BACKGROUND:T lymphocytes play a central role in the intestinal immune response in dogs with immunomodulator-responsive enteropathy (IRE), but the clinical relevance of mucosal T-cell infiltration remains unclear. HYPOTHESIS/OBJECTIVES:Compare mucosal CD3+ T-cell density between dogs with IRE and healthy comparison dogs across intestinal segments, and assess associations with clinical, biochemical, and histologic severity markers. ANIMALS:Forty-two client-owned dogs with IRE and 12 healthy research dogs. METHODS:Retrospective multicenter study. Archived endoscopic biopsy samples from the duodenum, ileum, and colon were evaluated using the Simplified Histopathological Scoring System. Immunohistochemistry for CD3 was quantified by digital image analysis (QuPath) and expressed as relative CD3+ density (RCD3). Group comparisons, receiver operating characteristic curve analyses, mixed linear models, and correlation analyses were performed. RESULTS:Relative CD3+ density was significantly higher in dogs with IRE than in comparison dogs in the duodenum (median, 6.34% vs 1.42%; P = .03), ileum (9.79% vs 0.85%; P < .001), and colon (3.88% vs 1.32%; P = .002). The area under the curve values were 0.833, 0.896, and 0.811, respectively. The RCD3 was not correlated with clinical indices, serum albumin concentration, or histologic scores, but ileal histologic score was negatively correlated with RCD3 (ρ = -0.37; P = .04). CONCLUSIONS AND CLINICAL IMPORTANCE:Mucosal CD3+ T-cell density is increased in dogs with IRE but is not associated with clinical or overall histologic disease severity. Quantification of CD3+ should not be used as a solitary monitoring tool but may contribute to immunophenotyping.

Rethinking response criteria of treatment of chronic enteropathy in dog is necessary, as clinical activity indices are widely used as primary endpoints despite substantial variability in how "response," "remission," and "relapse" are defined. Across recent studies, response thresholds range from modest relative reductions (eg, ≥25%) to stringent targets (eg, ≥75%), absolute score cut-offs, shifts between severity categories, or binary resolution of clinical signs. This methodological heterogeneity undermines comparability between trials and complicates evidence synthesis. An often-overlooked contributor to this issue is the intrinsic variability of the Canine Inflammatory Bowel Disease Activity Index and the Canine Chronic Enteropathy Clinical Activity Index, particularly their limited inter-observer reproducibility for total scores and several core items. When commonly used response thresholds overlap with expected measurement error, apparent clinical improvement might reflect scoring variability rather than true change in disease activity. We therefore propose a pragmatic framework for response classification anchored in the measurement properties of these instruments. For research endpoints, an absolute change of at least 4 points (Δ ≥ 4) is suggested as a conservative minimal detectable change to reduce misclassification of responders and non-responders. In dogs with low baseline scores driven by 1 or 2 isolated abnormalities, an item-centered approach (Δ item ≥2) might be more appropriate, particularly for variables such as stool consistency or defecation frequency. Finally, transparent reporting of scoring conditions, prioritization of evaluator consistency, and integration of complementary outcomes, including validated health-related quality-of-life measures and longitudinal symptom tracking, might help better capture clinically meaningful effects.

Proteolytic imbalance involving host and microbial serine proteases and their inhibitors (serpins) contributes to intestinal barrier disruption and chronic inflammation in inflammatory bowel disease (IBD). However, the interplay among these components remains insufficiently characterized. Here, we survey 13,304 publications over five decades, to map protease-serpin-microbiome literature in IBD. Our analysis reveals a fragmented literature structure, with uneven coverage and limited cross-domain integration among host proteases, microbial proteases, and inhibitory pathways. We synthesize evidence linking these components to intestinal barrier integrity, mucosal immunity, extracellular-matrix remodeling, and microbial ecology. Considering the protease-serpin-microbiome axis may provide an integrative direction for future studies of IBD pathogenesis, including the investigation of mechanisms underlying disease heterogeneity, prioritizing future biomarker and therapeutic studies.

Rethinking response criteria of treatment of chronic enteropathy in dog is necessary, as clinical activity indices are widely used as primary endpoints despite substantial variability in how "response," "remission," and "relapse" are defined. Across recent studies, response thresholds range from modest relative reductions (eg, ≥25%) to stringent targets (eg, ≥75%), absolute score cut-offs, shifts between severity categories, or binary resolution of clinical signs. This methodological heterogeneity undermines comparability between trials and complicates evidence synthesis. An often-overlooked contributor to this issue is the intrinsic variability of the Canine Inflammatory Bowel Disease Activity Index and the Canine Chronic Enteropathy Clinical Activity Index, particularly their limited inter-observer reproducibility for total scores and several core items. When commonly used response thresholds overlap with expected measurement error, apparent clinical improvement might reflect scoring variability rather than true change in disease activity. We therefore propose a pragmatic framework for response classification anchored in the measurement properties of these instruments. For research endpoints, an absolute change of at least 4 points (Δ ≥ 4) is suggested as a conservative minimal detectable change to reduce misclassification of responders and non-responders. In dogs with low baseline scores driven by 1 or 2 isolated abnormalities, an item-centered approach (Δ item ≥2) might be more appropriate, particularly for variables such as stool consistency or defecation frequency. Finally, transparent reporting of scoring conditions, prioritization of evaluator consistency, and integration of complementary outcomes, including validated health-related quality-of-life measures and longitudinal symptom tracking, might help better capture clinically meaningful effects.

BACKGROUND:Chronic enteropathies (CEs) in dogs substantially impact the quality of life (QoL) for both patients and owners. Existing clinical indices do not capture the broader burden of disease, and no validated health-related QoL (HRQoL) tool exists for CE. HYPOTHESIS/OBJECTIVES:Develop and validate a psychometrically sound HRQoL questionnaire for dogs with CE. ANIMALS:A total of 351 client-owned dogs: 141 with CE, 126 healthy, and 84 with other chronic diseases (OCD), based on owner classification. METHODS:A multi-phase psychometric study was conducted to create and validate the instrument. Items were generated from literature and expert input, refined using cognitive debriefing and statistical filtering, and tested for internal consistency, construct validity, and discriminative validity. The HRQoL scores were compared among groups and analyzed for demographic factors. RESULTS:The final Canine Chronic Enteropathy QoL (CCEQoL) questionnaire included 33 items. Internal consistency was excellent (Cronbach's α = 0.91). The median total score (TS) was higher in CE dogs (129; interquartile range [IQR], 73.5-181.5) than in OCD dogs (62; IQR, 31.3-105.4) and healthy dogs (15.3, IQR, 6-34; P < .001). The total score was inversely correlated with owner-rated overall QoL (ρ = -0.61; P < .001). In CE dogs, the TS was weakly and inversely correlated with age but was not significantly associated with breed size, comorbidities, or country of residence. CONCLUSIONS AND CLINICAL IMPORTANCE:The CCEQoL is the first validated HRQoL tool for dogs with CE. It provides a structured, multidimensional assessment of disease burden and may enhance patient-centered care, owner-veterinarian communication, and clinical research.

The Canine Inflammatory Bowel Disease Activity Index (CIBDAI) and Canine Chronic Enteropathy Clinical Activity Index (CCECAI) are key tools for monitoring chronic enteropathies (CE) in dogs. Despite their widespread use, concerns persist regarding their intra-observer repeatability and inter-observer reproducibility, which may impact clinical and research applications. This study evaluated the reliability of these indices through a two-phase approach using anonymized clinical records. In Phase 1, two observers independently scored 41 consultation forms twice, one month apart, to assess repeatability and reproducibility. Phase 2 involved four observers with varying expertise who scored 59 forms using a standardized guide addressing Phase 1 inconsistencies. Statistical methods included Lin’s concordance correlation coefficient and Bland-Altman plots. High intra-observer repeatability was observed for most variables, but inter-observer reproducibility was limited for CIBDAI, CCECAI, and fluctuating parameters like stool consistency and defecation frequency. The standardized guide marginally improved consistency but did not resolve discrepancies. Expert evaluators did not consistently outperform non-experts. Reproducibility declined in more clinically severe cases. These findings highlight the need for standardized training, dynamic scoring systems, and digital tools to enhance reliability. Addressing these limitations is critical to improve clinical decision-making and research outcomes in canine CE.

An uncontrolled activity of neutrophil serine proteases (NSPs) contributes to inflammatory diseases. Cathepsin C (CatC) is known to activate NSPs during neutrophilic differentiation and represents a promising pharmacological target in NSP-mediated diseases. In humans, Papillon-Lefèvre syndrome (PLS) patients have mutations in theirCTSC gene, resulting in the complete absence of CatC activity. Despite this, low residual NSP activities are detected in PLS neutrophils (<10% vs healthy individuals), suggesting the involvement of CatC-independent proteolytic pathway(s) in the activation of proNSPs. This prompted us to characterize CatC-independent NSP activation pathways by blocking proCatC maturation. In this study, we show that inhibition of intracellular CatS almost completely blocked CatC maturation in human promyeloid HL-60 cells. Despite this, NSP activation was not significantly reduced, confirming the presence of a CatC-independent activation pathway involving a CatC-like protease that we termed NSPs-AAP-1. Similarly, when human CD34+ progenitor cells were treated with CatS inhibitors during neutrophilic differentiation in vitro, CatC activity was nearly abrogated but ∼30% NSP activities remained, further supporting the existence of NSPs-AAP-1. Our data indicate that NSPs-AAP-1 is a cysteine protease that is inhibited by reversible nitrile compounds designed for CatC inhibition. We further established a proof of concept for the indirect, although incomplete, inhibition of NSPs by pharmacological targeting of CatC maturation using CatS inhibitors. This emphasizes the potential of CatS as a therapeutic target for inflammatory diseases. Thus, preventing proNSP maturation using a CatS inhibitor, alone or in combination with a CatC/NSPs-AAP-1 inhibitor, represents a promising approach to efficiently control the extent of tissue injury in neutrophil-mediated inflammatory diseases.

Chronic digestive disorders are of increasing incidence worldwide with expensive treatments and no available cure. Available therapeutic schemes mainly rely on symptom relief, with large degrees of variability in patients' response to such treatments, underlining the need for new therapeutic strategies. There are strong indications that the gut microbiota's contribution seems to be a key modulator of disease activity and patients' treatment responses. Hence, efforts have been devoted to understanding host-microbe interactions and the mechanisms underpinning such variability. Animal models, being the gold standard, provide valuable mechanistic insights into host-microbe interactions. However, they are not exempt from limitations prompting the development of alternative methods. Emerging microfluidic technologies and gut-on-chip models were shown to mirror the main features of gut physiology and disease state, reflect microbiota modification, and include functional readouts for studying host responses. In this commentary, we discuss the relevance of animal models in understanding host-microbe interactions and how gut-on-chip technology holds promises for addressing patient variability in responses to chronic digestive disease treatment.

Cathepsin C (CatC, syn. Dipeptidyl peptidase I) is a lysosomal cysteine proteinase expressed in several tissues including inflammatory cells. This enzyme is important for maintaining multiple cellular functions and for processing immune cell-derived proteases. While mutations in the CatC gene were reported in Papillon-Lefèvre syndrome, a rare autosomal recessive disorder featuring hyperkeratosis and periodontitis, evidence from clinical and preclinical studies points toward pro-inflammatory effects of CatC in various disease processes that are mainly mediated by the activation of neutrophil serine proteinases. Moreover, tumor-promoting effects were ascribed to CatC. The aim of this review is to highlight current knowledge of the CatC as a potential therapeutic target in inflammatory disorders.

BACKGROUND:The gut microbiota and derived metabolites play a key role in regulating host physiology. Diet is identified as a key regulatory factor of the microbiota composition and, potentially, of subsequent functionalities. Demonstrating the role of diet may be complex as most human studies are cross-sectional and dietary intervention is often accompanied by hygienic changes. The objective of the present study was to investigate the impact of an industrial diet on the modulation of the microbiota and targeted functionalities using a canine "natural" model. RESULTS:We carried out a controlled dietary trial in a cohort of Tunisian semi-stray dogs. We made a transition from a natural diet to an industrial kibble diet and monitored the composition of the fecal microbiota, the concentration of short-chain fatty acids (SCFA) and bile acids (BAs), and protease activities. We demonstrated that dietary change significantly decreased fecal primary bile acids levels and protease activities. Interestingly, correlation analyses demonstrated that variation of specific microbial genera were associated with modulated physiological parameters. CONCLUSIONS:Our study reveals that an industrial diet induces beneficial changes in microbial composition and functions characterised by increased diversity, synthesis of SCFA and secondary bile acids production, stressing the key role of the diet-microbiota-dog crosstalk.

In cats and humans, several physiological and environmental factors have been shown to alter the gut microbiota of healthy individuals. Cats share several diseases with humans such as inflammatory bowel diseases and low-grade intestinal T-cell lymphoma. The physiopathology of these chronic enteropathies is poorly understood but may involve disequilibrium of the gut microbiota composition and disruption of normal microbiome activity profiles. These disorders are increasingly diagnosed in the feline species due to improved medicalization and easier access to endoscopy in veterinary practice. This review addresses the current data on the gut microbiota of cats in health and in chronic enteropathies. Such functional analysis will help the advancement of innovative diagnostic tools and targeted therapeutic strategies.

Insects rely on carbohydrates such as starch and glycogen as an energy supply for growth of larvae and for longevity. In this sense α-amylases have essential roles under extreme conditions, e.g., during nutritional or temperature stress, thereby contributing to survival of the insect. This makes them interesting targets for combating insect pests. Drosophila melanogaster α-amylase, DMA, which belongs to the glycoside hydrolase family 13, sub family 15, has been studied from an evolutionary, biochemical, and structural point of view. Our studies revealed that the DMA enzyme is active over a broad temperature and pH range, which is in agreement with the fluctuating environmental changes with which the insect is confronted. Crystal structures disclosed a new nearly fully solvated metal ion, only coordinated to the protein via Gln263. This residue is only conserved in the subgroup of D. melanogaster and may thus contribute to the enzyme adaptive response to large temperature variations. Studies of the effect of plant inhibitors and the pseudo-tetrasaccharide inhibitor acarbose on DMA activity, allowed us to underline the important role of the so-called flexible loop on activity/inhibition, but also to suggest that the inhibition modes of the wheat inhibitors WI-1 and WI-3 on DMA, are likely different.

Serine proteases are involved in many biological processes and are associated with irritable bowel syndrome (IBS) pathology. An increase in serine protease activity has been widely reported in IBS patients. While most of the studies focused on host proteases, the contribution of microbial proteases are poorly studied. In the present study, we report the analysis of proteolytic activities in fecal samples from the first Tunisian cohort of IBS-M patients and healthy individuals. We demonstrated, for the first time, that metalloproteases activities were fourfold higher in fecal samples of IBS patients compared to controls. Of interest, the functional characterization of serine protease activities revealed a 50-fold increase in trypsin-like activities and a threefold in both elastase- and cathepsin G-like activities. Remarkably, we also showed a fourfold increase in proteinase 3-like activity in the case of IBS. This study also provides insight into the alteration of gut microbiota and its potential role in proteolytic modulation in IBS. Our results stressed the impact of the disequilibrium of serine proteases, metalloproteases and gut microbiota in IBS and the need of the further characterization of these targets to set out new therapeutic approaches.

The gut microbiota is now considered as a key player in the development of metabolic dysfunction. Therefore, targeting gut microbiota dysbiosis has emerged as a new therapeutic strategy, notably through the use of live gut microbiota-derived biotherapeutics. We previously highlighted the anti-inflammatory abilities of two Parabacteroides distasonis strains. We herein evaluate their potential anti-obesity abilities and show that the two strains induced the secretion of the incretin glucagon-like peptide 1 in vitro and limited weight gain and adiposity in obese mice. These beneficial effects are associated with reduced inflammation in adipose tissue and the improvement of lipid and bile acid metabolism markers. P. distasonis supplementation also modified the Actinomycetota, Bacillota and Bacteroidota taxa of the mice gut microbiota. These results provide better insight into the capacity of P. distasonis to positively influence host metabolism and to be used as novel source of live biotherapeutics in the treatment and prevention of metabolic-related diseases.

Inflammatory bowel diseases (IBDs) have emerged as a public health problem worldwide with a limited number of efficient therapeutic options despite advances in medical therapy. Although changes in the gut microbiota composition are recognized as key drivers of dysregulated intestinal immunity, alterations in bile acids (BAs) have been shown to influence gut homeostasis and contribute to the pathogenesis of the disease. In this review, we explore the interactions involving BAs and gut microbiota in IBDs, and discuss how the gut microbiota–BA–host axis may influence digestive inflammation.

Accumulating data show the involvement of intestinal microbiota in the development and maintenance of numerous diseases. Many environmental factors influence the composition and function of the gut microbiota. An animal model subjected to the same environmental constraints that will allow better characterization of the microbiota–host dialogue is awaited. The domestic dog has physiological, dietary and pathological characteristics similar to those of humans and shares the domestic environment and lifestyle of its owner. This review exposes how the domestication of dogs has brought them closer to humans based on their intrinsic and extrinsic similarities which were discerned through examining and comparing the current knowledge and data on the intestinal microbiota of humans and canines in the context of several spontaneous pathologies, including inflammatory bowel disease, obesity and diabetes mellitus.