Tributyrin Plays an Important Role in Regulating the Growth and Health Status of Juvenile Blunt Snout Bream (Megalobrama amblycephala), as Evidenced by Pathological Examination

Glycerol tributylate (Triacylglycerol tributanoate) promoted the liver lipid metabolism by cultivating the intestinal flora of grass carp (Ctenopharyngodon idellus)

To investigate the effects of glycerol tributyrin (TB) (Triacylglycerol tributanoate) on the regulation of liver lipid metabolism by intestinal flora of grass carp (Ctenopharyngodon idellus). The compound feed with soybean oil 2.8% + fish oil 1.8%, soybean oil 6.3% + fish oil 1.8%, and soybean oil 6.2% + fish oil 1.8% + TB 0.1% was added to the basal diet as a fat source and fed to the basal (control) group, high lipid (HL) group, and tributyrin (TB) group for 12 weeks. We tested the growth performance, fat content, diversity, and abundance of gut flora and other related indexes of grass carp by Soxhlet extraction, liver tissue enzyme activity, oil red O staining, and 16S rRNA high-throughput sequencing. The results showed that the liver fat number and liver fat content of grass carp in the TB group were lower than those in the HL group, while the fattening degree was significantly higher than those in the other two groups; according to the indices such as Shannon, Ace, and Coverage, it was found that the grass carp in the TB group had the highest abundance and diversity of intestinal microflora; at the portal level, Proteobacteria and Fusobacteria were the main dominant flora in the TB group, with the number of unique OUTs accounting for about 59. 9% of the total number measured; at the genus level, the relative abundance of lipase-producing, short-chain fatty acid-associated bacteria, such as Bacillus-Lactobacillus and Bifidobacterium, was significantly lower (p < 0.05). Thus, we conclude that the addition of TB to high-fat diets can alter the structure of the intestinal microbial community and promote hepatic lipid metabolism in grass carp. TB can alleviate fatty liver in grass carp by increasing the relative abundance of short-chain fatty acids in the intestine. Meanwhile, TB inhibits the conversion of primary bile acids to secondary bile acids in the host, which can block intestinal FXR signaling and the hepatic FXR-SHP pathway, thus slowing down fat synthesis and alleviating the accumulation of liver lipids in grass carp.

Effects of Dietary Bacillus coagulans and Tributyrin on Growth Performance, Serum Antioxidants, Intestinal Morphology, and Cecal Microbiota of Growing Yellow-Feathered Broilers

This study investigated the impact of Bacillus coagulans (BC) and tributyrin (TB) supplementation on the growth performance, serum antioxidant capacity, intestinal morphology, and cecal microbiota of yellow-feathered broilers. Using a 2 × 2 factorial design, 480 broilers were randomly assigned to four experimental diets, comprising two levels of BC (0 and 1 g/kg) and two levels of TB (0 and 1 g/kg), over a 36-day period. A significant interaction was observed between BC and TB, impacting the average daily feed intake (ADFI) of broilers aged between 26 and 40 days (p < 0.01). BC and TB also displayed a significant interaction in relation to serum malondialdehyde levels and total antioxidant capacity (p < 0.05). Additionally, there was a significant interaction between BC and TB concerning the duodenal villus-to-crypt ratio, crypt depth, and jejunal villus-to-crypt ratio (p < 0.05). The addition of BC and TB significantly enhanced the richness and diversity of cecal microbiota, with a notable interactive effect observed for the abundance of Faecalibacterium, Ruminococcus_torques_group, and Phascolarctobacterium. In conclusion, supplementation with BC and TB can effectively improve the growth performance, serum antioxidant capacity, intestinal morphology, and cecal microbiota composition of yellow-feathered broilers, indicating the presence of an interactive effect.

Effects of morphological traits on body weight and analysis of growth-related genes of Parabramis pekinensis at different ages

Parabramis pekinensis was treated as research object in order to investigate the correlation between morphological traits and body weight. We measured 9 morphological indexes including total length (X1), body length (X2), body height (X3), head length (X4), snout length (X5), eye diameter (X6), eye distance (X7), caudal stalk length (X8) and caudal stalk height (X9). The principal morphological traits affecting body weight were screened out and the regression equation was established. The regression equation of Y1 (age 1 group) shape character (X) and weight (Y) was Y = - 169.183 + 32.544 × 3 + 10.263 × 4 + 15.655 × 7. The regression equation of Y2 (age 2 group) shape character (X) and weight (Y) was Y = - 694.082 + 7.725 × 1 + 72.822 × 3 + 77.023 × 6, the regression equation of Y3 (age 3 group) shape character (X) and weight (Y) was Y = - 1161.512 + 26.062 × 1 + 22.319 × 2- 107.218 × 5 + 83.901 × 7. Gene expression was consistent with these conclusions. TOR signaling pathway expression raised in Y1 then width increased. And GH-IGF-1 signaling pathway expression raised in Y2 then the length increased. In conclusion, the paper could prove that P. pekinensis showed a growth trend, which was increasing width first and length later. In some sense, the study not only enriched the basic biological data of P. pekinensis, but also provided waiting morphological traits for selective breeding of P. pekinensis artificial breeding in future.

Effects of tributyrin and alanyl-glutamine dipeptide on intestinal health of largemouth bass (Micropterus salmoides) fed with high soybean meal diet

To investigate the effects of dietary tributyrin (TB) and alanyl-glutamine (AGn) on the intestinal health of largemouth bass (Micropterus salmoides) fed with high-level soybean meal (SM) diet, six isonitrogenous (41.36%) and isolipidic (10.25%) diets were formulated and fed to largemouth bass (initial body weight 25.5 ± 0.5g) for 8 weeks. The two control diets contained 34.8% peanut meal (PM) and 41.3% SM, while the other four experimental diets supplemented TB at 0.1% (TB0.1), 0.2% (TB0.2) and AGn at 1% (AGn1), 2% (AGn2) in SM, respectively. The results showed that there were no significant differences in weight gain, survival rate, and hepatosomatic index among all groups (P>0.05), while feed coefficient rate in AGn1, AGn2 and TB0.2 groups was significantly lower than that in SM group (P< 0.05). Compared with the PM group, the intestinal inflammation of largemouth bass in SM group were obvious, accompanied by the damage of intestinal structure, the decrease of digestive enzyme activity, and the up-regulation of proinflammatory cytokines. Compared with the SM group, the activities of intestinal trypsin, lipase and foregut amylase in TB and AGn groups increased significantly (P<0.05), and the gene expression levels of acetyl-CoA carboxylase (ACC), caspase-3, caspase-8, caspase-9, tumor necrosis factor alpha (TNF-α), and interleukin-1 beta (IL-1β) were down-regulated, while the gene expression levels of target of rapamycin (TOR) and eIF4E-binding protein (4E-BP) were up-regulated in all experimental groups (P<0.05). It can be concluded that supplementation of 1%-2% AGn and 0.1%-0.2% TB can alleviate enteritis caused by high-level soybean meal, and the recommend level is 2% AGn and 0.2% TB.

Histidine Deficiency Inhibits Intestinal Antioxidant Capacity and Induces Intestinal Endoplasmic-Reticulum Stress, Inflammatory Response, Apoptosis, and Necroptosis in Largemouth Bass (Micropterus salmoides)

This 56-day study aimed to evaluate the effects of histidine levels on intestinal antioxidant capacity and endoplasmic-reticulum stress (ERS) in largemouth bass (Micropterus salmoides). The initial weights of the largemouth bass were (12.33 ± 0.01) g. They were fed six graded levels of histidine: 0.71% (deficient group), 0.89%, 1.08%, 1.26%, 1.48%, and 1.67%. The results showed that histidine deficiency significantly suppressed the intestinal antioxidant enzyme activities, including SOD, CAT, GPx, and intestinal level of GSH, which was supported by significantly higher levels of intestinal MDA. Moreover, histidine deficiency significantly lowered the mRNA level of nrf2 and upregulated the mRNA level of keap1, which further lowered the mRNA levels of the downstream genes sod, cat, and gpx. Additionally, histidine-deficiency-induced intestinal ERS, which was characterized by activating the PEPK-signalling pathway and IRE1-signalling pathway, including increased core gene expression of pepk, grp78, eif2α, atf4, chopα, ire1, xbp1, traf2, ask1, and jnk1. Dietary histidine deficiency also induced apoptosis and necroptosis in the intestine by upregulating the expressions of proapoptotic genes, including caspase 3, caspase 8, caspase 9, and bax, and necroptosis-related genes, including mlkl and ripk3, while also lowering the mRNA level of the antiapoptotic gene bcl-2. Furthermore, histidine deficiency activated the NF-κB-signalling pathway to induce an inflammatory response, improving the mRNA levels of the proinflammatory factors tnf-α, hepcidin 1, cox2, cd80, and cd83 and lowering the mRNA levels of the anti-inflammatory factors tgf-β1 and ikbα. Similarly, dietary histidine deficiency significantly lowered the intestinal levels of the anti-inflammatory factors TGF-β and IL-10 and upregulated the intestinal levels of the proinflammatory factor TNF-α, showing a trend similar to the gene expression of inflammatory factors. However, dietary histidine deficiency inhibited only the level of C3, and no significant effects were observed for IgM, IgG, HSP70, or IFN-γ. Based on the MDA and T-SOD results, the appropriate dietary histidine requirements of juvenile largemouth bass were 1.32% of the diet (2.81% dietary protein) and 1.47% of the diet (3.13% dietary protein), respectively, as determined by quadratic regression analysis.

Dietary Histidine Supplementation Maintained Amino Acid Homeostasis and Reduced Hepatic Lipid Accumulation of Juvenile Largemouth Bass, Micropterus Salmoides

This 56-day research aimed to evaluate the recommended histidine requirement and the influence of dietary histidine levels on the protein and lipid metabolism of juvenile largemouth bass (Mieropterus salmoides). The initial weight of the largemouth bass was 12.33 ± 0.01 g, which was fed with six graded levels of histidine. The results showed that appropriate dietary histidine had a positive effect on growth, with a higher specific growth rate, final weight, weight gain rate, protein efficiency rate, and a lower feed conversion rate and feed intake rate being observed in 1.08-1.48% dietary histidine groups. Furthermore, the mRNA levels of GH, IGF-1, TOR, and S6 showed an increasing trend first and then declined, similar to the trend of the growth and protein content of the whole body composition. Meanwhile, dietary histidine levels could be sensed by the AAR signaling pathway, representing as downregulation of core genes of AAR signaling pathway with the increased dietary histidine levels, including GCN2, eIF2α, CHOP, ATF4, and REDD1. In addition, increased dietary histidine levels decreased the lipid content of the whole body and the liver by upregulating the mRNA levels of core genes of the PPARα signaling pathways, including PPARα, CPT1, L-FABP, and PGC1α. However, increased dietary histidine levels downregulated the mRNA levels of core genes of the PPARγ signaling pathways such as PPARγ, FAS, ACC, SREBP1, and ELOVL2. These findings were also supported by the positive area ratio of hepatic oil red O staining and the TC content of plasma. According to the specific growth rate and feed conversion rate, the recommended histidine requirement of juvenile largemouth bass was 1.26% of the diet (2.68% of dietary protein) by regression lines calculated using a quadratic model. In general, histidine supplementation promoted protein synthesis and lipid decomposition and reduced lipid synthesis by activating the TOR, AAR, PPARα, and PPARγ signaling pathways, which provided a new perspective to solve the fatty liver problem of largemouth bass by nutritional means.

Effect of Tributyrin on Growth Performance and Pathway by which Tributyrin Regulates Oligopeptide Transporter 1 in Juvenile Grass Carp (Ctenopharyngodon idellus)

Simple Summary

Oligopeptide transporter 1 (PepT1) plays a role in the transportation and absorption of oligopeptides, which is an important part of protein nutrition and affects the growth of animals. Tributyrin (TB), the precursor of butyrate, exhibits similar functions to those of the butyrate in intestinal nutrients absorption. The analysis of TB on the growth of grass carp and its regulation pathway on PepT1 may help us to better understand the functions of TB and oligopeptide transportation via PepT1, which can be modulated by diet. In this study, we demonstrated that an appropriate level of tributyrin supplementation in the diet promoted the growth of juvenile grass carp and elevated the expressions of caudal type homeobox 2 (CDX2), specificity protein 1 (SP1), and PepT1 in the grass carp intestine and primary intestine cell. In addition, CDX2 and SP1 regulating the expression of PepT1 was investigated. Finally, CDX2/SP1-mediating tributyrin regulation on PepT1 was elucidated. This study verified the effect of tributyrin on the growth of juvenile grass carp and clarified the tributyrin regulation pathway on CDX2/SP1-PepT1.

Abstract

The nutritional functions of tributyrin (TB) have been extensively studied, but questions remain regarding its influence on the growth of juvenile grass carp (Ctenopharyngodon idellus) and the regulation pathway to PepT1 in the intestine of grass carp. To answer the remaining questions, feeding trials, cell trials, and peritoneal injection trials were conducted in this study. The results showed that an appropriate level of TB (0.5 g/kg and 1.0 g/kg) supplementation in feed significantly promoted the growth performance of juvenile grass carp. The expressions of intestine genes (CDX2, SP1 and PepT1) related to oligopeptide transportation increased in the 0.5 g/kg TB group of feeding trials and both the 5 mM and 10 mM TB groups of the intestine cell trials, respectively. Subsequently, the injection trials of inhibitors CDX2 and SP1 demonstrated that the inhibition of CDX2 or SP1 decreased the mRNA expression of PepT1. Finally, the results of independent or combined treatments of TB and the inhibitors suggested that CDX2/SP1 mediated TB regulation on PepT1. These findings may help us to better understand the functions of TB on growth and PepT1 oligopeptide transportation, which could be modulated by dietary TB through the CDX2/SP1-PepT1 pathway in juvenile grass carp.

Dietary Supplementation with Eucommia ulmoides Leaf Extract Improved the Intestinal Antioxidant Capacity, Immune Response, and Disease Resistance against Streptococcus agalactiae in Genetically Improved Farmed Tilapia (GIFT; Oreochromis niloticus)

A 7-week rearing trial was designed to investigate the effects of Eucommia ulmoides leaf extract (ELE) on growth performance, body composition, antioxidant capacity, immune response, and disease susceptibility of diet-fed GIFT. The results showed that dietary ELE did not affect growth performance or whole-body composition (p > 0.05). Compared with the control group, plasma ALB contents increased in the 0.06% dietary ELE group (p < 0.05), and plasma ALT and AST activities decreased in the 0.08% dietary ELE group (p < 0.05). In terms of antioxidants, compared with GIFT fed the control diet, 0.06% dietary ELE upregulated the mRNA expression levels of Nrf2 pathway-related antioxidant genes, including CAT and SOD (p < 0.05), and 0.06% and 0.08% dietary ELE upregulated the mRNA levels of Hsp70 (p < 0.05). In terms of immunity, 0.06% dietary ELE suppressed intestinal TLR2, MyD88, and NF-κB mRNA levels (p < 0.05). Moreover, the mRNA levels of the anti-inflammatory cytokines TGF-β and IL-10 were upregulated by supplementation with 0.04% and 0.06% dietary ELE (p < 0.05). In terms of apoptosis, 0.06% and 0.08% ELE significantly downregulated the expression levels of FADD mRNA (p < 0.05). Finally, the challenge experiment with S. agalactiae showed that 0.06% dietary ELE could inhibit bacterial infection, and significantly improve the survival rate of GIFT (p < 0.05). This study demonstrated that the supplementation of 0.04−0.06% ELE in diet could promote intestinal antioxidant capacity, enhance the immune response and ultimately improve the disease resistance of GIFT against Streptococcus agalactiae.

Capsaicin regulates lipid metabolism through modulation of bile acid/gut microbiota metabolism in high-fat-fed SD rats

Capsaicin (CAP) is one of the active ingredients found in chili peppers and has been shown to reduce fat. This study aimed to explore the mechanisms of CAP activity by investigating intestinal microorganisms and bile acids (BAs). This study utilized 16S RNA sequencing to detect gut microbiota in cecal contents, and BAs in Sprague Dawley (SD) rats were also investigated. The results showed that 1) CAP increased the levels of chenodeoxycholic acid (CDCA), deoxycholic acid (DCA), β-muricholic acid (β-MCA), and tauro-β-muricholic acid sodium salt (T-β-MCA), which can regulate farnesoid X receptor (FXR) to inhibit Fgf15, increased CYP7A1 expression to lower triglycerides (TG) and total cholesterol (TC); 2) CAP decreased the abundance of Firmicutes and promoted the presence of specific fermentative bacterial populations, like Akkermansia; meanwhile, less optimal dose can reduce Desulfovibrio; 3) CAP decreased inflammatory factors IL-6 and IL-1β, and increased transient receptor potential channel of vanilloid subtype 1 (TRPV1) to regulate lipid metabolism, fasting plasma glucose and insulin resistance. In conclusion, CAP can reduce fat accumulation by regulating BAs, microorganisms, and short-chain fatty acids.

Effects of replacing fishmeal with methanotroph (Methylococcus capsulatus, Bath) bacteria meal (FeedKind®) on growth and intestinal health status of juvenile largemouth bass (Micropterus salmoides)

A ten-week feeding trial evaluated the feasibility of methanotroph (Methylococcus capsulatus) bacteria meal (FeedKind®, FK) as a fishmeal substitute in largemouth bass (Micropterus salmoides) diets. Six isonitrogenous and isoenergetic diets with different inclusion levels of FK (0 (fishmeal group), 43, 86, 129, 172 and 215 g/kg) were formulated to replace 0, 50, 100, 150, 200 and 250 g/kg fishmeal, respectively. The results showed that FK inclusion level could reach 129 g/kg without significantly affecting growth or feed coefficient rate (P > 0.05), while growth performance was decreased and feed coefficient rate increased when FK inclusion levels exceeded 129 g/kg (P < 0.05). Increase in FK inclusion levels tended to reduce plasma total cholesterol and total triglyceride whilst plasma total protein, albumin, alanine aminotransferase and aspartate aminotransferase in FK treatment groups were unchanged compared with fishmeal group (P > 0.05). FK inclusion levels at 43 g/kg and 86 g/kg were not detrimental to intestinal morphology whilst it was unfavourable when FK inclusion levels exceeded 86 g/kg as the total length of intestinal wall thickness and villus height, villus height were obviously decreased compared with fishmeal group (P < 0.05). As regards to inflammatory cytokine genes, FK instead of fishmeal increased the expression levels of TLR2, RelA, TNF-α, IL-1β, IL-10 and TGF-β, 43 g/kg and 86 g/kg FK decreased the expression level of Caspase-3 (P < 0.05). In conclusion, 129 g/kg FK can replace 150 g/kg fishmeal without negative effects on the growth performance, and replacing 100 g/kg fishmeal with 86 g/kg FK is more beneficial to intestinal health.

Effects of Dietary Tributyrin on Growth Performance, Biochemical Indices, and Intestinal Microbiota of Yellow-Feathered Broilers

This study aimed to evaluate the effects of tributyrin on growth performance, biochemical indices and intestinal microbiota of yellow-feathered broilers. 360 one-day-old chicks were randomly allocated to three treatments with six replicates of 20 chicks each, including a normal control group (NC), an antibiotic group (PC), and a tributyrin (250 mg/kg) group (TB) for 63 days. The results showed that compared with the control, the feed conversion ratio (FCR) in the TB group decreased during the d22 to d42 (p < 0.05) and overall, the final weight and FCR of broilers tended to increase and decrease, respectively. Moreover, the TB group showed the highest creatine concentrations at the entire period (p < 0.05). TB treatment increased the Bacteroidetes relative abundance and decreased Firmicutes. Principal coordinates analysis yielded clear clustering of the three groups. Linear discriminant analysis effect size analysis found seven differentially abundant taxa in the TB group, including several members of Bacteroidedetes. The relative abundance of Eisenbergiella, Phascolarctobacterium, Megasphaera and Intestinimonas increased in tributyrin-treated broilers. Spearman correlation analysis identified a correlation between Eisenbergiella abundance and overall feed efficiency. These results demonstrated that tributyrin could improve the growth performance by modulating blood biochemical indices and the cecal microflora composition of broilers.

Culture salinity modulates Nrf2 antioxidant signaling pathway and immune response of juvenile Genetically Improved Farmed Tilapia (GIFT) (Oreochromis niloticus) under different dietary protein levels

This study aimed to evaluate that dietary protein levels and culture salinity levels affect the health status of juvenile genetically improved farmed tilapia (GIFT, Oreochromis niloticus). Graded protein levels of six diets were prepared, ranging from 18.20% to 49.49% (dry basis), and were used in cultured GIFT at two salinity levels (0‰ and 8‰) for 8 weeks. The results suggested that appropriate protein levels reduced pro-inflammatory gene expressions in the intestine including interleukin 1β (IL-1β), interleukin 8 (IL-8) and tumour necrosis factor-α (TNF-α) mRNA levels at two salinity levels (P < 0.05). 8‰ salinity significantly decreased the expression levels of IL-1β, TNF-α and nuclear factor-kappa B (NF-κB) (P < 0.05). The anti-inflammatory factor interleukin 10 (IL-10) was significantly increased by 36.42% protein level (P < 0.05). Regarding antioxidant capacity, appropriate protein levels and 8‰ salinity significantly improved the antioxidant capacity of fish by regulating the activities of intestinal total superoxide dismutase (T-SOD), glutathione peroxidase (GPx), and the levels of glutathione (GSH) and malondialdehyde (MDA). Furthermore, appropriate protein levels and 8‰ salinity also significantly enhanced the antioxidant gene expressions associated with the Nrf2/keap1 signaling pathway by regulating the expression levels of heme oxygenase-1 (HO-1), GPx, catalase (CAT) and superoxide dismutase (SOD). According to GPx activities and the mRNA levels of IL-10, the optimum dietary protein levels for GIFT juveniles were 31.12%-32.18% (0‰) and 34.25-35.38% (8‰) based on second-degree polynomial regression analysis. The present study found that appropriate protein levels and 8‰ culture salinity are critical in maintaining the health of GIFT juveniles by improving antioxidant and immune capacity.