Methionine deficiency reduces autophagy and accelerates death in intestinal epithelial cells infected with enterotoxigenic Escherichia coli

The Hydrophobic Amino Acid-Rich Fish Collagen Peptide Ameliorates Dextran Sulfate Sodium-Induced Ulcerative Colitis in Mice via Repairing the Intestinal Barrier, Regulating Intestinal Flora and AA Metabolism

The incidence of ulcerative colitis (UC) is increasing annually, but treatment option is limited. Fish collagen peptide (FCP) is a food source collagen peptide that has shown promise in alleviating UC symptoms. However, its impact on the intestinal barrier and intestinal metabolic homeostasis in UC remains unclear. This study aimed to analyze the peptide sequences and absolute amino acid (AA) content of FCP, assessing its effects on UC in mice induced by dextran sulfate sodium (DSS). FCP was examined by liquid chromatography and tandem mass spectrometry (LC-MS/MS) analysis. The 3% DSS was utilized to induce UC in murine models, followed by the assessment of the therapeutic efficacy of FCP. Clinical manifestations of UC mice were meticulously evaluated and scored. Subsequently, samples were procured for histological examination and intestinal epithelial barrier integrity analysis as well as macrogenomic and metabolomic profiling. Here, it shows that abundant peptide sequences and AAs were in FCP, particularly enriched in hydrophobic AAs (HAAs). Furthermore, it was observed that FCP effectively reversed colon shortening and reduced the extent of histological damage. Additionally, FCP suppressed the abnormal expression of inflammatory factors and intestinal barrier proteins and modulated the dysbiosis of gut microbiota toward a balanced state. These alterations led to the activation of intestinal alkaline AA and various AA metabolisms, ultimately contributing to the mitigation of UC symptoms. In summary, the diverse peptide sequences and high AAs in FCP, particularly rich in HAAs, can alleviate DSS-induced UC via preserving intestinal barrier integrity, regulating gut microbiota, and modulating AA metabolism.

Butyrate ameliorated ferroptosis in ulcerative colitis through modulating Nrf2/GPX4 signal pathway and improving intestinal barrier

Oxidative stress and intestinal inflammation are main pathological features of ulcerative colitis (UC). Ferroptosis, characterized by iron accumulation and lipid peroxidation, is closely related to the pathologic process of UC. 16S rRNA sequencing for intestinal microbiota analysis and gas chromatography-mass spectrometry (GC-MS) for short-chain fatty acid (SCFA) contents clearly demonstrated lower amounts of butyrate-producing bacteria and butyrate in colitis mice. However, the precise mechanisms of sodium butyrate (NaB) in treating UC remain largely unclear. We found that ferroptosis occurred in colitis models, as evidenced by the inflammatory response, intracellular iron level, mitochondria ultrastructural observations and associated protein expression. NaB inhibited ferroptosis in colitis, significantly rescued weight loss and colon shortening in mice and reduced inflammatory lesions and mitochondrial damage. Furthermore, NaB improved intestinal barrier integrity and markedly suppressed the expression of pro-ferroptosis proteins. Conversely, the protein expression of anti-ferroptosis markers including nuclear factor erythroid-related Factor 2 (Nrf2) and glutathione peroxidase 4 (GPX4), was significantly upregulated with NaB treatment. Moreover, the knockdown of Nrf2 reversed the anti-colitis effect of NaB. Taken together, NaB exhibited a protective effect by ameliorating ferroptosis in experimental colitis through Nrf2/GPX4 signaling and improving intestinal barrier integrity, which provides a novel mechanism for NaB prevention of UC.

Effects of Enterotoxigenic Escherichia coli Challenge on Jejunal Morphology and Microbial Community Profiles in Weaned Crossbred Piglets

Pathogenic enterotoxigenic Escherichia coli (ETEC) is a major cause of bacterial diarrhea in weaning piglets, which are vulnerable to changes in environment and feed. This study aimed to determine the effects of the ETEC challenge on piglet growth performance, diarrhea rate, jejunal microbial profile, jejunal morphology and goblet cell distribution. A total of 13 piglets from one litter were selected on postnatal day 21 and assigned to treatments with or without ETEC challenge at 1 × 108 CFUs, as ETEC group or control group, respectively. On postnatal day 28, samples were collected, followed by the detection of serum biochemical indexes and inflammatory indicators, HE staining, PAS staining and 16S rDNA gene amplicon sequencing. Results showed that the growth performance decreased, while the diarrhea rate increased for the ETEC group. The jejunum is the main segment of the injured intestine during the ETEC challenge. Compared with the control, the ETEC group displayed fewer goblet cells in the jejunum, where goblet cells are more distributed at the crypt and less distributed at the villus. In addition, ETEC piglets possessed higher abundances of the genus Desulfovibrio, genus Oxalobacter and genus Peptococus and lower abundances of the genus Prevotella 2, genus Flavonifractor and genus Blautra. In terms of alpha diversity, Chao 1 and observed features indexes were both increased for the ETEC group. Our study provides insights into jejunal histopathological impairment and microbial variation in response to ETEC infection for weaned piglets and is a valuable reference for researchers engaged in animal health research to select stress models.

The Underlying Changes in Serum Metabolic Profiles and Efficacy Prediction in Patients with Extensive Ulcerative Colitis Undergoing Fecal Microbiota Transplantation

(1) Background: Fecal microbiota transplantation (FMT) is an effective treatment for ulcerative colitis (UC). Metabolomic techniques would assist physicians in clinical decision-making. (2) Methods: Patients with active UC undergoing FMT were enrolled in the study and monitored for 3 months. We explored short-term changes in the serum metabolic signatures of groups and the association between baseline serum metabolomic profiles and patient outcomes. (3) Results: Forty-four eligible patients were included in the analysis. Of them, 50.0% and 29.5% achieved clinical response and clinical remission, respectively, 3 months post-FMT. The top two significantly altered pathways in the response group were vitamin B6 metabolism and aminoacyl-tRNA biosynthesis. Both the remission and response groups exhibited an altered and enriched pathway for the biosynthesis of primary bile acid. We found a clear separation between the remission and non-remission groups at baseline, characterized by the higher levels of glycerophosphocholines, glycerophospholipids, and glycerophosphoethanolamines in the remission group. A random forest (RF) classifier was constructed with 20 metabolic markers selected by the Boruta method to predict clinical remission 3 months post-FMT, with an area under the curve of 0.963. (4) Conclusions: FMT effectively induced a response in patients with active UC, with metabolites partially improving post-FMT in the responsive group. A promising role of serum metabolites in the non-invasive prediction of FMT efficacy for UC demonstrated the value of metabolome-informed FMT in managing UC.

Resveratrol alleviates enterotoxigenic Escherichia coli K88-induced damage by regulating SIRT-1 signaling in intestinal porcine epithelial cells

This study found that resveratrol pretreatment attenuated porcine intestinal epithelial cell damage caused by enterotoxigenic Escherichia coli (ETEC) K88 in vitro and the protective effects of resveratrol were associated with SIRT-1 signaling. ETEC K88 is a main intestinal pathogen for post-weaning diarrhea (PWD) in piglets. With the strict ban on antibiotics in animal feed, people are seeking effective antibiotic substitutes to protect the intestinal system against harmful pathogenic bacteria. This study was conducted to evaluate the effects of resveratrol, a natural plant polyphenol, on ETEC K88-induced cellular damage in porcine enterocytes and underlying mechanisms. Intestinal porcine epithelial cell line 1 (IPEC-1) cells, pretreated with or without resveratrol (30 μM, 4 h), were challenged with ETEC K88 (MOI = 1 : 10) for 3 h. The results showed that ETEC K88 infection induced severe damage and dysfunction in IPEC-1 cells, as evidenced by a reduced cell viability, decreased tight junctions, mitochondrial dysfunction, and autophagy. It is noteworthy that IPEC-1 cells pre-treated with resveratrol improved their capacity for resistance to most of these abnormal phenotypes caused by ETEC K88 infection. Furthermore, we found that the activation of SIRT-1 signaling was associated with the benefits of resveratrol, as demonstrated by EX-527, an inhibitor of SIRT-1, which reversed most of the protective effects of resveratrol. In conclusion, these results indicated that resveratrol could protect intestinal epithelial cells against ETEC K88 infection by activating SIRT-1 signaling. These findings provide new insights into the role of resveratrol in maintaining intestinal physiological functions.

Methionine deficiency and its hydroxy analogue influence chicken intestinal 3-dimensional organoid development

Methionine and its hydroxy analogue (MHA) have been shown to benefit mouse intestinal regeneration. The intestinal organoid is a good model that directly reflects the impact of certain nutrients or chemicals on intestinal development. Here, we aimed to establish a chicken intestinal organoid culture method first and then use the model to explore the influence of methionine deficiency and MHA on intestinal organoid development. The results showed that 125-μm cell strainer exhibited the highest efficiency for chicken embryo crypt harvesting. We found that transforming growth factor-β inhibitor (A8301) supplementation promoted enterocyte differentiation at the expense of the proliferation of intestinal stem cells (ISC). The mitogen-activated protein kinase p38 inhibitor (SB202190) promoted intestinal organoid formation and enterocyte differentiation but suppressed the differentiation of enteroendocrine cells, goblet cells and Paneth cells. However, the suppression of enteroendocrine cell and Paneth cell differentiation by SB202190 was alleviated at the presence of A8301. The glycogen synthase kinase 3 inhibitor (CHIR99021), valproic acid (VPA) alone and their combination promoted chicken intestinal organoid formation and enterocyte differentiation at the expense of the expression of Paneth cells and goblet cells. Chicken serum significantly improved organoid formation, especially in the presence of A8301, SB202190, CHIR99021, and VPA, but inhibited the differentiation of Paneth cells and enteroendocrine cells. Chicken serum at a concentration of 0.25% meets the requirement of chicken intestinal organoid development, and the beneficial effect of chicken serum on chicken intestinal organoid culture could not be replaced by fetal bovine serum and insulin-like growth factor-1. Moreover, commercial mouse organoid culture medium supplemented with A8301, SB202190, CHIR99021, VPA, and chicken serum promotes chicken organoid budding. Based on the chicken intestinal organoid model, we found that methionine deficiency mimicked by cycloleucine suppressed organoid formation and organoid size, and this effect was reinforced with increased cycloleucine concentrations. Methionine hydroxy analogue promoted regeneration of ISC but decreased cell differentiation compared with the results obtained with L-methionine. In conclusion, our results provide a potentially excellent guideline for chicken intestinal organoid culture and insights into methionine function in crypt development.

Citral mitigates inflammation of Caco-2 cells induced by Cronobacter sakazakii

The aim of this study was to explore the anti-inflammatory effect and mechanism of citral in Cronobacter sakazakii-stimulated Caco-2 cells. Safe doses of citral were first determined in Caco-2 cells....

Dietary supplementation of fructooligosaccharides alleviates enterotoxigenic E. coli-induced disruption of intestinal epithelium in a weaned piglet model

Diarrhea caused by pathogens such as enterotoxigenic E. coli (ETEC) is a serious threat to the health of young animals and human infants. Here, we investigated the protective effect of fructooligosaccharides (FOS) on the intestinal epithelium with ETEC-challenge in a weaned piglet model. Twenty-four weaned piglets were randomly divided into three groups: (1) non-ETEC-challenged control (CON), (2) ETEC-challenged control (ECON), and (3) ETEC challenge + 2.5 g/kg FOS (EFOS). On day 19, the CON pigs were orally infused with sterile culture, while the ECON and EFOS pigs were orally infused with active ETEC (2.5 × 109 colony-forming units). On day 21, pigs were slaughtered to collect venous blood and small intestine. Result showed that the pre-treatment of FOS improved the antioxidant capacity and the integrity of intestinal barrier in the ETEC-challenged pigs without affecting their growth performance. Specifically, comparing with ECON pigs, the level of GSH-Px (glutathione peroxidase) and CAT (catalase) in the plasma and intestinal mucosa of EFOS pigs was increased (P<0.05), and the intestinal barrier marked by ZO-1 and plasmatic DAO was also improved in EFOS pigs. A lower level (P<0.05) of inflammatory cytokines in the intestinal mucosa of EFOS pigs might be involved in the inhibition of TLR4/MYD88/NF-κB pathway. The apoptosis of jejunal cells in EFOS pigs was also lower than that in ECON pigs (P<0.05). Our findings provide convincing evidence of possible prebiotic and protective effect of FOS on the maintenance of intestinal epithelial function under the attack of pathogens.

Research progress on diarrhoea and its mechanism in weaned piglets fed a high-protein diet

In order to pursue faster growth and development of weaned piglets, increased dietary protein (CP) levels were favoured by the pig industry and the feed industry. The digestive organs of piglets were not fully developed at weaning, and the digestive absorption capacity of protein was limited. High-protein diets can cause allergic reactions in piglets, destroy intestinal structural integrity, reduce immunity, and cause intestinal flora imbalance. Undigested proteins were prone to produce toxic substances, such as ammonia and biogenic amines, after fermentation in the hindgut, which negatively affects the health of the intestine and eventually causes reduced growth performance and diarrhoea in piglets. This review revealed the mechanism of diarrhoea caused by high-protein diets in weaned piglets and provided ideas for preventing diarrhoea in weaned piglets.

Functional Amino Acids and Autophagy: Diverse Signal Transduction and Application

Functional amino acids provide great potential for treating autophagy-related diseases by regulating autophagy. The purpose of the autophagy process is to remove unwanted cellular contents and to recycle nutrients, which is controlled by many factors. Disordered autophagy has been reported to be associated with various diseases, such as cancer, neurodegeneration, aging, and obesity. Autophagy cannot be directly controlled and dynamic amino acid levels are sufficient to regulate autophagy. To date, arginine, leucine, glutamine, and methionine are widely reported functional amino acids that regulate autophagy. As a signal relay station, mammalian target of rapamycin complex 1 (mTORC1) turns various amino acid signals into autophagy signaling pathways for functional amino acids. Deficiency or supplementation of functional amino acids can immediately regulate autophagy and is associated with autophagy-related disease. This review summarizes the mechanisms currently involved in autophagy and amino acid sensing, diverse signal transduction among functional amino acids and autophagy, and the therapeutic appeal of amino acids to autophagy-related diseases. We aim to provide a comprehensive overview of the mechanisms of amino acid regulation of autophagy and the role of functional amino acids in clinical autophagy-related diseases and to further convert these mechanisms into feasible therapeutic applications.

GABA attenuates ETEC-induced intestinal epithelial cell apoptosis involving GABAAR signaling and the AMPK-autophagy pathway

Enterotoxigenic Escherichia coli (ETEC) triggers diarrhea in humans and livestock. We have previously showed that ETEC promotes intestinal epithelial cell apoptosis and increases gamma-aminobutyric acid (GABA) concentration in the jejunum, suggesting that GABA might mediate ETEC-induced apoptosis. Here, we found that GABA alleviates ETEC-induced intestinal barrier dysfunctions, including ETEC-induced apoptosis both in vivo and in vitro. Interestingly, the alleviation of GABA on ETEC-induced apoptosis largely depends on autophagy. Mechanistically, GABA attenuates ETEC-induced apoptosis via activating GABA_AR signaling and the AMPK-autophagy pathway. These findings highlight that maintaining intestinal GABA concentration could alleviate intestinal ETEC infection.

The Role of Nrf2 Signaling Pathway in Eucommia ulmoides Flavones Regulating Oxidative Stress in the Intestine of Piglets

Eucommia ulmoides flavones (EUF) have been demonstrated to alleviate oxidative stress and intestinal damage in piglets, but their effect target is still poorly understood. NF-E2-related factor 2 (Nrf2) pathway plays a very important role in the defense mechanism. This study was designed to investigate the regulation of EUF on the Nrf2 pathway and inhibition of Nrf2 on oxidative stress in the intestine of piglets. An in vivo study was conducted in weaned piglets treated with basal diet, basal diet+diquat, and 100 mg/kg EUF diet+diquat for 14 d to determine Nrf2 and Keap1 protein expressions, as well as downstream antioxidant gene mRNA expression. An in vitro study was performed in a porcine jejunal epithelial cell line to investigate the effect of inhibiting Nrf2 on cell growth and intracellular oxidative stress parameters. The results showed that the supplementation of EUF decreased the oxidized glutathione (GSSG) concentration and the ratio of GSSG to glutathione (GSH) but increased the protein expressions of nuclear Nrf2 and Kelch-like ECH-associated protein 1 (Keap1) as well as mRNA expression of heme oxygenase 1 (HO-1), NAD(P)H:quinone oxidoreductase 1 (NQO-1), and glutamate cysteine ligase catalytic subunit (GCLC) in the small intestinal mucosa of diquat-challenged piglets. When Nrf2 was inhibited by using ML385, cell viability, cellular antioxidant activities, expressions of nuclear Nrf2 and Keap1 protein, and downstream antioxidant enzyme (HO-1, NQO-1, and GCLC) mRNA were decreased in paraquat-treated enterocytes. These results showed that the Nrf2 signaling pathway played an important role in EUF-regulating oxidative stress in the intestine of piglets.

Effects of methionine partially replaced by methionyl-methionine dipeptide on intestinal function in methionine-deficient pregnant mice

This study was to compare the effects of parenteral supplementation of methionyl-methionine (Met-Met) or Met on intestinal barrier function in Met-deficient pregnant mice. Pregnant mice were randomly divided into three groups. The Control group was provided a diet containing Met and received i.p. injection of saline. The Met group was fed the same diet but without Met and received daily i.p. injection of 35% of the Met contained in the control diet. The Met-Met group was treated the same as the Met group, except that 25% of the Met injected was replaced with Met-Met. Met-Met promoted villus surface area in ileum compared with Met alone. In addition, the mRNA abundance of amino acid and glucose transporters in the small intestine was altered with Met-Met. Moreover, Met-Met increased tight junction protein and decreased apoptosis-related proteins expression in the jejunum and ileum. These results suggest that Met-Met can promote intestinal function over Met alone in Met-deficient mice.

Effect of Puerarin, Baicalin and Berberine Hydrochloride on the Regulation of IPEC-J2 Cells Infected with Enterotoxigenic Escherichia coli

Puerarin, baicalin and berberine hydrochloride are the main components of Gegen Qinlian Decoction, which has been used to treat diarrhoea in China for hundreds of years, yet the biological function and molecular mechanism of these components are not clear. To investigate the effects of puerarin, baicalin, and berberine hydrochloride on the regulation of porcine intestinal epithelial cells (IPEC-J2 cells) infected with enterotoxigenic Escherichia coli (ETEC). IPEC-J2 cells were pretreated with puerarin (200 μg/mL), baicalin (1 μg/mL), and berberine hydrochloride (100 μg/mL) at 37°C for 3 h and then coincubated with the F4ac ETEC bacterial strain 200 at 37°C for 3 h. ETEC infection damaged the structure of IPEC-J2 cells, upregulated mucin 4 (P < 0.01) and mucin 13 mRNA (P < 0.05) expression, increased the apoptosis rate (P < 0.05), and promoted inflammatory responses (IL-6 and CXCL-2 mRNA expression) in IPEC-J2 cells by activating the nuclear factor-κB (NF-κB) signaling pathway. Pretreatment with puerarin, baicalin, and berberine hydrochloride improved the structure and morphology of IPEC-J2 cells and inhibited ETEC adhesion by downregulating specific adhesion molecules. Pretreatment with baicalin decreased the inflammatory response; pretreatment with baicalin and berberine hydrochloride decreased the inflammatory response mediated by the NF-κB signaling pathway. Pretreatment with puerarin, baicalin, and berberine hydrochloride protected IPEC-J2 cells from ETEC infection by inhibiting bacterial adhesion and inflammatory responses.

Implication of G Protein-Coupled Receptor 43 in Intestinal Inflammation: A Mini-Review

Short chain fatty acids (SCFAs, e.g., acetate, propionate, and butyrate) are a subset of fatty acids that are produced by gut microbiota during the fermentation of dietary fiber. They modulate different processes in the gastrointestinal tract and play various positive roles in mediating the intestinal health. Most beneficial roles of SCFAs in the gastrointestinal tract are mediated by directly activating its receptor, G protein-coupled receptor 43 (GPR43, also known as FFAR2). Various recent studies have demonstrated the role of GPR43 in intestinal inflammatory diseases, such as inflammatory bowel diseases. These SCFAs-mediated regulations of intestinal health are associated with neutrophil chemotaxis, T cell differentiation, activation, and subsequent cytokines production. Therefore, GPR43 could potentially be a drug target for intestinal inflammatory diseases. In this review, we review the current knowledge on the regulatory mechanisms associated with GPR43 in intestinal inflammation. The role of GPR43-mediated regulation of antibody responses is also discussed.

Amino Acids As Mediators of Metabolic Cross Talk between Host and Pathogen

The interaction between host and pathogen decidedly shapes the outcome of an infection, thus understanding this interaction is critical to the treatment of a pathogen-induced infection. Although research in this area of cell biology has yielded surprising findings regarding interactions between host and pathogen, understanding of the metabolic cross talk between host and pathogen is limited. At the site of infection, host and pathogen share similar or identical nutritional substrates and generate common metabolic products, thus metabolic cross talk between host and pathogen could profoundly affect the pathogenesis of an infection. In this review, we present results of a recent discovery of a metabolic interaction between host and pathogen from an amino acid (AA) metabolism-centric point of view. The host depends on AA metabolism to support defensive responses against pathogens, while the pathogens modulate AA metabolism for its own advantage. Some AA, such as arginine, asparagine, and tryptophan, are central points of competition between the host and pathogen. Thus, a better understanding of AA-mediated metabolic cross talk between host and pathogen will provide insight into fruitful therapeutic approaches to manipulate and prevent progression of an infection.

Nutrient sensing and metabolic changes after methionine deprivation in primary muscle cells of turbot (Scophthalmus maximus L.)

The low methionine content in plant-based diets is a major limiting factor for feed utilization by animals. However, the molecular consequences triggered by methionine deficiency have not been well characterized, especially in fish species, whose metabolism is unique in many aspects and important for aquaculture industry. In the present study, the primary muscle cells of turbot (Scophthalmus maximus L.) were isolated and treated with or without methionine for 12 h in culture. The responses of nutrient sensing pathways, the proteomic profiling of metabolic processes, and the expressions of key metabolic molecules were systematically examined. Methionine deprivation (MD) suppressed target of rapamycin (TOR) signaling, activated AMP-activated protein kinase (AMPK) and amino acid response (AAR) pathways. Reduced cellular protein synthesis and increased protein degradation by MD led to increased intracellular free amino acid levels and degradations. MD also reduced glycolysis and lipogenesis while stimulated lipolysis, thus resulted in decreased intracellular lipid pool. MD significantly enhanced energy expenditure through stimulated tricarboxylic acid (TCA) cycle and oxidative phosphorylation. Collectively, our results identified a comprehensive set of transcriptional, proteomic, and signaling responses generated by MD and provided the molecular insight into the integration of cell homeostasis and metabolic controls in fish species.

Therapeutic Potential of Amino Acids in Inflammatory Bowel Disease

Inflammatory bowel disease (IBD), which includes both ulcerative colitis and Crohn’s disease, is a chronic relapsing inflammation of the gastrointestinal tract, and is difficult to treat. The pathophysiology of IBD is multifactorial and not completely understood, but genetic components, dysregulated immune responses, oxidative stress, and inflammatory mediators are known to be involved. Animal models of IBD can be chemically induced, and are used to study etiology and to evaluate potential treatments of IBD. Currently available IBD treatments can decrease the duration of active disease but because of their adverse effects, the search for novel therapeutic strategies that can restore intestinal homeostasis continues. This review summarizes and discusses what is currently known of the effects of amino acids on the reduction of inflammation, oxidative stress, and cell death in the gut when IBD is present. Recent studies in animal models have identified dietary amino acids that improve IBD, but amino acid supplementation may not be adequate to replace conventional therapy. The animal models used in dietary amino acid research in IBD are described.

Roles of amino acids in preventing and treating intestinal diseases: recent studies with pig models

Animal models are needed to study and understand a human complex disease. Because of their similarities in anatomy, structure, physiology, and pathophysiology, the pig has proven its usefulness in studying human gastrointestinal diseases, such as inflammatory bowel disease, ischemia/reperfusion injury, diarrhea, and cancer. To understand the pathogenesis of these diseases, a number of experimental models generated in pigs are available, for example, through surgical manipulation, chemical induction, microbial infection, and genetic engineering. Our interests have been using amino acids as therapeutics in pig and human disease models. Amino acids not only play an important role in protein biosynthesis, but also exert significant physiological effects in regulating immunity, anti-oxidation, redox regulation, energy metabolism, signal transduction, and animal behavior. Recent studies in pigs have shown that specific dietary amino acids can improve intestinal integrity and function under normal and pathological conditions that protect the host from different diseases. In this review, we summarize several pig models in intestinal diseases and how amino acids can be used as therapeutics in treating pig and human diseases.

The different ecological niches of enterotoxigenic Escherichia coli

Enterotoxigenic Escherichia coli (ETEC) is a water and food-borne pathogen that infects the small intestine of the human gut and causes diarrhoea. Enterotoxigenic E. coli adheres to the epithelium by means of colonization factors and secretes two enterotoxins, the heat labile toxin and/or the heat stable toxin that both deregulate ion channels and cause secretory diarrhoea. Enterotoxigenic E. coli as all E. coli, is a versatile organism able to survive and grow in different environments. During transmission and infection, ETEC is exposed to various environmental cues that have an impact on survivability and virulence. The ability to cope with exposure to different stressful habitats is probably shaping the pool of virulent ETEC strains that cause both endemic and epidemic infections. This review will focus on the ecology of ETEC in its different habitats and interactions with other organisms as well as abiotic factors.

Co-dependence of genotype and dietary protein intake to affect expression on amino acid/peptide transporters in porcine skeletal muscle

A total of 96 barrows (48 pure-bred Bama mini-pigs representing fatty genotype, and 48 Landrace pigs representing lean genotype) were randomly assigned to either a low- or adequate-protein treatment diet. The experimental period commenced at 5 weeks of age and extended to the finishing period. After euthanasia, blood and skeletal muscle samples were collected from pigs at the nursery, growing, and finishing phases. Our results indicate that the concentrations of free AAs in the plasma and muscle decreased as the age of the pigs increased. In addition, a strain × growth phase interaction (P < 0.05) was observed for the free AA pool in the plasma and muscle. The low-protein diet upregulated (P < 0.05) the mRNA levels for T1R1/T1R3 involved in glutamate binding, but downregulated (P < 0.05) the mRNA levels for PAT1, PAT2, and ASCT2, which transport neutral AAs into muscles. Bama mini-pigs had higher (P < 0.05) mRNA levels for LAT1, SNAT2, and EAAC1, but a lower (P < 0.05) mRNA level for PepT1, compared with Landrace pigs. Collectively, our findings indicate that adequate provision of dietary protein plays an important role in regulating profiles of free AA pools and expression of key AA/peptide transporters/transceptors in a genotype- and tissue-specific manner.

Suppression of starvation-induced autophagy by recombinant toxic shock syndrome toxin-1 in epithelial cells

Toxic shock syndrome toxin-1 (TSST-1), a superantigen produced from Staphylococcus aureus, has been reported to bind directly to unknown receptor(s) and penetrate into non-immune cells but its function is unclear. In this study, we demonstrated that recombinant TSST-1 suppresses autophagosomal accumulation in the autophagic-induced HeLa 229 cells. This suppression is shared by a superantigenic-deficient mutant of TSST-1 but not by staphylococcal enterotoxins, suggesting that autophagic suppression of TSST-1 is superantigenic-independent. Furthermore, we showed that TSST-1-producing S. aureus suppresses autophagy in the response of infected cells. Our data provides a novel function of TSST-1 in autophagic suppression which may contribute in staphylococcal persistence in host cells.