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1.
Gut-brain axis: A matter of concern in neuropsychiatric disorders…!
Naveed, M, Zhou, QG, Xu, C, Taleb, A, Meng, F, Ahmed, B, Zhang, Y, Fukunaga, K, Han, F
Progress in neuro-psychopharmacology & biological psychiatry. 2021;:110051
Abstract
The gut microbiota is composed of a large number of microbes, usually regarded as commensal bacteria. It has become gradually clear that gastrointestinal microbiota affects gut pathophysiology and the central nervous system (CNS) function by modulating the signaling pathways of the microbiota-gut-brain (MGB) axis. This bidirectional MGB axis communication primarily acts through neuroendocrine, neuroimmune, and autonomic nervous systems (ANS) mechanisms. Accumulating evidence reveals that gut microbiota interacts with the host brain, and its modulation may play a critical role in the pathology of neuropsychiatric disorders. Recently, neuroscience research has established the significance of gut microbiota in the development of brain systems that are essential to stress-related behaviors, including depression and anxiety. Application of modulators of the MGB, such as psychobiotics (e.g., probiotics), prebiotics, and specific diets, may be a promising therapeutic approach for neuropsychiatric disorders. The present review article primarily focuses on the relevant features of the disturbances of the MGB axis in the pathophysiology of neuropsychiatric disorders and its potential mechanisms.
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2.
Glycyl Radical Enzymes and Sulfonate Metabolism in the Microbiome.
Wei, Y, Zhang, Y
Annual review of biochemistry. 2021;:817-846
Abstract
Sulfonates include diverse natural products and anthropogenic chemicals and are widespread in the environment. Many bacteria can degrade sulfonates and obtain sulfur, carbon, and energy for growth, playing important roles in the biogeochemical sulfur cycle. Cleavage of the inert sulfonate C-S bond involves a variety of enzymes, cofactors, and oxygen-dependent and oxygen-independent catalytic mechanisms. Sulfonate degradation by strictly anaerobic bacteria was recently found to involve C-S bond cleavage through O2-sensitive free radical chemistry, catalyzed by glycyl radical enzymes (GREs). The associated discoveries of new enzymes and metabolic pathways for sulfonate metabolism in diverse anaerobic bacteria have enriched our understanding of sulfonate chemistry in the anaerobic biosphere. An anaerobic environment of particular interest is the human gut microbiome, where sulfonate degradation by sulfate- and sulfite-reducing bacteria (SSRB) produces H2S, a process linked to certain chronic diseases and conditions.
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3.
The Neuroprotective Effect of Tea Polyphenols on the Regulation of Intestinal Flora.
Zhang, Z, Zhang, Y, Li, J, Fu, C, Zhang, X
Molecules (Basel, Switzerland). 2021;(12)
Abstract
Tea polyphenols (TPs) are the general compounds of natural polyhydroxyphenols extracted in tea. Although a large number of studies have shown that TPs have obvious neuroprotective and neuro repair effects, they are limited due to the low bioavailability in vivo. However, TPs can act indirectly on the central nervous system by affecting the "microflora-gut-brain axis", in which the microbiota and its composition represent a factor that determines brain health. Bidirectional communication between the intestinal microflora and the brain (microbe-gut-brain axis) occurs through a variety of pathways, including the vagus nerve, immune system, neuroendocrine pathways, and bacteria-derived metabolites. This axis has been shown to influence neurotransmission and behavior, which is usually associated with neuropsychiatric disorders. In this review, we discuss that TPs and their metabolites may provide benefits by restoring the imbalance of intestinal microbiota and that TPs are metabolized by intestinal flora, to provide a new idea for TPs to play a neuroprotective role by regulating intestinal flora.
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4.
Potential of Omega-3 Polyunsaturated Fatty Acids in Managing Chemotherapy- or Radiotherapy-Related Intestinal Microbial Dysbiosis.
Zhang, Y, Zhang, B, Dong, L, Chang, P
Advances in nutrition (Bethesda, Md.). 2019;(1):133-147
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Abstract
Chemotherapy- or radiotherapy-related intestinal microbial dysbiosis is one of the main causes of intestinal mucositis. Cases of bacterial translocation into peripheral blood and subsequent sepsis occur as a result of dysfunction in the intestinal barrier. Evidence from recent studies depicts the characteristics of chemotherapy- or radiotherapy-related intestinal microbial dysbiosis, which creates an imbalance between beneficial and harmful bacteria in the gut. Decreases in beneficial bacteria can lead to a weakening of the resistance of the gut to harmful bacteria, resulting in robust activation of proinflammatory signaling pathways. For example, lipopolysaccharide (LPS)-producing bacteria activate the nuclear transcription factor-κB signaling pathway through binding with Toll-like receptor 4 on stressed epithelial cells, subsequently leading to secretion of proinflammatory cytokines. Nevertheless, various studies have found that the omega-3 (n-3) polyunsaturated fatty acids (PUFAs) such as docosahexaenoic acid and eicosapentaenoic acid can reverse intestinal microbial dysbiosis by increasing beneficial bacteria species, including Lactobacillus, Bifidobacterium, and butyrate-producing bacteria, such as Roseburia and Coprococcus. In addition, the n-3 PUFAs decrease the proportions of LPS-producing and mucolytic bacteria in the gut, and they can reduce inflammation as well as oxidative stress. Importantly, the n-3 PUFAs also exert anticancer effects in colorectal cancers. In this review, we summarize the characteristics of chemotherapy- or radiotherapy-related intestinal microbial dysbiosis and introduce the contributions of dysbiosis to the pathogenesis of intestinal mucositis. Next, we discuss how n-3 PUFAs could alleviate chemotherapy- or radiotherapy-related intestinal microbial dysbiosis. This review provides new insights into the clinical administration of n-3 PUFAs for the management of chemotherapy- or radiotherapy-related intestinal microbial dysbiosis.
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Current understanding of gut microbiota alterations and related therapeutic intervention strategies in heart failure.
Chen, X, Li, HY, Hu, XM, Zhang, Y, Zhang, SY
Chinese medical journal. 2019;(15):1843-1855
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Abstract
OBJECTIVE The purpose of this review is to stress the complicated interactions between the microbiota and the development of heart failure. Moreover, the feasibility of modulating intestinal microbes and metabolites as novel therapeutic strategies is discussed. DATA SOURCES This study was based on data obtained from PubMed up to March 31, 2019. Articles were selected using the following search terms: "gut microbiota," "heart failure," "trimethylamine N-oxide (TMAO)," "short-chain fatty acid (SCFA)," "bile acid," "uremic toxin," "treatment," "diet," "probiotic," "prebiotic," "antibiotic," and "fecal microbiota transplantation." RESULTS Accumulated evidence has revealed that the composition of the gut microbiota varies obviously in people with heart failure compared to those with healthy status. Altered gut microbial communities contribute to heart failure through bacterial translocation or affecting multiple metabolic pathways, including the trimethylamine/TMAO, SCFA, bile acid, and uremic toxin pathways. Meanwhile, modulation of the gut microbiota through diet, pre/probiotics, fecal transplantation, and microbial enzyme inhibitors has become a potential therapeutic approach for many metabolic disorders. Specifically, a few studies have focused on the cardioprotective effects of probiotics on heart failure. CONCLUSIONS The composition of the gut microbiota in people with heart failure is different from those with healthy status. A reduction in SCFA-producing bacteria in patients with heart failure might be a notable characteristic for patients with heart failure. Moreover, an increase in the microbial potential to produce TMAO and lipopolysaccharides is prominent. More researches focused on the mechanisms of microbial metabolites and the clinical application of multiple therapeutic interventions is necessarily required.
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Circulating LPS and (1→3)-β-D-Glucan: A Folie à Deux Contributing to HIV-Associated Immune Activation.
Ramendra, R, Isnard, S, Mehraj, V, Chen, J, Zhang, Y, Finkelman, M, Routy, JP
Frontiers in immunology. 2019;:465
Abstract
Immune activation is the driving force behind the occurrence of AIDS and non-AIDS events, and is only partially reduced by antiretroviral therapy (ART). Soon after HIV infection, intestinal CD4+ T cells are depleted leading to epithelial gut damage and subsequent translocation of microbes and/or their products into systemic circulation. Bacteria and fungi are the two most abundant populations of the gut microbiome. Circulating lipopolysaccharide (LPS) and (1→3)-β-D-Glucan (βDG), major components of bacterial and fungal cell walls respectively, are measured as markers of microbial translocation in the context of compromised gut barriers. While LPS is a well-known inducer of innate immune activation, βDG is emerging as a significant source of monocyte and NK cell activation that contributes to immune dysfunction. Herein, we critically evaluated recent literature to untangle the respective roles of LPS and βDG in HIV-associated immune dysfunction. Furthermore, we appraised the relevance of LPS and βDG as biomarkers of disease progression and immune activation on ART. Understanding the consequences of elevated LPS and βDG on immune activation will provide insight into novel therapeutic strategies against the occurrence of AIDS and non-AIDS events.
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Analyses of gut microbiota and plasma bile acids enable stratification of patients for antidiabetic treatment.
Gu, Y, Wang, X, Li, J, Zhang, Y, Zhong, H, Liu, R, Zhang, D, Feng, Q, Xie, X, Hong, J, et al
Nature communications. 2017;(1):1785
Abstract
Antidiabetic medication may modulate the gut microbiota and thereby alter plasma and faecal bile acid (BA) composition, which may improve metabolic health. Here we show that treatment with Acarbose, but not Glipizide, increases the ratio between primary BAs and secondary BAs and plasma levels of unconjugated BAs in treatment-naive type 2 diabetes (T2D) patients, which may beneficially affect metabolism. Acarbose increases the relative abundances of Lactobacillus and Bifidobacterium in the gut microbiota and depletes Bacteroides, thereby changing the relative abundance of microbial genes involved in BA metabolism. Treatment outcomes of Acarbose are dependent on gut microbiota compositions prior to treatment. Compared to patients with a gut microbiota dominated by Prevotella, those with a high abundance of Bacteroides exhibit more changes in plasma BAs and greater improvement in metabolic parameters after Acarbose treatment. Our work highlights the potential for stratification of T2D patients based on their gut microbiota prior to treatment.
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Fructooligosaccharide (FOS) and Galactooligosaccharide (GOS) Increase Bifidobacterium but Reduce Butyrate Producing Bacteria with Adverse Glycemic Metabolism in healthy young population.
Liu, F, Li, P, Chen, M, Luo, Y, Prabhakar, M, Zheng, H, He, Y, Qi, Q, Long, H, Zhang, Y, et al
Scientific reports. 2017;(1):11789
Abstract
The gut microbiota has been implicated in glucose intolerance and its progression towards type-2 diabetes mellitus (T2DM). Relevant randomized clinical trial with prebiotic intervention was inadequate. We sought to evaluate the impact of fructooligosaccharides (FOS) and galactooligosaccharides (GOS) on glycemia during oral glucose tolerance test (OGTT) and intestinal microbiota. A randomized double-blind cross-over study was performed with 35 adults treated with FOS and GOS for 14 days (16 g/day). Faeces sampling, OGTT and anthropometric parameters were performed. Short-term intake of high-dose prebiotics had adverse effect on glucose metabolism, as in FOS intervention demonstrated by OGTT (P < 0.001), and in GOS intervention demonstrated by fasting glucose (P < 0.05). A significant increase in the relative abundance of Bifidobacterium was observed both in FOS and GOS group, while the butyrate-producing bacteria like Phascolarctobacterium in FOS group and Ruminococcus in GOS group were decreased. A random forest model using the initial microbiota was developed to predict OGTT levels after prebiotic intervention with relative success (R = 0.726). Our study alerted even though FOS and GOS increased Bifidobacterium, they might have adverse effect on glucose metabolism by reducing butyrate-producing microbes. Individualized prebiotics intervention based on gut microbiome needs to be evaluated in future.
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Healthy Subjects Differentially Respond to Dietary Capsaicin Correlating with Specific Gut Enterotypes.
Kang, C, Zhang, Y, Zhu, X, Liu, K, Wang, X, Chen, M, Wang, J, Chen, H, Hui, S, Huang, L, et al
The Journal of clinical endocrinology and metabolism. 2016;(12):4681-4689
Abstract
CONTEXT Previous population studies in evaluating the beneficial effects of capsaicin (CAP) have yielded inconclusive results, and the mechanisms responsible for possible benefit remain unclear. OBJECTIVE The objective was to assess the effect of dietary CAP on metabolic and immune profiles and its potential associations with gut microbial patterns in healthy adults. DESIGN In a 6-week controlled feeding trial, subjects were given the weight maintenance diet sequentially contained with 0, 5, 0, and 10 mg/d CAP from chili powder. SETTING AND PARTICIPANTS The study was conducted in 12 healthy subjects enrolled in Third Military Medical University in Chongqing. MAIN OUTCOME MEASURES At the end of each period, anthropometric and basal metabolism measures together with blood and fecal samples were collected. Plasma metabolic and inflammatory markers and gut microbial ecology of each subject were subsequently assessed. RESULT Dietary CAP increased the Firmicutes/Bacteroidetes ratio and Faecalibacterium abundance, accompanied with increased plasma levels of glucagon-like peptide 1 and gastric inhibitory polypeptide and decreased plasma ghrelin level. Further enterotype analysis revealed that these subjects could be clustered into Bacteroides enterotype (E1) and Prevotella enterotype (E2), and the above beneficial effects were mainly obtained in E1 subjects. Moreover, E1 subjects had significantly higher fecal Faecalibacterium abundance and butyrate concentration after CAP interventions than those in E2 subjects. CONCLUSION Our study showed that gut enterotypes may influence the beneficial effects of dietary CAP, providing new evidence for the personalized nutrition guidance of CAP intervention on health promotion linking with gut microbiota patterns.