Gut-Brain Communication

New Study Explores Gut-Brain Communication with Multimodal MRI Approach

Norman W. Kettner, DC (’80), DACBR, FICC, dean of research and professor emeritus of Logan’s Department of Radiology, contributed to a study titled, “Cine gastric MRI reveals altered gut-brain axis in functional dyspepsia: gastric motility is linked with brainstemcortical fMRI connectivity.” Recently published in Neurogastroenterology & Motility, the study combines magnetic resonance imaging (MRI) assessment of gastric kinematics with measurements of the nucleus tractus solitarii (NTS) located in the brainstem to evaluate how gut-brain axis communication is associated with functional dyspepsia (FD) pathophysiology.

“This is the first study to utilize both our novel, recently validated fourdimensional (4D) cine MRI and brain functional magnetic resonance imaging (fMRI) to analyze stomach function and central processing of gastric afference in FD,” Dr. Kettner said.

Functional dyspepsia, which affects 25 percent of people worldwide, is a disorder of gut-brain interaction that is characterized by a range of bothersome symptoms in the upper digestive tract that are not caused by organic, systemic or metabolic disease. Although it is not well understood, FD could include altered gastric function and gastric myoelectric activity as well as alterations in brain processing, which may be linked to gastric afference.

According to Dr. Kettner, the vagus nerve acts as the primary link in communication between the stomach and brain, carrying both descending motor signals that coordinate movement and ascending sensory information such as pain.

“Previous research has noted altered brain activity and connectivity in patients with FD compared to healthy controls,” Dr. Kettner said. “To gain a better understanding of FD etiology and pathophysiology, we aimed to conduct a deeper investigation into gut-brain axis communication using assessments of gastric kinematics and brain processing of vagal afference.”

Dr. Kettner and his team hypothesized that compared to healthy adults, patients with FD would demonstrate altered antral motility and NTS connectivity to higher cortical regions known for executive and cognitive processing of sensory signaling. They also predicted gastric dysmotility in FD would be linked with NTS connectivity to the same cortical processing brain regions.

Participants with FD as well as age- and sex-matched healthy controls were enrolled in the study. They attended a screening visit, a behavioral assessment session where they completed several clinical questionnaires, and an imaging visit. During the imaging visit, subjects consumed a contrast meal consisting of a mixture of vanilla pudding and blended pineapple. Then they underwent three abdominal scans and three brain scans. Before each scan, subjects were asked to rate their level of abdominal discomfort.

After analyzing the 4D cine stomach images and brain fMRI data, the researchers found: • Propagation velocity of antral peristalsis was significantly lower in patients with FD. • In both groups, the NTS was most strongly connected to the default mode

network (DMN), known for being active when daydreaming or mind wandering. But in patients with FD, the NTS was more connected to the frontoparietal network (FPN), which is involved in sustained attention, working memory and problem solving. • Patients with FD demonstrated higher NTS connectivity to insula, anterior cingulate, prefrontal cortices and the presupplementary motor area. Dr. Norman W. Kettner • NTS connectivity was linked to propagation velocity in healthy controls, while NTS connectivity was linked to peristalsis frequency in patients with FD. “This groundbreaking study is the only one to date that directly links mechanoreceptive gastric afference to brainstem viscerosensory connectivity in patients with FD,” Dr. Kettner said. “These associations suggest that patients suffering from FD show specific plasticity in gut-brain communication, which can be assessed with our multimodal MRI approach.” In addition to providing new insight into FD pathophysiology, Dr. Kettner hopes this study will open the door for future investigations into other functional disorders. “Functional disorders are widespread, but at this point, we have not been able to identify a pathological cause,” Dr. Kettner said. “If we can gain a better understanding, we can develop more effective interventions.” Scan the QR codes below to read the most recent study on FD (left) and the 2021 study on 4D cine MRI (right).