Dietary myo-inositol exerts pleiotropic effects on T cell activation, antioxidant defense and fatty acid metabolism to enhance anti-bacterial immunity in tilapia.

Abstract

Bacterial diseases cause major economic losses in aquaculture, underscoring the need for feed additives that enhance fish immunity. Myo-inositol (MI), an essential nutrient for fish growth, possesses antioxidant and lipid-metabolism modulating properties. However, the role of MI in regulating T cell function remains unclear. In this study, Nile tilapia (Oreochromis niloticus) individuals were fed diets containing 850 or 1700 mg/kg MI to evaluate its effects on T cell immunity. The results demonstrated that dietary MI at 850 mg/kg significantly enhanced host anti-bacterial immunity in Nile tilapia by systematically improving T cell function. Specifically, during Edwardsiella piscicida infection, dietary MI increased the absolute number of T cells in Nile tilapia, and promoted their activation, proliferation, and cytokine production while reducing apoptosis. Mechanistically, MI elevated antioxidant enzymes expression to reduce intracellular reactive oxygen species (ROS) in T cells and drove fatty acid metabolic reprogramming. These coordinated enhancements collectively accelerated pathogen clearance and significantly improved host survival upon E. piscicida infection. Therefore, these findings reveal the pivotal role of dietary MI in promoting T cell mediated anti-bacterial immunity in Nile tilapia, and establish a foundation for using nutritional immunomodulation to improve health and disease resistance in farmed fish.