| The use of fat-rich feeds has made fish farming more cost-effective because protein is a relatively expensive source of energy.Supplementing diets with fat enables the protein to be ‘‘spared’’ for the synthesis of new tissue.Indeed,dietary lipid levels support higher growth rates and extra dietary protein in some species.However,suboptimal and/or excess levels of lipid may have an adverse effect on growth and unwanted fat deposition in the liver,inducing a condition referred to as ‘‘fatty liver’’ which often correlates with mortality.Several additives have been substantiated to be effective in controlling the accumulation of extra fat in the fish tissues and also regulate the expressions of the primary genes involved in lipid metabolism and as well enhance antioxidant and immune response without having any adverse on growth performance.Thus,this experiment consists of three parts in the approach of the alleviating effect of high-fat feeding using and additive.Experiment 1.Dietary supplementation of glycyrrhetinic acid,berberine,and resveratrol benefits the growth,antioxidant capability,innate immunity,and lipid metabolism of channel catfish(Ictalurus punctatus)fed high-fat diets: A comparative studyThis study aimed to investigate the effects of glycyrrhetinic acid(GA),berberine(B),and resveratrol(R)dietary supplementation on growth,feed utilization,and expression of lipid metabolism genes in channel catfish(Ictalurus punctatus)fed on a high-fat diet.Fish(average weight,20 ± 0.15 g)were distributed randomly in 15 tanks(3 × 0.8 × 0.8 m)at a density of stocking 11 fish per tank.Fish were distributed randomly to five experimental diets(Control diet(ND);High fat diet(HFD);High fat diet + 0.3 mg/kg glycyrrhetinic acid(HFD+GA),High fat diet + 50 mg/kg berberine(HFD+B)and High fat diet + 400 mg/kg resveratrol(HFD+R).Each diet was tested in triplicates for six weeks.From our result,the survival rate(SR)and total feed intake(TFI)were not affected by dietary treatment.However,final body weight(FBW),body weight gain(BWG),and specific growth rate(SGR)were significantly lower(P<0.05)in fish fed on HFD,whereas the opposite trend was seen in feed conversation ratio(FCR).However,the supplemented group enhanced these parameters with the highest level obtained in fish fed on HFD+GA.Fish fed on HFD obtained a significantly higher(P<0.05)Hepatosomatic index(HSI),Visceralsomatic index(VSI),and Mesenteric fat index(MFI),whereas the opposite was true for condition factor(CF).The supplemented restored these parameters similar to the control groups.Whole-body crude protein was higher in fish fed on HFD+GA compare to those fed on HFD,but no difference was attributed to other groups.Meanwhile,fish fed on HFD obtained higher EE compare to the control,but fish fed on the supplemented group restored their parameter similar to the control with the lowest seen in fish fed on HFD+GA and HFD+B diet(P<0.05).Fish fed on HFD show a higher trend(P<0.05)in glucose,cortisol,aspartate aminotransferase(AST),alanine aminotransferase(ALT),liver total cholesterol(TC),triglycerides(TG),and Low-density lipoprotein(LDL)while the opposite trend was found for Total protein(TP)and High-density lipoprotein(HDL).These parameters were all enhanced by feeding the supplemented diet.Liversuperoxide dismutase(SOD),Catalase(CAT),Glutathione peroxidase(GPx),Plasma lysozyme(LYM),Myeloperoxidase(MPO),Alkaline phosphatase(AKP),Acid phosphatase(ACP)activities,and Immunoglobulin M(Ig M)level were all lower in fish fed on HFD as compared to the control group.However,supplementing HFD with GA,berberine,and resveratrol restored these parameters similar to control.The group supplemented with GA was significantly higher in GPx than other supplemented groups.Hepatic expressions of fatty acid synthase(FAS),sterol regulatory element-binding protein 1(SREBP1),liver X receptor(LXR),and hormone-sensitive lipase(HSL)of the group fed on HFD were significantly higher(P<0.05)and lower acetyl-Co A carboxylase alpha(ACCα),acyl-Co A oxidase(ACO),carnitine palmitoyltransferase 1(CPT1),microsomal triglyceride transfer protein(MTTP),and peroxisome proliferator-activated receptor alpha(PPARα)compare to the control group.This damage was all reversed by feeding glycyrrhetinic acid,berberine,and resveratrol diet.In conclusion,glycyrrhetinic acid,berberine,and resveratrol could enhance growth,immune response,antioxidant,and lipid metabolism genes in channel catfish fed on HFD.Experiment 2.Testing the effects of glycyrrhetinic acid(GA)on the lipid metabolism of channel catfish(Ictalurus punctatus)by intraperitoneal injection and hepatopancreas cell culture.Fatty liver always strongly correlates with low growth and reduced harvest yield.However,some herbs in China can reduce the storage of hepatic fat.This study aimed to examine the lipid-lowering effect of glycyrrhetinic acid(GA)in channel catfish(Ictalurus punctatus)in vitro.Two different methods were performed to measure the effect of GA on the metabolism of fats in the fingerling of catfish.First method: GA injected directly into the abdominal cavity,where fish were fed on a high-fat diet with different time points(0H,3H,6H,12 H,18H,24 H & 36H),and the highest TG level was found at 18 hours so this time was chosen to treat with GA.The fish were then injected with five levels of GA(0,0.15,0.3,0.6,1.2 mg/kg)in two diets groups of fish;normal-fat diet(ND)and high-fat diet(HFD).Injections of GA in channel catfish enhanced plasma and liver TC,TG,HDL & LDL,and lipid metabolism gene expression compared to HFD and ND.Nevertheless,treatment with GA significantly decreased gene expression of inositol requiring enzyme 1(IRE1),spliced X box-binding protein 1(xbp1s),Dna J heat shock protein family(Hsp40)member B9(DNAJB9),and glucose-regulated protein 78(GRP78),an increased level of gene expression of MTTP and Apolipoprotein B(Apo B)in both ND groups and HFD groups.Best results of lipid profile parameters and gene expression of lipid metabolism genes have been observed at the injection level of 0.3 mg/kg GA both in ND and HFD.Second method: cell culture of catfish hepatopancreas,5 different levels of GA(0-0.15-0.3-0.6-1.2)μM were tested with oleic acid(OA)as a fat source with a concentration of 0.4 m M.The use of GA with OA in cell culture led to reduced IRE1,xbp1 s,DNAJB9,and GRP78,and increased MTTP & Apo B expression level,while the opposite was observed when treated with OA alone.The best expression level was at a concentration of 0.3 μM GA.In conclusion,a high-fat diet could lead to aberrant lipid secretion by activating the IRE1/XBP1 pathway.However,adding GA restored this parameter to the normal level.Experiment 3.Influences of various levels of glycyrrhetinic acid(GA)dietary supplementation on growth,feed utilization,and expression of lipid metabolism genes in channel catfish(Ictalurus punctatus)fed on a high-fat diet.An 8-week feeding trial was conducted to evaluate the effects of glycyrrhetinic acid(GA)on growth and the expression of some genes related to hepatic lipid metabolism in channels catfish(initial body weight,3.5±0.02 g)fed on high-fat diets.In 15 tanks with a stocking density of 21 fish/tank,fish were fed on the control diet(6% fat),high-fat diet(HFD,11%fat),and HFD supplemented with 0.4,0.8,and 1.2 mg/kg GA.Fish fed on HFD were significantly lower in BWG and SGR,but higher in TFI and FCR than control.Compared with the control diet,the GA supplement at 1.2 mg/kg remarkably enhanced these parameters.In fish fed on with HFD,high levels of TC,TG,LDL,and low plasma levels of HDL were observed;the contrary was found for fish fed on HFD combined with GA.Also,FAS,SREBP1,LXRα,HSL m RNA expression were downregulated.In contrast,the transcription of CPT1,PPARα,ACO,MTTP were downregulated in fish fed on HFD.In conclusion,adding 1,2 mg/kg of GA to HFD could boost the growth performance,and lipid metabolism of channel catfish fed on HFD. |
