too much AA. When given DHA supplements, the mice improved, says Freedman.
For this study, the researchers tested tissue samples from 38 people with cystic fibrosis, 13 people who carried the CF gene, 11 people with inflammatory bowel disease, nine people with an upper respiratory infection, and 16 people with asthma.
The reason they tested people with other illnesses was to determine whether inflammation, a common finding in all of these disorders, was the cause of the fatty acid abnormalities, or if the abnormalities were present only in people with CF.
"What we found in mice, we found in humans," says Freedman: too little DHA and too much AA.
The researchers also found these changes, though to a lesser degree, in people who carried the CF gene but didn't have the disease. They did not, however, see these fatty acid abnormalities in people with other inflammatory diseases, such as asthma or inflammatory bowel disease.
"This is an interesting study that shows cystic fibrosis is a very complex disease," says Dr. Jan Larsen, head of the Ochsner Children's Research Institute in New Orleans. "No one has been able to make a specific correlation from the CFTR gene and the mechanism that produces symptoms of the disease."
"CFTR is like a master switch that probably turns on several different mechanisms. This study isolates one of those mechanisms," says Dr. Gregory Pastores, a geneticist at New York University Medical Center in New York. "This may open a window to rational therapeutic approaches."
The finding that humans have this fatty acid change means that "it's a new target for therapies," adds Freedman.
However, both Freedman and Campbell caution against supplementing with large doses of DHA, which is available over the counter. They point out that there is no direct evidence that it will be helpful in humans, and the doses used in mice were large enough that the equivalent dose in humans would make a person feel bloated and sick, according to Freedman.