Swine Inflammation and Necrosis Syndrome Is Associated with Plasma Metabolites and Liver Transcriptome in Affected Piglets

SIMPLE SUMMARY: Swine inflammation and necrosis syndrome (SINS) is a newly identified syndrome associated with inflammatory and necrotic signs in different body parts of suckling piglets, weaners, and fatteners. While the proven inflammatory basis of the disease and the development of signs in even newborns indicate a primarily endogenous etiology, the mechanisms underlying SINS development are largely unknown. In this study, the hypothesis was tested that SINS is indirectly triggered by the translocation of gut-derived microbial components into the liver, thereby causing derangements of liver metabolism, by comparing the hepatic transcriptome and plasma metabolome of SINS-affected and unaffected piglets. Apart from demonstrating that hepatic inflammation occurs in SINS-affected piglets, the study clearly shows for the first time that several metabolic derangements are induced in SINS-affected piglets that may contribute to the clinical and histopathological signs of SINS. ABSTRACT: Swine Inflammation and Necrosis Syndrome can lead to severe clinical signs, especially in tails, ears, teats, and claws in pigs. Clinical and histopathological findings in newborn piglets with intact epidermis indicate a primarily endogenous etiology, and microbial-associated molecular patterns (MAMPs), such as lipopolysaccharide (LPS) are assumed to play a central role in the development of the syndrome. We hypothesized that swine inflammation and necrosis syndrome (SINS) is indirectly triggered by gut-derived MAMPs entering the circulatory system via the liver and thereby causing derangements on liver metabolism. To test this hypothesis, metabolomes, candidate genes of the liver and liver transcriptomes of 6 piglets with high-grade clinical signs of SINS (SINS high) were examined and compared with 6 piglets without significant signs of SINS (SINS low). Several hepatic pro-inflammatory genes and genes involved in stress response were induced in piglets of the SINS high group. The most striking finding from hepatic transcript profiling and bioinformatic enrichment was that the most enriched biological processes associated with the approximately 220 genes induced in the liver of the SINS high group were exclusively related to metabolic pathways, such as fatty acid metabolic process. Within the genes (≈390) repressed in the liver of the SINS high group, enriched pathways were ribosome biogenesis, RNA processing, RNA splicing, spliceosome, and RNA transport. The transcriptomic findings were supported by the results of the metabolome analyses. These results provide the first evidence for the induction of an inflammatory process in the liver of piglets suffering from SINS, accompanied by lipid metabolic derangement.