Attenuating effect of melatonin on lipopolysaccharide-induced chicken small intestine inflammation

Alginate Oligosaccharide Attenuates Lipopolysaccharide-Induced Intestinal Barrier Dysfunction in Balb/c Mice: Mechanistic Insights

Alginate oligosaccharide (AOS) is a structurally distinct carbohydrate derived from marine algae. In this study, AOS was obtained through the enzymatic hydrolysis of alginate, and the anti-inflammatory efficacy of AOS was assessed in lipopolysaccharide (LPS)-induced inflammatory Balb/c mice. AOS effectively suppressed the overexpression of TNF-α, IL-6, and MDA while restoring the reduced SOD activity. Histopathological analysis revealed that AOS significantly reduced the level of LPS-induced tissue edema, inflammatory infiltration, and villous destruction. Additionally, AOS notably upregulated tight junction proteins Claudin-1, Occludin, and ZO-1 expression. Transcriptomic and Western blot analyses indicated that AOS primarily mediated the restriction of the TLR4/MAPK/NF-κB pathway in the jejunum. Moreover, AOS ameliorated gut microbiota dysbiosis, such as increasing in Bacteroidota, alongside decreasing in Firmicutes, Campylobacter, and Desulfovibrio, respectively. Metabolomics demonstrated that AOS improved the LPS-induced reduction of short-chain fatty acids in the gut. These results provide compelling evidence supporting the potential of AOS against acute intestinal inflammation.

The Therapeutic Potential of Melatonin and Its Novel Synthetic Analogs in Circadian Rhythm Sleep Disorders, Inflammation-Associated Pathologies, and Neurodegenerative Diseases

Melatonin, N-acetyl-5-methoxytryptamine, is a tryptophan-derived hormone mostly produced in the pineal gland, despite being synthesized locally at several tissues and organs. This production is rhythmically controlled by complex clock gene networks in the master pacemaker located in the suprachiasmatic nucleus of the hypothalamus. Melatonin is usually secreted only during the dark phase of the day and is essential to synchronize circadian rhythms and neuroendocrine physiological processes. Its main clinical use is associated with the treatment of jet lag and other circadian rhythm sleep disorders, with a growing number of other promising therapeutic applications due to the diverse physiological roles of melatonin. In this review, we explore melatonin and its receptors and provide an updated overview on research concerning the role of melatonin, either as an endogenous molecule or as a drug, in: sleep-wake cycle regulation; circadian rhythms; inflammatory processes that may compromise cardiovascular, respiratory, gastrointestinal, renal, and reproductive system functions; and neurodegenerative disorders such as Alzheimer's and Parkinson's disease. The most recent and promising research findings concerning melatonin synthetic analogs such as agomelatine and ramelteon are highlighted, pointing toward new compounds with promising pharmacological activity while emphasizing their structural differences and advantages when compared to melatonin.

Dietary supplementation with farnesol confers a protective effect on the intestine of broiler chickens challenged with lipopolysaccharide by reshaping intestinal flora structure and regulating TLR4/NF-κB signaling pathway

Farnesol (FAN), one of plant essential oils, is widely found in a variety of natural plants. Studies demonstrated that FAN contributed to the antioxidant and immune function as well as improving the intestinal flora, however effects of it on the broiler chickens has not been fully characterized. In the present study, we present an undated report of its effects on growth performance, antioxidant and immune functions of broiler chickens challenged with lipopolysaccharide (LPS). One hundred healthy male AA+ broiler chickens with uniform body weight were divided into control and FAN groups, there were five replicates and 10 birds in each one. The trial lasted for 28 days, and two birds with uniform body weight were selected from each replicate to be treated with intraperitoneal injection of LPS at the end of the trial, and then samples were harvested after 3 h. Results showed that dietary supplementary with FAN tended to improve the feed conversion ratio (FCR) (P = 0.058). The levels of serum lactate dehydrogenase and IL-1β were elevated in the birds challenged with LPS, as well as the content of malondialdehyde in the ileal and liver (P < 0.05). Additionally, LPS treatment descended the levels of catalase and superoxide dismutase, and the ratio of villi height to crypt depth in the ileum (P < 0.05). Dietary supplementation with FAN was able to alleviate the abnormal changes of the above indexes caused by LPS. In addition, dietary supplementation with FAN also contributed to alleviating the up-regulation of Toll-like receptor 4 (TLR-4), nuclear transcription factor κB (NF-κB), myeloid differentiation primary response gene 88 (MYD88), tumor necrosis factor (TNF-α) and IL-1β transcription levels in the ileum and liver of birds challenged with LPS (P < 0.05). Results of intestinal flora demonstrated that the relative abundance of Candidatus Arthromitus was up-regulated in the ileal chyme of birds challenged with LPS, and dietary supplementation with FAN could reshape it. Intriguingly, the relative abundance of Candidatus Arthromitus was positively correlated with the mRNA levels of TLR-4, NF-κB, MYD88, TNF-α and IL-1β in the ileum (P < 0.05). In conclusion, dietary supplementation with FAN might confer a protective effect on the intestine of broiler chickens challenged with lipopolysaccharide by reshaping intestinal flora, especially Candidatus Arthromitus, and regulating TLR4/NF-κB signaling pathway.

Immune-pineal-ocular Axis in Amphibians: Unveiling A Novel Connection

Melatonin is a hormone known as an endogenous temporal marker signaling the dark phase of the day. Although the eyes seem to be the main site of melatonin production in amphibians, little information is available about the natural variation in ocular melatonin levels and its modulation following immune stimulation. We investigated the daily variation of plasma and ocular melatonin levels in bullfrogs (Lithobates catesbeianus) and their modulation following an immune stimulation with lipopolysaccharide (LPS) in yellow cururu toads (Rhinella icterica). For the daily variation, bullfrogs were bled and then euthanized for eye collection every 3 h over 24 h to determine plasma and ocular melatonin levels. We found a positive correlation between ocular and plasma melatonin levels, with maximum values at night (22 h) for both plasma and the eyes. For immune stimulation, yellow cururu toads received an intraperitoneal injection of LPS or saline solution during the day (10 h) or at night (22 h). Two hours after injection, toads were bled and euthanized for eye collection to obtain plasma and ocular melatonin levels. In addition, the liver and bone marrow were collected to investigate local melatonin modulation. Our results demonstrate that retinal light-controlled rhythmic melatonin production is suppressed while liver and bone marrow melatonin levels increase during the inflammatory assemblage in anurans. Interestingly, the LPS injection decreased only ocular melatonin levels, reinforcing the central role of the eyes (i.e., retina) as an essential organ of melatonin production, and a similar role to the pineal gland during the inflammatory response in amphibians. Together, these results point to a possible immune-pineal-ocular axis in amphibians, yet to be fully described in this group.

Immunoregulatory properties of melatonin in the humoral immune system: A narrative review

Melatonin is the major product both synthesized and secreted by the pineal gland during the night period and it is the principal chronobiotic hormone that regulates the circadian rhythms and seasonal changes in vertebrate biology. Moreover, melatonin shows both a broad distribution along the phylogenetically distant organisms and a high functional versatility. At the present time, a significant amount of experimental evidence has been reported in scientific literature and has clearly shown a functional relationship between the endocrine, nervous, and immune systems. The biochemistry basis of the functional communication between these systems is the utilization of a common chemicals signals. In this framework, at present melatonin is considered to be a relevant member of the so-called neuro-endocrine-immunological network. Thus, both in vivo and in vitro investigations conducted in both experimental animals and humans, have clearly documented that melatonin has an important immunomodulatory role. However, most of the published results refer to information on T lymphocytes, i.e., cell-mediated immunity. On the contrary, fewer studies have been carried out on B lymphocytes, the cells responsible for the so-called humoral immunity. In this review, we have focused on the biological role of melatonin in the humoral immunity. More precisely, we report the actions of melatonin on B lymphocytes biology and on the production of different types of antibodies.

Lactobacillus reuteri alleviates LPS-induced intestinal mucosal damage by stimulating the expansion of intestinal stem cells via activation of the Wnt/β-catenin signaling pathway in broilers

The continuous expansion of intestinal stem cells (ISCs) is crucial for maintaining the renewal of the intestinal epithelium, particularly in inflammatory conditions. It remains largely unknown how the internal microbiota repair damage to the internal mucosal barrier. Hence, investigating potential anti-inflammatory probiotics from the intestinal symbolic microbes of broilers and analyzing their mechanism of action to support the intestinal mucosal barrier function can offer novel regulatory tools to alleviate broiler enteritis. In this research, we utilized in vivo broilers plus ex vivo organoids model to thoroughly examine the effectiveness of Lactobacillus reuteri (LR) in protecting the integrity of the intestinal mucosa during lipopolysaccharide-induced (LPS-induced) enteritis in broilers. The findings indicated that LR feeding maintained intestinal morphological and structural integrity, enhanced proliferation of intestinal epithelial cells, and inhibited cell apoptosis and inflammatory response against the deleterious effects triggered by LPS. Simultaneously, LR enhanced ISCs activity and stimulated intestinal epithelial regeneration to protect the intestinal barrier during LPS-induced injury conditions. The coculture system of LR and ileum organoids revealed that LR increased the growth of organoids and attenuated LPS-stimulated damage to organoids. Furthermore, the LPS-induced decrease in ISC activity was rescued by reactivation of Wnt/β-catenin signaling by LR ex vivo and in vivo. This research revealed that LR promoted the expansion of ISCs and intestinal epithelial cell renewal by regulating the Wnt/β-catenin signaling pathway, thereby maintaining the integrity of the intestinal mucosal barrier. This finding provided theoretical support for lactobacillus as a probiotic additive in livestock feed to improve intestinal inflammation and treat intestinal diseases.

Melatonin in animal husbandry: functions and applications

Melatonin (N-acetyl-5-methoxytryptamine) is an essential small molecule with diverse biological functions. It plays several key roles, including regulating the secretion of reproductive hormones and the reproductive cycle, enhancing the functionality of reproductive organs, improving the quality of sperm and eggs, and mitigating oxidative stress in the reproductive system. Melatonin effectively inhibits and scavenges excess free radicals while activating the antioxidant enzyme system and reduces the production of inflammatory factors and alleviates tissue damage caused by inflammation by regulating inflammatory pathways. Additionally, melatonin contributes to repairing the intestinal barrier and regulating the gut microbiota, thereby reducing bacterial and toxin permeation. The use of melatonin as an endogenous hormone in animal husbandry has garnered considerable attention because of its positive effects on animal production performance, reproductive outcomes, stress adaptation, disease treatment, and environmental sustainability. This review explores the characteristics and biological functions of melatonin, along with its current applications in animal production. Our findings may serve as a reference for the use of melatonin in animal farming and future developmental directions.

SeMet alleviates LPS-induced eggshell gland necroptosis mediated inflammation by regulating the Keap1/Nrf2/HO-1 pathway

Exposure to lipopolysaccharide (LPS) can lead to inflammation in a variety of tissues and organs. Selenium (Se) plays a crucial role in mitigating inflammatory damage. Compared with inorganic selenium, organic selenium, such as selenomethionine (SeMet), has the advantages of a higher absorption rate and lower toxicity in animals. This study examined the protective effects of SeMet on eggshell gland tissue damage caused by LPS. Hy-Line Brown laying hens were chosen as the experimental animals and were randomly assigned to four groups: control group (C), lipopolysaccharide group (LPS), SeMet group (Se), and SeMet + lipopolysaccharide group (Se + LPS). H&E staining and transmission electron microscope were performed to observe the pathological changes of eggshell glands, oxidative stress related indicators were measured using relevant kits, qRT‒PCR and western blotting were used to evaluate the mRNA and protein levels of the Nrf2 pathway, necroptosis, and inflammation related indicators. The results showed that LPS treatment increased the content of malondialdehyde (MDA), decreased the activities of superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GPX), and decreased the content of glutathione (GSH). LPS increased the levels of Keap1, RIPK1, RIPK3, MLKL, TNF-α, COX-2, and NF-κB, while decreasing the levels of HO-1, NQO1, Nrf2, and Caspase-8. However, SeMet treatment effectively reversed the changes of the above indicators, indicating that SeMet alleviates eggshell gland cell necroptosis-mediated inflammation induced by LPS via regulating the Keap1/Nrf2/HO-1 pathway. This study elucidated the mechanism by which SeMet alleviates LPS-induced eggshell gland tissue damage in Hy-Line Brown laying hens and provided a new direction for expanding the application of SeMet in the feeding and production of laying hens.

Pyrroloquinoline Quinone (PQQ) Improves Long-term Survival of Fat Grafts by Alleviating Oxidative Stress and Promoting Angiogenesis During the Early Phase After Transplantation

BACKGROUND

Reducing absorption after autologous fat grafting is a current challenge. Pyrroloquinoline quinone (PQQ) is the strongest known catalyst of redox reactions, which can scavenge reactive oxygen species (ROS) and alleviate oxidative stress.

OBJECTIVES

The aim of this study was to establish an in vivo model of PQQ-assisted lipotransfer and clarify the role of PQQ in reducing oxidative stress, alleviating apoptosis, and promoting angiogenesis during the acute hypoxic phase after grafting. In addition the study was performed to assess whether this intervention would have a positive effect on the improvement of long-term volume retention.

METHODS

Different concentrations of PQQ (low: 10 μM, medium: 100 μM, and high: 1000 μM) were mixed with human adipose tissue and transplanted subcutaneously into nude mice. Meanwhile, a control group of phosphate-buffered saline in an equal volume to PQQ was set up. On the third day after grafting, whole mount fluorescence staining was applied to detect ROS, mitochondrial membrane potential (MMP), apoptosis, adipocyte activity, and angiogenesis. Graft volume retention rate and electron microscopic morphology were evaluated at the third month. Immunohistochemistry and polymerase chain reaction (PCR) were further employed to elucidate the mechanism of action of PQQ.

RESULTS

PQQ-assisted fat grafting improved the long-term volume retention, promoted the quality and viability of the adipose tissue, and reduced the level of fibrosis. The underlying mechanism of PQQ assisted in scavenging the accumulated ROS, restoring MMP, enhancing adipocyte viability, alleviating tissue apoptosis, and promoting timely angiogenesis during the hypoxia stress phase. The most effective concentration of PQQ was 100 μM. Immunohistochemistry and PCR experiments confirmed that PQQ reduced the expression of Bax and cytochrome c in the mitochondrial apoptotic pathway and increased the level of the antiapoptotic molecule Bcl-2.

CONCLUSIONS

PQQ could improve the long-term survival of adipocytes by alleviating hypoxic stress and promoting timely angiogenesis in the early phase following lipotransfer.

LEVEL OF EVIDENCE: 4

Effect of Wu Zhi San supplementation in LPS-induced intestinal inflammation and barrier damage in broilers

Intestinal inflammation and barrier damage can inhibit the absorption and transportation of nutrients in the small intestine, and lead to various chronic diseases. Wu Zhi San (WZS) is a traditional Chinese formula composed of Schisandrae, Anemarrhenae, Lonicerae, and Glycyrrhizae that was made to cure intestinal inflammation and barrier damage in broilers. To evaluate the protective effect of WZS on intestinal inflammation and barrier damage of broilers under lipopolysaccharide (LPS) stress, a total of 200 one-day-old broilers were randomly divided into five groups, namely, the CON group, LPS group, and three WZS groups (WZS-H, WZS-M, and WZS-L). The groups were designed for stress phase I (days 15, 17, 19, and 21) and stress phase II (days 29, 31, 33, and 35). The protective effect of WZS on the intestinal tract was evaluated by measuring the levels of serum myeloperoxidase (MPO), diamine oxidase (DAO), super oxide dismutase (SOD), and serum D-lactate (D-LA) and the expression of inflammatory factors in jejunum. The results showed that the diet supplemented with WZS could significantly reduce serum MPO, DAO, and D-LA levels and jejunal CD in broilers (p < 0.05), increase serum SOD levels and jejunal VH (p < 0.05), significantly downregulate the expression of NF-κB, TLR4, MyD88, and inflammatory cytokines (TNF-α, IL-1β, IL-6, and IL-10), and upregulate Claudin-1, Occludin-1, and ZO-1 in broiler jejunum mucosa (p < 0.05). On the other hand, WZS could significantly reduce the protein expression of NF-κB (p65) in broiler jejunum (p < 0.05). These results indicate that supplementing WZS in the diet can reduce intestinal inflammation and alleviate intestinal barrier damage, and by inhibiting the NF-κB/TLR4/MyD88 signaling pathway, supplementation with WZS intervenes in LPS-induced stress injury in broilers.

Dietary resveratrol supplementation on growth performance, immune function and intestinal barrier function in broilers challenged with lipopolysaccharide

This study discusses the effects of resveratrol (RES) on the productive performance, immune function and intestinal barrier function of broiler chickens challenged with lipopolysaccharide (LPS). Two hundred and forty 1-day-old male Arbor Acres broilers were randomly divided into 4 groups of 6 replicates each, with 10 broilers per replicate. This experiment used a 2 × 2 factorial design with dietary factors (basal diets or basal diets supplemented with 400 mg/kg RES were administered from d 1 to 21) and stress factors (intraperitoneal injection of 0.5 mg/kg BW of saline or LPS at 16, 18 and 20 d of age). The results showed that LPS challenge had a significant adverse effect on average daily gain (ADG) in broilers at 16 to 21 d of age (P < 0.05), whereas the addition of RES to the diet inhibited the LPS-induced decrease in ADG (P < 0.05). RES also alleviated LPS-induced immune function damage in broilers, which was manifested by the decrease of spleen index (P < 0.05) and the recovery of serum immunoglobulin M and ileal secretory immunoglobulin A content (P < 0.05). The LPS challenge also disrupts intestinal barrier function and inflammation, and RES mitigates these adverse effects in different ways. RES attenuated LPS-induced reduction of villus height in the jejunum and ileum of broilers (P < 0.05). LPS also caused an abnormal increase in plasma D-lactic acid levels in broilers (P < 0.05), which was effectively mitigated by RES (P < 0.05). LPS challenge resulted in a significant decrease in mRNA expression of occludin in the intestinal mucosa (P < 0.05), which was mitigated by the addition of RES (P < 0.05). RES significantly decreased the mRNA expression of toll-like receptor 4, nuclear factor kappa-B and tumor necrosis factor alpha in the ileum tissue stimulated by LPS (P < 0.05). Taken together, this study shows that RES exerts its beneficial effect on broilers challenged with LPS by alleviating immune function damage, relieving intestinal inflammation and barrier damage, and thus improving growth performance.

Effects of Sihuang Zhili Granules on the Diarrhea Symptoms, Immunity, and Antioxidant Capacity of Poultry Challenged with Lipopolysaccharide (LPS)

A growing interest has been focused on Chinese herbs as alternatives to antimicrobial growth promoters, which are characterized by non-toxic side effects and drug resistance. The purpose of this study was to evaluate the effects of the Sihuang Zhili granule (abbreviated as Sihuang) on diarrhea, immunity, and antioxidation in poultry. Thirty male Leghorn chickens, aged 21 days, were randomly assigned to one of three groups with ten animals each. The control group (CON) received intraperitoneal saline injections, while the LPS-challenged group (LPS) and Sihuang intervention group (SH) received intraperitoneal injections of LPS (0.5 mg/kg of BW) and Sihuang (5 g/kg) at d 31, d 33, d 35, respectively. The control and LPS groups were fed a basal diet, while the SH group was fed a diet supplemented with Sihuang from d 21 to d 35. Analysis of the diarrhea index showed that the addition of Sihuang inhibited the increase in the diarrhea grade and the fecal water content caused by LPS, effectively alleviating poultry diarrhea symptoms. The results of the immune and antioxidant indexes showed that Sihuang significantly reduced the contents of the pro-inflammatory factors TNF- α and IL-1 β, as well as the oxidative stress markers ROS and MDA. Conversely, it increased the contents of the anti-inflammatory factors IL-4 and IL-10, along with the activities of antioxidant enzymes GSH-Px and CAT, thereby enhancing the immune and antioxidant abilities of chickens. Furthermore, Sihuang protected the chicken's ileum, liver, and immune organs from LPS invasion and maintained their normal development. In conclusion, this study confirmed the antidiarrheal effect of Sihuang in poultry farming and demonstrated its ability to improve poultry immunity and antioxidant capacity by modulating antioxidant enzyme activity and inflammatory cytokine levels.

Artemisia ordosica polysaccharide ameliorated LPS-induced growth inhibition and intestinal injury in broilers through enhancing immune-regulation and antioxidant capacity

The study investigated the effects of dietary Artemisia ordosica polysaccharide (AOP) on growth, intestinal morphology, immune responses and antioxidant capacity of broilers challenged with lipopolysaccharide (LPS). A total of 192 1-d-old broilers were randomly allotted to four treatments with 6 replicates (n = 8): (1) CON group, non-challenged broilers fed basal diet; (2) LPS group, LPS-challenged broilers fed basal diet; (3) AOP group, non-challenged broilers fed basal diet supplemented with 750 mg/kg AOP; (4) LPS+AOP group, LPS-challenged broilers fed basal diet supplemented with 750 mg/kg AOP. The trial included starter phase (d 1 to 14), stress period Ⅰ (d 15 to 21), convalescence Ⅰ (d 22 to 28), stress period Ⅱ (d 29 to 35) and convalescence Ⅱ (d 36 to 42). During stress period Ⅰ and Ⅱ, broilers were injected intra-abdominally either with LPS solution or with equal sterile saline. The results showed that AOP alleviated LPS-induced growth inhibition by prompting protein digestibility, and decreasing serum stress hormones and pro-inflammatory cytokines content of broilers. Moreover, AOP decreased LPS-induced over-production of IL-1β and IL-6 through suppressing TLR4/NF-κB pathway, and alleviated LPS-induced decreasing of T-AOC, CAT and GPx activities by activating Nrf2/Keap1 pathway, which ultimately improved jejunum morphology. In conclusion, AOP alleviated LPS-induced growth inhibition and intestinal damage by enhancing anti-inflammatory and antioxidant capacities of broilers.

Bacterial lipopolysaccharide with different administration routes affects intestinal mucosal morphological, immunological, and microbial barrier functions in goslings

The current study was conducted to evaluate the effects of different administration routes of bacterial lipopolysaccharide (LPS) on intestinal mucosal morphological, immunological, and microbial barrier functions in goslings. First, we compared intestinal villi morphology of goslings under intraperitoneal or oral LPS treatment through hematoxylin and eosin staining. Then, we determined the signatures of the microbiome in the ileum mucosa of goslings subjected to oral LPS treatment at 0, 2, 4, and 8 mg/kg BW by 16S sequencing, and analyzed the changes in intestinal barrier functions and permeability, levels of LPS in the ileum mucosa, plasma, and liver tissue, and the induced inflammatory response of Toll-like receptor 4 (TLR4). As a result, intraperitoneal LPS injection resulted in a thicker intestinal wall in the ileum within a short time, whereas villus height was less affected; in contrast, oral LPS treatment exerted a stronger influence on villus height but not on intestinal wall thickness. We also found that oral LPS treatment affected the structure of the intestinal microbiome, reflected by changes in the clustering of intestinal microbiota. The average abundance of Muribaculaceae showed an increasing trend with increasing LPS levels, and that of the genus Bacteroides decreased, compared with the control group. In addition, oral LPS treatment with 8 mg/kg BW affected the intestinal epithelial morphology, damage the mucosal immune barrier, downregulated the expression of tight junction proteins, increased circulating D-lactate levels, and stimulated the secretion of various inflammatory mediators and activation of the TLR4/MyD88/NFκB pathway. This study presented the injuries of intestinal mucosal barrier function induced by LPS challenges in goslings and provided a scientific model for searching the novel strategies to attenuate the immunological stress and gut injury caused by LPS.

Melatonin and inflammatory bowel disease: From basic mechanisms to clinical application

Inflammatory bowel disease is a chronic inflammatory disease and has periods of recurrence and remission. Improper immune responses to gut flora bacteria, along with genetic susceptibility, appear to be involved in causing this complex disease. It seems dysbiosis and oxidative stress may also be involved in IBD pathogenesis. A significant number of clinical studies have shown an interesting association between sleep disturbances and IBD. Studies in animal models have also shown that sleep deprivation has a significant effect on the pathogenesis of IBD and can aggravate inflammation. These interesting findings have drawn attention to melatonin, a sleep-related hormone. Melatonin is mainly produced by the pineal gland, but many tissues in the body, including the intestines, can produce it. Melatonin can have an interesting effect on the pathogenesis of IBD. Melatonin can enhance the intestinal mucosal barrier, alter the composition of intestinal bacteria in favor of bacteria with anti-inflammatory properties, regulate the immune response, alleviate inflammation and attenuate oxidative stress. It seems that, melatonin supplementation is effective in relieving inflammation and healing intestinal ulcers in IBD animal models. Some clinical studies have also shown that melatonin supplementation as an adjuvant therapy may be helpful in reducing disease activity in IBD patients. In this review article, in addition to reviewing the effects of sleep disturbances and melatonin on key mechanisms involved in the pathogenesis of IBD, we will review the findings of clinical studies regarding the effects of melatonin supplementation on IBD treatment.

Tea tree oil nanoliposomes: optimization, characterization, and antibacterial activity against Escherichia coli in vitro and in vivo

The purpose of this study was to formulate tee tree oil nanoliposomes (TTONL) and evaluate its characterization and antibacterial activity. TTONL was prepared by thin film hydration and sonication technique, and the preparation conditions were optimized by Box-behnken response surface method. The characterization (morphology, size, zeta potential, and stability) and antibacterial activity of TTONL against Escherichia coli (E. coli) in vitro and in vivo were evaluated. The optimal preparation conditions for TTONL: lecithin to cholesterol mass ratio of 3.7:1, TTO concentration of 0.5%, and pH of the hydration medium of 7.4, which resulted in a TTONL encapsulation rate of 80.31 ± 0.56%. TTONL was nearly spherical in shape and uniform in size, and the average particle size was 227.8 ± 25.3 nm with negative charge. The specific disappearance of the TTO peak in the infrared spectrum suggested the successful preparation of TTONL, which showed high stability at 4°C within 35 d. The result of MIC test found that the nanoliposomes improved antibacterial activity of TTO against various E. coli strains. TTONL exposure in vitro caused different degrees of structural damage to the E. coli. TTONL by oral administration alleviated the clinical symptoms and intestinal lesion of chickens induced with E. coli challenge. Furthermore, TTONL treatment remarkably lowered the mRNA expression of NLRP3 and NF-κB (p65) in the duodenum and cecum of E. coli-infected chickens. In conclusion, the prepared TTONL had good stability and slow-release property with dose-dependent inhibition and killing effects on different strains of E. coli, and exerted a preventive role against chicken colibacillosis through inhibition.

Dietary resistant starch ameliorating lipopolysaccharide-induced inflammation in meat ducks associated with the alteration in gut microbiome and glucagon-like peptide 1 signaling

Background

Consumption of resistant starch (RS) has been associated with various intestinal and systemic health benefits, but knowledge of its effects on intestinal health and inflammatory response in stressed birds is limited. Here, we examined how dietary RS supplementation from 12% raw potato starch (RPS) modulated inflammatory severity induced by lipopolysaccharide (LPS) in meat ducks.

Results

LPS administration at 14, 16, and 18 d (chronic challenge) decreased body weight (BW) and glucagon-like peptide 1 receptor (GLP-1R) level with higher intestinal permeability and inflammation, evident by higher pro-inflammatory cytokine levels. Dietary 12% RPS supplementation enhanced Claudin-1 and GLP-1R expression, along with lower levels of inflammatory factors in both ileum and serum. Microbiome analysis showed that RS treatment shifted microbial structure reflected by enriched the proportion of Firmicutes, Bifidobacterium, Ruminococcus, etc. Dietary RS addition also significantly increased the concentrations of propionate and butyrate during chronic LPS challenge. Furthermore, response to acute challenge, the ducks received 2 mg/kg BW LPS at 14 d had higher concentrations of serum endotoxins and inflammatory cytokines, as well as upregulated transcription of toll like receptor 4 (TLR4) in ileum when compared to control birds. Analogous to GLP-1 agonist liraglutide, dietary RS addition decreased endotoxins and inflammation cytokines, whereas it upregulated the GLP-1 synthesis related genes expression. Meanwhile, dietary RS supplementation suppressed the acute LPS challenge-induced TLR4 transcription.

Conclusions

These data suggest that dietary 12% RPS supplementation could attenuate the LPS-induced inflammation as well as intestinal injury of meat ducks, which might involve in the alteration in gut microbiota, SCFAs production and the signaling pathways of TLR4 and GLP-1/GLP-1R.

Supplementary Information

The online version contains supplementary material available at 10.1186/s40104-022-00735-x.

Melatonin Alleviates Neonatal Necrotizing Enterocolitis by Repressing the Activation of the NLRP3 Inflammasome

Objective

Necrotizing enterocolitis (NEC) is one of the commonest gastrointestinal critical diseases in newborns. Several researches have proven the efficacy of melatonin (MEL) on NEC, but the latent mechanisms were ambiguous. We designed the current research to evaluate the function and mechanism of MEL on NEC in a neonatal mouse model.

Methods

The newborn mice were subjected to formula milk containing LPS and hypoxia to establish a NEC model and also intraperitoneally injected with MEL. During the experiment, all mice were closely monitored and weighed. The effect of MEL on the histopathological injury of the terminal ileum tissues, inflammation, and oxidative stress of serum in NEC mice was examined by hematoxylin-eosin (H&E) staining and ELISA. The effect of MEL on the NOD-like receptor family pyrin domain containing 3 (NLRP3) inflammasome was assessed via quantitative real-time PCR and Western blot.

Results

MEL intensified the survival rate and body weight in NEC mice. The H&E staining illustrated that MEL improved the histopathological injury in NEC mice. Moreover, MEL repressed the IL-1β, TNF-α, and MDA levels of serum and enhanced the SOD and GSH-Px levels of serum in NEC mice. We also discovered that MEL attenuated the mRNA and protein levels of NLRP3, Toll-like Receptor 4 (TLR4), NF-κB, and caspase-1 of the terminal ileum tissues in NEC mice.

Conclusion

Our research illuminated that MEL attenuated the severity of NEC via weakening the activation of the NLRP3 inflammasome.

Gut Microbiota Dysbiosis Aggravates Mycoplasma gallisepticum Colonization in the Chicken Lung

Mycoplasma gallisepticum (MG) is the pathogen that causes chronic respiratory diseases in chickens. Gut microbiota plays an important role in maintaining body health and resisting respiratory infection, but the correlation between gut microbiota and MG infection is poorly defined. Therefore, in this study, the correlation between gut microbiota and MG infection was explored by disturbing gut microbiota in chickens with antibiotic cocktail. The results showed that the gut microbiota dysbiosis impairs pulmonary immune response against MG infection. It has been noted that MG colonization in the lung was significantly increased following gut microbiota dysbiosis, and this could be reversed by intranasally administrated toll-like receptor 2 (TLR2) ligand, recombinant chicken IL-17 protein or recombinant chicken granulocyte-macrophage colony-stimulating factor (GM-CSF) protein. In addition, the levels of short-chain fatty acids (SCFAs) and vitamin A were significantly reduced in gut microbiota dysbiosis group, however, butyric acid or vitamin A as feed additives promoted MG clearance in the lung of gut microbiota dysbiosis group via increasing TLR2/IL17/GM-CSF and host defense peptides genes expression. The present study revealed an important role of gut microbiota in the defense against MG colonization in the lung of chicken.

Pyrroloquinoline-Quinone Is More Than an Antioxidant: A Vitamin-like Accessory Factor Important in Health and Disease Prevention

Pyrroloquinoline quinone (PQQ) is associated with biological processes such as mitochondriogenesis, reproduction, growth, and aging. In addition, PQQ attenuates clinically relevant dysfunctions (e.g., those associated with ischemia, inflammation and lipotoxicity). PQQ is novel among biofactors that are not currently accepted as vitamins or conditional vitamins. For example, the absence of PQQ in diets produces a response like a vitamin-related deficiency with recovery upon PQQ repletion in a dose-dependent manner. Moreover, potential health benefits, such as improved metabolic flexibility and immuno-and neuroprotection, are associated with PQQ supplementation. Here, we address PQQ's role as an enzymatic cofactor or accessory factor and highlight mechanisms underlying PQQ's actions. We review both large scale and targeted datasets demonstrating that a neonatal or perinatal PQQ deficiency reduces mitochondria content and mitochondrial-related gene expression. Data are reviewed that suggest PQQ's modulation of lactate acid and perhaps other dehydrogenases enhance NAD+-dependent sirtuin activity, along with the sirtuin targets, such as PGC-1α, NRF-1, NRF-2 and TFAM; thus, mediating mitochondrial functions. Taken together, current observations suggest vitamin-like PQQ has strong potential as a potent therapeutic nutraceutical.

Maternal stevioside supplementation ameliorates intestinal mucosal damage and modulates gut microbiota in chicken offspring challenged with lipopolysaccharide

Our previous study showed that dietary stevioside supplementation could alleviate intestinal mucosal damage induced by lipopolysaccharide (LPS) through its anti-inflammatory and antioxidant effects in broiler chickens. However, it remains unknown whether feeding stevioside to breeder hens could exert similar biological functions in their offspring. The present study aimed to investigate whether maternal dietary stevioside supplementation could prevent LPS-induced intestinal mucosal damage and alteration of gut microbiota in chicken offspring. A total of 120 Jinmao yellow-feathered breeder hens were fed a basal diet (CON) or a 250 mg kg^-1 stevioside-supplemented diet (STE) for 5 weeks before collecting their eggs. After hatching, 160 male offspring (80 chickens from each group) were randomly selected and divided into four treatment groups: (1) the offspring of hens fed a basal diet (CON); (2) the offspring of hens fed a stevioside-supplemented diet (STE); (3) the CON group challenged with LPS (LPS); and (4) the STE group challenged with LPS (LSTE). The results showed that maternal stevioside supplementation increased the hatching weight and improved the intestinal morphology. LPS challenge significantly decreased the terminal body weight and the concentrations of serum triglyceride (TG) and glucose (GLU) of the chicken offspring. Maternal stevioside supplementation protected against LPS-induced morphological damage, goblet cell impairment, intestinal apoptosis, and gene expression alteration. In addition, sequence analysis of 16S rRNA gene showed that maternal stevioside supplementation could prevent the impairment of bacterial diversity in LPS-challenged chicken offspring. Moreover, the increased abundance of Lactobacillus caused by maternal stevioside supplementation had a significant negative correlation with the expression of intestinal inflammatory cytokines. In conclusion, maternal stevioside supplementation could ameliorate intestinal mucosal damage and modulate gut microbiota in chicken offspring challenged with LPS.

Lactobacillus reuteri-derived extracellular vesicles maintain intestinal immune homeostasis against lipopolysaccharide-induced inflammatory responses in broilers

BACKGROUND

Lactobacillus reuteri strains are widely used as probiotics to prevent and treat inflammatory bowel disease by modulating the host's immune system. However, the underlying mechanisms by which they communicate with the host have not been clearly understood. Bacterial extracellular vesicles (EVs) have been considered as important mediators of host-pathogen interactions, but their potential role in commensals-host crosstalk has not been widely studied. Here, we investigated the regulatory actions of EVs produced by L. reuteri BBC3, a gut-associated commensal bacterium of Black-Bone chicken, in the development of lipopolysaccharide (LPS)-induced intestinal inflammation in a chicken model using both in vivo and in vitro experiments.

RESULTS

L. reuteri BBC3 produced nano-scale membrane vesicles with the size range of 60-250 nm. Biochemical and proteomic analyses showed that L. reuteri BBC3-derived EVs (LrEVs) carried DNA, RNA and several bioactive proteins previously described as mediators of other probiotics' beneficial effects such as glucosyltransferase, serine protease and elongation factor Tu. In vivo broiler experiments showed that administration of LrEVs exerted similar effects as L. reuteri BBC3 in attenuating LPS-induced inflammation by improving growth performance, reducing mortality and decreasing intestinal injury. LrEVs suppressed the LPS-induced expression of pro-inflammatory genes (TNF-α, IL-1β, IL-6, IL-17 and IL-8), and improved the expression of anti-inflammatory genes (IL-10 and TGF-β) in the jejunum. LrEVs could be internalized by chicken macrophages. In vitro pretreatment with LrEVs reduced the gene expression of TNF-α, IL-1β and IL-6 by suppressing the NF-κB activity, and enhanced the gene expression of IL-10 and TGF-β in LPS-activated chicken macrophages. Additionally, LrEVs could inhibit Th1- and Th17-mediated inflammatory responses and enhance the immunoregulatory cells-mediated immunosuppression in splenic lymphocytes of LPS-challenged chickens through the activation of macrophages. Finally, we revealed that the reduced content of both vesicular proteins and nucleic acids attenuated the suppression of LrEVs on LPS-induced inflammatory responses in ex vivo experiments, suggesting that they are essential for the LrEVs-mediated immunoregulation.

CONCLUSIONS

We revealed that LrEVs participated in maintaining intestinal immune homeostasis against LPS-induced inflammatory responses in a chicken model. Our findings provide mechanistic insight into how commensal and probiotic Lactobacillus species modulate the host's immune system in pathogens-induced inflammation.

MiR-339 attenuates LPS-induced intestinal epithelial cells inflammatory responses and apoptosis by targeting TLR4

BACKGROUND

Intestinal epithelial cells are important for defending against pathogen infection. LPS is an endotoxin that is highly antigenic and cytotoxic produced by bacteria. LPS disrupts the intestine epithelium integrity and induced the intestinal epithelial cell inflammation and apoptosis. Our previous study has predicted the function of exosome miRNAs through bioinformatics analysis, and we found that miR-339 had a potential function in cell inflammation response. To our knowledge, no published paper has demonstrated the miR-339 function in protecting the intestine epithelium against bacterial infection.

OBJECTIVE

The objective of this study is to evaluate the miR-339 function in regulating intestinal epithelial cells to defend against bacterial infection through biological experiments and bioinformatics analyses.

METHODS

Through the miR-339 transfection experiment and TLR4 interfering experiment, we evaluated the function of miR-339 and TLR4 in the process of inflammatory responses and apoptosis. Through Bioinformatics analyses and dual-luciferase reporter experiment, we identified the target gene of miR-339.

RESULTS

miR-339 attenuates LPS-induced intestinal epithelial cells inflammatory responses through the TLR4/NF-κB signaling pathway and inhibited LPS-induced apoptosis through the P53 signaling pathway. TLR4 is the target gene of miR-339. TLR4 reduced LPS-induced proinflammatory responses and apoptosis.

CONCLUSIONS

In conclusion, miR-339 protected the intestine epithelial cells from LPS-induced cell inflammation and apoptosis through targeting TLR4. This study expanded our understanding of how miRNAs and genes work collaboratively in regulating intestinal epithelial cells to defend against bacterial infection.

Riemerella anatipestifer infection affects intestinal barrier structure and immune reactions in the duck caecum

Riemerella anatipestifer (RA) infection causes high mortality and poor feed conversion, leading to great economic losses to the duck industry. This study investigated the effects of RA on the intestinal morphology and immune response of ducks. Histological examination showed that RA infection caused intestinal injury, including significantly reduced mucosal thickness on days 2, 3 and 5, significantly reduced villus height on days 1, 2, 3 and 5 (P < 0.05) and significantly reduced villus height to crypt depth ratios on days 2, 3, 5 and 9 of RA infection (P < 0.05). The expression of intestinal mucosal layer construction-associated genes and tight junction genes was significantly altered on at least one time point (day 1, 2, 3, 5, 9 or 14) after RA infection. Quantitative real-time polymerase chain reaction revealed that RA infection affected intestinal mucosal immune function. The genes encoding TLR4 (toll like receptor-4), TRAF6 (TNF receptor-associated factor 6), MYD88 (myeloid differentiation factor 88), IFN-γ (interferon-γ), IL (interleukin)-4 and IL-8 were significantly upregulated on day 2 of RA infection. Taken together, these results indicate that RA infection negatively affects intestinal barrier function in ducks due to impaired mucosal and villus-crypt structure and alters the mRNA expression of mucous layer construction-, intestinal tight junction-, and intestinal mucosal immunity-related genes.

Intestinal Ca2+ absorption revisited: A molecular and clinical approach

Ca2+ has an important role in the maintenance of the skeleton and is involved in the main physiological processes. Its homeostasis is controlled by the intestine, kidney, bone and parathyroid glands. The intestinal Ca2+ absorption occurs mainly via the paracellular and the transcellular pathways. The proteins involved in both ways are regulated by calcitriol and other hormones as well as dietary factors. Fibroblast growth factor 23 (FGF-23) is a strong antagonist of vitamin D action. Part of the intestinal Ca2+ movement seems to be vitamin D independent. Intestinal Ca2+ absorption changes according to different physiological conditions. It is promoted under high Ca2+ demands such as growth, pregnancy, lactation, dietary Ca2+ deficiency and high physical activity. In contrast, the intestinal Ca2+ transport decreases with aging. Oxidative stress inhibits the intestinal Ca2+ absorption whereas the antioxidants counteract the effects of prooxidants leading to the normalization of this physiological process. Several pathologies such as celiac disease, inflammatory bowel diseases, Turner syndrome and others occur with inhibition of intestinal Ca2+ absorption, some hypercalciurias show Ca2+ hyperabsorption, most of these alterations are related to the vitamin D endocrine system. Further research work should be accomplished in order not only to know more molecular details but also to detect possible therapeutic targets to ameliorate or avoid the consequences of altered intestinal Ca2+ absorption.

Dihydromyricetin attenuates Escherichia coli lipopolysaccharide-induced ileum injury in chickens by inhibiting NLRP3 inflammasome and TLR4/NF-κB signalling pathway

Lipopolysaccharide (LPS) as a major component of Escherichia coli cell wall can cause inflammation and cell death. Dihydromyricetin (ampelopsin, DHM) is a natural flavonoid compound with anti-inflammatory, anti-oxidant and anti-bacterial effects. The preventive effects of DHM against ileum injury remain unclear. Here, we explored the protective role of DHM against LPS-induced ileum injury in chickens. In this study, DHM significantly attenuated LPS-induced alteration in diamine oxidase, malondialdehyde, reduced glutathione, glutathione peroxidase and superoxide dismutase levels in chicken plasma and ileum. Histology evaluation showed that the structure of blood vessels in ileum was seriously fragmented and presence of necrotic tissue in the lumen in the LPS group. Scanning electron microscopic observation revealed that the surface of the villi was rough and uneven, the structure was chaotic, and the normal finger shape was lost in the LPS group. In contrast, 0.05% and 0.1% DHM treatment partially alleviated the abnormal morphology. Additionally, DHM maintained the barrier function by restoring the protein expression of occludin, claudin-1 and zonula occludens protein-1. DHM inhibited apoptosis through the reduction of the expression of bax and caspase-3 and restored the expression of bcl-2. Importantly, DHM could reduce ileum NLR family pyrin domain-containing 3 (NLRP3), caspase-1, interleukin (IL)-1β and IL-18 expression to protect tissues from pyroptosis and inhibited toll-like receptor 4 (TLR4)/nuclear factor kappa-B (NF-κB) signalling pathway. In summary, DHM attenuated the ileum mucosal damage, oxidative stress and apoptosis, maintained barrier function, inhibited NLRP3 inflammasome and TLR4/NF-κB signalling pathway activation triggered by Escherichia coli LPS.

Dietary Stevioside Supplementation Alleviates Lipopolysaccharide-Induced Intestinal Mucosal Damage through Anti-Inflammatory and Antioxidant Effects in Broiler Chickens

The study was conducted to investigate the effects of dietary stevioside (STE) supplementation on the lipopolysaccharide (LPS)-induced intestinal mucosal damage of broiler chickens. A total of 192 one-day-old male Ross 308 broiler chicks were randomly divided into four treatments: (1) basal diet (CON); (2) basal diet supplemented with 250 mg/kg stevioside (STE); (3) basal diet + LPS-challenge (LPS); (4) basal diet supplemented with 250 mg/kg stevioside + LPS-challenge (LPS + STE). LPS-challenged groups received an intraperitoneal injection of LPS at 17, 19 and 21 d, whereas the CON and STE groups received a saline injection. The results showed that dietary STE supplementation normalized LPS-induced changes in protein expression of p-NF-κB and p-IκBα, mRNA expression of inflammatory genes (TLR4, NF-κB, and IFN-γ), tight junction-related genes (CLDN2, OCLN, and ZO-1), and antioxidant genes (Nrf2 and HO-1). LPS-induced decreases in serum diamine oxidase (DAO) level, villus height-to-crypt depth ratio, apoptotic index, and protein expression of proliferating cell nuclear antigen (PCNA) were reversed with dietary STE supplementation. Additionally, STE supplementation ameliorated the redox damage by reducing malondialdehyde (MDA) content and increasing total antioxidant capacity (T-AOC) and antioxidant enzyme activity. In conclusion, dietary stevioside supplementation could alleviate LPS-induced intestinal mucosal damage through anti-inflammatory and antioxidant effects in broiler chickens.

Porcine Milk Exosome MiRNAs Attenuate LPS-Induced Apoptosis through Inhibiting TLR4/NF-κB and p53 Pathways in Intestinal Epithelial Cells

Lipopolysaccharide (LPS) is a bacterial endotoxin that induces intestine inflammation. Milk exosomes improve the intestine and immune system development of newborns. This study aims to establish the protective mechanisms of porcine milk exosomes on the attenuation of LPS-induced intestinal inflammation and apoptosis. In vivo, exosomes prevented LPS-induced intestine damage and inhibited (p < 0.05) LPS-induced inflammation. In vitro, exosomes inhibited (p < 0.05) LPS-induced intestinal epithelial cells apoptosis (23% ± 0.4% to 12% ± 0.2%). Porcine milk exosomes also decreased (p < 0.05) the LPS-induced TLR4/NF-κB signaling pathway activation. Furthermore, exosome miR-4334 and miR-219 reduced (p < 0.05) LPS-induced inflammation through the NF-κB pathway and miR-338 inhibited (p < 0.05) the LPS-induced apoptosis via the p53 pathway. Cotransfection with these three miRNAs more effectively prevented (p < 0.05) LPS-induced cell apoptosis than these miRNAs individual transfection. The apoptosis percentage in the group cotransfected with the three miRNAs (14% ± 0.4%) was lower (p < 0.05) than that in the NC miRNA group (28% ± 0.5%), and also lower than that in each individual miRNA group. In conclusion, porcine milk exosomes protect the intestine epithelial cells against LPS-induced injury by inhibiting cell inflammation and protecting against apoptosis through the action of exosome miRNAs. The presented results suggest that the physiological amounts of miRNAs-enriched exosomes addition to infant formula could be used as a novel preventative measure for necrotizing enterocolitis.

Mitochondrial oxidative stress-induced brain and hippocampus apoptosis decrease through modulation of caspase activity, Ca2+ influx and inflammatory cytokine molecular pathways in the docetaxel-treated mice by melatonin and selenium treatments

Docetaxel (DOCE) is widely used to treat several types of glioblastoma. Adverse effects DOCE seriously limit its clinical use in several tissues. Its side effects on brain cortex and hippocampus have not been clarified yet. Limited data indicated a protective effect of melatonin (MLT) and selenium (SELEN) on DOCE-induced apoptosis, Ca²⁺ influx and mitochondrial reactive oxygen species (ROS) in several tissues except brain and hippocampus. The purpose of this study is to discover the protective effect of MLT and SELEN on DOCE-induced brain and hippocampus oxidative toxicity in mice. MLT and SELEN pretreatments significantly ameliorated acute DOCE-induced mitochondrial ROS production in the hippocampus and brain tissues by reducing levels of lipid peroxidation, intracellular ROS production and mitochondrial membrane depolarization, while increasing levels of total antioxidant status, glutathione, glutathione peroxidase, MLT, α-tocopherol, γ-tocopherol, vitamin A, vitamin C and β-carotene in the tissues. Furthermore, MLT and SELEN pretreatments increased cell viability and TRPM2 channel activation in the hippocampus and brain followed by decreased activations of TNF-α, IL-1β, IL-6, and caspase -3 and - 9, suggesting a suppression of calcium ion influx, apoptosis and inflammation responses. However, modulator role of SELEN on the values in the tissues is more significant than in the MLT treatment. MLT and SELEN prevent DOCE-induced hippocampus and brain injury by inhibiting mitochondrial ROS and cellular apoptosis through regulating caspase -3 and - 9 activation signaling pathways. MLT and SELEN may serve as potential therapeutic targets against DOCE-induced toxicity in the hippocampus and brain.

Melatonin Improves Laying Performance by Enhancing Intestinal Amino Acids Transport in Hens

The high concentration of melatonin (MEL) in the intestinal mucosa suggests that it has a special physiological function in intestine. In hens, previous studies have shown that MEL treatment promoted egg-laying performance. Considering the importance of amino acids (AA) for egg formation, we hypothesized that MEL may enhance the intestinal absorption of AA from the feed, thus promoting egg laying performance. In this study, we supplemented the hens with MEL for two consecutive weeks. The results showed that, compared with control group, feeding with 0.625 mg MEL/kg diets gave rise to higher egg laying rate (by 4.3%, P = 0.016), increased eggshell thickness (by 16.9%, P < 0.01) and albumen height (by 4.5%, P = 0.042). Meanwhile, feeding with 0.625 and 2.5 mg MEL/kg diets could significantly increase serum levels of aspartic acid, threonine, serine, glutamic acid, glycine, alanine, isoleucine, leucine, tyrosine, phenylalanine, lysine, histidine, arginine, and proline. Furthermore, a 0.625 mg MEL/kg diets could significantly increase the expression of PepT1 (by 3949.9%), B⁰AT (by 6045.9%), b^{0, +}AT (by 603.5%), and EAAT3 (by 412.7%) in the jejunum. Additionally, in the cultured intestinal crypt "organoids," treatment with 0.5 μM MEL could significantly enhance the expression of PepT1, b^{0, +}AT and EAAT3 mRNAs by 35.4%, 110.0%, and 160.1%, respectively. Detection of MEL concentration in serum and intestinal fluid suggested that lower dosage of MEL feeding was mainly acted on intestine locally, and further increased intestinal antioxidases (GPx-3, SOD-1 or PRDX-3) mRNA expression. Taken together, we demonstrated that MEL feeding in laying hens could locally promote the expression and function of AA transporter in small intestine by up-regulating antioxidases expression, and finally elevate laying performance.