UPLC-QTOF/MS Metabolomics and Biochemical Assays Reveal Changes in Hepatic Nutrition and Energy Metabolism during Sexual Maturation in Female Rainbow Trout (Oncorhynchus mykiss)

SIMPLE SUMMARY: Although the close relationship between nutrition mobilization and liver metabolism has been proposed in female rainbow trout with normal sexual maturity, detailed information concerning the molecular mechanisms that the liver regulates nutrition and energy metabolism to facilitate sexual maturity remains limited. In the present study, metabolomic and biochemical assays were used to investigate differences in liver metabolic characteristics between mature and immature female rainbow trout to systematically analyze the mechanisms of hepatic nutrients and energy metabolism during sexual maturation in female rainbow trout. Our results revealed that during the sexual maturation of female rainbow trout, the liver enhanced various pathways of lipid metabolism and amino acid anabolism to provide structural substances that promote the proliferation and differentiation of oocytes. At the same time, hepatic glycogen catabolism was the primary metabolic pathway for energy production. In conclusion, this study might give a deeper insight into understanding the “nutrition-reproduction” interaction of female rainbow trout at the metabolic level. ABSTRACT: Mobilization and repartition of nutrients and energy are prerequisites for the normal sexual maturity of broodstock. However, there are few studies on the mechanisms of hepatic nutrients and energy metabolism during sexual maturation in female rainbow trout (Oncorhynchus mykiss). This study investigated hepatic metabolite changes and explored the potential nutritional regulation mechanism between mature and immature female rainbow trout by combining UPLC-QTOF/MS metabolomics and biochemical assays. It was observed that hepatic biochemical assays differed considerably between the two groups, such as glucose, triglycerides, hexokinase, lipase, and aspartate aminotransferase. Liver metabolomics showed that various differential metabolites involved in amino acid and lipid metabolism markedly increased, suggesting the enhancement of lipid metabolism and amino acid anabolism in the liver provides the necessary material basis for ovarian development. Meanwhile, glycogen catabolism and glycolysis hold the key to maintaining organismal energy homeostasis with normal sexual maturation of female rainbow trout. Overall, the results from this study suggested that the liver undergoes drastic reprogramming of the metabolic profile in response to mobilization and repartition of nutrients and energy during the sexual maturation of female rainbow trout. This study further deepened the understanding of the reproductive biology of rainbow trout, and provided the theoretical basis and practical ramifications for nutritional requirements of breeding high-quality broodstock in the artificial propagation of rainbow trout.