A comparative study on the effects of supplemental L-carnitine on fatty acids composition, energy status and related genes expression in Cyprinus carpio var. Jian and Rhynchocypris lagowskii (Dybowski, 1869)

This study was to compare study on the effects of supplemental L-carnitine on fatty acids composition, energy status and related genes expression in Cyprinus carpio var. Jian and Rhynchocypris lagowskii. Different concentrations of L-carnitine were added to the basal diets of two species of fish, in which Cyprinus carpio were supplemented with 0, 50 (LC), 200 (AC) and 800 (HC) mg/kg, and Rhynchocypris lagowskii were supplemented at 0, 200 (LC), 400 (AC) and 800 (HC) mg/kg, respectively, for 8 weeks. Results showed that in liver of AC group on C. carpio, the changes of HUFA and ∑DHA+EPA showed a significant downward trend, while the changes of PUFA, EFA and ∑n3 + n6 showed an upward trend. The above trend in liver of the AC group on R. lagowskii was opposite to C. carpio. With the exception of HUFA, the changes of fatty acids of AC group in muscles of the two fish were completely different. The content of ATP and AMP in liver and muscle in AC and HC groups of two fish species showed a decreasing trend, while the change trend of ADP content was opposite. AMP/ATP ratio in liver and muscle showed a trend of first increasing and then decreasing in the treatment groups of two fish species. The relative gene expression levels of AMPKα1, AMPKα2, ACC2 and CPT-I of liver and muscle in treatment groups of C. carpio showed a decreasing trend, while these values showed an opposite trend in liver of R. lagowskii. Consequently, the different fish species may be the main reason that affects the regulation of fatty acid metabolism by exogenous L-carnitine. In addition, AMPK, acting as an energy receptor is a key effector in regulation of fatty acids metabolism by L-carnitine. Further study of AMPK function in fatty acids metabolism of fish is thus warranted.