Fecal Proteomic Analysis in Healthy Dogs and in Dogs Suffering from Food Responsive Diarrhea

Retrospective Study of 222 Dogs Suffering from Food-Responsive Enteropathy-Correlation with Clinical Variables, Diet and Breed

Food-responsive enteropathy (FRE) is the most frequent form of canine chronic inflammatory enteropathy (CIE). It can be diagnosed if, after excluding known causes of diarrhea, clinical signs resolve or significantly improve after an appropriate dietary trial. No universal diet can resolve the clinical signs in every case of FRE, as genetic predisposition and environment (e.g., the possible role of the diet feed before the disease onset) are suggested as possible players. The study aimed to retrospectively evaluate the possible correlations between disease, diet, and breed in a large cohort of dogs (n = 222) suffering from FRE. Throughout the study, dogs differed based on dietary options: commercial diet group, homemade diet group, and mixed diet group. Diet, breed, age, body weight, body condition score (BCS), fecal score (FS), canine chronic enteropathy activity index (CCECAI), and selected clinical signs were variably evaluated at T0 and at final time (FT-based on response to the diet[s], but between 30 and 60 days). Significant differences between T0 and FT were found regarding FS, BCS, and CCECAI, as well as between age, BCS, and CCECAI at FT with the FS at FT. The CCECAI at FT was significantly directly correlated only with the shift from a mixed to a homemade diet. Finally, the multiple linear regression analysis between the covariables of different breeds versus clinical response to the dietary trials did not highlight any difference except for the passage from commercial to mixed diet in a specific subgroup of breeds. The present study reports the clinical progression in 222 dogs suffering from FRE, and it could represent a reference for the variables investigated, considering the large number of patients included.

Characterization of the plasma proteome from healthy adult dogs

Introduction

Bloodwork is a widely used diagnostic tool in veterinary medicine, as diagnosis and therapeutic interventions often rely on blood biomarkers. However, biomarkers available in veterinary medicine often lack sensitivity or specificity. Mass spectrometry-based proteomics technology has been extensively used in the analysis of biological fluids. It offers excellent potential for a more comprehensive characterization of the plasma proteome in veterinary medicine.

Methods

In this study, we aimed to identify and quantify plasma proteins in a cohort of healthy dogs and compare two techniques for depleting high-abundance plasma proteins to enable the detection of lower-abundance proteins via label-free quantification liquid chromatography-mass spectrometry. We utilized surplus lithium-heparin plasma from 30 healthy dogs, subdivided into five groups of pooled plasma from 6 randomly selected individuals each. Firstly, we used a commercial kit to deplete high-abundance plasma proteins. Secondly, we employed an in-house method to remove albumin using Blue-Sepharose.

Results and discussion

Among all the samples, some of the most abundant proteins identified were apolipoprotein A and B, albumin, alpha-2-macroglobulin, fibrinogen beta chain, fibronectin, complement C3, serotransferrin, and coagulation factor V. However, neither of the depletion techniques achieved significant depletion of highly abundant proteins. Despite this limitation, we could detect and quantify many clinically relevant proteins. Determining the healthy canine proteome is a crucial first step in establishing a reference proteome for canine plasma. After enrichment, this reference proteome can later be utilized to identify protein markers associated with different diseases, thereby contributing to the diagnosis and prognosis of various pathologies.

Fecal Proteome Profile in Dogs Suffering from Different Hepatobiliary Disorders and Comparison with Controls

In the present study, the fecal proteomes of clinically healthy dogs (HD = n. 10), of dogs showing clinical, ultrasonographic, and/or laboratory evidence of different hepatobiliary dysfunction (DHD = n. 10), and of dogs suffering from chronic hepatitis (CHD = n. 10) were investigated with an Ultimate 3000 nanoUPLC system, coupled to an Orbitrap Fusion Lumos Tribrid mass spectrometer. Fifty-two different proteins of canine origin were identified qualitatively in the three study groups, and quantitative differences were found in 55 proteins when comparing groups. Quantitatively, a total of 41 and 36 proteins were found differentially abundant in the DHD and CHD groups compared to the control HD, and 38 proteins resulted dysregulated in the CHD group as compared to the DHD group. Among the various proteins, differently abundant fecal fibronectin and haptoglobin were more present in the feces of healthy and DHD dogs than in chronic ones, leading us to hypothesize its possible diagnostic/monitoring role in canine chronic hepatitis. On the other hand, the trefoil factor 2 was increased in DHD dogs. Our results show that the analysis of the fecal proteome is a very promising field of study, and in the case of dogs suffering from different hepatobiliary disorders, it was able to highlight both qualitative and quantitative differences among the three groups included. Results need to be confirmed with western blotting and in further studies.

Serum proteome of dogs with chronic enteropathy

BACKGROUND

Chronic enteropathy (CE) is common in dogs and can occur with multiple etiologies including food-responsive enteropathy (FRE) and idiopathic inflammatory bowel disease (IBD).

HYPOTHESIS/OBJECTIVE

To study the protein profile and pathway differences among dogs with FRE, IBD, and healthy controls using serum proteome analysis.

ANIMALS

Nine CE dogs with signs of gastrointestinal disease and histologically confirmed chronic inflammatory enteropathy and 16 healthy controls.

METHODS

A cross-sectional study with cases recruited from 2 veterinary hospitals between May 2019 and November 2020 was performed. Serum samples were analyzed using mass spectrometry-based proteomic techniques.

RESULTS

Proteomic profiles showed marked variation in relative protein abundances. Forty-five proteins were significantly (P ≤ .01) differentially expressed among the dogs with CE and controls with ≥2-fold change in abundance. The fold change of dogs with IBD normalized to controls was more pronounced for the majority of proteins than that seen in the dogs with FRE normalized to control dogs. Proteins involving reactive oxygen species, cytokine activation, acute phase response signaling, and lipid metabolism were altered in dogs with CE.

CONCLUSIONS AND CLINICAL IMPORTANCE

Cytokine alterations, acute phase response signaling, and lipid metabolism are likely involved in pathogenesis of CE. Although there are insufficient current data to justify the use of proteomic biomarkers for assessment of CE in dogs, our study identifies potential candidates.

Fecal Protein Profile in Eight Dogs Suffering from Acute Uncomplicated Diarrhea before and after Treatment

Acute diarrhea is a very frequent condition affecting dogs; nevertheless, little is known about what happens in the GI tract during such conditions. Proteomics allows the study of proteins present in a specific biologic substrate, and fecal proteomic investigations have been recently implemented to study GI diseases in dogs. In the present study, the fecal protein profiles of eight dogs suffering from acute uncomplicated diarrhea at the time of inclusion was investigated for the first time, and then the same patients were followed, replicating two further evaluations at two subsequent time points (after 2 and 14 days from the first presentation), with the aim of gaining possible new insights regarding the pathologic changes in the gastrointestinal environment during such conditions. Two-dimensional gel electrophoresis (2-DE) was performed, followed by mass spectrometry. Nine spots, corresponding to four (groups of) proteins (i.e., albumin, alkaline phosphatase, chymotrypsin-C-like, and some immunoglobulins), showed significant differences at two or more of the three time points investigated, almost all behaving similarly and decreasing at T1 (2 days after the onset of the condition) and significantly increasing at T2 (14 days after the onset), mainly evidencing a reaction of the organism. Further studies including a greater number of patients and possibly different techniques are needed to confirm the present findings.

Evaluation of the Fecal Proteome in Healthy and Diseased Cheetahs (Acinonyx jubatus) Suffering from Gastrointestinal Disorders

Fecal proteomics allows for the identification of proteins and peptides present in stools and is useful in finding possible new biomarkers for diagnosing and/or monitoring gastrointestinal (GI) disorders. In the present study, we investigated the fecal proteome in healthy and diseased cheetahs (Acinonyx jubatus). Captive individuals of this species frequently show gastrointestinal disorders characterized by recurrent episodes of diarrhea, rare episodes of vomiting and weight loss, associated with Helicobacter spp. infection. Fecal proteomic evaluation has been performed by two-dimensional electrophoresis followed by liquid chromatography-tandem mass spectrometry. In healthy cheetahs, the results showed the presence of the following proteins: collagen alpha-1 (II) chain, transthyretin, IgG Fc-binding protein, titin, dystonin, isopentenyl-diphosphate Delta-isomerase 1, sodium/potassium-transporting ATPase subunit alpha-1 and protein disulfide-isomerase A6. The presence of albumin isoforms was found only in diseased cheetahs. The present paper reports the study of the fecal proteome in the cheetah, evidences some differences between healthy and diseased patients and confirms, once again, the potential of fecal proteomics for the study of the GI environment, with promising developments regarding the identification of new diagnostic/monitoring markers.

Faecal proteomics in the identification of biomarkers to differentiate canine chronic enteropathies

Canine chronic enteropathy (CCE) is a collective term used to describe a group of idiopathic enteropathies of dogs that result in a variety of clinical manifestations of intestinal dysfunction. Clinical stratification into food-responsive enteropathy (FRE) or non-food responsive chronic inflammatory enteropathy (CIE), is made retrospectively based on response to treatments. Faecal extracts from those with a FRE (n = 5) and those with non-food responsive chronic inflammatory enteropathies (CIE) (n = 6) were compared to a healthy control group (n = 14) by applying TMT-based quantitative proteomic approach. Many of the proteins with significant differential abundance between groups were pancreatic or intestinal enzymes with pancreatitis-associated protein (identified as REG3α) and pancreatic M14 metallocarboxypeptidase proteins carboxypeptidase A1 and B identified as being of significantly increased abundance in the CCE group. The reactome analysis revealed the recycling of bile acids and salts and their metabolism to be present in the FRE group, suggesting a possible dysbiotic aetiology. Several acute phase proteins were significantly more abundant in the CCE group with the significant increase in haptoglobin in the CIE group especially notable. Further research of these proteins is needed to fully assess their clinical utility as faecal biomarkers for differentiating CCE cases. SIGNIFICANCE: The identification and characterisation of biomarkers that differentiate FRE from other forms of CIE would prove invaluable in streamlining clinical decision-making and would avoid costly and invasive investigations and delays in implementing effective treatment. Many of the proteins described here, as canine faecal proteins for the first time, have been highlighted in previous human and murine inflammatory bowl disease (IBD) studies initiating a new chapter in canine faecal biomarker research, where early and non-invasive biomarkers for early clinical stratification of CCE cases are needed. Pancreatitis-associated protein, pancreatic M14 metallocarboxypeptidase along with carboxypeptidase A1 and B are identified as being of significantly increased abundance in the CCE groups. Several acute phase proteins, were significantly more abundant in the CCE group notably haptoglobin in dogs with inflammatory enteropathy. The recognition of altered bile acid metabolism in the reactome analysis in the FRE group is significant in CCE which is a complex condition incorporating of immunological, dysbiotic and faecal bile acid dysmetabolism. Both proteomics and immunoassays will enable the characterisation of faecal APPs as well as other inflammatory and immune mediators, and the utilisation of assays, validated for use in analysis of faeces of veterinary species will enable clinical utilisation of faecal matrix to be fully realised.

Faecal proteome in clinically healthy dogs and cats: Findings in pooled faeces from 10 cats and 10 dogs

BACKGROUND

In the scientific literature, there are only a few manuscripts available on small animal faecal proteomics.

METHODS

In the present pilot study, this evaluation was performed using pooled faecal samples from 10 clinically healthy dogs and, for the first time, in 10 clinically healthy cats by mean of two-dimensional electrophoresis followed by liquid chromatography-tandem mass spectrometry.

RESULTS

Our results showed the presence of nine (albumin, alkaline phosphatase, chymotrypsin-C-like, cytosol aminopeptidase, elastase-3B/proteinase E, immunoglobulins and nuclear pore membrane glycoprotein 210) and 14 (albumin, caspase recruitment domain-containing protein, chymotrypsin-like, deleted in malignant brain tumours 1 protein-like, hypothetical protein LOC107375, immunoglobulin, kallikrein-1, superoxide dismutase, transthyretin precursor, interstitial collagenase-like) different proteins in canine and feline faeces, respectively.

CONCLUSION

These preliminary findings document the presence of a range of proteins in the faeces of apparently healthy dogs and cats and may serve as a basis for larger, prospective studies to establish reference proteomic data against which diseased populations can be compared.

Clinicopathological and Fecal Proteome Evaluations in 16 Dogs Presenting Chronic Diarrhea Associated with Lymphangiectasia

Canine intestinal lymphangiectasia (IL) is a condition characterized by variably severe gastrointestinal signs, frequently associated with laboratory abnormalities; the research for markers allowing a better understanding of the severity degree and/or obtaining an early diagnosis and/or monitoring is continuously progressing. In the present study, we investigated possible new diagnostic/follow-up markers in IL dogs, namely, serum C-reactive protein, serum bacterial lipopolysaccharide, serum cleaved cytokeratin 18, serum citrulline, and zonulin (in both serum and feces). A fecal proteomic study looking for possible confirmation and/or new marker candidates was also performed. All markers in both substrates, with the exception of serum citrulline, significantly differed between diseased and control dogs. Fecal proteomics allowed the retrieval of three proteins in IL dogs (Fc fragment of IgG-binding protein; transthyretin; proproteinase E) that were not previously found in clinically healthy subjects. Although further studies are needed, C-reactive protein, bacterial lipopolysaccharide, cleaved cytokeratin 18, and zonulin (in both serum and feces) resulted as promising markers for canine IL; similarly, fecal proteomics represents a road worthy of being pursued in the search for candidate biomarkers.

Canine Traditional Laboratory Tests and Cardiac Biomarkers

In small animals, cardiac disease evaluation through laboratory tests can be a challenge. This review will present both historical and updated perspectives on the clinical pathology of cardiac diseases in dogs and demonstrate that laboratory tests are useful tools for the management of patients with cardiac diseases.

Rapid Resolution of Large Bowel Diarrhea after the Administration of a Combination of a High-Fiber Diet and a Probiotic Mixture in 30 Dogs

Canine fiber responsive diarrhea is a form of chronic colitis that improves clinically after adding fiber to the diet. In the present study, we investigated the effect of a combination of a high-fiber, highly digestible, hypoallergenic diet with a probiotic mixture in 30 dogs with chronic colitis that were unresponsive to various dietary and/or pharmacological interventions. Fecal scores, canine chronic enteropathy clinical activity index (CCECAI) scores, the dysbiosis index (DI), and histologic images of colonic biopsies were evaluated. At baseline (day 0; T0) and after 30 days of treatment (T1), all variables evaluated in our patients (i.e., fecal and CCECAI scores and histopathology) improved significantly at T1, with the exception of DI. However, there was a numerical shift from a state of dysbiosis to one of normobiosis. The combination of the diet and the probiotic used in the present study induced the resolution of clinical signs in a mean of 8.5 days (maximum 15 days) and did not necessitate any other treatments or the further addition of alimentary fiber.