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1.
A Prospective Study on Child Morbidity and Gut Microbiota in Rural Malawi.
Kortekangas, E, Young, R, Cheung, YB, Fan, YM, Jorgensen, JM, Kamng'ona, AW, Chaima, D, Ashorn, U, Dewey, KG, Maleta, K, et al
Journal of pediatric gastroenterology and nutrition. 2019;(4):431-437
Abstract
OBJECTIVES The determinants of gut microbiota composition and its effects on common childhood illnesses are only partly understood, especially in low-income settings. The aim of the present study was to investigate whether morbidity predicts gut microbiota composition in Malawian children and whether microbiota predicts subsequent morbidity. We tested the hypothesis that common infectious disease symptoms would be predictive of lower microbiota maturity and diversity. METHODS We used data from 631 participants in a randomized-controlled nutrition intervention trial, in which a small-quantity lipid-based nutrient supplement was provided to pregnant and lactating mothers and their children at 6 to 18 months of age. Fecal samples were collected from the children at 6, 12, 18, and 30 months of age and analyzed using 16S rRNA sequencing. Microbiota variables consisted of measures of microbiota diversity (Shannon Index), microbiota maturity (microbiota-for-age z score), and the relative abundances of taxa. Morbidity variables included gastrointestinal and respiratory symptoms and fever. RESULTS Diarrhea and respiratory symptoms from 11 to 12 months were predictive of lower microbiota-for-age z score and higher Shannon Index, respectively (P = 0.035 and P = 0.023). Morbidity preceding sample collection was predictive of the relative abundances of several bacterial taxa at all time points. Higher microbiota maturity and diversity at 6 months were predictive of a lower incidence rate of fever in the subsequent 6 months (P = 0.007 and P = 0.031). CONCLUSIONS Our findings generally do not support the hypothesis that morbidity prevalence predicts a subsequent decrease in gut microbiota maturity or diversity in rural Malawian children. Certain morbidity symptoms may be predictive of microbiota maturity and diversity and relative abundances of several bacterial taxa. Furthermore, microbiota diversity and maturity may be associated with the subsequent incidence of fever.
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Interplay between food and gut microbiota in health and disease.
Danneskiold-Samsøe, NB, Dias de Freitas Queiroz Barros, H, Santos, R, Bicas, JL, Cazarin, CBB, Madsen, L, Kristiansen, K, Pastore, GM, Brix, S, Maróstica Júnior, MR
Food research international (Ottawa, Ont.). 2019;:23-31
Abstract
Numerous microorganisms colonize the human gastrointestinal tract playing pivotal roles in relation to digestion and absorption of dietary components. They biotransform food components and produce metabolites, which in combination with food components shape and modulate the host immune system and metabolic responses. Reciprocally, the diet modulates the composition and functional capacity of the gut microbiota, which subsequently influence host biochemical processes establishing a system of mutual interaction and inter-dependency. Macronutrients, fibers, as well as polyphenols and prebiotics are strong drivers shaping the composition of the gut microbiota. Especially, short-chain fatty acids produced from ingested fibers and tryptophan metabolites are key in modulating host immune responses. Since reciprocal interactions between diet, host, and microbiota are personal, understanding this complex network of interactions calls for novel use of large datasets and the implementation of machine learning algorithms and artificial intelligence. In this review, we aim to provide a base for future investigations of how interactions between food components and gut microbiota may influence or even determine human health and disease.
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Type VI Secretion Systems and the Gut Microbiota.
Coyne, MJ, Comstock, LE
Microbiology spectrum. 2019;(2)
Abstract
The human colonic microbiota is a dense ecosystem comprised of numerous microbes, including bacteria, phage, fungi, archaea, and protozoa, that compete for nutrients and space. Studies are beginning to reveal the antagonistic mechanisms that gut bacteria use to compete with other members of this ecosystem. In the healthy human colon, the majority of the Gram-negative bacteria are of the order Bacteroidales. Proteobacteria, such as Escherichia coli, are numerically fewer but confer important properties to the host, such as colonization resistance. Several enteric pathogens use type VI secretion systems (T6SSs) to antagonize symbiotic gut E. coli, facilitating colonization and disease progression. T6SS loci are also widely distributed in human gut Bacteroidales, which includes three predominant genera: Bacteroides, Parabacteroides, and Prevotella. There are three distinct genetic architectures of T6SS loci among the gut Bacteroidales, termed GA1, GA2, and GA3. GA1 and GA2 T6SS loci are contained on integrative and conjugative elements and are the first T6SS loci shown to be readily transferred in the human gut between numerous species and families of Bacteroidales. In contrast, the GA3 T6SSs are present exclusively in Bacteroides fragilis. There are divergent regions in all three T6SS GAs that contain genes encoding effector and immunity proteins, many of which function by unknown mechanisms. To date, only the GA3 T6SSs have been shown to antagonize bacteria, and they target nearly all gut Bacteroidales species analyzed. This review delves more deeply into properties of the T6SSs of these human gut bacteria and the ecological outcomes of their synthesis in vivo.
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Microbiome 101: Studying, Analyzing, and Interpreting Gut Microbiome Data for Clinicians.
Allaband, C, McDonald, D, Vázquez-Baeza, Y, Minich, JJ, Tripathi, A, Brenner, DA, Loomba, R, Smarr, L, Sandborn, WJ, Schnabl, B, et al
Clinical gastroenterology and hepatology : the official clinical practice journal of the American Gastroenterological Association. 2019;(2):218-230
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Abstract
Advances in technical capabilities for reading complex human microbiomes are leading to an explosion of microbiome research, leading in turn to intense interest among clinicians in applying these techniques to their patients. In this review, we discuss the content of the human microbiome, including intersubject and intrasubject variability, considerations of study design including important confounding factors, and different methods in the laboratory and on the computer to read the microbiome and its resulting gene products and metabolites. We highlight several common pitfalls for clinicians, including the expectation that an individual's microbiome will be stable, that diet can induce rapid changes that are large compared with the differences among subjects, that everyone has essentially the same core stool microbiome, and that different laboratory and computational methods will yield essentially the same results. We also highlight the current limitations and future promise of these techniques, with the expectation that an understanding of these considerations will help accelerate the path toward routine clinical application of these techniques developed in research settings.
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Role of the Gut Microbiota in Atopic Dermatitis: A Systematic Review.
Petersen, EBM, Skov, L, Thyssen, JP, Jensen, P
Acta dermato-venereologica. 2019;(1):5-11
Abstract
The immune mechanisms involved in atopic dermatitis (AD) are complex and little is known about the possible role of the gut microbiota in the aetiopathogenesis of AD. A systematic review of the literature was performed according to PRISMA guidelines, and included 44 of 2,199 studies (26 observational and 18 interventional studies). Detection of gut microbiota was performed by either 16s rRNA PCR, or by culture. Observational studies were diverse regarding the age of study participants and the bacterial species investigated. Overall, the results were conflicting with regard to diversity of the gut microbiota, specific bacterial colonization, and subsequent risk of AD. Nearly half of the included interventional studies showed that an altered gut microbial colonization due to use of probiotics had a positive effect on the severity of AD. The remaining studies did not show an effect of probiotics on the severity of AD despite an alteration in the gut microbial composition. The role of the gut microbiome for the onset and severity of pre-existing AD remains controversial.
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Safety assessment of L-lysine oral intake: a systematic review.
Hayamizu, K, Oshima, I, Fukuda, Z, Kuramochi, Y, Nagai, Y, Izumo, N, Nakano, M
Amino acids. 2019;(4):647-659
Abstract
Currently, the use of amino acids in supplements and functional foods is increasing globally. However, there are no guidelines for the upper limit of ingestion for the safe use of these amino acids. Safety evaluation of chemical substances is generally performed through non-clinical and clinical studies. However, amino acids that have these safety data are limited. Therefore, we used a systematic review approach for evaluating the safety of amino acids. In the present study, we evaluated the safety of L-lysine added to an ordinary diet in humans. Using PubMed, Cochrane Library, Ichushi Web, and EBSCOhost as search databases, we comprehensively searched human studies on oral ingestion of L-lysine. Ultimately, 71 studies were selected for evaluation. Of these, 12 studies were of relatively high quality with Jadad scores ≥ 3. The dose range of L-lysine in the selected studies was 16.8-17,500 mg/day, and the range of dosing period was 1-1095 days. The observed adverse events were mainly subjective symptoms related to the gastrointestinal tract such as nausea, stomachache, and diarrhea. The provisional no-observed-adverse-effect level obtained based on these gastrointestinal symptoms was 6000 mg/person/day. Integrated analysis of the risk for developing gastrointestinal symptoms revealed that the risk ratio was 1.02 (95% CI, 0.96-1.07; p = 0.49); thus, no significant increase was observed. (UMIN000028914).
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Mechanisms controlling hormone secretion in human gut and its relevance to metabolism.
Martin, AM, Sun, EW, Keating, DJ
The Journal of endocrinology. 2019;(1):R1-R15
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Abstract
The homoeostatic regulation of metabolism is highly complex and involves multiple inputs from both the nervous and endocrine systems. The gut is the largest endocrine organ in our body and synthesises and secretes over 20 different hormones from enteroendocrine cells that are dispersed throughout the gut epithelium. These hormones include GLP-1, PYY, GIP, serotonin, and CCK, each of whom play pivotal roles in maintaining energy balance and glucose homeostasis. Some are now the basis of several clinically used glucose-lowering and weight loss therapies. The environment in which these enteroendocrine cells exist is also complex, as they are exposed to numerous physiological inputs including ingested nutrients, circulating factors and metabolites produced from neighbouring gut microbiome. In this review, we examine the diverse means by which gut-derived hormones carry out their metabolic functions through their interactions with different metabolically important organs including the liver, pancreas, adipose tissue and brain. Furthermore, we discuss how nutrients and microbial metabolites affect gut hormone secretion and the mechanisms underlying these interactions.
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Nutritional role of amniotic fluid: clues from infants with congenital obstruction of the digestive tract.
Hall, NJ, Drewett, M, Burge, D
Archives of disease in childhood. Fetal and neonatal edition. 2019;(2):F199-F201
Abstract
AIMS: To investigate the role played by amniotic fluid in late fetal nutrition by analysis of infants born with digestive tract atresia. METHODS Birth weight (BW), gestational age and gender of infants born with oesophageal (OA), duodenal (DA), jejunal (JA) and ileal atresia (IA) were recorded and BW Z-scores compared. Infants with incomplete obstruction (stenosis), chromosomal or syndromic conditions and multiple congenital malformations were excluded. Term infants admitted with suspected postnatal intestinal obstruction in whom no congenital malformation was found were used as a control group. RESULTS A total of 584 infants were identified comprising 148 OA, 60 DA, 26 JA and 57 IA with 293 in the control group. Infants with OA and DA had statistically significantly lower BW Z-score than controls. However, BW Z-score for infants with more distal atresia (JA and IA) was similar to controls. When compared with infants with OA, BW Z-score for infants with more distal atresia was higher than that for OA. BW Z-score in infants with OA was significantly lower in those born at term compared with those born preterm (mean±SD -0.92±1.0 vs -0.48±0.87; p=0.01) with a significant negative correlation between BW Z-score and increasing gestational age (R2=0.12; p<0.0001). This effect of gestational age was not seen in other atresias. CONCLUSION These observations support the concept that reduced enteral absorption of amniotic fluid due to high digestive tract obstruction in utero reduces fetal growth. The effect is greater when the obstruction is more proximal and with advancing gestation.
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Targeting the Gut Microbiota to Treat Cachexia.
Genton, L, Mareschal, J, Charretier, Y, Lazarevic, V, Bindels, LB, Schrenzel, J
Frontiers in cellular and infection microbiology. 2019;:305
Abstract
Cachexia occurs in many chronic diseases and is associated with increased morbidity and mortality. It is treated by nutritional support but often with limited effectiveness, leading to the search of other therapeutic strategies. The modulation of gut microbiota, whether through pro-, pre-, syn- or antibiotics or fecal transplantation, is attracting ever-growing interest in the field of obesity, but could also be an interesting and innovative alternative for treating cachexia. This article reviews the evidence linking the features of malnutrition, as defined by the Global Leadership Initiative on Malnutrition [low body mass index (BMI), unintentional body weight loss, low muscle mass, low appetite, and systemic inflammation] and the gut microbiota in human adults with cachexia-associated diseases, and shows the limitations of the present research in that field with suggestions for future directions.
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The effect of diets delivered into the gastrointestinal tract on gut motility after colorectal surgery-a systematic review and meta-analysis of randomised controlled trials.
Hogan, S, Steffens, D, Rangan, A, Solomon, M, Carey, S
European journal of clinical nutrition. 2019;(10):1331-1342
Abstract
BACKGROUND/OBJECTIVES Despite best practice guidelines, feeding methods after colorectal surgery vary due to the difficulties translating evidence into practice. The aim was to determine the effectiveness of diets delivered into the gastrointestinal tract (GIT) on gut motility following colorectal surgery. SUBJECTS/METHODS EMBASE, MEDLINE, CINAHL, Web of Science and PubMed were systematically searched. Randomised controlled trials investigating effectiveness of a diet on gut motility after colorectal surgeries were included. Outcomes included postoperative ileus, length of stay, mortality, nausea and vomiting. RESULTS A total of 756 potential studies were identified; of these, 10 trials reporting on 1237 unique patients were included. There is evidence that early feeding reduces time (days) to first flatus (mean difference (MD):-0.64; 95% CI:-0.84 to -0.44) and bowel movements (MD:-0.64; 95% CI:-1.01 to -0.26), when compared to traditional postoperative fasting. Introducing solids versus the progression of fluids to solids had no effect on time (days) to first flatus (MD:0.13; 95% CI:-1.99 to 1.74) or bowel movement (MD:0.20; 95% CI:-0.50 to 0.98). Complete nutrition compared to hypocaloric nutrition had no effect on time to first flatus (MD:-0.60; 95% CI:-1.66 to 0.46) or bowel movement (MD:-0.20; 95% CI:-1.59 to 1.19), whereas coffee and diet compared to water and diet significantly decreased time (days) to first bowel movement (MD:-0.60; 95% CI:-0.97 to -0.19) but had no effect on time to first flatus (MD:-0.20; 95% CI:-0.57 to 0.09). CONCLUSIONS Any form of early postoperative diet provided into the GIT early after colorectal surgery is likely to stimulate gut motility, resulting in earlier return of bowel function and shorter length of stay.