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Mayo Clinic discovers new genetic candidates for irritable bowel syndrome

ROCHESTER, Minn. — Most people associate serotonin with brain neurology, but over 95 percent of the body’s serotonin occurs in the gastrointestinal tract, which has a complex neuronal circuit that has been called “the second brain” of the body. Now a Mayo Clinic research team has identified a number of genetic variants in serotonin genes that impact irritable bowel syndrome or IBS. The findings are being presented today at Digestive Disease Week 2010 in New Orleans.

IBS is one of the most common chronic disorders of the digestive tract. It can cause years of discomfort or pain and altered bowel habits, limit a person’s personal and professional life, and cost millions nationally in medical costs and loss of time from work or school.

“It’s been known that some drugs that alter serotonin levels in the body also have an effect on motility, thus prompting IBS-like symptoms, but the genetic and molecular mechanism for IBS was unclear,” says Yuri Saito, M.D., Mayo Clinic gastroenterologist and presenter of the study. “A number of studies had looked at a few polymorphisms and a handful of genes.”

The Mayo team used high throughput technology to study nearly 400 tagged single-nucleotide polymorphisms (SNPs) in over 20 serotonin-related genes.

Using a familiar analogy, Dr. Saito says, “Rather than sending out a few patrol cars to look for culprits by rounding up ‘the usual suspects,’ we launched a genetic dragnet that took an objective, unbiased look at a broader range of possibilities.” They found a number of previously unknown IBS associations. The conclusion: Many more serotonin-related SNPs were implicated in IBS than first thought. The implicated genes relate to serotonin synthesis, metabolism and receptors. The researchers also found IBS may be caused by multiple genes — not just one or a few — and there may be distinct as well as overlapping molecular mechanisms that cause diarrhea and constipation, two major symptoms of IBS.

The findings offer future researchers specific targets for drug development or other therapies to combat IBS.

Other involved in the study were Joseph Larson; Elizabeth Atkinson; Euijung Ryu, Ph.D.; Ann Almazar-Elder; Nicholas Talley, M.D., Ph.D.; Michael Camilleri, M.D.; and Gloria Petersen, Ph.D., all of Mayo Clinic. The study was supported by the National Institutes of Health.

About Mayo Clinic

For more than 100 years, millions of people from all walks of life have found answers at Mayo Clinic. These patients tell us they leave Mayo Clinic with peace of mind knowing they received care from the world’s leading experts. Mayo Clinic is the first and largest integrated, not-for-profit group practice in the world. At Mayo Clinic, a team of specialists is assembled to take the time to listen, understand and care for patients’ health issues and concerns. These teams draw from more than 3,700 physicians and scientists and 50,100 allied staff that work at Mayo Clinic’s campuses in Minnesota, Florida, and Arizona; and community-based providers in more than 70 locations in southern Minnesota, western Wisconsin and northeast Iowa. These locations treat more than half a million people each year. To best serve patients, Mayo Clinic works with many insurance companies, does not require a physician referral in most cases and is an in-network provider for millions of people. To obtain the latest news releases from Mayo Clinic, go to www.mayoclinic.org/news. For information about research and education, visit www.mayo.edu. MayoClinic.com (www.mayoclinic.com) is available as a resource for your general health information.




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