Protein Restriction with Amino Acid-Balanced Diets Shrinks Circulating Pool Size of Amino Acid by Decreasing Expression of Specific Transporters in the Small Intestine

Chenodeoxycholic Acid Improves Embryo Implantation and Metabolic Health through Modulating Gut Microbiota-Host Metabolites Interaction during Early Pregnancy

Fetus loss in early pregnancy is of major concern to both humans and animals, and this issue is largely influenced by embryo implantation. Chenodeoxycholic acid (CDCA), a primary bile acid, contributes to metabolic improvements and protects against intrahepatic cholestasis of pregnancy. However, the effect of CDCA on embryo implantation during early pregnancy has not been investigated. The present study demonstrated that CDCA administration during early pregnancy improved embryo implantation in sows and rats, thereby improving the pregnancy outcomes of sows. CDCA significantly reduced inflammation, oxidative stress, and insulin resistance. The metabolomics analysis indicated significant differences in the fecal metabolome, especially regarding the level of secondary bile acids, between the control and CDCA-treated sows. CDCA also influenced the serum metabolite profiles in sows, and the serum L-Histidine level was significantly correlated with the abundance of 19 differential fecal metabolites. Importantly, L-Histidine administration improved embryo implantation and metabolic health in rats during early pregnancy. Moreover, CDCA administration during early pregnancy also led to long-term metabolic improvements in sows. Our data indicated that CDCA improved embryo implantation by alleviating inflammation and oxidative stress, improving insulin sensitivity, and modulating the interaction between the gut microbiota and host metabolites. Therefore, CDCA intervention is a potential therapeutic strategy regarding embryo loss during pregnancy.

Comparison of the Effects of Feeding Compound Probiotics and Antibiotics on Growth Performance, Gut Microbiota, and Small Intestine Morphology in Yellow-Feather Broilers

This study was devoted to the comparison of the probiotic effect of compound probiotics to antibiotics as a feed additive for chicken. Two hundred and seventy newly hatched yellow-feather broilers were randomly divided into three groups: the control group (Con), probiotics (Pb), and antibiotics group (Ab). The Pb group received compound probiotics (Bifidobacterium, Lactobacillus acidophilus, Streptococcus faecalis, and yeast) via drinking water for 24 days. The Ab group received antibiotics (zinc bacitracin and colistin sulfate) in their diet for 24 days. All broilers were slaughtered on day 42. Compared with the Con group, the body weight was significantly increased on days 13, 28, and 42 in the Pb group (p < 0.05), and markedly increased on day 28 in the Ab group (p < 0.05). Compared with the Ab group, the body weight of the broilers in the Pb group increased significantly on day 13 (p < 0.05). Compared to the Con and Pb groups, the antibiotics treatment reduced the feed intake (p < 0.05), but there was no significant difference in the feed conversion ratio between the Ab and Pb groups (p > 0.05). The feed conversion ratio of the broilers treated with antibiotics or probiotics significantly decreased compared to the Con group (p < 0.05). The depth of duodenum, jejunum, and ileum crypts in the Pb group decreased significantly compared to the Con and Ab group (p < 0.05). The ratio of the villi length to crypt depth of duodenum, jejunum, and ileum epithelium was significantly increased in the Pb group compared to the Con group (p < 0.05). The genera Bacteroides and Barnesiella were the most significantly enriched bacteria in the Ab and Pb groups, respectively (p < 0.05). The expression of the genes related to antibiotic resistance was significantly decreased in the Pb group compared to the Ab group (p < 0.05). Although both compound probiotics and antibiotics can improve growth performance, antibiotics increased the abundance of harmful bacteria and drug-resistant genes, while probiotics increased Barnesiella abundance, which is related to a decrease in the drug-resistant gene expression. Moreover, the probiotics treatment improved small intestinal morphology and fecal emissions, while antibiotics have no significant effect on these indicators, indicating a bright future for probiotics as an alternative to feed antibiotics in the yellow-feather broiler industry.

The optimal dietary arginine level of laying hens fed with low-protein diets

Background

Arginine (Arg) is an essential amino acid (EAA) in poultry, an important substrate for protein synthesis and a precursor of several molecules. Supplementation of EAAs with low protein (LP) diet increases the utilization efficiency of dietary crude protein (CP). However, if the EAA requirement is changed in hens fed a LP diet remains to be elucidated. The aim of the present study was to evaluate the optimal level of dietary Arg in the LP diet of hens. A total of 1350 Hy-Line Brown laying hens were randomly allocated to six dietary treatments: a basal diet (16% CP, positive control), or an isoenergetic LP diet (14% CP, 0.80% Arg) supplemented 0, 0.05%, 0.10%, 0.15%, and 0.20% L-Arg, corresponding to 0.80%, 0.85%, 0.90%, 0.95% and 1.00% dietary Arg, respectively.

Results

The feed efficiency was decreased (P < 0.05) by 0.80% and 1.00% Arg-LP diets, compared to control. Within LP diets, dietary Arg level had significant quadratic effects (P < 0.05) on laying rate, egg mass, and feed efficiency. Compared to control, the plasma CAT activity or T-AOC content were decreased by 0.80% (P < 0.001). However, the hens offered 0.85% and 0.90% Arg-LP diets had higher CAT activity (P < 0.001) than 0.80% Arg-LP diet. In contrast, 1.00% Arg-LP group had the highest MDA and the lowest T-AOC content in plasma, liver, duodenal and jejunal mucosa (P < 0.05). Compared to control, the villus height was decreased by 0.80%, 0.95% and 1.00% Arg-LP diets, while the villus height to crypt depth (V/C) ratio was reduced by 0.95% and 1.00% Arg-LP diets in duodenum.

Conclusion

The result demonstrates that LP diet (14% CP) deficient in Arg (0.80% Arg) result in augmented oxidative damage and impaired development of intestinal mucosa. According to the quadratic broken-line regression model, the optimal dietary arginine levels for Hy-Line Brown laying hens fed with low protein diet (14% CP) aged 33 to 40 weeks are 0.85%, 0.86%, and 0.86% to obtained the maximum laying rate, egg mass, and feed efficiency, respectively.

Supplementary Information

The online version contains supplementary material available at 10.1186/s40104-022-00719-x.

Modifying dietary amino acids in cancer patients

Limiting nutrient utilization by cancer cells in order to disrupt their metabolism and suppress their growth represents a promising approach for anti-cancer therapy. Recently, studies demonstrating the anti-neoplastic effects of lowering amino acid (AA) availability have opened up an exciting and quickly growing field of study. Although intracellular synthesis can often provide the AAs necessary to support cancer cells, diet and the tumor microenvironment can also be important sources. In fact, studies carried out in vitro and in animal tumor models have supported the anti-cancer potential of restricting exogenous sources of AAs. However the potential benefit of reducing AA intake in cancer patients requires further investigation. Furthermore, implementation of such an approach clinically, even if proven useful, could be challenging. In the enclosed review, we (1) summarize the pre-clinical studies showing the anti-tumorigenic effects of restricting exogenously available AAs, including through reducing dietary protein, (2) consider the role of microbiota in this process, (3) report on current recommendations for protein intake in cancer patients and studies that applied these guidelines, and (4) propose considerations for studies to test the potential therapeutic benefit of reducing protein/AA consumption in patients with cancer.

Effects of Dietary Supplementation With Bacillus subtilis, as an Alternative to Antibiotics, on Growth Performance, Serum Immunity, and Intestinal Health in Broiler Chickens

Bacillus subtilis (B. subtilis) as in-feed probiotics is a potential alternative for antibiotic growth promoters (AGP) in the poultry industry. The current study investigated the effects of B. subtilis on the performance, immunity, gut microbiota, and intestinal barrier function of broiler chickens. A 42-day feeding trial was conducted with a total of 600 1-day-old Arbor Acres broilers with similar initial body weight, which was randomly divided into one of five dietary treatments: the basal diet (Ctrl), Ctrl + virginiamycin (AGP), Ctrl + B. subtilis A (BSA), Ctrl + B. subtilis B (BSB), and Ctrl + B. subtilis A + B (1:1, BSAB). The results showed significantly increased average daily gain in a step-wise manner from the control, B. subtilis, and to the AGP groups. The mortality rate of the B. subtilis group was significantly lower than the AGP group. The concentrations of serum immunoglobulin (Ig) G (IgG), IgA, and IgM in the B. subtilis and AGP groups were higher than the control group, and the B. subtilis groups had the highest content of serum lysozyme and relative weight of thymus. Dietary B. subtilis increased the relative length of ileum and the relative weight of jejunum compared with the AGP group. The villus height (V), crypt depth (C), V/C, and intestinal wall thickness of the jejunum in the B. subtilis and AGP groups were increased relative to the control group. Dietary B. subtilis increased the messenger RNA (mRNA) expression of ZO-1, Occludin, and Claudin-1, the same as AGP. The contents of lactic acid, succinic acid, and butyric acid in the ileum and cecum were increased by dietary B. subtilis. Dietary B. subtilis significantly increased the lactobacillus and bifidobacteria in the ileum and cecum and decreased the coliforms and Clostridium perfringens in the cecum. The improved performance and decreased mortality rate observed in the feeding trial could be accrued to the positive effects of B. subtilis on the immune response capacity, gut health, and gut microflora balance, and the combination of two strains showed additional benefits on the intestinal morphology and tight junction protein expressions. Therefore, it can be concluded that dietary B. subtilis A and B could be used as alternatives to synthetic antibiotics in the promotion of gut health and productivity index in broiler production.

Effects of Dietary Selenium Sources on Physiological Status of Laying Hens and Production of Selenium-Enriched Eggs

Developing new sources of organic selenium (Se) has potential benefits for animal production and human nutrition via animal-based foods enriched with Se. The objective of this study was to evaluate the effects of Se-enriched insect protein (SEIP) in comparison with other sources, such as sodium selenite (SS) and selenium-enriched yeast (SEY), on performance, egg quality, selenium concentration in eggs, serum biochemical indices, immune capacity, and intestinal morphology of laying hens. Four hundred and fifty 24-week-old Hy-Line Brown laying hens with 94.0 ± 1.5% laying rate were randomly allocated to five groups with six replicates of 15 hens each. The control diet was prepared without adding exogenous selenium (calculated basal Se content of 0.08 mg/kg). The normal group was fed basal diets supplemented with 0.3 mg/kg of Se provided by sodium selenite. Three treatment groups (SS, SEY, and SEIP, respectively) were fed basal diets supplemented with 2 mg/kg of Se provided by sodium selenite, Se-enriched yeast, and SEIP, respectively. The feeding trial lasted for 12 weeks. Results revealed that dietary supplementation of 2 mg/kg of Se increased egg weight, decreased feed conversion ratio, and enhanced the antioxidant capacity of eggs in laying hens relative to the control group, whereas no significant differences were observed among SS, SEY, and SEIP treatment groups for the same. The organic source of Se provided by SEY or SEIP showed higher bio efficiency, as indicated by higher selenium content in eggs of SEY and SEIP compared with SS, although higher content was observed in SEY compared with SEIP. Also, the organic Se source significantly improved antioxidant capacity and immune functions of laying hens than the inorganic Se source. Diets supplemented with SEIP and SS significantly improved jejunal morphology of the laying hens compared with SEY, whereas SEIP was more effective than SEY to improve the oviduct health of laying hens. The results of this work evidently points the additive effect and nontoxicity of SEIP. Thus, SEIP could be used as another organic source of Se in the diet of laying hens and production of selenium-enriched eggs for humans.

Implications of excreta uric acid concentrations in broilers offered reduced-crude protein diets and dietary glycine requirements for uric acid synthesis

In a previous experiment, male Ross 308 broiler chickens were offered dietary treatments with 3 levels of crude protein (222, 193, 165 g/kg) and 3 feed grains (ground maize, ground wheat, whole wheat) from 7 to 35 d post-hatch. Maize-based diets supported superior growth performance in comparison to wheat-based diets. Uric acid concentrations in excreta were retrospectively determined and related to total nitrogen (N) excreta concentrations. Uric acid concentrations ranged from 28.5 to 69.4 mg/g and proportions of uric acid-N to total excreta-N ranged from 27.4% to 42.6% in broiler chickens offered the 3 × 3 factorial array of dietary treatments. Proportions of uric acid-N to total N in excreta in birds offered the 165 g/kg CP, maize-based diet were significantly lower by 10.6 percentage units (27.4% versus 38.0%; P = 0.00057) than their wheat-based counterparts. Total excreta analysed had been collected from 35 to 37 d post-hatch when feed intakes and excreta outputs were monitored. There were linear relationships between proportions of uric acid-N to total N in excreta in birds offered the three 165 g/kg CP diets with weight gain (r = -0.587; P = 0.010), feed intake (r = -0.526; P = 0.025) and feed conversion ratios (r = 0.635; P = 0.005). The possibility that increasing uric acid-N proportions in excreta is indicative of excessive ammonia accumulations compromising growth performance is discussed. The mean proportion of dietary glycine involved in uric acid excretion was 49.2% across all dietary treatments but ranged from 25.0% to 80.9%. Thus, the appropriate amount of dietary glycine is variable and largely dependent on the volume of uric acid synthesised and excreted.

Arginine promotes myogenic differentiation and myotube formation through the elevation of cytoplasmic calcium concentration

This study aimed to explore the mechanism underlying arginine-promoted myogenesis of myoblasts. C2C12 cells were cultured with a medium containing 0.1, 0.4, 0.8, or 1.2 mmol/L arginine, respectively. Cell proliferation, viability, differentiation indexes, cytoplasmic Ca²⁺ concentration, and relative mRNA expression levels of myogenic regulatory factors (MRF) and key Ca²⁺ channels were measured in the absence or presence of 2 chemical inhibitors, dantrolene (DAN, 10 μmol/L) and nisoldipine (NIS, 10 μmol/L), respectively. Results demonstrated that arginine promoted myogenic differentiation and myotube formation. Compared with the control (0.4 mmol/L arginine), 1.2 mmol/L arginine upregulated the relative mRNA expression levels of myogenin (MyoG) and Myomaker at d 2 during myogenic induction (P < 0.05). Cytoplasmic Ca²⁺ concentrations were significantly elevated by arginine supplementation at d 2 and 4 (P < 0.05). Relative mRNA expression levels of Ca²⁺ channels including the type 1 ryanodine receptor (RyR1) and voltage-gated Ca²⁺ channel (Cav1.1) were upregulated by 1.2 mmol/L arginine during 2-d myogenic induction (P < 0.01). However, arginine-promoted myogenic potential of myoblasts was remarkably compromised by DAN and NIS, respectively (P < 0.05). These findings evidenced that the supplementation of arginine promoted myogenic differentiation and myotube formation through increasing cytoplasmic Ca²⁺ concentration from both extracellular and sarcoplasmic reticulum Ca²⁺.

The Dynamic Conversion of Dietary Protein and Amino Acids into Chicken-Meat Protein

This review considers the conversion of dietary protein and amino acids into chicken-meat protein and seeks to identify strategies whereby this transition may be enhanced. Viable alternatives to soybean meal would be advantageous but the increasing availability of non-bound amino acids is providing the opportunity to develop reduced-crude protein (CP) diets, to promote the sustainability of the chicken-meat industry and is the focus of this review. Digestion of protein and intestinal uptakes of amino acids is critical to broiler growth performance. However, the transition of amino acids across enterocytes of the gut mucosa is complicated by their entry into either anabolic or catabolic pathways, which reduces their post-enteral availability. Both amino acids and glucose are catabolised in enterocytes to meet the energy needs of the gut. Therefore, starch and protein digestive dynamics and the possible manipulation of this 'catabolic ratio' assume importance. Finally, net deposition of protein in skeletal muscle is governed by the synchronised availability of amino acids and glucose at sites of protein deposition. There is a real need for more fundamental and applied research targeting areas where our knowledge is lacking relative to other animal species to enhance the conversion of dietary protein and amino acids into chicken-meat protein.

Effect of Dietary Tryptophan on Growth, Intestinal Microbiota, and Intestinal Gene Expression in an Improved Triploid Crucian Carp

Tryptophan (Trp) has received increasing attention in the maintenance of intestinal function. In this study, improved triploid crucian carp (ITCC) fed diets containing 6.35 g kg⁻¹ Trp had higher average daily gain (ADG) and improved villus height (VH) and crypt depth (CD) in the intestine compared to the control group. To elucidate the potential mechanisms, we used RNA sequencing (RNA-seq) to investigate changes in the intestinal transcriptome and 16S rRNA gene sequencing to measure the intestinal microbiota in response to 6.35 g kg⁻¹ Trp feeding in ITCC. Dietary Trp altered intestinal gene expression involved in nutrient transport and metabolism. Differentially expressed transcripts (DETs) were highly enriched in key pathways containing protein digestion and absorption and the AMPK signaling pathway. 16S rRNA sequencing showed that 6.35 g kg⁻¹ Trp significantly increased the abundance of the genus Cetobacterium, and the Firmicutes/Bacteroidetes ratio at the phylum level (P < 0.05). In addition, bacterial richness indices (Simpson index) significantly increased (P < 0.05) community evenness in response to 6.35 g kg⁻¹ Trp. In conclusion, appropriate dietary Trp improves the growth performance, and influences the intestinal flora of ITCC. This study might be helpful to guide the supply of dietary exogenous Trp in ITCC breeding.

Application of Selenium Conjugated to Animal Protein in Laying Hens' Diet for the Production of Selenium-Enriched Eggs

The current experiment was conducted to investigate the application effects of selenium conjugated to insect protein (SCIP) in the production of selenium-enriched eggs. A total of 450 laying hens were randomly assigned to five dietary groups, each group consisting of six replicates. Hens in the control group received a diet without selenium supplementation, whereas hens in the other four groups received diets supplemented with either 1, 2, 5, or 10 mg/kg of selenium from SCIP. The productive performance, egg quality, antioxidant and immune capacity, biochemical indices, intestinal morphology, and oviduct health of laying hens were evaluated. The results showed that the supplementation of organic selenium provided by SCIP in the diets of laying hens enhanced performance and egg quality without any toxicity effect, even at the 10 mg/kg inclusion level. A level of 2 mg/kg of selenium provided by SCIP in diets tentatively improved the serum antioxidant and immune capacity, intestinal development, and oviduct health of laying hens in a conspicuous manner. Hence, the biosafety and positive effects of SCIP as a feed additive supplement in laying hens' diet have been demonstrated with the enhanced production of safe and selenium-enriched eggs.

Plasma and Urinary Amino Acid-Derived Catabolites as Potential Biomarkers of Protein and Amino Acid Deficiency in Rats

OBJECTIVE

Dietary intakes must cover protein and essential amino acid (EAA) requirements. For this purpose, different methods have been developed such as the nitrogen balance method, factorial method, or AA tracer studies. However, these methods are either invasive or imprecise, and the Food and Agriculture Organization of the United Nations (FAO, 2013) recommends new methods and, in particular, metabolomics. The aim of this study is to determine total protein/EAA requirement in the plasma and urine of growing rats.

METHODS

36 weanling rats were fed with diets containing 3, 5, 8, 12, 15, and 20% protein for 3 weeks. During experimentation, urine was collected using metabolic cages, and blood from the portal vein and vena was taken at the end of the experiment. Metabolomics analyses were performed using LC-MS, and the data were analyzed with a multivariate analysis model, partial least Squares (PLS) regression, and independent component-discriminant analysis (ICDA). Each discriminant metabolite identified by PLS or ICDA was tested by one-way ANOVA to evaluate the effect of diet.

RESULTS

PLS and ICDA allowed us to identify discriminating metabolites between different diet groups. Protein deficiency led to an increase in the AA catabolism enzyme systems inducing the production of breakdown metabolites in the plasma and urine.

CONCLUSION

These results indicate that metabolites are specific for the state of EAA deficiency and sufficiency. Some types of biomarkers such as AA degradation metabolites appear to be specific candidates for protein/EAA requirement.

Use of encapsulated L-lysine-HCl and DL-methionine improves postprandial amino acid balance in laying hens

The supplementation of dietary limiting amino acids (AA) with crystalline AA makes the use of low-protein diets an option in poultry production. The differing absorption rates of crystalline and protein-bound AA may lead to temporally imbalanced AA in the postabsorptive period. In this study, two experiments were conducted to evaluate the effect of encapsulated L-lysine-HCl (L-Lys-HCl) and DL-methionine (DL-Met) on the laying performance of hens. In exp. 1, a total of 135 forty-seven-wk-old Hy-Line Brown hens were subjected to three dietary treatments for 8 wk: basal diet supplemented with 0.14% L-Lys-HCl and 0.17% DL-Met to satisfy the NRC (1994) total Lys and Met recommendation (control) and basal diet supplemented with encapsulated L-Lys-HCl and DL-Met at the levels of 60% (60CLM, 0.084% L-Lys-HCl and 0.102% DL-Met) or 80% of control (80CLM, 0.112% L-Lys-HCl and 0.136% DL-Met), respectively. In exp. 2, 24 fifty-five-wk-old Hy-Line Brown hens were individually reared in cages and subjected to the same treatments as in exp. 1. The plasma concentrations of free AA and nitrogen metabolites were measured 2, 4, and 6 h after fed. The results showed that dietary AA treatment had no significant influence on body weight (BW), feed intake, laying rate, egg weight, egg mass, or feed efficiency. The expression levels of AA transporters CAT-1, y+LAT1, b0,+AT, B0AT, rBAT, EAAT3, and PepT1 in the duodenum, jejunum, and ileum were not influenced (P > 0.05) by dietary treatment. There was an interaction of dietary AA treatment and time (P < 0.05) and the 80CLM hens exhibited higher concentrations of Lys (P < 0.05) than the controls at 2-h time point. In contrast, plasma Met concentration was not influenced (P > 0.05), while Cys was reduced in the 60CLM hens at every time point. The 80CLM hens had higher taurine concentrations than those receiving the control diet at every postprandial time point. In conclusion, these findings demonstrate that by using encapsulated form, the supplemental levels of synthetic L-Lys-HCl and DL-Met can be effectively reduced by approximately 20% with no negative effect on laying performance. The result suggests that encapsulated Lys and Met may ameliorate the postabsorptive AA balance and contribute to the reduced dietary AA supplemental levels.

Impact of reduced dietary crude protein levels and phytase enzyme supplementation on growth response, slurry characteristics, and gas emissions of growing pigs

This experiment was carried out to evaluate the effect of reduced dietary crude protein (CP) levels supplemented with or without exogenous phytase on growing pigs. Six dietary treatments arranged in a 3 × 2 factorial arrangements of 3 CP levels (containing 14%, 16%, and 18% CP) supplemented each with or without 5,000 FTU/g phytase enzyme. Thirty growing pigs (average weight of 17.80 ± 0.10 kg) were allotted to the six dietary treatments in a complete randomized design. The final weight, daily weight gain, and feed conversion ratio (FCR) increased significantly with increasing CP levels. While, phytase supplementation improved (p = .044) FCR in pigs. Total solid and volatile solid content of the slurry were higher (p = .001) in pigs fed 14% and 16% CP diets supplemented with phytase when compared with other treatment groups. Concentration of methane gas emitted was lowest (p = .001) in the slurry of pigs fed 14% CP diet with or without phytase and those fed 16% CP diet with phytase supplementation. In conclusion, reduction in dietary CP levels resulted in reduced weight gain and poor FCR. While, reduced CP with phytase supplementation reduced concentration of methane gas emitted.

Encapsulated crystalline lysine and DL-methionine have higher efficiency than the crystalline form in broilers

Crystalline amino acids (AAs) exhibit high nutritional values when supplemented AA-deficient diets. However, the AAs in crystalline form in the diet are absorbed quickly than protein-bound AAs, which may take an effect on AA utilization efficiency. In this study, 2 experiments were conducted to investigate the effect of encapsulated lysine-HCl (Lys) and DL-methionine (DL-Met) on the growth performance of broiler chickens. In experiment 1, a total of 432 one-day-old male Arbor Acres broilers were subjected to 3 dietary treatments (27 pens; 16 birds per pen) for 42 d. The control group was basal diets supplemented with crystalline Lys and DL-Met, and treatment groups had basal diets supplemented with encapsulated Lys and DL-Met at the levels of 80% and 60% of control diets (80CLM, 60CLM), respectively. The growth performance, intestinal development, and transcription of AA transporters were determined. In experiment 2, 24 broiler chickens were subjected to the same treatments as in experiment 1. The plasma concentrations of free AAs were measured 0, 2, 4, and 6 h after feeding. The results showed that 80CLM treatment had no significant influence on production performance, carcass characteristics, and plasma free AAs content during the experiment compared with the control group (P > 0.05). In addition, the 80CLM group moderately enhanced gut morphology development and increased AAs' absorption capacity. However, broilers fed the 60CLM diet had lower production performance and breast muscle weight than the control group (P < 0.05), but increased villi height and B⁰AT mRNA expression level (P < 0.05). At h 4 after feeding, the 60CLM broilers exhibited higher concentration of Ala, Cys, and total dispensable AAs than the control group (P < 0.05). In conclusion, the result suggests that the supplemental levels of crystalline Lys and DL-Met can be effectively saved approximately for 20% by using the encapsulated form in broilers, with improvements to AAs utilization efficiency, while posing no detrimental effects on production performance. Encapsulated Lys and DL-Met would have greater potential for application when replacing crystalline AAs in broiler chickens.

Long-term effect of early antibiotic exposure on amino acid profiles and gene expression of transporters and receptors in the small intestinal mucosa of growing pigs with different dietary protein levels

BACKGROUND

This study evaluated the effects of early antibiotic exposure (EAE) on subsequent amino acid (AA) profiles and small intestinal AA transporter and receptor expression level in pigs with different dietary crude protein (CP) levels. Eighteen litters of piglets were fed creep feed diets, either with or without antibiotics while with sow on day 7. The pigs were weaned at day 23 and fed the same diets until day 42, when random pigs within each group were offered a normal- or low-CP diet, thereby creating four groups. On day 120, the pigs were euthanized, and jejunal and ileal mucosa and digesta were collected for gene-expression and AA-concentration analysis.

RESULTS

With the normal-CP diet, EAE increased (P < 0.05) the concentrations of six essential amino acids (EAA) and three non-essential amino acids (NEAA) in serum, four EAAs and four NEAAs in jejunal mucosa, one EAA and two NEAAs in ileal mucosa, five EAAs and three NEAAs in jejunal digesta, and three EAAs and two NEAAs in ileal digesta. Early antibiotic exposure upregulated (P < 0.05) CAT1, ASCT2, ATB^0,+ , CaSR, T1R1, and T1R3 expression in the jejunum, downregulated PepT1 expression with a normal-CP diet. It upregulated (P < 0.05) the expressions of CAT1, ATB^0,+ , ATP1A1, and T1R3 in the ileum with a normal-CP diet.

CONCLUSION

These results suggest that EAE has long-term effects on AA profiles, mainly in the jejunum and serum, by increasing AA transporter expression in the intestine, and that these effects may be influenced by dietary CP levels. © 2019 Society of Chemical Industry.

The involvement of NF-κB/P38 pathways in Scutellaria baicalensis extracts attenuating of Escherichia coli K88-induced acute intestinal injury in weaned piglets

The present study was carried out to evaluate the effect of dietary supplementation of Scutellaria baicalensis extracts (SBE) on intestinal health in terms of morphology, barrier integrity and immune responses in weaned piglets challenged with Escherichia coli K88. A total of seventy-two weaned piglets were assigned into two groups to receive a basal diet without including antibiotic additives or the basal diet supplemented 1000 mg SBE/kg diet for 14 d. On day 15, twelve healthy piglets from each group were selected to expose to oral administration of either 10 ml 1 × 109 colony-forming units of E. coli K88 or the vehicle control. After 48 h of E.coli K88 challenge, blood was sampled, and then all piglets were killed humanely for harvesting jejunal and ileal samples. Dietary supplementation of SBE significantly decreased diarrhoea frequency and improved feed conversion ratio (P < 0·05). SBE supplementation to E.coli K88-challenged piglets improved villous height and villous height/crypt depth (P < 0·05), recovered the protein expression of occludin and zonula occludens-2 in both the jejunum and ileum (P < 0·05), and mitigated the increases in plasma IL-1β, TNF-α, IL-6, IgA and IgG (P < 0·05). Meanwhile, dietary SBE effectively inhibited the stimulation of NF-κB, P38 and TNF-α as well as IL-1β in the small intestine of piglets challenged by E. coli K88 and prevented the activation of NF-κB/P38 signalling pathways (P < 0·05). Collectively, SBE supplementation can potently attenuate diarrhoea in weaning piglets and decrease inflammatory cytokine expressions through inhibiting the NF-κB and P38 signalling pathways.

Surplus dietary isoleucine intake enhanced monounsaturated fatty acid synthesis and fat accumulation in skeletal muscle of finishing pigs

Background

Isoleucine (Ile) has been implicated in the regulation of energy homeostasis and adipogenesis. However, the impact of surplus dietary Ile intake on muscle lipogenesis remains unknown. The present study aimed to investigate the impact of dietary supplementation of extra-Ile on lipogenesis, fatty acid profile and lipid accumulation in skeletal muscle in finishing pigs.

Methods

Forty-eight barrows with initial body weight of 77.0 ± 0.1 kg were allotted to one of two groups and fed diets containing 0.39%, 0.53% standardized ileal digestible (SID) Ile with six replicates per treatment and four pigs per replicate for 30 d.

Results

Dietary Ile intake significantly improved the intramuscular fat (IMF) content and monounsaturated fatty acid (MUFA) concentration in the skeletal muscle (P < 0.05), and decreased the drip loss and shear force (P < 0.05) without influencing the growth performance of pigs (P > 0.05). Moreover, the phosphorylation of adenosine monophosphate activated protein kinase α (AMPKα) and acetyl coenzyme A carboxylase (ACC) proteins that monitor lipid metabolism were decreased in skeletal muscle of pigs offered extra-Ile diet (P < 0.05). The mRNA expression of adipose-specific genes adipocyte determination and differentiation factor 1 (ADD1), fatty acid synthase (FAS), and stearoyl-CoA desaturase (SCD) were upregulated and the activity of SCD was increased as well (P < 0.05).

Conclusions

Surplus dietary Ile intake could increase IMF accumulation and MUFA synthesis in skeletal muscle through depressing the phosphorylation of AMPKα-ACC and stimulating the expression and activity of SCD, and increasing the capability of lipogenesis in skeletal muscle.

Electronic supplementary material

The online version of this article (10.1186/s40104-018-0306-5) contains supplementary material, which is available to authorized users.

Intestinal IMINO transporter SIT1 is not expressed in human newborns

The expression of amino acid transporters in small intestine epithelia of human newborns has not been studied yet. It is further not known whether the maturation of imino acid (proline) transport is delayed as in the kidney proximal tubule. The possibility to obtain small intestinal tissue from patients undergoing surgery for jejunal or ileal atresia during their first days after birth was used to address these questions. As control, adult terminal ileum tissue was sampled during routine endoscopies. Gene expression of luminal imino and amino acid transporter SIT1 (SLC6A20) was approximately threefold lower in newborns versus adults. mRNA levels of all other luminal and basolateral amino acid transporters and accessory proteins tested were similar in newborn mucosa compared with adults. At the protein level, the major luminal neutral amino acid transporter B⁰AT1 (SLC6A19) and its accessory protein angiotensin-converting enzyme 2 were shown by immunofluorescence to be expressed similarly in newborns and in adults. SIT1 protein was not detectable in the small intestine of human newborns, in contrast to adults. The morphology of newborn intestinal mucosa proximal and distal to the obstruction was generally normal, but a decreased proliferation rate was visualized distally of the atresia by lower levels of the mitosis marker K_i-67. The mRNA level of the 13 tested amino acid transporters and accessory proteins was nonetheless similar, suggesting that the intestinal obstruction and interruption of amniotic fluid passage through the small intestinal lumen did not affect amino acid transporter expression. NEW & NOTEWORTHY System IMINO transporter SIT1 is not expressed in the small intestine of human newborns. This new finding resembles the situation in the proximal kidney tubule leading to iminoglycinuria. Lack of amniotic fluid passage in small intestinal atresia does not affect amino acid transporter expression distal to intestinal occlusion.

Integrated Remodeling of Gut-Liver Metabolism Induced by Moderate Protein Restriction Contributes to Improvement of Insulin Sensitivity

SCOPE

Protein restriction (PR) is beneficial for relieving metabolic disorders and aging-related diseases. However, extreme PR could result in malnutrition due to severe deficiency of essential amino acids. Therefore, the effect of moderate PR on insulin sensitivity is investigated.

METHODS AND RESULTS

The growing and adult pigs are subjected to moderate PR by 15-30%. Plasma insulin concentration and insulin resistance index HOMA-IR are significantly decreased upon moderate PR. Furthermore, IRS1/PI3K/AKT pathway in the basal state is enhanced in both liver and skeletal muscle. The adapted metabolism in the liver upon moderate PR is in support of improving insulin sensitivity. The liver shares a coordinated metabolic adaption in terms of energy metabolism and amino acid metabolism with the small intestine. Particularly, alteration of the metabolic footprint appeared in the portal venous blood, representing metabolites to be absorbed into liver after intestinal metabolism, is also in favor of improvement of insulin sensitivity.

CONCLUSION

In summary, the study proves that moderate PR could improve insulin sensitivity from childhood to adulthood in a pig model, and sheds a new light on the role of integrated remodeling of gut and liver metabolism in the improved insulin sensitivity induced by moderate PR.

Regulation profile of the intestinal peptide transporter 1 (PepT1)

The intestinal peptide transporter 1 (PepT1) was first identified in 1994. It plays a crucial role in the absorption of small peptides including not only >400 different dipeptides and 8,000 tripeptides digested from dietary proteins but also a repertoire of structurally related compounds and drugs. Owing to its critical role in the bioavailability of peptide-like drugs, such as the anti-cancer agents and anti-virus drug, PepT1 is increasingly becoming a striking prodrug-designing target. Therefore, the understanding of PepT1 gene regulation is of great importance both for dietary adaptation and for clinical drug treatment. After decades of research, it has been recognized that PepT1 could be regulated at the transcriptional and post-transcriptional levels by numerous factors. Therefore, the present review intends to summarize the progress made in the regulation of PepT1 and provide insights into the PepT1's potential in clinical aspects of nutritional and drug therapies.