Effects of paraprobiotics on bile acid metabolism and liver health in largemouth bass(Micropterus salmoides)fed a cottonseed protein concentrate-based diet

Cottonseed protein concentrate is a sustainable fishmeal alternative in aquafeed.A 10-week experiment was conducted to investigate the effects of a cottonseed protein concentrate-based diet with and without multi-strain yeast fractions(MsYF)on growth,bile acid metabolism,and health in largemouth bass.Four hundred fish(54.0±0.0 g)were casually distributed into 16 tanks(4 replicates/diet).Fish were fed with 4 iso-nitrogen and iso-energetic diets 3 times daily,including a fishmeal diet(FM),a soy protein concentrate-based diet(SPC;replacing 81%fishmeal protein),a cottonseed protein concentrate-based diet(CPC;replacing 81%fishmeal protein),and a CPC diet supplemented with 800 mg/kg MsYF(CPCY).Results showed that the survival of SPC was the lowest,i.e.,48%,with no apparent diet effect among other treatments;we omitted the SPC in additional analyses.Fish fed cottonseed protein concentrate-based diets showed lower growth than FM(P<0.05).Fish fed CPC showed the highest nuclear dense hepatic phenotypes ratio(50%),followed by CPCY(33%)and FM(17%).Further,dietary CPC increased hepatic total cholesterol and triglyceride levels with concurrently increased cholesterol syn-thesis but decreased triglyceride synthesis-associated transcription levels(P<0.05).Furthermore,di-etary CPC increased bile acid synthesis but decreased bile acid transport-associated transcription levels(P<0.05),and then induced an increment of plasma cholic acid and hepatic chenodeoxycholic acid content and the decrement of genus Romboustia(P<0.05).Regarding the effect of MsYF,fish fed CPCY reduced hepatic lipid accumulation and total plasma bile acid content(P<0.05)compared to CPC,suggesting an improvement in liver health.Also,dietary MsYF could reverse the microbiota community structure showing a similar gut microbial composition to FM.In conclusion,81%of fishmeal protein replaced by cottonseed protein concentrate suppressed growth and liver health,while dietary MsYF might mitigate the negative impact of a high cottonseed protein concentrate level diet on liver functions via gut microbiota regulation.

Gluconeogenesis during starvation and refeeding phase is affected by previous dietary carbohydrates levels and a glucose stimuli during early life in Siberian sturgeon(Acipenser baerii)

Gluconeogenesis responses was assessed during a short starvation period and subsequent refeeding in Siberian sturgeon(Acipenser baerii) previously fed different dietary carbohydrates levels and experienced to a glucose stimuli during early life. The sturgeon larvae were previously fed either a high glucose diet(G) or a low glucose diet(F) from the first feeding to yolk absorption(8 to 12 d post-hatching [dph]). Each group of fish was sub-divided into 2 treatments at 13 dph and was fed either a high-carbohydrate diet(H) or a low carbohydrate diet(L) until 20 wk. In the current study, the fish in 4 groups(GL, FL, GH and FH) were experienced to starvation for 21 d following by re-feeding of their corresponding diets for 21 d.Fish were sampled at postprandial 6 and 24 h before starvation(P6 h and P24 h), starvation 7,14 and 21 d(S7, S14 and S21) and 1, 7,14 and 21 d during refeeding(R1, R7, R14 and R21). Plasma samples during refeeding were taken at P6 h at each time point. Glycaemia levels, liver and muscle glycogen contents,activities and mRNA levels of hepatic gluconeogenic enzymes were examined. We found that both dietary carbohydrate levels and early glucose stimuli significantly affected the metabolic responses to starvation and refeeding in Siberian sturgeon(P < 0.05). During prolonged starvation, Siberian sturgeon firstly mobilized the liver glycogen and then improved gluconeogenesis when the dietary carbohydrates were abundant, whereas preserved the liver glycogen stores at a stable level and more effectively promoted gluconeogenesis when the dietary carbohydrates are absent to maintain glucose homoeostasis.During refeeding, as most teleostean, Siberian sturgeon failed controlling the activities and mRNA levels of phosphoenolpyruvate carboxykinase cytosolic forms(PEPCK-C), fructose-1,6-bisphosphatase(FBPase),but particularly controlled phosphoenolpyruvate carboxykinase mitochondrial forms(PEPCK-M) activities and mRNA expression of glucose-6-phosphatase(G6 Pase, except in GL group). Siberian sturgeon has a full compensatory ability on growth, but this ability would be obstructed by early glucose stimuli when refeeding the low carbohydrate diet after S21.

A new single-cell protein from Clostridium autoethanogenum as a functional protein for largemouth bass(Micropterus salmoides)

Clostridium autoethanogenum protein(CAP)is a new single-cell protein source originating from inactivated bacteria.An in vitro digestion experiment and an 8-wk growth experiment were conducted to evaluate the molecular weight distribution of the CAP hydrolysate,and the effects of dietary CAP levels on the growth performance,plasma parameters,hepatic and intestinal health,and the diversity of gutadherent microbiota of largemouth bass(Micropterus salmoides).The fish(initial body weight of 47.99±0.01 g)were fed diets where CAP gradually replaced 0%(CAP0),12.5%(CAP12.5),25%(CAP25),37.5%(CAP37.5)and 50%(CAP50)of low-temperature steam dried anchovy fish meal(LTFM)in the diet.Results showed that the content of peptides below 1,000 Da in the CAP hydrolysate(0.56 mg/mL)was higher than that of the LTFM hydrolysate(0.48 mg/mL).Dietary CAP inclusion had no negative effect on growth performance,while whole-body lipid content significantly reduced in the CAP25 and CAP50 groups(P<0.05).The plasma alanine aminotransferase activities and triglyceride concentrations in the CAP inclusion groups were significantly lower than those in the CAP0 group(P<0.05).The plasma aspartate aminotransferase activity was significantly reduced in the CAP37.5 group(P<0.05).The richness and diversity of the gut-adhesive microbiota and the proportion of Clostridium sensu stricto 12 in the CAP50 group were significantly higher than those in the CAP0 group(P<0.05).Dietary CAP inclusion inhibited inflammatory responses by down-regulating the mRNA levels of interleukin 1b(IL1b),IL10 and transforming growth factor b1(P<0.05)in the liver.The mRNA levels of acetyl-CoA carboxylase 1 were significantly down-regulated in the CAP12.5,CAP25 and CAP37.5 groups(P<0.05),while that of fatty acid synthase was significantly down-regulated in the CAP50 group(P<0.05).These results demonstrate that dietary CAP inclusion could improve the hepatic and intestinal health of largemouth bass,and can be helpful to further develop CAP as a functional feed ingredient.

N-carbamoylglutamate improves lipid metabolism, inflammation, and apoptosis responses in visceral adipocytes of Japanese seabass (Lateolabrax japonicus), in vivo and in vitro

This study applied in vivo and in vitro methods to investigate the effect of dietary N-carbamoylglutamate(NCG)on lipid metabolism,inflammation and apoptosis related-gene expression in visceral adipose tissue and isolated adipocytes of Japanese seabass(Lateolabrax japonicus).A basal diet and a test diet supplemented with 720 mg/kg NCG were fed to the fish for 10 weeks.During the growth trial,no mortality and no significant differences in growth performance were observed in fish between the 2 groups(P>0.05).Plasma Arg content and mRNA level of argininosuccinate synthetase(ASS)in adipose tissue were significantly increased,which indicated that NCG inclusion promoted endogenous Arg synthesis.Thereafter,the potential effects of NCG treatment on lipid metabolism-related genes expression were studied through in vivo and in vitro methods.In the present study,we successfully established a primary adipocytes culture system and isolated pre-adipocytes in vitro of Japanese seabass for the first time.Both the results in vivo and in vitro showed that NCG treatment decreased the mRNA levels of genes related to adipogenesis(fatty acid synthase,FASN),cholesterol synthesis(3-hydroxy-3-methylglutaryl-CoA reductase,HMGCR)and fat deposition(lipoprotein lipase[LPL]and leptin),which revealed the underlying mechanism of NCG on reducing fat deposition.The results of this study demonstrated that NCG inclusion reduced the expression of inflammatory and apoptosis cytokines markedly in vivo and in vitro.In conclusion,NCG did exert beneficial effects on ameliorating adipo-genesis,inflammation and apoptosis via promoting Arg endogenous synthesis in Japanese seabass.