A look at proteins reveals inflammation invisible even under a microscope
By Amy Ratner, Director Scientific Affairs
People with celiac disease who seem to be doing well on a gluten-free diet may have on-going, low-level intestinal inflammation, according to a new study that looked at complete protein profiles in biopsy samples.
“Our findings raise the question whether a standard gluten-free diet is sufficient to curb the gluten-specific immune response in all celiac disease patients,” the study says.
Researchers at the University of Oslo used proteomics, which is analysis of the entire protein complement of a cell, tissue, or organism under a specific, defined set of conditions. They set out to find out why some people with celiac disease who have a healthy intestine according to their biopsy results develop intense inflammation following a short gluten challenge, while others do not.
A gluten challenge is sometimes used in clinical trials testing new drugs to treat celiac disease. It can also be used to confirm a diagnosis of celiac disease.
Researchers looked at biopsies that had been taken from 19 adults with well-controlled celiac disease before and after a 14-day gluten challenge during which the study participants ate one muesli bar with about 6 grams of gluten protein daily. All had been following the gluten-free diet for more than two years and were considered to be “in complete remission.”
Using proteomics analysis, researchers found a range of intestinal reactions to the challenge, with some people with celiac disease showing strong changes in intestinal inflammation and others none. Seven study participants were classified as responding to the gluten challenge and 12 were classified as nonresponders.
T-Cells: White blood cells that function as the body’s disease fighting soldiers and are improperly activated by gluten in those who have celiac disease
The study showed that patients with a strong inflammatory response had signs of ongoing baseline inflammation even before they had the gluten challenge. Additionally, they had increased levels of gluten-specific T-cells in the intestine and a low-level presence of inflammatory proteins in their blood.
These patients may have a “head start” even before the gluten challenge, the study, published in the journal Advanced Science, says.
“It is conceivable that the patients who responded strongly in the challenge trial were not completely healed despite being considered ‘well-treated’ by their gluten-free diet before being enrolled in the trial,” said Jorunn Stamnæs, PhD, lead study author and administrative coordinator of the KG Jebsen Celiac Disease Research Center at the University of Oslo.
The ongoing inflammation found through proteomics is not visible when biopsy samples are examined under a microscope, the study says. Consequently, assessing biopsy samples only with a microscope appears to be insufficient to judge full recovery and intestinal healing in celiac disease patients.
Stamnæs said pre-gluten challenge differences in study participants’ biopsies could be attributed to inadvertent gluten in the gluten-free diet of those who showed protein evidence of intestinal inflammation. Or some patients could have a greater number of dormant gluten-specific T-cells while on the gluten-free diet than others.
“We don’t know which of these explanations are true,” she said, noting that it could be both. Stamnæs and colleagues are now conducting further studies to see if they can find activated T-cells in some patients on the gluten-free diet and if those patients also have signs of low-level intestinal inflammation that can be detected by protein analysis.
If researchers find confirming evidence of these activated T-cells despite a gluten-free diet, it would have implications for celiac disease management, Stamnæs said.
Her research looks for changes in biopsy tissue by examining all the proteins inside and outside cells. “These proteins tell us something about what goes on in the tissue; if all is well or if some or all cells are in a state of alert,” Stamnæs explained. “Our method can discover and measure several important invisible changes, and in the future, this approach may be helpful to set the correct diagnosis or to monitor the effect of treatment in cases with no visible changes in the gut.”
Currently, analysis of biopsies at the protein level is at an early stage even in research. Stamnæs said the field is developing rapidly and may one day be used for celiac disease diagnosis, particularly when patients have a positive blood test for celiac disease, but biopsy results are unclear. However, this use needs to be investigated further.
Questions about the effectiveness of the gluten-free diet as a complete treatment for celiac disease have been raised in other ways in previous research. Studies have shown that even after two years on the gluten-free diet, 30 to 60 percent of adults with celiac disease have persistent gut damage. Data also suggests that this is true in more than 33 percent of adults regardless of having symptoms or positive blood tests.
Non-responsive celiac disease, which is defined as persistent symptoms, signs or abnormalities typical of the condition despite 6 to 12 months of strict adherence to a gluten-free diet, affects up to 30 percent of patients, according to a 2020 study. Thirty four to 64 percent of celiac disease patients have intestinal healing two years after diagnosis, the study says, increasing to 66 to 85 percent in five years. However, some patients never achieve complete resolution of intestinal inflammation, according to the study.
A 2017 study by researchers at the University of Chicago Celiac Center found that even after more than two years on the gluten-free diet about 60 percent of children and adults have ongoing non-gastrointestinal symptoms. Short stature, fatigue and headache were most common in children, while iron deficiency anemia, fatigue, headaches and psychiatric symptoms were most common in adults
A 2016 study of children with celiac disease found one in five may not heal despite following the gluten-free diet for at least a year. The children, who were seen between 2008 and 2015, also had a follow-up biopsy at least 12 months after starting a gluten-free diet. The study found that 19 percent had persistent intestinal damage when the second biopsy was done.
You can read more from the study here.