A new vision of Panax ginseng leaf polysaccharide function: multiple roles in improving growth, flesh quality and muscle energy metabolism of sub-adult grass carp (Ctenopharyngodon idella)

BACKGROUND: As living standards improve, consumers are placing greater emphasis on the enhancement of fish flesh quality, making its improvement increasingly critical. Plant-derived polysaccharides positively affect the improvement of animal flesh quality. Panax ginseng leaf polysaccharides (PGLP) have a similar composition and lower cost compared with Panax ginseng root polysaccharides. However, its function and application effects in grass carp (Ctenopharyngodon idella) are unclear. METHODS: A total of 540 sub-adult grass carp (679 ± 1.29 g), one of the important economic fish species, were used as experimental models and fed diets supplemented with 0, 100, 200, 300, 400, or 500 mg/kg PGLP for 60 d. After 60 d, grass carp were weighed, and their muscles were collected to explore the effects of PGLP on the growth and development of myofibers and energy metabolism-related parameters. RESULTS: Our study found that PGLP increased the growth performance and muscle nutritional composition as well as improved muscle hardness, springiness, cohesiveness, chewiness, and hyperplasia of myofibers of sub-adult grass carp. Besides, PGLP promoted muscle energy metabolism by increasing creatine, glycogen, pyruvate, and acetyl-CoA contents and creatine kinase (CK), pyruvate kinase (PK), phosphofructokinase (PFK), and hexokinase (HK) activities, while decreasing lactate dehydrogenase (LDH) activity and lactate content in fish muscle. Finally, our study found that PGLP enhanced mitochondrial function by increasing the protein expression of mitochondrial complexes I-V, biogenesis, and fusion and decreasing autophagy and fission in fish muscle. CONCLUSIONS: PGLP improved growth performance and flesh quality of sub-adult grass carp, which may be related to enhancing hyperplasia of myofibers by promoting energy metabolism. We concluded that the recommended amount of PGLP in sub-adult grass carp feed to optimize growth performance is 100-200 mg/kg. This study provides a theoretical basis for the application of PGLP in fish feed and for the analysis of the mechanism of nutrition and feed regulating fish flesh quality, which is of great significance.