Introduction

Irritable bowel syndrome (IBS) is defined as a disorder of gut-brain interaction (DGBI) and is characterised by intestinal immune activation, increased intestinal permeability, and structural and functional brain alterations. DGBI patients have a higher prevalence of psychological comorbidities. Nevertheless, the exact pathophysiological link between these factors and the sequence of events is unknown. Gut alterations have been suggested to induce brain neuroinflammation in DGBI, but scientific evidence is lacking.

Aims & Methods

The present study aims to assess whether GI alteration induces brain neuroinflammation, alters brain function, and, consequently, induces psychological comorbidities. A unique longitudinal study was conducted from 30 to 220 days of age to establish the chronological sequence of intestinal and neurological changes. For this, we utilised the BioBreeding diabetes-prone (BBDP) rat model, which spontaneously develops intestinal inflammation, increased permeability, and colonic hypersensitivity^{1, 2}and has been employed as a model of DGBI. The BioBreeding diabetes-resistant (BBDR) was used as control. Anxiety-like behaviour was assessed using the elevated plus maze. Intestinal permeability was assessed in vivo by measuring the passage of 4 kDa and 70 kDa dextrans into the blood, thereby evaluating paracellular and transcellular permeability, respectively. The appearance of red colour, given by the mixture of the dextrans in the stools, was used to assess overall intestinal motility. The blood-brain barrier (BBB) integrity and brain metabolic profile were assessed using contrast-enhanced magnetic resonance imaging (0.25 mL/100g weight of 0.05 mM, gadolinium) and proton magnetic resonance spectroscopy, respectively.

Results

BBDP rats exhibit an increased colonic permeability starting from 90 days, and reduced GI motility at 90 and 160 days. Interestingly, this increased permeability is accompanied by an increased BBB permeability at 220 days only in the anterior cingulate cortex (ACC) but not in the hippocampus, insula, amygdala, or thalamus. BBDP rats showed a slight increase in total choline and myoinositol concentrations in the ACC and the insula at late time points, which may indicate increased neuroinflammation. BBDP rats also have higher concentrations of glutamine-glutamate in the insula and N-acetyl aspartate in the ACC. Moreover, BBDP rats develop anxiety-like behaviour at 160 and 220 days.

Conclusion

The BBDP rat model supports the current hypothesis that increased gut permeability can lead to brain neuroinflammation, altered function, and, consequently, to psychological comorbidities.
EU-funded DISCOvERIE project (No. 848228).

References

1. Meleine M, Accarie A, Wauters L, et al. Colonic hypersensitivity and low-grade inflammation in a spontaneous animal model for functional gastrointestinal disorders. Neurogastroenterol Motil 2019;31:e13614.
2. Vanuytsel T, Vanormelingen C, Vanheel H, et al. From intestinal permeability to dysmotility: the biobreeding rat as a model for functional gastrointestinal disorders. PLoS One 2014;9:e111132.

Introduction

Genome-wide association studies (GWAS) have identified more than 250 risk variants linked to inflammatory bowel disease (IBD). Most genetic variants increase the risk of disease onset, and their impact on clinical presentation is limited.^1,2,3 Variants in NOD2 and IL23R not only modulate the risk of disease onset, but also influence disease behaviour and localisation. Their role in predicting treatment response remains unclear.^3,4
A variant in an intron of TNRC18 (rs7486781, allele frequency 3.6%) was recently identified as having a strong risk-increasing effect (OR 3.2, p=2.4x10-61) for IBD in the FinnGen biobank study. The same allele was also associated with a risk for ankylosing spondylitis (AS), uveitis and psoriasis.⁵ The functional effect of rs7486781 is not yet fully established.⁶

Aims & Methods

The FinnGen biobank study includes the genotype data of 520 000 individuals and their longitudinal register data from national health registers, including 11 298 individuals with verified diagnosis for IBD. The data also include drug purchases, procedure codes and laboratory measurements of the individuals.
Our aim was to study the impact of the TNRC18-variant on IBD phenotype, particularly disease behavior. We assessed established aspects of disease severity⁷: use of immunosuppressants and advanced therapies, necessity to switch medications, frequent use of corticosteroids and risk of procedures. We also evaluated the presence of extraintestinal manifestations (EIM) and other disease complications.

Results

Regarding disease severity, the use of therapies beyond 5-ASA was more common among variant carriers; the use of thiopurines and other immunosuppressants (OR 1.21-1.27, p-values 1.35x10^-5 - 0.00849), ustekinumab and other IL-inhibitors (OR 1.46-1.48, p-values 0.00324 - 0.00286) and TNF-α-inhibitors (OR 1.26, p=0.00753) was more frequent.
In addition, perianal and anal canal operations were more prevalent with TNRC18 variant carriers (OR 2.44, p=1.41x10^-4), indicating perianal disease.
Assessing EIM, we observed that diagnoses for AS and uveitis (OR 1.62-1.67, p=1.3x10^-5 - 1.55x10^-4) were more frequent within IBD in patients with rs7486781.
Interestingly, a reduced risk of primary sclerosing cholangitis (PSC) was implicated by lower number of cholangitis (K83.0) diagnoses (OR 0.617, p=0.00221) and fewer purchases of ursodeoxycholic acid (OR 0.55, p=2.83x10^-5), in addition to lower levels of ALP (mean 75 vs 82, p=0.00296), IgG4 (mean 0.45 g/l vs 0.81 g/l, p=4.81x10^-5) and IgM (0.12 vs 0.15, p=0.00115) among variant carriers. All events survived the false discovery rate–adjusted p threshold of 0.05.
Our results also suggest that the cumulative risk for IBD related procedures⁸ (patients with procedures n=2209) from diagnosis and birth were elevated in TNRC18 variant carriers (HR=1.12 and HR=1.14, p=0.050 and p=0.023, assuming additive effect) using a Cox regression model.
Finally, our results in ulcerative colitis indicate that TNRC18 variant carriers are at higher risk of transitioning from 5-ASA/immunomodulators to biologics/JAK-inhibitors (HR=1.38, p=0.016). Variant carriers receiving immunomodulators or advanced therapies were not, however, in increased risk of colectomy (HR~0.97-1.34, p~0.86-0.37).

Conclusion

TNRC18 variant was associated with greater risk of operative treatment, the need of more advanced medication and perianal disease. AS and uveitis were more common EIMs, but PSC appeared less infrequent. Our preliminary results indicate that TNRC18 variant carriers might benefit from early intervention with immunomodulators or advanced therapies.

References

1. Chang, J. T. Pathophysiology of Inflammatory Bowel Diseases. N Engl J Med 383, 2652–2664 (2020).

2. Cleynen, I. et al. Inherited determinants of Crohn’s disease and ulcerative colitis phenotypes: a genetic association study. Lancet 387, 156–167 (2016).

3. Atreya, R. & Neurath, M. F. Biomarkers for Personalizing IBD Therapy: The Quest Continues. Clin Gastroenterol Hepatol 22, 1353–1364 (2024).

4. Kayali, S. et al. NOD2 and Crohn’s Disease Clinical Practice: From Epidemiology to Diagnosis and Therapy, Rewired. Inflamm Bowel Dis 31, 552–562 (2025).

5. Kurki, M. I. et al. FinnGen provides genetic insights from a well-phenotyped isolated population. Nature 613, 508–518 (2023).

6. Rahimov, F. et al. A genome-wide CRISPR screen supported by human genetics identifies the TNRC18 gene locus as a novel regulator of inflammatory signaling. bioRxiv 2023.10.04.560902 (2023) doi:10.1101/2023.10.04.560902.

7. Swaminathan, A. et al. The Disease Severity Index for Inflammatory Bowel Disease Is a Valid Instrument that Predicts Complicated Disease. Inflamm Bowel Dis 30, 2064–2075 (2024).

Disclosure

Anna Aarni: Speaker fee from Abbvie, Clinic visit: travelling expenses from Tillots Pharma

Pauliina Molander: Speaker, consultancy and advisory board member fees from Abbvie, Johnson & Johnson, Lilly, Pfizer and Takeda. Clinic visit: traveling expenses from Tillots Pharma

Jukka Koskela: Pfizer-FinnGen genetic advisory board, traveling, clinic and congress visits: FinnGen partners, Tillots Pharma, Takeda, consulting: Pfizer

Introduction

Irritable bowel syndrome (IBS), the most prevalent gastrointestinal disorder globally, has a significant impact on the quality of life of 10 - 15% of the population, with a higher prevalence among women than men. Despite the identification of certain contributing factors, the pathophysiology of IBS remains largely unknown.

Aims & Methods

We firstly performed Genome-wide association study (GWAS) on the IBS cohort from the All of Us Research Program and adjusted for sex, age, and top 10 principal components. We conducted GWAS meta-analyses of IBS and its subtypes in 80,737 IBS cases and 1,019,143 asymptomatic control subjects from five independent cohorts (All of Us Research Program, UK Biobank, Bellygenes, Genetic Epidemiology Research on Aging, FinnGen). IBS risk loci were functionally annotated to identify candidate genes. Systematic variant-level analysis, including variants annotation, functional genomics and expression quantitative trait loci, prioritized potential causal variants. Gene-level analyses, including transcriptome-wide association study, colocalization analysis and Mendelian randomization, nominated the potential causal genes.

Results

We identified two independent IBS susceptibility loci at genome-wide significance (P < 5 × 10⁻⁸) in All of Us Research Program cohort totaling 14,897 cases and 245,388 controls. GWAS-meta analysis identified 12 novel independent (P < 5×10^-8) signals and 5 unreported loci (rs143348218, rs3748618, rs6432674, rs9536395, rs976714). Subtype-specific (P < 5×10^-8) findings based on subtype-specific GWAS meta-datasets included 3 loci for subtype IBS-C (3 novel independent loci) , 44 loci for IBS-M (2 novel independent loci). By integrating evidence from layers of different analyses, we prioritized the most plausible causal genes for IBS including CADM2, PCLO, PHF2 and SHISA6. Notably, PCLO (associated with bipolar disorder and major depressive disorder) and SHISA6 (overexpression in Platelet and T-lymphocyte) have been previously unreported in association with IBS.

Conclusion

Our study not only showed the power of the last large-scale GWAS in deciphering the genetic aetiology of IBS, but also uncovered 5 new genetic risk variants, potential unreported causal variants, genes and therapeutic targets for IBS.

References

1 Chey WD, Kurlander J, Eswaran S. Irritable bowel syndrome: a clinical review. JAMA. 2015;313:949–58. doi: 10.1001/jama.2015.0954
2 Soubieres A, Wilson P, Poullis A, et al. Burden of irritable bowel syndrome in an increasingly cost-aware National Health Service. Frontline Gastroenterology. 2015;6:246–51. doi: 10.1136/flgastro-2014-100542
3 Eijsbouts C, Zheng T, Kennedy NA, et al. Genome-wide analysis of 53,400 people with irritable bowel syndrome highlights shared genetic pathways with mood and anxiety disorders. Nat Genet. 2021;53:1543–52. doi: 10.1038/s41588-021-00950-8
4 Bonfiglio F, Zheng T, Garcia-Etxebarria K, et al. Female-Specific Association Between Variants on Chromosome 9 and Self-Reported Diagnosis of Irritable Bowel Syndrome. Gastroenterology. 2018;155:168–79. doi: 10.1053/j.gastro.2018.03.064
5 DeBoever C, Tanigawa Y, Aguirre M, et al. Assessing Digital Phenotyping to Enhance Genetic Studies of Human Diseases. Am J Hum Genet. 2020;106:611–22. doi: 10.1016/j.ajhg.2020.03.007
6 Venner E, Muzny D, Smith JD, et al. Whole-genome sequencing as an investigational device for return of hereditary disease risk and pharmacogenomic results as part of the All of Us Research Program. Genome Med. 2022;14:34. doi: 10.1186/s13073-022-01031-z
7 Weeks EM, Ulirsch JC, Cheng NY, et al. Leveraging polygenic enrichments of gene features to predict genes underlying complex traits and diseases. Nat Genet. 2023;55:1267–76. doi: 10.1038/s41588-023-01443-6

Introduction

The interplay of diet and the intestinal microbiome plays a key role in developing colorectal cancer (CRC), with westernization of diets, e.g., an increase in fat and sugar and a decrease in fiber content, being the main contributor. We recently demonstrated that the endoplasmic reticulum unfolded protein response (ER-UPR) effector activating transcription factor 6 (ATF6) is associated with early and late onset of CRC in patients. Furthermore, the overexpression of ATF6 observed in a subset of CRC patients is associated with the presence of certain gut bacteria. The specific expression of activated ATF6 (nATF6) in mouse intestinal epithelial cells (nATF6^IEC) induces spontaneous development of colonic tumors in a microbiota-dependent manner, highlighting the functional relevance of ATF6 as a novel oncogenic driver.

Aims & Methods

To elucidate the adverse role of dietary fat, sugar, and fiber in tumorigenesis, we exposed nATF6^IEC mice under SPF conditions to control (chow) and westernized diets for 7 weeks after weaning. Microbial and metabolite profiles were assessed through deep metagenomic sequencing and targeted/untargeted mass spectrometry (LC-MS) analysis. Microbiota transfer of diet-exposed mice into germ-free recipients was conducted to verify the microbiota-dependent transmissibility of tumor formation. Bismuth(II)subsalicylate (BSS) was used as a dietary additive to validate the impact of bacteria-produced H₂S on tumorigenesis.

Results

Westernized high lard (HL) diet, enriched in fat and sugar and depleted in fermentable fiber, increased tumor burden in biallelic nATF6^IEC mice. Unexpectedly, HL induced de novo tumorigenesis in otherwise tumor-free monoallelic nATF6^IEC mice. Surprisingly, modifying the HL diet by supplementing dietary fiber or lowering fat content failed to protect the HL-induced tumorigenic phenotype. Metabolite profiling clearly differentiated westernized from control diets and tumor bearing from control mice. Transferring microbiota from diet-exposed mice into germ-free nATF6^IEC mice was sufficient to trigger tumorigenesis. Metagenomic profiles of westernized diet-exposed mice identified an increased relative abundance of H₂S-producing Desulfovibrio species and genes related to dissimilatory sulfate reduction. Supplementing westernized diets with the H₂S-scavenger BSS resulted in a drastic change in microbial communities as well as the prevention of tumor formation in monoallelic nATF6^IEC mice.

Conclusion

These results highlight the ability of westernized diets to enhance nATF6-related tumorigenesis while altering metabolite and microbial profiles. Westernized diets favor the growth of sulfate-reducing Desulfovibrionaceae, possibly resulting in increased H₂S production. H₂S scavenging significantly reduces diet-induced colonic tumor susceptibility, clearly demonstrating the impact of diet in shaping cancer-related microbiome alterations.

Introduction

Immune checkpoint inhibitors (ICIs) have marked a breakthrough in the management of a wide range of cancer types, leading to increased overall survival. However, this treatment is frequently associated with the onset of various immune-related adverse events (irAEs), including ICI-related diarrhea and colitis.¹ Current recommendations for patients with diarrhea or colitis grade 2 or higher (graded via CTCAE)² include the discontinuation of ICI and administration of immune suppressants (e.g. steroids or biologics), which may lead to worse outcomes in these patients.³ Therefore, alternative therapeutic strategies to manage irAEs are needed. The gut microbiota plays a pivotal role in the onset of gastrointestinal irAEs, but the role of its therapeutic modulation on these disorders is mostly unknown. ^4,5

Aims & Methods

Our aim was to evaluate the efficacy and safety of therapeutic microbiome modulation for gastrointestinal irAEs in cancer patients. We enrolled cancer patients affected by ICI-related diarrhea/colitis referred to our Microbiome Clinic from January 2023 to March 2025. After clinical evaluation, patients were stratified according to severity of diarrhea (graded via CTCAE)² and then received a microbiome-modulating therapy. Patients were followed-up for at least 8 week after the initiation of therapy. We collected data about patient demographics (age and gender), patient’s overall health status as assessed by the the Charlson Comorbidity Index (CCI)⁶, type of cancer, oncological therapy and its suspension, time in weeks from initiation of cancer therapy to onset of diarrhea, severity of diarrhea (graded via CTCAE)², time in weeks until resolution of diarrhea and resumption of oncological therapy

Results

We enrolled 42 patients in the study period (8 males, 34 females, mean age 58,3 years-old, mean CCI-index 5.8). All patients were treated with ICI (Pembrolizumab: n=25 , Dostarlimab: n=4, Nivolumab: n=4; Atezolizumab: n=3; Novulumab and Ipilumab: n=2, Cemiplimab: n=2; Mogamulizumab: n=1; Pertuzumab: n=1). Ten patients experienced G1 diarrhea (23,8%), 16 (38,1) G2, 15 (35,7%) G3 and one G4 (2,4%). As indicated by current European Guidelines³, 30 patients (71,4%) had to interrupt ICI due to diarrhea. Multi-strain probiotics were administered to 27 (64.3% ) patients, rifaximin to 22 (52,4%). Overall, 21 patients (50%) needed therapy with systemic steroids. Seven patients who experienced ICI-related colitis refractory to steroids and biologics were successfully treated with FMT. Twenty-eight patients (66.7% ) had a resolution of the diarrhea (G0) and 11 patients (26.2%) had diarrhea G1 at a mean time of 8 weeks. Upon resolution of diarrhea, nine of the 30 patients who had interrupted ICI (30%) were able to resume the treatment. None of the patients experienced any adverse event related to gut microbiota modulation as defined by CTCAE².

Conclusion

Therapeutic modulation of gut microbiota appears to be a promising safe and effective approach for treating ICI-related diarrhea and colitis. However, these preliminary findings need confirmation through more consolidated and well-designed studies.

References

1. Dougan M, Wang Y, Rubio-Tapia A, Lim JK. AGA Clinical Practice Update on Diagnosis and Management of Immune Checkpoint Inhibitor Colitis and Hepatitis: Expert Review. Gastroenterology. 2021;160(4):1384-1393. doi:10.1053/j.gastro.2020.08.063
2. Freites-Martinez A, Santana N, Arias-Santiago S, Viera A. Using the Common Terminology Criteria for Adverse Events (CTCAE - Version 5.0) to Evaluate the Severity of Adverse Events of Anticancer Therapies. Actas Dermosifiliogr. 2021;112(1):90-92. doi:10.1016/j.ad.2019.05.009
3. Haanen J, Obeid M, Spain L, et al. Management of toxicities from immunotherapy: ESMO Clinical Practice Guideline for diagnosis, treatment and follow-up. Ann Oncol. 2022;33(12):1217-1238. doi:10.1016/j.annonc.2022.10.001
4. Wang Y, Wiesnoski DH, Helmink BA, et al. Fecal microbiota transplantation for refractory immune checkpoint inhibitor-associated colitis. Nat Med. 2018;24(12):1804-1808. doi:10.1038/s41591-018-0238-9
5. Wang T, Zheng N, Luo Q, et al. Probiotics Lactobacillus reuteri Abrogates Immune Checkpoint Blockade-Associated Colitis by Inhibiting Group 3 Innate Lymphoid Cells. Front Immunol. 2019;10. doi:10.3389/fimmu.2019.01235
6. Charlson ME, Pompei P, Ales KL, MacKenzie CR. A new method of classifying prognostic comorbidity in longitudinal studies: Development and validation. J Chronic Dis. 1987;40(5):373-383. doi:10.1016/0021-9681(87)90171-8

Disclosure

G.I. has received personal fees for acting as speaker for Biocodex, Danone, Sofar, Malesci, Metagenics and Tillotts Pharma, and for acting as consultant and/or advisor for Ferring Therapeutics, Giuliani, Malesci and Tillotts Pharma. A.G. reports personal fees for consultancy from Eisai Srl, 3PSolutions, Real Time Meeting, Fondazione Istituto Danone, SinergieSrl, Board MRGE and Sanofi SpA personal fees for acting as a speaker for Takeda SpA, AbbVie and Sandoz SpA and personal fees for acting on advisory boards for VSL3 and Eisai. G.C. has received personal fees for acting as advisor for Ferring Therapeutics. All other authors have no conflicts of interest to disclose.