The cross talk between microbiota and the immune system: metabolites take center stage

Inflammation-Related Factors Identified as Biomarkers of Dehydration and Subsequent Acute Kidney Injury in Agricultural Workers

Globally, there is increasing recognition that agricultural workers are at risk for chronic kidney disease of unknown etiology (CKDu). Recurrent heat exposure, physical exertion, dehydration, muscle damage, and inflammation are hypothesized to contribute to the development of CKDu, but the relative importance of these processes and the interactions among them remain unclear. Moreover, there is a need to identify biomarkers that could distinguish individuals who are at greatest risk for kidney damage to target preventative interventions for CKDu. In this study, we evaluated dehydration and markers of inflammation, muscle damage, and renal function in agricultural workers at a non-workday baseline assessment. Urine specific gravity and kidney function were measured before and after work shifts on three subsequent days, and heat index, core body temperature, and heart rate were monitored during the work shifts. A combination of direct comparisons and machine learning algorithms revealed that reduced levels of uromodulin and sodium in urine and increased levels of interleukin-6 and C-reactive protein in serum were indicative of dehydration at baseline, and that dehydration, high body mass index, reduced urine uromodulin, and increased serum interleukin-6, C-reactive protein, and lipopolysaccharide-binding protein at baseline were predictive of acute kidney injury on subsequent workdays. Our findings suggest a method for identifying agricultural workers at greatest risk for kidney injury and reveal potential mechanisms responsible for this process, including pathways overlapping in dehydration and kidney injury. These results will guide future studies confirming these mechanisms and introducing interventions to protect kidney health in this vulnerable population.

The Surviving Sepsis Campaign: Basic/Translational Science Research Priorities

Objectives:

Expound upon priorities for basic/translational science identified in a recent paper by a group of experts assigned by the Society of Critical Care Medicine and the European Society of Intensive Care Medicine.

Data Sources:

Original paper, search of the literature.

Study Selection:

By several members of the original task force with specific expertise in basic/translational science.

Data Extraction:

None.

Data Synthesis:

None.

Conclusions:

In the first of a series of follow-up reports to the original paper, several members of the original task force with specific expertise provided a more in-depth analysis of the five identified priorities directly related to basic/translational science. This analysis expounds on what is known about the question and what was identified as priorities for ongoing research. It is hoped that this analysis will aid the development of future research initiatives.

Probiotics in Fish Nutrition—Long-Standing Household Remedy or Native Nutraceuticals?

Over the last decades, aquaculture production increased rapidly. The future development of the industry highly relies on the sustainable utilization of natural resources. The need for improving disease resistance, growth performance, food conversion, and product safety for human consumption has stimulated the application of probiotics in aquaculture. Probiotics increase growth and feed conversion, improve health status, raise disease resistance, decrease stress susceptibility, and improve general vigor. Currently, most probiotics still originate from terrestrial sources rather than fish. However, host-associated (autochthonous) probiotics are likely more persistent in the gastrointestinal tract of fish and may, therefore, exhibit longer-lasting effects on the host. Probiotic candidates are commonly screened in in vitro assays, but the transfer to in vivo assessment is often problematic. In conclusion, modulation of the host-associated microbiome by the use of complex probiotics is promising, but a solid understanding of the interactions involved is only in its infancy and requires further research. Probiotics could be used to explore novel ingredients such as chitin-rich insect meal, which cannot be digested by the fish host alone. Most importantly, probiotics offer the opportunity to improve stress and disease resistance, which is among the most pressing problems in aquaculture.

Lung immune tone via gut-lung axis: gut-derived LPS and short-chain fatty acids' immunometabolic regulation of lung IL-1β, FFAR2, and FFAR3 expression

Microbial metabolites produced by the gut microbiome, e.g. short-chain fatty acids (SCFA), have been found to influence lung physiology and injury responses. However, how lung immune activity is regulated by SCFA is unknown. We examined fresh human lung tissue and observed the presence of SCFA with interindividual variability. In vitro, SCFA were capable of modifying the metabolic programming in LPS-exposed alveolar macrophages (AM). We hypothesized that lung immune tone could be defined by baseline detection of lung intracellular IL-1β. Therefore, we interrogated naïve mouse lungs with intact gut microbiota for IL-1β mRNA expression and localized its presence within alveolar spaces, specifically within AM subsets. We established that metabolically active gut microbiota, which produce SCFA, can transmit LPS and SCFA to the lung and thereby could create primed lung immunometabolic tone. To understand how murine lung cells sensed and upregulated IL-1β in response to gut microbiome-derived factors, we determined that, in vitro, AM and alveolar type II (AT2) cells expressed SCFA receptors, free fatty acid receptor 2 (FFAR2), free fatty acid receptor 3 (FFAR3), and IL-1β but with distinct expression patterns and different responses to LPS. Finally, we observed that IL-1β, FFAR2, and FFAR3 were expressed in isolated human AM and AT2 cells ex vivo, but in fresh human lung sections in situ, only AM expressed IL-1β at rest and after LPS challenge. Together, this translational study using mouse and human lung tissue and cells point to an important role for the gut microbiome and their SCFA in establishing and regulating lung immune tone.

Gut microbiota-derived metabolites in the regulation of host immune responses and immune-related inflammatory diseases

The gut microbiota has a critical role in the maintenance of immune homeostasis. Alterations in the intestinal microbiota and gut microbiota-derived metabolites have been recognized in many immune-related inflammatory disorders. These metabolites can be produced by gut microbiota from dietary components or by the host and can be modified by gut bacteria or synthesized de novo by gut bacteria. Gut microbiota-derived metabolites influence a plethora of immune cell responses, including T cells, B cells, dendritic cells, and macrophages. Some of these metabolites are involved in the pathogenesis of immune-related inflammatory diseases, such as inflammatory bowel diseases, diabetes, rheumatoid arthritis, and systemic lupus erythematosus. Here, we review the role of microbiota-derived metabolites in regulating the functions of different immune cells and the pathogenesis of chronic immune-related inflammatory diseases.

Gut Dysbiosis during Influenza Contributes to Pulmonary Pneumococcal Superinfection through Altered Short-Chain Fatty Acid Production

Secondary bacterial infections often complicate viral respiratory infections. We hypothesize that perturbation of the gut microbiota during influenza A virus (IAV) infection might favor respiratory bacterial superinfection. Sublethal infection with influenza transiently alters the composition and fermentative activity of the gut microbiota in mice. These changes are attributed in part to reduced food consumption. Fecal transfer experiments demonstrate that the IAV-conditioned microbiota compromises lung defenses against pneumococcal infection. In mechanistic terms, reduced production of the predominant short-chain fatty acid (SCFA) acetate affects the bactericidal activity of alveolar macrophages. Following treatment with acetate, mice colonized with the IAV-conditioned microbiota display reduced bacterial loads. In the context of influenza infection, acetate supplementation reduces, in a free fatty acid receptor 2 (FFAR2)-dependent manner, local and systemic bacterial loads. This translates into reduced lung pathology and improved survival rates of double-infected mice. Lastly, pharmacological activation of the SCFA receptor FFAR2 during influenza reduces bacterial superinfection.

Antitumor efficacy of a neoantigen cancer vaccine delivered by electroporation is influenced by microbiota composition

Cancer is a heterogeneous disease and its treatment remains unsatisfactory with inconstant therapeutic responses. This variability could be related, at least in part, to different and highly personalized gut microbiota compositions. Different studies have shown an impact of microbiota on antitumor therapy. It has been demonstrated that some gut bacteria influences the development and differentiation of immune cells, suggesting that different microbiota compositions could affect the efficacy of the antitumor vaccine. Emerging data suggest that recognition of neoantigens for the generation of neoantigen cancer vaccines (NCVs) could have a key role in the activity of clinical immunotherapies. However, it is still unknown whether there is a crosstalk between microbiota and NCV. This study aimed to understand the possible mechanisms of interaction between gut microbiota and NCV delivered by DNA-electroporation (DNA-EP). We found that decreased microbiota diversity induced by prolonged antibiotic (ATB) treatment is associated with higher intratumor specific immune responses and consequently to a better antitumor effect induced by NCV delivered by DNA-EP.

Dysbiosis in Pediatrics Is Associated with Respiratory Infections: Is There a Place for Bacterial-Derived Products?

Respiratory tract infections (RTIs) are common in childhood because of the physiologic immaturity of the immune system, a microbial community under development in addition to other genetic, physiological, environmental and social factors. RTIs tend to recur and severe lower viral RTIs in early childhood are not uncommon and are associated with increased risk of respiratory disorders later in life, including recurrent wheezing and asthma. Therefore, a better understanding of the main players and mechanisms involved in respiratory morbidity is necessary for a prompt and improved care as well as for primary prevention. The inter-talks between human immune components and microbiota as well as their main functions have been recently unraveled; nevertheless, more is still to be discovered or understood in the above medical conditions. The aim of this review paper is to provide the most up-to-date overview on dysbiosis in pre-school children and its association with RTIs and their complications. The potential role of non-harmful bacterial-derived products, according to the old hygiene hypothesis and the most recent trained-innate immunity concept, will be discussed together with the need of proof-of-concept studies and larger clinical trials with immunological and microbiological endpoints.

Kidney diseases and COVID-19 infection: causes and effect, supportive therapeutics and nutritional perspectives

Recently, the novel coronavirus disease 2019 (COVID-19), has attracted the attention of scientists where it has a high mortality rate among older adults and individuals suffering from chronic diseases, such as chronic kidney diseases (CKD). It is important to elucidate molecular mechanisms by which COVID-19 affects the kidneys and accordingly develop proper nutritional and pharmacological strategies. Although numerous studies have recently recommended several approaches for the management of COVID-19 in CKD, its impact on patients with renal diseases remains the biggest challenge worldwide. In this paper, we review the most recent evidence regarding causality, potential nutritional supplements, therapeutic options, and management of COVID-19 infection in vulnerable individuals and patients with CKD. To date, there is no effective treatment for COVID-19-induced kidney dysfunction, and current treatments are yet limited to anti-inflammatory (e.g. ibuprofen) and anti-viral medications (e.g. Remdesivir, and Chloroquine/Hydroxychloroquine) that may increase the chance of treatment. In conclusion, the knowledge about kidney damage in COVID-19 is very limited, and this review improves our ability to introduce novel approaches for future clinical trials for this contiguous disease.

The lung-gut axis during viral respiratory infections: the impact of gut dysbiosis on secondary disease outcomes

Bacteria that colonize the human gastrointestinal tract are essential for good health. The gut microbiota has a critical role in pulmonary immunity and host's defense against viral respiratory infections. The gut microbiota's composition and function can be profoundly affected in many disease settings, including acute infections, and these changes can aggravate the severity of the disease. Here, we discuss mechanisms by which the gut microbiota arms the lung to control viral respiratory infections. We summarize the impact of viral respiratory infections on the gut microbiota and discuss the potential mechanisms leading to alterations of gut microbiota's composition and functions. We also discuss the effects of gut microbial imbalance on disease outcomes, including gastrointestinal disorders and secondary bacterial infections. Lastly, we discuss the potential role of the lung-gut axis in coronavirus disease 2019.

Gut microbiota and aging

Aging is characterized by the functional decline of tissues and organs and increased risk of aging-associated disorders, which pose major societal challenges and are a public health priority. Despite extensive human genetics studies, limited progress has been made linking genetics with aging. There is a growing realization that the altered assembly, structure and dynamics of the gut microbiota actively participate in the aging process. Age-related microbial dysbiosis is involved in reshaping immune responses during aging, which manifest as immunosenescence (insufficiency) and inflammaging (over-reaction) that accompany many age-associated enteric and extraenteric diseases. The gut microbiota can be regulated, suggesting a potential target for aging interventions. This review summarizes recent findings on the physiological succession of gut microbiota across the life-cycle, the roles and mechanisms of gut microbiota in healthy aging, alterations of gut microbiota and aging-associated diseases, and the gut microbiota-targeted anti-aging strategies.

Gut microbial bile acid metabolite skews macrophage polarization and contributes to high-fat diet-induced colonic inflammation

High-fat diet (HFD) leads to systemic low-grade inflammation, which has been involved in the pathogenesis of diverse metabolic and inflammatory diseases. Colon is thought to be the first organ suffering from inflammation under HFD conditions due to the pro-inflammatory macrophages infiltration, however, the mechanisms concerning the induction of pro-inflammatory phenotype of colonic macrophages remains unclear. In this study, we show that HFD increased the percentage of gram-positive bacteria, especially genus Clostridium, and resulted in the significant increment of fecal deoxycholic acid (DCA), a gut microbial metabolite produced by bacteria mainly restricted to genus Clostridium. Notably, reducing gram-positive bacteria with vancomycin diminished fecal DCA and profoundly alleviated pro-inflammatory macrophage infiltration in colon, whereas DCA-supplemented feedings to vancomycin-treated mice provoked obvious pro-inflammatory macrophage infiltration and colonic inflammation. Meanwhile, intra-peritoneal administration of DCA also elicited considerable recruitment of macrophages with pro-inflammatory phenotype. Mechanistically, DCA dose-dependently promoted M1 macrophage polarization and pro-inflammatory cytokines production at least partially through toll-like receptor 2 (TLR2) transactivated by M2 muscarinic acetylcholine receptor (M2-mAchR)/Src pathway. In addition, M2-mAchR mediated increase of TLR2 transcription was mainly achieved via targeting AP-1 transcription factor. Moreover, NF-κB/ERK/JNK signalings downstream of TLR2 are involved in the DCA-induced macrophage polarization. In conclusion, our findings revealed that high level DCA induced by HFD may serve as an initiator to activate macrophages and drive colonic inflammation, thus offer a mechanistic basis that modulation of gut microbiota or intervening specific bile acid receptor signaling could be potential therapeutic approaches for HFD-related inflammatory diseases.

Fine Particulate Matter Exposure Alters Pulmonary Microbiota Composition and Aggravates Pneumococcus-Induced Lung Pathogenesis

Exposure to fine particulate matter (PM) with aerodynamic diameter ≤2.5 μm (PM2. 5) is closely correlated with respiratory diseases. Microbiota plays a key role in maintaining body homeostasis including regulation of host immune status and metabolism. As reported recently, PM2. 5 exposure causes microbiota dysbiosis and thus promotes disease progression. However, whether PM2. 5 alters pulmonary microbiota distribution and aggravates bacteria-induced pathogenesis remains unknown. In this study, we used mouse experimental models of PM2. 5 exposure combined with Streptococcus pneumonia infection. We characterized the airway microbiota of bronchoalveolar lavage fluid (BALF) by sequencing the 16S rRNA V3-V4 amplicon on the Illumina MiSeq platform, followed by a combination of bioinformatics and statistical analyses. Shannon-diversity index, observed ASVs, and Fisher's diversity index indicated that microbiota richness was significantly decreased in the mice treated with either PM2. 5 or pneumococcus when compared with the control group. The genera Streptococcus, Prevotella, Leptotrichia, and Granulicatella were remarkably increased in mice exposed to PM2. 5 combined with pneumococcal infection as compared to mice with pneumococcal infection alone. Histopathological examination exhibited that a more pronounced inflammation was present in lungs of mice treated with PM2. 5 and pneumococcus than that in mouse groups exposed to either PM2. 5 or pneumococcal infection alone. Our results demonstrate that PM2. 5 alters the microbiota composition, thereby enhancing susceptibility to pneumococcal infection and exacerbating lung pathogenesis.

A comprehensive analysis of the microbiota composition and gene expression in colorectal cancer

BACKGROUND

The dysregulation of gut microbiota is pivotal in colorectal carcinogenesis. Meanwhile, altered gut microbiome may affect the development of intestinal diseases through interaction with the host genes. However, the synergy between the altered gut microbiota composition and differential expression of specific genes in colorectal cancer (CRC) remains elusive. Thus, we integrated the data from 16S rRNA gene sequences and RNA sequences to investigate the potential relationship between genes and gut microbes in patients with CRC.

RESULTS

Compared with normal samples, the presence of Proteobacteria and Fusobacteria increased considerably in CRC samples; conversely, the abundance of Firmicutes and Spirochaetes decreased markedly. In particular, the genera Fusobacterium, Catenibacterium, and Shewanella were only detected in tumor samples. Meanwhile, a closely interaction between Butyricimonas and Clostridium was observed in the microbiome network. Furthermore, a total of 246 (differentially expressed genes) DEGs were identified between tumor and normal tissues. Both DEGs and microbiota were involved in bile secretion and steroid hormone biosynthesis pathways. Finally, genes like cytochrome P450 family 3 subfamily A member 4 (CYP3A4) and ATP binding cassette subfamily G member 2 (ABCG2) enriched in these two pathways were connected with the prognosis of CRC, and CRC patients with low expression level of CYP3A4 and ABCG2 had longer survival time.

CONCLUSION

Identifying the complicated interaction between gut microbiota and the DEGs contributed to further understand the pathogenesis of CRC, and these findings might enable better diagnosis and treatment of CRC patients.

Impact of Microbiota: A Paradigm for Evolving Herd Immunity against Viral Diseases

Herd immunity is the most critical and essential prophylactic intervention that delivers protection against infectious diseases at both the individual and community level. This process of natural vaccination is immensely pertinent to the current context of a pandemic caused by severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) infection around the globe. The conventional idea of herd immunity is based on efficient transmission of pathogens and developing natural immunity within a population. This is entirely encouraging while fighting against any disease in pandemic circumstances. A spatial community is occupied by people having variable resistance capacity against a pathogen. Protection efficacy against once very common diseases like smallpox, poliovirus or measles has been possible only because of either natural vaccination through contagious infections or expanded immunization programs among communities. This has led to achieving herd immunity in some cohorts. The microbiome plays an essential role in developing the body’s immune cells for the emerging competent vaccination process, ensuring herd immunity. Frequency of interaction among microbiota, metabolic nutrients and individual immunity preserve the degree of vaccine effectiveness against several pathogens. Microbiome symbiosis regulates pathogen transmissibility and the success of vaccination among different age groups. Imbalance of nutrients perturbs microbiota and abrogates immunity. Thus, a particular population can become vulnerable to the infection. Intestinal dysbiosis leads to environmental enteropathy (EE). As a consequence, the generation of herd immunity can either be delayed or not start in a particular cohort. Moreover, disparities of the protective response of many vaccines in developing countries outside of developed countries are due to inconsistencies of healthy microbiota among the individuals. We suggested that pan-India poliovirus vaccination program, capable of inducing herd immunity among communities for the last 30 years, may also influence the inception of natural course of heterologous immunity against SARS-CoV-2 infection. Nonetheless, this anamnestic recall is somewhat counterintuitive, as antibody generation against original antigens of SARS-CoV-2 will be subdued due to original antigenic sin.

Activation of aryl hydrocarbon receptor in Langerhans cells by a microbial metabolite of tryptophan negatively regulates skin inflammation

BACKGROUND

Skin commensal bacteria play important roles in skin homeostasis. Langerhans cells (LCs) are epidermis-resident dendritic cells that sense environmental stimuli and are critical in the induction of immune tolerance to allergen and bacterial skin flora. However, response of LCs to the metabolites of the skin microbiota is not clear.

OBJECTIVE

To explore the effects of the skin microbial metabolites on LCs activation.

METHODS

LCs derived from CD34+ hematopoietic stem cells in the cord blood were treated with a microbial metabolite of tryptophan, indole-3-aldehyde (IAId). Activation aryl hydrocarbon receptor (AhR) signaling, production of IL-10, and expression of receptor activator of NF-κB (RANK) / receptor activator of NF-κB ligand (RANKL) in LCs or keratinocytes were analyzed using quantitative PCR, western blotting and flow cytometry. LCs maturation induced by IAId and CD4⁺ T cell response induced by IAId-conditioned LCs were also investigated.

RESULTS

IAId induced the production of indoleamine 2,3-dioxygenase (IDO) and IL-10 in LCs through the activation of AhR. IAId promoted the expression of RANK and RANKL on LCs and keratinocytes in an AhR-dependent manner respectively, which might result in activation of NF-κB signaling and production of IL-10. Moreover, a mature phenotype of LCs was induced by IAId, and IAId-activated LCs inhibited CD4⁺ T cell proliferation and induced IL-10 secretion.

CONCLUSIONS

Our study revealed a negatively regulatory function of a tryptophan metabolite on LCs through the activation of AhR, and the microbial metabolites could be utilized in future treatment for inflammatory skin diseases.

Target Dysbiosis of Gut Microbes as a Future Therapeutic Manipulation in Alzheimer's Disease

Alzheimer’s disease (AD) is commonly an age-associated dementia with neurodegeneration. The pathogenesis of AD is complex and still remains unclear. The inflammation, amyloid β (Aβ), and neurofibrillary tangles as well misfolded tau protein in the brain may contribute to the occurrence and development of AD. Compared with tau protein, Aβ is less toxic. So far, all efforts made in the treatments of AD with targeting these pathogenic factors were unsuccessful over the past decades. Recently, many studies demonstrated that changes of the intestinal environment and gut microbiota via gut–brain axis pathway can cause neurological disorders, such as AD, which may be involved in the pathogenesis of AD. Thus, remodeling the gut microbiota by various ways to maintain their balance might be a novel therapeutic strategy for AD. In the review article, we analyzed the characteristics of gut microbiota and its dysbiosis in AD and its animal models and investigated the possibility of targeting the gut microbiota in the treatment of the patients with AD in the future.

Biomarkers of Physical Frailty and Sarcopenia: Coming up to the Place?

Physical frailty and sarcopenia (PF&S) recapitulates all the hallmarks of aging and has become a focus in geroscience. Factors spanning muscle-specific processes (e.g., mitochondrial dysfunction in skeletal myocytes) to systemic changes (e.g., inflammation and amino acid dysmetabolism) have been pinpointed as possible contributors to PF&S pathophysiology. However, the search for PF&S biomarkers allowing the early identification and tracking of the condition over time is ongoing. This is mainly due to the phenotypic heterogeneity of PF&S, its unclear pathophysiology, and the frequent superimposition of other age-related conditions. Hence, presently, the identification of PF&S relies upon clinical, functional, and imaging parameters. The adoption of multi-marker approaches (combined with multivariate modeling) has shown great potential for addressing the complexity of PF&S pathophysiology and identifying candidate biological markers. Well-designed longitudinal studies are necessary for the incorporation of reliable biomarkers into clinical practice and for unveiling novel targets that are amenable to interventions.

The surviving sepsis campaign: basic/translational science research priorities

Objectives

Expound upon priorities for basic/translational science identified in a recent paper by a group of experts assigned by the Society of Critical Care Medicine and the European Society of Intensive Care Medicine.

Data sources

Original paper, search of the literature.

Study selection

This study is selected by several members of the original task force with specific expertise in basic/translational science. Data extraction and data synthesis are not available.

Conclusions

In the first of a series of follow-up reports to the original paper, several members of the original task force with specific expertise provided a more in-depth analysis of the five identified priorities directly related to basic/translational science. This analysis expounds on what is known about the question and what was identified as priorities for ongoing research. It is hoped that this analysis will aid the development of future research initiatives.

The gut microbiome and frailty

The human microbiome is constituted by an extensive network of organisms that lie at the host/environment interface and transduce signals that play vital roles in human health and disease across the lifespan. Frailty is a critical aging-related syndrome marked by diminished physiological reserve and heightened vulnerability to stress, predictive of major adverse clinical outcomes including death. While recent studies suggest the microbiome may impact key pathways critical to frailty pathophysiology, direct evaluation of the microbiome-frailty relationship remains limited. In this article, we review the complex interplay of biological, behavioral, and environmental factors that may influence shifts in gut microbiome composition and function in aging populations and the putative implications of such shifts for progression to frailty. We discuss HIV infection as a key prototype for elucidating the complex pathways via which the microbiome may precipitate frailty. Finally, we review considerations for future research efforts.

Exogenous maltose enhances Zebrafish immunity to levofloxacin-resistant Vibrio alginolyticus

Understanding the interplay between bacterial fitness, antibiotic resistance, host immunity and host metabolism could guide treatment and improve immunity against antibiotic-resistant pathogens. The acquisition of levofloxacin (Lev) resistance affects the fitness of Vibrio alginolyticus in vitro and in vivo. Lev-resistant (Lev-R) V. alginolyticus exhibits slow growth, reduced pathogenicity and greater resistance to killing by the host, Danio rerio (zebrafish), than Lev-sensitive (Lev-S) V. alginolyticus, suggesting that Lev-R V. alginolyticus triggers a weaker innate immune response in D. rerio than Lev-S V. alginolyticus. Differences were detected in the metabolome of D. rerio infected with Lev-S or Lev-R V. alginolyticus. Maltose, a crucial metabolite, is significantly downregulated in D. rerio infected with Lev-R V. alginolyticus, and exogenous maltose enhances the immune response of D. rerio to Lev-R V. alginolyticus, leading to better clearance of the infection. Furthermore, we demonstrate that exogenous maltose stimulates the host production of lysozyme and its binding to Lev-R V. alginolyticus, which depends on bacterial membrane potential. We suggest that exogenous exposure to crucial metabolites could be an effective strategy for treating and/or managing infections with antibiotic-resistant bacteria.

Schizochytrium limacinum Supplementation in a Low Fish-Meal Diet Improved Immune Response and Intestinal Health of Juvenile Penaeus monodon

The aim of the present experiment was to evaluate the effects of Schizochytrium limacinum supplementation on the immune response, gut microbiota, and health of Penaeus monodon fed a low fish-meal (FM) diet. A diet containing 25% FM was used as a control (Diet A), and three other diets were formulated to contain 15% FM and supplemented with 0, 0.75, and 1.5% S. limacinum (Diet B, C, and D, respectively). The experiment was carried out in quadruplicates (30 shrimp per replicate, average weight 1.01 ± 0.01 g), and the shrimps were fed the test diets to apparent satiation three times daily for 8 weeks. Shrimp fed diet B and D showed lower weight gain than those fed diet A. Supplementation of 0.75% S. limacinum enhanced expression of antioxidative genes (superoxide dismutase and catalase) and immune-response-related genes in hepatopancreas but could not affect the gene expression of immune deficiency in hepatopancreas and Tube in the intestine. A low FM diet induced endoplasmic reticulum swelling of the intestinal epithelial cells, which was alleviated by S. limacinum supplementation. Ultra-performance liquid chromatography coupled with quadrupole time of flight mass spectrometry was employed to analyze the changes of hemolymph metabolomics, 49 significantly different metabolites were identified, and lysoPCs, deoxyinosine, inosine, and highly unsaturated fatty acids were lower in fish fed with low FM diets. Intestinal microbial diversity was lower in shrimp fed Diet B than those fed the control diet. Dietary supplementation of 0.75% S. limacinum increased intestinal microbial diversity of shrimp and decreased the ratio of pathogenic bacterium (Thalassotalea and Tenacibaculum). These results indicated that supplementing S. limacinum into a low FM diet improves the growth performance, immune response, and intestinal health of P. monodon. The optimum inclusion level of seems to be 0.75% of diet.

Interactions between host and gut microbiota in domestic pigs: a review

It is well established that pig gut microbiota plays a critical role in maintaining metabolic homeostasis as well as in a myriad of physiological, neurological and immunological functions; including protection from pathogens and digestion of food materials - some of which would be otherwise indigestible by the pig. A rich and diverse gut microbial ecosystem (balanced microbiota) is the hallmark of good health; while qualitative and quantitative perturbations in the microbial composition can lead to development of various diseases. Alternatively, diseases caused by stressors or other factors have been shown to negatively impact the microbiota. This review focuses primarily on how commensal microorganisms in the gastrointestinal tract of pigs influence biochemical, physiological, immunological, and metabolic processes within the host animal.

Effects of dietary vitamins supplementation level on the production performance and intestinal microbiota of aged laying hens

The objective of this study was to investigate the effects of higher vitamins supplementation level on the performance, immunity, and intestinal microbiota of old laying hens. Twelve birds were randomly chosen from 312 healthy, 65-wk-old Hy-Line Brown layers for sampling after a 7-wk acclimation period. The remaining 300 hens were randomly allocated to 1 of 4 dietary treatments for a 13-wk feeding trial: basal diet (CON), basal diet with 2-fold supplementation level of lipid-soluble vitamins (LV), 2-fold supplementation level of water-soluble vitamins (WV), or 2-fold supplementation level of both lipid-soluble and water-soluble vitamins (BV), respectively. Compared with 72-wk-old laying hens, the 85-wk-old laying hens showed declined egg quality, which implied by inferior eggshell strength and yolk color (P < 0.05). However, after 13 wks feeding trial, the birds in WV group had higher yellowness of yolk color, and LV group had increased laying rate (P < 0.05) compared with CON. Meanwhile, WV and/or BV groups showed improved GSH/GSSG levels in liver and increased secretory immunoglobulin A concentrations in jejunum compared with CON (P < 0.05). In addition, higher dietary vitamin supplementation levels significantly altered the composition of intestinal microbiota, as evidenced by increased abundance of ileal Lactobacillus, whereas reduced richness of ileal Romboutsia, Turicibacter, and cecal Faecalibacterium (P < 0.05) in WV group and increased cecal Megasphaera and Phascolarctobacterium (P < 0.05) in LV group compared with CON group. In conclusion, higher vitamin supplementation levels in the diet could improve laying performance and egg quality of aged hens, which was closely correlated with the increased abundance of beneficial microbiota in the intestine.

Healthy Human Gastrointestinal Microbiome: Composition and Function After a Decade of Exploration

The human gastrointestinal (GI) tract contains communities of microbes (bacteria, fungi, viruses) that vary by anatomic location and impact human health. Microbial communities differ in composition based on age, diet, and location in the gastrointestinal tract. Differences in microbial composition have been associated with chronic disease states. In terms of function, microbial metabolites provide key signals that help maintain healthy human physiology. Alterations of the healthy gastrointestinal microbiome have been linked to the development of various disease states including inflammatory bowel disease, diabetes, and colorectal cancer. While the definition of a healthy GI microbiome cannot be precisely identified, features of a healthy gut microbiome include relatively greater biodiversity and relative abundances of specific phyla and genera. Microbes with desirable functional profiles for the human host have been identified, in addition to specific metabolic features of the microbiome. This article reviews the composition and function of the healthy human GI microbiome, including the relative abundances of different bacterial taxa and the specific metabolic pathways and classes of microbial metabolites contributing to human health and disease prevention.

Twin-Arginine Translocation System Is Involved in Citrobacter rodentium Fitness in the Intestinal Tract

The twin-arginine translocation (Tat) system is involved in not only a wide array of cellular processes but also pathogenesis in many bacterial pathogens; thus, this system is expected to become a novel therapeutic target to treat infections. To the best of our knowledge, involvement of the Tat system has not been reported in the gut infection caused by Citrobacter rodentium Here, we studied the role of Tat in C. rodentium gut infection, which resembles human infection with enterohemorrhagic Escherichia coli (EHEC) and enteropathogenic E. coli (EPEC). A C. rodentium Tat loss-of-function mutant displayed prolonged gut colonization, which was explained by reduced inflammatory responses and, particularly, neutrophil infiltration. Further, the Tat mutant had colonization defects upon coinfection with the wild-type strain of C. rodentium The Tat mutant also became hypersensitive to bile acids, and an increase in fecal bile acids fostered C. rodentium clearance from the gut lumen. Finally, we show that the chain form of C. rodentium cells, induced by a Tat-dependent cell division defect, exhibits impaired resistance to bile acids. Our findings indicate that the Tat system is involved in gut colonization by C. rodentium, which is associated with neutrophil infiltration and resistance to bile acids. Interventions that target the Tat system, as well as luminal bile acids, might thus be promising therapeutic strategies to treat human EHEC and EPEC infections.

Nutritional Status as a Mediator of Fatigue and Its Underlying Mechanisms in Older People

Fatigue is an often-neglected symptom but frequently complained of by older people, leading to the inability to continue functioning at a normal level of activity. Fatigue is frequently associated with disease conditions and impacts health status and quality of life. Yet, fatigue cannot generally be completely explained as a consequence of a single disease or pathogenetic mechanism. Indeed, fatigue mirrors the exhaustion of the physiological reserves of an older individual. Despite its clinical relevance, fatigue is typically underestimated by healthcare professionals, mainly because reduced stamina is considered to be an unavoidable corollary of aging. The incomplete knowledge of pathophysiological mechanisms of fatigue and the lack of a gold standard tool for its assessment contribute to the poor appreciation of fatigue in clinical practice. Inadequate nutrition is invoked as one of the mechanisms underlying fatigue. Modifications in food intake and body composition changes seem to influence the perception of fatigue, probably through the mechanisms of inflammation and/or mitochondrial dysfunction. Here, we present an overview on the mechanisms that may mediate fatigue levels in old age, with a special focus on nutrition.

Dysbiosis of gut microbiome affecting small intestine morphology and immune balance: a rhesus macaque model

There is a growing appreciation for the specific health benefits conferred by commensal microbiota on their hosts. Clinical microbiota analysis and animal studies in germ-free or antibiotic-treated mice have been crucial for improving our understanding of the role of the microbiome on the host mucosal surface; however, studies on the mechanisms involved in microbiome-host interactions remain limited to small animal models. Here, we demonstrated that rhesus monkeys under short-term broad-spectrum antibiotic treatment could be used as a model to study the gut mucosal host-microbiome niche and immune balance with steady health status. Results showed that the diversity and community structure of the gut commensal bacteria in rhesus monkeys were both disrupted after antibiotic treatment. Furthermore, the 16S rDNA amplicon sequencing results indicated that Escherichia-Shigella were predominant in stool samples 9 d of treatment, and the abundances of bacterial functional genes and predicted KEGG pathways were significantly changed. In addition to inducing aberrant morphology of small intestinal villi, the depletion of gut commensal bacteria led to increased proportions of CD3 ⁺ T, CD4 ⁺ T, and CD16 ⁺ NK cells in peripheral blood mononuclear cells (PBMCs), but decreased numbers of Treg and CD20 ⁺ B cells. The transcriptome of PBMCs from antibiotic-treated monkeys showed that the immune balance was affected by modulation of the expression of many functional genes, including IL-13, VCAM1, and LGR4.

Gut Microbiota and Immune Responses

The gut microbiota consists of a dynamic multispecies community living within a particular niche in a mutual synergy with the host organism. Recent findings have revealed roles for the gut microbiota in the modulation of host immunity and the development and progression of immune-mediated diseases. Besides, growing evidence supports the concept that some metabolites mainly originated from gut microbiota are linked to the immune regulation implicated in systemic inflammatory and autoimmune disorders. In this chapter, we describe the recent advances in our understanding of how host-microbiota interactions shape the immune system, how they affect the pathogenesis of immune-associated diseases and the impact of these mechanisms in the efficacy of disease therapy.

Tryptophan metabolism as a common therapeutic target in cancer, neurodegeneration and beyond

L-Tryptophan (Trp) metabolism through the kynurenine pathway (KP) is involved in the regulation of immunity, neuronal function and intestinal homeostasis. Imbalances in Trp metabolism in disorders ranging from cancer to neurodegenerative disease have stimulated interest in therapeutically targeting the KP, particularly the main rate-limiting enzymes indoleamine-2,3-dioxygenase 1 (IDO1), IDO2 and tryptophan-2,3-dioxygenase (TDO) as well as kynurenine monooxygenase (KMO). However, although small-molecule IDO1 inhibitors showed promise in early-stage cancer immunotherapy clinical trials, a phase III trial was negative. This Review summarizes the physiological and pathophysiological roles of Trp metabolism, highlighting the vast opportunities and challenges for drug development in multiple diseases.

Efficacy of Nutritional Interventions as Stand-Alone or Synergistic Treatments with Exercise for the Management of Sarcopenia

Sarcopenia is an age-related and accelerated process characterized by a progressive loss of muscle mass and strength/function. It is a multifactorial process associated with several adverse outcomes including falls, frailty, functional decline, hospitalization, and mortality. Hence, sarcopenia represents a major public health problem and has become the focus of intense research. Unfortunately, no pharmacological treatments are yet available to prevent or treat this age-related condition. At present, the only strategies for the management of sarcopenia are mainly based on nutritional and physical exercise interventions. The purpose of this review is, thus, to provide an overview on the role of proteins and other key nutrients, alone or in combination with physical exercise, on muscle parameters.

Gut microbiota and physical frailty through the mediation of sarcopenia

The changing physiology and lifestyle of older people affect the gut microbiota composition. In particular, the age-related diet modifications can alter the gut microbiota biodiversity and determine the relative abundance of specific microbial taxa, resulting in microbiota dysbiosis with negative consequences for the host physiology. Unhealthy microbiota may then induce an acceleration of the age-related physiological changes, consequently concurring at determining the characteristic complexity of frail older persons. One of the major clinical manifestations of frailty is represented by the individual's physical decline. Besides of a well-established clinical phenotype of frailty, the qualitative and quantitative skeletal muscle impairment (i.e., sarcopenia) is today of particular interest for potentially serving as target for (pharmacological and non-pharmacological) interventions to prevent incident disability. Evidence suggests that gut microbiota is able to influence the skeletal muscle homeostasis via microbiota-dependent metabolites, thus representing the possible biological substratum for the sarcopenia onset. In fact, the rearrangements of gut microbiota as well as the alteration of its functions contribute at increasing the anabolic resistance, releasing pro-inflammatory mediators, determining mitochondrial abnormalities with consequent oxidation, and causing insulin resistance. In this article, the link between gut microbiota and physical frailty is discussed. It is especially explained the role that sarcopenia may play in this likely bidirectional relationship.

Fecal Microbial Transplantation and Its Potential Application in Cardiometabolic Syndrome

Newly revealed links between inflammation, obesity, and cardiometabolic syndrome have created opportunities to try previously unexplored therapeutic modalities in these common and life-risking disorders. One potential modulator of these complex disorders is the gut microbiome, which was described in recent years to be altered in patients suffering from features of cardiometabolic syndrome and to transmit cardiometabolic phenotypes upon transfer into germ-free mice. As a result, there is great interest in developing new modalities targeting the altered commensal bacteria as a means of treatment for cardiometabolic syndrome. Fecal microbiota transplantation (FMT) is one such modality in which a disease-associated microbiome is replaced by a healthy microbiome configuration. So far clinical use of FMT has been overwhelmingly successful in recurrent Clostridium difficile infection and is being extensively studied in other microbiome-associated pathologies such as cardiometabolic syndrome. This review will focus on the rationale, promises and challenges in FMT utilization in human disease. In particular, it will overview the role of the gut microbiota in cardiometabolic syndrome and the rationale, experience, and prospects of utilizing FMT treatment as a potential preventive and curative treatment of metabolic human disease.

Workshop Report: Modulation of Antitumor Immune Responses by Dietary and Microbial Metabolites

The human microbiota maintains an enormous and diverse capacity to produce a diet-dependent metabolome that impacts both host tissue and microbial community homeostasis. Recent discoveries support a growing appreciation that microbial metabolites derived from bioactive foods are also important regulators of host immune and metabolic functions. To gain a better understanding of the current evidence for the roles of dietary and microbial metabolites in tumor immunity, the Division of Cancer Biology and the Division of Cancer Prevention, National Cancer Institute, cosponsored a workshop on August 31 and September 1, 2016, in Bethesda, Maryland. Workshop participants examined several lines of converging science that link nutrition, microbiology, and tumor immunology and identified key concepts and research opportunities that will accelerate our understanding of these interactions. In addition, the participants identified some of the critical gaps and research challenges that could be addressed through interdisciplinary collaborations, including future opportunities for translating new information into novel cancer prevention and treatment strategies based on targeting host immune functions that are altered by metabolite sensing pathways.

The Unique Lifestyle of Crohn's Disease-Associated Adherent-Invasive Escherichia coli

Escherichia coli is one of the most genetically and phenotypically diverse species of bacteria. This remarkable diversity produces a plethora of clinical outcomes following infection and has informed much of what we currently know about host-pathogen interactions for a wide range of bacteria-host relationships. In studying the role of microbes in disease, adherent-invasive E. coli (AIEC) has emerged as having a strong association with Crohn's disease (CD). Thus, there has been an equally strong effort to uncover the root origins of AIEC, to appreciate how AIEC differs from other well-known pathogenic E. coli variants, and to understand its connection to disease. Emerging from a growing body of research on AIEC is the understanding that AIEC itself is remarkably diverse, both in phylogenetic origins, genetic makeup, and behavior in the host setting. Here, we describe the unique lifestyle of CD-associated AIEC and review recent research that is uncovering the inextricable link between AIEC and its host in the context of CD.

Sex Differences in Older Adults' Immune Responses to Seasonal Influenza Vaccination

Background: Sex differences in immune responses to influenza vaccine may impact efficacy across populations. Methods: In a cohort of 138 older adults (50-74 years old), we measured influenza A/H1N1 antibody titers, B-cell ELISPOT response, PBMC transcriptomics, and PBMC cell compositions at 0, 3, and 28 days post-immunization with the 2010/11 seasonal inactivated influenza vaccine. Results: We identified higher B-cell ELISPOT responses in females than males. Potential mechanisms for sex effects were identified in four gene clusters related to T, NK, and B cells. Mediation analysis indicated that sex-dependent expression in T and NK cell genes can be partially attributed to higher CD4+ T cell and lower NK cell fractions in females. We identified strong sex effects in 135 B cell genes whose expression correlates with ELISPOT measures, and found that cell subset differences did not explain the effect of sex on these genes' expression. Post-vaccination expression of these genes, however, mediated 41% of the sex effect on ELISPOT responses. Conclusions: These results improve our understanding of sexual dimorphism in immunity and influenza vaccine response.

Elevated Gut Microbiome-Derived Propionate Levels Are Associated With Reduced Sterile Lung Inflammation and Bacterial Immunity in Mice

Short-chain fatty acids (SCFA) are important dietary and microbiome metabolites that can have roles in gut immunity as well as further afield. We previously observed that gut microbiome alteration via antibiotics led to attenuated lung inflammatory responses. The rationale for this study was to identify gut microbiome factors that regulate lung immune homeostasis. We first investigated key factors within mouse colonic lumen filtrates (CLF) which could elicit direct inflammatory effects in vitro. We identified lipopolysaccharide (LPS) and SCFAs as key CLF ingredients whose levels and inflammatory capacity changed after antibiotic exposure in mice. Specifically, the SCFA propionate appeared to be a key regulator of LPS responses in vitro. Elevated propionate: acetate ratios, as seen in CLF after antibiotic exposure, strongly blunted inflammatory responses in vitro. In vivo, exposure of lungs to high dose propionate, to mimic how prior antibiotic exposure changed SCFA levels, resulted in diminished immune containment of Staphylococcus aureus pneumonia. Finally, we discovered an enrichment of propionate-producing gut bacteria in mice with reduced lung inflammation following lung ischemia reperfusion injury in vivo. Overall, our data show that propionate levels can distinctly modulate lung immune responses in vitro and in vivo and that gut microbiome increased production of propionate is associated with reduced lung inflammation.

High-dimensional single-cell proteomics analysis identifies immune checkpoint signatures and therapeutic targets in ulcerative colitis

Immune checkpoints are regulators of immune cells and play key roles in the modulation of immune responses. The role of checkpoints in autoimmune disease is poorly understood but likely to be central since checkpoint inhibition during cancer treatment can cause autoimmunity. We generated a high-dimensional single-cell proteomics data set from PBMCs of healthy individuals and patients with ulcerative colitis (UC) by mass cytometry, enabling systems-wide analyses of immune cell frequencies and cell type-specific expression patterns of 12 immune checkpoints. Subtle but significant changes in immune cell frequencies and checkpoint expression were observed between UC patients on different treatment regimens and between patients and healthy controls. Most strikingly, UC patients showed a reduced number of peripheral NK-cells and those cells showed an altered phenotype including increased TIGIT expression. Based on these results, we modulated NK-cell function ex vivo through targeting of TIGIT pathway members. In summary, we describe a pattern of changes in immune cell abundance and checkpoint expression as a basis for UC patient stratification and we show modulation of a corresponding immune cell subset through checkpoint targeting. Our approach can be used for the identification of pathogenic immune cell subsets and guide target selection in autoimmunity and chronic inflammation.

Altered bile acid profile associates with cognitive impairment in Alzheimer's disease-An emerging role for gut microbiome

INTRODUCTION

Increasing evidence suggests a role for the gut microbiome in central nervous system disorders and a specific role for the gut-brain axis in neurodegeneration. Bile acids (BAs), products of cholesterol metabolism and clearance, are produced in the liver and are further metabolized by gut bacteria. They have major regulatory and signaling functions and seem dysregulated in Alzheimer's disease (AD).

METHODS

Serum levels of 15 primary and secondary BAs and their conjugated forms were measured in 1464 subjects including 370 cognitively normal older adults, 284 with early mild cognitive impairment, 505 with late mild cognitive impairment, and 305 AD cases enrolled in the AD Neuroimaging Initiative. We assessed associations of BA profiles including selected ratios with diagnosis, cognition, and AD-related genetic variants, adjusting for confounders and multiple testing.

RESULTS

In AD compared to cognitively normal older adults, we observed significantly lower serum concentrations of a primary BA (cholic acid [CA]) and increased levels of the bacterially produced, secondary BA, deoxycholic acid, and its glycine and taurine conjugated forms. An increased ratio of deoxycholic acid:CA, which reflects 7α-dehydroxylation of CA by gut bacteria, strongly associated with cognitive decline, a finding replicated in serum and brain samples in the Rush Religious Orders and Memory and Aging Project. Several genetic variants in immune response-related genes implicated in AD showed associations with BA profiles.

DISCUSSION

We report for the first time an association between altered BA profile, genetic variants implicated in AD, and cognitive changes in disease using a large multicenter study. These findings warrant further investigation of gut dysbiosis and possible role of gut-liver-brain axis in the pathogenesis of AD.

The protective roles of NLRP6 in intestinal epithelial cells

The evolution of chronic inflammatory diseases is thought to be due to a combination of host genetic variations and environmental factors that include the alteration of intestinal flora, termed "dysbiosis." The intestinal mucosal barrier includes a chemical barrier and physical barrier that have important roles in protecting the intestine against inflammatory injury. The chemical barrier includes antimicrobial peptides (AMPs), and the physical barrier includes a mucous layer, a monolayer of intestinal epithelial cells and cell junctions. The intestinal mucosal barrier is not a static barrier, but rather, it strongly interacts with the gut microbiome and cells of the immune system. Correct expression of AMPs, together with mucus and balanced epithelial cell proliferation, prevents the occurrence of disease. NLRP6, a member of the nucleotide-binding domain, leucine-rich repeat-containing (NLR) innate immune receptor family, participates in the progression of intestinal inflammation and enteric pathogen infections. It has become apparent in recent years that NLRP6 is important in disease pathogenesis, as it responds to internal ligands that lead to the release of AMPs and mucus, thus regulating the regeneration of intestinal epithelial cells. This review summarizes the activation of NLRP6 and its protective role in the intestinal epithelial cell.

Inflammation-Accelerated Senescence and the Cardiovascular System: Mechanisms and Perspectives

Low-grade chronic inflammation is a common denominator in atherogenesis and related diseases. Solid evidence supports the occurrence of an impairment in the innate and adaptive immune system with senescence, favoring the development of acute and chronic age-related diseases. Cardiovascular (CV) diseases (CVD), in particular, are a leading cause of death even at older ages. Inflammation-associated mechanisms that contribute to CVD development include dysregulated redox and metabolic pathways, genetic modifications, and infections/dysbiosis. In this review, we will recapitulate the determinants and consequences of the immune system dysfunction at older age, with particular focus on the CV system. We will examine the currently available and potential future strategies to counteract accelerated CV aging, i.e., nutraceuticals, probiotics, caloric restriction, physical activity, smoking and alcohol cessation, control of low-grade inflammation sources, senolytic and senescence-modulating drugs, and DNA-targeting drugs.

Microbiome modulates intestinal homeostasis against inflammatory diseases

Eliminating prophylactic antibiotics in food animal production has exerted pressure on discovering antimicrobial alternatives (e.g. microbiome) to reduce elevated intestinal diseases. Intestinal tract is a complex ecosystem coupling host cells with microbiota. The microbiota and its metabolic activities and products are collectively called microbiome. Intestinal homeostasis is reached through dynamic and delicate crosstalk between host immunity and microbiome. However, this balance can be occasionally broken, which results in intestinal inflammatory diseases such as human Inflammatory Bowel Diseases, chicken necrotic enteritis, and swine postweaning diarrhea. In this review, we introduce the intestinal immune system, intestinal microbiome, and microbiome modulation of inflammation against intestinal diseases. The purpose of this review is to provide updated knowledge on host-microbe interaction and to promote using microbiome as new antimicrobial strategies to reduce intestinal diseases.

The mammalian mycobiome: A complex system in a dynamic relationship with the host

Mammalian barrier surfaces are densely populated by symbiont fungi in much the same way the former are colonized by symbiont bacteria. The fungal microbiota, otherwise known as the mycobiota, is increasingly recognized as a critical player in the maintenance of health and homeostasis of the host. Here we discuss the impact of the mycobiota on host physiology and disease, the factors influencing mycobiota composition, and the current technologies used for identifying symbiont fungal species. Understanding the tripartite interactions among the host, mycobiota, and other members of the microbiota, will help to guide the development of novel prevention and therapeutic strategies for a variety of human diseases.

This article is categorized under:

Physiology > Mammalian Physiology in Health and Disease

Laboratory Methods and Technologies > Genetic/Genomic Methods

Models of Systems Properties and Processes > Organismal Models

Evidence-based nutritional and pharmacological interventions targeting chronic low-grade inflammation in middle-age and older adults: A systematic review and meta-analysis

Growing evidence suggests chronic low-grade inflammation (LGI) as a possible mechanism underlying the aging process. Some biological and pharmaceutical compounds may reduce systemic inflammation and potentially avert functional decline occurring with aging. The aim of the present meta-analysis was to examine the association of pre-selected interventions on two established biomarkers of inflammation, interleukin-6 (IL-6), and C-reactive protein (CRP) in middle-age and older adults with chronic LGI. We reviewed the literature on potential anti-inflammatory compounds, selecting them based on safety, tolerability, acceptability, innovation, affordability, and evidence from randomized controlled trials. Six compounds met all five inclusion criteria for our systematic review and meta-analysis: angiotensin II receptor blockers (ARBs), metformin, omega-3, probiotics, resveratrol and vitamin D. We searched in MEDLINE, PubMed and EMBASE database until January 2017. A total of 49 articles fulfilled the selection criteria. Effect size of each study and pooled effect size for each compound were measured by the standardized mean difference. I² was computed to measure heterogeneity of effects across studies. The following compounds showed a significant small to large effect in reducing IL-6 levels: probiotics (-0.68 pg/ml), ARBs (-0.37 pg/ml) and omega-3 (-0.19 pg/ml). For CRP, a significant small to medium effect was observed with probiotics (-0.43 mg/L), ARBs (-0.2 mg/L), omega-3 (-0.17 mg/L) and metformin (-0.16 mg/L). Resveratrol and vitamin D were not associated with any significant reductions in either biomarker. These results suggest that nutritional and pharmaceutical compounds can significantly reduce established biomarkers of systemic inflammation in middle-age and older adults. The findings should be interpreted with caution, however, due to the evidence of heterogeneity across the studies.

Inflammageing: chronic inflammation in ageing, cardiovascular disease, and frailty

Most older individuals develop inflammageing, a condition characterized by elevated levels of blood inflammatory markers that carries high susceptibility to chronic morbidity, disability, frailty, and premature death. Potential mechanisms of inflammageing include genetic susceptibility, central obesity, increased gut permeability, changes to microbiota composition, cellular senescence, NLRP3 inflammasome activation, oxidative stress caused by dysfunctional mitochondria, immune cell dysregulation, and chronic infections. Inflammageing is a risk factor for cardiovascular diseases (CVDs), and clinical trials suggest that this association is causal. Inflammageing is also a risk factor for chronic kidney disease, diabetes mellitus, cancer, depression, dementia, and sarcopenia, but whether modulating inflammation beneficially affects the clinical course of non-CVD health problems is controversial. This uncertainty is an important issue to address because older patients with CVD are often affected by multimorbidity and frailty - which affect clinical manifestations, prognosis, and response to treatment - and are associated with inflammation by mechanisms similar to those in CVD. The hypothesis that inflammation affects CVD, multimorbidity, and frailty by inhibiting growth factors, increasing catabolism, and interfering with homeostatic signalling is supported by mechanistic studies but requires confirmation in humans. Whether early modulation of inflammageing prevents or delays the onset of cardiovascular frailty should be tested in clinical trials.