Canine Intestinal Organoids as a Novel In Vitro Model of Intestinal Drug Permeability: A Proof-of-Concept Study

A key component of efforts to identify the biological and drug-specific aspects contributing to therapeutic failure or unexpected exposure-associated toxicity is the study of drug-intestinal barrier interactions. While methods supporting such assessments are widely described for human therapeutics, relatively little information is available for similar evaluations in support of veterinary pharmaceuticals. There is, therefore, a critical need to develop novel approaches for evaluating drug-gut interactions in veterinary medicine. Three-dimensional (3D) organoids can address these difficulties in a reasonably affordable system that circumvents the need for more invasive in vivo assays in live animals. However, a first step in developing such systems is understanding organoid interactions in a 2D monolayer. Given the importance of orally administered medications for meeting the therapeutic need of companion animals, we demonstrate growth conditions under which canine-colonoid-derived intestinal epithelial cells survive, mature, and differentiate into confluent cell systems with high monolayer integrity. We further examine the applicability of this canine-colonoid-derived 2D model to assess the permeability of three structurally diverse, passively absorbed β-blockers (e.g., propranolol, metoprolol, and atenolol). Both the absorptive and secretive apparent permeability (P_app) of these drugs at two different pH conditions were evaluated in canine-colonoid-derived monolayers and compared with that of Caco-2 cells. This proof-of-concept study provides promising preliminary results with regard to the utility of canine-derived organoid monolayers for species-specific assessments of therapeutic drug passive permeability.

Dose-response of benazepril on biomarkers of the classical and alternative pathways of the renin-angiotensin-aldosterone system in dogs

Angiotensin-converting enzyme inhibitors (ACEI) such as benazepril are commonly prescribed in both humans and dogs with heart disease to mitigate the renin-angiotensin-aldosterone system (RAAS); however, the dose-dependent effects of benazepril on comprehensive RAAS components remain unknown. In this study, nine purpose-bred healthy dogs received three different dosages of oral benazepril (0.125 mg/kg, 0.25 mg/kg, or 0.5 mg/kg) in a randomized crossover design following induction of RAAS activation by consuming a low-sodium diet. Blood samples were collected at serial time intervals after benazepril dosing to measure plasma benazeprilat (active metabolite of benazepril) and serum RAAS biomarkers. Blood pressure and echocardiogram were performed at baseline and after each benazepril administration. Time-weighted averages for RAAS biomarkers for 12 h post-dose and hemodynamic variables were compared between dosing groups using Wilcoxon rank-sum testing. Compared to the lowest dosage of benazepril (0.125 mg/kg), the highest dosage (0.5 mg/kg) resulted in lower time-weighted average values of angiotensin (Ang) II (- 38%, P = 0.004), Ang1-5 (- 53%, P = 0.001), ACE-S (surrogate for ACE activity; - 59%, P = 0.0002), and ALT-S (surrogate for alternative RAAS activity; - 22%, P = 0.004), and higher values of AngI (+ 78%, P = 0.014) and PRA-S (surrogate for plasma renin activity; + 58%, P = 0.040). There were no relevant differences between dosing groups for blood pressure or echocardiographic variables. Knowledge of dose-dependent alterations in biomarkers of the classical and alternative RAAS pathways could help inform clinical trials for dosage optimization in both dogs and humans.

Synbiotic-IgY Therapy Modulates the Mucosal Microbiome and Inflammatory Indices in Dogs with Chronic Inflammatory Enteropathy: A Randomized, Double-Blind, Placebo-Controlled Study

Chronic inflammatory enteropathy (CE) is a common cause of persistent gastrointestinal signs and intestinal inflammation in dogs. Since evidence links dysbiosis to mucosal inflammation, probiotics, prebiotics, or their combination (synbiotics) may reduce intestinal inflammation and ameliorate dysbiosis in affected dogs. This study's aim was to investigate the effects of the synbiotic-IgY supplement on clinical signs, inflammatory indices, and mucosal microbiota in dogs with CE. Dogs with CE were enrolled in a randomized prospective trial. Twenty-four client-owned dogs were fed a hydrolyzed diet and administered supplement or placebo (diet) for 6 weeks. Dogs were evaluated at diagnosis and 2- and 6-week post-treatment. Outcome measures included clinical activity, endoscopic and histologic scores, inflammatory markers (fecal calprotectin, C-reactive protein), and composition of the mucosal microbiota via FISH. Eleven supplement- and nine placebo-treated dogs completed the trial. After 6 weeks of therapy, clinical activity and endoscopic scores decreased in both groups. Compared to placebo-treated dogs, dogs administered supplement showed decreased calprotectin at 2-week post-treatment, decreased CRP at 2- and 6-week post-treatment increased mucosal Clostridia and Bacteroides and decreased Enterobacteriaceae in colonic biopsies at trial completion. Results suggest a beneficial effect of diet and supplements on host responses and mucosal microbiota in dogs with CE.

109 Diet-induced Clinical Responsiveness of Translational Dog Model for Human Western Diet (WD)-related Disease Research

Human consumption of Western diets (WD) has been strongly associated with increased central obesity, adipocyte hypertrophy, intestinal epithelial stemness/proliferation, dyslipidemia, and blood pressure. These changes reflect metabolic dysfunction and contribute to increased risk of type 2 diabetes mellitus and colorectal cancer. As comprehensive molecular/clinical comparisons have not been performed, the objective of this study was to evaluate diet-induced changes in dogs as a clinically-responsive model for human WD-related disease research. Methods: In a crossover design, 10 dogs were fed either a 1.) control diet (CON) formulated based on the Acceptable Macronutrient Distribution Ranges and fiber recommendations for humans; or 2.) Western diet (WD) formulated based on National Health and Nutrition Examination Survey dataset parameters. Diets were prepared cooked with the same ingredients and formulated to meet/exceed nutrient/energy requirements for both humans/dogs and fed isocalorically based on calculated metabolizable energy (ME). Following each period (~7–8 weeks), experimental parameters were measured. Results/Conclusions: Mean body weights were 8.83 and 9.28kg for CON and WD diets, respectively (P = 0.0018). Fasted (10-hour) blood samples differed significantly (P < 0.01) for mean fasting bile acids (CON=0.79, WD=8.94μmol/L), serum triglycerides (CON=45.70, WD=67.80mg/dL), and serum cholesterol (CON=140.10, WD=175.40mg/dL) demonstrating diet-dependent alterations in lipid profiles. Mean systolic blood pressures were 131.66 and 140.02mmHg for CON and WD, respectively (P < 0.0001). Histological analysis revealed diet-dependent changes in colonic epithelial villus height (CON=182, WD=207μm) and villus:crypt ratio (CON=2.61, WD=3.89). Preliminary RNA-ISH analysis (n = 3 dogs) showed increased LGR5+ expression (intestinal stem-cell marker) in WD compared to CON group (P = 0.0019) suggesting an increased “stemnness” of colonic epithelium. Further, mean adipocyte diameters were increased in omental fat biopsies (CON=58.6, WD=62.5μm; P < 0.0001) but not subcutaneous fat biopsies (P >0.05) following WD feeding, consistent with centralized obesity. Collectively, these results demonstrate effects of diet-induced changes in dogs as a clinically-responsive model for human WD-related disease research.