Brain network topological changes in inflammatory bowel disease: an exploratory study

Inflammatory bowel disease (IBD) is characterized by multiple and complex pathogenic mechanisms that make its etiology unclear. Nevertheless, it is known that the interaction between genetic and adverse environmental factors may reduce the variety of the intestinal microbiota, and this could result in inflammation having effects on the brain functions through the gut-brain axis. In this paper, we assumed possible alterations in the large-scale brain organization in IBD. To test our hypothesis, we analyzed source-reconstructed magnetoencephalography (MEG) signals in resting state condition in 25 patients and 28 healthy controls. Then, we applied the graph theory to evaluate the brain network topology. Finally, to assess whether changes in the whole-brain activity were linked to IBD clinical evolution, we correlated brain network alterations to disease duration. We found that the betweenness centrality (BC) of the left hippocampus was higher in IBD patients as compared to controls, in the gamma frequency band. We observed a negative correlation between topological data and disease duration, with only a trend toward the statistical significance. The hippocampus is a key region in the gut-brain axis, and the chronic intestinal inflammation specifically alters its functioning. In addition, given the large number of glucocorticoid receptors, the hippocampus is highly susceptible to long-term stress, probably explaining the increase of the local BC. Furthermore, the trend toward a negative correlation with disease duration may be interpreted as a brain compensatory mechanism for IBD-related stress. However, although these findings are promising, we need to recruit more patients to clarify their clinical impact.