Marker for inflammatory bowel disease linked to bipolar disorder

By Lucy Piper, Senior medwireNews Reporter

Researchers have found evidence that the gastrointestinal (GI) tract plays a role in the inflammatory pathology of bipolar disorder, suggesting the need to consider dietary modification and anti-inflammatory treatment for some patients.

Their results showed that elevated levels of anti-Saccharomyces cerevisiae antibodies (ASCA; a GI inflammation marker) were associated with a 3.5–4.4-fold increased risk for bipolar disorder, irrespective of what medications were being taken.

ASCA levels in the 264 bipolar disorder patients, 38 of whom had a recent onset of psychosis, were between 2.5 and 3.0 mean-normalized absorbance at 405 nm, compared with 1.0 in the 207 mentally healthy individuals.

Moreover, ASCA levels in patients correlated strongly with immunoglobulin G against wheat gluten and bovine milk caseins. These associations were particularly strong in patients with bipolar disorder who also reported GI symptoms, such as gastroesophageal reflux disease.

These findings support previous theories that compromised endothelial barriers in patients with bipolar disorder may allow exorphins, the by-products of gluten and casein digestion, to enter into systemic circulation and impact brain physiology through action at opioid receptors, the researchers, led by Emily Severance (Johns Hopkins University School of Medicine, Baltimore, Maryland, USA), explain.

However, the team also notes that as ASCA levels correlated with antibodies to food antigens in those with and without GI symptoms, there may be a nonspecific immune response occurring.

To investigate this further, they looked at correlations between ASCA levels and non-food-related antigens, including measles and Toxoplasma gondii, and found significant correlations in patients with bipolar disorder, but only those with recent onset psychosis.

“Although our findings require further scrutiny and larger sample sizes, the possibility of a more generalized inflammatory nature inherent to earlier stages of disease cannot be discounted,” Severance et al write in Bipolar Disorders.

They believe that the serologic markers and their inter-associations could help to identify patients with bipolar disorder who may be at risk for GI- and food-based sensitivities.

And they recommend: “Treatment strategies that involve dietary modifications, anti-inflammatory agents and/or microbiota modulations should be evaluated for effects on symptom improvement in carefully controlled clinical trials.”

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