Gut commensal Bacteroides acidifaciens prevents obesity and improves insulin sensitivity in mice

Understanding Bile Acid Signaling in Diabetes: From Pathophysiology to Therapeutic Targets

Diabetes and obesity have reached an epidemic status worldwide. Diabetes increases the risk for cardiovascular disease and non-alcoholic fatty liver disease. Primary bile acids are synthesized in hepatocytes and are transformed to secondary bile acids in the intestine by gut bacteria. Bile acids are nutrient sensors and metabolic integrators that regulate lipid, glucose, and energy homeostasis by activating nuclear farnesoid X receptor and membrane Takeda G protein-coupled receptor 5. Bile acids control gut bacteria overgrowth, species population, and protect the integrity of the intestinal barrier. Gut bacteria, in turn, control circulating bile acid composition and pool size. Dysregulation of bile acid homeostasis and dysbiosis causes diabetes and obesity. Targeting bile acid signaling and the gut microbiome have therapeutic potential for treating diabetes, obesity, and non-alcoholic fatty liver disease.

Destiny of Dendrobium officinale Polysaccharide after Oral Administration: Indigestible and Nonabsorbing, Ends in Modulating Gut Microbiota

Polysaccharides from functional foods have been proved to have diverse bioactivities, but little is known about what exactly happens to these polysaccharides after oral administration and even less about the underlying mechanism of action. Taking the marker polysaccharide (DOP) of Dendrobium officinale as an example, this study aims to demonstrate the dynamic distribution and degradation of orally dosed DOP in mice and in vitro using near-infrared fluorescence imaging and a kind of chromatographic analysis. The results indicate that (1) neither DOP nor fluorescence-labeled DOP (FDOP) was absorbed, (2) both DOP and FDOP were undigested and were quickly degraded to short-chain fatty acids in the large intestine, (3) DOP modulated gut microbiota, which could be associated with DOP's suppression of 4T1 tumor growth in mice. All of these findings suggest that some (maybe not all) bioactive polysaccharides share a common destiny: indigestible and nonabsorbing, ends in modulating bioactivities-associated gut microbiota.

Impact of Gut Microbiota Composition on Onset and Progression of Chronic Non-Communicable Diseases

In recent years, mounting scientific evidence has emerged regarding the evaluation of the putative correlation between the gut microbiota composition and the presence of chronic non-communicable diseases (NCDs), such as diabetes mellitus, chronic kidney disease, and arterial hypertension. The aim of this narrative review is to examine the current literature with respect to the relationship between intestinal dysbiosis and the insurgence/progression of chronic NCDs, analyzing the physiopathological mechanisms that can induce microbiota modification in the course of these pathologies, and the possible effect induced by microbiota alteration upon disease onset. Therapy based on probiotics, prebiotics, synbiotics, postbiotics, and fecal microbiota transplant can represent a useful therapeutic tool, as has been highlighted on animal studies. To this moment, clinical studies that intended to demonstrate the beneficial effect induced by this kind of oral supplementation on the gut microbiota composition, and subsequent amelioration of signs and symptoms of chronic NCDs have been conducted on limited sample populations for a limited follow-up period. Therefore, to fully evaluate the therapeutic value of this kind of intervention, it would be ideal to design ample population; randomized clinical trials with a lengthy follow up period.

Bile Acids as Metabolic Regulators and Nutrient Sensors

Bile acids facilitate nutrient absorption and are endogenous ligands for nuclear receptors that regulate lipid and energy metabolism. The brain-gut-liver axis plays an essential role in maintaining overall glucose, bile acid, and immune homeostasis. Fasting and feeding transitions alter nutrient content in the gut, which influences bile acid composition and pool size. In turn, bile acid signaling controls lipid and glucose use and protection against inflammation. Altered bile acid metabolism resulting from gene mutations, high-fat diets, alcohol, or circadian disruption can contribute to cholestatic and inflammatory diseases, diabetes, and obesity. Bile acids and their derivatives are valuable therapeutic agents for treating these inflammatory metabolic diseases.

Magnesium lithospermate B improves the gut microbiome and bile acid metabolic profiles in a mouse model of diabetic nephropathy

Magnesium lithospermate B (MLB) is a new drug marketed in China to treat angina, but its low oral bioavailability limits its clinical application to the intravenous route. Paradoxically, orally administered low-dose MLB was found to alleviate kidney injury in diabetic nephropathy (DN) rats, but its mechanism of action remains unknown. In recent years, the kidney-gut axis has been suspected to be involved in kidney damage pathogenesis, potentially representing a non-classical pathway for pharmacologic intervention. To ascertain whether MLB targets the kidney-gut axis, streptozotocin (STZ)-treated mice were prepared as a mouse model of DN. The STZ mice were treated with MLB (50 mg kg-1 d-1, p.o.) for 8 weeks. Twenty-four-hour urinary albumin was detected to mirror kidney function. At week 4, 6, 8, feces were collected; bile acids (BAs) were quantified to examine the alterations in the BA metabolic profiles, and bacterial 16S rRNA gene fragments were sequenced to identify alterations in gut microbial composition. In STZ mice, 24-h urinary albumin levels and total fecal BAs, especially cholic acids (CAs) and deoxycholic acids (DCAs) were greatly increased, and the gut microbiome was dramatically shifted compared with control mice. Oral administration of MLB significantly decreased 24-h urinary albumin levels and total BAs, CAs and DCAs, and reversed CA:TCA (taurocholic acid) and DCA:CA ratios. It also changed the microbiome composition in STZ mice based on operational units. Thus the therapeutic effect of MLB on kidney injury might be attributed (at least partially) to its ability to modulate the disordered gut microbiome and BA metabolism.

Impact of the gut microbiome on the genome and epigenome of colon epithelial cells: contributions to colorectal cancer development

In recent years, the number of studies investigating the impact of the gut microbiome in colorectal cancer (CRC) has risen sharply. As a result, we now know that various microbes (and microbial communities) are found more frequently in the stool and mucosa of individuals with CRC than healthy controls, including in the primary tumors themselves, and even in distant metastases. We also know that these microbes induce tumors in various mouse models, but we know little about how they impact colon epithelial cells (CECs) directly, or about how these interactions might lead to modifications at the genetic and epigenetic levels that trigger and propagate tumor growth. Rates of CRC are increasing in younger individuals, and CRC remains the second most frequent cause of cancer-related deaths globally. Hence, a more in-depth understanding of the role that gut microbes play in CRC is needed. Here, we review recent advances in understanding the impact of gut microbes on the genome and epigenome of CECs, as it relates to CRC. Overall, numerous studies in the past few years have definitively shown that gut microbes exert distinct impacts on DNA damage, DNA methylation, chromatin structure and non-coding RNA expression in CECs. Some of the genes and pathways that are altered by gut microbes relate to CRC development, particularly those involved in cell proliferation and WNT signaling. We need to implement more standardized analysis strategies, collate data from multiple studies, and utilize CRC mouse models to better assess these effects, understand their functional relevance, and leverage this information to improve patient care.

Association between blood microbiome and type 2 diabetes mellitus: A nested case-control study

Background

Although recent studies have indicated that gut microbiome dysbiosis was significantly associated with the onset of type 2 diabetes mellitus (T2DM), information on the role of blood microbiome in T2DM development is scarce.

Methods

Fifty incident T2DM cases and 100 matched non‐T2DM controls were selected from a prospective cohort study of “135.” The composition of the blood microbiome was characterized using bacterial 16S ribosomal RNA (16S rRNA) gene sequencing from pre‐diagnostic blood sample. The amplicons were normalized, pooled, and sequenced on the Illumina MiSeq instrument using a MiSeq Reagent Kit PE300 v3 kit.

Results

Totally, 3 000 391 and 6 244 227 high‐quality sequences were obtained from T2DM patients and non‐T2DM controls, respectively. The mean diversity of the blood microbiome (Simpson, Chao1 and Shannon indices) was not different between two groups at baseline. At genus level, the Aquabacterium, Xanthomonas, and Pseudonocardia were presented with lower abundance, while Actinotalea, Alishewanella, Sediminibacterium, and Pseudoclavibacter were presented with higher abundance among T2DM cases compared to those in non‐T2DM controls. As the results shown, participants carried the genus Bacteroides in blood were significantly associated with a decreased risk for T2DM development, with 74% vs 88% (adjusted OR: 0.367, 95% CI: 0.151‐0.894). However, participants carried the genus Sediminibacterium have an increased risk for T2DM, with adjusted OR (95% CI) being 14.098 (1.358, 146.330).

Conclusions

Blood microbiome may play an etiology role in the development of T2DM. These findings would be useful to develop microbiota‐based strategies for T2DM prevention and control.

The Effects of Glucosamine and Chondroitin Sulfate on Gut Microbial Composition: A Systematic Review of Evidence from Animal and Human Studies

Oral glucosamine sulfate (GS) and chondroitin sulfate (CS), while widely marketed as joint-protective supplements, have limited intestinal absorption and are predominantly utilized by gut microbiota. Hence the effects of these supplements on the gut microbiome are of great interest, and may clarify their mode of action, or explain heterogeneity in therapeutic responses. We conducted a systematic review of animal and human studies reporting the effects of GS or CS on gut microbial composition. We searched MEDLINE, EMBASE, and Scopus databases for journal articles in English from database inception until July 2018, using search terms microbiome, microflora, intestinal microbiota/flora, gut microbiota/flora and glucosamine or chondroitin. Eight original articles reported the effects of GS or CS on microbiome composition in adult humans (four articles) or animals (four articles). Studies varied significantly in design, supplementation protocols, and microbiome assessment methods. There was moderate-quality evidence for an association between CS exposure and increased abundance of genus Bacteroides in the murine and human gut, and low-quality evidence for an association between CS exposure and an increase in Desulfovibrio piger species, an increase in Bacteroidales S24-7 family, and a decrease in Lactobacillus. We discuss the possible metabolic implications of these changes for the host. For GS, evidence of effects on gut microbiome was limited to one low-quality study. This review highlights the importance of considering the potential influence of oral CS supplements on gut microbiota when evaluating their effects and safety for the host.

Influence of Maternal Inulin-Type Prebiotic Intervention on Glucose Metabolism and Gut Microbiota in the Offspring of C57BL Mice

Scope: Maternal obesity leads to glucose intolerance in the offspring. Changes in the gut microbiota are being increasingly implicated in the pathogenesis of diabetes. We hypothesized that inulin intervention during gestation and lactation improves glucose metabolism disorders in mouse offspring from high-fat diet (HD)-fed dams. Procedures: Female C57BL mice were fed a control diet or HD for 4 weeks before mating. After mating, pregnant mice were randomly divided into three groups through gestation and lactation: control diet (CD) group, HD group, and HD treated with inulin (HD-inulin) group. At weaning, glucose metabolic status was assessed. Gut microbial DNA from offspring cecal contents was isolated and processed for metagenomic shotgun sequencing, and taxonomic and functional profiling were performed. Results: Offspring from dams in the HD-inulin groups demonstrated reduced fasting blood glucose, decreased blood glucose area under the curve during the oral glucose tolerance test, and reduced fasting serum insulin and HOMA-IR compared to offspring from dams in the HD group. Nineteen differentially abundant bacterial species were identified between the HD-inulin and HD groups. The HD-inulin group displayed significantly greater abundances of Bacteroides_acidifaciens, Eubacterium_sp_CAG_786, Clostridium_sp_CAG_343, and Bifidobacterium_breve species and lower abundances of Oscillibacter_sp_1_3, Ruminococcus_gnavus_CAG_126, and Bacteroides_massiliensis species. Differentially abundant bacterial species among the three groups were involved in 38 metabolic pathways, including several glucose and lipid metabolism pathways. Conclusion: Our results show that early inulin intervention in HD-fed mouse dams moderates offspring glucose metabolism and gut dysbiosis.

Mannan-oligosaccharide modulates the obesity and gut microbiota in high-fat diet-fed mice

The gut microbiota is considered to be associated with high-fat diet (HFD)-induced obesity and metabolic syndrome (MS). Mannan-oligosaccharide (MOS) is widely used as a natural additive, and its effect on promoting fat metabolism has been reported. Here, we performed a 11-week study on C57BL/6J mice fed a high-fat diet (HFD) with/without MOS supplementation, and the results showed that MOS could attenuate high-fat diet induced metabolic syndrome, including slower body weight gain, lowered serum lipids and reduced insulin resistance. Next generation sequencing (NGS) of the gut microbiota indicated that MOS modulated the overall structure of the gut microbiome, which was highly correlated with MS parameters. Specifically, the intake of MOS decreased the Firmicutes/Bacteroidetes ratio and could reverse the changes in the relative abundance of several species caused by HFD, including Akkermansia muciniphila, Bacteroides acidifaciens, Lactobacillus gasseri and Bifidobacterium pseudolongum. Thus, MOS has the potential to be used as a new prebiotic for regulating the gut microbiota and helping in attenuating metabolic disorders.

The gut microbiome of Mexican children affected by obesity

Obesity is a metabolic disorder and global health issue. In Mexico 34.4% of children between 5 and 11 years-old are overweight or obese. Here we address this issue studying the gut microbiome in a sample of Mexican children affected by obesity. We performed metagenomic shotgun-sequencing of DNA isolated from fecal samples from a cohort of normal weight and obese Mexican children using Illumina platform with HiSeq 2500. We also examined their metabolic factors and fecal short-chain fatty acids concentration. The results show that a remarkable dysbiosis of bacteria, archaea and viruses was not observed in the obese children group compared to the normal weight group; however, the archaeal community exhibited an increase of unclassified Methanobrevibacter spp. in obese children. The bacterial communities of all participants were clustered into three different enterotypes. Most normal weight children have a gut bacterial community dominated by Ruminococcus spp. (Enterotype 3), while most obese children had a community dominated by Prevotella spp. (Enterotype 2). On the other hand, changes in the gut microbiome were correlated with clinical metadata and could be used to stratify individuals based on their phenotype. The species Megamonas spp. were over-represented in obese children, whereas members of the family Oscillospiraceae were depleted in the same individuals and negatively correlated with levels of serum cholesterol. A microbiome comparative metabolic pathway analysis showed that two KEGG pathway modules of glycolysis, Glycolysis I (from Glucose 6-Phosphate), and Glycolysis II (from Fructose 6-Phosphate) were significantly overrepresented in normal weight children. Our results establish specific alterations in the gut microbiome of Mexican children affected of obesity, along with clinical alterations, providing information on the microbiome composition that may be useful for prognosis, diagnosis, and treatment.

Dietary Exposure to the Environmental Chemical, PFOS on the Diversity of Gut Microbiota, Associated With the Development of Metabolic Syndrome

The gut microbiome is a dynamic ecosystem formed by thousands of diverse bacterial species. This bacterial diversity is acquired early in life and shaped over time by a combination of multiple factors, including dietary exposure to distinct nutrients and xenobiotics. Alterations of the gut microbiota composition and associated metabolic activities in the gut are linked to various immune and metabolic diseases. The microbiota could potentially interact with xenobiotics in the gut environment as a result of their board enzymatic capacities and thereby affect the bioavailability and toxicity of the xenobiotics in enterohepatic circulation. Consequently, microbiome-xenobiotic interactions might affect host health. Here, we aimed to investigate the effects of dietary perfluorooctane sulfonic acid (PFOS) exposure on gut microbiota in adult mice and examine the induced changes in animal metabolic functions. In mice exposed to dietary PFOS for 7 weeks, body PFOS and lipid contents were measured, and to elucidate the effects of PFOS exposure, the metabolic functions of the animals were assessed using oral glucose-tolerance test and intraperitoneal insulin-tolerance and pyruvate-tolerance tests; moreover, on Day 50, cecal bacterial DNA was isolated and subject to 16S rDNA sequencing. Our results demonstrated that PFOS exposure caused metabolic disturbances in the animals, particularly in lipid and glucose metabolism, but did not substantially affect the diversity of gut bacterial species. However, marked modulations were detected in the abundance of metabolism-associated bacteria belonging to the phyla Firmicutes, Bacteroidetes, Proteobacteria, and Cyanobacteria, including, at different taxonomic levels, Turicibacteraceae, Turicibacterales, Turicibacter, Dehalobacteriaceae, Dehalobacterium, Allobaculum, Bacteroides acidifaciens, Alphaproteobacteria, and 4Cod-2/YS2. The results of PICRUSt analysis further indicated that PFOS exposure perturbed gut metabolism, inducing notable changes in the metabolism of amino acids (arginine, proline, lysine), methane, and a short-chain fatty acid (butanoate), all of which are metabolites widely recognized to be associated with inflammation and metabolic functions. Collectively, our study findings provide key information regarding the biological relevance of microbiome-xenobiotic interactions associated with the ecology of gut microbiota and animal energy metabolism.

Oleoylethanolamide treatment affects gut microbiota composition and the expression of intestinal cytokines in Peyer's patches of mice

The lipid sensor oleoylethanolamide (OEA), an endogenous high-affinity agonist of peroxisome proliferator-activated receptor-α (PPAR-α) secreted in the proximal intestine, is endowed with several distinctive homeostatic properties, such as control of appetite, anti-inflammatory activity, stimulation of lipolysis and fatty acid oxidation. When administered exogenously, OEA has beneficial effects in several cognitive paradigms; therefore, in all respects, OEA can be considered a hormone of the gut-brain axis. Here we report an unexplored modulatory effect of OEA on the intestinal microbiota and on immune response. Our study shows for the first time that sub-chronic OEA administration to mice fed a normal chow pellet diet, changes the faecal microbiota profile, shifting the Firmicutes:Bacteroidetes ratio in favour of Bacteroidetes (in particular Bacteroides genus) and decreasing Firmicutes (Lactobacillus), and reduces intestinal cytokines expression by immune cells isolated from Peyer's patches. Our results suggest that sub-chronic OEA treatment modulates gut microbiota composition towards a "lean-like phenotype", and polarises gut-specific immune responses mimicking the effect of a diet low in fat and high in polysaccharides content.

Intestine farnesoid X receptor agonist and the gut microbiota activate G-protein bile acid receptor-1 signaling to improve metabolism

Bile acids activate farnesoid X receptor (FXR) and G protein-coupled bile acid receptor-1 (aka Takeda G protein-coupled receptor-5 [TGR5]) to regulate bile acid metabolism and glucose and insulin sensitivity. FXR and TGR5 are coexpressed in the enteroendocrine L cells, but their roles in integrated regulation of metabolism are not completely understood. We reported recently that activation of FXR induces TGR5 to stimulate glucagon-like peptide-1 (GLP-1) secretion to improve insulin sensitivity and hepatic metabolism. In this study, we used the intestine-restricted FXR agonist fexaramine (FEX) to study the effect of activation of intestinal FXR on the gut microbiome, bile acid metabolism, and FXR and TGR5 signaling. The current study revealed that FEX markedly increased taurolithocholic acid, increased secretion of fibroblast growth factors 15 and 21 and GLP-1, improved insulin and glucose tolerance, and promoted white adipose tissue browning in mice. Analysis of 16S ribosomal RNA sequences of the gut microbiome identified the FEX-induced and lithocholic acid-producing bacteria Acetatifactor and Bacteroides. Antibiotic treatment completely reversed the FEX-induced metabolic phenotypes and inhibited taurolithocholic acid synthesis, adipose tissue browning, and liver bile acid synthesis gene expression but further increased intestinal FXR target gene expression. FEX treatment effectively improved lipid profiles, increased GLP-1 secretion, improved glucose and insulin tolerance, and promoted adipose tissue browning, while antibiotic treatment reversed the beneficial metabolic effects of FEX in obese and diabetic mice.

CONCLUSION

This study uncovered a mechanism in which activation of intestinal FXR shaped the gut microbiota to activate TGR5/GLP-1 signaling to improve hepatic glucose and insulin sensitivity and increase adipose tissue browning; the gut microbiota plays a critical role in bile acid metabolism and signaling to regulate metabolic homeostasis in health and disease. (Hepatology 2018).

Intestinal fluke Metagonimus yokogawai infection increases probiotic Lactobacillus in mouse cecum

Helminth infection can alleviate immune-mediated disorders such as allergies and autoimmune diseases, by altering the gut microbiome. However, changes in gut microbiome due to intestinal trematodes remain unelucidated. Here, we evaluated the changes in the gut microbiome of ICR mice infected with Metagonimus yokogawai, a hypo-virulent intestinal trematode. Four weeks after infection, mouse cecal content was analyzed by 16S rRNA amplicon analysis. Although there was no apparent difference in species richness and diversity, the microbiome composition was different in the infected and control groups. Furthermore, several Lactobacillus species with known immunomodulatory role in immune-mediated diseases were increased in the infected group.

Agaro-Oligosaccharides Regulate Gut Microbiota and Adipose Tissue Accumulation in Mice

Gut microbiota are deeply associated with the prevalence of obesity. Agarose is hydrolyzed easily to yield oligosaccharides, designated as agaro-oligosaccharides (AGO). This study evaluated the effects of AGO on obese phenotype and gut microbial composition in mice. Mice were administered AGO in drinking water (AGO-receiving mice). 16S rRNA gene sequencing analyses revealed their fecal microbiota profiles. Serum bile acids were ascertained using a LC-MS/MS system. Compared to the control group, AGO administration significantly reduced epididymal adipose tissue weights and serum non-esterified fatty acid concentrations, but the cecal content weights were increased. Data from the serum bile acid profile show that concentrations of primary bile acids (cholic acid and chenodeoxycholic acid), but not those of secondary bile acids (deoxycholic acid, lithocholic acid, and ursodeoxycholic acid), tended to increase in AGO-receiving mice. 16S rRNA gene sequencing analyses showed that the relative abundances of 15 taxa differed significantly in AGO-receiving mice. Of these, the relative abundances of Rikenellaceae and Lachnospiraceae were found to be positively correlated with epididymal adipose tissue weight. The relative abundances of Bacteroides and Ruminococcus were correlated negatively with epididymal adipose tissue weight. Although the definitive role of gut microbes of AGO-received mice is still unknown, our data demonstrate the possibility that AGO administration affects the gut microbial composition and inhibits obesity in mice.

Prebiotic Mannan-Oligosaccharides Augment the Hypoglycemic Effects of Metformin in Correlation with Modulating Gut Microbiota

Type 2 diabetes (T2D) induced by obesity and high-fat diet is significantly associated with gut microbiota dysbacteriosis. Because the first line clinical medicine of metformin has several intestinal drawbacks, combination usage of metformin with a prebiotic of konjac mannan-oligosaccharides (MOS) was conceived and implemented aiming to investigate whether there were some intestinal synergetic effects and how MOS would function. Composite treatment of metformin and MOS demonstrated synergistic effects on ameliorating insulin resistance and glucose tolerance, also on repairing islet and hepatic histology. In addition, MF+MOS altered the gut community composition and structure by decreasing the relative abundances of family Rikenellaceae and order Clostridiales while increasing an unnamed OTU05945 of family S24-7, Akkermansia muciniphila, and Bifidobacterium pseudolongum. The present study suggested that usage of MOS could augment the hypoglycemic effects of metformin in association with gut microbiota modulation, which could provide references for further medication.

Antimicrobial Emulsifier-Glycerol Monolaurate Induces Metabolic Syndrome, Gut Microbiota Dysbiosis, and Systemic Low-Grade Inflammation in Low-Fat Diet Fed Mice

SCOPE

Glycerol monolaurate (GML) is widely consumed worldwide in the food industry and is considered safe, but for chronic diseases, supporting scientific data remain sparse. This study investigates whether dietary GML induces metabolic syndrome, gut microbiota dysbiosis, and systemic low-grade inflammation.

METHODS AND RESULTS

GML-induced occurrence of metabolic syndrome, gut microbiota alterations, and systemic low-grade inflammation are investigated. The results demonstrate that GML induced metabolic syndrome by significantly increasing the body weight, weight gain, food intake, body fat, fat droplet size and percentage of epididymal fat, serum triglycerides (TG), LDL, and atherogenic index, and decreasing the body muscle ratio, liver weight, and HDL, compared to the control (CON) group. Meanwhile, GML significantly changed the β-diversity and composition of gut microbiota and upregulated the circulating levels of serum LPS, IL-1β, IL-6, and TNF-α. Importantly, GML significantly decreased Akkermansia muciniphila and Lupinus luteus, and increased Bacteroides acidifaciens, Escherichia coli and the microbial DNA abundance of the ten predicated metabolism pathways involved in carbohydrate, amino acid, and lipid metabolism.

CONCLUSION

Our results indicate that relatively low-dose GML consumption promotes metabolic syndrome, gut microbiota dysbiosis, and systemic low-grade inflammation, thereby calling for a reassessment of GML usage.

Berberine treatment increases Akkermansia in the gut and improves high-fat diet-induced atherosclerosis in Apoe-/- mice

BACKGROUND AND AIMS

Gut microbiota plays a major role in metabolic disorders. Berberine is used to treat obesity, diabetes and atherosclerosis. The mechanism underlying the role of berberine in modulating metabolic disorders is not fully clear because berberine has poor oral bioavailability. Thus, we evaluated whether the antiatherosclerotic effect of berberine is related to alterations in gut microbial structure and if so, whether specific bacterial taxa contribute to the beneficial effects of berberine.

METHODS

Apoe^-/- mice were fed either a normal-chow diet or a high-fat diet (HFD). Berberine was administered to mice in drinking water (0.5 g/L) for 14 weeks. Gut microbiota profiles were established by high throughput sequencing of the V3-V4 region of the bacterial 16S ribosomal RNA gene. The effects of berberine on metabolic endotoxemia, tissue inflammation and gut barrier integrity were also investigated.

RESULTS

Berberine treatment significantly reduced atherosclerosis in HFD-fed mice. Akkermansia spp. abundance was markedly increased in HFD-fed mice treated with berberine. Moreover, berberine decreased HFD-induced metabolic endotoxemia and lowered arterial and intestinal expression of proinflammatory cytokines and chemokines. Berberine treatment increased intestinal expression of tight junction proteins and the thickness of the colonic mucus layer, which are related to restoration of gut barrier integrity in HFD-fed mice.

CONCLUSIONS

Modulation of gut microbiota, specifically an increase in the abundance of Akkermansia, may contribute to the antiatherosclerotic and metabolic protective effects of berberine, which is poorly absorbed orally. Our findings therefore support the therapeutic value of gut microbiota manipulation in treating atherosclerosis.

Lychee (Litchi chinensis Sonn.) Pulp Phenolic Extract Provides Protection against Alcoholic Liver Injury in Mice by Alleviating Intestinal Microbiota Dysbiosis, Intestinal Barrier Dysfunction, and Liver Inflammation

Liver injury is the most common consequence of alcohol abuse, which is promoted by the inflammatory response triggered by gut-derived endotoxins produced as a consequence of intestinal microbiota dysbiosis and barrier dysfunction. The aim of this study was to investigate whether modulation of intestinal microbiota and barrier function, and liver inflammation contributes to the hepatoprotective effect of lychee pulp phenolic extract (LPPE) in alcohol-fed mice. Mice were treated with an ethanol-containing liquid diet alone or in combination with LPPE for 8 weeks. LPPE supplementation alleviated ethanol-induced liver injury and downregulated key markers of inflammation. Moreover, LPPE supplementation reversed the ethanol-induced alteration of intestinal microbiota composition and increased the expression of intestinal tight junction proteins, mucus protecting proteins, and antimicrobial proteins. Furthermore, in addition to decreasing serum endotoxin level, LPPE supplementation suppressed CD14 and toll-like receptor 4 expression, and repressed the activation of nuclear factor-κB p65 in the liver. These data suggest that intestinal microbiota dysbiosis, intestinal barrier dysfunction, and liver inflammation are improved by LPPE, and therefore, the intake of LPPE or Litchi pulp may be an effective strategy to alleviate the susceptibility to alcohol-induced hepatic diseases.

Innovation in microbiome-based strategies for promoting metabolic health

PURPOSE OF REVIEW

Update on the development of microbiome-based interventions and dietary supplements to combat obesity and related comorbidities, which are leading causes of global mortality.

RECENT FINDINGS

The role of intestinal dysbiosis, partly resulting from unhealthy diets, in the development of obesity and metabolic disorders, is well documented by recent translational research. Human experimental trials with whole-faecal transplants are ongoing, and their results will be crucial as proof of concept that interventions intended to modulate the microbiome composition and function could be alternatives for the management of obesity and related comorbidities. Potential next-generation probiotic bacteria (Akkermansia, Bacteroides spp., Eubacterium halli) and microbiota-derived molecules (e.g. membrane proteins, short-chain fatty acids) are being evaluated in preclinical and clinical trials to promote the development of innovative dietary supplements. The fact that live or inactivated bacteria and their products can regulate pathways that increase energy expenditure, and reduce energy intake, and absorption and systemic inflammation make them attractive research targets from a nutritional and clinical perspective.

SUMMARY

Understanding which are the beneficial bacteria and their bioactive products is helping us to envisage innovative microbiome-based dietary interventions to tackle obesity. Advances will likely result from future refinements of these strategies according to the individual's microbiome configuration and its particular response to interventions, thereby progressing towards personalized nutrition.

Inflammatory bactericidal lectin RegIIIβ: Friend or foe for the host?

In the inflamed gut, the bactericidal lectin RegIIIβ is massively produced by intestinal mucosa. RegIIIβ binds peptidoglycan and lipid A respectively, and thus can kill certain Gram-positive and Gram-negative bacteria, including the gut commensal microbiota and enteropathogenic bacteria. Considering the expression pattern and bactericidal activity, RegIIIβ is believed to be a host defense factor for protecting against the infection with enteropathogenic bacteria. However, it was poorly understood how RegIIIβ recognizes the target bacteria and kill them, and how RegIIIβ plays role(s) in infectious diarrhea. Therefore, our recent study has focused on RegIIIβ-target recognition, killing of Gram-negative bacteria, and host protective functions of RegIIIβ for infectious diarrhea inflicted by Salmonella Typhimurium. Here, we discuss novel insights into the protective role of RegIIIβ in infectious diarrhea, and propose avenues towards novel therapeutic interventions for Salmonella diarrhea.

Emerging Trends in "Smart Probiotics": Functional Consideration for the Development of Novel Health and Industrial Applications

The link between gut microbiota and human health is well-recognized and described. This ultimate impact on the host has contributed to explain the mutual dependence between humans and their gut bacteria. Gut microbiota can be manipulated through passive or active strategies. The former includes diet, lifestyle, and environment, while the latter comprise antibiotics, pre- and probiotics. Historically, conventional probiotic strategies included a phylogenetically limited diversity of bacteria and some yeast strains. However, biotherapeutic strategies evolved in the last years with the advent of fecal microbiota transplant (FMT), successfully applied for treating CDI, IBD, and other diseases. Despite the positive outcomes, long-term effects resulting from the uncharacterized nature of FMT are not sufficiently studied. Thus, developing strategies to simulate the FMT, using characterized gut colonizers with identified phylogenetic diversity, may be a promising alternative. As the definition of probiotics states that the microorganism should have beneficial effects on the host, several bacterial species with proven efficacy have been considered next generation probiotics. Non-conventional candidate strains include Akkermansia muciniphila, Faecalibacterium prausnitzii, Bacteroides fragilis, and members of the Clostridia clusters IV, XIVa, and XVIII. However, viable intestinal delivery is one of the current challenges, due to their stringent survival conditions. In this review, we will cover current perspectives on the development and assessment of next generation probiotics and the approaches that industry and stakeholders must consider for a successful outcome.

Beyond gut feelings: how the gut microbiota regulates blood pressure

Hypertension is the leading risk factor for heart disease and stroke, and is estimated to cause 9.4 million deaths globally every year. The pathogenesis of hypertension is complex, but lifestyle factors such as diet are important contributors to the disease. High dietary intake of fruit and vegetables is associated with reduced blood pressure and lower cardiovascular mortality. A critical relationship between dietary intake and the composition of the gut microbiota has been described in the literature, and a growing body of evidence supports the role of the gut microbiota in the regulation of blood pressure. In this Review, we describe the mechanisms by which the gut microbiota and its metabolites, including short-chain fatty acids, trimethylamine N-oxide, and lipopolysaccharides, act on downstream cellular targets to prevent or contribute to the pathogenesis of hypertension. These effects have a direct influence on tissues such as the kidney, the endothelium, and the heart. Finally, we consider the role of the gut microbiota in resistant hypertension, the possible intergenerational effect of the gut microbiota on blood pressure regulation, and the promising therapeutic potential of gut microbiota modification to improve health and prevent disease.

Chondroitin sulfate disaccharides modified the structure and function of the murine gut microbiome under healthy and stressed conditions

Chondroitin sulfate (CS) has been widely used for medical and nutraceutical purposes due to its roles in maintaining tissue structural integrity. We investigated if CS disaccharides may act as a bioactive compound and modulate gut microbial composition in mice. Our data show that CS disaccharides supplementation for 16 days significantly reduced blood LPS in the mice experiencing exhaustive exercise stress. CS disaccharides partially restored total fecal short-chain fatty acids from the level significantly repressed in mice under the stress. Our findings demonstrated that CS was likely butyrogenic and resulted in a significant increase in fecal butyrate concentration. CS disaccharides had a profound impact on gut microbial composition, affecting the abundance of 13.6% and 7.3% Operational Taxonomic Units in fecal microbial communities in healthy and stressed mice, respectively. CS disaccharides reduced the prevalence of inflammatory Proteobacteria. Together, our findings demonstrated that CS may ameliorate stress-induced intestinal inflammation. Furthermore, CS significantly increased intestinal Bacteroides acidifaciens population, indirectly exerting its immunomodulatory effect on the intestine. CS disaccharides had a significant impact on a broad range of biological pathways under stressed condition, such as ABC transporters, two-component systems, and carbohydrate metabolism. Our results will facilitate the development of CS as a bioactive nutraceutical.

Associations between hepatic miRNA expression, liver triacylglycerols and gut microbiota during metabolic adaptation to high-fat diet in mice

AIMS/HYPOTHESIS

Despite the current pandemic of metabolic diseases, our understanding of the diverse nature of the development of metabolic alterations in people who eat a high-fat diet (HFD) is still poor. We recently demonstrated a cardio-metabolic adaptation in mice fed an HFD, which was characterised by a specific gut and periodontal microbiota profile. Since the severity of hepatic disease is characterised by specific microRNA (miRNA) signatures and the gut microbiota is a key driver of both hepatic disease and miRNA expression, we analysed the expression of three hepatic miRNA and studied their correlation with hepatic triacylglycerol content and gut microbiota.

METHODS

Two cohorts of C57BL/6 4-week-old wild-type (WT) male mice (n = 62 and n = 96) were fed an HFD for 3 months to provide a model of metabolic adaptation. Additionally 8-week-old C57BL/6 mice, either WT or of different genotypes, with diverse gut microbiota (ob/ob, Nod1, Cd14 knockout [Cd14KO] and Nod2) or without gut microbiota (axenic mice) were fed a normal chow diet. Following which, glycaemic index, body weight, blood glucose levels and hepatic triacylglycerol levels were measured. Gut (caecum) microbiota taxa were analysed by pyrosequencing. To analyse hepatic miRNA expression, real-time PCR was performed on total extracted miRNA samples. Data were analysed using two-way ANOVA followed by the Dunnett's post hoc test, or by the unpaired Student's t test. A cluster analysis and multivariate analyses were also performed.

RESULTS

Our results demonstrated that the expression of miR-181a, miR-666 and miR-21 in primary murine hepatocytes is controlled by lipopolysaccharide in a dose-dependent manner. Of the gut microbiota, Firmicutes were positively correlated and Proteobacteria and Bacteroides acidifaciens were negatively correlated with liver triacylglycerol levels. Furthermore, the relative abundance of Firmicutes was negatively correlated with hepatic expression of miR-666 and miR-21. In contrast, the relative abundance of B. acidifaciens was positively correlated with miR-21.

CONCLUSIONS/INTERPRETATION

We propose the involvement of hepatic miRNA, liver triacylglycerols and gut microbiota as a new triad that underlies the molecular mechanisms by which gut microbiota governs hepatic pathophysiology during metabolic adaptation to HFD.

High-Fiber Diet and Acetate Supplementation Change the Gut Microbiota and Prevent the Development of Hypertension and Heart Failure in Hypertensive Mice

Background:

Dietary intake of fruit and vegetables is associated with lower incidence of hypertension, but the mechanisms involved have not been elucidated. Here, we evaluated the effect of a high-fiber diet and supplementation with the short-chain fatty acid acetate on the gut microbiota and the prevention of cardiovascular disease.

Methods:

Gut microbiome, cardiorenal structure/function, and blood pressure were examined in sham and mineralocorticoid excess–treated mice with a control diet, high-fiber diet, or acetate supplementation. We also determined the renal and cardiac transcriptome of mice treated with the different diets.

Results:

We found that high consumption of fiber modified the gut microbiota populations and increased the abundance of acetate-producing bacteria independently of mineralocorticoid excess. Both fiber and acetate decreased gut dysbiosis, measured by the ratio of Firmicutes to Bacteroidetes, and increased the prevalence of Bacteroides acidifaciens . Compared with mineralocorticoid-excess mice fed a control diet, both high-fiber diet and acetate supplementation significantly reduced systolic and diastolic blood pressures, cardiac fibrosis, and left ventricular hypertrophy. Acetate had similar effects and markedly reduced renal fibrosis. Transcriptome analyses showed that the protective effects of high fiber and acetate were accompanied by the downregulation of cardiac and renal Egr1 , a master cardiovascular regulator involved in cardiac hypertrophy, cardiorenal fibrosis, and inflammation. We also observed the upregulation of a network of genes involved in circadian rhythm in both tissues and downregulation of the renin-angiotensin system in the kidney and mitogen-activated protein kinase signaling in the heart.

Conclusions:

A diet high in fiber led to changes in the gut microbiota that played a protective role in the development of cardiovascular disease. The favorable effects of fiber may be explained by the generation and distribution of one of the main metabolites of the gut microbiota, the short-chain fatty acid acetate. Acetate effected several molecular changes associated with improved cardiovascular health and function.

The gut microbiota: a key regulator of metabolic diseases

The prevalence of obesity and type 2 diabetes, two closely linked metabolic disorders, is increasing worldwide. Over the past decade, the connection between these disorders and the microbiota of the gut has become a major focus of biomedical research, with recent studies demonstrating the fundamental role of intestinal microbiota in the regulation and pathogenesis of metabolic disorders. Because of the complexity of the microbiota community, however, the underlying molecular mechanisms by which the gut microbiota is associated with metabolic disorders remain poorly understood. In this review, we summarize recent studies that investigate the role of the microbiota in both human subjects and animal models of disease and discuss relevant therapeutic targets for future research. [BMB Reports 2016; 49(10): 536-541]

The biphasic dose effect of lychee (Litchi chinensis Sonn.) pulp phenolic extract on alcoholic liver disease in mice

Lychee pulp phenolic extract (LPPE) has a biphasic dose response in ethanol-induced liver injury in mice.

Microbiome and metabolic disease: revisiting the bacterial phylum Bacteroidetes

Bacterial species composition in the gut has emerged as an important factor in obesity and its related metabolic diseases such as type 2 diabetes. Out of thousands of bacterial species-level phylotypes inhabiting the human gut, the majority belong to two dominant phyla, the Bacteroidetes and Firmicutes. Members of the Bacteroidetes in particular have been associated with human metabolic diseases. However, their associations with disease are not always consistent between studies. Delving deeper into the diversity within the Bacteroidetes reveals a vast diversity in genomes and capacities, which partly explain how not all members respond equally to similar environmental conditions in their hosts. Here, we discuss the Bacteroidetes phylum, associations of its members with metabolic phenotypes, and efforts to characterize functionally their interactions with their hosts. Harnessing the Bacteroidetes to promote metabolic health will require a nuanced understanding of how specific strains interact with their microbial neighbors and their hosts under various conditions.