Dietary creatine enhances neurodevelopment and cognitive performance in juvenile largemouth bass (Micropterus salmoides): Implications for aquaculture efficiency and conservation strategies

Creatine contributes to cognition and brain health in mammalian. Neuronal regeneration in the teleost brain shows great potential throughout the life cycle, dietary creatine may be of potential value in aquatic animal brains. Therefore, in this study, 6 feeds with different creatine additions (0 %, 0.2 %, 0.5 %, 1 %, 2 %, and 4 %) were formulated and fed to juvenile largemouth bass (Micropterus salmoides) for 8 weeks. The brain creatine metabolism of largemouth bass was detected by Q-PCR, Western blot, and high-performance liquid chromatography (HPLC). Dietary creatine significantly increased creatine inventory, mRNA levels of brain-type creatine kinase, protein level of creatine transporter protein (SLC6A8) in the brain of largemouth bass. This indicated that exogenous creatine can effectively pass through the blood-brain barrier of largemouth bass and deposited in the brain. Western blot for relative quantification of protein levels, it was found in this study that creatine could elevate the protein levels of BDNF (Brain Derived Neurotrophic Factor) as well as phosphorylated activation of the AKT (Protein Kinase B) /mTOR (Mechanistic Target of Rapamycin Kinase) and the ERK (Extracellular Signal-Regulated Kinase)/p90RSK (90 KDa Ribosomal Protein S6 Kinase) in the largemouth bass brain to activate brain neurotrophin signaling pathways. Teleost can consistently produce new neurons in the adult brain. In this study, dietary creatine significantly upregulated neuro-related growth factors genes, indicating that dietary creatine promotes neurodevelopment and neurogenesis in the brain. In the present study, multiple experimental setups were used to assess fish behavior. Dietary creatine significantly increased the forward maximum acceleration of largemouth bass in open-field test; significantly increased the exploration time in new object recognition test (NORT); and significantly increased the mean swimming speed and forward maximum acceleration of largemouth bass in sociability test. In locomotor (swimming) capacity tests, the burst swimming speed after rest was significantly elevated, which possibly resulting in enhanced predation ability. Overall, these findings suggest that long-term dietary creatine promotes largemouth bass brain health and neurodevelopment, enhance cognitive, and motor performance. In the future, creatine may have multiple potential applications in aquaculture, such as enhancing the adaptability of stock enhancement fish after returning to nature, strengthening cognitive and motor abilities thereby increasing the economic benefits of fish rearing and aquaculture production.