Negative association of antibiotics on clinical activity of immune checkpoint inhibitors in patients with advanced renal cell and non-small-cell lung cancer

Background

The composition of gut microbiota affects antitumor immune responses, preclinical and clinical outcome following immune checkpoint inhibitors (ICI) in cancer. Antibiotics (ATB) alter gut microbiota diversity and composition leading to dysbiosis, which may affect effectiveness of ICI.

Patients and methods

We examined patients with advanced renal cell carcinoma (RCC) and non-small-cell lung cancer (NSCLC) treated with anti-programmed cell death ligand-1 mAb monotherapy or combination at two academic institutions. Those receiving ATB within 30 days of beginning ICI were compared with those who did not. Objective response, progression-free survival (PFS) determined by RECIST1.1 and overall survival (OS) were assessed.

Results

Sixteen of 121 (13%) RCC patients and 48 of 239 (20%) NSCLC patients received ATB. The most common ATB were β-lactam or quinolones for pneumonia or urinary tract infections. In RCC patients, ATB compared with no ATB was associated with increased risk of primary progressive disease (PD) (75% versus 22%, P < 0.01), shorter PFS [median 1.9 versus 7.4 months, hazard ratio (HR) 3.1, 95% confidence interval (CI) 1.4-6.9, P < 0.01], and shorter OS (median 17.3 versus 30.6 months, HR 3.5, 95% CI 1.1-10.8, P = 0.03). In NSCLC patients, ATB was associated with similar rates of primary PD (52% versus 43%, P = 0.26) but decreased PFS (median 1.9 versus 3.8 months, HR 1.5, 95% CI 1.0-2.2, P = 0.03) and OS (median 7.9 versus 24.6 months, HR 4.4, 95% CI 2.6-7.7, P < 0.01). In multivariate analyses, the impact of ATB remained significant for PFS in RCC and for OS in NSCLC.

Conclusion

ATB were associated with reduced clinical benefit from ICI in RCC and NSCLC. Modulatation of ATB-related dysbiosis and gut microbiota composition may be a strategy to improve clinical outcomes with ICI.

Impacts of polystyrene microplastic on the gut barrier, microbiota and metabolism of mice

Microplastics (MPs), which are new environmental pollutants with a diameter of <5 mm, have received wide attention in recent years. However, there are still very limited data regarding the risks of MPs to animals, especially higher mammals. In this study, we exposed male mice to 5 μm pristine and fluorescent polystyrene MP for six weeks. The results showed that the polystyrene MP was observed in the guts of mice and could reduce the intestinal mucus secretion and cause damage the intestinal barrier function. In addition, high-throughput sequencing of the V3-V4 region of the 16S rRNA gene was used to explore the change of the gut microbiota composition in the cecal content. At the phylum level, the content of Actinobacteria decreased significantly in the polystyrene MP-treated group. The PD whole-tree indexes of the alpha diversity and principal component analysis (PCA) of the beta diversity indicated that the diversity of gut microbiota was altered after polystyrene MP exposure. At the genus level, a total of 15 types of bacteria changed significantly after exposure to polystyrene MP. Furthermore, the predicted KEGG (Kyoto Encyclopedia of Genes and Genomes) metabolic pathway differences indicated that the main metabolic pathways of the functional genes in the microbial community were significantly influenced by the polystyrene MP. In addition, indexes of amino acid metabolism and bile acid metabolism in the serum were analyzed after polystyrene MP exposure. These results indicated that polystyrene MP caused metabolic disorders. In conclusion, the polystyrene MP induced gut microbiota dysbiosis, intestinal barrier dysfunction and metabolic disorders in mice. This study provided more data on the toxicity of MPs in a terrestrial organism to aid in the assessment of the health risks of polystyrene MP to animals.

Polystyrene microplastics induce gut microbiota dysbiosis and hepatic lipid metabolism disorder in mice

Microplastic (MP) has become a concerning global environmental problem. It is toxic to aquatic organisms and can spread through the food chain to ultimately pose a threat to humans. In the environment, MP can interact with microbes and act as a microbial habitat. However, effects of polystyrene MP on the gut microbiota in mammals remain unclear. Here, male mice were exposed to two different sizes of polystyrene MP for 5 weeks to explore its effect. We observed that oral exposure to 1000 μg/L of 0.5 and 50 μm polystyrene MP decreased the body, liver and lipid weights in mice. Mucus secretion in the gut decreased in both sizes of polystyrene MP-treated groups. Regarding the gut microbiota, at the phylum level, polystyrene MP exposure decreased the relative abundances of Firmicutes and α-Proteobacteria in the feces. Furthermore, high throughput sequencing of the V3-V4 region of the 16S rRNA gene revealed significant changes in the richness and diversity of the gut microbiota in the cecums of polystyrene MP-treated mice. At the genus level, a total of 6 and 8 types of bacteria changed in the 0.5 and 50 μm polystyrene MP-treated groups, respectively. Furthermore, an operational taxonomic unit (OTU) analysis identified that 310 and 160 gut microbes were changed in the 0.5 and 50 μm polystyrene MP-treated groups, respectively. In addition, the hepatic triglyceride (TG) and total cholesterol (TCH) levels decreased in both 1000 μg/L 0.5 and 50 μm polystyrene MP-treated groups. Correspondingly, the relative mRNA levels of some key genes related to lipogenesis and TG synthesis decreased in the liver and epididymal fat. These results indicated that polystyrene MP could modify the gut microbiota composition and induce hepatic lipid disorder in mice; while the mouse is a common mammal model, consequently, the health risks of MP to animals should not be ignored.

Microplastics induce intestinal inflammation, oxidative stress, and disorders of metabolome and microbiome in zebrafish

Microplastics (MPs) can be ingested by a variety of species and mainly accumulate in the gut. However, the consequences of MPs exposure in the gut are largely unknown. Here we evaluated the impacts of MPs exposure in zebrafish gut. Animals were experimentally exposed to polystyrene MPs (5-μm beads; 50 μg/L and 500 μg/L) for 21 days and monitored for alterations in tissue histology, enzymatic biomarkers, gut microbiome and metabolomic responses. Inflammation and oxidative stress were observed in the zebrafish gut after exposed to MPs. Furthermore, significant alterations in the gut microbiome and tissue metabolic profiles were observed, with most of these were associated with oxidative stress, inflammation and lipid metabolism. This study provides evidence that MPs exposure causes gut damage as well as alterations in gut metabolome and microbiome, yielding novel insights into the consequences of MPs exposure.

Polystyrene microplastics induce microbiota dysbiosis and inflammation in the gut of adult zebrafish

Microplastic (MP) are environmental pollutants and have the potential to cause varying degrees of aquatic toxicity. In this study, the effects on gut microbiota of adult male zebrafish exposed for 14 days to 100 and 1000 μg/L of two sizes of polystyrene MP were evaluated. Both 0.5 and 50 μm-diameter spherical polystyrene MP increased the volume of mucus in the gut at a concentration of 1000 μg/L (about 1.456 × 10¹⁰ particles/L for 0.5 μm and 1.456 × 10⁴ particles/L for 50 μm). At the phylum level, the abundance of Bacteroidetes and Proteobacteria decreased significantly and the abundance of Firmicutes increased significantly in the gut after 14-day exposure to 1000 μg/L of both sizes of polystyrene MP. In addition, high throughput sequencing of the 16S rRNA gene V3-V4 region revealed a significant change in the richness and diversity of microbiota in the gut of polystyrene MP-exposed zebrafish. A more in depth analysis, at the genus level, revealed that a total of 29 gut microbes identified by operational taxonomic unit (OTU) analysis were significantly changed in both 0.5 and 50 μm-diameter polystyrene MP-treated groups. Moreover, it was observed that 0.5 μm polystyrene MP not only increased mRNA levels of IL1α, IL1β and IFN but also their protein levels in the gut, indicating that inflammation occurred after polystyrene MP exposure. Our findings suggest that polystyrene MP could induce microbiota dysbiosis and inflammation in the gut of adult zebrafish.

Cognitive impairment by antibiotic-induced gut dysbiosis: Analysis of gut microbiota-brain communication

Emerging evidence indicates that disruption of the gut microbial community (dysbiosis) impairs mental health. Germ-free mice and antibiotic-induced gut dysbiosis are two approaches to establish causality in gut microbiota-brain relationships. However, both models have limitations, as germ-free mice display alterations in blood-brain barrier and brain ultrastructure and antibiotics may act directly on the brain. We hypothesized that the concerns related to antibiotic-induced gut dysbiosis can only adequately be addressed if the effect of intragastric treatment of adult mice with multiple antibiotics on (i) gut microbial community, (ii) metabolite profile in the colon, (iii) circulating metabolites, (iv) expression of neuronal signaling molecules in distinct brain areas and (v) cognitive behavior is systematically investigated. Of the antibiotics used (ampicillin, bacitracin, meropenem, neomycin, vancomycin), ampicillin had some oral bioavailability but did not enter the brain. 16S rDNA sequencing confirmed antibiotic-induced microbial community disruption, and metabolomics revealed that gut dysbiosis was associated with depletion of bacteria-derived metabolites in the colon and alterations of lipid species and converted microbe-derived molecules in the plasma. Importantly, novel object recognition, but not spatial, memory was impaired in antibiotic-treated mice. This cognitive deficit was associated with brain region-specific changes in the expression of cognition-relevant signaling molecules, notably brain-derived neurotrophic factor, N-methyl-d-aspartate receptor subunit 2B, serotonin transporter and neuropeptide Y system. We conclude that circulating metabolites and the cerebral neuropeptide Y system play an important role in the cognitive impairment and dysregulation of cerebral signaling molecules due to antibiotic-induced gut dysbiosis.

Antibiotics, pediatric dysbiosis, and disease

Antibiotics are by far the most common medications prescribed for children. Recent epidemiological data suggests an association between early antibiotic use and disease phenotypes in adulthood. Antibiotic use during infancy induces imbalances in gut microbiota, called dysbiosis. The gut microbiome's responses to antibiotics and its potential link to disease development are especially complex to study in the changing infant gut. Here, we synthesize current knowledge linking antibiotics, dysbiosis, and disease and propose a framework for studying antibiotic-related dysbiosis in children. We recommend future studies into the microbiome-mediated effects of antibiotics focused on four types of dysbiosis: loss of keystone taxa, loss of diversity, shifts in metabolic capacity, and blooms of pathogens. Establishment of a large and diverse baseline cohort to define healthy infant microbiome development is essential to advancing diagnosis, interpretation, and eventual treatment of pediatric dysbiosis. This approach will also help provide evidence-based recommendations for antibiotic usage in infancy.

Gut Microbiota and the Neuroendocrine System

The microbial ecosystem that inhabits the gastrointestinal tract of all mammals-the gut microbiota-has been in a symbiotic relationship with its hosts over many millennia. Thanks to modern technology, the myriad of functions that are controlled or modulated by the gut microbiota are beginning to unfold. One of the systems that is emerging to closely interact with the gut microbiota is the body's major neuroendocrine system that controls various body processes in response to stress, the hypothalamic-pituitary-adrenal (HPA) axis. This interaction is of pivotal importance; as various disorders of the microbiota-gut-brain axis are associated with dysregulation of the HPA axis. The present contribution describes the bidirectional communication between the gut microbiota and the HPA axis and delineates the potential underlying mechanisms. In this regard, it is important to note that the communication between the gut microbiota and the HPA axis is closely interrelated with other systems, such as the immune system, the intestinal barrier and blood-brain barrier, microbial metabolites, and gut hormones, as well as the sensory and autonomic nervous systems. These communication pathways will be exemplified through preclinical models of early life stress, beneficial roles of probiotics and prebiotics, evidence from germ-free mice, and antibiotic-induced modulation of the gut microbiota.

Antibiotics, gut microbiota, and Alzheimer's disease

Alzheimer's disease (AD) is a neurodegenerative disease whose various pathophysiological aspects are still being investigated. Recently, it has been hypothesized that AD may be associated with a dysbiosis of microbes in the intestine. In fact, the intestinal flora is able to influence the activity of the brain and cause its dysfunctions.Given the growing interest in this topic, the purpose of this review is to analyze the role of antibiotics in relation to the gut microbiota and AD. In the first part of the review, we briefly review the role of gut microbiota in the brain and the various theories supporting the hypothesis that dysbiosis can be associated with AD pathophysiology. In the second part, we analyze the possible role of antibiotics in these events. Antibiotics are normally used to remove or prevent bacterial colonization in the human body, without targeting specific types of bacteria. As a result, broad-spectrum antibiotics can greatly affect the composition of the gut microbiota, reduce its biodiversity, and delay colonization for a long period after administration. Thus, the action of antibiotics in AD could be wide and even opposite, depending on the type of antibiotic and on the specific role of the microbiome in AD pathogenesis.Alteration of the gut microbiota can induce changes in brain activity, which raise the possibility of therapeutic manipulation of the microbiome in AD and other neurological disorders. This field of research is currently undergoing great development, but therapeutic applications are still far away. Whether a therapeutic manipulation of gut microbiota in AD could be achieved using antibiotics is still not known. The future of antibiotics in AD depends on the research progresses in the role of gut bacteria. We must first understand how and when gut bacteria act to promote AD. Once the role of gut microbiota in AD is well established, one can think to induce modifications of the gut microbiota with the use of pre-, pro-, or antibiotics to produce therapeutic effects.

Inflammatory pathways in alcoholic steatohepatitis

Inflammatory processes are primary contributors to the development and progression of alcoholic steatohepatitis (ASH), with severe alcoholic hepatitis characterised by non-resolving inflammation. Inflammation in the progression of ASH is a complex response to microbial dysbiosis, loss of barrier integrity in the intestine, hepatocellular stress and death, as well as inter-organ crosstalk. Herein, we review the roles of multiple cell types that are involved in inflammation in ASH, including resident macrophages and infiltrating monocytes, as well as other cell types in the innate and adaptive immune system. In response to chronic, heavy alcohol exposure, hepatocytes themselves also contribute to the inflammatory process; hepatocytes express a large number of chemokines and inflammatory mediators and can also release damage-associated molecular patterns during injury and death. These cellular responses are mediated and accompanied by changes in the expression of pro- and anti-inflammatory cytokines and chemokines, as well as by signals which orchestrate the recruitment of immune cells and activation of the inflammatory process. Additional mechanisms for cell-cell and inter-organ communication in ASH are also reviewed, including the roles of extracellular vesicles and microRNAs, as well as inter-organ crosstalk. We highlight the concept that inflammation also plays an important role in promoting liver repair and controlling bacterial infection. Understanding the complex regulatory processes that are disrupted during the progression of ASH will likely lead to better targeted strategies for therapeutic interventions.

The interaction between vaginal microbiota, cervical length, and vaginal progesterone treatment for preterm birth risk

BACKGROUND

Preterm birth is the primary cause of infant death worldwide. A short cervix in the second trimester of pregnancy is a risk factor for preterm birth. In specific patient cohorts, vaginal progesterone reduces this risk. Using 16S rRNA gene sequencing, we undertook a prospective study in women at risk of preterm birth (n = 161) to assess (1) the relationship between vaginal microbiota and cervical length in the second trimester and preterm birth risk and (2) the impact of vaginal progesterone on vaginal bacterial communities in women with a short cervix.

RESULTS

Lactobacillus iners dominance at 16 weeks of gestation was significantly associated with both a short cervix <25 mm (n = 15, P < 0.05) and preterm birth <34⁺⁰ weeks (n = 18; P < 0.01; 69% PPV). In contrast, Lactobacillus crispatus dominance was highly predictive of term birth (n = 127, 98% PPV). Cervical shortening and preterm birth were not associated with vaginal dysbiosis. A longitudinal characterization of vaginal microbiota (<18, 22, 28, and 34 weeks) was then undertaken in women receiving vaginal progesterone (400 mg/OD, n = 25) versus controls (n = 42). Progesterone did not alter vaginal bacterial community structure nor reduce L. iners-associated preterm birth (<34 weeks).

CONCLUSIONS

L. iners dominance of the vaginal microbiota at 16 weeks of gestation is a risk factor for preterm birth, whereas L. crispatus dominance is protective against preterm birth. Vaginal progesterone does not appear to impact the pregnancy vaginal microbiota. Patients and clinicians who may be concerned about "infection risk" associated with the use of a vaginal pessary during high-risk pregnancy can be reassured.

Pharmacomicrobiomics: exploiting the drug-microbiota interactions in anticancer therapies

Cancer is a major health burden worldwide, and despite continuous advances in medical therapies, resistance to standard drugs and adverse effects still represent an important cause of therapeutic failure. There is a growing evidence that gut bacteria can affect the response to chemo- and immunotherapeutic drugs by modulating either efficacy or toxicity. Moreover, intratumor bacteria have been shown to modulate chemotherapy response. At the same time, anticancer treatments themselves significantly affect the microbiota composition, thus disrupting homeostasis and exacerbating discomfort to the patient. Here, we review the existing knowledge concerning the role of the microbiota in mediating chemo- and immunotherapy efficacy and toxicity and the ability of these therapeutic options to trigger dysbiotic condition contributing to the severity of side effects. In addition, we discuss the use of probiotics, prebiotics, synbiotics, postbiotics, and antibiotics as emerging strategies for manipulating the microbiota in order to improve therapeutic outcome or at least ensure patients a better quality of life all along of anticancer treatments.

Dietary fructose-induced gut dysbiosis promotes mouse hippocampal neuroinflammation: a benefit of short-chain fatty acids

BACKGROUND

Western-style diets arouse neuroinflammation and impair emotional and cognitive behavior in humans and animals. Our previous study showed that a high-fructose diet caused the hippocampal neuroinflammatory response and neuronal loss in animals, but the underlying mechanisms remained elusive. Here, alterations in the gut microbiota and intestinal epithelial barrier were investigated as the causes of hippocampal neuroinflammation induced by high-fructose diet.

RESULTS

A high-fructose diet caused the hippocampal neuroinflammatory response, reactive gliosis, and neuronal loss in C57BL/6N mice. Depletion of the gut microbiota using broad-spectrum antibiotics suppressed the hippocampal neuroinflammatory response in fructose-fed mice, but these animals still exhibited neuronal loss. Gut microbiota compositional alteration, short-chain fatty acids (SCFAs) reduction, intestinal epithelial barrier impairment, NOD-like receptor family pyrin domain-containing 6 (NLRP6) inflammasome dysfunction, high levels of serum endotoxin, and FITC-dextran were observed in fructose-fed mice. Of note, SCFAs, as well as pioglitazone (a selective peroxisome proliferator-activated receptor gamma (PPAR-γ) agonist), shaped the gut microbiota and ameliorated intestinal epithelial barrier impairment and NLRP6 inflammasome dysfunction in fructose-fed mice. Moreover, SCFAs-mediated NLRP6 inflammasome activation was inhibited by histamine (a bacterial metabolite) in ex vivo colonic explants and suppressed in murine CT26 colon carcinoma cells transfected with NLRP6 siRNA. However, pioglitazone and GW9662 (a PPAR-γ antagonist) exerted no impact on SCFAs-mediated NLRP6 inflammasome activation in ex vivo colonic explants, suggesting that SCFAs may stimulate NLRP6 inflammasome independently of PPAR-γ activation. SCFAs and pioglitazone prevented fructose-induced hippocampal neuroinflammatory response and neuronal loss in mice. Additionally, SCFAs activated colonic NLRP6 inflammasome and increased DCX+ newborn neurons in the hippocampal DG of control mice.

CONCLUSIONS

Our findings reveal that gut dysbiosis is a critical factor for a high-fructose diet-induced hippocampal neuroinflammation in C57BL/6N mice possibly mediated by impairing intestinal epithelial barrier. Mechanistically, the defective colonic NLRP6 inflammasome is responsible for intestinal epithelial barrier impairment. SCFAs can stimulate NLRP6 inflammasome and ameliorate the impairment of intestinal epithelial barrier, resulting in the protection against a high-fructose diet-induced hippocampal neuroinflammation and neuronal loss. This study addresses a gap in the understanding of neuronal injury associated with Western-style diets. A new intervention strategy for reducing the risk of neurodegenerative diseases through SCFAs supplementation or dietary fiber consumption is emphasized.

Microplastics and the gut microbiome: How chronically exposed species may suffer from gut dysbiosis

As small pieces of plastics known as microplastics pollute even the remotest parts of Earth, research currently focuses on unveiling how this pollution may affect biota. Despite increasing awareness, one potentially major consequence of chronic exposure to microplastics has been largely neglected: the impact of the disruption of the symbiosis between host and the natural community and abundance pattern of the gut microbiota. This so-called dysbiosis might be caused by the consumption of microplastics, associated mechanical disruption within the gastrointestinal tract, the ingestion of foreign and potentially pathogenic bacteria, as well as chemicals, which make-up or adhere to microplastics. Dysbiosis may interfere with the host immune system and trigger the onset of (chronic) diseases, promote pathogenic infections, and alter the gene capacity and expression of gut microbiota. We summarize how chronically exposed species may suffer from microplastics-induced gut dysbiosis, deteriorating host health, and highlight corresponding future directions of research.

Organophosphorus pesticide chlorpyrifos intake promotes obesity and insulin resistance through impacting gut and gut microbiota

BACKGROUND

Disruption of the gut microbiota homeostasis may induce low-grade inflammation leading to obesity-associated diseases. A major protective mechanism is to use the multi-layered mucus structures to keep a safe distance between gut epithelial cells and microbiota. To investigate whether pesticides would induce insulin resistance/obesity through interfering with mucus-bacterial interactions, we conducted a study to determine how long-term exposure to chlorpyrifos affected C57Bl/6 and CD-1 (ICR) mice fed high- or normal-fat diets. To further investigate the effects of chlorpyrifos-altered microbiota, antibiotic treatment and microbiota transplantation experiments were conducted.

RESULTS

The results showed that chlorpyrifos caused broken integrity of the gut barrier, leading to increased lipopolysaccharide entry into the body and finally low-grade inflammation, while genetic background and diet pattern have limited influence on the chlorpyrifos-induced results. Moreover, the mice given chlorpyrifos-altered microbiota had gained more fat and lower insulin sensitivity.

CONCLUSIONS

Our results suggest that widespread use of pesticides may contribute to the worldwide epidemic of inflammation-related diseases.

Proton pump inhibitors and dysbiosis: Current knowledge and aspects to be clarified

Proton pump inhibitors (PPIs) are common medications within the practice of gastroenterology. These drugs, which act through the irreversible inhibition of the hydrogen/potassium pump (H+/K+-ATPase pump) in the gastric parietal cells, are used in the treatment of several acid-related disorders. PPIs are generally well tolerated but, through the long-term reduction of gastric acid secretion, can increase the risk of an imbalance in gut microbiota composition (i.e., dysbiosis). The gut microbiota is a complex ecosystem in which microbes coexist and interact with the human host. Indeed, the resident gut bacteria are needed for multiple vital functions, such as nutrient and drug metabolism, the production of energy, defense against pathogens, the modulation of the immune system and support of the integrity of the gut mucosal barrier. The bacteria are collected in communities that vary in density and composition within each segment of the gastrointestinal (GI) tract. Therefore, every change in the gut ecosystem has been connected to an increased susceptibility or exacerbation of various GI disorders. The aim of this review is to summarize the recently available data on PPI-related microbiota alterations in each segment of the GI tract and to analyze the possible involvement of PPIs in the pathogenesis of several specific GI diseases.

FODMAP diet modulates visceral nociception by lipopolysaccharide-mediated intestinal inflammation and barrier dysfunction

Foods high in fermentable oligosaccharides, disaccharides, monosaccharides, and polyols (FODMAPs) exacerbate symptoms of irritable bowel syndrome (IBS); however, their mechanism of action is unknown. We hypothesized that a high-FODMAP (HFM) diet increases visceral nociception by inducing dysbiosis and that the FODMAP-altered gut microbial community leads to intestinal pathology. We fed rats an HFM and showed that HFM increases rat fecal Gram-negative bacteria, elevates lipopolysaccharides (LPS), and induces intestinal pathology, as indicated by inflammation, barrier dysfunction, and visceral hypersensitivity (VH). These manifestations were prevented by antibiotics and reversed by low-FODMAP (LFM) diet. Additionally, intracolonic administration of LPS or fecal supernatant (FS) from HFM-fed rats caused intestinal barrier dysfunction and VH, which were blocked by the LPS antagonist LPS-RS or by TLR4 knockdown. Fecal LPS was higher in IBS patients than in healthy subjects (HS), and IBS patients on a 4-week LFM diet had improved IBS symptoms and reduced fecal LPS levels. Intracolonic administration of FS from IBS patients, but not FS from HS or LFM-treated IBS patients, induced VH in rats, which was ameliorated by LPS-RS. Our findings indicate that HFM-associated gut dysbiosis and elevated fecal LPS levels induce intestinal pathology, thereby modulating visceral nociception and IBS symptomatology, and might provide an explanation for the success of LFM diet in IBS patients.

Gut bacteria are critical for optimal muscle function: a potential link with glucose homeostasis

Gut microbiota is involved in the development of several chronic diseases, including diabetes, obesity, and cancer, through its interactions with the host organs. It has been suggested that the cross talk between gut microbiota and skeletal muscle plays a role in different pathological conditions, such as intestinal chronic inflammation and cachexia. However, it remains unclear whether gut microbiota directly influences skeletal muscle function. In this work, we studied the impact of gut microbiota modulation on mice skeletal muscle function and investigated the underlying mechanisms. We determined the consequences of gut microbiota depletion after treatment with a mixture of a broad spectrum of antibiotics for 21 days and after 10 days of natural reseeding. We found that, in gut microbiota-depleted mice, running endurance was decreased, as well as the extensor digitorum longus muscle fatigue index in an ex vivo contractile test. Importantly, the muscle endurance capacity was efficiently normalized by natural reseeding. These endurance changes were not related to variation in muscle mass, fiber typology, or mitochondrial function. However, several pertinent glucose metabolism markers, such as ileum gene expression of short fatty acid chain and glucose transporters G protein-coupled receptor 41 and sodium-glucose cotransporter 1 and muscle glycogen level, paralleled the muscle endurance changes observed after treatment with antibiotics for 21 days and reseeding. Because glycogen is a key energetic substrate for prolonged exercise, modulating its muscle availability via gut microbiota represents one potent mechanism that can contribute to the gut microbiota-skeletal muscle axis. Taken together, our results strongly support the hypothesis that gut bacteria are required for host optimal skeletal muscle function.

Antibiotic use and the development of inflammatory bowel disease: a national case-control study in Sweden

BACKGROUND

Use of antibiotics in early life has been linked with childhood inflammatory bowel disease (IBD), but data for adults are mixed, and based on smaller investigations that did not compare risk among siblings with shared genetic or environmental risk factors. We aimed to investigate the association between antibiotic therapy and IBD in a large, population-based study.

METHODS

In this prospective case-control study, we identified people living in Sweden aged 16 years or older, with a diagnosis of IBD based on histology and at least one diagnosis code for IBD or its subtypes (ulcerative colitis and Crohn's disease). We identified consecutive patients with incident IBD from the ESPRESSO (Epidemiology Strengthened by histoPathology Reports in Sweden) study, cross-referenced with the Swedish Patient Register and the Prescribed Drug Register. We accrued data for cumulative antibiotic dispensations until 1 year before time of matching for patients and up to five general population controls per patient (matched on the basis of age, sex, county, and calendar year). We also included unaffected full siblings as a secondary control group. Conditional logistic regression was used to estimate multivariable-adjusted odds ratios (aORs) and 95% CIs for diagnosis of incident IBD.

FINDINGS

We identified 23 982 new patients with IBD (15 951 ulcerative colitis, 7898 Crohn's disease, 133 unclassified IBD) diagnosed between Jan 1, 2007, and Dec 31, 2016. 117 827 matched controls and 28 732 siblings were also identified. After adjusting for several risk factors, aOR in patients who had used antibiotics versus those who had never used antibiotics was 1·88 (95% CI 1·79-1·98) for diagnosis of incident IBD, 1·74 (1·64-1·85) for ulcerative colitis, and 2·27 (2·06-2·49) for Crohn's disease. aOR was higher in patients who had received one antibiotic dispensation (1·11, 1·07-1·15), two antibiotic dispensations (1·38, 1·32-1·44), and three or more antibiotic dispensations (1·55, 1·49-1·61) than patients who had none. Increased risk was noted for ulcerative colitis (aOR with three or more antibiotic dispensations 1·47, 95% CI 1·40-1·54) and Crohn's disease (1·64, 1·53-1·76) with higher estimates corresponding to broad-spectrum antibiotics. Similar but attenuated results were observed when siblings were used as the reference group, with an aOR of 1·35 (95% CI 1·28-1·43) for patients who had received three or more dispensations, compared with general population controls.

INTERPRETATION

Higher cumulative exposure to systemic antibiotic therapy, particularly treatments with greater spectrum of microbial coverage, may be associated with a greater risk of new-onset IBD and its subtypes. The association between antimicrobial treatment and IBD did not appear to differ when predisposed siblings were used as the reference controls. Our findings, if substantiated by longer-term prospective studies in humans or mechanistic preclinical investigations, suggest the need to further emphasise antibiotic stewardship to prevent the rise in dysbiosis-related chronic diseases, including IBD.

FUNDING

National Institutes of Health. Crohn's and Colitis Foundation.

Antibiotics induced intestinal tight junction barrier dysfunction is associated with microbiota dysbiosis, activated NLRP3 inflammasome and autophagy

Tight junction barrier is critical to intestinal homeostasis. Applying antibiotics to treat infections is common in clinical practice, which may affect intestinal microbiota. Intestinal microbiota dysbiosis is involved in the occurrence of some gastrointestinal diseases. Therefore, this study was aimed to investigate the influence of antibiotics on intestinal tight junction barrier and the possible underlying mechanisms. Healthy adult female C57BL/6 mice were treated with a broad-spectrum antibiotic cocktail for 14 days. 16S rDNA Illumina sequencing and headspace gas chromatography-mass spectrometry (HS-GC/MS) were respectively used to analyze microbial community and to detect short-chain fatty acids (SCFAs) contents. In vivo intestinal paracellular permeability to fluorescein isothiocyanate-dextran (FITC-dextran) was measured. Protein expression was determined by immunoblotting. Immunofluoresence was applied to observe the distributions of ZO-1, LC3B and ASC. Antibiotics remarkably altered intestinal microbiota composition in healthy mice, accompanying reduced SCFAs' concentrations. In addition, the intestinal tight junction barrier was disrupted by antibiotic treatment, as evidenced by increased intestinal paracellular permeability to FITC-dextran, decreased tight junction protein expressions, and disrupted ZO-1 morphology. Furthermore, NLRP3 inflammasome and autophagy were activated by antibiotic treatment. In conclusion, intestinal epithelial tight junction barrier dysfunction induced by antibiotics is associated with intestinal microbiota dysbiosis, activated NLRP3 inflammasome and autophagy in mice.

The Skin Microbiome: A New Actor in Inflammatory Acne

Our understanding of the role of Cutibacterium acnes in the pathophysiology of acne has recently undergone a paradigm shift: rather than C. acnes hyperproliferation, it is the loss of balance between the different C. acnes phylotypes, together with a dysbiosis of the skin microbiome, which results in acne development. The loss of diversity of C. acnes phylotypes acts as a trigger for innate immune system activation, leading to cutaneous inflammation. A predominance of C. acnes phylotype IA₁ has been observed, with a more virulent profile in acne than in normal skin. Other bacteria, mainly Staphylococcus epidermis, are also implicated in acne. S. epidermidis and C. acnes interact and are critical for the regulation of skin homeostasis. Recent studies also showed that the gut microbiome is involved in acne, through interactions with the skin microbiome. As commonly used topical and systemic antibiotics induce cutaneous dysbiosis, our new understanding of acne pathophysiology has prompted a change in direction for acne treatment. In the future, the development of individualized acne therapies will allow targeting of the pathogenic strains, leaving the commensal strains intact. Such alternative treatments, involving modifications of the microbiome, will form the next generation of ‘ecobiological’ anti-inflammatory treatments.

Probiotic Lactobacillus reuteri Prevents Postantibiotic Bone Loss by Reducing Intestinal Dysbiosis and Preventing Barrier Disruption

Antibiotic treatment, commonly prescribed for bacterial infections, depletes and subsequently causes long-term alterations in intestinal microbiota composition. Knowing the importance of the microbiome in the regulation of bone density, we investigated the effect of postantibiotic treatment on gut and bone health. Intestinal microbiome repopulation at 4-weeks postantibiotic treatment resulted in an increase in the Firmicutes:Bacteroidetes ratio, increased intestinal permeability, and notably reduced femoral trabecular bone volume (approximately 30%, p < 0.01). Treatment with a mucus supplement (a high-molecular-weight polymer, MDY-1001 [MDY]) prevented the postantibiotic-induced barrier break as well as bone loss, indicating a mechanistic link between increased intestinal permeability and bone loss. A link between the microbiome composition and bone density was demonstrated by supplementing the mice with probiotic bacteria. Specifically, Lactobacillus reuteri, but not Lactobacillus rhamnosus GG or nonpathogenic Escherichia coli, reduced the postantibiotic elevation of the Firmicutes:Bacteroidetes ratio and prevented femoral and vertebral trabecular bone loss. Consistent with causing bone loss, postantibiotic-induced dysbiosis decreased osteoblast and increased osteoclast activities, changes that were prevented by both L. reuteri and MDY. These data underscore the importance of microbial dysbiosis in the regulation of intestinal permeability and bone health, as well as identify L. reuteri and MDY as novel therapies for preventing these adverse effects. © 2018 American Society for Bone and Mineral Research.

Chronic exposure to low concentrations of lead induces metabolic disorder and dysbiosis of the gut microbiota in mice

Lead (Pb) is one of the most prevalent toxic, nonessential heavy metals that can contaminate food and water. In this study, effects of chronic exposure to low concentrations of Pb on metabolism and gut microbiota were evaluated in mice. It was observed that exposure of mice to 0.1mg/L Pb, supplied via drinking water, for 15weeks increased hepatic TG and TCH levels. The levels of some key genes related to lipid metabolism in the liver increased significantly in Pb-treated mice. For the gut microbiota, at the phylum level, the relative abundance of Firmicutes and Bacteroidetes changed obviously in the feces and the cecal contents of mice exposed to 0.1mg/L Pb for 15weeks. In addition, 16s rRNA gene sequencing further discovered that Pb exposure affected the structure and richness of the gut microbiota. Moreover, a ¹H NMR metabolic analysis unambiguously identified 31 metabolites, and 15 metabolites were noticeably altered in 0.1mg/L Pb-treated mice. Taken together, the data indicate that chronic Pb exposure induces dysbiosis of the gut microbiota and metabolic disorder in mice.

CAPSULE

Chronic Pb exposure induces metabolic disorder, dysbiosis of the gut microbiota and hepatic lipid metabolism disorder in mice.

Candida albicans induces mucosal bacterial dysbiosis that promotes invasive infection

Infectious complications are a common cause of morbidity and mortality in cancer patients undergoing chemotherapy due to increased risk of oral and gastrointestinal candidiasis, candidemia and septicemia. Interactions between C. albicans and endogenous mucosal bacteria are important in understanding the mechanisms of invasive infection. We published a mouse intravenous chemotherapy model that recapitulates oral and intestinal mucositis, and myelosuppression in patients receiving 5-fluorouracil. We used this model to study the influence of C. albicans on the mucosal bacterial microbiome and compared global community changes in the oral and intestinal mucosa of the same mice. We validated 16S rRNA gene sequencing data by qPCR, in situ hybridization and culture approaches. Mice receiving both 5Fu and C. albicans had an endogenous bacterial overgrowth on the oral but not the small intestinal mucosa. C. albicans infection was associated with loss of mucosal bacterial diversity in both sites with indigenous Stenotrophomonas, Alphaproteobacteria and Enterococcus species dominating the small intestinal, and Enterococcus species dominating the oral mucosa. Both immunosuppression and Candida infection contributed to changes in the oral microbiota. Enterococci isolated from mice with oropharyngeal candidiasis were implicated in degrading the epithelial junction protein E-cadherin and increasing the permeability of the oral epithelial barrier in vitro. Importantly, depletion of these organisms with antibiotics in vivo attenuated oral mucosal E-cadherin degradation and C. albicans invasion without affecting fungal burdens, indicating that bacterial community changes represent overt dysbiosis. Our studies demonstrate a complex interaction between C. albicans, the resident mucosal bacterial microbiota and the host environment in pathogenesis. We shed significant new light on the role of C. albicans in shaping resident bacterial communities and driving mucosal dysbiosis.

Dysbiosis of gut microbiota by chronic coexposure to titanium dioxide nanoparticles and bisphenol A: Implications for host health in zebrafish

Gut microbiota is of critical relevance to host health. However, toxicological understanding of environmental pollutants on gut microbiota is limited, not to mention their combined effects. In the present study, adult zebrafish (Danio rerio) were exposed to titanium dioxide nanoparticles (nano-TiO₂; 100 μg/L), bisphenol A (BPA; 0, 2, and 20 μg/L) or their binary mixtures for three months. Sequencing of 16S rRNA amplicons found that nano-TiO₂ and BPA coexposure shifted the intestinal microbial community, interacting in an antagonistic manner when the BPA concentration was low but in a synergistic manner at a higher BPA concentration. Sex- and concentration-dependent responses to the coexposure regime were also observed for zebrafish growth and intestinal health (e.g. neurotransmission, epithelial barrier permeability, inflammation, and oxidative stress). Correlation analysis showed that oxidative stress after nano-TiO₂ and BPA coexposure was tightly associated with the imbalanced ratio of pathogenic Lawsonia and normal metabolic Hyphomicrobium, where higher abundance of Lawsonia but lower abundance of Hyphomicrobium were induced concurrently. A positive relationship was observed between zebrafish body weight and the abundance of Bacteroides in the gut, which was also closely associated with the genera of Anaerococcus, Finegoldia, and Peptoniphilus. This study revealed, for the first time, the combined effects of nano-TiO₂ and BPA coexposure on the dynamics of the gut microbiome, which proved to have toxicological implications for zebrafish host health.