The gut microbiota and inflammation: An overview. Int J Environ Res Public Health. 2020;17. [PMID: 33086688 PMCID: PMC7589951 DOI: 10.3390/ijerph17207618]

Cross-Talk Between Gut Microbiota and Adipose Tissues in Obesity and Related Metabolic Diseases

The rapid increase of obesity and associated diseases has become a major global health problem. Adipose tissues are critical for whole-body homeostasis. The gut microbiota has been recognized as a significant environmental factor in the maintenance of energy homeostasis and host immunity. A growing body of evidence suggests that the gut microbiota regulates host metabolism through a close cross-talk with adipose tissues. It modulates energy expenditure and alleviates obesity by promoting energy expenditure, but it also produces specific metabolites and structural components that may act as the central factors in the pathogenesis of inflammation, insulin resistance, and obesity. Understanding the relationship between gut microbiota and adipose tissues may provide potential intervention strategies to treat obesity and associated diseases. In this review, we focus on recent advances in the gut microbiota and its actions on adipose tissues and highlight the joint actions of the gut microbiota and adipose tissue with each other in the regulation of energy metabolism.

Probiotics and gut microbiota: mechanistic insights into gut immune homeostasis through TLR pathway regulation

Consumption of probiotics as a useful functional food improves the host's wellbeing, and, when paired with prebiotics (indigestible dietary fibre/carbohydrate), often benefits the host through anaerobic fermentation.

Holothurian fucosylated chondroitin sulfates and their potential benefits for human health: Structures and biological activities

Fucosylated chondroitin sulfates (FCS) are a sulfated polysaccharide exclusively existing in the body wall of sea cucumber. FCS possesses a mammalian chondroitin sulfate like backbone, namely repeating disaccharides units composed of GlcA and GalNAc, with fucosyl branches linked to GlcA and/or GalNAc residues. It is found that FCS can prevent unhealthy dietary pattern-induced metabolic syndromes, including insulin resistance and β-cell function improvement, anti-inflammation, anti-hyperlipidemia, and anti-adipogenesis. Further studies show that those activities of FCS might be achieved through positively modulating gut microbiota composition. Besides, FCS also show therapeutic efficacy in cancer, HIV infection, and side effects of cyclophosphamide. Furthermore, bioactivities of FCS are closely affected by their molecular weights, sulfation pattern of the fucosyl branches, and chain conformations. This review summarizes the recent 20 years studies to provide references for the future studies and applications of FCS in functional foods or drugs.

Prolonged NHE Activation may be both Cause and Outcome of Cytokine Release Syndrome in COVID-19

The release of cytokines and chemokines such as IL-1β, IL-2, IL-6, IL-7, IL-10, TNF-α, IFN-γ, CCL2, CCL3, and CXCL10 is increased in critically ill patients with COVID-19. Excessive cytokine release during COVID-19 is related to increased morbidity and mortality. Several mechanisms are put forward for cytokine release syndrome during COVID-19. Here we have mentioned novel pathways. SARS-CoV-2 increases angiotensin II levels by rendering ACE2 nonfunctional. Angiotensin II causes cytokine release via AT₁ and AT₂ receptors. Moreover, angiotensin II potently stimulates the Na+/H+ exchanger (NHE). It is a pump found in the membranes of many cells that pumps Na+ inward and H+ outward. NHE has nine isoforms. NHE1 is the most common isoform found in endothelial cells and many cells. NHE is involved in keeping the intracellular pH within physiological limits. When the intracellular pH is acidic, NHE is activated, bringing the intracellular pH to physiological levels, ending its activity. Sustained NHE activity is highly pathological and causes many problems. Prolonged NHE activation in COVID-19 may cause a decrease in intracellular pH through H+ ion accumulation in the extracellular area and subsequent redox reactions. The activation reduces the intracellular K+ concentration and leads to Na+ and Ca²⁺ overload. Increased ROS can cause intense cytokine release by stimulating NF-κB and NLRP3 inflammasomes. Cytokines also cause overstimulation of NHE. As the intracellular pH decreases, SARS-CoV-2 rapidly infects new cells, increasing the viral load. This vicious circle increases morbidity and mortality in patients with COVID-19. On the other hand, SARS-CoV-2 interaction with NHE3 in intestinal tissue is different from other tissues. SARS-CoV-2 can trigger CRS via NHE3 inhibition by disrupting the intestinal microbiota. This review aimed to help develop new treatment models against SARS-CoV-2- induced CRS by revealing the possible effects of SARS-CoV-2 on the NHE.

Therapeutic Strategies for Immune Transformation in Parkinson's Disease

Dysregulation of innate and adaptive immunity can lead to alpha-synuclein (α-syn) misfolding, aggregation, and post-translational modifications in Parkinson's disease (PD). This process is driven by neuroinflammation and oxidative stress, which can contribute to the release of neurotoxic oligomers that facilitate dopaminergic neurodegeneration. Strategies that promote vaccines and antibodies target the clearance of misfolded, modified α-syn, while gene therapy approaches propose to deliver intracellular single chain nanobodies to mitigate α-syn misfolding, or to deliver neurotrophic factors that support neuronal viability in an otherwise neurotoxic environment. Additionally, transformative immune responses provide potential targets for PD therapeutics. Anti-inflammatory drugs represent one strategy that principally affects innate immunity. Considerable research efforts have focused on transforming the balance of pro-inflammatory effector T cells (Teffs) to favor regulatory T cell (Treg) activity, which aims to attenuate neuroinflammation and support reparative and neurotrophic homeostasis. This approach serves to control innate microglial neurotoxic activities and may facilitate clearance of α-syn aggregates accordingly. More recently, changes in the intestinal microbiome have been shown to alter the gut-immune-brain axis leading to suppressed leakage of bacterial products that can promote peripheral inflammation and α-syn misfolding. Together, each of the approaches serves to interdict chronic inflammation associated with disordered immunity and neurodegeneration. Herein, we examine research strategies aimed at improving clinical outcomes in PD.

Fructooligosaccharides on inflammation, immunomodulation, oxidative stress, and gut immune response: a systematic review

CONTEXT

Evidence shows that fructooligosaccharides (FOSs) can modulate inflammatory, oxidative, and immune activity in the gut, possibly leading to a systemic response, improving human health.

OBJECTIVE

To assess the present knowledge of the effects of FOSs on inflammation, immunomodulation, oxidative stress, and gut immune response.

DATA SOURCES

Studies published between December 2000 and January 2020 were systematically searched in four databases: MEDLINE, LILACS, Web of Science, and Scopus. After the screening of 1316 articles, 8 human studies and 20 animal models were included.

DATA EXTRACTION

Data were extracted separately by 2 reviewers. For each study, the design, population, exposures, main results, and conclusion were extracted. The research questions and the risk-of-bias information were also extracted. Additionally, the risk-of-bias were analyzed to guarantee the reliability of this review.

DATA ANALYSIS

A qualitative analysis revealed that FOSs can increase bifidobacteria counts and short-chain fatty acids in the gut, stimulate IgA secretion in the colon, and decrease proinflammatory cytokines, thus influencing metabolic diseases.

CONCLUSION

Studies suggest that FOS supplementation is positively associated with an anti-inflammatory and antioxidant effect, thus enhancing the gut immune system, which may be beneficial for the host's health.

SYSTEMATIC REVIEW REGISTRATION

PROSPERO registration nos 42020209865 and 42020220369.

Regulatory Effect of Resveratrol on Inflammation Induced by Lipopolysaccharides via Reprograming Intestinal Microbes and Ameliorating Serum Metabolism Profiles

The purpose of this study was to explore the regulatory effect of resveratrol (RES) on lipopolysaccharide (LPS)-induced inflammation and its influence on intestinal microorganisms and serum atlas in murine models during the development of inflammation to explore a novel method for the regulation of inflammation. Mice were randomly assigned to three groups: control (CON), LPS, and RES–LPS. The results showed that RES mitigated the inflammatory damage to the intes-tines and liver induced by LPS. Compared with the LPS group, RES treatment decreased the levels of TNF-α, IL-6, IFN-γ, myeloperoxidase, and alanine aminotransferase in the liver. Serum metabolic profile monitoring showed that, compared with the CON group, LPS decreased the levels of five metabolites, including cycloartomunin and glycerol triundecanoate, and increased the levels of eight metabolites, including N-linoleoyl taurine and PE(O-16:0/20:5(5Z), 8Z, 11Z, 14Z, 17Z). Conversely, RES treatment increased the levels of eight metabolites, including pantothenic acid, homovanillic acid, and S-(formylmethyl)glutathione, and reduced seven metabolites, including lysoPE(20:4(8Z,11Z,14Z,17Z)/0:0) and 13-cis-retinoic acid, etc., in comparison with the LPS group. Moreover, RES treatment alleviated the negative effects of LPS on intestinal microbes by reducing, for instance, the relative abundance of Bacteroidetes and Alistipes, and increasing the relative abundance of Lactobacillus. These results suggest that RES has great potential for preventing in-flammation.

The gut microbiota in retinal diseases

The gut microbiota is a complex ecosystem that inhabits the gastrointestinal tract and consists of archaea, fungi, viruses, and bacteria, with bacteria being dominant. From birth onwards, it coevolves dynamically together with the host. The composition of the gut microbiota is under the influence of a complex interplay between both host and environmental factors. Scientific advances in the past few decades have shown that it is essential in maintaining homeostasis and tipping the balance between health and disease. In addition to its role in food digestion, the gut microbiota is implicated in regulating multiple physiological processes in the host gut mucosa and in distant organs such as the brain. Persistent imbalance between gut microbial communities, termed "dysbiosis," has been associated with several inflammatory and metabolic diseases as well as with central nervous system disorders. In this review, we present the state of the art of current knowledge on an emerging concept, the microbiota-retina axis, and the potential role of its disturbance in the development of retinopathies. We also describe several microbiota-targeting strategies that could constitute preventive and therapeutic tools for retinopathies.

TLR4 Deficiency Affects the Microbiome and Reduces Intestinal Dysfunctions and Inflammation in Chronic Alcohol-Fed Mice

Chronic alcohol abuse causes an inflammatory response in the intestinal tract with damage to the integrity of the mucosa and epithelium, as well as dysbiosis in the gut microbiome. However, the role of gut bacteria in ethanol effects and how these microorganisms interact with the immune system are not well understood. The aim of the present study was to evaluate if TLR4 alters the ethanol-induced intestinal inflammatory response, and whether the response of this receptor affects the gut microbiota profile. We analyzed the 16S rRNA sequence of the fecal samples from wild-type (WT) and TLR4-knockout (TLR4-KO) mice with and without ethanol intake for 3 months. The results demonstrated that chronic ethanol consumption reduces microbiota diversity and causes dysbiosis in WT mice. Likewise, ethanol upregulates several inflammatory genes (IL-1β, iNOS, TNF-α) and miRNAs (miR-155-5p, miR-146a-5p) and alters structural and permeability genes (INTL1, CDH1, CFTR) in the colon of WT mice. Our results further demonstrated that TLR4-KO mice exhibit a different microbiota that can protect against the ethanol-induced activation of the immune system and colon integrity dysfunctions. In short, our results reveal that TLR4 is a key factor for determining the gut microbiota, which can participate in dysbiosis and the inflammatory response induced by alcohol consumption.

Therapeutic Advances in Gut Microbiome Modulation in Patients with Inflammatory Bowel Disease from Pediatrics to Adulthood

There is mounting evidence that the gut microbiota plays an important role in the pathogenesis of inflammatory bowel disease (IBD). For the past decade, high throughput sequencing-based gut microbiome research has identified characteristic shifts in the composition of the intestinal microbiota in patients with IBD, suggesting that IBD results from alterations in the interactions between intestinal microbes and the host’s mucosal immune system. These studies have been the impetus for the development of new therapeutic approaches targeting the gut microbiome, such as nutritional therapies, probiotics, fecal microbiota transplant and beneficial metabolic derivatives. Innovative technologies can further our understanding of the role the microbiome plays as well as help to evaluate how the different approaches in microbiome modulation impact clinical responses in adult and pediatric patients. In this review, we highlight important microbiome studies in patients with IBD and their response to different microbiome modulation therapies, and describe the differences in therapeutic response between pediatric and adult patient cohorts.

Linking Gut Microbiota, Metabolic Syndrome and Metabolic Health among a Sample of Obese Egyptian Females

Background: Studies of the gut microbiota have revealed a great link to obesity and metabolic syndrome (MetS). The aim of this study was to review the dysbiosis of gut microbiota in terms of the components of MetS among a sample of obese Egyptian female patients and to assess current potential gut microbiota targeted therapies for the treatment of MetS. Methods: This study is a cross-sectional study included 82 obese Egyptian women.  All participants were subjected to anthropometric assessment; and  laboratory evaluation of fasting blood sugar (FBS), insulin, C-reactive protein (CRP), lipid profile and insulin resistance (HOMA), in addition to fecal microbiota analysis for Lactobacillus, Bifidobacteria, Firmicutes and Bacteroid. Results: Among obese group with MetS, Firmicutes / Bacteroidetes Ratio was negatively associated with HOMA and positively associated with serum cholesterol and LDL, while lactobacillus was negatively associated with serum cholesterol. Among obese group without MetS, Firmicutes/ Bacteroidetes ratio is negatively associated with WC (central obesity marker) and positively associated with CRP (inflammatory marker), while lactobacillus was positively correlated with FBS and HOMA, and Bifidobacteria was negatively associated with serum cholesterol and LDL.Conclusion: The two beneficial types the Lactobacillus and bifidobacteria supplementation in form of probiotic with therapeutic treatment and decreasing of WChave their important role in controlling and treating hypertension, serum cholesterol and LDL levels, among obese females even with MetS.

Antioxidant, Anti-Inflammatory, and Immunomodulatory Properties of Tea-The Positive Impact of Tea Consumption on Patients with Autoimmune Diabetes

The physiological markers of autoimmune diabetes include functional disorders of the antioxidative system as well as progressing inflammation and the presence of autoantibodies. Even though people with type 1 diabetes show genetic predispositions facilitating the onset of the disease, it is believed that dietary factors can stimulate the initiation and progression of the disease. This paper analyses the possibility of using tea as an element of diet therapy in the treatment of type 1 diabetes. Based on information available in literature covering the last 10 years, the impact of regular tea consumption or diet supplements containing tea polyphenols on the oxidative status as well as inflammatory and autoimmune response of the organism was analyzed. Studies conducted on laboratory animals, human patients, and in vitro revealed positive effects of the consumption of tea or polyphenols isolated therefrom on the diabetic body. Few reports available in the literature pertain to the impact of tea on organisms affected by type 1 diabetes as most (over 85%) have focused on cases of type 2 diabetes. It has been concluded that by introducing tea into the diet, it is possible to alleviate some of the consequences of oxidative stress and inflammation, thus limiting their destructive impact on the patients' organisms, consequently improving their quality of life, regardless of the type of diabetes. Furthermore, elimination of inflammation should reduce the incidence of immune response. One should consider more widespread promotion of tea consumption by individuals genetically predisposed to diabetes, especially considering the drink's low price, easy availability, overall benefits to human health, and above all, the fact that it can be safely used over extended periods of time, regardless of the patient's age.

Fermentable Oligosaccharides, Disaccharides, Monosaccharides and Polyols (FODMAPs) and cancer risk in the prospective NutriNet-Santé cohort

BACKGROUND

Fermentable Oligosaccharides, Disaccharides and Monosaccharides And Polyols (FODMAPs) have been shown to be involved in gastrointestinal disorders. In view of their pro-inflammatory potential and their interactions with the gut microbiota, their contribution to the etiology of other chronic diseases such as cancer has been postulated. However, no epidemiological study has investigated this hypothesis so far.

OBJECTIVE

Our objective was to investigate the associations between FODMAP intake (total and by type) and cancer risk (overall, breast, prostate and colorectal) in a large prospective cohort.

DESIGN

The study was based on the NutriNet-Santé cohort (2009-2020); 104,909 adult participants without cancer at baseline were included in our analyses (median follow-up time = 7.7y, 78.7% women, mean age at baseline 42.1y (SD = 14.5)). Baseline dietary intakes were obtained from repeated 24h-dietary records linked to a detailed food composition table. Associations between FODMAP intake (expressed in quintiles, Q) and cancer risks were assessed by Cox proportional hazard models adjusted for a large range of lifestyle, sociodemographic and anthropometric variables.

RESULTS

Total FODMAP intake was associated with increased overall cancer risk (n = 3374 incident cases, HR for sex-specific Quintile 5 versus Quintile 1: 1.21; 95%CI: 1.02, 1.44; P-trend = 0.04). In particular, oligosaccharides were associated with cancer risk: a trend was observed for overall cancer (HR Q5 vs. Q1: 1.10; 95%CI: 0.97, 1.25; P-trend = 0.04) and colorectal cancer (n = 272, HR Q5 vs. Q1: 1.78; 95%CI: 1.13-2.79; P-trend = 0.02).

CONCLUSION

Results from this large population-based study on French adults from the NutriNet-Santé cohort show a significant association between FODMAP intake and the risk of cancer development. Further epidemiological and experimental studies are needed to confirm these results and provide data on the potential underlying mechanisms.

Effects of Different Concentrations of Ganpu Tea on Fecal Microbiota and Short Chain Fatty Acids in Mice

Ganpu tea is composed of tangerine peel and Pu-erh tea. Current research suggests that both products can interact with gut microbes and thus affect health. However, as a kind of compound health food, little information is available about the effect of Ganpu tea on intestinal microorganisms. In this study, the basic physiological parameters (body weight, white adipose tissue and serum fat), the regulation of intestinal microorganisms and content of short-chain fatty acids (SCFAs) in feces of healthy mice were studied. The Ganpu tea can reduce the weight gain of mice and the increase in white adipose tissue (p < 0.01). After the intake of Ganpu tea, the abundance of Bacteroidetes increased (p < 0.05), whereas that of Firmicutes decreased (p < 0.01), indicating the latent capacity of Ganpu tea in adjusting the gut microbiota. Moreover, Ganpu tea differentially affected the content of different types of SCFAs in feces. Ganpu tea at the lowest concentrations showed positive effects on the concentrations of SCFAs such as acetic acid and propionic acid, whereas the concentration of butyric acid was decreased. For branched short-chain fatty acids (BSCFAs) such as isobutyric acid, isovaleric acid, etc., Ganpu tea reduced their concentrations. Our results indicated that Ganpu tea may have positive effects on preventing obesity in humans, but further research is needed before introducing such dietary therapy.

Gut Microbiota Composition and Fecal Metabolic Profiling in Patients With Diabetic Retinopathy

Recent evidence suggests there is a link between metabolic diseases and gut microbiota. To investigate the gut microbiota composition and fecal metabolic phenotype in diabetic retinopathy (DR) patients. DNA was extracted from 50 fecal samples (21 individuals with type 2 diabetes mellitus-associated retinopathy (DR), 14 with type 2 diabetes mellitus but without retinopathy (DM) and 15 sex- and age-matched healthy controls) and then sequenced by high-throughput 16S rDNA analysis. Liquid chromatography mass spectrometry (LC-MS)-based metabolomics was simultaneously performed on the samples. A significant difference in the gut microbiota composition was observed between the DR and healthy groups and between the DR and DM groups. At the genus level, Faecalibacterium, Roseburia, Lachnospira and Romboutsia were enriched in DR patients compared to healthy individuals, while Akkermansia was depleted. Compared to those in the DM patient group, five genera, including Prevotella, were enriched, and Bacillus, Veillonella, and Pantoea were depleted in DR patients. Fecal metabolites in DR patients significantly differed from those in the healthy population and DM patients. The levels of carnosine, succinate, nicotinic acid and niacinamide were significantly lower in DR patients than in healthy controls. Compared to those in DM patients, nine metabolites were enriched, and six were depleted in DR patients. KEGG annotation revealed 17 pathways with differentially abundant metabolites between DR patients and healthy controls, and only two pathways with differentially abundant metabolites were identified between DR and DM patients, namely, the arginine-proline and α-linolenic acid metabolic pathways. In a correlation analysis, armillaramide was found to be negatively associated with Prevotella and Subdoligranulum and positively associated with Bacillus. Traumatic acid was negatively correlated with Bacillus. Our study identified differential gut microbiota compositions and characteristic fecal metabolic phenotypes in DR patients compared with those in the healthy population and DM patients. Additionally, the gut microbiota composition and fecal metabolic phenotype were relevant. We speculated that the gut microbiota in DR patients may cause alterations in fecal metabolites, which may contribute to disease progression, providing a new direction for understanding DR.

Intestinal flora alterations in patients with ulcerative colitis and their association with inflammation

Ulcerative colitis (UC), which is a type of inflammatory bowel disease, is a chronic intestinal disorder of multifactorial etiology. Numerous studies have indicated an association between UC and intestinal bacteria. However, a limited number of studies regarding the expression of interleukin-17 (IL-17) and interleukin-23 (IL-23) in association with intestinal bacteria have been performed. The aim of the current study was to investigate the gut microbiota alterations in patients with UC, at a number of taxonomic levels, and their relationship with intestinal inflammation by analyzing the protein expression of IL-17 and IL-23. Specimens were collected from 10 healthy controls and 16 patients with UC. A histological examination was performed in colonic tissues, IL-17 and IL-23 protein expression was detected by immunohistochemistry, fecal samples were sequenced using 16S rDNA sequencing and bioinformatics analysis was performed. The UC group exhibited an increased histological score (P<0.01) and upregulated IL-17 and IL-23 expression (P<0.01). At the order level, the bacterial diversity of the UC group was decreased. β-diversity analyses, including principal component analysis, principal coordinate analysis and non-metric multidimensional scaling, demonstrated that the two groups of samples were separated into two taxonomic categories, as distinct variations were observed in the analysis of group differences (P=0.001). Regarding the differences in species composition between the groups, Enterococcus was indicated to be the species with the greatest difference in abundance compared with the healthy control group (P<0.01), followed by Lactobacillus (P<0.05), Escherichia-Shigella (P<0.05), Bifidobacterium and Bacteroides. In addition, the average optical density of IL-17 was positively correlated with the histological score (ρ=0.669; P=0.035), Enterococcus (r=0.843; P<0.001), Lactobacillus (r=0.737; P=0.001), Bifidobacterium (r=0.773; P<0.001) and Escherichia-Shigella (r=0.663; P=0.005), and the average optical density of IL-23 was positively correlated with the histological score (ρ=0.733; P=0.016), Enterococcus (r=0.771; P<0.001), Lactobacillus (r=0.566; P=0.022), Bifidobacterium (r=0.517; P=0.041) and Escherichia-Shigella (r=0.613; P=0.012). The results of the present study indicated that the intestinal microbiota of patients with UC differed from that of healthy controls at multiple taxonomic levels. The alterations of the intestinal microflora were closely associated with the degree of inflammation. The IL-23/IL-17 axis, as a key factor in the development of UC, maybe associated with the alterations of intestinal microflora. The interaction between intestinal microflora and the IL-23/IL-17 axis may serve an important role in the pathogenesis of UC.

Effects of cadmium on organ function, gut microbiota and its metabolomics profile in adolescent rats

Cadmium (Cd) exposure in adult animals can result in multi-organ damages and gut microbiota disturbance. However, Cd's consequences on health and gut microbiota during adolescence are obscure. In the present study, three-week-old SD rats were exposed to Cd at doses of 0, 0.25, 1, and 4 mg/kg body weight for eight weeks, and the changes of liver, kidney, and ovary function, as well as gut microbiota and its metabolomics profile, were analyzed. After transplantation of fecal bacteria from the 4 mg/kg Cd-treated group into age-matched rats (4 mg/kg-Cd recipients), the organ function and inflammatory reaction were evaluated. The results indicated that Cd perturbed gut microbiota composition, significantly decreased the abundance of Prevotella and Lachnoclostridium but increased Escherichia coli_Shigella. The fecal metabolome profile was altered and was closely correlated with some specific genera. These changes were accompanied by the inflammatory response, dyslipidemia, kidney dysfunction, and abnormal estrogen level. In 4 mg/kg-Cd recipients, the serum triglyceride (TG), lipopolysaccharide (LPS), and inflammatory cytokines were increased with the expressions of IL-1β, IL-6, TNF-α genes up-regulated in liver and kidney. Overall, this study demonstrated that Cd exposure during adolescence could cause disturbance of gut microbiota, dysfunction of liver, kidney, and ovary, which may be correlated with the activation of Cd-induced inflammatory response.

The Role of Carrageenan in Inflammatory Bowel Diseases and Allergic Reactions: Where Do We Stand?

Carrageenan (CGN) is a high molecular weight polysaccharide extracted from red seaweeds, composed of D-galactose residues linked in β-1,4 and α-1,3 galactose-galactose bond, widely used as a food additive in processed foods for its properties as a thickener, gelling agent, emulsifier, and stabilizer. In recent years, with the spread of the Western diet (WD), its consumption has increased. Nonetheless, there is a debate on its safety. CGN is extensively used as an inflammatory and adjuvant agent in vitro and in animal experimental models for the investigation of immune processes or to assess the activity of anti-inflammatory drugs. CGN can activate the innate immune pathways of inflammation, alter the gut microbiota composition and the thickness of the mucus barrier. Clinical evidence suggests that CGN is involved in the pathogenesis and clinical management of inflammatory bowel diseases (IBD), indeed food-exclusion diets can be an effective therapy for disease remission. Moreover, specific IgE to the oligosaccharide α-Gal has been associated with allergic reactions commonly referred to as the "α-Gal syndrome". This review aims to discuss the role of carrageenan in inflammatory bowel diseases and allergic reactions following the current evidence. Furthermore, as no definitive data are available on the safety and the effects of CGN, we suggest gaps to be filled and advise to limit the human exposure to CGN by reducing the consumption of ultra-processed foods.

Assessing the effect of interaction between C-reactive protein and gut microbiome on the risks of anxiety and depression

Cumulative evidence shows that gut microbiome can influence brain function and behavior via the inflammatory processes. However, the role of interaction between gut dysbiosis and C-reactive protein (CRP) in the development of anxiety and depression remains to be elucidated. In this study, a total of 3321 independent single nucleotide polymorphism (SNP) loci associated with gut microbiome were driven from genome-wide association study (GWAS). Using individual level genotype data from UK Biobank, we then calculated the polygenetic risk scoring (PRS) of 114 gut microbiome related traits. Moreover, regression analysis was conducted to evaluate the possible effect of interaction between gut microbiome and CRP on the risks of Patient Health Questionnaire-9 (PHQ-9) (N = 113,693) and Generalized Anxiety Disorder-7 (GAD-7) (N = 114,219). At last, 11 candidate CRP × gut microbiome interaction with suggestive significance was detected for PHQ-9 score, such as F_Ruminococcaceae (β = - 0.009, P = 2.2 × 10^-3), G_Akkermansia (β = - 0.008, P = 7.60 × 10^-3), F_Acidaminococcaceae (β = 0.008, P = 1.22 × 10^-2), G_Holdemanella (β = - 0.007, P = 1.39 × 10^-2) and O_Lactobacillales (β = 0.006, P = 1.79× 10^-2). 16 candidate CRP × gut microbiome interaction with suggestive significance was detected for GAD-7 score, such as O_Bacteroidales (β = 0.010, P = 4.00×  10^-4), O_Selenomonadales (β = - 0.010, P = 1.20 × 10^-3), O_Clostridiales (β = 0.009, P = 2.70 × 10^-3) and G_Holdemanella (β = - 0.008, P = 4.20 × 10^-3). Our results support the significant effect of interaction between CRP and gut microbiome on the risks of anxiety and depression, and identified several candidate gut microbiomes for them.

Potential Benefits of Probiotics and Prebiotics for Coronary Heart Disease and Stroke

Among cardiovascular diseases (CVDs), a major cause of morbidity and mortality worldwide, coronary heart disease and stroke are the most well-known and extensively studied. The onset and progression of CVD is associated with multiple risk factors, among which, gut microbiota has received much attention in the past two decades. Gut microbiota, the microbial community colonizing in the gut, plays a prominent role in human health. In particular, gut dysbiosis is directly related to many acute or chronic dysfunctions of the cardiovascular system (CVS) in the host. Earlier studies have demonstrated that the pathogenesis of CVD is strongly linked to intestinal microbiota imbalance and inflammatory responses. Probiotics and prebiotics conferring various health benefits on the host are emerging as promising therapeutic interventions for many diseases. These two types of food supplements have the potential to alleviate the risks of CVD through improving the levels of several cardiovascular markers, such as total and low-density lipoprotein (LDL) cholesterol, high sensitivity C-reactive protein (hs-CRP), and certain cytokines involved in the inflammatory response. In this review, we focus mainly on the preventive effects of probiotics and prebiotics on CVD via rebalancing the structural and functional changes in gut microbiota and maintaining immune homeostasis.

Nutrition in Patients with Type 2 Diabetes: Present Knowledge and Remaining Challenges

Unhealthy behaviours, including diet and physical activity, coupled with genetic predisposition, drive type 2 diabetes (T2D) occurrence and severity; the present review aims to summarise the most recent nutritional approaches in T2D, outlining unmet needs. Guidelines consistently suggest reducing energy intake to counteract the obesity epidemic, frequently resulting in sarcopenic obesity, a condition associated with poorer metabolic control and cardiovascular disease. Various dietary approaches have been proposed with largely similar results, with a preference for the Mediterranean diet and the best practice being the diet that patients feel confident of maintaining in the long term based on individual preferences. Patient adherence is indeed the pivotal factor for weight loss and long-term maintenance, requiring intensive lifestyle intervention. The consumption of nutritional supplements continues to increase even if international societies do not support their systematic use. Inositols and vitamin D supplementation, as well as micronutrients (zinc, chromium, magnesium) and pre/probiotics, result in modest improvement in insulin sensitivity, but their use is not systematically suggested. To reach the desired goals, patients should be actively involved in the collaborative development of a personalised meal plan associated with habitual physical activity, aiming at normal body weight and metabolic control.

Probiotics, Prebiotics, and Synbiotics in the Irritable Bowel Syndrome Treatment: A Review

Irritable bowel syndrome is not a life-threatening disease, yet it significantly affects the quality of life and contributes to economic loss. It is estimated that even up to 45% of the world's population can suffer from the disease. The first attempts to diagnose irritable bowel syndrome were made at the end of the 19th century; however, establishing appropriate diagnostic criteria and treatment methods is still ongoing. To date, little is known about the etiology of irritable bowel syndrome; however, growing attention is drawn to the intestinal microbiota as a factor in the disease development. For this reason, researchers have conducted many studies on therapies that modulate the microbiota, among which probiotics, prebiotics, and synbiotics are widely studied. To date, most studies have examined probiotics; however, there are also several studies demonstrating the efficacy of prebiotics and synbiotics. The aim of this review was to summarize findings on the usefulness of probiotics, prebiotics, and synbiotics in the treatment of irritable bowel syndrome.

Mediterranean Diet and Physical Activity: Two Imperative Components in Breast Cancer Prevention

Despite tremendous advances in medicine over the past few decades and significantly improved understanding of the symptomology and contributors to breast cancer (BC) incidence, BC rates continue to rise worldwide, with BC being a leading cause of cancer-related death among women. To reduce BC incidence, it is necessary to focus on promoting prevention strategies through a population-based approach of lowering exposure to modifiable risk factors in addition to the application of newer drug interventions (chemoprevention) for prevention in high-risk populations. Currently, available data suggest that lifestyle modifications through a healthy diet and increased physical activity (PA) play a crucial role in BC prevention; specifically, there is growing evidence to indicate that the Mediterranean diet (MeD) lowers cancer risk. This review summarizes the potential role of the MeD and PA in reducing BC risk, with an additional focus on microbial modulation in BC prevention, based on the current evidence obtained from PubMed. After reviewing the immunomodulatory and anticarcinogenic effects of both the MeD and PA, we conclude that further evaluation and proper implementation of both interventions can significantly reduce the risk of BC and associated mortality in the general population.

Effects of ginseng soluble dietary fiber on serum antioxidant status, immune factor levels and cecal health in healthy rats

As an important component of ginseng, the in vivo benefits of ginseng water-soluble dietary fiber (ginseng-SDF) have not been fully revealed. To explore these benefits, healthy rats were given ginseng-SDF (200, 400, and 800 mg/kg body weight/day) by gavage for 15 days. The results showed that ginseng-SDF significantly improved the rats' growth performance and serum antioxidant status. Insulin-like growth factor (IGF-1 and IGF-2) and immunoglobulin (IgA, IgM, and IgG) levels in the ginseng-SDF groups were increased. High-dose ginseng-SDF significantly increased the cecal butyric acid proportion compared with the K group. Ginseng-SDF increased the abundance of Firmicutes and promoted the proliferation of probiotics such as Lactobacillus, and cellulose decomposers such as Ruminococcus and Clostridium in cecal microflora. These altered microflora were correlated with growth performance, antioxidant status and immunoglobulin indexes. The above results suggested that ginseng-SDF might have positive effects on growth, oxidative-immune levels and cecal health in rats.

Gut microbiota in obesity

Obesity is a major global health problem determined by heredity and environment, and its incidence is increasing yearly. In recent years, increasing evidence linking obesity to the gut microbiota has been reported. Gut microbiota management has become a new method of obesity treatment. However, the complex interactions among genetics, environment, the gut microbiota, and obesity remain poorly understood. In this review, we summarize the characteristics of the gut microbiota in obesity, the mechanism of obesity induced by the gut microbiota, and the influence of genetic and environmental factors on the gut microbiota and obesity to provide support for understanding the complex relationship between obesity and microbiota. At the same time, the prospect of obesity research related to the gut microbiota is proposed.

Metformin as a Treatment Strategy for Sjögren's Syndrome

Sjögren's syndrome (SS), a chronic inflammatory disease involving the salivary and lacrimal glands, presents symptoms of sicca as well as systemic manifestations such as fatigue and musculoskeletal pain. Only a few treatments have been successful in management of SS; thus treatment of the disease is challenging. Metformin is the first-line agent for type 2 diabetes and has anti-inflammatory potential. Its immunomodulatory capacity is exerted via activation of 5' adenosine monophosphate-activated protein kinase (AMPK). Metformin inhibits mitochondrial respiratory chain complex I which leads to change in adenosine mono-phosphate (AMP) to adenosine tri-phosphate (ATP) ratio. This results in AMPK activation and causes inhibition of mammalian target of rapamycin (mTOR). mTOR plays an important role in T cell differentiation and mTOR deficient T cells differentiate into regulatory T cells. In this manner, metformin enhances immunoregulatory response in an individual. mTOR is responsible for B cell proliferation and germinal center (GC) differentiation. Thus, reduction of B cell differentiation into antibody-producing plasma cells occurs via downregulation of mTOR. Due to the lack of suggested treatment for SS, metformin has been considered as a treatment strategy and is expected to ameliorate salivary gland function.

Effects of probiotics on body adiposity and cardiovascular risk markers in individuals with overweight and obesity: A systematic review and meta-analysis of randomized controlled trials

BACKGROUND & AIMS

Evidence suggests that gut microbiota is a potential factor in the pathophysiology of both obesity and related metabolic disorders. While individual randomized controlled trials (RCTs) have evaluated the effects of probiotics on adiposity and cardiovascular disease (CVD) risk factors in subjects with overweight and obesity, the results are inconsistent. Thus, this systematic review and meta-analysis aimed to evaluate the effects of probiotic supplementation on body weight, body adiposity and CVD risk markers in overweight and obese subjects.

METHODS

A systematic search for RCTs published up to December 2020 was conducted in MEDLINE (via PubMed), EMBASE, Scopus and LILACS. Meta-analysis using a random-effects model was chosen to analyze the impact of combined trials.

RESULTS

Twenty-six RCTs (n = 1720) were included. Data pooling showed a significant effect of probiotics in reducing body weight (MD:-0.70 kg; 95%CI:-1.04,-0.35 kg; P < 0.0001), body mass index (BMI) (MD:-0.24 kg/m²; 95%CI:-0.35,-0.12 kg/m²; P = 0.0001), waist circumference (WC) (MD:-1.13 cm; 95%CI:-1.54,-0.73 cm; P < 0.0001), fat mass (MD:-0.71 kg; 95%CI:-1.10,-0.32 kg; P = 0.0004), tumor necrosis factor-α (MD:-0.16 pg/ml; 95%CI:-0.24,-0.08 pg/ml; P = 0.0001), insulin (MD:-0.85mcU/ml; 95%CI:-1.50,-0.21mcU/ml; P = 0.010), total cholesterol (MD:-0.16 mmol/l; 95%CI:-0.26,-0.05 mmol/l; P = 0.003) and LDL (MD:-0.09 mmol/l; 95%CI:-0.16,-0.03 mmol/l; P = 0.006) compared with control groups. There was a significant decrease in body weight, BMI and WC in studies using both single and multi-bacterial species. Decreases in body adiposity parameters were only observed in studies using a probiotic dose of ≥ 10¹⁰ CFU and for ≥8 weeks duration.

CONCLUSIONS

The present meta-analysis suggests that probiotics consumption may be helpful for improving body weight, body adiposity and some CVD risk markers in individuals with overweight and obesity. The review was registered on PROSPERO (International prospective register of systematic reviews): CRD42020183136.

Gastrointestinal microbiome, what is behind faecal microbiota transplantation?

The intestinal microbiota is made up of billions of microorganisms that coexist in an organised ecosystem, where strict and facultative anaerobic bacteria predominate. The alteration or imbalance of these microorganisms, known as dysbiosis, can be associated with both gastrointestinal and extraintestinal diseases. Based on a review of the literature, the intestinal microbiota is described in its state of health, the changes associated with some gastrointestinal diseases and the potential role that faecal microbiota transplantation has in the reestablishment of an altered ecosystem. Undoubtedly, the information revealed makes us reflect on the indication of faecal microbiota transplantation in various pathologies of intestinal origin. However, to ensure the efficacy and safety of this therapy, more studies are needed to obtain more evidence.

Biotransformation of Timosaponin BII into Seven Characteristic Metabolites by the Gut Microbiota

Timosaponin BII is one of the most abundant Anemarrhena saponins and is in a phase II clinical trial for the treatment of dementia. However, the pharmacological activity of timosaponin BII does not match its low bioavailability. In this study, we aimed to determine the effects of gut microbiota on timosaponin BII metabolism. We found that intestinal flora had a strong metabolic effect on timosaponin BII by HPLC-MS/MS. At the same time, seven potential metabolites (M1–M7) produced by rat intestinal flora were identified using HPLC/MS-Q-TOF. Among them, three structures identified are reported in gut microbiota for the first time. A comparison of rat liver homogenate and a rat liver microsome incubation system revealed that the metabolic behavior of timosaponin BII was unique to the gut microbiota system. Finally, a quantitative method for the three representative metabolites was established by HPLC-MS/MS, and the temporal relationship among the metabolites was initially clarified. In summary, it is suggested that the metabolic characteristics of gut microbiota may be an important indicator of the pharmacological activity of timosaponin BII, which can be applied to guide its application and clinical use in the future.

Multi-Omics Approaches in Immunological Research

The immune system plays a vital role in health and disease, and is regulated through a complex interactive network of many different immune cells and mediators. To understand the complexity of the immune system, we propose to apply a multi-omics approach in immunological research. This review provides a complete overview of available methodological approaches for the different omics data layers relevant for immunological research, including genetics, epigenetics, transcriptomics, proteomics, metabolomics, and cellomics. Thereafter, we describe the various methods for data analysis as well as how to integrate different layers of omics data. Finally, we discuss the possible applications of multi-omics studies and opportunities they provide for understanding the complex regulatory networks as well as immune variation in various immune-related diseases.

Nutritional and ecological perspectives of the interrelationships between diet and the gut microbiome in multiple sclerosis: Insights from marmosets

Studies in experimental autoimmune encephalomyelitis (EAE), the animal model of multiple sclerosis, have shown potential links between diet components, microbiome composition, and modulation of immune responses. In this review, we reanalyze and discuss findings in an outbred marmoset EAE model in which a yogurt-based dietary supplement decreased disease frequency and severity. We show that although diet has detectable effects on the fecal microbiome, microbiome changes are more strongly associated with the EAE development. Using an ecological framework, we further show that the dominant factors influencing the gut microbiota were marmoset sibling pair and experimental time point. These findings emphasize challenges in assigning cause-and-effect relationships in studies of diet-microbiome-host interactions and differentiating the diet effects from other environmental, stochastic, and host-related factors. We advocate for animal experiments to be designed to allow causal inferences of the microbiota's role in pathology while considering the complex ecological processes that shape microbial communities.

Human gut-microbiome interplay: Analysis of clinical studies for the emerging roles of diagnostic microbiology in inflammation, oncogenesis and cancer management

Microorganisms have been known to coexist in various parts of human body including the gut. The interactions between microbes and the surrounding tissues of the host are critical for fine fettle of the gut. The incidence of such microorganisms tends to vary among specific type of cancer affected individuals. Such microbial communities of specific tumor sites in cancer affected individuals could plausibly be used as prognostic and/or diagnostic markers for tumors associated with that specific site. Microorganisms of intestinal and non-intestinal origins including Helicobacter pylori can target several organs, act as carcinogens and promote cancer. It is interesting to note that diets causing inflammation can also increase the cancer risk. Yet, dietary supplementation with prebiotics and probiotics can reduce the incidence of cancer. Therefore, both diet and microbial community of the gut have dual roles of prevention and oncogenesis. Hence, this review intends to summarize certain important details related to gut microbiome and cancer.

Patient factors related to early implant failures in the edentulous jaw: A large retrospective case-control study

BACKGROUND

Dental implants provide anchorage for dental prostheses to restore functions for individuals with edentulous jaws. During the healing phase, proper osseointegration is required to prevent early implant failure. More knowledge is needed regarding factors related to early failure of dental implants.

PURPOSE

The aim of the present study was to identify possible risk factors for early implant failure, with respect to anamnestic and clinical parameters.

MATERIALS AND METHODS

All patients with edentulous jaws with early implant failure (n = 408) from one referral clinic were compared with a matched control group (n = 408) with no implant failure. Early implant failure was identified during the first year of prosthetic function. Matching was performed on age, gender, year of surgery, type of jaw, and type of implant surface. In addition, data on anamnestic and clinical parameters were collected. The data were analyzed with a multivariable logistic regression model using early implant failure as the binary outcome.

RESULTS

Five anamnestic factors were statistically significant with respect to higher probability for early implant failure: systemic disease, allergies in general, food allergies, smoking, and intake of analgesic medication. Four clinical conditions (i.e., implants in the opposing jaw, low primary stability, reduced bone volume, and healing complications) were also related to higher probability for early implant failure.

CONCLUSIONS

This study identified nine factors associated with early implant failure, several related to patient's general health. Further investigations are needed to fully understand the causality between the obtained variables and early implant failure.

Gut Microbiota and Acute Diverticulitis: Role of Probiotics in Management of This Delicate Pathophysiological Balance

How can the knowledge of probiotics and their mechanisms of action be translated into clinical practice when treating patients with diverticular disease and acute diverticulitis? Changes in microbiota composition have been observed in patients who were developing acute diverticulitis, with a reduction of taxa with anti-inflammatory activity, such as Clostridium cluster IV, Lactobacilli and Bacteroides. Recent observations supported that a dysbiosis characterised by decreased presence of anti-inflammatory bacterial species might be linked to mucosal inflammation, and a vicious cycle results from a mucosal inflammation driving dysbiosis at the same time. An alteration in gut microbiota can lead to an altered activation of nerve fibres, and subsequent neuronal and muscular dysfunction, thus favoring abdominal symptoms' development. The possible role of dysbiosis and mucosal inflammation in leading to dysmotility is linked, in turn, to bacterial translocation from the lumen of the diverticulum to perivisceral area. There, a possible activation of Toll-like receptors has been described, with a subsequent inflammatory reaction at the level of the perivisceral tissues. Being aware that bacterial colonisation of diverticula is involved in the pathogenesis of acute diverticulitis, the rationale for the potential role of probiotics in the treatment of this disease becomes clearer. For this review, articles were identified using the electronic PubMed database through a comprehensive search conducted by combining key terms such as "gut microbiota", "probiotics and gut disease", "probiotics and acute diverticulitis", "probiotics and diverticular disease", "probiotics mechanism of action". However, the amount of data present on this matter is not sufficient to draw robust conclusions on the efficacy of probiotics for symptoms' management in diverticular disease.

The association of child maltreatment and systemic inflammation in adulthood: A systematic review

Introduction

Child maltreatment (CM) is associated with mental and physical health disorders in adulthood. Some studies have identified elevated markers of systemic inflammation in adult survivors of CM, and inflammation may mediate the association between CM and later health problems. However, there are methodological inconsistencies in studies of the association between CM and systemic inflammation and findings are conflicting. We performed a systematic review to examine the association of CM with systemic inflammation in adults.

Methods

A pre-registered systematic review was performed following PRISMA guidelines. Medline, Embase, Scopus and PsychInfo were searched for studies of the association of CM with blood markers of inflammation in adults. Quality was assessed using the Crowe Critical Appraisal Tool. We had intended to perform a meta-analysis, but this was not possible due to variation in study design and reporting.

Results

Forty-four articles met criteria for inclusion in the review. The most widely reported biomarkers were C-Reactive Protein (CRP) (n = 27), interleukin-6 (IL-6) (n = 24) and Tumour Necrosis Factor-alpha (TNF-a) (n = 17). Three studies were prospective (all relating to CRP) and the remainder were retrospective. 86% of studies were based in high income countries. In the prospective studies, CM was associated with elevated CRP in adulthood. Results of retrospective studies were conflicting. Methodological issues relating to the construct of CM, methods of analysis, and accounting for confounding or mediating variables (particularly Body Mass Index) may contribute to the uncertainty in the field.

Conclusions

There is some robust evidence from prospective studies that CM is associated with elevated CRP in adulthood. We have identified significant methodological inconsistencies in the literature and have proposed measures that future researchers could employ to improve consistency across studies. Further prospective, longitudinal, research using robust and comparable measures of CM with careful consideration of confounding and mediating variables is required to bring clarity to this field.

Regulation of Enteric Infection and Immunity by Dietary Proanthocyanidins

The role of dietary components in immune function has acquired considerable attention in recent years. An important focus area is to unravel the role of bioactive dietary compounds in relation to enteric disease and their impact on gut mucosal immunity. Proanthocyanidins (PAC) are among the most common and most consumed dietary polyphenols, and are characterised by their variable molecular structures and diverse bioactivities. In particular, their anti-oxidative effects and ability to modulate gut microbiota have been widely described. However, there is limited evidence on the mechanism of action of PAC on the immune system, nor is it clearly established how PAC may influence susceptibility to enteric infections. Establishing the sites of action of PAC and their metabolites within the gut environment is fundamental to determine the applicability of PAC against enteric pathogens. Some mechanistic studies have shown that PAC have direct modulatory effects on immune cell signalling, isolated pathogens, and gut mucosal barrier integrity. Boosting the recruitment of immune cells and suppressing the amount of pro-inflammatory cytokines are modulating factors regulated by PAC, and can either be beneficial or detrimental in the course of re-establishing gut homeostasis. Herein, we review how PAC may alter distinct immune responses towards enteric bacterial, viral and parasitic infections, and how the modulation of gut microbiota may act as a mediating factor. Furthermore, we discuss how future studies could help unravel the role of PAC in preventing and/or alleviating intestinal inflammation and dysbiosis caused by enteric disease.

Crosstalk between gut microbiome and immunology in the management of ischemic brain injury

Ischemic brain injury is a serious neurological complication, which accrues an immense activation of neuroinflammatory responses. Several lines of research suggested the interconnection of gut microbiota perturbation with the activation of proinflammatory mediators. Intestinal microbial communities also interchange information with the brain through various afferent and efferent channels and microbial by-products. Herein, we discuss the different microelements of gut microbiota and its connection with the host immune system and how change in immune-microbial signatures correlates with the stroke incidence and post-injury neurological sequelae. The activated inflammatory cells increase the production of proinflammatory cytokines, chemokines, proteases and adhesive proteins that are involved in the systemic inflammation, blood brain barrier disruption, gut dysbiosis and aggravation of ischemic brain injury. We suggest that fine-tuning of commensal gut microbiota (eubiosis) may regulate the activation of CNS resident cells like microglial, astrocytes, mast cells and natural killer cells.

The Immunopathogenesis of Alzheimer's Disease Is Related to the Composition of Gut Microbiota

The microbiota-gut-brain axis plays an important role in the development of neurodegenerative diseases. Commensal and pathogenic enteric bacteria can influence brain and immune system function by the production of lipopolysaccharides and amyloid. Dysbiosis of the intestinal microbiome induces local and consecutively systemic immune-mediated inflammation. Proinflammatory cytokines then trigger neuroinflammation and finally neurodegeneration. Immune-mediated oxidative stress can lead to a deficiency of vitamins and essential micronutrients. Furthermore, the wrong composition of gut microbiota might impair the intake and metabolization of nutrients. In patients with Alzheimer's disease (AD) significant alterations of the gut microbiota have been demonstrated. Standard Western diet, infections, decreased physical activity and chronic stress impact the composition and diversity of gut microbiota. A higher abundancy of "pro-inflammatory" gut microbiota goes along with enhanced systemic inflammation and neuroinflammatory processes. Thus, AD beginning in the gut is closely related to the imbalance of gut microbiota. Modulation of gut microbiota by Mediterranean diet, probiotics and curcumin can slow down cognitive decline and alter the gut microbiome significantly. A multi-domain intervention approach addressing underlying causes of AD (inflammation, infections, metabolic alterations like insulin resistance and nutrient deficiency, stress) appears very promising to reduce or even reverse cognitive decline by exerting positive effects on the gut microbiota.