New Study Shows Fatty Acids May Help or Hurt Patients with Crohn's Disease
December 4, 2015
Genetics and fatty acids may play a part in alleviating or worsening Crohn’s disease.
A new study from Duke University has found genetic similarities between people predisposed to Crohn’s disease and people with a specific profile of fatty acids in their blood.
Dennis Ko, an author of the study and molecular genetics professor at the Duke University School of Medicine, used an analytics software called CPAG, which mines genetic data from more than 1,400 genome studies, to show the genetic overlap between Crohn’s and specific fatty acid levels is more than just chance.
Ko and his colleagues then examined a zebrafish model — zebrafish are commonly used in medical research as a model for human organ systems — and found that high levels of an omega-7 acid and low levels of an omega-6 acid were a cause of the gut inflammation associated with Crohn’s disease.
Crohn’s disease, an inflammation of the bowel that can cause severe pain, diarrhea and malnutrition and affects as many as 700,000 Americans, is remarkable in how little scientists know about it. There is no known cure — though doctors prescribe everything from anti-inflammatory drugs to antibiotics to immune suppressants to altered diets to treat it — and doctors are not sure exactly what causes it. Genetics is part of it, but scientists also suggest diet, infections or an overactive immune system may also play a role.
Ko’s study shows that fatty acids and the genetics of how our bodies absorb them could contribute to the severity of Crohn’s disease.
Fatty acids are long chains of carbon atoms capped by an organic acid (carbon with an arrangement of two oxygen atoms and a hydrogen atom). Each carbon atom in the chain can hold two hydrogen atoms, and when all of them do, the fat is “saturated” with hydrogen.
In a saturated fat, all of the carbon atoms in the chain connect with single bonds, but carbons can form double bonds as well. When they form that extra bond, each carbon involved has to get rid of a hydrogen atom to make room, and because each carbon no longer carries two hydrogen atoms, the chain is no longer saturated. These are unsaturated fats. Trans fats are unsaturated fats in which the double bond does not bend the chain.
Each fatty acid has two ends: the acid or alpha end and the carbon tail or omega end. Fatty acids are named by where the first double bond appears in the chain, so an omega-3 fatty acid — often advertised in fish oil — has its first double bond 3 carbons from the omega end of the chain.
The two fatty acids Ko and his colleagues found in the zebrafish study were an omega-6 and the relative of an omega-7. Palmitic acid, the saturated version of omega-7 palmoleic acid, significantly worsened the inflammation in the zebrafish. Palmitic acid is found in meat and dairy products.
Linoleic acid, an omega-6 found in seed and vegetable oils, eased the inflammation. Previous studies have shown that Crohn’s patients generally have lower levels of linoleic acid in their blood.
While other studies must demonstrate the effects of these acids in other animal models and humans before these acids can be included in Crohn’s disease dietary guidelines, the results of this study are a step toward understanding this mysterious disease.
The study was published in the journal Genome Biology.
— Daniel Lane
Daniel Lane covers science, engineering, medicine and the environment in North Carolina.