- By Emily Gurnon
For the first time, research has shown that our genes may have an influence over some of the bacteria that causes Crohn’s disease and ulcerative colitis.
The diseases, known collectively as inflammatory bowel diseases, or IBD, cause persistent diarrhea and abdominal pain.
Your “gut microbiome,” or the bacteria in your intestines, “can have a big impact on your health for the rest of your life,” said Dan Knights, a University of Minnesota assistant professor and the lead author of a study published in December in Genome Medicine. “We have found groups of genes that may play a role in shaping the development of imbalanced gut microbes.”
Doctors have known for years that IBD has a genetic component. But it is the genes’ impact on the gut bacteria that the study shed new light on.
The joint study by researchers at five universities looked at 474 adults in Boston, Toronto and the Netherlands with one of the two diseases. It showed that the subjects’ DNA was linked to the bacteria in their intestines. Those with IBD had a different balance of bacteria in their gut and more “opportunistic” pathogens, or “bad” bacteria.
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Dr. Balfour Sartor, who was not involved in the study, called its results “quite significant.”
“They looked at all the 163 genes associated with IBD, especially those that govern the immune response, and demonstrated genetic associations with resident intestinal bacteria,” said Sartor, a gastroenterologist and professor at the University of North Carolina in Chapel Hill. “It doesn’t prove that genes and bacteria cause IBD, but it proves an association between these two contributors to these diseases.”
Crohn’s disease and ulcerative colitis can develop at any age, though they begin most commonly between 15 and 30, he said. Consequently, by the time they are in their 50s and 60s, those with the diseases have been struggling to cope with them for decades. Dwight Eisenhower had Crohn's disease and underwent surgery during his presidency; Mike McCready, the 48-year-old lead guitarist for Pearl Jam, has lived with it for 25 years, he writes.
Like asthma and rheumatoid arthritis, IBD is related to an out-of-whack immune response. The immune system treats bacteria and food in the intestines as if they were harmful invaders. That overreaction causes inflammation.
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And like those other diseases, the incidence of Crohn's disease and ulcerative colitis has increased greatly over the decades, said Sartor, who also serves as medical director of the Broad Medical Research Program at the Crohn’s & Colitis Foundation of America.
Immunosuppressive medications are the current treatment. When they are not effective, surgery may be necessary — but unlike in past decades, the numbers of patients who must wear a permanent ileostomy bag has dropped dramatically, Sartor said.
In most cases, if the colon has to be removed because of ulcerative colitis, surgeons can now create an internal pouch made from the small intestine that is attached to the rectum, he said.
Do You Have IBD?
An estimated 1.6 million people in the United States have Crohn’s disease or ulcerative colitis, according to the Crohn’s & Colitis Foundation of America.
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Not to be confused with the less-serious irritable bowel syndrome, or spastic colon, Crohn’s and colitis are both characterized by inflammation of the intestine. See your doctor if you have these symptoms, the Crohn’s & Colitis Foundation says:
Crohn’s Disease (usually affects the small bowel and beginning of the colon):
- Persistent diarrhea
- Rectal bleeding
- Abdominal pain and cramps
- Urgent need to move bowels
- Feeling the bowel movement isn’t complete
Ulcerative colitis (affects the large intestine or colon):
- Looser and more urgent bowel movements
- Persistent diarrhea with blood in stool
- Abdominal pain and cramps
Those suffering from either disease may lose their appetite and lose weight. You may also feel tired and low in energy.
The good news: Research continues.
“In many cases, we’re still learning how these (gut) bacteria influence our risk of disease, but understanding the human genetics component is a necessary step in unraveling the mystery,” Knights said.