Functional constipation is associated with alterations in thalamo-limbic/parietal structural connectivity

Epidemiology of Disorders of the Gut-Brain Interaction: An Appraisal of the Rome IV Criteria and Beyond

Disorders of the gut-brain interaction (DGBIs) are presently classified into mutually exclusive anatomical area-related symptom-based categories according to the Rome IV criteria. The pathophysiology of visceral nociception, which contributes to the wide range of symptoms of DGBIs, involves complex psychobiological processes arising from the bidirectional interactions of multiple systems at the gut and brain levels, which affect symptom expression and illness behaviors. The attitude toward an illness and expression of pain and bowel habit vary across cultures with variable interpretation based on sociocultural beliefs, which may not tally with the medical definitions. Thus, psychological factors impact DGBI definitions, their severity and health care utilization. Due to the poor localization and multisegment referral of visceral pain, the anatomical site of pain may not correspond to the affected segment, and there may be a variable degree of overlap among symptoms. The somewhat restrictively defined Rome IV criteria assume one-to-one correlation of symptoms with underlying pathophysiology and ignore overlapping DGBIs, nonstandardized symptom categories, and change or shift in category over time. The microorganic nature of DGBIs resulting from systemic, metabolic or motility disorders, gut dysbiosis and inflammation are not addressed in the Rome IV criteria. Although there is a multidimensional clinical profile that does address these factors, it is not followed rigorously in practice. Threshold changes for diagnostic criteria or addition/deletion of symptoms leads to wide variation among different DGBI criteria resulting in uncertain comparability of results. Although the Rome IV criteria are excellent for research studies and therapeutic trials in homogenous populations, further improvement is needed for their wider applicability in clinical practice.

The role of the gut microbiome in disorders of gut-brain interaction

Disorders of Gut-Brain Interaction (DGBI) are widely prevalent and commonly encountered in gastroenterology practice. While several peripheral and central mechanisms have been implicated in the pathogenesis of DGBI, a recent body of work suggests an important role for the gut microbiome. In this review, we highlight how gut microbiota and their metabolites affect physiologic changes underlying symptoms in DGBI, with a particular focus on their mechanistic influence on GI transit, visceral sensitivity, intestinal barrier function and secretion, and CNS processing. This review emphasizes the complexity of local and distant effects of microbial metabolites on physiological function, influenced by factors such as metabolite concentration, duration of metabolite exposure, receptor location, host genetics, and underlying disease state. Large-scale in vitro work has elucidated interactions between host receptors and the microbial metabolome but there is a need for future research to integrate such preclinical findings with clinical studies. The development of novel, targeted therapeutic strategies for DGBI hinges on a deeper understanding of these metabolite-host interactions, offering exciting possibilities for the future of treatment of DGBI.

Regional homogeneity alterations in patients with functional constipation and their associations with gene expression profiles

Functional constipation, a highly prevalent functional gastrointestinal disorder, often accompanies by mental and psychological disorders. Previous neuroimaging studies have demonstrated brain functional and structural alterations in patients with functional constipation. However, little is known about whether and how regional homogeneity is altered in these patients. Moreover, the potential genetic mechanisms associated with these alterations remain largely unknown. The study included 73 patients with functional constipation and 68 healthy controls, and regional homogeneity comparison was conducted to identify the abnormal spontaneous brain activities in patients with functional constipation. Using Allen Human Brain Atlas, we further investigated gene expression profiles associated with regional homogeneity alterations in functional constipation patients with partial least squares regression analysis applied. Compared with healthy controls, functional constipation patients demonstrated significantly decreased regional homogeneity in both bilateral caudate nucleus, putamen, anterior insula, thalamus and right middle cingulate cortex, supplementary motor area, and increased regional homogeneity in the bilateral orbitofrontal cortex. Genes related to synaptic signaling, central nervous system development, fatty acid metabolism, and immunity were spatially correlated with abnormal regional homogeneity patterns. Our findings showed significant regional homogeneity alterations in functional constipation patients, and the changes may be caused by complex polygenetic and poly-pathway mechanisms, which provides a new perspective on functional constipation's pathophysiology.

Altered intrinsic functional brain architecture in patients with functional constipation: a surface-based network study

Background

Functional constipation (FCon) is a common functional gastrointestinal disorder (FGID). Studies have indicated a higher likelihood of psychiatric disorders, such as anxiety, depression, sleep disturbances, and impaired concentration, among patients with FCon. However, the underlying pathophysiological mechanisms responsible for these symptoms in FCon patients remain to be fully elucidated. The human brain is a complex network architecture with several fundamental organizational properties. Neurological interactions between gut symptoms and psychiatric issues may be closely associated with these complex networks.

Methods

In the present study, a total of 35 patients with FCon and 40 healthy controls (HC) were recruited for a series of clinical examinations and resting-state functional magnetic imaging (RS-fMRI). We employed the surface-based analysis (SBA) approach, utilizing the Schaefer cortical parcellation template and Tikhonov regularization. Graph theoretical analysis (GTA) and functional connectivity (FC) analysis of RS-fMRI were conducted to investigate the aberrant network alterations between the two groups. Additionally, correlation analyses were performed between the network indices and clinical variables in patients with FCon.

Results

At the global level, we found altered topological properties and networks in patients with FCon, mainly including the significantly increased clustering coefficient (CP), local efficiency (Eloc), and shortest path length (LP), whereas the decreased global efficiency (Eglob) compared to HC. At the regional level, patients with FCon exhibited increased nodal efficiency in the frontoparietal network (FPN). Furthermore, FC analysis demonstrated several functional alterations within and between the Yeo 7 networks, particularly including visual network (VN), limbic network (LN), default mode network (DMN), and somatosensory-motor network (SMN) in sub-network and large-scale network analysis. Correlation analysis revealed that there were no significant associations between the network metrics and clinical variables in the present study.

Conclusion

These results highlight the altered topological architecture of functional brain networks associated with visual perception abilities, emotion regulation, sensorimotor processing, and attentional control, which may contribute to effectively targeted treatment modalities for patients with FCon.

U-shaped association between sleep duration with chronic constipation and diarrhea: A population-based study

To examine the association between sleep duration with chronic constipation and diarrhea, we collected demographic and questionnaire data of participants from The National Health and Nutrition Examination Survey in the period 2005 to 2010. A restricted cubic spline curve function was used to determine the association between sleep duration and chronic constipation or diarrhea. Multivariate logistic regression models were used to estimate the association between sleep duration groups and chronic constipation or diarrhea. 14,054 eligible participants were included in this study. Among all sleep durations, 7 hours sleep per day had the highest percentage of normal stool forms (86.3%, P < .001), while people with ≤4 hours sleep had a higher number of bowel movements per week (P < .001). RCS models demonstrated a significant nonlinear association between sleep duration and risk of chronic constipation (P < .001). The inflection points of the U-shaped association curve corresponded to 7 hours of sleep per day. Multivariate logistic regression indicated that compared to participants with 7 hours daily sleep duration, participants with ≤4 hours and ≥10 hours sleep duration had a 54% (95%CI: (1.16-2.04), P = .002) and 90% (95%CI: (1.33-2.72), P < .001) higher risk of constipation, respectively. There is a non-linear association between sleep duration and the risk of chronic constipation. Our findings indicate that both shorter and longer sleep duration are associated with an increased risk of constipation.

Intra and inter: Alterations in functional brain resting-state networks in patients with functional constipation

Background

Functional constipation (FCon), is a symptom-based functional gastrointestinal disorder without an organic etiology and altering brain structure and function. However, previous studies mainly focused on isolated brain regions involved in brain plasticity. Therefore, little is known about the altered large-scale interaction of brain networks in FCon.

Methods

For this study, we recruited 20 patients with FCon and 20 healthy controls. We used group independent component analysis to identify resting-state networks (RSNs) and documented intra- and inter-network alterations in the RSNs of the patients with FCon.

Results

We found 14 independent RSNs. Differences in the intra-networks included decreased activities in the bilateral caudate of RSN 3 (strongly related to emotional and autonomic processes) and decreased activities in the left precuneus of RSN 10 (default mode network). Notably, the patients with FCon exhibited significantly decreased interactive connectivity between RSNs, mostly involving the connections to the visual perception network (RSN 7–9).

Conclusion

Compared with healthy controls, patients with FCon had extensive brain plastic changes within and across related RSNs. Furthermore, the macroscopic brain alterations in FCon were associated with interoceptive abilities, emotion processing, and sensorimotor control. These insights could therefore lead to the development of new treatment strategies for FCon.

White-matter microstructural alterations in patients with functional constipation: A tract-based spatial statistics study

BACKGROUND

Highly prevalent functional constipation (FC) belongs to the category of functional gastrointestinal disorders. Neuroimaging studies have demonstrated brain functional and morphometric changes in patients with FC. However, whether FC is associated with white-matter (WM) microstructural alterations remains unclear.

METHODS

Diffusion tensor imaging (DTI) and tract-based spatial statistics (TBSS) were introduced to investigate WM microstructural changes as calculated by fractional anisotropy (FA), mean (MD), axial (AD), and radial diffusivity (RD) in 26 FC patients and 31 healthy controls.

KEY RESULTS

Patients with FC relative to healthy controls had significantly decreased FA with increased MD/RD in the genu (GCC) and body (BCC) of the corpus callosum, right cingulum (Cing), bilateral anterior corona radiata (ACR), bilateral superior corona radiata (SCR), and left posterior corona radiata (PCR) (p_FWE  < 0.05). Between-group difference was only in the left SCR and PCR when regressing out anxiety and depression as covariates.

CONCLUSIONS AND INFERENCES

These WM tracts are mainly responsible for sensory and emotional information communication and corresponding functional integration; thus, our findings indicate an association between FC and WM microstructural abnormalities in regions involved with visceral afferent and emotional-arousal processing. Alterations in WM microstructures including the CC, cingulum, and ACR are more related to psychological symptoms than constipation, which might have greater impact on brain structures.

Altered Functional Connectivity Within and Between Salience and Sensorimotor Networks in Patients With Functional Constipation

Functional constipation (FCon) is a common functional gastrointestinal disorder. A considerable portion of patients with FCon is associated with anxiety/depressive status (FCAD). Previous neuroimaging studies mainly focused on patients with FCon without distinguishing FCAD from FCon patients without anxiety/depressive status (FCNAD). Differences in brain functions between these two subtypes remain unclear. Thus, we employed resting-state functional magnetic resonance imaging (RS-fMRI) and graph theory method to investigate differences in brain network connectivity and topology in 41 FCAD, 42 FCNAD, and 43 age- and gender-matched healthy controls (HCs). FCAD/FCNAD showed significantly lower normalized clustering coefficient and small-world-ness. Both groups showed altered nodal degree/efficiency mainly in the rostral anterior cingulate cortex (rACC), precentral gyrus (PreCen), supplementary motor area (SMA), and thalamus. In the FCAD group, nodal degree in the SMA was negatively correlated with difficulty of defecation, and abdominal pain was positively correlated with nodal degree/efficiency in the rACC, which had a lower within-module nodal degree. The salience network (SN) exhibited higher functional connectivity (FC) with the sensorimotor network (SMN) in FCAD/FCNAD, and FC between these two networks was negatively correlated with anxiety ratings in FCAD group. Additionally, FC of anterior insula (aINS)-rACC was only correlated with constipation symptom (i.e., abdominal pain) in the FCNAD group. In the FCAD group, FCs of dorsomedial prefrontal cortex-rACC, PreCen-aINS showed correlations with both constipation symptom (i.e., difficulty of defecation) and depressive status. These findings indicate the differences in FC of the SN-SMN between FCAD and FCNAD and provide neuroimaging evidence based on brain function, which portrays important clues for improving new treatment strategies.

Disrupted Regional Homogeneity in Major Depressive Disorder With Gastrointestinal Symptoms at Rest

Background: Gastrointestinal (GI) symptoms are prominent in patients with major depressive disorder (MDD). Previous studies have reported brain structural and functional changes in both MDD and digestive system diseases but it remains unclear whether MDD patients with GI symptoms have brain imaging changes. Methods: We recruited 35 MDD patients with GI symptoms, 17 MDD patients without GI symptoms and 28 age-, gender-, and education-matched healthy controls. All participants were scanned by resting-state functional magnetic resonance imaging (fMRI). Imaging data were analyzed with regional homogeneity (ReHo). Results: The GI group showed higher total HRSD-17 scores, anxiety/somatization, weight loss, and sleep disturbance scores compared to the non-GI group. We found increased ReHo in the right inferior parietal gyrus (IPL), bilateral supplementary motor area (SMA), bilateral cerebellum Crus II, left inferior frontal gyrus (IFG), and bilateral superior medial frontal cortex (SMFC) and decreased ReHo in the right posterior cingulate cortex (PCC), bilateral cuneus, and left middle occipital gyrus (MOG) in patients with GI symptoms relative to the HCs. The GI group showed higher ReHo values in the bilateral precuneus than the non-GI group. Conclusion: MDD patients with GI symptoms showed a greater severity of symptoms than MDD patients without GI symptoms, particularly in terms of anxiety/somatization, weight loss, and sleep disturbances. Increased activity in the default-mode network might be associated with GI symptoms in MDD patients.