Preliminary analysis of intestinal microbiota in Golden Retrievers prone to taurine deficiency.

Introduction: Recent literature has highlighted the significance of taurine in the pathogenesis of dilated cardiomyopathy in Golden Retrievers [1,2]. Taurine is a conditional essential amino acid in dogs and needs meticulous dietary management to ensure adequate intake, particularly in this breed [3]. Notably, gut microbiota profoundly influences taurine metabolism, with select bacterial species utilizing taurine as a metabolic substrate [4]. Moreover, intestinal hydrolases, crucial for taurine deconjugation from bile acids, are predominantly of microbial origin [5]. Hence, this study aimed to scrutinize the intestinal microbiota composition in Golden Retrievers and assess potential alterations in subjects exhibiting hypotaurinemia. Animals, materials and methods. Eleven healthy Golden Retrievers, fed the same commercial diet, underwent evaluation in this study. Nutritional assessment encompassing body weight, body condition score (BCS), and muscle condition score (MCS) was conducted during the examination. Blood samples were obtained to measure serum taurine concentrations, while faecal samples underwent 16S rRNA gene sequencing analysis. Descriptive statistical analysis employing SPSS was used for data interpretation. Sequencing reads were filtered and analysed using QIIME2, followed by normalization of counts prior to alpha and beta diversity analysis utilizing GMPR. Alpha and beta diversity indexes analyses were performed in R where Wilcoxon test was employed to assess alpha diversity differences between groups. Differential abundance analysis between high and low serum taurine groups was performed using ANCOMBC. Results and discussion: The mean body weight recorded was 26.5 ± 3.95 kg. Notably, 73% of the dogs exhibited overweight (BCS 6/9), while 9% were obese (BCS 7/9), consistent with a breed predisposition to obesity [6]. MCS was considered adequate in all subjects. Microbiota analysis among all 11 individuals revealed Bacteroidetes (26,51 ± 8,10%), Fusobacteriaceae (16,74 ± 4,15%), Algalicenaceae (7,14 ± 2,44%) and Paraprevotellaceae (6,34 ± 2,75%) as predominant phyla. Serum taurine concentration fell below the normal range (110-272 nmol/mL) in 73% of the samples, as per literature reference values [7]. Consequently, subjects were categorized into high (>110 nmol/mL) and low (<110 nmol/mL) serum taurine groups. Moreover, both alpha (inclusive of observed species, Pielou, and Shannon index) and beta (evaluated via Bray-Curtis index) diversity showed no statistically significant differences between the high and low taurine groups. Noteworthy taxonomic variations in hypotaurinemic dogs included a decrease in Coriobacteriaceae family abundance and an increase in unidentified species within the Bacteroidetes family and Epulopiscium genus, suspected of possessing 7α- hydroxysteroid dehydrogenase (HSDH) [8], bile salt hydrolase (BSH) [6] and fatty acid binding capabilities [9], implicating their involvement in taurine metabolism. Conclusion Alterations in microbiota composition observed in the low taurine group may be involved in taurine deficiency. However, faecal losses due to inadequate deconjugation and reabsorption or microbial consumption may have contributed to the low blood taurine concentration. Further investigations on a larger caseload are warranted to elucidate gut microbiota alterations and serum taurine concentrations, mirroring results obtained in human medical research.