Dietary leucine supplementation improves intestinal health of mice through intestinal SIgA secretion

Maternal resveratrol improves the intestinal health and weight gain of suckling piglets during high summer temperatures: The involvement of exosome-derived microRNAs and immunoglobin in colostrum

Previous studies have shown that maternal resveratrol improved growth performance and altered the microbial composition of suckling piglets under hot summer conditions. However, it remains unclear how maternal resveratrol improves growth performance of suckling piglets during high summer temperatures. A total of 20 sows (Landrace × Large White; three parity) were randomly assigned to 2 groups (with or without 300 mg/kg resveratrol) from d 75 of gestation to d 21 of lactation during high ambient temperatures (from 27 to 30 °C). The results showed that maternal resveratrol supplementation increased total daily weight gain of piglets under hot summer conditions, which is consistent with previous studies. Furthermore, we found that maternal resveratrol improved the intestinal morphology and intestinal epithelial proliferation in suckling piglets. Dietary resveratrol supplementation affected the characteristics of exosome-derived microRNAs (miRNAs) in sow colostrum, as well as the genes targeted by differentially produced miRNAs. MiRNAs are concentrated in the tight junction pathway. As a result, the expression of intestinal tight junction proteins was increased in suckling piglets (P < 0.05). Notably, maternal resveratrol increased the intestinal secretory immunoglobulin A (sIgA) levels of suckling piglets via colostrum immunoglobin (P < 0.05), which could increase the abundance of beneficial microbiota to further increase the concentration of short chain fatty acids (SCFA) in suckling piglets' intestine (P < 0.05). Finally, our correlation analysis further demonstrated the positive associations between significantly differential intestinal microbiota, intestinal sIgA production and SCFA concentrations, as well as the positive relation between total daily weight gain and intestinal health of suckling piglets. Taken together, our findings suggested that maternal resveratrol could promote intestinal health to improve piglet growth during high summer temperatures, which might be associated with the immunoglobin and exosome-derived miRNAs in sows' colostrum.

Exploring the therapeutic potential of porphyran extracted from Porphyra haitanensis in the attenuation of DSS-induced intestinal inflammation

Ulcerative colitis is a chronic, spontaneous inflammatory bowel disease that primarily affects the colon. This study aimed to explore how Porphyra haitanensis porphyran (PHP) modulates the immune response and the associated mechanisms that alleviate dextran sulphate sodium-induced colitis in mice. Histological assessments via H&E staining and AB-PAS staining revealed that PHP intervention partially restored the number of goblet cells and improved intestinal mucosal function. Immunohistochemical and Western blot analyses of claudin-1, occludin, and MUC-2 demonstrated that PHP could repair the intestinal barrier and reduce colon damage by upregulating the expression of these proteins. PHP intervention was associated with a decrease in pro-inflammatory cytokine expression and an increase in anti-inflammatory cytokine expression. Moreover, the expression of proteins involved in intestinal immune homing, such as CCR-9, CCL-25, MAdCAM-1, and α4β7, was significantly suppressed in response to PHP treatment. Conversely, PHP upregulates the expression of CD40 and TGF-β1, both of these can promote healing and reduce inflammation in the gut lining. This study demonstrates that PHP can ameliorate ulcerative colitis by enhancing the intestinal barrier and modulating immune responses. These findings offer valuable insights into the potential utility of P. haitanensis as a promising natural product for managing ulcerative colitis.

Multiomics Analysis Reveals Leucine Deprivation Promotes Bile Acid Synthesis by Upregulating Hepatic CYP7A1 and Intestinal Turicibacter sanguinis in Mice

BACKGROUND

Leucine, a branched-chain amino acid, participates in the regulation of lipid metabolism and the composition of the intestinal microbiota. However, the related mechanism remains unclear.

OBJECTIVES

Here, we aimed to reveal the potential mechanisms by which hepatic CYP7A1 (a rate-limiting enzyme for bile acid [BA] synthesis) and gut microbiota coregulate BA synthesis under leucine deprivation.

METHODS

To this end, 8-wk-old C57BL/6J mice were fed with either unpurified diets or leucine-free diets for 1 wk. Then, we investigated whether secondary BAs were synthesized by Turicibacter sanguinis in 7-wk-old C57BL/6J germ-free mice gavaged with T. sanguinis for 2 wk by determining BA concentrations in the plasma, liver, and cecum contents using liquid chromatography-tandem mass spectrometry.

RESULTS

The results showed that leucine deprivation resulted in a significant increase in total BA concentration in the plasma and an increase in the liver, but no difference in total BA was observed in the cecum contents before and after leucine deprivation. Furthermore, leucine deprivation significantly altered BA profiles such as taurocholic acid and ω-muricholic acid in the plasma, liver, and cecum contents. CYP7A1 expression was significantly upregulated in the liver under leucine deprivation. Leucine deprivation also regulated the composition of the gut microbiota; specifically, it significantly upregulated the relative abundance of T. sanguinis, thus enhancing the conversion of primary BAs into secondary BAs by intestinal T. sanguinis in mice.

CONCLUSIONS

Overall, leucine deprivation regulated BA profiles in enterohepatic circulation by upregulating hepatic CYP7A1 expression and increasing intestinal T. sanguinis abundance. Our findings reveal the contribution of gut microbiota to BA metabolism under dietary leucine deprivation.

A modified Mediterranean-style diet enhances brain function via specific gut-microbiome-brain mechanisms

Alzheimer's disease (AD) is a debilitating brain disorder with rapidly mounting prevalence worldwide, yet no proven AD cure has been discovered. Using a multi-omics approach in a transgenic AD mouse model, the current study demonstrated the efficacy of a modified Mediterranean-ketogenic diet (MkD) on AD-related neurocognitive pathophysiology and underlying mechanisms related to the gut-microbiome-brain axis. The findings revealed that MkD induces profound shifts in the gut microbiome community and microbial metabolites. Most notably, MkD promoted growth of the Lactobacillus population, resulting in increased bacteria-derived lactate production. We discovered elevated levels of microbiome- and diet-derived metabolites in the serum as well, signaling their influence on the brain. Importantly, these changes in serum metabolites upregulated specific receptors that have neuroprotective effects and induced alternations in neuroinflammatory-associated pathway profiles in hippocampus. Additionally, these metabolites displayed strong favorable co-regulation relationship with gut-brain integrity and inflammatory markers, as well as neurobehavioral outcomes. The findings underscore the ameliorative effects of MkD on AD-related neurological function and the underlying gut-brain communication via modulation of the gut microbiome-metabolome arrays.

Research progress in the role and mechanism of Leucine in regulating animal growth and development

Leucine, a branched-chain amino acid, is essential in regulating animal growth and development. Recent research has uncovered the mechanisms underlying Leucine's anabolic effects on muscle and other tissues, including its ability to stimulate protein synthesis by activating the mTORC1 signaling pathway. The co-ingestion of carbohydrates and essential amino acids enhances Leucine's anabolic effects. Moreover, Leucine has been shown to benefit lipid metabolism, and insulin sensitivity, making it a promising strategy for preventing and treating metabolic diseases, including type 2 diabetes and obesity. While emerging evidence indicates that epigenetic mechanisms may mediate Leucine's effects on growth and development, more research is needed to elucidate its mechanisms of action fully. Specific studies have demonstrated that Leucine promotes muscle growth and metabolic health in animals and humans, making it a promising therapeutic agent. However, it is essential to note that Leucine supplementation may cause digestive issues or interact with certain medications, and More study is required to determine definitively optimal dosages. Therefore, it is important to understand how Leucine interacts with other nutrients, dietary factors, and lifestyle habits to maximize its benefits. Overall, Leucine's importance in human nutrition is far-reaching, and its potential to prevent muscle loss and enhance athletic performance warrants further investigation.

Gut microbiota bridges dietary nutrients and host immunity

Dietary nutrients and the gut microbiota are increasingly recognized to cross-regulate and entrain each other, and thus affect host health and immune-mediated diseases. Here, we systematically review the current understanding linking dietary nutrients to gut microbiota-host immune interactions, emphasizing how this axis might influence host immunity in health and diseases. Of relevance, we highlight that the implications of gut microbiota-targeted dietary intervention could be harnessed in orchestrating a spectrum of immune-associated diseases.

Recent progress in plant-derived polysaccharides with prebiotic potential for intestinal health by targeting gut microbiota: a review

Natural products of plant origin are of high interest and widely used, especially in the food industry, due to their low toxicity and wide range of bioactive properties. Compared to other plant components, the safety of polysaccharides has been generally recognized. As dietary fibers, plant-derived polysaccharides are mostly degraded in the intestine by polysaccharide-degrading enzymes secreted by gut microbiota, and have potential prebiotic activity in both non-disease and disease states, which should not be overlooked, especially in terms of their involvement in the treatment of intestinal diseases and the promotion of intestinal health. This review elucidates the regulatory effects of plant-derived polysaccharides on gut microbiota and summarizes the mechanisms involved in targeting gut microbiota for the treatment of intestinal diseases. Further, the structure-activity relationships between different structural types of plant-derived polysaccharides and the occurrence of their prebiotic activity are further explored. Finally, the practical applications of plant-derived polysaccharides in food production and food packaging are summarized and discussed, providing important references for expanding the application of plant-derived polysaccharides in the food industry or developing functional dietary supplements.

Dietary Leucine Improves Fish Intestinal Barrier Function by Increasing Humoral Immunity, Antioxidant Capacity, and Tight Junction

This study attempted to evaluate the possible impact and mechanism of leucine (Leu) on fish intestinal barrier function. One hundred and five hybrid Pelteobagrus vachelli ♀ × Leiocassis longirostris ♂ catfish were fed with six diets in graded levels of Leu 10.0 (control group), 15.0, 20.0, 25.0, 30.0, 35.0, and 40.0 g/kg diet for 56 days. Results showed that the intestinal activities of LZM, ACP, and AKP and contents of C3, C4, and IgM had positive linear and/or quadratic responses to dietary Leu levels. The mRNA expressions of itnl1, itnl2, c-LZM, g-LZM, and β-defensin increased linearly and/or quadratically (p < 0.05). The ROS, PC, and MDA contents had a negative linear and/or quadratic response, but GSH content and ASA, AHR, T-SOD, and GR activities had positive quadratic responses to dietary Leu levels (p < 0.05). No significant differences on the CAT and GPX activities were detected among treatments (p > 0.05). Increasing dietary Leu level linearly and/or quadratically increased the mRNA expressions of CuZnSOD, CAT, and GPX1α. The GST mRNA expression decreased linearly while the GCLC and Nrf2 mRNA expressions were not significantly affected by different dietary Leu levels. The Nrf2 protein level quadratically increased, whereas the Keap1 mRNA expression and protein level decreased quadratically (p < 0.05). The translational levels of ZO-1 and occludin increased linearly. No significant differences were indicated in Claudin-2 mRNA expression and protein level. The transcriptional levels of Beclin1, ULK1b, ATG5, ATG7, ATG9a, ATG4b, LC3b, and P62 and translational levels of ULK1, LC3Ⅱ/Ⅰ, and P62 linearly and quadratically decreased. The Beclin1 protein level was quadratically decreased with increasing dietary Leu levels. These results suggested that dietary Leu could improve fish intestinal barrier function by increasing humoral immunity, antioxidative capacities, and tight junction protein levels.

Leucine supplementation alleviates immune and antioxidant function damage in adult rats induced by early weaning

BACKGROUND

Early weaning (EW) can lead to stress and destroy intestinal integrity. Leucine has functional diversity in antioxidant, immune, and metabolic regulation.

OBJECTIVE

This study aims to explore a lifelong impact of early weaning on intestinal, immune and antioxidant functions of adult rats and the role of leucine supplementation in the alleviation of the damage caused by early weaning.

METHODS

In this 211-day study, 36 SD rat pups were divided into three groups: 21-day weaning normal group (C), 17-day early weaning group (E) and 17-day early weaning group with two-month leucine supplementation (EL). The content of amino acids in serum, immune and antioxidant indexes, intestinal morphology, liver transcriptomics, mRNA, and protein expression of signaling pathway were determined.

RESULTS

EW reduced the protein expression level of sIgA and GSH in jejunum, and increased the protein expression levels of IgA, IgM, and IL-17 in serum, and TNFα and IL-1β in jejunum. The impairment by EW was activated via NF-κB signal pathway. In terms of antioxidation, EW reduced the level of GSH in jejunum. After leucine supplementation, the damage induced by EW was partially repaired.

CONCLUSIONS

EW causes long-term damage to the intestinal barrier function, immunity, apoptosis factor, and antioxidant function of rats and leucine supplementation could alleviate the impairment, suggesting possible approach to EW.

Maternal resveratrol regulates the growth performance, antioxidant capacity, and intestinal health of suckling piglets through intestinal microorganisms at high summer temperatures

Background

Resveratrol has numerous beneficial properties, including antioxidant, anti-inflammatory, and immunomodulatory properties. High summer temperatures in Southern China affect the reproductive performance of sows. The present study aimed to investigate the effects of dietary resveratrol supplementation in different thermal environments on the reproductive performance, antioxidant capacity, immune function, and intestinal microbes of sows and piglets during late gestation and lactation, as well as their relationship with colostrum immunoglobulin.

Methods

A two-phase experiment was conducted with 40 healthy multiparous sows. In the first phase of the experiment, 20 sows were used in a moderate temperature environment, and in the second phase of the experiment, the remaining 20 sows were used in a high-temperature environment. In both phases, sows were fed either a control diet or a diet consists of control diet and 300 mg/kg resveratrol starting on day 75 of gestation. Plasma, milk, and fecal samples were collected to obtain the indices of antioxidant capacity, immune function, and intestinal microbes.

Results

The results showed that resveratrol supplementation increased the number of live births by 13.24 and 26.79% in the first and second phases, respectively, compared with the control group. In the second phase, resveratrol supplementation increased litter weight at weaning and in the concentrations of growth hormone (GH), insulin (INS), progesterone (PROG), triglycerides, and uric acid (UA). The plasma superoxide dismutase (SOD) level on day 110 of gestation and day 14 of lactation, as well as glutathione peroxidase (GSH-Px) on day 14 of lactation in the first phase, showed an increasing trend (p = 0.0728, p = 0.0932, and p = 0.067, respectively) in the resveratrol group, compared with the control group. On day 14 of lactation, the plasma total antioxidant capability (T-AOC) level was higher in the second phase, while the plasma malondialdehyde (MDA) level was lower in both phases in the resveratrol group. Resveratrol supplementation increased the abundance of immunoglobulin A (IgA), immunoglobulin G (IgG), and immunoglobulin M (IgM) in colostrum and the relative abundance of Lactobacillus and Alloprevotella but decreased the relative abundance of Escherichia-shigella in piglet feces in the second phase. In addition, Spearman's correlation analysis indicated that the weight gain of weaned piglets was positively (p < 0.05) associated with IgM content in colostrum and the abundance of Lactobacillus in the fecal microbiota of piglets in the second phase. Moreover, the abundance of Alloprevotella was positively correlated with the contents of IgA and IgG in colostrum, while the abundance of Lactobacillus was positively correlated with IgM content.

Conclusion

These findings indicated that maternal resveratrol supplementation could enhance the growth performance, antioxidant capacity, and intestinal health of piglets in a high temperature environment, which might be associated with increased immunoglobin secretion from colostrum.

S. boulardii Early Intervention Maintains Gut Microbiome Structure and Promotes Gut Mucosal Barrier Function in Early-Weaned Rats

Early weaning leads to the disorder of the gut microbiome and gut mucosal barrier injury. Early intervention of gut microbiome colonization contributes to the development of the gut microbiome and gut function. The aim of this study was to explore the effects of Saccharomyces boulardii (S. boulardii) early intervention on the gut microbiome structure and gut mucosal barrier function of early-weaned rats. The results showed that S. boulardii early intervention improved growth performance along with a decrease in pathogenic bacteria, an increase in beneficial bacteria, a stable and complex microbiome, and a high level of microbial metabolism. Moreover, S. boulardii upregulated the mucosal barrier function including goblet cells and relative gene expression, tight junction, and sIgA level. Furthermore, S. boulardii suppressed the inflammatory response and promoted the anti-inflammatory response. Our study may provide a possible early intervention strategy for preventing an early weaning-induced disorder of the gut microbiome and loss of gut mucosal barrier function.

The secretion of sIgA and dendritic cells activation in the intestinal of cyclophosphamide-induced immunosuppressed mice are regulated by Alhagi honey polysaccharides

BACKGROUND

It remains a huge challenge to recover the intestine immune function for the treatment of intestinal mucosal damage from chemotherapy with cyclophosphamide (CY). Alhagi honey polysaccharide (AH) has immunomodulation pharmacological activity, but the effect and mechanism on the intestinal immune system of CY-mice remain unclear.

PURPOSE

In this experiment, the immunomodulatory activity of AH on intestinal immune in CY-mice and its mechanism of regulating the intestinal immune system was investigated.

STUDY DESIGN AND METHODS

The experiment studied the immunomodulatory activity of AH on the intestinal immune system and its mechanism for the first time from in vitro and in vivo experiments. We investigated the immunomodulatory effects of AH on Caco-2 and dendritic cells (DCs) in vitro by using western blot (WB), flow cytometry, quantitative real-time PCR (qPCR), and ELISA methods. In vivo experiment, the immunosuppressive mouse model was established through being given intraperitoneal injection with CY (80 mg/kg) for 3 days. Then, mice oral administration of 800 mg/kg AH and 40 mg/kg levamisole hydrochloride for a week. Immunofluorescence, flow cytometry, ELISA, qPCR and WB were applied to examine the immunomodulatory activity of AH on the intestinal immune function of CY-mice, as well as the function of AH on the concentration of SCFAs in cecum by Gas chromatographic analysis.

RESULTS

In vitro experiments, AH could significantly stimulate the expression of pIgR protein in Caco-2. It could also induce the DCs maturation and release the cytokines to regulate the immune response. In vivo experiments, AH could remarkably stimulate the DCs maturation and secrete more CCL20 to recruit DCs, then induce the T (CD4⁺ and CD8⁺) and B cells proliferation and activation. Moreover, it could further induce T helper cells to differentiate and secrete cytokines to enhance the secretion of sIgA. Furthermore, it also directly activated DCs and released cytokines to increase the content of pIgR, J-chain, and IgA⁺ cells in intestine, thereby enhancing the secretion of sIgA to protect the intestine. In addition, AH could obviously strengthen the SCFAs production in cecum to regulate the intestinal immune dysfunction induced by CY.

CONCLUSION

In summary, oral administrated AH exhibits great benefits for treating CY-induced intestinal immunosuppression, and the mechanism of action mainly involves sIgA, DCs, SCFAs.

The Effect of Dietary Leucine Supplementation on Antioxidant Capacity and Meat Quality of Finishing Pigs under Heat Stress

This study examined the effects of dietary leucine supplements on antioxidant capacity and meat quality in growing-finishing pigs. A total of 24 crossbred (Duroc × Landrace × Yorkshire) pigs with an average initial weight of 68.33 ± 0.97 kg were randomly allotted to three treatment groups. All pigs were exposed to constant heat stress. Each group of pigs was fed a basal diet, or a diet supplemented with increasing levels of leucine (0.25% or 0.50%). The results showed that leucine intake could improve average daily gain and reduce feed/gain of finishing pigs under heat stress (p < 0.05). The supplementation of leucine could improve the carcass slant length (p = 0.09), and dramatically increased loin-eye area of the finishing pigs (p < 0.05) but had no significant effect on other carcass traits. Compared with the control group, 0.50% leucine markedly reduced drip loss and shear force of longissimus dorsi muscle, and increased pH value at 24 h after slaughter (p < 0.05). Dietary supplementation of 0.25% leucine increased the contents of inosine monophosphate and intramuscular fat in biceps femoris muscle (p < 0.05). Supplementation of 0.25% or 0.50% leucine significantly stimulated the activities of antioxidant enzymes while reduced the level of MDA in serum, liver and longissimus dorsi muscle (p < 0.05). Compared with the control group, 0.50% leucine supplementation markedly modulated the relative mRNA expression levels of genes related to muscle fiber type and mitochondrial function in longissimus dorsi muscle and the gene relative antioxidant in the liver (p < 0.05). In conclusion, dietary leucine supplementation could improve the growth performance and meat quality of the finishing pigs under heat stress, and the pathway of Keap1-NRF2 and PGC-1α-TFAM might be involved.

Ornithine α-Ketoglutarate Alleviates Inflammation via Regulating Ileal Mucosa Microbiota and Metabolites in Enterotoxigenic Escherichia coli-Infected Pigs

Enterotoxigenic Escherichia coli (ETEC) is one of the main causes of diarrhea in weaned piglets, and ornithine α-ketoglutarate (OKG) as a food supplement has been shown to improve intestinal immune status in animals and humans. However, it remains unknown whether OKG alleviates inflammation through the regulation of gut microbiota and its metabolites on ETEC-infected piglets. This study was conducted to explore the impact of OKG on growth performance, immunity, and ileal mucosa microbiota and its metabolites in piglets infected with ETEC. On a total of 40 pigs, a 2 × 2 factor design was performed; the major factors were diet (basal diet or 1% OKG diet) and challenge (E. coli or LB Broth). The results showed that ETEC-infection inhibited growth performance, and OKG supplementation alleviated growth performance. Interestingly, ETEC-infection increased the serum TNF-α and IL-6, decreased the serum IL-10, downregulated the mRNA expression of IL-1β, IL-6, MyD88, and improved the mRNA expression of IL-8, IL-18, and TLR4. OKG inhibited serum IL-6, suppressed the phosphorylation of downstream signals of NF-κB/JNK in the ileum, and enhanced serum IL-10 and ileum SIgA in ETEC-challenged piglets. OKG supplementation enhanced the mRNA expression of IL-1β and IL-10 and reduced NF-κB and MyD88 in the ileum. Importantly, OKG reversed intestinal microbiota dysfunction, including the diversity of ileal microbiota, the relative abundances of Actinobacillus, Turicibacter, and [Acetivibrio]_ethanolgignens_group, which significantly affected arachidonic acid metabolism and primary bile acid biosynthesis. Collectively, our results suggest that OKG improves growth performance, regulates immunity, and ileal mucosa microbiota and its metabolites in ETEC-infected piglets.

Oral S2-Ag85 DNA Vaccine Activated Intestinal Cell dsDNA and RNA Sensors to Promote the Presentation of Intestinal Antigen

Objective

To explore the molecular mechanism by which oral S2-Ag85DNA vaccines present intestinal antigens. The oral S2-Ag85 vaccine has been shown to protect the human body and effectively improve the titration of the vaccine by acting on intestinal mucosa cells and enhancing their immunogenicity.

Method

Mice were immunized with the recombinant S2-Ag85 vaccine, and antibody secretion was then detected in the intestinal tissue. The molecular mechanisms of in vitro detection sensor molecules RIG-1, Pol III, and related conductor transductor molecules DAI, STING, AIM2, IRF3, and IRF7 were determined by separating intestinal IEC, DC, and IELC cells.

Results

The S2-Ag85A vaccine was effective in activating dsDNA and RNA transduction pathways in intestinal cells and improving intestinal antigen presentation in mice.

Dietary regulation of the SIgA-gut microbiota interaction

Gut microbiota (GM) is essential for host health, and changes in the GM are related to the development of various diseases. Recently, secretory immunoglobulin A (SIgA), the most abundant immunoglobulin isotype in the intestinal mucosa, has been found to play an essential role in controlling GM. SIgA dysfunction can lead to changes in the GM and is associated with the development of various GM-related diseases. Although in early stage, recent studies have shown that assorted dietary interventions, including vitamins, amino acids, fatty acids, polyphenols, oligo/polysaccharides, and probiotics, can influence the intestinal SIgA response and SIgA-GM interaction. Dietary intervention can enhance the SIgA response by directly regulating it (from top to bottom) or by regulating the GM structure or gene expression (from bottom to top). Furthermore, intensive studies involving the particular influence of dietary intervention on SIgA-binding to the GM and SIgA repertoire and the precise regulation of the SIgA response via dietary intervention are still exceedingly scarce and merit further consideration. This review summarizes the existing knowledge and (possible) mechanisms of the influence of dietary intervention on the SIgA-GM interaction. Key issues are considered, and the approaches in addressing these issues in future studies are also discussed.

Tea Polyphenols: A Natural Antioxidant Regulates Gut Flora to Protect the Intestinal Mucosa and Prevent Chronic Diseases

The intestinal tract of a healthy human body hosts many microorganisms that are closely linked to all aspects of people’s lives. The impact of intestinal flora on host health is no longer limited to the gut but can also affect every organ in the body through various pathways. Studies have found that intestinal flora can be altered by external factors, which provides new ideas for treating some diseases. Tea polyphenols (TP), a general term for polyphenols in tea, are widely used as a natural antioxidant in various bioactive foods. In recent years, with the progress of research, there have been many experiments that provide strong evidence for the ability of TP to regulate intestinal flora. However, there are very few studies on the use of TP to modify the composition of intestinal microorganisms to maintain health or treat related diseases, and this area has not received sufficient attention. In this review, we outline the mechanisms by which TP regulates intestinal flora and the essential role in maintaining suitable health. In addition, we highlighted the protective effects of TP on intestinal mucosa by regulating intestinal flora and the preventive and therapeutic effects on certain chronic diseases, which will help further explore measures to prevent related chronic diseases.

Pyruvate Might Bridge Gut Microbiota and Muscle Health in Aging Mice After Chronic High Dose of Leucine Supplementation

Background: The previous studies demonstrated that there might be complex and close relationships among leucine supplementation, gut microbiota, and muscle health, which still needs further investigation.

Aims: This study aimed to explore the associations of gut microbiota with muscle health after leucine intake.

Methods: In this study, 19-month-old male C57BL/6j mice (n = 12/group) were supplemented with ultrapure water, low dose of leucine (500 mg/kg·d), and high dose of leucine (1,250 mg/kg·d) for 12 weeks by oral gavage. The mice fecal samples in each group before and after supplementation were collected for baseline and endpoint gut microbiota analysis by using 16S rDNA amplicon sequencing. Meanwhile, ultrasound measurement, H&E staining, myofiber cross-sectional area (CSA) measurement, and western blotting were performed in the quadriceps subsequently. The pyruvate levels were detected in feces.

Results: Improvement in muscle of histology and ultrasonography were observed after both low and high dose of leucine supplementation. High dose of leucine supplementation could promote skeletal muscle health in aging mice via regulating AMPKα/SIRT1/PGC-1α. The richness and diversities of microbiota as well as enriched metabolic pathways were altered after leucine supplementation. Firmicutes-Bacteroidetes ratio was significantly decreased in high-leucine group. Moreover, pyruvate fermentation to propanoate I were negatively associated with differential species and the pyruvate levels were significantly increased in feces after high dose of leucine supplementation.

Conclusions: Chronic high dose of leucine supplementation changed gut microbiota composition and increased pyruvate levels in the feces, which possibly provides a novel direction for promoting muscle health in aging mice.

Alterations in Faecal Microbiota and Elevated Levels of Intestinal IgA Following Oral Administration of Lacticaseibacillus casei in mice

The intestinal microbiota has been identified as a crucial regulator of the overall health, with studies describing its influence in a variety of disorders and developmental processes throughout the body. A widely accepted approach of influencing the microbiota and regulating its functionality in health or disease is the consumption of probiotics. In this study, we aimed to identify the impact of probiotic Lacticaseibacillus casei ATCC393 on the intestinal microbiota of mice and circulating soluble products of microbial origin or the immune system. Investigation of the gut microflora using next-generation sequencing analysis revealed alterations in the microbial populations following consumption of the probiotic. Abundance of taxa classified as Muribaculaceae was increased in lactobacilli-fed animals, while abundance of taxa classified as Lachnospiraceae and Oscillospiraceae was decreased. In addition, the composition of the intestinal microbiota was modified by the administration of L. casei, as evident by the clustering of test subjects when inspecting beta diversity, without however any significant effect on the alpha diversity of the animals. Finally, production of IgA in the intestinal lumen of mice that had received the microorganism was significantly increased, as was the concentration of lactic acid, while levels of acetic acid were noticeably lower in the L. casei group. The findings suggest that L. casei can be considered a potential candidate strain for the modulation of intestinal homeostasis and a component of dietary interventions aiming to improve overall health.

Anti-Inflammatory and Immunomodulatory Properties of Fermented Plant Foods

Fermented plant foods are gaining wide interest worldwide as healthy foods due to their unique sensory features and their health-promoting potentials, such as antiobesity, antidiabetic, antihypertensive, and anticarcinogenic activities. Many fermented foods are a rich source of nutrients, phytochemicals, bioactive compounds, and probiotic microbes. The excellent biological activities of these functional foods, such as anti-inflammatory and immunomodulatory functions, are widely attributable to their high antioxidant content and lactic acid-producing bacteria (LAB). LAB contribute to the maintenance of a healthy gut microbiota composition and improvement of local and systemic immunity. Besides, antioxidant compounds are involved in several functional properties of fermented plant products by neutralizing free radicals, regulating antioxidant enzyme activities, reducing oxidative stress, ameliorating inflammatory responses, and enhancing immune system performance. Therefore, these products may protect against chronic inflammatory diseases, which are known as the leading cause of mortality worldwide. Given that a large body of evidence supports the role of fermented plant foods in health promotion and disease prevention, we aim to discuss the potential anti-inflammatory and immunomodulatory properties of selected fermented plant foods, including berries, cabbage, and soybean products, and their effects on gut microbiota.

Effects of Mannan Oligosaccharides and/or Bifidobacterium on Growth and Immunity in Domestic Pigeon (Columba livia domestica)

The goal of this study was to evaluate the influences of mannan oligosaccharides (MOSs) and/or Bifidobacterium on the growth and immunity of pigeons over a 56-day period. One hundred paired adult pigeons were randomly divided into four groups of five paired pigeons. Paired pigeons with two young squabs were housed in a man-made aviary. Parent pigeons in the control group received a basal diet (C), while the other three groups were fed with the basal diet supplemented with 20 g of MOSs/kg of feed (M), 10 g Bifidobacterium (1×1010 CFU/g)/kg of feed (B), or a combination of M and B (MB). We found higher body weights (BW) in pigeons of the B group than in the C, M, and MB groups. None of the treatments exerted significant effects involving spleen and thymus indices, whereas M birds tended to improve the bursa of Fabricius index. Pigeons fed with the M-supplemented diet exhibited improved serum immunoglobulin M (IgM) concentrations compared with those fed with C and the B- and MB-supplemented diets. In addition, M treatment increased immunoglobulin A (IgA) levels compared with MB treatment. MB treatment improved serum immunoglobulin G (IgG) concentrations compared to that by the C treatment. The concentration of secretory immunoglobulin A (sIgA) was significantly reduced in the duodenum and increased in the ileum in pigeons fed with the MB-supplemented diet. This study indicated that dietary supplementation with Bifidobacterium increased the growth performance. Dietary supplementation with MOSs or in combination with Bifidobacterium was able to improve immune function in pigeons but exerted no apparent effect on weight gain. Accordingly, in terms of economic benefits, the findings suggested that supplementation with Bifidobacterium alone may improve production performance, and that supplementation with MOSs alone may improve immune function in pigeons.

Effects of GABA Supplementation on Intestinal SIgA Secretion and Gut Microbiota in the Healthy and ETEC-Infected Weanling Piglets

Pathogenic enterotoxigenic Escherichia coli (ETEC) has been considered a major cause of diarrhea which is a serious public health problem in humans and animals. This study was aimed at examining the effect of γ-aminobutyric acid (GABA) supplementation on intestinal secretory immunoglobulin A (SIgA) secretion and gut microbiota profile in healthy and ETEC-infected weaning piglets. A total of thirty-seven weaning piglets were randomly distributed into two groups fed with the basal diet or supplemented with 40 mg·kg-1 of GABA for three weeks, and some piglets were infected with ETEC at the last week. According to whether ETEC was inoculated or not, the experiment was divided into two stages (referred as CON1 and CON2 and GABA1 and GABA2). The growth performance, organ indices, amino acid levels, and biochemical parameters of serum, intestinal SIgA concentration, gut microbiota composition, and intestinal metabolites were analyzed at the end of each stage. We found that, in both the normal and ETEC-infected piglets, jejunal SIgA secretion and expression of some cytokines, such as IL-4, IL-13, and IL-17, were increased by GABA supplementation. Meanwhile, we observed that some low-abundance microbes, like Enterococcus and Bacteroidetes, were markedly increased in GABA-supplemented groups. KEGG enrichment analysis revealed that the nitrogen metabolism, sphingolipid signaling pathway, sphingolipid metabolism, and microbial metabolism in diverse environments were enriched in the GABA1 group. Further analysis revealed that alterations in microbial metabolism were closely correlated to changes in the abundances of Enterococcus and Bacteroidetes. In conclusion, GABA supplementation can enhance intestinal mucosal immunity by promoting jejunal SIgA secretion, which might be related with the T-cell-dependent pathway and altered gut microbiota structure and metabolism.

Lactobacillus casei-fermented blueberry pomace augments sIgA production in high-fat diet mice by improving intestinal microbiota

Intestinal secretory immunoglobulin A (sIgA)-improving function of Lactobacillus casei-fermented blueberry pomace (FBP) was investigated in this study.

Dietary Supplementation With Citrus Extract Altered the Intestinal Microbiota and Microbial Metabolite Profiles and Enhanced the Mucosal Immune Homeostasis in Yellow-Feathered Broilers

The present study aimed to investigate the effects of citrus extract (CE) on intestinal microbiota, microbial metabolite profiles, and the mucosal immune status in broilers. A total of 540 one-day-old yellow-feathered broilers were randomly allotted into three groups and fed a basal diet (control group), or a basal diet containing 10 mg/kg of zinc bacitracin (antibiotic group), or 10 mg/kg of CE (CE group). Each treatment consisted of six replicates, with 30 broilers per replicate. After 63-day feeding, two broilers per replicate were randomly selected and slaughtered, and their ileal and cecal digesta and ileal tissue were collected for microbial composition, microbial metabolites, and gene expression analysis. The results showed that CE significantly increased the abundance of Barnesiella and Blautia than did the antibiotic group (adjusted P < 0.05), whereas it decreased the abundance of Alistipes and Bacteroides (adjusted P < 0.05). Meanwhile, the CE group also increased the numbers of Bifidobacterium and Lactobacillus than did the control and antibiotic groups (P < 0.05), whereas it decreased the number of Escherichia coli (P < 0.05). For microbial metabolites, dietary supplementation with CE increased the concentrations of lactate, total short-chain fatty acids, acetate, and butyrate in the cecum than did the control and antibiotic groups (P < 0.05), whereas it decreased the concentrations of amino acid fermentation products (ammonia, amines, p-cresol, and indole) (P < 0.05). Additionally, supplementation with CE up-regulated (P < 0.05) the mRNA expression of intestinal barrier genes (ZO-1 and Claudin) in the ileum than did both the control and antibiotic groups. However, antibiotic treatment induced gut microbiota dysbiosis, altered the microbial metabolism, and disturbed the innate immune homeostasis. In summary, these results provide evidence that dietary supplementation with CE can improve the intestinal barrier function by changing microbial composition and metabolites, likely toward a host-friendly gut environment. This suggests that CE may possibly act as an efficient antibiotic alternative for yellow-feathered broiler production.