Markers of Gut Health in Small Animals: Focus on Fatty Acids and Amino Acids as Indicators of Intestinal Functionality and Microbiome Activity.

Chronic inflammatory enteropathies (CIEs) in companion animals represent a group of idiopathic, immune-mediated gastrointestinal disorders in which the intestinal epithelium can be altered, affecting intestinal functionality, nutrient absorption, and microbiota composition. This review presents an overview of markers that could be used for the assessment of intestinal health, focusing extensively on functional biomarkers, with particular attention to fatty acids (including short-chain fatty acids, SCFAs) and amino acids. Studies have consistently shown reduced concentrations of SCFAs in companion animals with CIEs compared to healthy groups. These alterations occur with varying intensity depending on the type of enteropathy. Alterations in saturated, monounsaturated, and long-chain polyunsaturated fatty acids have also been reported in blood and feces, particularly in omega-3 and omega-6 derivatives, as well as in the elongase and desaturase indices responsible for endogenous synthesis. In addition, amino acids serve as precursors to key metabolites involved in mucosal immunity, oxidative stress regulation, and microbial homeostasis. In CIEs, alterations in systemic and fecal amino acid profiles have been observed, reflecting both host metabolic adaptation and microbial dysbiosis. Integrating fatty acid and amino acid profiles can help distinguish different types of enteropathies, providing additional discriminatory power for determining response to dietary treatment. Future research should aim to elucidate the causal relationships between metabolic alterations and disease pathogenesis, which could lead to novel dietary interventions targeting metabolic interactions between the microbiota and the host.