Role of Glutamine in Protection of Intestinal Epithelial Tight Junctions

Elemental Diet as a Therapeutic Modality: A Comprehensive Review

Elemental diets have been employed for the management of various diseases for over 50 years, with several mechanisms mediating their beneficial effects. Yet, they are underutilized due to poor palatability, access, cost, and lack of awareness regarding their clinical efficacy. Therefore, in this review, we aimed to systematically search and review the literature to summarize the formulation variability, mechanisms of action, clinical applications, and tolerability of the elemental diets in gastrointestinal diseases. While large prospective trials are lacking, elemental diets appear to exhibit objective and subjective clinical benefit in several diseases, including eosinophilic esophagitis, eosinophilic gastroenteritis, inflammatory bowel diseases, small intestinal bacterial overgrowth, intestinal methanogen overgrowth, chemoradiotherapy-associated mucositis, and celiac disease. Although some data support the long-term use of elemental diets as an add-on supplement for chronic pancreatitis and Crohn's disease, most of the literature on exclusive elemental diets focuses on inducing remission. Therefore, subsequent treatment strategies for maintaining remission need to be adopted in chronic/relapsing diseases. Several mechanistic pathways were identified to mediate the effects of elemental diets, including food additive and allergen-free content, high passive absorption rate, and anti-inflammatory properties. High rates of intolerance up to 40% are seen in the trials where exclusive elemental diets were administered orally due to poor organoleptic acceptability; however, when tolerated, adverse events were rare. Other limitations of elemental diets are cost, access, and lifestyle/social restrictions. Moreover, judicious use is advised in presence of a concomitant restrictive food intake disorders. Elemental diets offer a potentially highly efficacious dietary intervention with minor side effects. Palatability, cost, access, and social restrictions are common barriers of use. Prospective clinical trials are needed to elucidate the role of elemental formulas in the management of individual diseases.

Sugar and arginine facilitate oral tolerance by ensuring the functionality of tolerogenic immune cell subsets in the intestine

Although oral tolerance is a critical system in regulating allergic disorders, the mechanisms by which dietary factors regulate the induction and maintenance of oral tolerance remain unclear. To address this, we explored the differentiation and function of various immune cells in the intestinal immune system under fasting and ad libitum-fed conditions before oral ovalbumin (OVA) administration. Fasting mitigated OVA-specific Treg expansion, which is essential for oral tolerance induction. This abnormality mainly resulted from functional defects in the CX3CR1+ cells responsible for the uptake of luminal OVA and reduction of tolerogenic CD103+ dendritic cells. Eventually, fasting impaired the preventive effect of oral OVA administration on asthma and allergic rhinitis development. Specific food ingredients, namely carbohydrates and arginine, were indispensable for oral tolerance induction by activating glycolysis and mTOR signaling. Overall, prior food intake and nutritional signals are critical for maintaining immune homeostasis by inducing tolerance to ingested food antigens.

Effect of dietary l-glutamine supplementation on the intestinal physiology and growth during Solea senegalensis larval development

The maturation of the intestinal digestive and absorptive functions might limit the amount of absorbed nutrients to fulfil the high requirements of the fast-growing marine fish larva. Glutamine (Gln) has been described to improve intestinal epithelium functions, due to its involvement in energy metabolism and protein synthesis. The purpose of this study was to evaluate dietary 0.2% Gln supplementation on aspects of intestinal physiology, protein metabolism and growth-related genes expression in Senegalese sole larvae. Experiment was carried out between 12 and 33 days post hatching (DPH) and fish were divided into two experimental groups, one fed Artemia spp. (CTRL) and the other fed Artemia spp. supplemented with Gln (GLN). GLN diet had two times more Gln than the CTRL diet. Samples were collected at 15, 19, 26 and 33 DPH for biometry, histology, and digestive enzymes activity, and at 33 DPH for gene expression, protein metabolism and AA content determination. Growth was significantly higher for Senegalese sole fed GLN diet, supported by differences on protein metabolism and growth-related gene expression. Slight differences were observed between treatments regarding the intestinal physiology. Overall, GLN diet seems to be directed to enhance protein metabolism leading to higher larval growth.

Sports-Related Gastrointestinal Disorders: From the Microbiota to the Possible Role of Nutraceuticals, a Narrative Analysis

Intense physical exercise can be related to a significant incidence of gastrointestinal symptoms, with a prevalence documented in the literature above 80%, especially for more intense forms such as running. This is in an initial phase due to the distancing of the flow of blood from the digestive system to the skeletal muscle and thermoregulatory systems, and secondarily to sympathetic nervous activation and hormonal response with alteration of intestinal motility, transit, and nutrient absorption capacity. The sum of these effects results in a localized inflammatory process with disruption of the intestinal microbiota and, in the long term, systemic inflammation. The most frequent early symptoms include abdominal cramps, flatulence, the urge to defecate, rectal bleeding, diarrhea, nausea, vomiting, regurgitation, chest pain, heartburn, and belching. Promoting the stability of the microbiota can contribute to the maintenance of correct intestinal permeability and functionality, with better control of these symptoms. The literature documents various acute and chronic alterations of the microbiota following the practice of different types of activities. Several nutraceuticals can have functional effects on the control of inflammatory dynamics and the stability of the microbiota, exerting both nutraceutical and prebiotic effects. In particular, curcumin, green tea catechins, boswellia, berberine, and cranberry PACs can show functional characteristics in the management of these situations. This narrative review will describe its application potential.

Intestinal macrophages in pathogenesis and treatment of gut leakage: current strategies and future perspectives

Macrophages play key roles in tissue homeostasis, defense, disease, and repair. Macrophages are highly plastic and exhibit distinct functional phenotypes based on micro-environmental stimuli. In spite of several advancements in understanding macrophage biology and their different functional phenotypes in various physiological and pathological conditions, currently available treatment strategies targeting macrophages are limited. Macrophages' high plasticity and diverse functional roles-including tissue injury and wound healing mechanisms-mark them as potential targets to mine for efficient therapeutics to treat diseases. Despite mounting evidence on association of gut leakage with several extraintestinal diseases, there is no targeted standard therapy to treat gut leakage. Therefore, there is an urgent need to develop therapeutic strategies to treat this condition. Macrophages are the cells that play the largest role in interacting with the gut microbiota in the intestinal compartment and exert their intended functions in injury and repair mechanisms. In this review, we have summarized the current knowledge on the origins and phenotypes of macrophages. The specific role of macrophages in intestinal barrier function, their role in tissue repair mechanisms, and their association with gut microbiota are discussed. In addition, currently available therapies and the putative tissue repair mediators of macrophages for treating microbiota dysbiosis induced gut leakage are also discussed. The overall aim of this review is to convey the intense need to screen for microbiota induced macrophage-released prorepair mediators, which could lead to the identification of potential candidates that could be developed for treating the leaky gut and associated diseases.

Glutamine Supplementation as an Anticancer Strategy: A Potential Therapeutic Alternative to the Convention

Glutamine, a multifaceted nonessential/conditionally essential amino acid integral to cellular metabolism and immune function, holds pivotal importance in the landscape of cancer therapy. This review delves into the intricate dynamics surrounding both glutamine antagonism strategies and glutamine supplementation within the context of cancer treatment, emphasizing the critical role of glutamine metabolism in cancer progression and therapy. Glutamine antagonism, aiming to disrupt tumor growth by targeting critical metabolic pathways, is challenged by the adaptive nature of cancer cells and the complex metabolic microenvironment, potentially compromising its therapeutic efficacy. In contrast, glutamine supplementation supports immune function, improves gut integrity, alleviates treatment-related toxicities, and improves patient well-being. Moreover, recent studies highlighted its contributions to epigenetic regulation within cancer cells and its potential to bolster anti-cancer immune functions. However, glutamine implementation necessitates careful consideration of potential interactions with ongoing treatment regimens and the delicate equilibrium between supporting normal cellular function and promoting tumorigenesis. By critically assessing the implications of both glutamine antagonism strategies and glutamine supplementation, this review aims to offer comprehensive insights into potential therapeutic strategies targeting glutamine metabolism for effective cancer management.

FNICM: A New Methodology To Identify Core Metabolites Based on Significantly Perturbed Metabolic Subnetworks

Metabolomics has emerged as a powerful tool in biomedical research to understand the pathophysiological processes and metabolic biomarkers of diseases. Nevertheless, it is a significant challenge in metabolomics to identify the reliable core metabolites that are closely associated with the occurrence or progression of diseases. Here, we proposed a new research framework by integrating detection-based metabolomics with computational network biology for function-guided and network-based identification of core metabolites, namely, FNICM. The proposed FNICM methodology is successfully utilized to uncover ulcerative colitis (UC)-related core metabolites based on the significantly perturbed metabolic subnetwork. First, seed metabolites were screened out using prior biological knowledge and targeted metabolomics. Second, by leveraging network topology, the perturbations of the detected seed metabolites were propagated to other undetected ones. Ultimately, 35 core metabolites were identified by controllability analysis and were further hierarchized into six levels based on confidence level and their potential significance. The specificity and generalizability of the discovered core metabolites, used as UC's diagnostic markers, were further validated using published data sets of UC patients. More importantly, we demonstrated the broad applicability and practicality of the FNICM framework in different contexts by applying it to multiple clinical data sets, including inflammatory bowel disease, colorectal cancer, and acute coronary syndrome. In addition, FNICM was also demonstrated as a practicality methodology to identify core metabolites correlated with the therapeutic effects of Clematis saponins. Overall, the FNICM methodology is a new framework for identifying reliable core metabolites for disease diagnosis and drug treatment from a systemic and a holistic perspective.

Safety and Suitability of Infant Formula Manufactured from Extensively Hydrolyzed Whey Protein Compared to Intact Protein: A Combined Analysis of Two Randomized Controlled Studies

Our aim was to assess the nutritional safety and suitability of an infant formula manufactured from extensively hydrolyzed protein in comparison to infant formula manufactured from intact protein (both with low and standard protein content). We performed a combined analysis of raw data from two randomized infant feeding studies. An analysis of covariance (ANCOVA) model was used to determine the non-inferiority of daily weight gain (primary outcome; margin -3 g/day), with the intervention group as a fixed factor and geographic region, sex, and baseline weight as covariates (main model). The data of 346 infants exposed to the formula were included in the analysis. The sample size of the per-protocol analysis with 184 infants was too small to achieve sufficient statistical power. The lower limit of the 97.5% confidence interval (-0.807) of the mean group difference in daily weight gain (i.e., 2.22 g/day) was above the -3 g/day margin (full analysis set). Further anthropometric parameters did not differ between the infant formula groups throughout the study. Growth was comparable to breastfed infants. We conclude that the infant formula manufactured from extensively hydrolyzed protein meets infant requirements for adequate growth and does not raise any safety concerns.

Research Progress on the Mechanism of Intestinal Barrier Damage and Drug Therapy in a High Altitude Environment

The plateau is a typical extreme environment with low temperature, low oxygen and high ultraviolet rays. The integrity of the intestinal barrier is the basis for the functioning of the intestine, which plays an important role in absorbing nutrients, maintaining the balance of intestinal flora, and blocking the invasion of toxins. Currently, there is increasing evidence that high altitude environment can enhance intestinal permeability and disrupt intestinal barrier integrity. This article mainly focuses on the regulation of the expression of HIF and tight junction proteins in the high altitude environment, which promotes the release of pro-inflammatory factors, especially the imbalance of intestinal flora caused by the high altitude environment. The mechanism of intestinal barrier damage and the drugs to protect the intestinal barrier are reviewed. Studying the mechanism of intestinal barrier damage in high altitude environment is not only conducive to understanding the mechanism of high altitude environment affecting intestinal barrier function, but also provides a more scientific medicine treatment method for intestinal damage caused by the special high altitude environment.

Influences of Yogurt with Functional Ingredients from Various Sources That Help Treat Leaky Gut on Intestinal Barrier Dysfunction in Caco-2 Cells

The impact of yogurts made with starter culture bacteria (L. bulgaricus and S. thermophilus) and supplemented with ingredients (maitake mushrooms, quercetin, L-glutamine, slippery elm bark, licorice root, N-acetyl-D-glucosamine, zinc orotate, and marshmallow root) that can help treat leaky gut were investigated using the Caco-2 cell monolayer as a measure of intestinal barrier dysfunction. Milk from the same source was equally dispersed into nine pails, and the eight ingredients were randomly allocated to the eight pails. The control had no ingredients. The Caco-2 cells were treated with isoflavone genistein (negative control) and growth media (positive control). Inflammation was stimulated using an inflammatory cocktail of cytokines (interferon-γ, tumor necrosis factor-α, and interleukin-1β) and lipopolysaccharide. The yogurt without ingredients (control yogurt) was compared to the yogurt treatments (yogurts with ingredients) that help treat leaky gut. Transepithelial electrical resistance (TEER) and paracellular permeability were measured to evaluate the integrity of the Caco-2 monolayer. Transmission electron microscopy (TEM), immunofluorescence microscopy (IM), and real-time quantitative polymerase chain reaction (RTQPCR) were applied to measure the integrity of tight junction proteins. The yogurts were subjected to gastric and intestinal digestion, and TEER was recorded. Ferrous ion chelating activity, ferric reducing potential, and DPPH radical scavenging were also examined to determine the yogurts' antioxidant capacity. Yogurt with quercetin and marshmallow root improved the antioxidant activity and TEER and had the lowest permeability in fluorescein isothiocyanate (FITC)-dextran and Lucifer yellow flux among the yogurt samples. TEM, IM, and RTQPCR revealed that yogurt enhanced tight junction proteins' localization and gene expression. Intestinal digestion of the yogurt negatively impacted inflammation-induced Caco-2 barrier dysfunction, while yogurt with quercetin, marshmallow root, maitake mushroom, and licorice root had the highest TEER values compared to the control yogurt. Yogurt fortification with quercetin, marshmallow root, maitake mushroom, and licorice root may improve functionality when dealing with intestinal barrier dysfunction.

Emerging therapies in cancer metabolism

Metabolic reprogramming in cancer is not only a biological hallmark but also reveals treatment vulnerabilities. Numerous metabolic molecules have shown promise as treatment targets to impede tumor progression in preclinical studies, with some advancing to clinical trials. However, the intricacy and adaptability of metabolic networks hinder the effectiveness of metabolic therapies. This review summarizes the metabolic targets for cancer treatment and provides an overview of the current status of clinical trials targeting cancer metabolism. Additionally, we decipher crucial factors that limit the efficacy of metabolism-based therapies and propose future directions. With advances in integrating multi-omics, single-cell, and spatial technologies, as well as the ability to track metabolic adaptation more precisely and dynamically, clinicians can personalize metabolic therapies for improved cancer treatment.

Physico-chemical, microbiological, and sensory characteristics of yogurt as affected by various ingredients

l-Glutamine, quercetin, slippery elm bark, marshmallow root, N-acetyl-d-glucosamine, licorice root, maitake mushrooms, and zinc orotate have been reported to help treat leaky gut. The purpose of this research was to explore the impact of these functional ingredients on the physico-chemical, microbiological, and sensory properties of yogurt. The milk from same source was equally divided into 9 pails and the 8 ingredients were randomly assigned to the 8 pails. The control had no ingredient. Milk was fermented to yogurt. The pH, titratable acidity, syneresis, viscosity, color (L*, a*, b*, C*, and h*), Streptococcus thermophilus counts, and Lactobacillus delbrueckii spp. bulgaricus counts of yogurts were determined on d 1, 7, 14, 21, 28, 35, and 42, whereas coliform counts, yeast and mold counts, and rheological characteristics were determined on d 1 and 42. The sensory study was performed on d 3 and particle size of the functional ingredients (powder form) was also determined. When compared with control, the incorporation of slippery elm bark into yogurts led to less syneresis. l-Glutamine increased pH and n' values (relaxation exponent derived from G') and lowered titratable acidity values. N-Acetyl-d-glucosamine incorporation resulted in higher n' and lower titratable acidity values, whereas maitake mushroom led to lower n' values. Incorporating quercetin increased the growth of L. bulgaricus. Adding maitake mushrooms increased the growth of S. thermophilus but lowered apparent viscosity values, whereas quercetin decreased its S. thermophilus counts. Quercetin decreased L* and a* values but increased b* values, and maitake mushroom increased a* values. Thixotropic behavior increased with the addition of licorice root and quercetin. Adding slippery elm bark, N-acetyl-d-glucosamine, licorice root, maitake mushrooms, and zinc orotate into yogurt did not affect the sensory properties, whereas yogurts with quercetin had the lowest sensory scores. Overall, most of these ingredients did not cause major changes to yogurt properties.

Attributes of Culture Bacteria as Influenced by Ingredients That Help Treat Leaky Gut

Consumers are becoming aware of functional ingredients such as medicinal herbs, polyphenols, mushrooms, amino acids, proteins, and probiotics more than ever before. Like yogurt and its probiotics, L-glutamine, quercetin, slippery elm bark, marshmallow root, N-acetyl-D-glucosamine, licorice root, maitake mushrooms, and zinc orotate have demonstrated health benefits through gut microbiota. The impact of these ingredients on yogurt starter culture bacteria characteristics is not well known. The objective of this study was to determine the influence of these ingredients on the probiotic characteristics, tolerance to gastric juices and lysozyme, protease activity, and viability of Streptococcus thermophilus STI-06 and Lactobacillus bulgaricus LB-12. Acid tolerance was determined at 0, 30, 60, 90, and 120 min of incubation, whereas bile tolerance was analyzed at 0, 4, and 8 h. The microbial growth was determined at 0, 2, 4, 6, 8, 10, 12, 14, and 16 h of incubation, while protease activity was evaluated at 0, 12, and 24 h. The application of marshmallow root, licorice root, and slippery elm bark improved bile tolerance and acid tolerance of S. thermophilus. These ingredients did not impact the bile tolerance, acid tolerance, and simulated gastric juice tolerance characteristics of L. bulgaricus over 8 h and 120 min (respectively) of incubation. Similarly, the growth of S. thermophilus and L. bulgaricus was not affected by any of these functional ingredients. The application of marshmallow root, N-acetyl-D-glucosamine, and maitake mushroom significantly increased the protease activity of S. thermophilus, whereas the protease activity of L. bulgaricus was not affected by any ingredient. Compared to the control, marshmallow root and quercetin samples had higher mean log counts and log counts for S. thermophilus on the simulated gastric juice and lysozyme resistance in vitro test, respectively. For L. bulgaricus, licorice root, quercetin, marshmallow root, and slippery elm bark samples had higher log counts than the control samples.

Nutritional supplements for the control of avian coccidiosis

Coccidiosis is acclaimed as the most prevalent enteric parasitic ailment of poultry. It is caused by an apicomplexan protozoon of the genus Eimeria, which resides in chicken intestinal epithelium leading to intestinal damage. As a result, bloody droppings are there, feed efficiency is reduced, the growth rate is impaired, and egg production is temporarily decreased. Treatment and prevention of coccidiosis are primarily accomplished by inoculating live vaccines and administering anticoccidial drugs. Due to anticoccidials’ continuous and excessive use, the mounting issue is drug resistant Eimeria strains. The poultry industry has managed resistance-related issues by suggesting shuttle and rotation schemes. Furthermore, new drugs have also been developed and introduced, but it takes a long time and causes cost inflation in the poultry industry. Moreover, government disallows growth promoters and drugs at sub-therapeutic doses in poultry due to increased concerns about the drug residues in poultry products. These constraints have motivated scientists to work on alternative ways to control coccidiosis effectively, safely, and sustainably. Using nutritional supplements is a novel way to solve the constraints mentioned above. The intriguing aspects of using dietary supplements against coccidiosis are that they reduce the risk of drug-resistant pathogen strains, ensure healthy, nutritious poultry products, have less reliance on synthetic drugs, and are typically considered environmentally safe. Furthermore, they improve productivity, enhance nonspecific immunity, preventing oxidation of fats (acting as antioxidants) and inflammation (acting as an anti-inflammatory). The present manuscript focuses on the efficacy, possible mechanism of action, applications, and different facets of nutrition supplements (such as organic acids, minerals, vitamins, probiotics, essential oils, amino acids, dietary nucleotides, feed enzymes, and yeast derivatives) as feed additive for treating poultry coccidiosis.

High-Grain Diet Feeding Altered Blood Metabolites, Rumen Microbiome, and Metabolomics of Yaks

Currently, information available on the comprehensive changes in the rumen bacteria and metabolites of yaks fed high-grain diets is limited. This study aimed to investigate the effects of high-grain diet feeding on the blood metabolites, rumen microbiome, and metabolomics of yaks by using 16S rDNA gene sequencing and liquid chromatography–mass spectrometry (LC/MS). Here, fourteen healthy male yaks (body weight, 249.61 ± 8.13 kg) were randomly assigned to two different diets: a hay diet (0% grain, CON, n = 7), or a high-grain diet (70% grain, HG, n = 7). At the 74th day of treatment, blood and ruminal fluid samples were collected for the blood metabolites, rumen microbiome, and metabolomics analyses. The HG diet increased lipopolysaccharides (LPS), aspartate aminotransferase (AST), gamma-glutamyltransferase (GGT), haptoglobin (HPT), serum amyloid-A (SAA), interleukin-1β (IL1-β), interleukin-6 (IL-6), and tumor necrosis factor-α (TNF-α) serum concentrations (p < 0.05). Compared with the CON diet, the HG diet decreased rumen pH (p < 0.05), and increased total volatile fatty acids concentration, and proportion of butyrate (p < 0.05). The relative abundance of Firmicutes and Saccharibacteria were higher (p < 0.05), while Bacteroidetes was lower (p < 0.05) in the HG group than those in the CON group. At the genus level, the relative abundance of Christensenelaceae_R-7_group, Ruminococcaceae_NK4A214_group, Lachnospiraceae_NK3A20_group, and Acetitomaculum were higher than in those in the HG diet (p < 0.05). Compared with the CON group, the HG diet increased the concentrations of biogenic amines (histamine, tyramine, and putrescine), common amino acids (phenylalanine, threonine, serine, etc.), and arachidonic acid (prostaglandin H2, prostaglandin E2, 12(S)-HPETE, etc.). Collectively, these findings demonstrate that the HG diet altered the microbiota and metabolites, as well as potentially damaged their rumen health and induced inflammation in yaks.

Glutamine supplementation moderately affects growth, plasma metabolite and free amino acid patterns in neonatal low birth weight piglets

Low birth weight (LBW) neonates show impaired growth compared with normal birth weight (NBW) neonates. Glutamine (Gln) supplementation benefits growth of weaning piglets, while the effect on neonates is not sufficiently clear. We examined the effect of neonatal Gln supplementation on piglet growth, milk intake and metabolic parameters. Sow-reared pairs of newborn LBW (0·8-1·2 kg) and NBW (1·4-1·8 kg) male piglets received Gln (1 g/kg body mass (BM)/d; Gln-LBW, Gln-NBW; n 24/group) or isonitrogenous alanine (1·22 g/kg BM/d; Ala-LBW; Ala-NBW; n 24/group) supplementation at 1-5 or 1-12 d of age (daily in three equal portions at 07:00, 12:00 and 17:00 by syringe feeding). We measured piglet BM, milk intake (1, 11-12 d), plasma metabolite, insulin, amino acid (AA) and liver TAG concentrations (5, 12 d). The Gln-LBW group had higher BM (+7·5%, 10 d, P = 0·066; 11-12 d, P < 0·05) and milk intake (+14·7%, P = 0·015) than Ala-LBW. At 5 d, Ala-LBW group had higher plasma TAG (+34·7%, P < 0·1) and lower carnosine (-22·5%, P < 0·05) than Ala-NBW and Gln-LBW, and higher liver TAG (+66·9%, P = 0·029) than Ala-NBW. At 12 d, plasma urea was higher (+37·5%, P < 0·05) with Gln than Ala supplementation. Several proteinogenic AA in plasma were lower (P < 0·05) in Ala-NBW v. Gln-NBW. Plasma arginine was higher (P < 0·05) in Gln-NBW v Ala-NBW piglets (5, 12 d). Supplemental Gln moderately improved growth and milk intake and affected lipid metabolism in LBW piglets and AA metabolism in NBW piglets, suggesting effects on intestinal and liver function.

Effects of Glutamine on Rumen Digestive Enzymes and the Barrier Function of the Ruminal Epithelium in Hu Lambs Fed a High-Concentrate Finishing Diet

The present experiment aimed to research the effects of glutamine (Gln) on the digestive and barrier function of the ruminal epithelium in Hu lambs fed a high-concentrate finishing diet containing some soybean meal and cottonseed meal. Thirty healthy 3-month-old male Hu lambs were randomly divided into three treatments. Lambs were fed a high-concentrate diet and supplemented with 0, 0.5, and 1% Gln on diet for 60 days. The experimental results show that the Gln treatment group had lower pepsin and cellulase enzyme activity, propionate acid concentration, and IL-6, TNF-α, claudin-1, and ZO-1 mRNA expression in the ruminal epithelium (p < 0.05); as well as increases in lipase enzyme activity, the ratio of propionic acid to acetic acid, the IL-10 content in the plasma, and the mRNA expression of IL-2 and IL-10 in the ruminal epithelium, in contrast to the CON (control group) treatment (p < 0.05). Taken together, the findings of this present study support the addition of Gln to improve digestive enzyme activity, the ruminal epithelium’s barrier, and fermentation and immune function by supplying energy to the mononuclear cells, improving the ruminal epithelium’s morphology and integrity, and mediating the mRNA expression of tight junction proteins (TJs) and cytokines.

Coadministration of L-alanine and L-glutamine ameliorate blood glucose levels, biochemical indices and histological features in alloxan-induced diabetic rats

We evaluated the effects of supplementation of L-alanine and L-glutamine on blood glucose levels and biochemical parameters in alloxan-induced diabetic rat. Forty-nine animals were distributed into seven equal groups. Except for the non-diabetic control, diabetes was induced in all groups by intravenous alloxan injection followed by daily supplementation with amino acids for 14 days. Weight and blood glucose were monitored during supplementation, while biochemical parameters such as liver and renal functions, lipid profile, and antioxidant markers were evaluated post-intervention. A significant increase (p < .05) in weight and decrease in blood glucose were observed in the amino acid(s) treated groups. The supplementation with both amino acids restored important tissue antioxidants, liver and kidney functions and rescued islets cells degeneration. Histopathological examinations of important tissues showed the restoration of alloxan-induced physiopathological changes by the amino acids. Thus, these amino acids might serve as nutraceuticals for the management and treatment of diabetes. PRACTICAL APPLICATIONS: The discovery and production of antidiabetic bioactive compounds are often challenging, and the existing antidiabetic drugs are expensive. Amino acids are key regulators of glucose metabolism, insulin secretion, and insulin sensitivity; thus, they can play a crucial role in alleviating diabetes. Here, we present findings that strongly suggest the potential of pure amino acids (L-alanine and L-glutamine) for the management and treatment of diabetes. We show that these amino acids, when supplemented singly or coadministered can lower blood glucose levels and restore several other biochemical parameters implicated in diabetes. Hence, these cheap amino acids may be consumed as nutraceuticals or food supplements by diabetics for the treatment/management of diabetes. Foods rich in these amino acids may also be consumed as part of the diet of diabetic patients.

Fecal Microbiota Transplantation Could Improve Chronic Diarrhea in Cynomolgus Monkey by Alleviating Inflammation and Modulating Gut Microbiota

Chronic diarrhea is associated with enteric dysbiosis and provokes the overuse of antibiotics. Fecal microbiota transplantation (FMT) is a promising therapy, but it shows discrepant clinical efficacy. Bacterial colonization in recipients has been studied, although little is known about the role of gut fungi and Archaea after FMT. In this study, we evaluated the efficacy of human-derived FMT on spontaneous chronic diarrhea cynomolgus monkeys and revealed the effector mechanisms. We demonstrated that FMT can mitigate the appearance of diarrheal symptoms and inhibit the increase in interleukin-6, interleukin-8, interleukin-1β, and interferon-γ and the decrease in interleukin-10 in serum. We confirmed that FMT restored the disturbance of gut bacteria by reducing the relative abundances of potential pathogens, including Cloacibacillus porcorum, Desulfovibrio desulfuricans, Erysipelotrichaceae bacterium 5_2_54FAA, and Erysipelotrichaceae bacterium 21_3, and increasing the levels of Lactobacillus fermentum and Lactobacillus ruminis CAG_367 in diarrheal monkeys. The metabolic pathways of healthy and FMT monkeys' gut bacteria were enriched in amino acid metabolism, carbohydrate metabolism, and lipid metabolism, while the metabolic pathways of pre-FMT monkeys' gut bacteria were enriched in antibiotic production. Moreover, a higher Ascomycota/Basidiomycota ratio, higher Aspergillus levels, and lower Trichosporon asahii abundance were present in intestinal fungi after FMT. Although the abundance of the Archaea Methanosphaera stastmanae did not change significantly, it was inversely correlated with the anti-inflammatory factor IL-4 after FMT. These results support the further development and application of FMT for chronic diarrhea.

Correlation Between Zinc Nutritional Status with Serum Zonulin and Gastrointestinal Symptoms in Diarrhea-Predominant Irritable Bowel Syndrome: A Case-Control Study

BACKGROUND

Zinc is known to have a critical role in the maintenance of intestinal homeostasis, immune cells, and anti-diarrheal and anti-inflammatory actions.

AIMS

The aim of this study was to evaluate the correlation between zinc status with serum zonulin and gastrointestinal symptoms in diarrhea-predominant patients with irritable bowel syndrome (IBS-D).

METHODS

This case-control study included 61 newly diagnosed IBS-D patients and 61 healthy matched controls. Dietary zinc intake, serum zinc, and zonulin levels were measured. IBS severity was evaluated using the IBS severity score system (IBS-SSS) questionnaire.

RESULTS

Serum zinc levels were lower in the IBS-D group compared with the controls (p = 0.001). Serum zinc was negatively correlated with serum zonulin in IBS-D patients (r = - 0.271; p = 0.035). Also, a reverse association between the serum zinc and odds of IBS-D was found [OR = 0.979; 95% CI (0.966-0.992)].

CONCLUSIONS

Our results suggest that zinc may have a role in the pathogenesis of IBS. However, clinical trial studies are warranted to evaluate this finding.

Dysregulation of Astrocytic Glutamine Transport in Acute Hyperammonemic Brain Edema

Acute liver failure (ALF) impairs ammonia clearance from blood, which gives rise to acute hyperammonemia and increased ammonia accumulation in the brain. Since in brain glutamine synthesis is the only route of ammonia detoxification, hyperammonemia is as a rule associated with increased brain glutamine content (glutaminosis) which correlates with and contributes along with ammonia itself to hyperammonemic brain edema-associated with ALF. This review focuses on the effects of hyperammonemia on the two glutamine carriers located in the astrocytic membrane: Slc38a3 (SN1, SNAT3) and Slc7a6 (y + LAT2). We emphasize the contribution of the dysfunction of either of the two carriers to glutaminosis- related aspects of brain edema: retention of osmotically obligated water (Slc38a3) and induction of oxidative/nitrosative stress (Slc7a6). The changes in glutamine transport link glutaminosis- evoked mitochondrial dysfunction to oxidative-nitrosative stress as formulated in the “Trojan Horse” hypothesis.

Standardized ileal digestibility of amino acids in broiler chickens fed single or mixture of feed ingredients-based diets with or without Eimeria challenge

The effect of Eimeria challenge on standardized ileal digestibility (SID) of amino acids (AA) in major poultry feed ingredients fed to broiler chickens was determined. A total of 840 male 9-day-old Ross 708 chicks were placed in 84 cages (10 birds/cage) and allocated to either a nitrogen-free diet (NFD) or one of the 6 test diets based on a single or mixture of feed ingredients as the sole source of AA (n = 12). Test diets were: 1) corn, 2) wheat, 3) soybean meal (SBM), 4) pork meal (PM), 5) corn, SBM, and PM (CSP), and 6) wheat, SBM, and PM (WSP). On d 10, birds in 6 cages/diet were orally gavaged with 1 mL of E. acervulina and E. maxima mixture and the other 6 cages with sham. On d 15, birds were bled for plasma AA and necropsied for intestinal lesion scores and ileal digesta samples. Challenge decreased (P < 0.05) plasma concentration of Arg, His, Thr, Asp, Gln, and Tyr and increased concentration of Lys, Ile, Leu, and Val. There was a diet by challenge interaction (P < 0.05) on intestinal lesion scores with birds fed mixed diets exhibiting more severe lesions than birds fed single ingredient diets. Diet by challenge interacted (P < 0.05) on ileal total endogenous flow (ITEF) of AA except for Arg, Met, Ala, Asp, and Cys, such that challenged birds fed the mixed, particularly WSP, had higher ITEF of AA compared to single ingredients birds. Diet and challenge interaction (P < 0.05) was observed for SID of Arg, Thr, Val, Glu, and Gly. Challenge decreased (P < 0.05) SID of most AA except for Met, Asp, and Cys with the largest impact seen on Lys, His, Ser, and Thr. With exception of Arg, Thr, Asp, and Cys, birds fed mixed diets had higher (P < 0.05) SID values compared to birds fed single ingredients. In conclusion, Eimeria reduced plasma availability and ileal digestibility of most AA. However, challenge interaction with diet composition on SID of some AA warrants further investigations.

Ameliorative Potential of L-Alanyl L-Glutamine Dipeptide in Colon Cancer Patients Receiving Modified FOLFOX-6 Regarding the Incidence of Diarrhea, the Treatment Response, and Patients’ Survival: A Randomized Controlled Trial

Background and Objectives: Diarrhea induced by chemotherapy may represent a life-threatening adverse effect in cancer patients receiving chemotherapy. FOLFOX, an effective treatment for colon cancer, has been associated with diarrhea with high severity, particularly with higher doses. Management of diarrhea is crucial to increase the survival of cancer patients and to improve the quality of life. Glutamine is an abundant protein peptide found in blood and has a crucial role in boosting immunity, increasing protein anabolism, and decreasing the inflammatory effects of chemotherapy on the mucosal membranes, including diarrhea. This study aimed to provide evidence that parenteral L-alanyl L-glutamine dipeptide may have a positive influence on the incidence of diarrhea, treatment response, and the overall survival in colon cancer patients treated with modified FOLFOX-6 (mFOLFOX-6). Materials and Methods: Forty-four stage II and III colon cancer patients were included in this study where they were treated with the standard colon cancer chemotherapy mFOLFOX-6 and were randomly allocated into glutamine group and placebo group, each of 22 patients. Results: L-alanyl L-glutamine dipeptide was found to be significantly effective in decreasing the frequency and severity of diarrhea when compared to the placebo group, particularly after four and six cycles of mFOLFOX-6. There was no significant difference between the studied groups regarding to the overall survival. Conclusion: L-alanyl L-glutamine dipeptide can be considered as an add-on with chemotherapy to improve the quality of life and the overall survival of colon cancer patients.

Socioeconomic disparities and household crowding in association with the fecal microbiome of school-age children

The development of the gut microbiome occurs mainly during the first years of life; however, little is known on the role of environmental and socioeconomic exposures, particularly within the household, in shaping the microbial ecology through childhood. We characterized differences in the gut microbiome of school-age healthy children, in association with socioeconomic disparities and household crowding. Stool samples were analyzed from 176 Israeli Arab children aged six to nine years from three villages of different socioeconomic status (SES). Sociodemographic data were collected through interviews with the mothers. We used 16 S rRNA gene sequencing to characterize the gut microbiome, including an inferred analysis of metabolic pathways. Differential analysis was performed using the analysis of the composition of microbiomes (ANCOM), with adjustment for covariates. An analysis of inferred metagenome functions was performed implementing PICRUSt2. Gut microbiome composition differed across the villages, with the largest difference attributed to socioeconomic disparities, with household crowding index being a significant explanatory variable. Living in a low SES village and high household crowding were associated with increased bacterial richness and compositional differences, including an over-representation of Prevotella copri and depleted Bifidobacterium. Secondary bile acid synthesis, d-glutamine and d-glutamate metabolism and Biotin metabolism were decreased in the lower SES village. In summary, residential SES is a strong determinant of the gut microbiome in healthy school-age children, mediated by household crowding and characterized by increased bacterial richness and substantial taxonomic and metabolic differences. Further research is necessary to explore possible implications of SES-related microbiome differences on children's health and development.

High altitude exposures and intestinal barrier dysfunction

Gastrointestinal complaints are often reported during ascents to high altitude (> 2500 m), though their etiology is not known. One potential explanation is injury to the intestinal barrier which has been implicated in the pathophysiology of several diseases. High altitude exposures can reduce splanchnic perfusion and blood oxygen levels causing hypoxic and oxidative stress. These stressors might injure the intestinal barrier leading to consequences such as bacterial translocation and local/systemic inflammatory responses. The purpose of this mini review is to 1) discuss the impact of high-altitude exposures on intestinal barrier dysfunction, and 2) present medications and dietary supplements which may have relevant impacts on the intestinal barrier during high-altitude exposures. There is a small but growing body of evidence which shows that acute exposures to high altitudes can damage the intestinal barrier. Initial data also suggests that prolonged hypoxic exposures can compromise the intestinal barrier through alterations in immunological function, microbiota, or mucosal layers. Exertion may worsen high-altitude related intestinal injury via additional reductions in splanchnic circulation and greater hypoxemia. Collectively these responses can result in increased intestinal permeability and bacterial translocation causing local and systemic inflammation. More research is needed to determine the impact of various medications and dietary supplements on the intestinal barrier during high-altitude exposures.

Clinical development of metabolic inhibitors for oncology

Metabolic inhibitors have been used in oncology for decades, dating back to antimetabolites developed in the 1940s. In the past 25 years, there has been increased recognition of metabolic derangements in tumor cells leading to a resurgence of interest in targeting metabolism. More recently there has been recognition that drugs targeting tumor metabolism also affect the often acidic, hypoxic, immunosuppressive tumor microenvironment (TME) and non-tumor cell populations within it, including immune cells. Here we review small-molecule metabolic inhibitors currently in clinical development for oncology applications. For each agent, we evaluate the preclinical studies demonstrating antitumor and TME effects and review ongoing clinical trials. The goal of this Review is to provide an overview of the landscape of metabolic inhibitors in clinical development for oncology.

Gut Microbiome Activity Contributes to Prediction of Individual Variation in Glycemic Response in Adults

Limiting postprandial glycemic response (PPGR) is an important intervention in reducing the risk of chronic metabolic diseases and has been shown to impart significant health benefits in people with elevated levels of blood sugar. In this study, we collected gut microbiome activity data by assessing the metatranscriptome, and we measured the glycemic responses of 550 adults who consumed more than 30,000 meals, collectively, from omnivore or vegetarian/gluten-free diets. We demonstrate that gut microbiome activity, anthropometric factors, and food macronutrients modulate individual variation in glycemic response. We employ two predictive models, including a mixed-effects linear regression model (R = 0.77) and a gradient boosting machine model (Rtrain = 0.80/R2train = 0.64; Rtest = 0.64/R2test = 0.40), which demonstrate variation in PPGR between individuals when ingesting the same foods. All features in the final mixed-effects linear regression model were significant (p < 0.05) except for two features which were retained as suggestive: glutamine production pathways (p = 0.08) and the interaction between tyrosine metabolizers and carbs (p = 0.06). We introduce molecular functions as features in these two models, aggregated from microbial activity data, and show their statistically significant contributions to glycemic control. In summary, we demonstrate for the first time that metatranscriptomic activity of the gut microbiome is correlated with PPGR among adults.

Safety, Tolerability, and Biologic Activity of AXA1125 and AXA1957 in Subjects With Nonalcoholic Fatty Liver Disease

INTRODUCTION

AXA1125 and AXA1957 are novel, orally administered endogenous metabolic modulator compositions, specifically designed to simultaneously support multiple metabolic and fibroinflammatory pathways associated with nonalcoholic fatty liver disease (NAFLD). This study assessed safety, tolerability, and biologic activity of AXA1125 and AXA1957 in NAFLD.

METHODS

In this multicenter, 16-week, placebo-controlled, single-blind, randomized clinical study in subjects with NAFLD stratified by type 2 diabetes, AXA1125 24 g, AXA1957 13.5 g or 20.3 g, or placebo was administered twice daily. Key metabolism (MRI-proton density fat fraction [MRI-PDFF] and homeostasis model assessment of insulin resistance [HOMA-IR]) and fibroinflammation markers (alanine aminotransferase [ALT], corrected T1 [cT1], keratin-18 [K-18] M65, and N-terminal type III collagen propeptide [Pro-C3]) were evaluated. Safety outcomes included adverse events and standard laboratory assessments.

RESULTS

Baseline characteristics of the 102 enrolled subjects, including 40 with type 2 diabetes, were consistent with presumed nonalcoholic steatohepatitis. AXA1125 showed consistently greater biologic activity than AXA1957 or placebo. Week 16 changes from baseline with AXA1125 vs placebo: MRI-PDFF -22.9% vs -5.7%, HOMA-IR -4.4 vs +0.7, ALT -21.9% vs -7.2%, K-18 M65 -13.6% vs +20.1%, cT1 -69.6 vs +18.3 ms (P < 0.05), and Pro-C3 -13.6% vs -3.6%. Week 16 changes from baseline with AXA1957 20.3 g: MRI-PDFF -8.1%, HOMA-IR +8.4, ALT -20.7%, K-18 M65 6.6%, cT1 -34.7 ms, and Pro-C3 -15.6%. A greater proportion of subjects treated with AXA1125 achieved clinically relevant thresholds: ≥30% MRI-PDFF, ≥17-IU/L ALT, and ≥80-ms cT1 reductions at week 16. Study products were safe and well tolerated with stable lipid and weight profiles.

DISCUSSION

Both compositions showed multitargeted activity on relevant NAFLD pathways. AXA1125 demonstrated the greatest activity over 16 weeks, warranting continued clinical investigation in nonalcoholic steatohepatitis subjects.

Effects of low-crude protein diets supplemented with arginine, glutamine, threonine, and methionine on regulating nutrient absorption, intestinal health, and growth performance of Eimeria-infected chickens

The study was conducted to evaluate the effects of low crude protein diets supplemented with arginine, glutamine, methionine, and/or threonine on apparent ileal digestibility of amino acids, intestinal morphology, intestinal permeability, gene expression of nutrient transporters, and tight junction proteins of broiler chickens challenged with mixed Eimeria spp. A total of five hundred seventy-six, 12-day-old male broiler chickens were allocated into 8 treatments, and 6 replicate cages of 12 chickens per cage. This experiment included a nonchallenged control (NC) fed regular corn-soybean meal-based diet (Regular diet, 19% crude protein), an Eimeria-challenged control (CC) fed Regular diet, an Eimeria challenge group fed low-crude protein diet (LCP, 16% crude protein), 4 Eimeria challenge groups fed low-crude protein diet supplemented with 0.75% arginine, glutamine, methionine, and threonine, respectively (ARG, GLN, MET, and THR), and an Eimeria challenge group fed low-crude protein diet with 0.75% supplemented arginine, glutamine, methionine, and threonine collectively as a combination group (COMB). On d 14, birds in the challenge groups were gavaged with a mixed Eimeria spp. solution containing 12,500 oocysts of E. maxima, 12,500 oocysts of E. tenella, and 62,500 oocysts of E. acervulina. The results showed that the Eimeria challenge reduced overall growth performance, but the LCP had no adverse impacts on intestinal health and growth of Eimeria-infected birds compared to the CC. Additionally, supplementation of crystalline arginine, glutamine, methionine, and threonine improved the apparent ileal digestibility of these specific amino acids on 6 dpi. Moreover, the THR treatment increased villus height in the duodenum. The ARG treatment decreased intestinal permeability and gene expression of amino acid transporters, whereas the GLN and THR treatments both reversed adverse effects of coccidiosis on gene expression of tight junction protein (claudin 1). However, the MET and COMB treatments exacerbated infection severity of coccidiosis. In summary, adding 0.75% of arginine, glutamine, or threonine in a low crude protein diet can improve the intestinal health of birds challenged with a mild coccidia infection.

Mucosal Microbiota and Metabolome in the Ileum of Hu Sheep Offered a Low-Grain, Pelleted or Non-pelleted High-Grain Diet

Alterations in mucosal microbiota and metabolites are critical to intestinal homeostasis and host health. This study used a combination of 16S rRNA gene sequencing and liquid chromatography-mass spectrometry (LC/MS) to investigate mucosal microbiota and their metabolic profiles in the ileum of Hu sheep fed different diets. Here, we randomly allocated 15 Hu sheep to three diets, a non-pelleted low-grain diet (control diet; CON), a non-pelleted high-grain diet (HG), and a pelleted high-grain diet (HP). After 60 days of treatment, ileal mucosal samples were collected for microbiome and metabolome analysis. The results of principal coordinate analysis and permutation multivariate analysis showed that there was a tendency for microbial differentiation between the CON and HG groups (P < 0.1), although no significant difference between the HG and HP groups was observed (P > 0.05). Compared with the CON diet, the HG diet decreased (P < 0.05) the abundance of some probiotic species (e.g., Sphingomonas and Candidatus Arthromitus) and increased (P < 0.05) the abundance of acid-producing microbiota (e.g., Succiniclasticum, Nesterenkonia, and Alloprevotella) in the ileal mucosa. Compared with the HG diet, the HP diet decreased (P < 0.05) the abundance of Alloprevotella and increased (P < 0.05) the abundance of Mycoplasma in the ileal mucosa. Furthermore, partial least squares discriminant analysis and orthogonal partial least-squared discriminant analysis indicated that different dietary treatments resulted in different metabolic patterns in the ileal mucosa of the CON, HG, and HP groups. The HG diet altered (VIP > 1 and P < 0.05) the metabolic patterns of amino acids, fatty acids, and nucleotides/nucleosides (such as increased amounts of ornithine, tyrosine, cis-9-palmitoleic acid, and adenosine) compared with the CON diet. However, 10 differential metabolites (VIP > 1 and P < 0.05; including tyrosine, ornithine, and cis-9-palmitoleic acid) identified in the HG group exhibited a diametrically opposite trend in the HP group, suggesting that the HP diet could partially eliminate the changes brought upon by the HG diet. Collectively, our findings demonstrate that different diets altered the ileal mucosal microbiota and metabolites and provide new insight into the effects of high-grain diets on the intestinal health of ruminant animals.

The use of biomarkers associated with leaky gut as a diagnostic tool for early intervention in autism spectrum disorder: a systematic review

Background

Innovative research highlighted the probable connection between autism spectrum disorder (ASD) and gut microbiota as many autistic individuals have gastrointestinal problems as co-morbidities. This review emphasizes the role of altered gut microbiota observed frequently in autistic patients, and the mechanisms through which such alterations may trigger leaky gut.

Main body

Different bacterial metabolite levels in the blood and urine of autistic children, such as short-chain fatty acids, lipopolysaccharides, beta-cresol, and bacterial toxins, were reviewed. Moreover, the importance of selected proteins, among which are calprotectin, zonulin, and lysozyme, were discussed as biomarkers for the early detection of leaky gut as an etiological mechanism of ASD through the less integrative gut–blood–brain barriers. Disrupted gut–blood–brain barriers can explain the leakage of bacterial metabolites in these patients.

Conclusion

Although the cause-to-effect relationship between ASD and altered gut microbiota is not yet well understood, this review shows that with the consumption of specific diets, definite probiotics may represent a noninvasive tool to reestablish healthy gut microbiota and stimulate gut health. The diagnostic and therapeutic value of intestinal proteins and bacterial-derived compounds as new possible biomarkers, as well as potential therapeutic targets, are discussed.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13099-021-00448-y.

A novel, multitargeted endogenous metabolic modulator composition impacts metabolism, inflammation, and fibrosis in nonalcoholic steatohepatitis-relevant primary human cell models

Nonalcoholic steatohepatitis (NASH) is a complex metabolic disease of heterogeneous and multifactorial pathogenesis that may benefit from coordinated multitargeted interventions. Endogenous metabolic modulators (EMMs) encompass a broad set of molecular families, including amino acids and related metabolites and precursors. EMMs often serve as master regulators and signaling agents for metabolic pathways throughout the body and hold the potential to impact a complex metabolic disease like NASH by targeting a multitude of pathologically relevant biologies. Here, we describe a study of a novel EMM composition comprising five amino acids and an amino acid derivative (Leucine, Isoleucine, Valine, Arginine, Glutamine, and N-acetylcysteine [LIVRQNac]) and its systematic evaluation across multiple NASH-relevant primary human cell model systems, including hepatocytes, macrophages, and stellate cells. In these model systems, LIVRQNac consistently and simultaneously impacted biology associated with all three core pathophysiological features of NASH—metabolic, inflammatory, and fibrotic. Importantly, it was observed that while the individual constituent amino acids in LIVRQNac can impact specific NASH-related phenotypes in select cell systems, the complete combination was necessary to impact the range of disease-associated drivers examined. These findings highlight the potential of specific and potent multitargeted amino acid combinations for the treatment of NASH.

Mechanisms of Food-Induced Symptom Induction and Dietary Management in Functional Dyspepsia

Functional dyspepsia (FD) is a common disorder of gut-brain interaction, characterised by upper gastrointestinal symptom profiles that differentiate FD from the irritable bowel syndrome (IBS), although the two conditions often co-exist. Despite food and eating being implicated in FD symptom induction, evidence-based guidance for dietetic management of FD is limited. The aim of this narrative review is to collate the possible mechanisms for eating-induced and food-related symptoms of FD for stratification of dietetic management. Specific carbohydrates, proteins and fats, or foods high in these macronutrients have all been reported as influencing FD symptom induction, with removal of 'trigger' foods or nutrients shown to alleviate symptoms. Food additives and natural food chemicals have also been implicated, but there is a lack of convincing evidence. Emerging evidence suggests the gastrointestinal microbiota is the primary interface between food and symptom induction in FD, and is therefore a research direction that warrants substantial attention. Objective markers of FD, along with more sensitive and specific dietary assessment tools will contribute to progressing towards evidence-based dietetic management of FD.

Tight Junctions as a Key for Pathogens Invasion in Intestinal Epithelial Cells

Tight junctions play a major role in maintaining the integrity and impermeability of the intestinal barrier. As such, they act as an ideal target for pathogens to promote their translocation through the intestinal mucosa and invade their host. Different strategies are used by pathogens, aimed at directly destabilizing the junctional network or modulating the different signaling pathways involved in the modulation of these junctions. After a brief presentation of the organization and modulation of tight junctions, we provide the state of the art of the molecular mechanisms leading to permeability breakdown of the gut barrier as a consequence of tight junctions’ attack by pathogens, including bacteria, viruses, fungi, and parasites.

Interorgan Metabolism of Amino Acids in Human Health and Disease

Amino acids are integral for human health, influencing an array of physiological processes from gene expression to vasodilation to the immune response. In accordance with this expansive range of unique functions, the tissues of the body engage in a complex interplay of amino acid exchange and metabolism to respond to the organism's dynamic needs for a range of nitrogenous products. Interorgan amino acid metabolism is required for numerous metabolic pathways, including the synthesis of functional amino acids like arginine, glutamate, glutamine, and glycine. This physiological process requires the cooperative handling of amino acids by organs (e.g., the small intestine, skeletal muscle, kidneys, and liver), as well as the complete catabolism of nutritionally essential amino acids such as the BCAAs, with their α-ketoacids shuttled from muscle to liver. These exchanges are made possible by several mechanisms, including organ location, as well as the functional zonation of enzymes and the cell-specific expression of amino acid transporters. The cooperative handling of amino acids between the various organs does not appear to be under the control of any centralized regulation, but is instead influenced by factors such as fluctuations in nutrient availability, hormones, changes associated with development, and altered environmental factors. While the normal function of these pathways is associated with health and homeostasis, affected by physical activity, diet and body composition, dysregulation is observed in numerous disease states, including cardiovascular disease and cancer cachexia, presenting potential avenues for the manipulation of amino acid consumption as part of the therapeutic approach to these conditions in individuals.

Intestinal Barrier Function in Health and Disease-Any role of SARS-CoV-2?

Alterations in the structure and function of the intestinal barrier play a role in the pathogenesis of a multitude of diseases. During the recent and ongoing coronavirus disease (COVID-19) pandemic, it has become clear that the gastrointestinal system and the gut barrier may be affected by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) virus, and disruption of barrier functions or intestinal microbial dysbiosis may have an impact on the progression and severity of this new disease. In this review, we aim to provide an overview of current evidence on the involvement of gut alterations in human disease including COVID-19, with a prospective outlook on supportive therapeutic strategies that may be investigated to rescue intestinal barrier functions and possibly facilitate clinical improvement in these patients.

Free Amino Acids in Human Milk: A Potential Role for Glutamine and Glutamate in the Protection Against Neonatal Allergies and Infections

Breastfeeding is indicated to support neonatal immune development and to protect against neonatal infections and allergies. Human milk composition is widely studied in relation to these unique abilities, which has led to the identification of various immunomodulating components in human milk, including various bioactive proteins. In addition to proteins, human milk contains free amino acids (FAAs), which have not been well-studied. Of those, the FAAs glutamate and glutamine are by far the most abundant. Levels of these FAAs in human milk sharply increase during the first months of lactation, in contrast to most other FAAs. These unique dynamics are globally consistent, suggesting that their levels in human milk are tightly regulated throughout lactation and, consequently, that they might have specific roles in the developing neonate. Interestingly, free glutamine and glutamate are reported to exhibit immunomodulating capacities, indicating that these FAAs could contribute to neonatal immune development and to the unique protective effects of breastfeeding. This review describes the current understanding of the FAA composition in human milk. Moreover, it provides an overview of the effects of free glutamine and glutamate on immune parameters relevant for allergic sensitization and infections in early life. The data reviewed provide rationale to study the role of free glutamine and glutamate in human milk in the protection against neonatal allergies and infections.

The Molecular and Mechanistic Insights Based on Gut-Liver Axis: Nutritional Target for Non-Alcoholic Fatty Liver Disease (NAFLD) Improvement

Non-alcoholic fatty liver disease (NAFLD) is recognized as the most frequent classification of liver disease around the globe. Along with the sequencing technologies, gut microbiota has been regarded as a vital factor for the maintenance of human and animal health and the mediation of multiple diseases. The modulation of gut microbiota as a mechanism affecting the pathogenesis of NAFLD is becoming a growing area of concern. Recent advances in the communication between gut and hepatic tissue pave novel ways to better explain the molecular mechanisms regarding the pathological physiology of NAFLD. In this review, we recapitulate the current knowledge of the mechanisms correlated with the development and progression of NAFLD regulated by the gut microbiome and gut-liver axis, which may provide crucial therapeutic strategies for NAFLD. These mechanisms predominantly involve: (1) the alteration in gut microbiome profile; (2) the effects of components and metabolites from gut bacteria (e.g., lipopolysaccharides (LPS), trimethylamine-N-oxide (TMAO), and N,N,N-trimethyl-5-aminovaleric acid (TMAVA)); and (3) the impairment of intestinal barrier function and bile acid homeostasis. In particular, the prevention and therapy of NAFLD assisted by nutritional strategies are highlighted, including probiotics, functional oligosaccharides, dietary fibers, ω-3 polyunsaturated fatty acids, functional amino acids (L-tryptophan and L-glutamine), carotenoids, and polyphenols, based on the targets excavated from the gut-liver axis.

Herbal formula improves upper and lower gastrointestinal symptoms and gut health in Australian adults with digestive disorders

Gastrointestinal (GI) problems affect half of Western populations. Symptoms can vary from frequent reflux to irritable bowel syndrome. The Nutrition Care (NC) Gut Relief Formula contains a combination of herbs and nutrients including curcumin, Aloe vera, slippery elm, guar gum, pectin, peppermint oil, and glutamine shown to benefit the GI system. The 16-week pre-post study tested the hypothesis that the NC Gut Relief Formula would be tolerable and effective in improving GI symptoms and gut health in adults with digestive disorders. A total of 43 participants completed the study. After a control phase, participants took 5 g/d and then 10 g/d of the formula for 4 weeks. GI symptoms and GI health were assessed by a series of validated questionnaires, for example, Leeds Dyspepsia Questionnaire, Bristol Stool Chart, Birmingham IBS Symptom Questionnaire, and by intestinal permeability and gut microbiota profile. The NC Gut Relief Formula significantly improved the frequency and severity of upper and lower GI symptoms by 60%-80%, including indigestion, heartburn, nausea, constipation or diarrhea, abdominal pain, and troublesome flatulence, and significantly improved physical functioning, energy levels, mood, and sleep by 60%-80%. All participants with normal stool, 90% with hard stool, and 66% with soft stool recovered from intestinal permeability, evident by normal lactulose to mannitol ratios. The NC Gut Relief Formula generally improved microbial profile, with a marked increase in Lactobacillus, Clostridium, and Faecalibacterium prausnitzii. Almost half of the participants with upper GI symptoms taking proton pump inhibitors for heartburn no longer required proton pump inhibitors at the end of the study. A third of participants were able to reintroduce food triggers, such as fermentable oligosaccharides, disaccharides, monosaccharides, and polyols garlic, onion, and beans, or reflux-causing acidic/spicy foods, for example, citrus, tomato, and caffeine, in their diet after 3 months without symptom aggravation. The NC Gut Relief Formula significantly improved GI symptoms and associated quality of life over 3 months while reducing intestinal permeability, improving the microbial profile, reducing the need for reflux medication, and enabling the consumption of previous food triggers.

The Role of Glutamine in the Complex Interaction between Gut Microbiota and Health: A Narrative Review

The scientific literature has demonstrated that glutamine is one of the main beneficial amino acids. It plays an important role in gut microbiota and immunity. This paper provides a critical overview of experimental studies (in vitro, in vivo, and clinical) investigating the efficacy of glutamine and its effect on gut microbiota. As a result of this review, we have summarized that glutamine could affect gut microbiota via different mechanisms including the reduction in the ratio of Firmicutes to Bacteroidetes, with the activation of NF-κB and PI3K-Akt pathways, reducing the intestinal colonization (Eimeria lesions) and bacterial overgrowth or bacterial translocation, increasing the production of secretory immunoglobulin A (SIgA) and immunoglobulin A+ (IgA+) cells in the intestinal lumen, and decreasing asparagine levels. The potential applications of glutamine on gut microbiota include, but are not limited to, the management of obesity, bacterial translocation and community, cytokines profiles, and the management of side effects during post-chemotherapy and constipation periods. Further studies and reviews are needed regarding the effects of glutamine supplementation on other conditions in humans.

Acute glutamine supplementation does not improve 20-km self-paced cycling performance in the heat

INTRODUCTION

The premise of this study was to investigate the effect of acute glutamine supplementation on 20 km time trial cycling performance in the heat, neuromuscular function, inflammation and endotoxemia.

METHODS

Twelve cyclists completed two, 20-km time trials (20TT) in 35 °C (50% relative humidity). Participants ingested either glutamine (GLUT; 0.9 g kg^-1 fat-free mass) or a placebo (CON) 60 min before each 20TT. Physiological and perceptual measures were recorded during each 20TT, and neuromuscular function assessed pre- and post-exercise. Venous blood was analysed for endotoxins, markers of gut damage (inflammatory fatty acid binding protein; I-FABP) and inflammatory cytokines (interleukin-6, IL-6; tumour necrosis factor-alpha, TNF-α). Data were analysed using linear mixed models in a Bayesian framework.

RESULTS

20TT in the heat increased I-FABP and elevated inflammatory cytokines (IL-6 and TNF-α) compared to pre-exercise values but did not result in endotoxemia. Completion time was not statistically different between conditions (mean difference [95% credible interval] = 11 s [- 23, 44]). Relative to CON, GLUT did not alter any physiological or perceptual measures during the 20TT.

CONCLUSION

Glutamine supplementation does not improve 20TT performance in the heat or preserve neuromuscular function when compared to a placebo. These findings suggest that glutamine is not an ergogenic aid or prophylactic intervention for heat-induced gut damage during short-duration self-paced exercise in hot environments.

Free Amino Acid Content in Human Milk is Associated with Infant Gender and Weight Gain during the First Four Months of Lactation

Background: There is a growing interest regarding the physiological role of free amino acids (FAA) present in human milk (HM). Recent studies show FAA in HM could be influenced by infants’ gender and could have an important role in their growth and development. We studied the concentrations of FAA in HM and potential associations with infants’ gender and their patterns of growth in a cohort of Ecuadorian women. Methods: Human milk samples were collected after approximately eight hours of overnight fast within one week (colostrum), 2 weeks (transition milk), and 2 and/or 4 months (mature milk) after parturition. Free AA were determined by cation-exchange chromatography separation. Results: We observed significantly higher concentrations of Glu 14.40 (1.35, 27.44), Gly 1.82 (0.24, 3.4), Cys 0.36 (0.03, 0.68), and Tyr 0.24 (0.02, 0.46) in HM intended for boys. Free Glu, Gly, Cys, and Tyr concentrations increased with time of lactation. In addition, there were higher concentrations of Glu 28.62 (1.78, 55.46) and Ala 7.16 (1.26, 13.06) in HM for children that presented faster weight gain than for those with slower gain. Conclusions: The present results showed that there are differences in FAA levels in HM intended for male and fast-growing children.

γ-Glutamyltransferase enzyme activity of cancer cells modulates L-γ-glutamyl-p-nitroanilide (GPNA) cytotoxicity

L-γ-Glutamyl-p-nitroanilide (GPNA) is widely used to inhibit the glutamine (Gln) transporter ASCT2, but recent studies have demonstrated that it is also able to inhibit other sodium-dependent and independent amino acid transporters. Moreover, GPNA is a well known substrate of the enzyme γ-glutamyltransferase (GGT). Our aim was to evaluate the effect of GGT-mediated GPNA catabolism on cell viability and Gln transport. The GGT-catalyzed hydrolysis of GPNA produced cytotoxic effects in lung cancer A549 cells, resulting from the release of metabolite p-nitroaniline (PNA) rather than from the inhibition of Gln uptake. Interestingly, compounds like valproic acid, verapamil and reversan were able to increase the cytotoxicity of GPNA and PNA, suggesting a key role of intracellular detoxification mechanisms. Our data indicate that the mechanism of action of GPNA is more complex than believed, and further confirm the poor specificity of GPNA as an inhibitor of Gln transport. Different factors may modulate the final effects of GPNA, ranging from GGT and ASCT2 expression to intracellular defenses against xenobiotics. Thus, other strategies - such as a genetic suppression of ASCT2 or the identification of new specific inhibitors - should be preferred when inhibition of ASCT2 function is required.

Association of intestinal permeability with a NUTRIC score in critically ill patients

OBJECTIVES

The aim of this study was to investigate the association of intestinal permeability with the Nutrition Risk in Critically Ill (NUTRIC) score and the modified NUTRIC score (mNUTRIC) in intensive care unit (ICU) hospitalized patients.

METHODS

One hundred and fifty ICU hospitalized adult patients admitted between October 2017 and April 2018 who stayed for >24 h in the general ICU were enrolled in the study. Nutrition status was estimated using the NUTRIC score, an ICU-specific nutrition risk assessment tool. The NUTRIC score was calculated using the exact same thresholds and point system as developed previously. Admission plasma endotoxin and zonulin concentrations were measured to assess intestinal permeability.

RESULTS

Median plasma endotoxin and zonulin increased with increasing mNUTRIC and NUTRIC categories in the overall study population and in the glutamine-deficient subgroup. Multivariate binary logistic regression analyses showed a significant association between the plasma endotoxin (odds ratio [OR], 2.04; 95% confidence interval [CI], 1.8-3.52) and zonulin (OR, 1.11; 95% CI, 1.03-1.20) levels with NUTRIC category in the overall population and the glutamine-deficient subgroup. Similar results were obtained when using mNUTRIC.

CONCLUSIONS

Results from the present study provided evidence that higher plasma endotoxin and zonulin levels are associated with a progressively higher NUTRIC score in critically ill patients.

Protective effects of a novel probiotic strain, Lactococcus lactis ML2018, in colitis: in vivo and in vitro evidence

Multiple articles have confirmed that an imbalance of the intestinal microbiota is closely related to aberrant immune responses of the intestines and to the pathogenesis of inflammatory bowel diseases (IBDs).

Short Communication: Differences in Levels of Free Amino Acids and Total Protein in Human Foremilk and Hindmilk

Free amino acids (FAAs) in human milk are indicated to have specific functional roles in infant development. Studies have shown differences between human milk that is expressed at the beginning of a feed (i.e., foremilk) and the remainder of the milk expressed (i.e., hindmilk). For example, it is well established that human hindmilk is richer in fat and energy than foremilk. Hence, exclusively feeding hindmilk is used to enhance weight gain of preterm, low birthweight infants. Whether FAAs occur differently between foremilk and hindmilk has never been reported, but given their bioactive capacities, this is relevant to consider especially in situations where hindmilk is fed exclusively. Therefore, this study analyzed and compared the FAA and total protein content in human foremilk and hindmilk samples donated by 30 healthy lactating women. The total protein content was found to be significantly higher in hindmilk (p < 0.001), whereas foremilk contained a significantly higher total content of FAAs (p = 0.015). With regards to individual FAAs, foremilk contained significantly higher levels of phenylalanine (p = 0.009), threonine (p = 0.003), valine (p = 0.018), alanine (p = 0.004), glutamine (p < 0.001), and serine (p = 0.012) than hindmilk. Although statistical significance was reached, effect size analysis of the milk fraction on FAA levels in milk revealed that the observed differences were only small. To what extent these differences are of physiological importance for infant development remains to be examined in future research.

Effects of glutamine on intestinal mucus barrier after burn injury

Severe burns may cause intense stress and persistent inflammation, resulting in intestinal mucosal barrier damage. In this study, we evaluated the effects of glutamine (Gln) on intestinal mucus barrier after burn injury. The results showed that glutamine could improve intestinal mucosal blood flow (IMBF), decrease diamine oxidase (DAO) activity, and reduce intestine damage, thereby alleviate intestinal mucous permeability. Severe burn was associated with subsequent decrease in mucus thickness, levels of hexose, sialic acid, and protein. Glutamine administration might partially reverse these changes. Additional experiments showed that supplementation with glutamine could markedly raise the content of glutamine, glutathione (GSH), and ATP in intestinal tissue. Moreover, the levels of mRNA and protein expression of MUC2, intestinal trefoil factor (ITF) were increased remarkably, but contrary to the trend of GRP-78, CHOP. These results suggest that glutamine can improve tissue perfusion and increase energy synthesis in enterocytes, decrease endoplasmic reticulum stress (ERS) and improve mucin and ITF synthesis. Finally, lessen intestinal mucus barrier damage after burn injury.

EGF receptor plays a role in the mechanism of glutamine-mediated prevention of alcohol-induced gut barrier dysfunction and liver injury

Recent study indicated that glutamine prevents alcoholic tissue injury in mouse gut and liver. Here we investigated the potential role of Epidermal Growth Factor Receptor (EGFR) in glutamine-mediated prevention of ethanol-induced colonic barrier dysfunction, endotoxemia and liver damage. Wild-type and EGFR*Tg transgenic (expressing dominant negative EGFR) mice were fed 1-6% ethanol in Lieber-DeCarli diet. Gut permeability was measured by vascular-to-luminal flux of FITC-inulin, and junctional integrity assessed by confocal microscopy. Liver injury was evaluated by plasma transaminases, histopathology and triglyceride analyses. Glutamine effect on acetaldehyde-induced tight junction disruption was investigated in Caco-2 cell monolayers. Doxycycline-induced expression of EGFR* blocked glutamine-mediated prevention of ethanol-induced disruption of colonic epithelial tight junction, mucosal permeability and endotoxemia. Ethanol activated cofilin and disrupted actin cytoskeleton, which was blocked by glutamine in an EGFR-dependent mechanism. Ethanol down-regulated antioxidant gene expression and up-regulated cytokine and chemokine gene expression, which were blocked by glutamine in wild-type mice in the presence or absence of doxycycline, but not in EGFR*Tg mice in the presence of doxycycline. Histopathology, plasma transaminases, triglyceride and expression of chemokine and antioxidant genes indicated ethanol-induced liver damage, which were blocked by glutamine in an EGFR-dependent mechanism. Src kinase activity and extracellular ligand binding domain of EGFR are required for glutamine-mediated protection of barrier function in Caco-2 cell monolayers. Glutamine released metalloproteinases into the medium, and metalloproteinase inhibitors blocked glutamine-mediated protection of barrier function. Results demonstrate that EGFR plays an important role in glutamine-mediated prevention of alcoholic gut permeability, endotoxemia and liver damage.