Identification of Novel Biomarkers in Cats with Chronic Enteropathies

Feline chronic enteropathy is a very common disorder with an increasing prevalence over the past decades. It mainly comprises idiopathic inflammatory bowel disease (IBD) and alimentary small cell lymphoma (SCL). Histopathology, immunohistochemistry, and clonality testing are currently considered to be the gold standard for the diagnosis and differentiation of IBD from SCL. The performance of these tests in a cohort of clinically healthy client-owned cats with similar demographic characteristics was evaluated. To characterize the mucosal proteome of cats with chronic enteropathy and to identify novel biomarker candidates, two-dimensional fluorescence difference gel electrophoresis was performed on intestinal biopsies. To characterize the fecal microbiome and metabolome, 16S rRNA sequencing and ultra-performance liquid chromatography were performed on fecal samples from cats with chronic enteropathy. Histopathology, immunohistochemistry, and clonality testing in healthy cats frequently revealed findings that are considered abnormal based on the currently accepted standards. Tests that are currently considered to be the gold standard for the diagnosis of feline chronic enteropathy should be interpreted with caution. Several potential protein biomarkers were identified in the intestinal mucosa of cats with CE. Among the identified proteins were those of the annexin and apolipoprotein families, and malate dehydrogenases. Characterization of the fecal microbiome of cats with chronic enteropathy revealed a dysbiosis pattern that has previously been described across different species with intestinal inflammation. The dysbiosis was characterized by a significantly reduced alpha diversity and trends for increased facultative anaerobic bacteria (e.g., Enterobacteriaceae) in favor of obligate anaerobic bacteria. However, the overall dysbiotic pattern did not differ between cats with IBD and cats with SCL. Characterization of the fecal metabolome revealed global metabolic changes in cats with chronic enteropathy with many pathways involved such as the tryptophan pathway, amino acids, sphingolipids, and sterols. However, the global metabolic pattern did not differ between cats with IBD and SCL. Further work is needed to verify these findings and confirm their promise for the development of a clinically useful biomarker or biomarker panel for the definitive diagnosis and sub-classification of feline chronic enteropathy

Characterization of the fecal microbiome in cats with inflammatory bowel disease or alimentary small cell lymphoma.

Feline chronic enteropathy (CE) is a common gastrointestinal disorder in cats and mainly comprises inflammatory bowel disease (IBD) and small cell lymphoma (SCL). Both IBD and SCL in cats share features with chronic enteropathies such as IBD and monomorphic epitheliotropic intestinal T-cell lymphoma in humans. The aim of this study was to characterize the fecal microbiome of 38 healthy cats and 27 cats with CE (13 cats with IBD and 14 cats with SCL). Alpha diversity indices were significantly decreased in cats with CE (OTU p = 0.003, Shannon Index p = 0.008, Phylogenetic Diversity p = 0.019). ANOSIM showed a significant difference in bacterial communities, albeit with a small effect size (P = 0.023, R = 0.073). Univariate analysis and LEfSE showed a lower abundance of facultative anaerobic taxa of the phyla Firmicutes (families Ruminococcaceae and Turicibacteraceae), Actinobacteria (genus Bifidobacterium) and Bacteroidetes (i.a. Bacteroides plebeius) in cats with CE. The facultative anaerobic taxa Enterobacteriaceae and Streptococcaceae were increased in cats with CE. No significant difference between the microbiome of cats with IBD and those with SCL was found. Cats with CE showed patterns of dysbiosis similar to those in found people with IBD

Results of histopathology, immunohistochemistry, and molecular clonality testing of small intestinal biopsy specimens from clinically healthy client‐owned cats

BackgroundHistopathology, immunohistochemistry, and molecular clonality testing are metrics frequently used to diagnose chronic enteropathy (CE) in cats. However, normal values for these metrics have been based mainly on samples from cats that were relatively young, specific pathogen-free, or both.ObjectivesTo describe results of histopathology, immunohistochemistry, and clonality testing of endoscopically-derived biopsy specimens of the upper small intestinal tract from a cohort of clinically healthy client-owned cats.AnimalsTwenty clinically healthy client-owned cats ≥3 years of age.MethodsTissue specimens were collected from the stomach and duodenum and evaluated single blinded by a board-certified pathologist. In addition, samples were evaluated by routine immunohistochemistry and clonality testing. Cats were followed after the procedure for signs of CE.ResultsIntegrated results from histopathology, immunohistochemistry, and clonality testing were interpreted as consistent with small cell lymphoma (SCL; n = 12), emerging SCL (n = 1), lymphocytic enteritis (n = 6), and pseudoclonality (n = 1). On follow-up, 3 cats eventually developed clinical signs of CE, of which 2 were euthanized 295 and 654 days post-endoscopy. The remaining 17 cats did not show clinical signs of CE after a median of 709 days (range, 219-869 days).Conclusions and clinical importanceIntestinal biopsy specimens from clinically healthy client-owned cats commonly had abnormal findings on histopathology, immunohistochemistry, clonality testing, or some combination of these without apparent clinical relevance. Current diagnostic metrics for diagnosing CE in cats may need modification to be applicable to the general population of cats

Chronic Inflammatory Enteropathy and Low-Grade Intestinal T-Cell Lymphoma Are Associated with Altered Microbial Tryptophan Catabolism in Cats.

Chronic inflammatory enteropathy (CIE) and low-grade intestinal T-cell lymphoma (LGITL) are common chronic enteropathies (CE) in cats. Enteric microbiota dysbiosis is implicated in the pathogenesis of CE; however, the mechanisms of host-microbiome interactions are poorly understood in cats. Microbial indole catabolites of tryptophan (MICT) are gut bacterial catabolites of tryptophan that are hypothesized to regulate intestinal inflammation and mucosal barrier function. MICTs are decreased in the sera of humans with inflammatory bowel disease and previous studies identified altered tryptophan metabolism in cats with CE. We sought to determine whether MICTs were decreased in cats with CE using archived serum samples from cats with CIE (n = 44) or LGITL (n = 31) and healthy controls (n = 26). Quantitative LC-MS/MS was used to measure serum concentrations of tryptophan, its endogenous catabolites (kynurenine, kynurenate, serotonin) and MICTs (indolepyruvate, indolealdehyde, indoleacrylate, indoleacetamide, indoleacetate, indolelactate, indolepropionate, tryptamine). Serum concentrations of tryptophan, indolepropionate, indoleacrylate, indolealdehyde, indolepyruvate, indolelactate were significantly decreased in the CIE and LGITL groups compared to those in healthy controls. Indolelactate concentrations were significantly lower in cats with LGITL compared to CIE (p = 0.006). Significant correlations were detected among serum MICTs and cobalamin, folate, fPLI, and fTLI. Our findings suggest that MICTs are promising biomarkers to investigate the role of gut bacteria in the pathobiology of chronic enteropathies in cats