Metabolomics-based analysis of adaptive mechanism of Larimichthys crocea to low temperature and starvation stresses

Large yellow croaker (Larimichthys crocea) is the most important warm-water marine commercial fish, which is widely distributed in the southeast coastal regions in China, such as Zhejiang, Fujian and Guangdong provinces. It is highly sensitive to cold and starvation, and massive death of this species can be observed during winters, leading to significant economic losses for farmers. This study aims to explore the response mechanism of L. crocea to oxidative damage caused by low temperature and starvation. Fish with an average weight of (21.38±2.46) g were exposed to low temperature (8 °C) or/and under starvation stress. The fish were divided into four groups: control group (C group), cold group (CC group), fasting group (F group) and cold+fasting group (CF group), each with three replicates. The experiment lasted 30 d, survival rate was calculated, liver samples were obtained for histological observation, chemical fluorescence and LC-MS technology were used to analyze the difference of reactive oxygen species (ROS) and metabolites in different treatment groups. The results showed that compared with C group, the survival rate of CC group, F group and CF group was significantly decreased, while the ROS content was significantly increased (P<0.05), and demonstrated vacuolation and nuclear atrophy, indicating cold and starvation stresses induced oxidative damage. A total of 184 and 50 differential metabolites were obtained from CC vs. C and CF vs. F, respectively. There were five important co-metabolic pathways: glycerophospholipid metabolism, glycosylphosphatidylinositol (GPI) - anchor biosynthesis, arginine biosynthesis, sphingolipids metabolism and autophagy, indicating cell membrane fluidity and autophagy played an important role in cold adaptation. A total of 184 and 50 different metabolites were obtained from F vs. C and CF vs. CC, respectively. There were four important overlapping metabolic pathways: glycerophospholipid metabolism, glycosylphosphatidylinositol (GPI) - anchor biosynthesis, ABC transporters and autophagy, indicating energy and material transport function, as well as autophagy played an important role in starvation stress of L. crocea. 126 differential metabolites were obtained from CF vs. C, which were significantly enriched in glycosylphosphatidylinositol (GPI) - anchor biosynthesis, glycerophospholipid metabolism, oxidative phosphorylation, starch and sucrose metabolism, FoxO signal pathway, autophagy and glutathione metabolism, indicating cell membrane fluidity, energy metabolism, autophagy and antioxidant systems played an important role in cold and starvation adaptation. The results provide scientific basis for further study about the effects of low temperature and fasting on the physiological functions of L. crocea.