Dietary sodium acetate and sodium butyrate improve high-carbohydrate diet utilization by regulating gut microbiota, liver lipid metabolism, oxidative stress, and inflammation in largemouth bass(Micropterus salmoides)

Background Adequate level of carbohydrates in aquafeeds help to conserve protein and reduce cost. However, studies have indicated that high-carbohydrate(HC) diet disrupt the homeostasis of the gut–liver axis in largemouth bass, resulting in decreased intestinal acetate and butyrate level.Method Herein, we had concepted a set of feeding experiment to assess the effects of dietary sodium acetate(SA) and sodium butyrate(SB) on liver health and the intestinal microbiota in largemouth bass fed an HC diet. The experimental design comprised 5 isonitrogenous and isolipidic diets, including LC(9% starch), HC(18% starch), HCSA(18% starch;2 g/kg SA), HCSB(18% starch;2 g/kg SB), and HCSASB(18% starch;1 g/kg SA + 1 g/kg SB). Juvenile largemouth bass with an initial body weight of 7.00 ± 0.20 g were fed on these diets for 56 d.Results We found that dietary SA and SB reduced hepatic triglyceride accumulation by activating autophagy(ATG101, LC3B and TFEB), promoting lipolysis(CPT1α, HSL and AMPKα), and inhibiting adipogenesis(FAS, ACCA, SCD1 and PPARγ). In addition, SA and SB decreased oxidative stress in the liver(CAT, GPX1α and SOD1) by activating the Keap1-Nrf2 pathway. Meanwhile, SA and SB alleviated HC-induced inflammation by downregulating the expression of pro-inflammatory factors(IL-1β, COX2 and Hepcidin1) through the NF-κB pathway. Importantly, SA and SB increased the abundance of bacteria that produced acetic acid and butyrate(Clostridium_sensu_stricto_1). Combined with the KEGG analysis, the results showed that SA and SB enriched carbohydrate metabolism and amino acid metabolism pathways, thereby improving the utilization of carbohydrates. Pearson correlation analysis indicated that growth performance was closely related to hepatic lipid deposition, autophagy, antioxidant capacity, inflammation, and intestinal microbial composition.Conclusions In conclusion, dietary SA and SB can reduce hepatic lipid deposition;and alleviate oxidative stress and inflammation in largemouth bass fed on HC diet. These beneficial effects may be due to the altered composition of the gut microbiota caused by SA and SB. The improvement effects of SB were stronger than those associated with SA.

Thermal cracking characteristics of n-decane in the rectangular and circular tubes

To investigate the effect of regenerative cooling channel geometry on pyrolysis of endothermic hydrocarbon fuel,a series of supercritical pyrolysis experiments of n-decane in the rectangular and circular tubes were conducted.Moreover,sensitivity analysis of production of propylene and methane as well as CFD simulation were also done.The results showed that gas yield and conversion in the circular tube with an inner diameter of 2 mm had a similar tendency with the one of 1.5 mm in inner diameter.The conversion in the circular tube was much less than that in the rectangular tube at the same outlet temperature.The heat sink of the rectangular tube at the same outlet temperature was larger than that of circular tubes,but the temperature at the corner of the rectangular tube was relatively high.According to the experimental data of the test tubes,a correlation between the conversion and the temperature in the rectangular and circular tubes at the same outlet temperature was fitted,providing a reference for the design of regenerative cooling channels.

Dietary sodium acetate and sodium butyrate attenuate intestinal damage and improve lipid metabolism in juvenile largemouth bass(Micropterus salmoides)fed a high carbohydrate diet by reducing endoplasmic reticulum stress

High-carbohydrate(HC)diets decrease the intestinal levels of sodium acetate(SA)and sodium butyrate(SB)and impair the gut health of largemouth bass;however,SA and SB have been shown to enhance immunity and improve intestinal health in farmed animals.Thus,the present study was to investigate the effects of dietary SA and SB on HC diet-induced intestinal injury and the potential mechanisms in juvenile largemouth bass.The experiment set five isonitrogenous and isolipidic diets,including a lowcarbohydrate diet(9%starch)(LC),a high carbohydrate diet(18%starch)(HC),and the HC diet supplemented with 2 g/kg SA(HCSA),2 g/kg SB(HCSB)or a combination of 1 g/kg SA and 1 g/kg SB(HCSASB).The feeding experiment was conducted for 8 weeks.A total of 525 juvenile largemouth bass with an initial body weight of 7.00±0.20 g were used.The results showed that dietary SA and SB improved the weight gain rate and specific growth rate(P<0.05)and ameliorated serum parameters(alkaline phosphatase,acid phosphatase,glutamate transaminase,and glutamic oxaloacetic transaminase)(P<0.05).And,importantly,dietary SA and SB repaired the intestinal barrier by increasing the expression levels of zonula occludens-1,occludin,and claudin-7(P<0.05),reduced HC-induced intestinal damage,and alleviated intestinal inflammation and cell apoptosis by attenuating HC-induced intestinal endoplasmic reticulum stress(P<0.05).Further results revealed that dietary SA and SB reduced HC-induced intestinal fat deposition by inhibiting adipogenesis and promoting lipolysis(P<0.05).In summary,this study demonstrated that dietary SA and SB attenuated HC-induced intestinal damage and reduced excessive intestinal fat deposition in largemouth bass.