Effects of Corbicula fluminea meal in high-fat diet on growth, lipid metabolism and intestinal microbiota of juvenile rice field eel Monopterus albus

Corbicula fluminea meal was added to a high-fat diet for eight weeks to determine its effects on growth, lipid metabolism, and intestinal microbiota in juvenile rice field eel (Monopterus albus). C. fluminea meal was made of dried and crushed soft parts of freshwater clam. The study included four diets: a normal fat diet (6.63% lipid, CON), a high fat diet (12.61% lipid, HFD), and a high fat diet supplemented with 1% or 2% C. fluminea meal (CFM1 and CFM2, respectively). The results showed that: (1) the growth performance was higher in the HFD, CFM1 and CFM2 group compared with the CON group, the hepatosomatic index (HSI) was significantly higher in fish fed the high-fat diet than in those fed other diets. (2) Compared with the CON group, The levels of serum triacylglycerol (TG), low-density lipoprotein cholesterol (LDL-C) contents, glutamate pyruvic transaminase (GPT), glutamic oxaloacetic transaminase (GOT) activities and the number of hepatic lipid droplets were significantly increased in the HFD group. The addition of C. fluminea meal both reduced liver damage and fat deposition. (3) The mRNA expressions of pparγ, fas, acc, me1, srebp1, g6pdh, hsl, lpl, cpt1, and cpt2 in the HFD group were significantly upregulated, while HFD supplemented with C. fluminea meal significantly downregulated the mRNA expressions of pparγ, fas, acc, me1, srebp1 and g6pdh and significantly upregulated the mRNA expressions of hsl and lpl. (4) The alpha diversity of intestinal microbial community in the HFD group was higher than those in the CON and CFM1 groups. The beta diversity revealed the microbial composition differed in the HFD group from the CON and CFM1 groups. The abundance of Firmicutes in the HFD group increased significantly compared with the CON and CFM1 groups, while the abundances of Cetobacterium decreased. In conclusion, the high-fat diet resulted in abnormal liver fat deposits and intestinal microbiota dysfunction in M. albus, but HFD supplemented with 1% or 2% C. fluminea meal reduced these negative effects.