Investigation of fecal microbiome and metabolome perturbations in dogs with protein-losing enteropathy

Canine protein-losing enteropathy (PLE) is a severe gastrointestinal syndrome characterized gastrointestinal loss of proteins. While dysbiosis and fecal metabolome perturbations have been previously reported in dogs with chronic enteropathy, they have not been widely studied in dogs with PLE, and the effects of treatment are unknown. Characterization of microbiome and metabolome perturbations could improve the management of PLE. Therefore, the study aims were (i) to investigate gut microbiome and targeted fecal metabolites in dogs with PLE and (ii) evaluate whether treatment affects these changes at short-term follow-up. Fifty-eight dogs with a diagnosis of PLE and histopathological evidence of gastrointestinal inflammation were prospectively enrolled, and 50 healthy dogs were included as a control group in this observational study. Non-gastrointestinal causes of hypoalbuminemia, defined by a serum albumin ≤2.8 g/dl, were ruled out prior to enrollment. Fecal samples were collected before endoscopy (T0) and after one month of therapy (T1). Microbiome alterations were investigated using qPCR assays for determination of the dysbiosis index (DI). Metabolome alterations were investigated using gas chromatography coupled with mass spectrometry for the determination of fecal sterols and fatty acids (FAs). Median (min-max) canine chronic enteropathy clinical activity index (CCECAI) and serum albumin at T0 were 9 (3-17) and 1.8g/dL (0.8-2.8) in dogs with PLE and had improved at T1 with median (min-max) values of 5 (0-13) and 2.3 g/dL (1.2-3.2), respectively. Median (min-max) DI of PLE dogs was -0.4 (-5.9-8.3) and was significantly higher (p<0.0001) than median DI in healthy dogs that was -2.0 (-6.0-5.3). No significant associations were found between DI and CCECAI, and serum albumin, cobalamin, cholesterol or C-Reactive Protein. DI did not significantly differ between T0 and T1. In PLE dogs, among FAs measured at T0, myristate, palmitate, linoleate, oleate, cis-vaccenate, stearate, arachidonate, gondoate, docosanoate, erucate, and nervonate, were significantly increased (adjusted p<0.001); arachidonate (adjusted p=0.024) was significantly decreased at T1 compared to T0. At T0, among zoosterols measured, cholesterol (adjusted p=0.0012) was significantly increased in PLE dogs and significantly decreased (adjusted p=0.046) at T1 compared to T0. Total measured phytosterols were significantly decreased in PLE dogs at T0, and significantly increased at T1 (both adjusted p=0.0012). Among measured phytosterols at T0, beta-sitosterol, sitostanol, fusosterol, campesterol, and lathosterol were significantly decreased (all adjusted p<0.05) in PLE dogs. This observational study shows that microbiome and lipid metabolism perturbations occurred in dogs with PLE. These alterations partially recovered after treatment.