Exposure to lipopolysaccharide induces immune genes in cultured preadipocytes of Atlantic salmon

In addition to its central role of energy storage and release, white adipose tissue (WAT) performs complex endocrine and immune activities. WAT produces physiologically active secretory proteins, including cytokines and complement factors. Furthermore, treatment of mammalian adipocytes with cytokines and inflammatory stimulators induces immune genes, suppresses regulators of adipocyte differentiation and activates lipolysis. Previously we reported up-regulation of immune genes in the course of in vitro development of Atlantic salmon white adipocytes. If WAT is immunoactive tissue in fish, excessive deposition of fat resulting from lipid-rich diets may imply risk for health of farmed fish. In this paper we investigated how lipopolysaccharide (LPS) affects immune activity in the adipose tissue-derived stromo-vascular fraction (aSVF) of Atlantic salmon. Experiments were performed with confluent cultures of proliferating preadipocytes. Exposure to LPS induced expression of immune genes, including TNFα and TNF-dependent genes, chemokines and receptors, NFkappaB related genes, matrix metalloproteinases and genes involved in eicosanoid metabolism. LPS decreased expression of adipocyte markers and genes involved in lipid metabolism, however, in parallel, it accelerated a number of transcriptional events that take place during the adipogenic differentiation of aSVF.