The study used STC-1 cells, a mouse intestinal secretion cell line described by the researchers as a stable model of native enteroendocrine cells and a commonly used model for CCK secretion. These cells possess characteristics of enteroendocrine cells, and their secretion is linked to increased intracellular calcium. The team measured transmembrane currents with whole-cell patch clamping and used Fura-2 fluorescence at excitation wavelengths of 340 and 380 nanometres to monitor intracellular calcium. CCK released into the culture medium was quantified by ELISA, while immunofluorescence, Western blotting and RT-qPCR assessed protein expression and CCK messenger RNA. Animal work used male C57BL/6 mice aged 6 to 8 weeks. Mice were randomly assigned to control, wrap restraint stress, TRPV4-blocker, NCX1-blocker or CCK-receptor-blocker groups, and data collection and evaluation were performed blind.

Carbachol, a stable analogue of acetylcholine used to stimulate muscarinic receptors, increased transmembrane current and intracellular calcium in STC-1 cells. The current-voltage relationship had a reversal potential near 0 millivolts, consistent with activation of non-selective cation channels, and the measured half-maximal effective concentration of carbachol for the calcium response was about 15 micromolar. The inositol trisphosphate receptor blocker 2-aminoethyl diphenylborinate at 100 micromolar reduced the carbachol-induced current, while xestospongin C at 100 nanomolar also suppressed the current increase. Pretreatment with 2-aminoethyl diphenylborinate also reduced the rise in intracellular calcium. The Orai1 blocker GSK7975A at 10 micromolar inhibited both the enhanced current and calcium response. Together, these observations support involvement of intracellular-store calcium release through IP3 receptors and Orai1-associated signaling in the response to muscarinic stimulation.

TRPV4 protein was detected in STC-1 cells by immunofluorescence and Western blotting. Two TRPV4 agonists, RN-1747 at 20 micromolar and GSK1016790A at 100 nanomolar, increased non-selective cation current and intracellular calcium. Both effects were suppressed by the TRPV4 blocker HC067047 at 10 micromolar. HC067047 also strongly reduced the membrane current and calcium increase induced by 20 micromolar carbachol. These results establish that TRPV4 is expressed and functionally active in this cell model and that it participates in the cholinergic calcium response. They do not establish TRPV4 as the sole or principal membrane channel responsible for that response.

The investigators likewise found evidence for the involvement of NCX1. Raising extracellular calcium with 5 millimolar CaCl2 produced an increase in membrane current that was inhibited by the reverse-mode NCX1 inhibitors KB-R7943 at 30 micromolar and SN6 at 10 micromolar. NCX1 protein was detected in STC-1 cells by immunofluorescence and Western blotting. In cholinergic-stimulation experiments, both KB-R7943 and SN6 reduced the carbachol-induced non-selective cation current, and pretreatment with either compound reduced the associated calcium signal. The findings indicate that reverse-mode NCX1 participates in the membrane-current and calcium-signaling response to carbachol in STC-1 cells.

Experiments designed to link the two proteins provided further evidence of functional coupling. Activating TRPV4 with either RN-1747 or GSK1016790A increased membrane current and intracellular calcium, while pretreating cells with SN6 suppressed both responses. Co-immunoprecipitation detected an interaction between TRPV4 and NCX1 proteins in STC-1 cells. The electrophysiological and imaging results therefore showed functional interdependence, while the co-immunoprecipitation result provided evidence of physical association. On the basis of these observations, the researchers proposed that TRPV4 and NCX1 form a coupled module that supports the elevated calcium signal and calcium-dependent CCK secretion. The experiments do not define the precise molecular steps of that interaction or demonstrate that the two proteins constitute the only route to hormone release.

The hormone link was tested directly by measuring CCK in STC-1 culture supernatants. Carbachol at 20 micromolar significantly increased CCK secretion relative to the control condition. The carbachol-associated increase was markedly suppressed by the TRPV4 inhibitor HC067047 and by the NCX1 inhibitors KB-R7943 and SN6. Thus, TRPV4 and NCX1 were not associated only with generic changes in membrane current or calcium; their inhibition also reduced a measured secretory response. The cellular results place both proteins upstream of part of the carbachol-dependent CCK response under the conditions tested. They do not directly establish that a stress-induced increase in vagal acetylcholine release drives the same sequence in the intact animals.

In the animal experiment, the investigators applied wrap restraint stress for seven consecutive days to male mice as an IBS-D model. After stress, CCK transcription was significantly higher in the duodenum and colon than in controls. Intraperitoneal HC067047 at 10 milligrams per kilogram, KB-R7943 at 20 milligrams per kilogram and the CCK receptor antagonist devazepide at 1 milligram per kilogram each suppressed the stress-associated increase in these transcripts. The study also examined fecal outcomes. Before restraint, there were no significant differences among groups in fecal number, weight or water content. After restraint, mice had significantly more fecal particles, greater fecal weight and increased fecal water content. Administration of each blocker significantly restored these three measures toward control levels, according to the reported results for groups of six mice.

The study provides experimental support for a TRPV4–NCX1–calcium–CCK pathway in intestinal enteroendocrine cells and associates that pathway with diarrhea-like outcomes in a stress-based mouse model. The authors described TRPV4 and NCX1 as potential targets for preventing or treating IBS-D, but that proposal remains preclinical. The evidence comes from one immortalized intestinal cell line and one established mouse model rather than patients with IBS. Female mice were excluded because hormonal cycles could interfere with the stability of the model, leaving the relevance of the results to female mice unresolved. TRPV4 and NCX1 are also present in other gastrointestinal cell types, and the study did not determine whether enteroendocrine-cell-specific deletion would reproduce or prevent the observed fecal effects. Other enteroendocrine hormones, including GLP-1 and PYY, were not assessed as contributors. Human tissue samples, patient cohorts and clinical outcomes were not studied, so the results offer a testable mechanism for IBS-D biology rather than evidence of a diagnostic, preventive or therapeutic benefit in people.

Subject of Research: TRPV4–NCX1 coupling, calcium-dependent CCK secretion and IBS-D-like diarrhea in male mice

Article Title: TRPV4/NCX1 coupling regulates Ca2+‐dependent cholecystokinin secretion from enteroendocrine cells to involve the pathogenesis of irritable bowel syndrome‐diarrhea in male mice

Article References: Wang, J., Chen, X., Tong, S., Qu, C., Lu, W., & Dong, H. (2026). TRPV4 / NCX1 coupling regulates Ca 2+ ‐dependent cholecystokinin secretion from enteroendocrine cells to involve the pathogenesis of irritable bowel syndrome‐diarrhea in male mice. Physiological Reports, 14(20), Article e71149. https://doi.org/10.14814/phy2.71149

Image Credits: AI Generated

DOI: 10.14814/phy2.71149

Keywords: TRPV4, NCX1, cholecystokinin, enteroendocrine cells, calcium signaling, irritable bowel syndrome, IBS-D, male mice, wrap restraint stress, coupling, regulates, dependent

Researchers assessed 298 symptomatic patients and diagnosed IBS using the Rome IV criteria, identifying 197 cases, or 66.1% of the cohort. Stool examinations found Blastocystis in 57 of those 197 patients, an infection prevalence of 28.9% within the IBS group. Parasite identification was performed by direct microscopy, while PCR with subtype-specific sequence-tagged site primers was used to classify the infections. These procedures detected two subtypes: subtype 3 accounted for 86% of Blastocystis-positive cases, and subtype 1 accounted for the remaining 14%.

To compare inflammatory responses, the investigators used a balanced random selection of 57 Blastocystis-positive IBS patients and an equal number of randomly chosen Blastocystis-negative IBS patients. Mean serum IL-8 concentration was 129.24 ± 56.28 pg/mL in the infected group, compared with 26.28 ± 9.28 pg/mL in the uninfected group. The difference was statistically significant at P < 0.001, indicating substantially elevated circulating IL-8 among the Blastocystis-positive participants. IL-8 is a chemokine involved in pro-inflammatory immune activity, making the association relevant to research on how intestinal infections may intersect with immune activation in functional gastrointestinal disorders.

The subtype analysis did not show that IL-8 concentrations differed significantly between subtype 3 and subtype 1, even though subtype 3 produced the numerically higher value. That distinction matters because subtype 3 was the predominant strain in this sample, but the study did not demonstrate a unique IL-8 response to that subtype. The authors therefore described the results as evidence of an association between Blastocystis infection and higher IL-8 in IBS rather than proof of a subtype-specific inflammatory effect.

Multivariable analysis identified younger age, diarrhea, and presentation during spring as independent predictors of Blastocystis infection. These variables were associated with the likelihood that an IBS patient carried the parasite; they do not establish that any of them caused infection or directly produced gastrointestinal symptoms. The sample was drawn from a single tertiary clinic and included symptomatic patients rather than a population-based control group. The cross-sectional comparison, modest number of infected participants, lack of longitudinal follow-up and absence of direct measurements of inflammation within the intestinal mucosa further constrain conclusions about causality.

The results add evidence to a continuing debate over whether Blastocystis has a meaningful role in IBS pathogenesis. The concentration of infections in a patient group with functional gastrointestinal symptoms and the accompanying difference in IL-8 are compatible with a potential aggravating influence, but the current data cannot establish that blastocystosis causes or worsens IBS. Distinguishing the effects of infection, subtype, host immunity, symptom pattern and other clinical characteristics will require mechanistic work and prospective studies.

The researchers also called for evaluation of local inflammatory markers to investigate immune modulation within the gut and identify molecular effectors that might connect Blastocystis with IBS. Such work would help determine whether the elevated serum IL-8 observed here reflects local intestinal activity, a broader systemic response, or another feature of the affected patients. Until those questions are resolved, the findings support a measured conclusion: Blastocystis was common among these IBS patients, subtype 3 predominated, and infection was associated with higher circulating IL-8, but the direction and mechanism of the relationship remain uncertain.

Subject of Research: Association between Blastocystis infection, subtype distribution and serum IL-8 in patients with irritable bowel syndrome

Article Title: Association of Blastocystis subtype 3 with elevated IL-8–mediated inflammation in patients with irritable bowel syndrome

Article References: Morsy, S. M., Abdeltawab, M. S. A., Mahfoz, A. M., Elkerdawy, M. A., Sallam, H. S., & Ismail, A. R. (2026). Association of Blastocystis subtype 3 with elevated IL-8–mediated inflammation in patients with irritable bowel syndrome. Gut Pathogens. https://doi.org/10.1186/s13099-026-00887-5

Image Credits: AI Generated

DOI: 10.1186/s13099-026-00887-5

Keywords: Blastocystis, irritable bowel syndrome, IL-8, intestinal parasites, inflammation, gut immunity, PCR, subtype 3, cross-sectional study, Association, subtype, elevated

The authors are careful to define their terms. Personality, in this context, refers to relatively consistent patterns of thinking, feeling, and behaving that persist across time and situations, not temporary emotional states, acute stress, or passing mood changes. This distinction matters because decades of research have already linked transient stress to reproductive difficulties, with mixed and often inconsistent results. What the Romanian team proposes is something different: that the neurobiological architecture underlying traits such as neuroticism, extraversion, or harm avoidance produces stable, individual differences in how the autonomic nervous system, the hypothalamic-pituitary-adrenal (HPA) axis, and inflammatory pathways operate. Those same regulatory systems happen to be deeply involved in digestion and in reproduction, raising the possibility that personality-related biology and reproductive biology are two faces of the same underlying physiology.

Personality neuroscience has matured considerably over the past two decades. Traits are no longer viewed as purely descriptive psychological labels but as neurobehavioral characteristics rooted in distributed brain networks governing reward processing, emotional regulation, salience detection, and executive control. Dimensional models, particularly the Big Five framework, describe normal-range variation in these traits across the general population. Crucially, studies have associated these traits with measurable physiological differences: variation in HPA-axis reactivity and cortisol dynamics, distinct patterns of autonomic nervous system activity, differences in chronic low-grade inflammation, and even the severity of dermatological conditions such as atopic dermatitis. These are observational associations rather than proven causal mechanisms, but they establish that personality is biologically embodied, not confined to the skull.

The first leg of the proposed framework runs through the gut. The brain-gut axis is a well-established bidirectional communication network linking the central nervous system to the digestive tract through neural, hormonal, and immune signaling. It regulates motility, secretion, and visceral sensitivity, and it is influenced by higher-order brain processes. Research on functional gastrointestinal disorders, particularly irritable bowel syndrome, has repeatedly found that traits such as neuroticism are associated with altered bowel habits, visceral hypersensitivity, and greater symptom severity. Meanwhile, the gut microbiota has emerged as a powerful mediator between brain and body: dysbiosis, or microbial imbalance, has been linked to altered gut signaling and to systemic metabolic, immune, and endocrine changes. Some of those changes, the review notes, may also be relevant to reproductive function, although a direct personality-microbiota-reproduction pathway remains speculative and confounded by diet, medication, and lifestyle factors.

The second leg runs through the reproductive system, which is governed by the hypothalamic-pituitary-gonadal (HPG) axis in concert with autonomic nerves and peripheral endocrine signals. Here the evidence is more fragmentary but intriguing. Personality-related factors have been linked to variations in libido, erectile function, and ejaculatory control in men, including premature ejaculation, and to differences in sexual arousal, satisfaction, and response patterns in women. Autonomic disturbances, for their part, have been associated with male infertility, providing one plausible mechanistic bridge. A systematic review of 23 studies identified neuroticism, harm avoidance, and psychoticism as recurring characteristics in psychological adjustment to infertility, and a more recent comparative study found that infertile couples scored higher on neuroticism and psychoticism, with greater sensory sensitivity and more interpersonal and sexual conflict than fertile couples.

The authors are emphatic, however, that such findings do not establish causation, and they devote considerable attention to the problem of directionality. Pre-existing personality characteristics may shape how people respond to infertility, but infertility itself, with its prolonged treatments, sexual difficulties, relationship strain, and uncertainty about parenthood, may also alter personality-related measurements. Common factors such as age, socioeconomic conditions, comorbidities, and psychological distress could confound both sides of the equation. A Mendelian randomization study exploring causality between neuroticism clusters and female reproductive diseases in European populations reported associations, but the biological mechanisms and direction of these relationships remain uncertain. The review therefore treats behavioral associations, fertility outcomes, and directly measured reproductive physiology as distinct tiers of evidence rather than folding them into a single causal story.

Several biological pathways could, in principle, connect the dots. Personality traits have been associated with differences in HPA-axis activity, and cortisol dysregulation has been investigated in relation to infertility, though findings remain inconsistent. Interactions between the HPA and HPG axes represent a plausible point of convergence, since stress hormones can suppress gonadal function. The relationship may also run in reverse: sex steroids influence brain development and neural function, meaning reproductive endocrine activity can shape personality-related neurobehavioral phenotypes rather than personality acting only upstream. Hypothalamic glial cells, including microglia, participate in inflammatory and metabolic signaling that modulates neuroendocrine regulation. Eating behavior offers yet another convergence point, since metabolic status influences ovulatory function in women and spermatogenesis in men. Polycystic ovary syndrome, which the authors suggest renaming polyendocrine metabolic ovarian syndrome, provides a clinical example where reproductive endocrine dysfunction and distinct personality and temperamental profiles appear together.

The methodology behind the review was systematic. The authors searched PubMed/MEDLINE, Scopus, Web of Science, and Google Scholar for peer-reviewed English-language publications from 2000 to 2026, combining MeSH terms related to personality traits, the brain-gut axis, gut microbiota, autonomic regulation, the HPA and HPG axes, sexual function, and infertility. Of 70 potentially relevant records, 37 were included in the final narrative synthesis after screening. The team explicitly graded their evidence into three levels: established biological relationships supported by mechanistic data, empirical associations between personality and physiological outcomes, and hypothetical cross-system connections proposed within the new framework. Only the first level rests on solid physiological ground; the third, the Brain-Gut-Gonadal integration itself, is presented as hypothesis-generating rather than as a newly discovered biological axis.

What would it take to test the hypothesis? The authors outline a research agenda centered on longitudinal cohort studies that track whether personality traits prospectively predict gastrointestinal, sexual, and reproductive outcomes over time. Studies combining neuroimaging, autonomic assessment, HPA- and HPG-axis measures, inflammatory markers, and reproductive hormones could identify where these systems genuinely converge. Most importantly, comparisons between individuals with unexplained infertility, explained infertility, and fertile controls could reveal whether specific traits correlate with measurable differences in autonomic activity, cortisol dynamics, reproductive hormones, sexual function, or gut microbiota composition. Such designs would directly test, rather than assume, whether personality-related biological variability matters for unexplained infertility, the clinical frontier where the framework could have its greatest impact.

The verdict, for now, is deliberately cautious. The available evidence is heterogeneous, predominantly associative, and vulnerable to confounding and reverse causality, and the proposed framework has not been validated in longitudinal or experimental studies. The authors do not claim that internal organs possess personalities or that traits cause infertility. What they offer is a unifying lens: shared neurobiological and neuroendocrine mechanisms may produce parallel functional response patterns across the brain, the gut, and the gonads, patterns that happen to reflect an individual’s personality. If future studies confirm that personality-related biological differences contribute to variation in reproductive physiology, unexplained infertility, one of medicine’s most frustrating diagnostic categories, may finally gain a new explanatory dimension. Until then, the Brain-Gut-Gonadal axis remains exactly what its authors intend: a bold, testable idea awaiting its experimental verdict.

Subject of Research: The proposed brain-gut-gonadal axis linking personality traits to reproductive physiology and unexplained infertility

Article Title: Personality beyond the brain: a new perspective on the brain-gut-gonadal axis and human fertility

Article References: Doroftei, B., Kamar, A. A. M., Ciobica, A., Puia, D., Doroftei, M., Puha, D., & Puha, B. (2026). Personality beyond the brain: a new perspective on the brain-gut-gonadal axis and human fertility. Frontiers in Behavioral Neuroscience, 20, Article 1985122. https://doi.org/10.3389/fnbeh.2026.1985122

Image Credits: AI Generated

DOI: 10.3389/fnbeh.2026.1985122

Keywords: personality traits, brain-gut axis, HPG axis, HPA axis, unexplained infertility, gut microbiota, autonomic nervous system, neuroendocrine regulation, sexual function, reproductive health, irritable bowel syndrome, cortisol

IPANs function as the gut’s local sentinels. Morphologically, they correspond to what anatomists call Dogiel type II neurons, cells with smooth, multipolar bodies and long processes that wrap circumferentially around the intestinal wall. Electrophysiologically, they are characterized as AH-type neurons, distinguished by a prominent slow afterhyperpolarization, a prolonged electrical reset that limits repetitive firing and gives these cells their distinctive excitability profile. Unlike extrinsic sensory neurons housed in the dorsal root and nodose ganglia, which relay gut information to the central nervous system, IPANs detect mechanical deformation, chemical cues, nutrients, microbial metabolites, and immune-derived signals, then pass this information to interneurons, motor neurons, and secretomotor pathways entirely within the enteric network. This architecture allows the intestine to mount rapid, localized reflexes, peristalsis, secretion, and vasodilation, without waiting for central approval.

The review emphasizes that IPAN excitability is remarkably plastic. Inflammation, serotonergic signaling, cytokines, neurotrophins, and microbial products can all alter firing thresholds, modify the slow afterhyperpolarization, and reshape synaptic transmission. In experimental models, repetitive stimulation or exposure to inflammatory mediators produces lasting sensitization of these neurons, a form of neural memory that may persist long after the initial insult has resolved. The authors propose that such maladaptive plasticity could shift IPANs from adaptive sensory encoders into persistently hyperexcitable states, lowering reflex thresholds and amplifying enteric responses in ways that promote urgency, diarrhea, and visceral hypersensitivity. Conversely, suppressed sensory gain could impair the initiation of peristaltic and secretory reflexes, contributing to stasis, constipation, and defective mucosal clearance.

One of the most striking recent advances comes from molecular profiling. Single-cell and single-nucleus transcriptomic analyses have identified neuromedin U, or NMU, as a conserved marker of putative myenteric IPANs in both mice and humans, though its expression is strongly region dependent, marking roughly 50 to 75 percent of putative IPANs in the human small intestine but only 5 to 10 percent in the colon. In the mouse colon, researchers identified cadherins Cdh6 and Cdh8 as selective markers of Dogiel type II/AH sensory neurons, enabling cell-type-specific manipulation for the first time. Optogenetic activation of Cdh6-positive IPANs was shown to evoke retrograde colonic motor complexes, while pharmacological blockade of their hyperpolarization-activated current disrupted spontaneous generation of these motor patterns. This established that a molecularly defined IPAN population is both sufficient and necessary for a specific motor program under physiological conditions, a milestone in enteric neurobiology.

Perhaps the most conceptually transformative finding involves neuroimmunity. IPANs express a broad repertoire of cytokine, chemokine, and pattern-recognition receptors, including receptors for the type 2 cytokines IL-4 and IL-13, Toll-like receptors, and receptors for TNF, IL-1β, IL-6, and IL-17. Work by Wang and colleagues, using genetic and viral approaches combined with single-nucleus RNA sequencing, identified a population of IL-13 receptor-expressing IPANs as a functional node in gut neuroimmune signaling during helminth infection. In this circuit, group 2 innate lymphoid cells release IL-13, which activates IPANs through the IL-13 receptor, inducing the release of beta-calcitonin gene-related peptide. That neuropeptide then suppresses ILC2 activity, establishing a reciprocal feedback loop. When the researchers deleted the neuronal IL-13 receptor alpha 1 subunit, host defense against the parasite Heligmosomoides polygyrus was impaired, and combined administration of NMU and beta-CGRP restored parasite clearance, supporting a causal role for this neuronal pathway in protective immunity.

The microbiome adds another layer of complexity. Studies in germ-free rodents revealed that jejunal myenteric AH/Dogiel type II neurons exhibit impaired excitability, with elevated firing thresholds, reduced input resistance, and prolonged calcium-dependent slow afterhyperpolarization. Remarkably, conventionalizing adult germ-free animals with a normal microbiota normalized these electrophysiological properties. Subsequent work showed that pharmacological excitation of IPANs increased mesenteric nerve discharge by 21 percent in specific pathogen-free mice and 41 percent in conventionalized mice, but by only 2 percent in germ-free animals, suggesting that microbial input is required for normal signal transmission from IPANs to extrinsic afferent pathways. Pattern-recognition receptors such as TLR2 and TLR4 on enteric neurons and glia mediate some of these effects, and commensal-derived N-formyl peptides can directly activate IPANs through FPR1-dependent reactive oxygen species generation.

Serotonergic signaling provides some of the strongest pharmacological evidence for IPAN involvement in gut function, though the picture is far from simple. Enterochromaffin cell-derived serotonin activates 5-HT1P receptors on primary afferent neurons to initiate secretory reflexes, while 5-HT3 receptors on interneurons and secretomotor neurons participate in peristaltic signaling. Clinically, 5-HT4 receptor agonists such as prucalopride accelerate gastrointestinal transit, whereas 5-HT3 antagonists like alosetron delay transit and increase colonic compliance. Yet the review notes that mucosal removal can abolish cyclical serotonin release without preventing peristalsis, and Tph1 deletion does not necessarily impair transit, challenging a strictly mucosal serotonin-dependent reflex model and pointing instead to direct enteric mechanotransduction as a critical mechanism.

Despite this wealth of convergent evidence, the authors are candid about the field’s central limitation: no study has yet completed the canonical experimental sequence of selectively disrupting IPANs, inducing a gastrointestinal phenotype, and then reversing it through targeted rescue, particularly in human tissue. Pharmacological approaches often lack anatomical specificity because their targets are expressed by multiple cell types. Transcriptomic atlases predominantly define neuronal identity under healthy conditions rather than in disease. Germ-free models establish that microbial input is required for normal IPAN function but do not prove that dysbiosis directly corrupts afferent coding. Whether maladaptive IPAN sensory coding is a primary driver of disease, an amplifier of existing pathology, or merely a consequence of broader enteric dysfunction remains unresolved.

The therapeutic implications, however, are tantalizing. The antibiotic rifaximin, which modulates the gut microbiota, has been shown to reduce visceral hypersensitivity in both patients with diarrhea-predominant IBS and murine models, implicating microbial regulation of afferent signaling in human disease. If future studies can establish IPAN-specific causal links using conditional genetics, gnotobiotic reconstitution with defined microbial consortia, and validation in human enteric preparations, the review suggests that therapeutic recalibration of sensory gain and neuroimmune signaling could offer a rational strategy for restoring gut homeostasis in chronic inflammatory and functional gastrointestinal disorders. Such an approach would represent a fundamental shift from treating symptoms to correcting the underlying neural code that governs how the gut perceives and responds to its internal world.

For the millions of people worldwide living with IBS, IBD, chronic constipation, and unexplained visceral pain, the message from this synthesis is one of cautious optimism. The enteric nervous system is not merely a passive conduit for central commands but an autonomous integrative hub whose sensory neurons sit at the intersection of mechanical, chemical, microbial, and immunological signaling. Understanding how IPANs encode these signals in health, and how that encoding goes wrong in disease, may finally provide the mechanistic foundation needed to develop targeted therapies that restore, rather than merely suppress, the gut’s intrinsic intelligence.

Subject of Research: The role of maladaptive sensory coding by enteric nervous system neurons in gastrointestinal disorders

Article Title: Maladaptive sensory coding in the enteric nervous system playing a role in gastrointestinal disorders

Article References: Yu, L. C.-H., Huang, C.-Y., Lin, C.-Y., Tsai, Y.-S., Chang, Y.-C., Huang, C.-W., Chao, Z.-L., & Kuo, W.-T. (2026). Maladaptive sensory coding in the enteric nervous system playing a role in gastrointestinal disorders. Frontiers in Cellular Neuroscience, 20, Article 1903390. https://doi.org/10.3389/fncel.2026.1903390

Image Credits: AI Generated

DOI: 10.3389/fncel.2026.1903390

Keywords: enteric nervous system, intrinsic primary afferent neurons, irritable bowel syndrome, inflammatory bowel disease, visceral hypersensitivity, neuroimmune communication, gut microbiota, serotonin, IPANs, gastrointestinal motility, neural plasticity, Dogiel type II neurons

The study, published in Frontiers in Gastroenterology, was designed to answer a question that has lingered in gastroenterology for decades: does having IBS-like symptoms on top of IBD actually change the course of the disease, or does it simply make patients feel miserable while their IBD smolders quietly? Previous estimates suggested that roughly a third of IBD patients in remission experience IBS-type symptoms, a rate far above the roughly six percent prevalence of IBS in the general population. Yet those estimates varied wildly depending on how remission was defined, and earlier longitudinal studies relied on fecal calprotectin thresholds that many experts consider too permissive to exclude ongoing intestinal inflammation.

To tighten the methodology, the Boston team recruited adults with established IBD at the time of a scheduled colonoscopy between 2020 and 2022. Quiescence was defined endoscopically, using a Mayo score of zero or one for ulcerative colitis and the absence of ulcerations for Crohn’s disease, and the great majority of participants, 84.2 percent, were also in histological remission. At the same visit, patients completed the IBS Symptom Severity Scale, a validated questionnaire that allowed the investigators to sort them into three groups: no IBS-like symptoms in 53 patients, mild symptoms in 43, and moderate to severe symptoms in 18. The researchers then manually extracted clinical data from the electronic medical record through September 2025, yielding a median follow-up of 3.5 years that was comparable across all three groups.

The primary outcome was total IBD-related healthcare utilization, a deliberately broad measure that captured clinic visits, endoscopic and imaging evaluations, emergency department visits, hospitalizations, surgeries, and even complications of IBD medications. The results showed a clear gradient. Patients with no IBS-like symptoms accumulated a median of 8 utilization events, those with mild symptoms 12, and those with moderate-severe symptoms 7, a difference that reached statistical significance. Expressed differently, patients with mild symptoms logged 391 events over 132.3 patient-years and those with moderate-severe symptoms 223 events over 62.9 patient-years, compared with 447 events over 183.7 patient-years among symptom-free patients. A negative binomial regression adjusting for IBD type and biologic therapy confirmed higher adjusted incidence rate ratios of 1.214 for mild and 1.393 for moderate-severe symptoms.

Perhaps the most clinically provocative finding emerged from the time-to-event analysis of unscheduled or acute care, defined as imaging, emergency department visits, hospitalizations, and surgeries, excluding routine monitoring visits and endoscopies. After multivariable adjustment, mild IBS-like symptoms carried a hazard ratio of 3.6 for unscheduled acute utilization, and moderate-severe symptoms a hazard ratio of 6.2, relative to patients without such symptoms. The Kaplan-Meier curves revealed that most of this excess risk accumulated within the first year after the index colonoscopy before plateauing. The authors caution that the absolute number of acute events was small, making these hazard ratios exploratory, but the direction and magnitude of the effect are difficult to ignore.

Dissecting where the extra utilization came from proved illuminating. The excess was driven mainly by imaging studies such as CT and MRI enterography, which accounted for 6 to 8 percent of events in the symptomatic groups versus only 1 percent in the asymptomatic group. By contrast, endoscopies were proportionally more common among patients without IBS-like symptoms, consistent with proactive surveillance rather than symptom-driven investigation. Hospitalizations and emergency department visits were rare across the board. This pattern suggests that when patients with quiescent IBD but troublesome symptoms present to their physicians, clinicians often reach for cross-sectional imaging to hunt for inflammation that endoscopy has already largely excluded, an expensive and radiation-bearing reflex that may frequently be unnecessary.

Equally important was what the study did not find. Among the 59 patients on biologic therapy at baseline, treatment failure, defined as drug discontinuation due to primary non-response, loss of response, or serious adverse events, did not differ significantly by IBS-like symptom status. Nine percent of patients without symptoms discontinued their biologic, compared with 27 percent of those with moderate-severe symptoms, a numerical gap that failed to reach statistical significance. This aligns with two prior studies from a United Kingdom cohort led by Gracie and Fairbrass, which similarly found that IBS-type symptoms predicted greater healthcare use and worse quality of life but not longitudinal disease activity, steroid need, therapy escalation, hospitalization, or intestinal resection.

The psychological dimension of the findings deserves attention. Using the PROMIS measurement system, where 50 represents the population average, the study recorded progressively higher anxiety and depression scores across the symptom groups. Patients with no IBS-like symptoms averaged 47.2 on the anxiety scale, while those with moderate-severe symptoms averaged 58.9, and depression scores followed the same pattern. The authors acknowledge that this psychological burden, together with the possibility of surveillance bias, may partly explain the elevated healthcare-seeking behavior. The underlying mechanisms linking IBS-like symptoms to IBD remain elusive, with candidate explanations including post-inflammatory visceral hypersensitivity, microbiome alterations, dysregulated gut-brain interactions, increased intestinal permeability, and low-grade immune activation.

The study is not without limitations, which the authors lay out candidly. Defining IBS within an IBD population remains inherently difficult, and alternative diagnoses such as bile acid diarrhea, small intestinal bacterial overgrowth, or pelvic floor dysfunction could account for some symptoms. Residual microscopic inflammation or proximal small bowel disease could not be fully excluded, fecal calprotectin and C-reactive protein data were available for only a small subset, and the symptom questionnaire was administered only once at baseline even though IBS-type symptoms fluctuate over time. The modest sample size precluded subgroup analyses, the tertiary care population may not represent typical IBD patients, and the COVID-19 pandemic overlapped with early follow-up. Still, the concurrent use of endoscopy and symptom scoring represents a meaningful methodological advance over prior work.

The takeaway for patients and clinicians is both sobering and actionable. IBS-like symptoms in endoscopically quiescent IBD are clinically meaningful, driving substantial healthcare consumption without reflecting inflammatory disease activity, and the authors argue they warrant targeted recognition and treatment within IBD care models. In practical terms, that could mean pairing routine IBD management with therapies proven for functional bowel disorders, including gut-brain neuromodulators, dietary interventions, and psychological treatments, rather than escalating immunosuppressive drugs in response to symptoms that inflammation scores say should not exist. As biologic therapies push more IBD patients into deep remission, distinguishing the inflamed gut from the irritable one may become one of the specialty’s central challenges, and this study offers a rigorous template for doing exactly that.

Subject of Research: The association of irritable bowel syndrome-like symptoms with healthcare utilization and treatment outcomes in patients with quiescent inflammatory bowel disease

Article Title: Irritable bowel syndrome-like symptoms are associated with increased healthcare utilization in patients with inflammatory bowel disease

Article References: Montgomery, S., Saraga, A., Rothschild, N. D. V., Soliman, M. A., Kim, A. N., Midura, I., Tikkala, R., Zhang, L., Rakowsky, S., Rabinowitz, L., Papamichael, K., Cheifetz, A. S., & Ballou, S. (2026). Irritable bowel syndrome-like symptoms are associated with increased healthcare utilization in patients with inflammatory bowel disease. Frontiers in Gastroenterology, 5, Article 1924176. https://doi.org/10.3389/fgstr.2026.1924176

Image Credits: AI Generated

DOI: 10.3389/fgstr.2026.1924176

Keywords: inflammatory bowel disease, irritable bowel syndrome, Crohn's disease, ulcerative colitis, healthcare utilization, endoscopic remission, biologic therapy, treatment failure, gut-brain axis, IBS-SSS, gastroenterology, visceral hypersensitivity

The study, led by Yutong Cheng and Qiuai Shu of The Second Affiliated Hospital of Xi’an Jiaotong University and published in Experimental Biology and Medicine, addresses a persistent problem in microbiome research. Observational studies have repeatedly reported microbial alterations in patients with functional gastrointestinal disorders, but the findings have been frustratingly inconsistent. Some studies found lower abundances of certain bacteria in patients compared with healthy controls, while others reported the opposite pattern or no difference at all. Without a way to establish the direction of these associations, it remained unclear whether the reported microbial changes were causes, consequences, or simply correlates of the disorders.

Mendelian randomization offers a way around this impasse by exploiting the random allocation of genetic variants at conception. Because single nucleotide polymorphisms are inherited independently of environmental factors and remain stable throughout life, they can serve as natural instruments for testing whether an observational association between an exposure and an outcome is consistent with a causal effect. The researchers drew their genetic data from genome-wide association studies of gut microbiota involving 14,306 individuals and from the FinnGen biobank, which provided summary statistics for irritable bowel syndrome based on 187,028 individuals and for functional dyspepsia based on 194,071 individuals, all of European ancestry.

The team selected 196 bacterial traits classified from phylum to genus level and applied rigorous quality control criteria to identify suitable instrumental variables. They used a relaxed significance threshold of P less than 5.0 times 10 to the negative 6 to obtain enough variants, performed linkage disequilibrium clumping with a threshold of r squared less than 0.001 and a window size of 10,000 kilobases, and calculated F statistics to ensure that all instruments exceeded the conventional threshold of 10, minimizing weak instrument bias. The inverse-variance-weighted method served as the primary analysis, with weighted median estimation as an auxiliary approach and a battery of sensitivity analyses to assess robustness.

The results revealed a striking asymmetry between the two disorders. For irritable bowel syndrome, higher genetically predicted abundances of the order Bifidobacteriales were associated with a lower risk of the condition, with an odds ratio of 0.741 and a 95 percent confidence interval of 0.570 to 0.963. The genus Eubacterium ventriosum group showed a similar protective pattern, with an odds ratio of 0.684 and a confidence interval of 0.524 to 0.893. Both associations were supported by both the inverse-variance-weighted and weighted median estimators, strengthening the case for their reliability.

For functional dyspepsia, the picture was more complex. A higher genetically predicted abundance of the genus Lachnospiraceae NK4A136 group was associated with an increased risk of the disorder, with an odds ratio of 1.368 and a confidence interval of 1.086 to 1.722. In contrast, the family Desulfovibrionaceae and the order Desulfovibrionales were protective, with an odds ratio of 0.649 and a confidence interval of 0.471 to 0.893. The researchers noted that the Desulfovibrionaceae and Desulfovibrionales analyses used the same seven instrumental variants and yielded nearly identical estimates, suggesting these represent highly overlapping rather than independent signals.

Sensitivity analyses provided strong support for the validity of these findings. Cochran’s Q test showed little evidence of heterogeneity among the variant-specific causal estimates. The MR-Egger intercept tests, which detect directional horizontal pleiotropy, returned P values ranging from 0.698 to 1.000 across the five significant associations, providing no evidence that the results were driven by pleiotropic pathways. MR-PRESSO global tests detected no overall pleiotropy and identified no outlier variants. Leave-one-out analyses confirmed that no single genetic variant disproportionately influenced any of the associations.

The reverse direction of the analysis yielded equally intriguing results. When the researchers asked whether genetically predicted disease risk influenced microbial abundance, they found that irritable bowel syndrome risk was associated with lower abundances of the genera Turicibacter and Slackia. The Turicibacter association was supported by both estimators, with a beta of negative 0.167 and a confidence interval of negative 0.283 to negative 0.052 in the primary analysis. No robust reverse associations were observed for functional dyspepsia. This bidirectional pattern suggests that the relationship between gut microbes and irritable bowel syndrome may be a two-way street, with the disorder itself capable of reshaping the microbial community.

The biological plausibility of these findings is supported by existing experimental evidence. Certain Bifidobacterium species can generate gamma-aminobutyric acid, an inhibitory neurotransmitter that may influence visceral sensitivity through the microbiota-gut-brain axis. A randomized controlled trial previously reported that a specific Bifidobacterium strain improved abdominal pain in women with irritable bowel syndrome. The Eubacterium ventriosum group includes butyrate-producing bacteria that support epithelial barrier integrity and mucosal immune regulation. Experimental studies have shown that Turicibacter interacts bidirectionally with host serotonergic signaling, providing a possible mechanistic link to the gut-brain communication pathway.

The authors are careful to frame these findings as hypothesis-generating rather than definitive. They emphasize that the identified microbial taxa are candidates for further mechanistic and clinical validation rather than established risk factors or therapeutic targets. The study has limitations, including the restriction to European ancestry populations, the limited number of instrumental variants for some microbial traits, and the reliance on 16S rRNA gene sequencing, which constrains analysis to the genus level and above. The fecal samples used in the microbiome studies may not represent the microbial composition at the gastroduodenal site most relevant to functional dyspepsia. Future studies should replicate these associations in independent and ancestrally diverse cohorts, employ strain-resolved shotgun metagenomics, and evaluate candidate strains and metabolites in mechanistic models before advancing to adequately powered intervention trials. Such stepwise validation could ultimately inform the development of more targeted and individualized microbiota-based strategies for these common and debilitating disorders.

Subject of Research: Genetics

Article Title: Causal effects of gut microbiota on functional gastrointestinal disorders: a bidirectional Mendelian randomization study

Article References: Cheng, Y., Shu, Q., Wang, Z., Wu, J., Peng, Y., Xie, J., Liang, X., Tao, Z., Shi, H., Wei, Z., Wang, J., & Xie, N. (2026). Causal effects of gut microbiota on functional gastrointestinal disorders: a bidirectional Mendelian randomization study. Experimental Biology and Medicine, 251, Article 11023. https://doi.org/10.3389/ebm.2026.11023

Image Credits: AI Generated

DOI: 10.3389/ebm.2026.11023

Keywords: gut microbiota, Mendelian randomization, irritable bowel syndrome, functional dyspepsia, functional gastrointestinal disorders, GWAS, Bifidobacteriales, Eubacterium ventriosum group, Lachnospiraceae NK4A136 group, Desulfovibrionaceae, gut-brain axis, causality

The research team, led by investigators at Northwestern University Feinberg School of Medicine including dermatologist Peter Lio, drew on data from the National Institutes of Health’s All of Us Research Program, a massive biomedical database that links participant surveys to electronic health records. Because the program collects detailed demographic information alongside longitudinal clinical data, it allowed the researchers to do something previous studies of the rosacea-gut connection rarely could: measure, patient by patient, the interval between the two diagnoses and test whether that interval differed systematically across population groups.

The statistical machinery behind the study was chosen with care. When the team examined the distribution of time differences between diagnoses, formal tests for normality and equal variance, specifically Shapiro-Wilk and Levene’s tests, indicated that the data violated the assumptions required for parametric statistics. The researchers therefore turned to non-parametric methods: Wilcoxon signed-rank tests to assess whether, within each demographic stratum, the median time difference between the IBS and rosacea diagnosis dates shifted significantly away from zero, and Kruskal-Wallis tests to compare those shifts between groups defined by race and ethnicity, education, income, gender, and age.

The headline result is a consistent directional skew. The median time difference, calculated as the IBS diagnosis date minus the rosacea diagnosis date, was negative in every demographic group the team examined, ranging from about 0.09 years to 2.03 years before the rosacea diagnosis. In plain terms, across every stratum of the population studied, the typical patient had their bowel syndrome documented before their facial flushing earned a name. Wilcoxon signed-rank tests confirmed that these within-group median shifts were statistically significant in several strata, particularly those with the largest sample sizes, where the tests have the most power to detect real asymmetry.

Yet the study’s second major finding is just as important as the first: demographics do not explain the pattern. When the researchers built a logistic regression model to predict which condition came first using race and ethnicity, education, income, gender, and age, the model achieved only 52.6 percent accuracy, barely better than a coin flip, with an area under the curve of 0.52. Kruskal-Wallis comparisons between demographic groups were uniformly non-significant, with p-values of 0.98 for race and ethnicity, 0.83 for education, 0.40 for income, 0.52 for gender, and 0.14 for age. Whatever drives the gut-before-skin sequence, it does not appear to respect the usual social and demographic fault lines.

To understand why this temporal ordering matters, it helps to zoom in on the biology that has energized the gut-skin axis field in recent years. The gut and the skin are both barrier organs, both heavily populated by immune cells, and both colonized by microbial communities that communicate with the host immune system. Reviews of the gut-skin axis have described how intestinal dysbiosis, an imbalance in gut microbial composition, can increase intestinal permeability, promote systemic inflammation, and modulate immune signaling in ways that plausibly reach the skin. In rosacea specifically, studies have documented activation of Th1 and Th17 inflammatory pathways in lesional skin, and systematic reviews have linked the condition to alterations in both cutaneous and gastrointestinal microbiomes.

The connection between rosacea and the gut is not new to dermatologists. Population-based cohort research from Denmark published in 2017 found that people with rosacea had elevated rates of several gastrointestinal disorders, including celiac disease, Crohn’s disease, ulcerative colitis, and irritable bowel syndrome. More recently, a study using the Korean National Health Insurance Service cohort examined whether rosacea might raise the risk of subsequently developing IBS, and bi-directional Mendelian randomization analyses have probed whether inflammatory bowel disease and rosacea share causal links through genetic instruments. Small intestinal bacterial overgrowth has also been reported at elevated rates in rosacea patients, and some trials have explored whether targeting the gut microbiome can calm the skin. What most of this earlier work lacked, however, was a direct measurement of onset order within the same individuals.

That is precisely the gap the new study fills, and the direction of the skew, IBS first in a majority of cases, is at least compatible with a model in which chronic gut inflammation or microbial disturbance contributes to the later emergence of cutaneous disease. Chronic gut inflammation and dysbiosis in IBS have been implicated in other inflammatory skin conditions, including atopic dermatitis, and neurohormonal-immune dysregulation along the skin-gut-brain axis has been proposed as a shared pathway in rosacea. If gut-driven systemic inflammation primes the skin’s vasculature and immune defenses, one might expect bowel symptoms to precede facial ones, on average, which is what the data show at the population level.

But the authors are careful, and rightly so, to keep the interpretation within strict limits. The dataset records the date a diagnosis was documented, not the date symptoms actually began. A patient may have endured years of abdominal pain before a clinician finally wrote down an IBS code, or may have had visible facial redness long before anyone called it rosacea. Diagnostic lag, healthcare access, and coding practices could all distort the apparent sequence. The study is also cross-sectional in design, meaning it captures a snapshot of the timing relationship rather than following patients forward in time, and it cannot establish that IBS causes rosacea or that any shared mechanism exists at all. The researchers themselves emphasize that the findings are descriptive and that prospective studies incorporating clinical and lifestyle variables are needed before any gut microbiome-mediated link can be properly evaluated.

Even with those caveats, the study offers a genuinely useful piece of the puzzle. It demonstrates, in a large and demographically diverse cohort, that the association between IBS and rosacea is not a random collision of two common conditions but a temporally structured one, with a reproducible direction that holds across race, ethnicity, education, income, gender, and age. It also delivers a humbling lesson about prediction: population-level patterns can be real and robust while remaining nearly useless for forecasting what will happen in any individual patient. For clinicians, the practical takeaway is one of heightened awareness, since a patient presenting with one of these conditions may warrant attention to the other. For researchers, the study provides a temporal scaffold on which mechanistic hypotheses about microbial signaling, immune trafficking, and neurovascular inflammation can now be tested with prospective designs. The gut-skin axis has been celebrated in headlines for years; studies like this one, modest in size but precise in method, are how the field moves from slogan to science.

Subject of Research: The temporal onset relationship between irritable bowel syndrome and rosacea within the gut-skin axis

Article Title: Temporal relationship between irritable bowel syndrome (IBS) and rosacea: an analysis of onset timing

Article References: Marzouk, S., Saleeb, J., Muttar, S., Alkhalili, S., Alsheikh, A., Nasari, A., Hassan, T., Issa, R., Hassan, O., & Lio, P. (2026). Temporal relationship between irritable bowel syndrome (IBS) and rosacea: an analysis of onset timing. Archives of Dermatological Research, 318(1), Article 524. https://doi.org/10.1007/s00403-026-05003-w

Image Credits: AI Generated

DOI: 10.1007/s00403-026-05003-w

Keywords: irritable bowel syndrome, rosacea, gut-skin axis, gut microbiome, onset timing, All of Us Research Program, dermatology, gastroenterology, chronic inflammation, dysbiosis, cross-sectional study, electronic health records

Ulcerative colitis is a chronic inflammatory bowel disease that causes long-standing inflammation and ulceration of the inner lining of the large intestine and rectum. Patients typically experience abdominal cramping, bloating, diarrhea and irregular bowel movements, symptoms that can significantly impair quality of life. Modern therapies, including corticosteroids, immunomodulators and biologic agents, have become remarkably effective at suppressing the underlying inflammation, and many patients achieve what clinicians call remission. Yet a substantial fraction of these patients do not feel well even when their colonoscopies and biopsies suggest their disease is quiet.

The central question of the new study is deceptively simple: are these lingering symptoms a sign of disease activity that standard testing misses, or are they driven by an entirely different mechanism? The answer matters enormously for patients. If persistent symptoms reflect ongoing, subclinical inflammation, treatment should be intensified. If instead they arise from altered gut-brain signaling, escalating immunosuppressive therapy may expose patients to risks without any benefit, and approaches that target the nervous system may be more appropriate.

The scale of the problem is considerable. According to the source announcement, in roughly one in three patients with ulcerative colitis, symptoms resembling those of irritable bowel syndrome persist even when inflammation is minimal or absent. Irritable bowel syndrome is a functional gastrointestinal disorder, distinct from inflammatory bowel disease, in which symptoms occur without the tissue damage and inflammation characteristic of colitis. The overlap between the two conditions has long complicated clinical decision-making, because the same complaint, diarrhea or abdominal pain, can signal very different underlying processes depending on the patient.

Chang, who is vice chief of the Vatche and Tamar Manoukian Division of Digestive Diseases at UCLA, brings to the project an unusually broad portfolio of leadership roles that reflect the interdisciplinary nature of the research. She directs the Walter and Shirley Wang Center for Integrative Digestive Health, co-directs the G. Oppenheimer Center for Neurobiology of Stress and Resilience, directs the Clinical Studies and Database Core of the Goodman-Luskin Microbiome Center and serves as program director of the UCLA Gastroenterology Fellowship Program. Her co-investigator, Sands, leads the gastroenterology division at Mount Sinai, one of the country’s major centers for inflammatory bowel disease care and research.

Methodologically, the study is designed to interrogate both sides of the gut-brain axis, the bidirectional communication network linking the enteric nervous system of the digestive tract with the central nervous system. The researchers will deploy brain imaging to examine how the brains of patients with quiescent colitis and persistent symptoms differ in their processing of visceral signals, an approach that has previously revealed altered pain and arousal networks in functional gastrointestinal disorders. In parallel, participants will wear wearable technology capable of measuring autonomic nervous system function, providing continuous, real-world data on heart rate variability and other physiological markers that reflect the balance between sympathetic and parasympathetic activity.

The autonomic nervous system is a plausible culprit in this context. It regulates gut motility, secretion and sensitivity, and disruptions in its signaling have been implicated in both inflammatory bowel disease and irritable bowel syndrome. Chronic inflammation can remodel autonomic pathways, and conversely, altered autonomic tone can influence immune activity in the gut. By capturing these measurements longitudinally in patients whose inflammation has subsided, the team hopes to determine whether persistent symptoms correlate with measurable autonomic dysfunction, with residual inflammatory activity, or with some interaction between the two.

Perhaps the most clinically ambitious component of the study is its test of a potential intervention. The researchers will evaluate whether non-invasive vagal nerve stimulation can improve symptoms in affected patients. Vagal nerve stimulation, which delivers electrical impulses to the vagus nerve, the main conduit of parasympathetic signaling between the brain and the body, has been used for years in neurology and is increasingly explored for disorders involving gut-brain dysregulation. Because the vagus nerve modulates both immune responses and visceral sensory processing, stimulating it could in principle address the mechanisms the study is designed to uncover, offering a therapy that works through the nervous system rather than the immune system.

The ultimate goal, according to the announcement, is to support new personalized treatment approaches for ulcerative colitis patients who have little to no active inflammation yet continue to experience persistent IBS-like symptoms. Personalization is the key word. If the study succeeds in distinguishing symptom drivers at the level of individual patients, clinicians could one day match therapies to mechanisms, reserving anti-inflammatory escalation for those with hidden inflammation and offering neuromodulation or related approaches to those whose symptoms stem from altered gut-brain signaling. That would represent a meaningful shift in how gastroenterologists manage the growing population of patients in inflammatory bowel disease remission who still do not feel well.

The grant also reflects a broader trend in digestive disease research, in which the traditional boundary between organic and functional disorders is dissolving. Conditions once dismissed as purely psychological are now understood to involve measurable alterations in neural signaling, immune activity and the microbial environment of the gut. By combining neuroimaging, wearable physiology and a neuromodulation trial within a single five-year program, the UCLA and Mount Sinai team is positioned to generate exactly the kind of mechanistic evidence that could move persistent post-inflammatory symptoms from the margins of gastroenterology into the mainstream of precision medicine. For the roughly one in three patients whose colitis has quieted but whose symptoms have not, the study offers the prospect that their suffering will finally be explained, and treated, on its own terms.

Subject of Research: Persistent IBS-like symptoms in ulcerative colitis patients with resolved inflammation and gut-brain signaling mechanisms

Article Title: UCLA Health awarded $4 million NIH grant to study why ulcerative colitis symptoms persist after inflammation subsides

Article References: UCLA Health awarded $4 million NIH grant to study why ulcerative colitis symptoms persist after inflammation subsides. (n.d.). Original publication

Image Credits: AI Generated

DOI: Not provided

Keywords: ulcerative colitis, irritable bowel syndrome, gut-brain axis, NIH grant, UCLA Health, Mount Sinai, vagal nerve stimulation, autonomic nervous system, brain imaging, inflammatory bowel disease, gastroenterology, Lin Chang

The findings arrive at a moment when irritable bowel syndrome has become one of the most common and frustrating diagnoses in gastroenterology. Classified among disorders of gut-brain interaction, IBS produces abdominal pain, bloating, and disturbed bowel habits in the absence of visible structural damage, and it resists most pharmacological treatments. That therapeutic vacuum has made acupuncture an increasingly popular option, and clinical trials have repeatedly reported that patients improve after a course of needling. But those trials also routinely show that patients receiving sham acupuncture improve nearly as much, raising a question that has shadowed complementary medicine research for decades: how much of the benefit is the needle, and how much is the mind?

To answer it, the researchers searched eight databases — PubMed, Embase, the Cochrane Library, Web of Science Core Collection, and four major Chinese databases including CNKI, Wanfang, VIP, and CBM — from their inception through July 4, 2026. They included only randomized controlled trials in which sham acupuncture served as a comparator in IBS patients, and they registered the protocol prospectively with PROSPERO under the identifier CRD420251035956. The primary outcome was the response rate, the proportion of patients who reported meaningful improvement, while secondary outcomes tracked changes in the IBS Symptom Severity Scale, the IBS Quality of Life scale, and abdominal pain intensity scores. Effect sizes were expressed as risk differences and pooled pre-to-post changes with 95 percent confidence intervals.

The headline numbers are striking. In patients who received sham acupuncture, the combined response rate was 0.38, meaning roughly 38 of every 100 patients treated with a placebo procedure reported feeling meaningfully better. On the IBS Symptom Severity Scale, scores fell by a pooled 60.08 points, with a confidence interval running from 70.62 down to 49.54 points of improvement. Quality of life scores rose by 8.23 points on average, and abdominal pain intensity dropped by 1.39 points on standard rating scales. None of these changes came from needles that penetrated classical acupoints in the way traditional theory prescribes; they emerged entirely from procedures intended to mimic acupuncture without its specific effects.

What does a 60-point drop on the symptom severity scale actually mean in clinical terms? The IBS-SSS is a 500-point instrument that captures pain intensity, pain frequency, bloating, satisfaction with bowel habits, and overall interference with daily life, and clinicians generally regard shifts of 50 points or more as clinically meaningful. By that yardstick, the placebo response documented in this analysis is not a statistical curiosity but a genuine therapeutic effect — one large enough that patients experience it as relief. Similarly, the 1.39-point reduction in pain intensity, measured on visual analog or numerical rating scales, represents a noticeable easing of the cramping and discomfort that define the condition.

Perhaps the most consequential part of the study, however, is not the headline effect size but the heterogeneity hiding beneath it. When the researchers stratified trials by their methodological and diagnostic characteristics, clear patterns emerged. Studies that used the Rome IV diagnostic criteria — the current international standard for defining functional gastrointestinal disorders — tended to report lower placebo responses than those relying on older Rome III or earlier criteria. Trials judged to be at low risk of bias also yielded smaller placebo effects, as did studies that defined treatment response according to the stringent criteria recommended by the U.S. Food and Drug Administration for IBS clinical trials. In other words, the more rigorous and modern the trial, the smaller the apparent power of the sham needle.

That pattern carries a lesson that extends well beyond acupuncture. Placebo responses are not fixed properties of a treatment; they are shaped by how trials are designed, how patients are selected, how outcomes are defined, and how much room subjective judgment has to wander. Older diagnostic criteria that swept in more heterogeneous patient populations, and looser definitions of what counts as a response, both inflate the apparent benefit of an inert procedure. The FDA’s patient-reported outcome requirements, which demand sustained improvement in abdominal pain and stool pattern rather than a fleeting global impression, are specifically engineered to filter out noise — and the analysis suggests they do exactly that, compressing the placebo response toward more conservative estimates.

The mechanisms behind a placebo response of this magnitude are likely multiple and overlapping. Ritualized, hands-on treatment delivers a dense bundle of contextual cues: a practitioner’s attention, the sensory experience of needling, the expectation of relief, and repeated clinical contact over weeks. IBS is, by definition, a disorder of gut-brain interaction, in which visceral sensitivity, stress physiology, and central pain processing are tightly entangled — making it precisely the kind of condition in which expectation and conditioning can plausibly modulate symptoms through real neurophysiological pathways. The gut’s enteric nervous system, its bidirectional communication with the brain via the vagus nerve and hypothalamic-pituitary-adrenal axis, and the endogenous opioid and cannabinoid systems all provide biological conduits through which psychological context can translate into altered gut sensation and motility.

For acupuncture researchers, the implications cut in two directions. On one hand, the substantial placebo response documented here means that any future trial of real acupuncture in IBS must be powered and designed to detect benefits that exceed this baseline — a demanding threshold, given that the sham arm already delivers clinically meaningful improvement to more than a third of patients. On the other hand, the finding does not automatically invalidate acupuncture as a therapy; it reframes the question. If part of acupuncture’s effect in IBS is a potent, ritual-mediated placebo response, some researchers argue that harnessing that response deliberately and ethically could itself be a legitimate clinical strategy, particularly for a condition with few effective drugs. The authors of the analysis note that several factors — diagnostic criteria, risk of bias, and response definitions — can notably influence the size of the placebo component, and that understanding these moderators is essential for interpreting both past and future trials.

For patients and clinicians, the study is a reminder that improvement after treatment is real even when the mechanism is expectation rather than needle stimulation — and that honest science can quantify that effect without dismissing the suffering it relieves. The 977 patients in these twelve trials who felt better after sham acupuncture were not imagining their symptoms fading; their brains and guts were genuinely recalibrating in response to context, ritual, and care. Disentangling how much of acupuncture’s benefit in IBS comes from specific needling effects and how much from this powerful contextual machinery will require trials that meet the highest methodological standards — Rome IV criteria, low risk of bias, and FDA-grade outcome definitions — and the new analysis provides the benchmark against which those trials can now be judged. In the meantime, it stands as one of the clearest quantitative demonstrations that in the contested territory of mind-body medicine, the placebo needle is anything but inert.

Subject of Research: Placebo response to sham acupuncture in patients with irritable bowel syndrome

Article Title: Placebo response of sham acupuncture in patients with irritable bowel syndrome: a systematic review and meta-analysis

Article References: Xiang, P., Wang, X., Li, B., Li, H., Zheng, W., Fan, X., Jiao, J., Wang, Y., Li, J., & She, Y. (2026). Placebo response of sham acupuncture in patients with irritable bowel syndrome: a systematic review and meta-analysis. BMC Complementary Medicine and Therapies. https://doi.org/10.1186/s12906-026-05513-0

Image Credits: AI Generated

DOI: 10.1186/s12906-026-05513-0

Keywords: irritable bowel syndrome, sham acupuncture, placebo response, meta-analysis, systematic review, randomized controlled trials, IBS-SSS, gut-brain interaction, Rome IV criteria, abdominal pain, complementary medicine, clinical trial methodology

The research team, led by Yuedan Wang and Meiling She of the Institute of Digestive Diseases at Xiyuan Hospital of the China Academy of Chinese Medical Sciences, together with colleagues from several Chinese institutions, recruited twenty patients diagnosed with both diarrhea-predominant irritable bowel syndrome and nonerosive reflux disease, along with twenty matched healthy controls. Rather than examining a single biological layer, the investigators deployed three complementary technologies in parallel: untargeted liquid chromatography-mass spectrometry metabolomics on plasma, data-independent acquisition proteomics on the same blood samples, and 16S ribosomal RNA sequencing of fecal microbiota. The design allowed them to ask, for the first time in this patient group, whether the metabolic, protein-level, and microbial signatures of the comorbidity converge on shared pathways.

Before any molecule was measured, the team documented the human toll of the condition. Participants completed the short form-36 health survey and the hospital anxiety and depression scale, two validated instruments for quantifying quality of life and psychological distress. The results were striking in their selectivity. Patients showed largely preserved physical functioning, meaning they could carry out basic daily activities without major limitation. Yet their scores revealed severe deficits in role functioning, the capacity to fulfill work and social obligations, as well as in mental health and overall health perception. This pattern suggests that the burden of the combined disorders is felt less in mobility and more in mood, productivity, and subjective well-being, a profile consistent with the long-standing clinical observation that functional gut disorders and psychological distress travel together.

The molecular readout was enormous in scale. Plasma analysis identified 350 metabolites whose abundance differed significantly between patients and controls, while proteomics flagged 920 proteins present at divergent levels. These were not scattered changes. Pathway-level analysis revealed coordinated disruption across metabolic and immune-inflammatory systems, indicating that the comorbid state is accompanied by a systemic shift in how the body processes nutrients, signaling molecules, and inflammatory signals. The breadth of the perturbation underscores why single-biomarker studies of irritable bowel syndrome have struggled to produce a coherent picture: the disease state is not one broken circuit but a rewired network.

The fecal microbiome told a complementary story. Sequencing revealed enrichment of opportunistic pathogens alongside a depletion of beneficial commensal populations, the microbial allies that normally help ferment fiber, train the immune system, and maintain the gut barrier. This dysbiotic shift matters because gut microbes are not passive residents; they manufacture metabolites that enter the bloodstream, modulate immune tone, and communicate with the enteric and central nervous systems. A community tilted toward potential pathogens and away from protective species can therefore ripple outward, influencing physiology far beyond the colon wall.

When the researchers integrated all three data layers using Procrustes analysis, correlation networks, and random forest modeling, a central hub emerged: the microbiota-gut-brain axis. Among the shared pathways highlighted by the integrative analysis were forkhead box O signaling, a family of transcription factors governing oxidative stress responses and cellular survival; tryptophan metabolism, the biochemical route that feeds both serotonin synthesis and microbial indole production; and neuroactive ligand-receptor interactions, the molecular grammar of communication between nerves and their targets. That all three pathways sit at the intersection of microbial chemistry and neural signaling is precisely what one would expect if gut dysbiosis were helping to drive both intestinal symptoms and the reflux and mood disturbances that accompany them.

One of the most intriguing findings concerned a single bacterial genus. Klebsiella, an opportunistic pathogen enriched in the patients, showed a positive association with expression of monoamine oxidase A, the enzyme responsible for degrading monoamine neurotransmitters including serotonin, and a negative association with serotonin pathway metabolites. In other words, the more Klebsiella a patient carried, the more serotonin-degrading enzyme activity appeared and the fewer serotonin-related metabolites remained. Because serotonin is central to gut motility, visceral sensitivity, and mood regulation, a microbial influence on its availability offers a plausible mechanistic thread connecting diarrhea, reflux symptoms, and the anxiety and depression scores documented in the questionnaire data.

The study also ventured into the translational territory of diagnosis. Random forest modeling, a machine learning approach that evaluates which features best separate patient groups, identified a set of metabolites as potential diagnostic biomarkers for the comorbid condition. If validated in larger and more diverse cohorts, such a metabolic signature could eventually allow clinicians to distinguish patients whose overlapping symptoms share this molecular profile from those whose reflux and bowel complaints arise through different mechanisms, opening the door to more targeted therapies rather than the current trial-and-error approach.

The authors are careful about scope. With twenty patients and twenty controls, the study is a hypothesis-generating snapshot rather than a definitive population-level claim, and its cross-sectional design cannot establish whether microbial changes cause the disorders or result from them. The multi-omics integration, however, is what gives the work its force: convergent evidence from metabolites, proteins, and microbes pointing at the same axis is far harder to dismiss than any single measurement. The findings also carry practical implications for a condition often dismissed as purely psychological. If dysbiosis and disrupted neuroactive metabolism underlie the comorbidity, interventions aimed at restoring microbial balance, whether through diet, probiotics, or microbiota-targeted drugs, could plausibly address both gut and reflux symptoms simultaneously.

For now, the study stands as one of the most systematic molecular portraits yet of a patient group that has been clinically recognized but biologically neglected. It reframes diarrhea-predominant irritable bowel syndrome with concomitant nonerosive reflux disease not as two coincidental ailments but as a single integrated disturbance of the microbiota-gut-brain axis, one in which Klebsiella expansion, serotonin pathway disruption, forkhead box O signaling, and immune-inflammatory abnormalities form a coherent web. Confirming and extending that web will require longitudinal cohorts, intervention trials, and validation of the candidate biomarkers, but the direction of travel is clear. The gut, its microbes, and the brain are talking to each other, and in this debilitating comorbidity, the conversation appears to have gone badly wrong.

Subject of Research: Multi-omics analysis of diarrhea-predominant irritable bowel syndrome with concomitant nonerosive reflux disease

Article Title: Multi-omics analysis provides clues in understanding diarrhea-predominant irritable bowel syndrome with concomitant nonerosive reflux disease

Article References: Wang, Y., She, M., Fang, L., Zhang, J., Chen, T., Zhang, B., & Tang, X. (2026). Multi-omics analysis provides clues in understanding diarrhea-predominant irritable bowel syndrome with concomitant nonerosive reflux disease. Gut Pathogens. https://doi.org/10.1186/s13099-026-00868-8

Image Credits: AI Generated

DOI: 10.1186/s13099-026-00868-8

Keywords: irritable bowel syndrome, nonerosive reflux disease, microbiota-gut-brain axis, multi-omics, gut dysbiosis, metabolomics, proteomics, 16S rRNA sequencing, Klebsiella, serotonin metabolism, tryptophan metabolism, diagnostic biomarkers