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Mediterranean Diet to Prevent the Development of Colon Diseases: A Meta-Analysis of Gut Microbiota Studies.
Illescas, O, Rodríguez-Sosa, M, Gariboldi, M
Nutrients. 2021;(7)
Abstract
Gut microbiota dysbiosis is a common feature in colorectal cancer (CRC) and inflammatory bowel diseases (IBD). Adoption of the Mediterranean diet (MD) has been proposed as a therapeutic approach for the prevention of multiple diseases, and one of its mechanisms of action is the modulation of the microbiota. We aimed to determine whether MD can be used as a preventive measure against cancer and inflammation-related diseases of the gut, based on its capacity to modulate the local microbiota. A joint meta-analysis of publicly available 16S data derived from subjects following MD or other diets and from patients with CRC, IBD, or other gut-related diseases was conducted. We observed that the microbiota associated with MD was enriched in bacteria that promote an anti-inflammatory environment but low in taxa with pro-inflammatory properties capable of altering intestinal barrier functions. We found an opposite trend in patients with intestinal diseases, including cancer. Some of these differences were maintained even when MD was compared to healthy controls without a defined diet. Our findings highlight the unique effects of MD on the gut microbiota and suggest that integrating MD principles into a person's lifestyle may serve as a preventive method against cancer and other gut-related diseases.
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Effect of traditional Chinese medicine on gut microbiota in adults with type 2 diabetes: A systematic review and meta-analysis.
Zheng, Y, Ding, Q, Wei, Y, Gou, X, Tian, J, Li, M, Tong, X
Phytomedicine : international journal of phytotherapy and phytopharmacology. 2021;:153455
Abstract
BACKGROUND Despite advances in research on type 2 diabetes mellitus (T2DM) with the development of science and technology, the pathogenesis and treatment response of T2DM remain unclear. Recent studies have revealed a significant role of the microbiomein the development of T2DM, and studies have found that the gut microbiota may explain the therapeutic effect of traditional Chinese medicine (TCM), a primary branch of alternative and complementary medicine, in the treatment of T2DM. The aim of this study was to systematically review all randomized controlled trials (RCTs) on TCM for gut microbiota to assess the effectiveness and safety of TCM in T2DM patients. METHODS All RCTs investigating the effects of TCM interventions on modulating gut microbiota and improving glucose metabolism in the treatment of T2DM adults were included. Meta-analyses were conducted when sufficient data were available, other results were reported narratively. The study protocol was pre-specified, documented, and published in PROSPERO (registration no. CRD42020188043). RESULTS Five studies met the eligibility criteria ofthe systematic review. All five studies reported the effects of TCM interventions on the gut microbiota modulation and blood glucose control. There were statistically significant improvements in HbA1c (mean difference [MD]: -0.69%; [95% CI -0.24, -0.14]; p = 0.01, I2 = 86%), fasting blood glucose (MD: -0.87 mmol/l; [95% CI -1.26, -0.49]; p < 0.00001, I2 = 75%) and 2-h postprandial blood glucose(MD: -0.83mmol/l; [95% CI: -1.01, -0.65]; p < 0.00001, I2 = 0%). In addition, there were also statistically significant improvements in homeostasis model assessment of insulin resistance (HOMA-IR) (standardized mean difference [SMD]: -0.99, [95% CI -1.25 to -0.73]; p < 0.00001, I2 = 0%) and homeostasis model assessment of β-cell function (HOMA-β) (SMD: 0.54, [95% CI 0.21 to 0.87]; p = 0.001, I2 = 0%).There was a significant change in the relative abundance of bacteria in the genera Bacteroides (standardized mean difference [SMD] 0.87%; [95% CI 0.58, 1.16], however, the change in Enterococcus abundance was not statistically significant (SMD: -1.71%; [95% CI: -3.64, 0.23]; p = 0.08) when comparing TCM supplementaltreatment with comparator groups. Other changes in the gut microbiota, including changes in the relative abundances of some probiotics and opportunistic pathogens at various taxon levels, and changes in diversity matrices (α and β), were significant by narrative analysis. However, insufficient evidences were found to support that TCM intervention had an effect on inflammation. CONCLUSION TCM had the effect of modulating gut microbiota and improving glucose metabolisms in T2DM patients. Although the results of the included studies are encouraging, further well-conducted studies on TCM interventions targeting the gut microbiota are needed.
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Diet and Pre-Intervention Washout Modifies the Effects of Probiotics on Gestational Diabetes Mellitus: A Comprehensive Systematic Review and Meta-Analysis of Randomized Controlled Trials.
Hasain, Z, Che Roos, NA, Rahmat, F, Mustapa, M, Raja Ali, RA, Mokhtar, NM
Nutrients. 2021;(9)
Abstract
Dynamic interactions among gestational diabetes mellitus (GDM), gut microbiota, inflammation, oxidative stress, and probiotics are increasingly acknowledged. This meta-analysis aimed to summarize the effects of probiotics in GDM, focusing on lifestyle intervention and pre-intervention washout, in addition to metabolic, inflammation, oxidative stress, and pregnancy outcomes. Three electronic databases (i.e., PubMed, Scopus, and CENTRAL) were searched from inception until October 2020. A meta-analysis was performed, and the effect sizes were reported as either mean differences or odds ratios with 95% confidence intervals. Altogether, 10 randomized controlled trials enrolling 594 participants were included. The meta-analysis indicated that probiotics supplementation effectively reduced fasting plasma glucose by 3.10 mg/dL, and subgroup analyses suggested that the duration of intervention, number of species, pre-intervention washout period, and dietary intervention may determine the effects of probiotics. Probiotics also reduced the level of inflammatory markers (high-sensitivity C-reactive protein, interleukin-6, tumor necrosis factor-α, and malondialdehyde), incidence of macrosomia, and newborn hospitalization. In conclusion, this meta-analysis suggests that probiotics may have positive effects on metabolic, inflammation, oxidative stress, and neonatal outcomes in women with GDM. Additionally, diet and pre-intervention washout may modify the effects of probiotics. Future studies are warranted on a larger scale to ascertain the clinical significance.
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Effects of Low Protein Diet on Modulating Gut Microbiota in Patients with Chronic Kidney Disease: A Systematic Review and Meta-analysis of International Studies.
Hsu, CK, Su, SC, Chang, LC, Shao, SC, Yang, KJ, Chen, CY, Chen, YT, Wu, IW
International journal of medical sciences. 2021;(16):3839-3850
Abstract
Background: Although associations between low protein diet (LPD) and changes of gut microbiota have been reported; however, systematic discernment of the effects of LPD on diet-microbiome-host interaction in patients with chronic kidney disease (CKD) is lacking. Methods: We searched PUBMED and EMBASE for articles published on changes of gut microbiota associated with implementation of LPD in CKD patients until July 2021. Independent researchers extracted data and assessed risks of bias. We conducted meta-analyses of combine p-value, mean differences and random effects for gut microbiota and related metabolites. Study heterogeneity was measured by Tau2 and I2 statistic. This study followed the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines. Results: Five articles met inclusion criteria. The meta-analyses of gut microbiota exhibited enrichments of Lactobacillaceae (meta-p= 0.010), Bacteroidaceae (meta-p= 0.048) and Streptococcus anginosus (meta-p< 0.001), but revealed depletion of Bacteroides eggerthii (p=0.017) and Roseburia faecis (meta-p=0.019) in LPD patients compared to patients undergoing normal protein diet. The serum IS levels (mean difference: 0.68 ug/mL, 95% CI: -8.38-9.68, p= 0.89) and pCS levels (mean difference: -3.85 ug/mL, 95% CI: -15.49-7.78, p < 0.52) did not change between groups. We did not find significant differences on renal function associated with change of microbiota between groups (eGFR, mean difference: -7.21 mL/min/1.73 m2, 95% CI: -33.2-18.79, p= 0.59; blood urea nitrogen, mean difference: -6.8 mg/dL, 95% CI: -46.42-32.82, p= 0.74). Other clinical (sodium, potassium, phosphate, albumin, fasting sugar, uric acid, total cholesterol, triglycerides, C-reactive protein and hemoglobin) and anthropometric estimates (body mass index, systolic blood pressure and diastolic blood pressure) did not differ between the two groups. Conclusions: This systematic review and meta-analysis suggested that the effects of LPD on the microbiota were observed predominantly at the families and species levels but minimal on microbial diversity or richness. In the absence of global compositional microbiota shifts, the species-level changes appear insufficient to alter metabolic or clinical outputs.
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5.
Maternal exposures and the infant gut microbiome: a systematic review with meta-analysis.
Grech, A, Collins, CE, Holmes, A, Lal, R, Duncanson, K, Taylor, R, Gordon, A
Gut microbes. 2021;(1):1-30
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Abstract
Early life, including the establishment of the intestinal microbiome, represents a critical window of growth and development. Postnatal factors affecting the microbiome, including mode of delivery, feeding type, and antibiotic exposure have been widely investigated, but questions remain regarding the influence of exposures in utero on infant gut microbiome assembly. This systematic review aimed to synthesize evidence on exposures before birth, which affect the early intestinal microbiome. Five databases were searched in August 2019 for studies exploring pre-pregnancy or pregnancy 'exposure' data in relation to the infant microbiome. Of 1,441 publications identified, 76 were included. Factors reported influencing microbiome composition and diversity included maternal antibiotic and probiotic uses, dietary intake, pre-pregnancy body mass index (BMI), gestational weight gain (GWG), diabetes, mood, and others. Eleven studies contributed to three meta-analyses quantifying associations between maternal intrapartum antibiotic exposure (IAP), BMI and GWG, and infant microbiome alpha diversity (Shannon Index). IAP, maternal overweight/obesity and excessive GWG were all associated with reduced diversity. Most studies were observational, few included early recruitment or longitudinal follow-up, and the timing, frequency, and methodologies related to stool sampling and analysis were variable. Standardization and collaboration are imperative to enhance understanding in this complex and rapidly evolving area.
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The effect of interventions targeting gut microbiota on depressive symptoms: a systematic review and meta-analysis.
Hofmeister, M, Clement, F, Patten, S, Li, J, Dowsett, LE, Farkas, B, Mastikhina, L, Egunsola, O, Diaz, R, Cooke, NCA, et al
CMAJ open. 2021;(4):E1195-E1204
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Abstract
BACKGROUND Despite their popularity, the efficacy of interventions targeting gut microbiota to improve depressive symptoms is unknown. Our objective is to summarize the effect of microbiome-targeting interventions on depressive symptoms. METHODS We conducted a systematic review and meta-analysis. We searched MEDLINE, Embase, PsycINFO, Database of Abstracts of Reviews of Effects, Cochrane Database of Systematic Reviews and the Cochrane Controlled Register of Trials from inception to Mar. 5, 2021. We included studies that evaluated probiotic, prebiotic, synbiotic, paraprobiotic or fecal microbiota transplant interventions in an adult population (age ≥ 18 yr) with an inactive or placebo comparator (defined by the absence of active intervention). Studies must have measured depressive symptoms with a validated scale, and used a randomized controlled trial study design. We conducted a random effects meta-analysis of change scores, using standardized mean difference as the measure of effect. RESULTS Sixty-two studies formed the final data set, with 50 included in the meta-analysis. Probiotic, prebiotic, and synbiotic interventions on depressive symptoms showed statistically significant benefits. In the single studies evaluating each of fecal microbiota transplant and paraprobiotic interventions, neither showed a statistically significant benefit. INTERPRETATION Despite promising findings of benefit of probiotic, prebiotic and synbiotic interventions for depressive symptoms in study populations, there is not yet strong enough evidence to favour inclusion of these interventions in treatment guidelines for depression. Critical questions about species administered, dosage and timing relative to other antidepressant medications remain to be answered. STUDY REGISTRATION PROSPERO no. 143178.
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The effects of inulin on gut microbial composition: a systematic review of evidence from human studies.
Le Bastard, Q, Chapelet, G, Javaudin, F, Lepelletier, D, Batard, E, Montassier, E
European journal of clinical microbiology & infectious diseases : official publication of the European Society of Clinical Microbiology. 2020;(3):403-413
Abstract
BACKGROUND Inulin, consisting of repetitive fructosyl units linked by β(2,1) bonds, is a readily fermentable fiber by intestinal bacteria that generates large quantities of short-chain fatty acids (SCFA). In individuals with constipation, it was reported that inulin ingestion was associated with a significant increase in stool frequency, suggesting a potential impact of inulin on human gut microbiota composition. Progress in high-throughput technologies allow assessment of human-associated microbiomes in terms of diversity and taxonomic or functional composition, and can identify changes in response to a specific supplementation. Hence, to understand the effects of inulin on the human gut microbiome is pivotal to gain insight into their mechanisms of action. METHODS Here, we conducted a systematic review of human studies in adult individuals showing the effects of inulin on the gut microbiome. We searched in MEDLINE, EMBASE, Web of Science, and Scopus databases for articles in English published in peer-reviewed journals and indexed up until March 2019. We used multiple search terms capturing gut microbiome, gut microflora, intestinal microbiota, intestinal flora, gut microbiota, gut flora, microbial gut community, gut microbial composition, and inulin. RESULTS Overall, nine original articles reported the effects of inulin on microbiome composition in adult humans, most of them being randomized, double-blind, placebo-controlled trials (n = 7). Studies varied significantly in design (3 studies associated inulin and oligofructose), supplementation protocols (from 5 to 20 gr per day of inulin consumed) and in microbiome assessment methods (16S sequencing, n = 7). The most consistent change was an increase in Bifidobacterium. Other concordant results included an increase in relative abundance of Anaerostipes, Faecalibacterium, and Lactobacillus, and a decrease in relative abundance of Bacteroides after inulin supplementation. CONCLUSIONS Our systematic review assessed the evidence for the effects of inulin supplementation on the human gut microbiome. However, these in vivo studies did not confirm in vitro experiments as the taxonomic alterations were not associated with increase in short-chain fatty acids levels.
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Novel findings of the association between gut microbiota-derived metabolite trimethylamine N-oxide and inflammation: results from a systematic review and dose-response meta-analysis.
Farhangi, MA, Vajdi, M
Critical reviews in food science and nutrition. 2020;(16):2801-2823
Abstract
The gut microbiota-derived metabolite trimethylamine N-oxide (TMAO) has been regarded as one of the potent risk factors of cardiovascular events and diabetes. However, its association with possible inflammatory mediators has not been revealed yet. In the current meta-analysis, we quantitatively summarized the results of studies regarding the association between TMAO and inflammation. Electronic databases including PubMed, ProQuest, Scopus, and Embase were systematically searched and a total of 586 manuscripts were retrieved. After removing 223 duplicates, 363 manuscripts were reviewed. All of the studies regarding the association between TMAO and inflammatory factors were included in the systematic review and eligible studies were included in to the meta-analysis. Accordingly, 13,783 number of participants were included and the results showed that being in the highest category of TMAO Accordingly was associated with 0.27 mg/L (weighted mean difference: 0.268; 95% confidence interval [CI]: 0.058-0.479; p = 0.013) increase in CRP concentrations compared with lowest category. The results of subgrouping and meta-regression revealed the location, CRP sample source, disease status, male percent, proportion of diabetes and smoking as the source of heterogeneity. Moreover, the dose-response meta-analysis revealed a non-linear association between increased TMAO concentrations and increased CRP concentrations (p for nonlinearity = 0.015). To our knowledge, this is first dose-response meta-analysis that summarized the results of studies about the association between circulating TMAO concentrations and inflammation risk.
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The Role of Dietary Fibre in Modulating Gut Microbiota Dysbiosis in Patients with Type 2 Diabetes: A Systematic Review and Meta-Analysis of Randomised Controlled Trials.
Ojo, O, Feng, QQ, Ojo, OO, Wang, XH
Nutrients. 2020;(11)
Abstract
BACKGROUND The prevalence of type 2 diabetes is on the increase worldwide, and it represents about 90% of adults who are diagnosed with diabetes. Overweight and obesity, lifestyle, genetic predisposition and gut microbiota dysbiosis have been implicated as possible risk factors in the development of type 2 diabetes. In particular, low intake of dietary fibre and consumption of foods high in fat and sugar, which are common in western lifestyle, have been reported to contribute to the depletion of specific bacterial taxa. Therefore, it is possible that intake of high dietary fibre may alter the environment in the gut and provide the needed substrate for microbial bloom. AIM: The current review is a systematic review and meta-analysis which evaluated the role of dietary fibre in modulating gut microbiota dysbiosis in patients with type 2 diabetes. METHODS This is a systematic review and meta-analysis of randomised controlled trials which relied on the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) framework. Electronic searches were conducted using EBSCOHost with links to Health Sciences Research Databases, EMBASE and Google Scholar. The reference lists of articles were also searched for relevant studies. Searches were conducted from date of commencement of the database to 5 August 2020. The search strategy was based on the Population, Intervention, Comparator, Outcomes, Studies (PICOS) framework and involved the use of synonyms and medical subject headings (MesH). Search terms were combined with Boolean operators (OR/AND). RESULTS Nine studies which met the inclusion criteria were selected for the systematic review and meta-analysis, and four distinct areas were identified: the effect of dietary fibre on gut microbiota; the role of dietary fibre on short-chain fatty acids (SCFAs); glycaemic control; and adverse events. There was significant difference (p < 0.01) in the relative abundance of Bifidobacterium with a mean difference of 0.72 (95% CI, 0.56, 0.89) between the dietary fibre group compared with placebo. In relation to the meta-analysis for SCFAs, while there was significant difference (p = 0.02) between the dietary fibre group and placebo with a standardised mean difference of 0.5 (95% CI, 0.08, 0.91) regarding total SCFAs, the differences were not significant (p > 0.05) in relation to acetic acid, propionic acid and butyric acid. There was only significant improvement (p = 0.002) with respect to glycated haemoglobin with a mean difference of -0.18 (95% CI, -0.29, -0.06) between the dietary fibre group and placebo group. Differences between the two groups were not significant (p > 0.05) in relation to fasting blood glucose and homeostatic model assessment of insulin resistance (HOMA-IR). Furthermore, there were no significant differences between the two groups in subjects who reported adverse events. It is possible that the promotion of SCFA producers in greater diversity and abundance by dietary fibre in this review led to improvement in glycated haemoglobin, partly due to increased glucagon-like peptide-1 (GLP-1) production. In addition, Bifidobacterium lactis has been reported to increase glycogen synthesis, decrease expression of hepatic gluconeogenesis genes, improve translocation of glucose transport-4 and promote glucose uptake. It is also possible that the reduction in body weight of participants in the intervention group compared with control may have contributed to the observed improvement in glycated haemoglobin. CONCLUSION This systematic review and meta-analysis have demonstrated that dietary fibre can significantly improve (p < 0.05) the relative abundance of Bifidobacterium, total SCFAs and glycated haemoglobin. However, dietary fibre did not appear to have significant effect (p > 0.05) on fasting blood glucose, HOMA-IR, acetic acid, propionic acid, butyric acid and adverse events.
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Gut microbiota-derived metabolite trimethylamine N-oxide (TMAO) potentially increases the risk of obesity in adults: An exploratory systematic review and dose-response meta- analysis.
Dehghan, P, Farhangi, MA, Nikniaz, L, Nikniaz, Z, Asghari-Jafarabadi, M
Obesity reviews : an official journal of the International Association for the Study of Obesity. 2020;(5):e12993
Abstract
It has been suggested that trimethylamine N-oxide (TMAO) is associated with increased risk of diabetes and cardiovascular disease (CVD) morbidity and mortality. However, it is not known whether increased TMAO concentrations is associated with obesity. In the current study, we summarized the evidence related to the association of circulating TMAO with the risk of obesity measurements, including body mass index (BMI), waist circumference (WC), and waist-to-hip ratio (WHR) in a two-class and dose-response meta-analysis of observational studies. A systematic search carried out in PubMed, SCOPUS, Cochrane, and ProQuest through September 30, 2019 resulted in 12 eligible studies which were included in the current meta-synthesis. In these studies, BMI was reported but there were no reports of WC or WHR. Meta-analysis of two-class variables and dose-response meta-analysis of continuous variables were performed. Subgroup analysis and meta-regression were also performed to identify the source of heterogeneity. There was a dose-response association between circulating TMAO concentration and increased BMI in studies involving healthy individuals (P nonlinearity = .007), while no evidence of departure from linearity was observed according to study design or among patients with CVD. Results showed the highest category of TMAO was associated with 0.56 kg/m2 increase in BMI (weighted mean difference [WMD], 0.563; CI, 0.026-1.100; P = .04). The results of the current meta-analysis revealed a positive association between circulating TMAO and obesity as presented by increased BMI. Moreover, a dose-dependent association between circulating TMAO and obesity was also identified in apparently healthy individuals. This is the first meta-analysis to reveal positive dose-dependent associations between circulating TMAO concentration and obesity.