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Alterations of gut microbiota are associated with blood pressure: a cross-sectional clinical trial in Northwestern China.
Lv, J, Wang, J, Yu, Y, Zhao, M, Yang, W, Liu, J, Zhao, Y, Yang, Y, Wang, G, Guo, L, et al
Journal of translational medicine. 2023;21(1):429
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Hypertension (HTN) is a complex and modifiable risk factor for cardiovascular diseases (CVDs) and stroke, while a diverse range of endogenous and environmental factors contribute to both HTN onset and progression. The adult gut microbiota (GM) consists of trillions of microorganisms and maintains the gut immunity and whole-body homeostasis. The aim of this study was to investigate the GM characteristics in HTN subjects in Northwestern China, and evaluate the associations of GM with blood pressure levels based on sex differences. This study was a cross-sectional study. Participants were randomly selected for the HTN and control groups. A total of 36 HTN subjects (24 females and 12 males) and 18 controls (9 females and 9 males) were randomly selected for metagenomic analysis. Results showed a positive association between GM characteristics and alterations and HTN in both females and males. Thus, GM dysbiosis underlies HTN pathogenesis. Authors conclude that further studies are needed to elucidate the underlying mechanisms and potential therapeutic interventions targeting GM for HTN prevention and management
Abstract
BACKGROUND The human gut microbiota (GM) is involved in the pathogenesis of hypertension (HTN), and could be affected by various factors, including sex and geography. However, available data directly linking GM to HTN based on sex differences are limited. METHODS This study investigated the GM characteristics in HTN subjects in Northwestern China, and evaluate the associations of GM with blood pressure levels based on sex differences. A total of 87 HTN subjects and 45 controls were recruited with demographic and clinical characteristics documented. Fecal samples were collected for 16S rRNA gene sequencing and metagenomic sequencing. RESULTS GM diversity was observed higher in females compared to males, and principal coordinate analysis showed an obvious segregation of females and males. Four predominant phyla of fecal GM included Firmicutes, Bacteroidetes, Actinobacteria and Proteobacteria. LEfSe analysis indicated that phylum unidentified_Bacteria was enriched in HTN females, while Leuconostocaceae, Weissella and Weissella_cibaria were enriched in control females (P < 0.05). Functionally, ROC analysis revealed that Cellular Processes (0.796, 95% CI 0.620 ~ 0.916), Human Diseases (0.773, 95% CI 0.595 ~ 0.900), Signal transduction (0.806, 95% CI 0.631 ~ 0.922) and Two-component system (0.806, 95% CI 0.631 ~ 0.922) could differentiate HTN females as effective functional classifiers, which were also positively correlated with systolic blood pressure levels. CONCLUSIONS This work provides evidence of fecal GM characteristics in HTN females and males in a northwestern Chinese population, further supporting the notion that GM dysbiosis may participate in the pathogenesis of HTN, and the role of sex differences should be considered. Trial registration Chinese Clinical Trial Registry, ChiCTR1800019191. Registered 30 October 2018 - Retrospectively registered, http://www.chictr.org.cn/ .
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Defecation status, intestinal microbiota, and habitual diet are associated with the fecal bile acid composition: a cross-sectional study in community-dwelling young participants.
Saito, Y, Sagae, T
European journal of nutrition. 2023;62(5):2015-2026
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Primary bile acids (priBAs) are synthesised from cholesterol in the human liver, conjugated with either taurine or glycine [amino acids], and secreted into the intestinal tract, where they dissolve dietary lipids. Diet is a modifiable factor that can influence defecation status, BAs, and intestinal microbiota. The aim of this study was to identify associations among defecation status, intestinal microbiota, and diet by examining faecal BA composition in community-dwelling young participants. This study was a cross-sectional study which enrolled 70 students. Results showed that 20.9% of the participants had high faecal BA levels with predominantly priBAs. This cluster was associated with an increased relative abundance of Clostridium subcluster XIVa [bacteria], increased frequency of normal faeces, and decreased relative abundance of Bacteroides and Clostridium cluster IV [bacteria]. Conversely, high levels of cytotoxic [toxic to cells] secondary BA (secBA) were associated with low normal defecation frequency, low insoluble fibre intake, and high animal fat intake. Authors concluded that among community-dwelling young adults, secBA production is affected by both dietary and lifestyle related factors. Thus, their findings may inform novel strategies for preventing colorectal cancer and cholelithiasis.
Abstract
PURPOSE Bile acid (BA) metabolism by intestinal bacteria is associated with the risk of gastrointestinal diseases; additionally, its control has become a modern strategy for treating metabolic diseases. This cross-sectional study investigated the influence of defecation status, intestinal microbiota, and habitual diet on fecal BA composition in 67 community-dwelling young participants. METHODS Feces were collected for intestinal microbiota and BA analyses; data about defecation status and dietary habits were collected using the Bristol stool form scales and a brief-type self-administered diet history questionnaire, respectively. The participants were categorized into four clusters based on their fecal BA composition, according to cluster analysis, and tertiles based on deoxycholic acid (DCA) and lithocholic acid (LCA) levels. RESULTS The high primary BA (priBA) cluster with high fecal cholic acid (CA) and chenodeoxycholic acid (CDCA) levels had the highest frequency of normal feces, whereas the second BA (secBA) cluster with high levels of fecal DCA and LCA had the lowest. Alternately, the high-priBA cluster had a distinct intestinal microbiota, with higher Clostridium subcluster XIVa and lower Clostridium cluster IV and Bacteroides. The low-secBA cluster with low fecal DCA and LCA levels had the lowest animal fat intake. Nevertheless, the insoluble fiber intake of the high-priBA cluster was significantly higher than that of the high-secBA cluster. CONCLUSION High fecal CA and CDCA levels were associated with distinct intestinal microbiota. Conversely, high levels of cytotoxic DCA and LCA were associated with increased animal fat intake and decreased frequency of normal feces and insoluble fiber intake. CLINICAL TRIAL REGISTRY University Hospital Medical Information Network (UMIN) Center system (UMIN000045639); date of registration: 15/11/2019.
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Influence of timing of maternal antibiotic administration during caesarean section on infant microbial colonisation: a randomised controlled trial.
Dierikx, T, Berkhout, D, Eck, A, Tims, S, van Limbergen, J, Visser, D, de Boer, M, de Boer, N, Touw, D, Benninga, M, et al
Gut. 2022;71(9):1803-1811
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Early-life microbiome acquisition and development can be compromised by external perturbations such as delivery via caesarean section (CS), formula feeding and antibiotics. Currently, based on revised international guidelines, all infants born by CS are exposed to broad-spectrum antibiotics via the umbilical cord. Even though there was not an increase in the incidence of neonatal sepsis, the effects on the gut microbiota colonisation and long-term health consequences remain largely unknown. The hypothesis for this study was that exposure to antibiotics in children delivered by CS, related to the revised international guidelines, influences the microbial colonisation process and may impact health outcome. This study is a randomised controlled trial on the microbiome and health state of infants up to 3 years of age. The study enrolled women delivering via CS who received antibiotics prior to skin incision (n=20) or after umbilical cord clamping (n=20) and women who had a vaginal delivery (n=23). Results show that CS delivery in general leads to a profound impact on the initial microbial colonisation. Furthermore, maternal antibiotic administration prior to CS does not lead to a ‘second hit’ on the already compromised microbiome in CS born infants. Authors conclude that early-life microbiome development is strongly affected by mode of delivery.
Abstract
OBJECTIVE Revised guidelines for caesarean section (CS) advise maternal antibiotic administration prior to skin incision instead of after umbilical cord clamping, unintentionally exposing the infant to antibiotics antenatally. We aimed to investigate if timing of intrapartum antibiotics contributes to the impairment of microbiota colonisation in CS born infants. DESIGN In this randomised controlled trial, women delivering via CS received antibiotics prior to skin incision (n=20) or after umbilical cord clamping (n=20). A third control group of vaginally delivering women (n=23) was included. Faecal microbiota was determined from all infants at 1, 7 and 28 days after birth and at 3 years by 16S rRNA gene sequencing and whole-metagenome shotgun sequencing. RESULTS Compared with vaginally born infants, profound differences were found in microbial diversity and composition in both CS groups in the first month of life. A decreased abundance in species belonging to the genera Bacteroides and Bifidobacterium was found with a concurrent increase in members belonging to the phylum Proteobacteria. These differences could not be observed at 3 years of age. No statistically significant differences were observed in taxonomic and functional composition of the microbiome between both CS groups at any of the time points. CONCLUSION We confirmed that microbiome colonisation is strongly affected by CS delivery. Our findings suggest that maternal antibiotic administration prior to CS does not result in a second hit on the compromised microbiome. Future, larger studies should confirm that antenatal antibiotic exposure in CS born infants does not aggravate colonisation impairment and impact long-term health.
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Probiotic treatment with specific lactobacilli does not improve an unfavorable vaginal microbiota prior to fertility treatment-A randomized, double-blinded, placebo-controlled trial.
Jepsen, IE, Saxtorph, MH, Englund, ALM, Petersen, KB, Wissing, MLM, Hviid, TVF, Macklon, N
Frontiers in endocrinology. 2022;13:1057022
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Efforts to improve pregnancy rates remain largely focused on enhancing the quality of the transferred embryo. However, there is increasing awareness of the potential role of the intra-uterine environment as a determinant for success. The aim of this study was to determine if lactobacilli-loaded vaginal capsules are superior to placebo in improving a vaginal microbiota reported as unfavourable to implantation in women scheduled for fertility treatment. This study is a single-centre, two-arm, double-blinded, randomised controlled study. The study enrolled women aged 18–40 years who were referred to the Fertility Clinic and whose vaginal microbiota prior to fertility treatment had been diagnosed as an unfavourable. Participants (n=77) were randomised in a 1:1 ratio to either lactobacilli-loaded vaginal capsules or placebo. Results did not show any significant effect of treatment with lactobacilli-loaded vaginal capsules on the unfavourable vaginal microbiota profile among women referred to fertility treatment. However, the study showed the highly dynamic nature of the vaginal microbiota, with a spontaneous improvement rate of 34.2% (of the patients) one to three months after the baseline sample. Authors conclude that probiotics use for the improvement of vaginal microbiota should be tempered with some caution. More studies of both the vaginal and endometrial microbiota are required to confirm the efficacy of specific vaginal probiotics before they can be considered as a therapeutic solution.
Abstract
OBJECTIVE To investigate whether treatment with proprietary lactobacilli-loaded vaginal capsules improves an unfavorable vaginal microbiome diagnosed using a commercially available test and algorithm. DESIGN A randomized, double-blinded, placebo-controlled study was conducted in 74 women prior to undergoing fertility treatment at a single university fertility clinic between April 2019 and February 2021. The women were randomly assigned in a 1:1 ratio to receive one vaginal capsule per day for 10 days containing either a culture of more than 108 CFU of Lactobacillus gasseri and more than 108 CFU Lactobacillus rhamnosus (lactobacilli group) or no active ingredient (placebo group). Vaginal swabs for microbiota analysis were taken at enrollment, after treatment and in the cycle following treatment. PARTICIPANTS AND METHODS Women aged 18-40 years who prior to fertility treatment were diagnosed with an unfavorable vaginal microbiota, characterized by either a low relative load of Lactobacillus or a high proportion of disrupting bacteria using the criteria of the IS-pro™ diagnostic system (ARTPred, Amsterdam, the Netherlands), were enrolled in the study. The primary outcome measure was the proportion of women with improvement of the vaginal microbiota after intervention. RESULTS The vaginal microbiota improved after intervention in 34.2% of all participants (lactobacilli group 28.9%, placebo group 40.0%), with no significant difference in the improvement rate between the lactobacilli and placebo groups, RR = 0.72 (95% CI 0.38-1.38). CONCLUSION This study indicates that administering vaginal probiotics may not be an effective means of modulating the vaginal microbiome for clinical purposes in an infertile population. However, a spontaneous improvement rate of 34.2% over a period of one to three months, confirming the dynamic nature of the vaginal microbiota, indicates that a strategy of postponing further IVF treatment to await microbiota improvement may be relevant in some patients, but further research is needed. CLINICAL TRIAL REGISTRATION ClinicalTrials.gov, identifier NCT03843112.
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Gut and Reproductive Tract Microbiota Adaptation during Pregnancy: New Insights for Pregnancy-Related Complications and Therapy.
Siena, M, Laterza, L, Matteo, MV, Mignini, I, Schepis, T, Rizzatti, G, Ianiro, G, Rinninella, E, Cintoni, M, Gasbarrini, A
Microorganisms. 2021;9(3)
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During pregnancy, several adaptations occur in the female organism. In fact, from fertilization until delivery, the maternal body changes and activates a series of physiological transformations to welcome the new life. The microbiota as a component of human bodies is subject to these modifications. This study is a review that focused on gut and reproductive tract microbiota variations during physiologic pregnancy and in case of pregnancy complications, particularly gestational diabetes mellitus (GDM), pre-eclampsia (PE), and preterm birth (PTB). Results show that: - during pregnancy, major changes have been seen in mothers’ gut microbiota. Between the first and third trimester of pregnancy, to support the foetus growth, there is a shift towards communities of microbes implicated in energy production and storage. - in nonpregnant women, vaginal microbiota could be classified into five major types, representing the community state types. - meconium’s microbes seems to be dominated by the Enterobacteriaceae family, suggesting prenatally stepwise colonization. - gut microbiota may contribute to enhanced insulin resistance in early pregnancy (1st and 2nd trimester). - microbiota imbalances in PE women are related not only with blood pressure levels but also with markers of kidney dysfunction. Thus, it is of key importance to understand the role of microbiota and other factors involved in the etiopathogenesis of PE - dysbiosis is related to PTB (however, further studies are necessary to better understand the correlation between this pregnancy complication and the specific microbiota alteration). Authors conclude that microbiota modulation could be a novel strategy to reduce the morbidity and mortality related to pregnancy complications in the future.
Abstract
Pregnancy is characterized by maternal adaptations that are necessary to create a welcoming and hospitable environment for the fetus. Studies have highlighted how the microbiota modulates several networks in humans through complex molecular interactions and how dysbiosis (defined as quantitative and qualitative alterations of the microbiota communities) is related to human pathologies including gynecological diseases. This review analyzed how maternal uterine, vaginal, and gut microbiomes could impact on fetus health during the gestational period. We evaluated the role of a dysbiotic microbiota in preterm birth, chorioamnionitis, gestational diabetes mellitus and pre-eclampsia. For many years it has been hypothesized that newborns were sterile organisms but in the past few years this paradigm has been questioned through the demonstration of the presence of microbes in the placenta and meconium. In the future, we should go deeper into the concept of in utero colonization to better understand the role of microbiota through the phases of pregnancy. Numerous studies in the literature have already showed interesting results regarding the role of microbiota in pregnancy. This evidence gives us the hope that microbiota modulation could be a novel strategy to reduce the morbidity and mortality related to pregnancy complications in the future.
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Non-Systematic Review of Diet and Nutritional Risk Factors of Cardiovascular Disease in Obesity.
Rychter, AM, Ratajczak, AE, Zawada, A, Dobrowolska, A, Krela-Kaźmierczak, I
Nutrients. 2020;12(3)
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Nutrition is a major factor influencing obesity associated heart disease risk, however many people with this disease do not follow nutritional recommendations. This review of 155 studies aimed to summarise dietary aspects of heart disease prevention. The paper began by outlining the role of obesity through the development of other disorders that contribute to heart disease, such as type 2 diabetes, high blood pressure and blood sugar imbalance. The quantity and distribution of fat tissue also can contribute to heart disease risk, especially if it is located within the heart or around the major organs of the body. Dietary factors which can increase heart disease risk were described as an increased intake of processed foods, sugar, salt and certain fats and low intakes of fruit, vegetables, fibre, whole grains, beans and nuts. The Mediterranean diet, the dietary approaches to stop hypertension (DASH) diet, plant-based diets, the portfolio dietary pattern and low carbohydrate diets were all reviewed and although mixed results were stated for low carbohydrate diets, most of the diets reviewed reported improved heart disease outcomes. The role of intestinal microbiota in heart disease were also reviewed and the influence of a poor diet was implicated in imbalanced gut microbiota and the development of heart disease. It was concluded that an unhealthy diet can contribute to heart disease and that dietary patterns such as the Mediterranean diet and plant-based diets may be favourable for its management. This study could be used by healthcare professionals to individualise dietary recommendations for patients with heart disease or who are at risk of it.
Abstract
Although cardiovascular disease and its risk factors have been widely studied and new methods of diagnosis and treatment have been developed and implemented, the morbidity and mortality levels are still rising-cardiovascular disease is responsible for more than four million deaths each year in Europe alone. Even though nutrition is classified as one of the main and changeable risk factors, the quality of the diet in the majority of people does not follow the recommendations essential for prevention of obesity and cardiovascular disease. It demonstrates the need for better nutritional education in cardiovascular disease prevention and treatment, and the need to emphasize dietary components most relevant in cardiovascular disease. In our non-systematic review, we summarize the most recent knowledge about nutritional risk and prevention in cardiovascular disease and obesity.
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Effect of Hesperidin on Cardiovascular Disease Risk Factors: The Role of Intestinal Microbiota on Hesperidin Bioavailability.
Mas-Capdevila, A, Teichenne, J, Domenech-Coca, C, Caimari, A, Del Bas, JM, Escoté, X, Crescenti, A
Nutrients. 2020;12(5)
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Cardiovascular diseases (CVDs) cause around 31% of all deaths worldwide. Certain dietary patterns have been associated with a reduction in CVDs and so the use of natural-based products has gained importance as a preventive strategy. Hesperidin is a bioactive compound found in high levels in citrus fruits. The reported beneficial properties include antitumor, antioxidant, anti-inflammatory; cholesterol and glucose lowering effects. Many animal studies show multiple beneficial effects but are inconclusive in human studies. The aim of this review is to describe the effects of hesperidin on CVD factors and to highlight the individual differences in its bioavailability and effectiveness. The gut bacteria play an important role in this. Hesperidin is not broken down by the normal digestive process and reaches the colon largely intact. It is the job of the gut bacteria to break it down into bioavailable substances that can be absorbed and utilised. The discrepancies observed in some of the results from human clinical trials may be partly due to individual differences, including that of the gut bacteria. Further clinical trials should be considered as well as classifying individuals according to individual differences in metabotypes.
Abstract
Recently, hesperidin, a flavonone mainly present in citrus fruits, has emerged as a new potential therapeutic agent able to modulate several cardiovascular diseases (CVDs) risk factors. Animal and in vitro studies demonstrate beneficial effects of hesperidin and its derived compounds on CVD risk factors. Thus, hesperidin has shown glucose-lowering and anti-inflammatory properties in diabetic models, dyslipidemia-, atherosclerosis-, and obesity-preventing effects in CVDs and obese models, and antihypertensive and antioxidant effects in hypertensive models. However, there is still controversy about whether hesperidin could contribute to ameliorate glucose homeostasis, lipid profile, adiposity, and blood pressure in humans, as evidenced by several clinical trials reporting no effects of treatments with this flavanone or with orange juice on these cardiovascular parameters. In this review, we focus on hesperidin's beneficial effects on CVD risk factors, paying special attention to the high interindividual variability in response to hesperidin-based acute and chronic interventions, which can be partly attributed to differences in gut microbiota. Based on the current evidence, we suggest that some of hesperidin's contradictory effects in human trials are partly due to the interindividual hesperidin variability in its bioavailability, which in turn is highly dependent on the α-rhamnosidase activity and gut microbiota composition.
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Gut Microbiota Modulation on Intestinal Mucosal Adaptive Immunity.
Wang, L, Zhu, L, Qin, S
Journal of immunology research. 2019;2019:4735040
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The mammalian intestine plays host to a vast microbiota, which is essential for the development and maintenance of the host’s immune system. This highly technical review highlights the results of recent studies on the effects and cellular and molecular mechanisms of the intestinal microbiota, and their metabolites and signals, on the development of intestinal immune cells and their functions. When the balance of the microbiota and their effects on intestinal immunity is disrupted (dysbiosis) this can lead to chronic local and systemic inflammatory and autoimmune disorders. The authors conclude that identifying microorganisms and their metabolites that can affect immunity, and the underlying mechanisms, is crucial for the development of microbiota based therapeutics.
Abstract
The mammalian intestine harbors a remarkable number of microbes and their components and metabolites, which are fundamental for the instigation and development of the host immune system. The intestinal innate and adaptive immunity coordinate and interact with the symbionts contributing to the intestinal homeostasis through establishment of a mutually beneficial relationship by tolerating to symbiotic microbiota and retaining the ability to exert proinflammatory response towards invasive pathogens. Imbalance between the intestinal immune system and commensal organisms disrupts the intestinal microbiological homeostasis, leading to microbiota dysbiosis, compromised integrity of the intestinal barrier, and proinflammatory immune responses towards symbionts. This, in turn, exacerbates the degree of the imbalance. Intestinal adaptive immunity plays a critical role in maintaining immune tolerance towards symbionts and the integrity of intestinal barrier, while the innate immune system regulates the adaptive immune responses to intestinal commensal bacteria. In this review, we will summarize recent findings on the effects and mechanisms of gut microbiota on intestinal adaptive immunity and the plasticity of several immune cells under diverse microenvironmental settings.
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The Role of Glutamine in the Complex Interaction between Gut Microbiota and Health: A Narrative Review.
Perna, S, Alalwan, TA, Alaali, Z, Alnashaba, T, Gasparri, C, Infantino, V, Hammad, L, Riva, A, Petrangolini, G, Allegrini, P, et al
International journal of molecular sciences. 2019;20(20)
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Glutamine is an amino acid, one of the building blocks of protein, and is the most abundant free amino acid in the body. Research shows that glutamine plays an important role in digestive health and immunity by supporting the integrity of the intestinal lining and suppressing inflammation. This review looks at glutamine and its mechanism on gut microbiota; the commensal bacteria which populate the gastro-intestinal tract. Glutamine supplementation was shown to beneficially affect the composition of gut bacteria in obese and overweight subjects, reduce bacterial overgrowth and more specifically reduce harmful strains of Clostridium spp. and Helicobacter spp. The subsequent increase in intestinal-friendly microbiota after supplementation aided symptoms of constipation. This same mechanism may help prevent bacterial infections in chemotherapy cancer patients which is a common side effect of the treatment. Glutamine also supports immune cell activity. White blood cells were shown to use a four-fold amount of glutamine versus glucose. There are indications of glutamine-mediated crosstalk between intestinal microbes and the immune system and that glutamine appears to be helpful in patients with severe digestive disturbances as well as metabolic stress, trauma, infection, burns and muscle-wastage.
Abstract
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.
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Impact of Fecal Microbiota Transplantation on Obesity and Metabolic Syndrome-A Systematic Review.
Zhang, Z, Mocanu, V, Cai, C, Dang, J, Slater, L, Deehan, EC, Walter, J, Madsen, KL
Nutrients. 2019;11(10)
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Fecal microbiota transplantation (FMT) is a relatively new field of scientific exploration where patients receive faeces from a healthy donor to help repopulate their intestinal tract with healthful bacteria. The gut microbiome is an ecosystem of an estimated 10~100 trillion microorganisms and there is increasing research on the important role these bacteria play in supporting our health and weight. This study reviews all trials involving faecal transports in patients with either clinical obesity or Metabolic syndrome to see if it helped improve weight, bmi or other metabolic parameters. Three studies with 76 male patients were included in this review and the results showed that FMT recipients had improved insulin sensitivity and reduced HbA1c glucose levels after 6 weeks, but these improvements were short-term only. There were no differences in bmi, cholesterol, markers and fasting glucose levels. The conclusion is that whilst FMT may confer benefits there is still much to understand about the fecal microbial preparation, dosing, and method of delivery, as well as the host patient’s response.
Abstract
Fecal microbiota transplantation (FMT) is a gut microbial-modulation strategy that has been investigated for the treatment of a variety of human diseases, including obesity-associated metabolic disorders. This study appraises current literature and provides an overview of the effectiveness and limitations of FMT as a potential therapeutic strategy for obesity and metabolic syndrome (MS). Five electronic databases and two gray literature sources were searched up to 10 December 2018. All interventional and observational studies that contained information on the relevant population (adult patients with obesity and MS), intervention (receiving allogeneic FMT) and outcomes (metabolic parameters) were eligible. From 1096 unique citations, three randomized placebo-controlled studies (76 patients with obesity and MS, body mass index = 34.8 ± 4.1 kg/m2, fasting plasma glucose = 5.8 ± 0.7 mmol/L) were included for review. Studies reported mixed results with regards to improvement in metabolic parameters. Two studies reported improved peripheral insulin sensitivity (rate of glucose disappearance, RD) at 6 weeks in patients receiving donor FMT versus patients receiving the placebo control. In addition, one study observed lower HbA1c levels in FMT patients at 6 weeks. No differences in fasting plasma glucose, hepatic insulin sensitivity, body mass index (BMI), or cholesterol markers were observed between two groups across all included studies. While promising, the influence of FMT on long-term clinical endpoints needs to be further explored. Future studies are also required to better understand the mechanisms through which changes in gut microbial ecology and engraftment of microbiota affect metabolic outcomes for patients with obesity and MS. In addition, further research is needed to better define the optimal fecal microbial preparation, dosing, and method of delivery.