Elevated Serum Zonulin in IBS Correlates with Stool Frequency in IBS-D

Celiac.com 07/30/2019 - Studies have shown increased intestinal permeability in irritable bowel syndrome. Validating serum biomarkers for altered intestinal permeability in irritable bowel syndrome will facilitate research and pathophysiology-based therapy.

A team of researchers recently set out to measure serum zonulin and intestinal fatty acid binding protein levels in diarrhea-predominant irritable bowel syndrome and constipation-predominant irritable bowel syndrome, and to compare the results with healthy control and celiac disease subjects.

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The research team included Prashant Singh, Jocelyn Silvester, Xinhua Chen, Hua Xu, Veer Sawhney, Vikram Rangan, Johanna Iturrino, Judy Nee, Donald R. Duerksen, and Anthony Lembo. They are variously affiliated with the Division of Gastroenterology, Department of Medicine, Beth Israel Deaconess Medical Center, Boston, United States of America; the Division of Gastroenterology, Hepatology and Nutrition, Boston Children's Hospital, Boston, United States of America; and the Rady Faculty of Health Sciences, University of Manitoba, Winnipeg, Canada.

The team used enzyme-linked immunosorbent assays to measure serum zonulin and intestinal fatty acid binding protein levels in fifty patients with constipation-predominant irritable bowel syndrome, fifty with diarrhea-predominant irritable bowel syndrome, fifty-three with celiac disease, and forty-two healthy control subjects. 

Using the irritable bowel syndrome-symptom severity scale as a gauge, they found that patients with constipation-predominant irritable bowel syndrome and diarrhea-predominant irritable bowel syndrome had higher zonulin levels compared with healthy controls. They also found that zonulin levels in patients with constipation-predominant irritable bowel syndrome and diarrhea-predominant irritable bowel syndrome are comparable to levels in patients with active celiac disease. 

The results showed no correlation between zonulin levels and overall irritable bowel syndrome symptom severity. They did, however, show a positive correlation with weekly stool frequency, and unsatisfactory bowel habits in diarrhea-predominant irritable bowel syndrome. 

Patients with diarrhea-predominant and constipation-predominant irritable bowel syndrome both had lower intestinal fatty acid binding protein levels compared with celiac patients.

In patients with irritable bowel syndrome, serum zonulin is upregulated at levels comparable to those for celiac patients, and match the severity of unsatisfactory bowel habits in diarrhea-predominant irritable bowel syndrome. 

Irritable bowel syndrome patients show no increase in intestinal fatty acid binding protein levels, which likely means no significant increase in enterocyte death.

This is an interesting finding regarding serum zonulin levels in some patients with irritable bowel syndrome, as is the positive correlation with weekly stool frequency, and unsatisfactory bowel habits in diarrhea-predominant irritable bowel syndrome.  

Read more at the United European Gastroenterology Journal; 2019 Jun; 7(5): 709–715.
doi: 10.1177/2050640619826419