Effects of Dietary L-Carnitine on the Growth Performance, Hepatic Lipid Deposition and Fatty Acid β-Oxidation in Tiger Puffer (Takifugu rubripes) Fed with High-Fat Diets

This study was conducted to explore the impacts of L-carnitine (CAR) on growth performance, antioxidant capacity, hepatic lipid deposition and fatty acid β-oxidation in farmed fish fed a high-fat diet (HFD). A total of 150 juvenile tiger puffer (15.23 ± 0.01 g) were randomly assigned into six tanks (three tanks each group) and fed with a control diet (HFD, 16% lipid) and a HFD supplemented with 1.5% CAR for eight weeks, respectively. The results indicated that the growth performance and the most proximate compositions were not influenced by dietary CAR. However, compared to the control group, the hepatosomatic index and crude lipid content in the liver were significantly reduced in the CAR group, indicating that CAR performed a lipid-lowering effect in tiger puffer. Serum lipid profiles remained stable, implying that the cholesterol metabolism was not influenced by dietary CAR. Furthermore, dietary CAR activated fatty acid β-oxidation (FAO) in both the mitochondria and peroxisomes and drove lipolysis and fatty acid intracellular transport to supply sufficient substrates for FAO, manifested by the activation of related genes, proteins and enzyme activity. Additionally, CAR lowered hepatic MDA levels, indicating improved antioxidant capacity. In conclusion, CAR shows potential as a lipid-lowering feed additive for marine fish under high-fat dietary conditions.