Double-edged effect of sodium citrate in Nile tilapia(Oreochromis niloticus):Promoting lipid and protein deposition vs.causing hyperglycemia and insulin resistance

Citrate is an essential substrate for energy metabolism that plays critical roles in regulating glucose and lipid metabolic homeostasis.However,the action of citrate in regulating nutrient metabolism in fish remains poorly understood.Here,we investigated the effects of dietary sodium citrate on growth performance and systematic energy metabolism in juvenile Nile tilapia(Oreochromis niloticus).A total of 270Nile tilapia(2.81±0.01 g)were randomly divided into three groups(3 replicates per group,30 fish per replicate)and fed with control diet(35%protein and 6%lipid),2%and 4%sodium citrate diets,respectively,for 8 weeks.The results showed that sodium citrate exhibited no effect on growth performance(P>0.05).The whole-body crude protein,serum triglyceride and hepatic glycogen contents were significantly increased in the 4%sodium citrate group(P<0.05),but not in the 2%sodium citrate group(P>0.05).The 4%sodium citrate treatment significantly increased the serum glucose and insulin levels at the end of feeding trial and also in the glucose tolerance test(P<0.05).The 4%sodium citrate significantly enhanced the hepatic phosphofructokinase activity and inhibited the expression of pyruvate dehydrogenase kinase isozyme 2 and phosphor-pyruvate dehydrogenase E1 component subunit alpha proteins(P<0.05).Additionally,the 4%sodium citrate significantly increased hepatic triglyceride and acetyl-Co A levels,while the expressions of carnitine palmitoyl transferase 1a protein were significantly down-regulated by the 4%sodium citrate(P<0.05).Besides,the 4%sodium citrate induced crude protein deposition in muscle by activating m TOR signaling and inhibiting AMPK signaling(P<0.05).Furthermore,the 4%sodium citrate significantly suppressed serum aspartate aminotransferase and alanine aminotransferase activities,along with the lowered expression of pro-inflammatory genes,such as nfκb,tnfa and il8(P<0.05).Although the 4%sodium citrate significantly increased phosphor-nuclear factor-k B p65 protein expression(P<0.05),no significant tissue damage or inflammation occurred.Taken together,dietary supplementation of sodium citrate could exhibit a double-edged effect in Nile tilapia,with the positive aspect in promoting nutrient deposition and the negative aspect in causing hyperglycemia and insulin resistance.

Unveiling the emerging role of curcumin to alleviate ochratoxin A-induced muscle toxicity in grass carp(Ctenopharyngodon idella):in vitro and in vivo studies

Background Ochratoxin A(OTA),a globally abundant and extremely hazardous pollutant,is a significant source of contamination in aquafeeds and is responsible for severe food pollution.The developmental toxicity of OTA and the potential relieving strategy of natural products remain unclear.This study screened the substance curcumin(Cur),which had the best effect in alleviating OTA inhibition of myoblast proliferation,from 96 natural products and investigated its effect and mechanism in reducing OTA myotoxicity in vivo and in vitro.Methods A total of 720 healthy juvenile grass carp,with an initial average body weight of 11.06±0.05 g,were randomly assigned into 4 groups:the control group(without OTA and Cur),1.2 mg/kg OTA group,400 mg/kg Cur group,and 1.2 mg/kg OTA+400 mg/kg Cur group.Each treatment consisted of 3 replicates(180 fish)for 60 d.Results Firstly,we cultured,purified,and identified myoblasts using the tissue block culture method.Through preliminary screening and re-screening of 96 substances,we examined cell proliferation-related indicators such as cell viability and ultimately found that Cur had the best effect.Secondly,Cur could alleviate OTA-inhibited myoblast differentiation and myofibrillar development-related proteins(Myo G and MYHC)in vivo and in vitro and improve the growth performance of grass carp.Then,Cur could also promote the expression of OTA-inhibited protein synthesis-related proteins(S6K1 and TOR),which was related to the activation of the AKT/TOR signaling pathway.Finally,Cur could downregulate the expression of OTA-enhanced protein degradation-related genes(murf1,foxo3a,and ub),which was related to the inhibition of the Fox O3a signaling pathway.Conclusions In summary,our data demonstrated the effectiveness of Cur in alleviating OTA myotoxicity in vivo and in vitro.This study confirms the rapidity,feasibility,and effectiveness of establishing a natural product screening method targeting myoblasts to alleviate fungal toxin toxicity.

Dietary isoleucine improved flesh quality,muscle antioxidant capacity,and muscle growth associated with AKT/TOR/S6K1 and AKT/FOXO3a signaling in hybrid bagrid catfish(Pelteobagrus vachelli♀×Leiocassis longirostris♂)

Background:Muscle is the complex and heterogeneous tissue,which comprises the primary edible part of the trunk of fish and mammals.Previous studies have shown that dietary isoleucine(Ile)exerts beneficial effects on growth in aquatic animals.However,there were limited studies regarding the benefits of Ile on fish muscle and their effects on flesh quality and muscle growth.Thus,this study was conducted to explore whether dietary Ile had affected flesh quality and muscle growth in hybrid bagrid catfish(Pelteobagrus vachelli♀×Leiocassis longirostris♂).Methods:A total of 630 hybrid fish,with an initial average body weight of 33.11±0.09 g,were randomly allotted into seven experimental groups with three replicates each,and respectively fed seven diets with 5.0,7.5,10.0,12.5,15.0,17.5,and 20.0 g Ile/kg diets for 8 weeks.Results:In the present study,we demonstrated that Ile significantly:(1)increased muscle protein and lipid contents and the frequency distribution of myofibers with≤20μm and≥50μm of diameter;(2)improved pH value,shear force,cathepsin B and L activities,hydroxyproline content,resilience,cohesiveness,and decreased cooking loss,lactate content,hardness,springiness,gumminess,and chewiness;(3)decreased reactive oxygen species(ROS),malondialdehyde(MDA),and protein carbonyl(PC)contents,GCLC and Keap1 mRNA levels,and up-regulated CuZnSOD,CAT,GPX1a,GST,and Nrf2 mRNA levels;(4)up-regulated the insulin-like growth factor 1,2(IGF-1,IGF-2),insulin-like growth factor 1 receptor(IGF-1R),proliferating cell nuclear antigen(PCNA),Myf5,Myod,Myog,Mrf4,and MyHC mRNA levels,and decreased MSTN mRNAlevel;(5)increased muscle protein deposition by activating AKT-TOR-S6K1 and AKT-FOXO3a signaling pathways.Conclusion:These results revealed that dietary Ile improved flesh quality,which might be due to increasing nutritional content,physicochemical,texture parameters,and antioxidant ability;promoting muscle growth by affecting myocytes hyperplasia and hypertrophy,and muscle protein deposition associated with protein synthesis and degradation signaling pathways.Finally,the quadratic regression analysis of chewiness,ROS,and protein contents against dietary Ile levels suggested that the optimal dietary Ile levels for hybrid bagrid catfish was estimated to be 14.19,12.36,and 12.78 g/kg diet,corresponding to 36.59,31.87,and 32.96 g/kg dietary protein,respectively.

Glucose supplementation improves intestinal amino acid transport and muscle amino acid pool in pigs during chronic cold exposure

Mammals in northern regions chronically suffer from low temperatures during autumn-winter seasons.The aim of this study was to investigate the response of intestinal amino acid transport and the amino acid pool in muscle to chronic cold exposure via Min pig models(cold adaptation)and Yorkshire pig models(non-cold adaptation).Furthermore,this study explored the beneficial effects of glucose supplementation on small intestinal amino acid transport and amino acid pool in muscle of cold-exposed Yorkshire pigs.Min pigs(Exp.1)and Yorkshire pigs(Exp.2)were divided into a control group(17℃,n=6)and chronic cold exposure group(7℃,n=6),respectively.Twelve Yorkshire pigs(Exp.3)were divided into a cold control group and cold glucose supplementation group(8℃).The results showed that chronic cold exposure inhibited peptide transporter protein 1(PepT1)and excitatory amino acid transporter 3(EAAT3)expression in ileal mucosa and cationic amino acid transporter-1(CAT-1)in the jejunal mucosa of Yorkshire pigs(P<0.05).In contrast,CAT-1,PepT1 and EAAT3 expression was enhanced in the duodenal mucosa of Min pigs(P<0.05).Branched amino acids(BCAA)in the muscle of Yorkshire pigs were consumed by chronic cold exposure,accompanied by increased muscle RING-finger protein-1(MuRF1)and muscle atrophy F-box(atrogin-1)expression(P<0.05).More importantly,reduced concentrations of dystrophin were detected in the muscle of Yorkshire pigs(P<0.05).However,glycine concentration in the muscle of Min pigs was raised(P<0.05).In the absence of interaction between chronic cold exposure and glucose supplementation,glucose supplementation improved CAT-1 expression in the jejunal mucosa and PepT1 expression in the ileal mucosa of cold-exposed Yorkshire pigs(P<0.05).It also improved BCAA and inhibited MuRF1 and atrogin-1 expression in muscle(P<0.05).Moreover,dystrophin concentration was improved by glucose supplementation(P<0.05).In summary,chronic cold exposure inhibits amino acid absorption in the small intestine,depletes BCAA and promotes protein degradation in muscle.Glucose supplementation ameliorates the negative effects of chronic cold exposure on amino acid transport and the amino acid pool in muscle.