# Multi-Omics Analysis Provides Insights into the Key Regulatory Pathways of Energy Metabolism in GIFT Under Salinity Stress

## TL;DR

This study explores how tilapia adjust their energy metabolism to survive in salty water, offering insights for breeding salt-tolerant fish.

## Contribution

The study reveals how tilapia reprogram energy metabolism under salinity stress using multi-omics data, identifying actionable targets for breeding.

## Key findings

- Salinity stress suppresses growth and induces extensive transcriptomic and metabolic changes in tilapia liver.
- Energy is redirected by suppressing fatty acid synthesis and steroid biosynthesis, with Fasn down-regulated.
- Metabolic reprogramming involves energy-sensing networks and glycolysis/gluconeogenesis pathway adjustments.

## Abstract

Salinity stress poses a major challenge to tilapia farming, particularly as the industry increasingly explores the use of brackish water. This study aimed to investigate the internal response mechanisms of genetically improved farmed tilapia (GIFT) when transferred from freshwater to saline environments. By analyzing changes in genes and small molecules in the fish liver, we found that high-salinity conditions slow fish growth. In response, the fish significantly alter their energy utilization strategies: they actively reduce energy expenditure on the synthesis of fats and steroid hormones and adjust sugar metabolism, thereby redirecting energy toward the critical and energy-intensive task of maintaining internal salt-water balance. These findings reveal the molecular strategies tilapia employ to cope with salt stress. This research provides insights for breeding new tilapia varieties with enhanced salt tolerance, contributing to more sustainable and productive aquaculture across a wider range of aquatic environments.

Salinity stress represents a critical environmental constraint that significantly limits the development of tilapia aquaculture in brackish water environments. Its substantial impacts on fundamental physiological processes in fish, particularly osmotic balance, energy metabolism, and antioxidant defense mechanisms, have become a major scientific concern in aquaculture research. To systematically elucidate the molecular mechanisms underlying the response of genetically improved farmed tilapia (Oreochromis niloticus) to salinity stress and to test the hypothesis that it adapts through metabolic reprogramming for energy reallocation under such conditions, this study employed an integrated transcriptomic and metabolomic approach. Through a rigorously controlled experimental design with freshwater (0‰) as the control group and brackish water (24‰) as the experimental group, we conducted a comprehensive analysis of dynamic changes in gene expression profiles and metabolite spectra in the liver tissues of experimental fish. The study yielded the following key findings: First, salinity stress significantly suppressed growth performance indicators, including body weight and length, while simultaneously inducing extensive transcriptomic restructuring and profound metabolic remodeling in liver tissue. A total of 1529 differentially expressed genes (including 399 up-regulated and 1130 down-regulated genes) and 127 significantly differential metabolites were identified. Second, the organism achieved strategic reallocation of energy resources through coordinated suppression of multiple energy-consuming anabolic pathways, particularly steroid biosynthesis and fatty acid metabolism, with the remarkable down-regulation of Fasn, a key gene in the fatty acid synthesis pathway, being especially prominent. Energy-sensing and metabolic homeostasis regulatory networks played a central coordinating role in this process, guiding the organism through metabolic reprogramming by regulating downstream metabolic nodes. From a multi-omics integrative perspective, this study provides in-depth insights into the sophisticated metabolic remodeling and energy allocation strategies employed by GIFT to cope with salinity stress. These findings, particularly the suppression of fatty acid biosynthesis and the reprogramming of glycolysis/gluconeogenesis pathways, not only elucidate the molecular mechanisms by which teleosts achieve environmental adaptation through energy reallocation, but also provide actionable molecular targets for the selective breeding of salinity-resilient tilapia strains.