Integrative analysis of gut microbiota composition, host colonic gene expression and intraluminal metabolites in aging C57BL/6J mice

The role of circulating metabolites and gut microbiome in hypertrophic scar: a two-sample Mendelian randomization study

Hypertrophic scarring is a fibro-proliferative disorder caused by abnormal cutaneous wound healing. Circulating metabolites and the gut microbiome may be involved in the formation of these scars, but high-quality evidence of causality is lacking. To assess whether circulating metabolites and the gut microbiome contain genetically predicted modifiable risk factors for hypertrophic scar formation. Two-sample Mendelian randomization (MR) was performed using MR-Egger, inverse-variance weighting (IVW), Mendelian Randomization Pleiotropy RESidual Sum and Outlier, maximum likelihood, and weighted median methods. Based on the genome-wide significance level, genetically predicted uridine (P = 0.015, odds ratio [OR] = 1903.514, 95% confidence interval [CI] 4.280-846,616.433) and isovalerylcarnitine (P = 0.039, OR = 7.765, 95% CI 1.106-54.512) were positively correlated with hypertrophic scar risk, while N-acetylalanine (P = 0.013, OR = 7.98E-10, 95% CI 5.19E-17-0.012) and glycochenodeoxycholate (P = 0.021, OR = 0.021 95% CI 0.003-0.628) were negatively correlated. Gastranaerophilales and two unknown gut microbe species (P = 0.031, OR = 0.378, 95% CI 0.156-0.914) were associated with an decreased risk of hypertrophic scarring. Circulating metabolites and gut microbiome components may have either positive or negative causal effects on hypertrophic scar formation. The study provides new insights into strategies for diagnosing and limiting hypertrophic scarring.

Evidence that the loss of colonic anti-microbial peptides may promote dysbiotic Gram-negative inflammaging-associated bacteria in aging mice

Introduction: Aging studies in humans and mice have played a key role in understanding the intestinal microbiome and an increased abundance of "inflammaging" Gram-negative (Gn) bacteria. The mechanisms underlying this inflammatory profile in the aging microbiome are unknown. We tested the hypothesis that an aging-related decrease in colonic crypt epithelial cell anti-microbial peptide (AMP) gene expression could promote colonic microbiome inflammatory Gn dysbiosis and inflammaging. Methods: As a model of aging, C57BL/6J mice fecal (colonic) microbiota (16S) and isolated colonic crypt epithelial cell gene expression (RNA-seq) were assessed at 2 months (mth) (human: 18 years old; yo), 15 mth (human: 50 yo), and 25 mth (human: 84 yo). Informatics examined aging-related microbial compositions, differential colonic crypt epithelial cell gene expressions, and correlations between colonic bacteria and colonic crypt epithelial cell gene expressions. Results: Fecal microbiota exhibited significantly increased relative abundances of pro-inflammatory Gn bacteria with aging. Colonic crypt epithelial cell gene expression analysis showed significant age-related downregulation of key AMP genes that repress the growth of Gn bacteria. The aging-related decrease in AMP gene expressions is significantly correlated with an increased abundance in Gn bacteria (dysbiosis), loss of colonic barrier gene expression, and senescence- and inflammation-related gene expression. Conclusion: This study supports the proposed model that aging-related loss of colonic crypt epithelial cell AMP gene expression promotes increased relative abundances of Gn inflammaging-associated bacteria and gene expression markers of colonic inflammaging. These data may support new targets for aging-related therapies based on intestinal genes and microbiomes.

Association between Dysbiosis in the Gut Microbiota of Primary Osteoporosis Patients and Bone Loss

In recent decades, gut microbiome research has experienced significant growth, driven by technological advances that enable quantifying bacterial taxa with greater precision. Age, diet, and living environment have emerged as three key factors influencing gut microbes. Dysbiosis, resulting from alterations in these factors, may lead to changes in bacterial metabolites that regulate pro- and anti-inflammatory processes and consequently impact bone health. Restoration of a healthy microbiome signature could mitigate inflammation and potentially reduce bone loss associated with osteoporosis or experienced by astronauts during spaceflight. However, current research is hindered by contradictory findings, insufficient sample sizes, and inconsistency in experimental conditions and controls. Despite progress in sequencing technology, defining a healthy gut microbiome across global populations remains elusive. Challenges persist in identifying accurate gut bacterial metabolics, specific taxa, and their effects on host physiology. We suggest greater attention be directed towards this issue in Western countries as the cost of treating osteoporosis in the United States reaches billions of dollars annually, with expenses projected to continue rising.

Dietary restriction mitigates the age-associated decline in mouse B cell receptor repertoire diversity

Aging impairs the capacity to respond to novel antigens, reducing immune protection against pathogens and vaccine efficacy. Dietary restriction (DR) extends life- and health span in diverse animals. However, little is known about the capacity of DR to combat the decline in immune function. Here, we study the changes in B cell receptor (BCR) repertoire during aging in DR and control mice. By sequencing the variable region of the BCR heavy chain in the spleen, we show that DR preserves diversity and attenuates the increase in clonal expansions throughout aging. Remarkably, mice starting DR in mid-life have repertoire diversity and clonal expansion rates indistinguishable from chronic DR mice. In contrast, in the intestine, these traits are unaffected by either age or DR. Reduced within-individual B cell repertoire diversity and increased clonal expansions are correlated with higher morbidity, suggesting a potential contribution of B cell repertoire dynamics to health during aging.

Akkermansia muciniphila, which is enriched in the gut microbiota by metformin, improves cognitive function in aged mice by reducing the proinflammatory cytokine interleukin-6

BACKGROUND

Metformin, a type 2 diabetes treatment, improves the cognitive function of aged mice; however, whether the protective effects of metformin on cognitive function in aged mice are associated with the gut microbiome is poorly understood. Although some studies suggest that the gut microbe composition influences cognitive function and that manipulating the gut microbiota might protect against age-related cognitive dysfunction, there is no direct evidence to validate that the gut microbiota mediates the effect of metformin on cognitive improvement.

RESULTS

In this study, we show that the gut microbiota is altered by metformin, which is necessary for protection against ageing-associated cognitive function declines in aged mice. Mice treated with antibiotics did not exhibit metformin-mediated cognitive function protection. Moreover, treatment with Akkermansia muciniphila, which is enriched by metformin, improved cognitive function in aged mice. Mechanistically, A. muciniphila decreased pro-inflammatory-associated pathways, particularly that of the pro-inflammatory cytokine interleukin (IL)-6, in both the peripheral blood and hippocampal profiles, which was correlated with cognitive function improvement. An IL-6 antibody protected cognitive function, and an IL-6 recombinant protein abolished the protective effect of A. muciniphila on cognitive function in aged mice.

CONCLUSION

This study reveals that A. muciniphila, which is mediated in the gut microbiota by metformin, modulates inflammation-related pathways in the host and improves cognitive function in aged mice by reducing the pro-inflammatory cytokine IL-6. Video Abstract.

Alterations of the gut microbiome and metabolic profile in CVB3-induced mice acute viral myocarditis

BACKGROUND

Acute viral myocarditis (AVMC) is an inflammatory disease of the myocardium. Evidence indicates that dysbiosis of gut microbiome and related metabolites intimately associated with cardiovascular diseases through the gut-heart axis.

METHODS

We built mouse models of AVMC, then applied 16 S rDNA gene sequencing and UPLC-MS/MS metabolomics to explore variations of gut microbiome and disturbances of cardiac metabolic profiles.

RESULTS

Compared with Control group, analysis of gut microbiota showed lower diversity in AVMC, decreased relative abundance of genera mainly belonging to the phyla Bacteroidetes, and increased of phyla Proteobacteria. Metabolomics analysis showed disturbances of cardiac metabolomics, including 62 increased and 84 decreased metabolites, and mainly assigned to lipid, amino acid, carbohydrate and nucleotide metabolism. The steroid hormone biosynthesis, cortisol synthesis and secretion pathway were particularly enriched in AVMC. Among them, such as estrone 3-sulfate, desoxycortone positively correlated with disturbed gut microbiome.

CONCLUSION

In summary, both the structure of the gut microbiome community and the cardiac metabolome were significantly changed in AVMC. Our findings suggest that gut microbiome may participate in the development of AVMC, the mechanism may be related to its role in dysregulated metabolites such as steroid hormone biosynthesis.

Fall of PARP3 restrains Lgr5+ intestinal stem cells proliferation and mucosal renovation in intestinal aging

The regeneration ability of intestinal epithelium is degenerated in aging. The determining factor is leucine-rich repeat-containing G-protein-coupled receptor 5-positive intestinal stem cells (Lgr5⁺ ISCs). Lgr5-EGFP (enhanced green fluorescence protein) knock-in in transgenic mice at three different ages (young group: 3-6 months; middle group: 12-14 months; old group: 22-24 months) were used to examined Lgr5⁺ ISCs at three different timepoints. The jejunum samples were collected for histology, immunofluorescence analysis, western blotting and PCR. In tissue, crypt depth, proliferating cells and Lgr5⁺ ISC numbers were increased in the middle group (12-14 months) and decreased in the old group (22-24 months). The number of proliferating Lgr5⁺ ISCs gradually decreased as the mice aged. In organoids, the budding number, projected area, and Lgr5⁺ ISC ratio decreased as the mice aged. The gene expression of poly (ADP-ribose) polymerase 3 (Parp3) and the protein expression of PARP3 were increased in the middle- and old-aged groups. PARP3 inhibitors slowed organoid growth in the middle group. In conclusion, PARP3 is upregulated in aging, and the inhibition of PARP3 reduces the proliferation of aging Lgr5⁺ ISCs.

The gut microbiota is an emerging target for improving brain health during ageing

The gut microbiota plays crucial roles in maintaining the health and homeostasis of its host throughout lifespan, including through its ability to impact brain function and regulate behaviour during ageing. Studies have shown that there are disparate rates of biologic ageing despite equivalencies in chronologic age, including in the development of neurodegenerative diseases, which suggests that environmental factors may play an important role in determining health outcomes in ageing. Recent evidence demonstrates that the gut microbiota may be a potential novel target to ameliorate symptoms of brain ageing and promote healthy cognition. This review highlights the current knowledge around the relationships between the gut microbiota and host brain ageing, including potential contributions to age-related neurodegenerative diseases. Furthermore, we assess key areas for which gut microbiota-based strategies may present as opportunities for intervention.

Gut microbiota and metabonomics used to explore the mechanism of Qing'e Pills in alleviating osteoporosis

CONTEXT

The traditional Chinese medicine Qing'e Pills (QEP) has been used to treat postmenopausal osteoporosis (PMO).

OBJECTIVE

We evaluated the regulatory effects of QEP on gut microbiota in osteoporosis.

MATERIALS AND METHODS

Eighteen female SD rats were divided into three groups: sham surgery (SHAM), ovariectomized (OVX) and ovariectomized treated with QEP (OVX + QEP). Six weeks after ovariectomy, QEP was administered to OVX + QEP rats for eight weeks (4.5 g/kg/day, i.g.). After 14 weeks, the bone microstructure was evaluated. Differences in gut microbiota were analysed via 16S rRNA gene sequencing. Changes in endogenous metabolites were studied using UHPLC-Q-TOF/MS technology. GC-MS was used to detect short-chain fatty acids. Furthermore, we measured serum inflammatory factors, such as IL-6, TNF-α and IFN-γ, which may be related to gut microbiota.

RESULTS

OVX + QEP exhibited increased bone mineral density (0.11 ± 0.03 vs. 0.21 ± 0.02, p< 0.001) compared to that of OVX. QEP altered the composition of gut microbiota. We identified 19 potential biomarkers related to osteoporosis. QEP inhibited the elevation of TNF-α (38.86 ± 3.19 vs. 29.43 ± 3.65, p< 0.05) and IL-6 (83.38 ± 16.92 vs. 45.26 ± 3.94, p< 0.05) levels, while it increased the concentrations of acetic acid (271.95 ± 52.41 vs. 447.73 ± 46.54, p< 0.001), propionic acid (28.96 ± 5.73 vs. 53.41 ± 14.26, p< 0.01) and butyric acid (24.92 ± 18.97 vs. 67.78 ± 35.68, p< 0.05).

CONCLUSIONS

These results indicate that QEP has potential of regulating intestinal flora and improving osteoporosis. The combination of anti-osteoporosis drugs and intestinal flora could become a new treatment for osteoporosis.

Combining p-values from various statistical methods for microbiome data

MOTIVATION

In the field of microbiome analysis, there exist various statistical methods that have been developed for identifying differentially expressed features, that account for the overdispersion and the high sparsity of microbiome data. However, due to the differences in statistical models or test formulations, it is quite often to have inconsistent significance results across statistical methods, that makes it difficult to determine the importance of microbiome taxa. Thus, it is practically important to have the integration of the result from all statistical methods to determine the importance of microbiome taxa. A standard meta-analysis is a powerful tool for integrative analysis and it provides a summary measure by combining p-values from various statistical methods. While there are many meta-analyses available, it is not easy to choose the best meta-analysis that is the most suitable for microbiome data.

RESULTS

In this study, we investigated which meta-analysis method most adequately represents the importance of microbiome taxa. We considered Fisher's method, minimum value of p method, Simes method, Stouffer's method, Kost method, and Cauchy combination test. Through simulation studies, we showed that Cauchy combination test provides the best combined value of p in the sense that it performed the best among the examined methods while controlling the type 1 error rates. Furthermore, it produced high rank similarity with the true ranks. Through the real data application of colorectal cancer microbiome data, we demonstrated that the most highly ranked microbiome taxa by Cauchy combination test have been reported to be associated with colorectal cancer.

Rational consideration of Akkermansia muciniphila targeting intestinal health: advantages and challenges

As one of the promising next-generation probiotics (NGPs), Akkermansia muciniphila, a well-known mucin-degrading bacterium, has been proven to be closely related to the metabolic diseases of its human host. However, the role of A. muciniphila in the host’s intestinal health remains ambiguous. Here, we comprehensively summarize and discuss the characteristics, the distribution, and the colonization of A. muciniphila in the human gastrointestinal tract (GIT). We propose that the application of A. muciniphila as a biomarker for longevity, for diagnostics and prognostics of intestinal diseases, or for intestinal health should be cautiously considered. Precise dietary regulation can mediate the treatment of intestinal diseases by altering the abundance of A. muciniphila. Although the beneficial role of A. muciniphila and its component in intestinal inflammation has been discovered, in gnotobiotic mice with specific gut microbiota, certain genotype, and colorectal cancer, or in animal models infected with a specific pathogen, A. muciniphila may be related to the occurrence and development of intestinal diseases. Genomic analysis, emphasizing the strain-level phylogenetic differences of A. muciniphila, indicates that a clear description and discussion of each strain is critical before its practical application. Our review provides much needed insight for the precise application of A. muciniphila.

Murine Gut Microbiome Meta-analysis Reveals Alterations in Carbohydrate Metabolism in Response to Aging

Compositional and functional alterations to the gut microbiota during aging are hypothesized to potentially impact our health. Thus, determining aging-specific gut microbiome alterations is critical for developing microbiome-based strategies to improve health and promote longevity in the elderly. In this study, we performed a meta-analysis of publicly available 16S rRNA gene sequencing data from studies investigating the effect of aging on the gut microbiome in mice. Aging reproducibly increased gut microbial alpha diversity and shifted the microbial community structure in mice. We applied the bioinformatic tool PICRUSt2 to predict microbial metagenome function and established a random forest classifier to differentiate between microbial communities from young and old hosts and to identify aging-specific metabolic features. In independent validation data sets, this classifier achieved an area under the receiver operating characteristic curve (AUC) of 0.75 to 0.97 in differentiating microbiomes from young and old hosts. We found that 50% of the most important predicted aging-specific metabolic features were involved in carbohydrate metabolism. Furthermore, fecal short-chain fatty acid (SCFA) concentrations were significantly decreased in old mice, and the expression of the SCFA receptor Gpr41 in the colon was significantly correlated with the relative abundances of gut microbes and microbial carbohydrate metabolic pathways. In conclusion, this study identified aging-specific alterations in the composition and function of the gut microbiome and revealed a potential relationship between aging, microbial carbohydrate metabolism, fecal SCFA, and colonic Gpr41 expression. IMPORTANCE Aging-associated microbial alteration is hypothesized to play an important role in host health and longevity. However, investigations regarding specific gut microbes or microbial functional alterations associated with aging have had inconsistent results. We performed a meta-analysis across 5 independent studies to investigate the effect of aging on the gut microbiome in mice. Our analysis revealed that aging increased gut microbial alpha diversity and shifted the microbial community structure. To determine if we could reliably differentiate the gut microbiomes from young and old hosts, we established a random forest classifier based on predicted metagenome function and validated its performance against independent data sets. Alterations in microbial carbohydrate metabolism and decreased fecal short-chain fatty acid (SCFA) concentrations were key features of aging and correlated with host colonic expression of the SCFA receptor Gpr41. This study advances our understanding of the impact of aging on the gut microbiome and proposes a hypothesis that alterations in gut microbiota-derived SCFA-host GPR41 signaling are a feature of aging.

Voluntary Wheel Running in Old C57BL/6 Mice Reduces Age-Related Inflammation in the Colon but Not in the Brain

Inflammation is considered a possible cause of cognitive decline during aging. This study investigates the influence of physical activity and social isolation in old mice on their cognitive functions and inflammation. The Barnes maze task was performed to assess spatial learning and memory in 3, 9, 15, 24, and 28 months old male C57BL/6 mice as well as following voluntary wheel running (VWR) and social isolation (SI) in 20 months old mice. Inflammatory gene expression was analyzed in hippocampal and colonic samples by qPCR. Cognitive decline occurs in mice between 15 and 24 months of age. VWR improved cognitive functions while SI had negative effects. Expression of inflammatory markers changed during aging in the hippocampus (Il1a/Il6/S100b/Iba1/Adgre1/Cd68/Itgam) and colon (Tnf/Il6/Il1ra/P2rx7). VWR attenuates inflammaging specifically in the colon (Ifng/Il10/Ccl2/S100b/Iba1), while SI regulates intestinal Il1b and Gfap. Inflammatory markers in the hippocampus were not altered following VWR and SI. The main finding of our study is that both the hippocampus and colon exhibit an increase in inflammatory markers during aging, and that voluntary wheel running in old age exclusively attenuates intestinal inflammation. Based on the existence of the gut-brain axis, our results extend therapeutic approaches preserving cognitive functions in the elderly to the colon.

Impact of the Age of Cecal Material Transfer Donors on Alzheimer’s Disease Pathology in 5xFAD Mice

Alzheimer’s disease is a progressive neurodegenerative disorder affecting around 30 million patients worldwide. The predominant sporadic variant remains enigmatic as the underlying cause has still not been identified. Since efficient therapeutic treatments are still lacking, the microbiome and its manipulation have been considered as a new, innovative approach. 5xFAD Alzheimer’s disease model mice were subjected to one-time fecal material transfer after antibiotics-treatment using two types of inoculation: material derived from the caecum of age-matched (young) wild type mice or from middle aged, 1 year old (old) wild type mice. Mice were profiled after transfer for physiological parameters, microbiome, behavioral tasks, and amyloid deposition. A single time transfer of cecal material from the older donor group established an aged phenotype in the recipient animals as indicated by elevated cultivatable fecal Enterobacteriaceae and Lactobacillaceae representative bacteria, a decreased Firmicutes amount as assessed by qPCR, and by increased levels of serum LPS binding protein. While behavioral deficits were not accelerated, single brain regions (prefrontal cortex and dentate gyrus) showed higher plaque load after transfer of material from older animals. We could demonstrate that the age of the donor of cecal material might affect early pathological hallmarks of Alzheimer’s disease. This could be relevant when considering new microbiome-based therapies for this devastating disorder.

Lactobacillus rhamnosus GG Colonization in Early Life Ameliorates Inflammaging of Offspring by Activating SIRT1/AMPK/PGC-1α Pathway

Inflammaging refers to chronic, low-grade inflammation during aging, which contributes to the pathogenesis of age-related diseases. Studies have shown that probiotic intervention in the aging stage could delay aging-related disorders. However, whether the application of probiotics in early life could have antiaging effects on offspring was unknown. Here, we investigated the effects of Lactobacillus rhamnosus GG (LGG) colonization in early life on inflammaging of offspring. Pregnant mice with the same conception time were given LGG live bacteria (LC group) or LGG fixed bacteria (NC group) from the 18th day after pregnancy until natural birth. The progeny mice were treated with 10⁷ cfu of live or fixed LGG for 0-5 days after birth, respectively. LGG colonization could be detected in the feces of 3-week offspring. The 16S rRNA sequencing analysis of 3-week-old offspring showed that colonization of LGG in early life could alter the composition and diversity of gut microbiota. Interestingly, the beneficial effects of LGG colonization in early life on the microbiota lasted to 8 months old. The abundance of longevity-related bacteria (Lactobacillus, Bifidobacterium, and Akkermansia muciniphila) increased significantly in the LGG colonization group. In addition, LGG colonization increased the abundance of short-chain fatty acid- (SCFA-) producing bacteria and the production of cecal SCFAs. LGG colonization in early life protected the intestinal barrier, enhanced antioxidant defense, attenuated epithelial cell DNA damage, and inhibited intestinal low-grade inflammation in 8-month-old progeny mice. Mechanically, LGG could upregulate Sirtuin1 (SIRT1)/Adenosine 5'-monophosphate-activated protein kinase (AMPK)/Peroxisome proliferator-activated receptor γ coactivator 1-α (PGC-1α) pathway and repress activation of nuclear factor-kappa B (NF-κB), while the protective effect of LGG was blunted after SIRT1 gene silencing. Together, LGG colonization in early life could ameliorate inflammaging of offspring, which would provide a new strategy for the prevention of age-related diseases.

Daily ingestion of Akkermansia mucciniphila for one month promotes healthy aging and increases lifespan in old female mice

The ingestion of certain probiotics has been suggested as a promising nutritional strategy to improve aging. The objective of this work was to evaluate the effects of the daily intake, for a month, of a new probiotic Akkermansia muciniphila (AKK) (2 × 10⁸ cfu/100µL PBS) on behavior, as well as function and redox state of immune cells of old female ICR-CD1 mice (OA group). For this, several behavioral tests were performed, and function and oxidative-inflammatory stress parameters of peritoneal leukocytes were analyzed in OA group, in a group of the same age that did not take AKK (old control, OC group) and in another adult control (AC) group. The results showed, in OA group, a significant improvement of several behavioral responses (coordination, balance, neuromuscular vigor, exploratory ability and anxiety like-behaviors), as well as in immune functions (chemotaxis, phagocytosis, NK activity and lymphoproliferation) and in oxidative stress parameters (glutathione peroxidase and reductase activities, oxidized glutathione and lipid oxidation concentrations) of the peritoneal leukocytes in comparison to those observed in OC group. In addition, peritoneal immune cells from the OA group released lower basal concentrations of pro-inflammatory cytokines (IL-2, IL-6 and TNF-α) compared to those from the OC group. The values of parameters in OA were similar to those in AC group. These improvements in the old mice receiving the probiotic were reflected in an increase in their lifespan. In conclusion, our data indicate that AKK supplementation for a short period could be a good nutritional strategy to promote healthy longevity.

Gut Microbiota Predicts Healthy Late-Life Aging in Male Mice

Calorie restriction (CR) extends lifespan and retards age-related chronic diseases in most species. There is growing evidence that the gut microbiota has a pivotal role in host health and age-related pathological conditions. Yet, it is still unclear how CR and the gut microbiota are related to healthy aging. Here, we report findings from a small longitudinal study of male C57BL/6 mice maintained on either ad libitum or mild (15%) CR diets from 21 months of age and tracked until natural death. We demonstrate that CR results in a significantly reduced rate of increase in the frailty index (FI), a well-established indicator of aging. We observed significant alterations in diversity, as well as compositional patterns of the mouse gut microbiota during the aging process. Interrogating the FI-related microbial features using machine learning techniques, we show that gut microbial signatures from 21-month-old mice can predict the healthy aging of 30-month-old mice with reasonable accuracy. This study deepens our understanding of the links between CR, gut microbiota, and frailty in the aging process of mice.

The Endocannabinoid System: A Bridge between Alzheimer's Disease and Gut Microbiota

Alzheimer's disease (AD) is a neurodegenerative disease that progresses from mild cognitive impairment to severe dementia over time. The main clinical hallmarks of the disease (e.g., beta-amyloid plaques and neurofibrillary tangles) begin during preclinical AD when cognitive deficits are not yet apparent. Hence, a more profound understanding of AD pathogenesis is needed to develop new therapeutic strategies. In this context, the endocannabinoid (eCB) system and the gut microbiome are increasingly emerging as important players in maintaining the general homeostasis and the health status of the host. However, their interaction has come to light just recently with gut microbiota regulating the eCB tone at both receptor and enzyme levels in intestinal and adipose tissues. Importantly, eCB system and gut microbiome, have been suggested to play a role in AD in both animal and human studies. Therefore, the microbiome gut-brain axis and the eCB system are potential common denominators in the AD physiopathology. Hence, the aim of this review is to provide a general overview on the role of both the eCB system and the microbiome gut-brain axis in AD and to suggest possible mechanisms that underlie the potential interplay of these two systems.

Interspecific interactions that affect ageing: Age-distorters manipulate host ageing to their own evolutionary benefits

Genetic causes for ageing are traditionally investigated within a species. Yet, the lifecycles of many organisms intersect. Additional evolutionary and genetic causes of ageing, external to a focal species/organism, may thus be overlooked. Here, we introduce the phrase and concept of age-distorters and its evidence. Age-distorters carry ageing interfering genes, used to manipulate the biological age of other entities upon which the reproduction of age-distorters relies, e.g. age-distorters bias the reproduction/maintenance trade-offs of cells/organisms for their own evolutionary interests. Candidate age-distorters include viruses, parasites and symbionts, operating through specific, genetically encoded interferences resulting from co-evolution and arms race between manipulative non-kins and manipulable species. This interference results in organismal ageing when age-distorters prompt manipulated organisms to favor their reproduction at the expense of their maintenance, turning these hosts into expanded disposable soma. By relying on reproduction/maintenance trade-offs affecting disposable entities, which are left ageing to the reproductive benefit of other physically connected lineages with conflicting evolutionary interests, the concept of age-distorters expands the logic of the Disposable Soma theory beyond species with fixed germen/soma distinctions. Moreover, acknowledging age-distorters as external sources of mutation accumulation and antagonistic pleiotropic genes expands the scope of the mutation accumulation and of the antagonistic pleiotropy theories.

Lipocalin 2 Deficiency Restrains Aging-Related Reshaping of Gut Microbiota Structure and Metabolism

Gut microbiota modulate age-associated changes in metabolism, innate immune responses, and cognitive function. However, the involvement of host factors in the regulation of age-dependent gut microbial structure and intestinal inflammation is largely unknown. Lipocalin 2 (Lcn2) has previously been identified as an adipocytokine and characterized as an important regulator of diet-induced obesity and inflammation. Previous studies have shown that Lcn2 plays a role in high fat diet-induced reshaping of gut microbiota and intestinal inflammation. However, the role of Lcn2 in the regulation of aging-related reshaping of gut microbiota is unclear. Herein, we demonstrate that fecal levels of Lcn2 are reduced during aging. Age reshaped gut microbiota composition in wild-type (WT) mice. Interestingly, Lcn2 deficiency diminished this effect of aging in Lcn2 knockout (LKO) mice, leading to decreased bacterial diversity and increased Firmicutes to Bacteroidetes (F to B) ratio. Specifically, we identified 16 bacteria at the family level that were differentially abundant between WT and LKO mice at old age. Several health-promoting bacteria, including SCFA-producing bacteria, were significantly less prevalent in old LKO mice compared to WT mice, indicating that Lcn2 deficiency shifts the aging-related gut microbial community towards an unhealthy population and lowers microbial butyrate production. Our results provide a line of evidence that Lcn2 plays a role in the control of aging-related reshaping of gut microbiota composition and metabolites.

Extracellular Vesicles from Child Gut Microbiota Enter into Bone to Preserve Bone Mass and Strength

Recently, the gut microbiota (GM) has been shown to be a regulator of bone homeostasis and the mechanisms by which GM modulates bone mass are still being investigated. Here, it is found that colonization with GM from children (CGM) but not from the elderly (EGM) prevents decreases in bone mass and bone strength in conventionally raised, ovariectomy (OVX)-induced osteoporotic mice. 16S rRNA gene sequencing reveals that CGM reverses the OVX-induced reduction of Akkermansia muciniphila (Akk). Direct replenishment of Akk is sufficient to correct the OVX-induced imbalanced bone metabolism and protect against osteoporosis. Mechanistic studies show that the secretion of extracellular vesicles (EVs) is required for the CGM- and Akk-induced bone protective effects and these nanovesicles can enter and accumulate into bone tissues to attenuate the OVX-induced osteoporotic phenotypes by augmenting osteogenic activity and inhibiting osteoclast formation. The study identifies that gut bacterium Akk mediates the CGM-induced anti-osteoporotic effects and presents a novel mechanism underlying the exchange of signals between GM and host bone.

Gut Microbiota Interaction with the Central Nervous System throughout Life

During the last years, accumulating evidence has suggested that the gut microbiota plays a key role in the pathogenesis of neurodevelopmental and neurodegenerative diseases via the gut-brain axis. Moreover, current research has helped to elucidate different communication pathways between the gut microbiota and neural tissues (e.g., the vagus nerve, tryptophan production, extrinsic enteric-associated neurons, and short chain fatty acids). On the other hand, altering the composition of gut microbiota promotes a state known as dysbiosis, where the balance between helpful and pathogenic bacteria is disrupted, usually stimulating the last ones. Herein, we summarize selected findings of the recent literature concerning the gut microbiome on the onset and progression of neurodevelopmental and degenerative disorders, and the strategies to modulate its composition in the search for therapeutical approaches, focusing mainly on animal models studies. Readers are advised that this is a young field, based on early studies, that is rapidly growing and being updated as the field advances.

Age-related changes of microbiota in midlife associated with reduced saccharolytic potential: an in vitro study

BACKGROUND

Gut microbiota is critical in maintaining human health, of which diversity and abundance are subject to significantly reduce in seniors. Gut microbiota is reported to be stable across the long adulthood in general, but lack of careful examination, especially for the midlife people.

RESULTS

To characterize the gut microbiota in midlife, we investigated the faecal microbiota between two groups of healthy people, young, 20-39 years old, n = 15; and midlife, 40-60 years old, n = 15. Metabolic responses of the microbiota were studied through in vitro batch fermentation model. Although no difference was observed in the diversity indices between the two age groups, a wide range taxonomic changes were found in the faecal microbiota. Furthermore, substantial Bifidobacterium reduction was also found in both faecal and fermented samples. The faecal SCFAs are similar in both groups, as well as starch fermentation broth. However, after inulin fermentation, the acetate concentration and inulin degradation rate decreased while the gas production increased in midlife group, suggesting a deficiency of saccharolytic potential in midlife, especially for non-digestible carbohydrate.

CONCLUSIONS

Our data demonstrate that gut microbiota begins to change as early as in midlife. The reduction in Bifidobacterium dominates the change of the microbiota composition in midlife resulting in attenuated saccharolytic capacity of inulin, possibly leading to insufficient acetate production which might be associated with healthy problems in this transition period from young to elderly.

Effect of Senecio scandens ethanol extract on gut microbiota composition in mice

The gut microbiota inhabits the animal intestinal tract, and dysbiosis of the gut microbiota may result in disease. Senecio scandens has pharmaceutical antibacterial activities and is regarded as a broad-spectrum antibiotic in traditional Chinese medicine. Extracts of S. scandens are reported to show strong antimicrobial activity, and quercetin significantly decreases some species in the caecal microflora. However, the bactericidal effects of the extracts on the gut microbiota remain obscure. Here, we supplied ethanol extract of S. scandens, which might possibly be used as an alternative for chemical antibiotics, to mice to investigate the state of the intestinal microbiota. Our studies included a control group, low-, moderate-, and high-dose ethanol extract groups, and cefixime capsule group. The ethanol extract groups did not present reduced diversity or differences in the gut microbiota balance. There were significant differences between the ethanol extract and cefixime capsule groups in terms of the gut microbiota. The control and ethanol extract groups contained similar bacteria, which suggested that the ethanol extract has no inhibitory effect on the gut microbiota in vivo. Bifidobacteriales and Lactobacillus acidophilus were significantly increased in the high-dose group. Both secretory immunoglobulin A and mucin 2 concentrations increased as the dose of ethanol extract increased. The functional prediction differences between the control and ethanol extract groups decreased with increasing extract doses, which indicated that the low-dose and high-dose extract treatments might regulate different pathways and functions of the gut microbiota. The results also highlighted the prevention of bacterial drug resistance in the ethanol extract groups.

Mid-life microbiota crises: middle age is associated with pervasive neuroimmune alterations that are reversed by targeting the gut microbiome

Male middle age is a transitional period where many physiological and psychological changes occur leading to cognitive and behavioural alterations, and a deterioration of brain function. However, the mechanisms underpinning such changes are unclear. The gut microbiome has been implicated as a key mediator in the communication between the gut and the brain, and in the regulation of brain homeostasis, including brain immune cell function. Thus, we tested whether targeting the gut microbiome by prebiotic supplementation may alter microglia activation and brain function in ageing. Male young adult (8 weeks) and middle-aged (10 months) C57BL/6 mice received diet enriched with a prebiotic (10% oligofructose-enriched inulin) or control chow for 14 weeks. Prebiotic supplementation differentially altered the gut microbiota profile in young and middle-aged mice with changes correlating with faecal metabolites. Functionally, this translated into a reversal of stress-induced immune priming in middle-aged mice. In addition, a reduction in ageing-induced infiltration of Ly-6C^hi monocytes into the brain coupled with a reversal in ageing-related increases in a subset of activated microglia (Ly-6C⁺) was observed. Taken together, these data highlight a potential pathway by which targeting the gut microbiome with prebiotics can modulate the peripheral immune response and alter neuroinflammation in middle age. Our data highlight a novel strategy for the amelioration of age-related neuroinflammatory pathologies and brain function.

Gut microbiota remodeling reverses aging-associated inflammation and dysregulation of systemic bile acid homeostasis in mice sex-specifically

Aging is usually characterized with inflammation and disordered bile acids (BAs) homeostasis, as well as gut dysbiosis. The pathophysiological changes during aging are also sexual specific. However, it remains unclear about the modulating process among gut microbiota, BA metabolism, and inflammation during aging. In this study, we established a direct link between gut microbiota and BA profile changes in the liver, serum, and four intestinal segments of both sexes during aging and gut microbiota remodeling by co-housing old mice with young ones. We found aging reduced Actinobacteria in male mice but increased Firmicutes in female mice. Among the top 10 altered genera with aging, 4 genera changed oppositely between male and female mice, and most of the changes were reversed by co-housing in both sexes. Gut microbiota remodeling by co-housing partly rescued the systemically dysregulated BA homeostasis induced by aging in a sex- and tissue-specific manner. Aging had greater impacts on hepatic BA profile in females, but intestinal BA profile in males. In addition, aging increased hepatic and colonic deoxycholic acid in male mice, but reduced them in females. Moreover, muricholic acids shifted markedly in the intestine, especially in old male mice, and partially reversed by co-housing. Notably, the ratios of primary to secondary BAs in the liver, serum, and all four intestinal segments were increased in old mice and reduced by co-housing in both sexes. Together, the presented data revealed that sex divergent changes of gut microbiota and BA profile in multiple body compartments during aging and gut microbiota remodeling, highlighting the sex-specific prevention and treatment of aging-related disorders by targeting gut microbiota-regulated BA metabolism should particularly be given more attention.

Mutation accumulation and horizontal gene transfer in Escherichia coli colonizing the gut of old mice

The ecology and environment of the microbes that inhabit the mammalian intestine undergoes several changes as the host ages. Here, we ask if the selection pressure experienced by a new strain colonizing the aging gut differs from that in the gut of young adults. Using experimental evolution in mice after a short antibiotic treatment, as a model for a common clinical situation, we show that a new colonizing E. coli strain rapidly adapts to the aging gut via both mutation accumulation and bacteriophage-mediated horizontal gene transfer (HGT). The pattern of evolution of E. coli in aging mice is characterized by a larger number of transposable element insertions and intergenic mutations compared to that in young mice, which is consistent with the gut of aging hosts harboring a stressful and iron limiting environment.

A human-origin probiotic cocktail ameliorates aging-related leaky gut and inflammation via modulating the microbiota/taurine/tight junction axis

Inflammation is a major risk factor of morbidity and mortality in older adults. Although its precise etiology is unknown, low-grade inflammation in older adults is commonly associated with increased intestinal epithelial permeability (leaky gut) and abnormal (dysbiotic) gut microbiota. The increasing older population and lack of treatments to reduce aging-related microbiota dysbiosis, leaky gut, and inflammation culminates in a rise in aging-related comorbidities, constituting a significant public health concern. Here, we demonstrate that a human-origin probiotic cocktail containing 5 Lactobacillus and 5 Enterococcus strains isolated from healthy infant gut prevented high-fat diet-induced (HFD-induced) microbiota dysbiosis, leaky gut, inflammation, metabolic dysfunctions, and physical function decline in older mice. Probiotic-modulated gut microbiota primarily reduced leaky gut by increasing tight junctions, which in turn reduced inflammation. Mechanistically, probiotics modulated microbiota in a way to increase bile salt hydrolase activity, which in turn increased taurine abundance in the gut that stimulated tight junctions and suppressed gut leakiness. Furthermore, in Caenorhabditis elegans, taurine increased life span, reduced adiposity and leaky gut, and enhanced physical function. The results suggest that such probiotic therapies could prevent or treat aging-related leaky gut and inflammation in the elderly.

Urinary metabolite signature in bipolar disorder patients during depressive episode

The first few episodes of bipolar disorder (BD) are highly likely to be depressive. This phenomenon causes many BD patients to be misdiagnosed as having major depression. Therefore, it is very important to correctly diagnose BD patients during depressive episode. Here, we conducted this study to identify potential biomarkers for young and middle-aged BD patients during depressive episode. Both gas chromatography-mass spectroscopy (GC-MS) and nuclear magnetic resonance (NMR) spectroscopy were used to profile the urine samples from the recruited subjects. In total, 13 differential metabolites responsible for the discrimination between healthy controls (HCs) and patients were identified. Most differential metabolites had a close relationship with energy homeostasis. Meanwhile, a panel consisting of five differential metabolites was identified. This panel could effectively distinguish the patients from HCs with an AUC of 0.998 in the training set and 0.974 in the testing set. Our findings on one hand could be helpful in developing an objective diagnostic method for young and middle-aged BD patients during depressive episode; on the other hand could provide critical insight into the pathological mechanism of BD and the biological mechanisms responsible for the transformation of different episodes.

The role of the microbiota in sedentary lifestyle disorders and ageing: lessons from the animal kingdom

A paradox of so-called developed countries is that, as the major historical causes of human mortality are eliminated or mitigated by medical progress, lifestyle-related diseases have become major killers. Furthermore, as lifespan is extended by the combined effects of modern medicine, health span is struggling to keep apace because of the burden of noncommunicable diseases linked to diet and sedentary lifestyle. The gut microbiome is now recognized as a plastic environmental risk factor for many of these diseases, the microbiome being defined as the complex community of co-evolved commensal microbes that breaks down components of a complex diet, modulates innate immunity, and produces signalling molecules and metabolites that can impact on diverse regulatory systems in mammals. Aspects of the so-called 'Western' lifestyle linked to disease risk such as energy dense diet and antibiotic treatment are known to affect the composition and function of the microbiome. Here, we review the detailed mechanisms whereby the gut microbiome may modulate risk of diseases linked to sedentary lifestyle and ageing-related health loss. We focus on the comparative value of natural animal models such as hibernation for studying metabolic regulation and the challenge of extrapolating from animal models to processes that occur in human ageing.

Absence of gut microbiota affects lipid metabolism in the prefrontal cortex of mice

Objectives: Lipid metabolism is closely associated with many important biological functions. Here, we conducted this study to explore the effects of gut microbiota on the lipid metabolism in the prefrontal cortex of mice. Methods: Germ-free (GF) mice, specific pathogen-free (SPF) and colonized GF (CGF) mice were used in this study. The open field test (OFT), forced swimming test (FST) and novelty suppressed feeding test (NSFT) were conducted to assess the changes in general behavioral activity. The liquid Chromatography-Tandem Mass Spectrometry (LC-MS/MS) was used to obtain the lipid metabolites. Both one-way analysis of variance (one-way ANOVA) and orthogonal partial least-squares discriminant analysis (OPLS-DA) were used to obtain the key differential lipid metabolites. Results: The behavioral tests showed that compared to SPF mice, GF mice had more center distance, more center time, less immobility time and less latency to familiar food. Meanwhile, 142 key differential lipid metabolites between SPF mice and GF mice were identified. These lipid metabolites mainly belonged to glycerophospholipids, glycerolipids, sphingolipids, and saccharolipids. The gut microbiota colonization did not reverse these changed behavioral phenotypes, but could restore 25 key differential lipid metabolites. Discussion: These results showed that the absence of gut microbiota could influence host behaviors and lipid metabolism. Our findings could provide original and valuable data for future studies to further investigate the microbiota-gut-brain axis.

The Microbiota-Gut-Brain Axis

The importance of the gut-brain axis in maintaining homeostasis has long been appreciated. However, the past 15 yr have seen the emergence of the microbiota (the trillions of microorganisms within and on our bodies) as one of the key regulators of gut-brain function and has led to the appreciation of the importance of a distinct microbiota-gut-brain axis. This axis is gaining ever more traction in fields investigating the biological and physiological basis of psychiatric, neurodevelopmental, age-related, and neurodegenerative disorders. The microbiota and the brain communicate with each other via various routes including the immune system, tryptophan metabolism, the vagus nerve and the enteric nervous system, involving microbial metabolites such as short-chain fatty acids, branched chain amino acids, and peptidoglycans. Many factors can influence microbiota composition in early life, including infection, mode of birth delivery, use of antibiotic medications, the nature of nutritional provision, environmental stressors, and host genetics. At the other extreme of life, microbial diversity diminishes with aging. Stress, in particular, can significantly impact the microbiota-gut-brain axis at all stages of life. Much recent work has implicated the gut microbiota in many conditions including autism, anxiety, obesity, schizophrenia, Parkinson’s disease, and Alzheimer’s disease. Animal models have been paramount in linking the regulation of fundamental neural processes, such as neurogenesis and myelination, to microbiome activation of microglia. Moreover, translational human studies are ongoing and will greatly enhance the field. Future studies will focus on understanding the mechanisms underlying the microbiota-gut-brain axis and attempt to elucidate microbial-based intervention and therapeutic strategies for neuropsychiatric disorders.

Monocyte mobilisation, microbiota & mental illness

The gastrointestinal microbiome has emerged as a key player in regulating brain and behaviour. This has led to the strategy of targeting the gut microbiota to ameliorate disorders of the central nervous system. Understanding the underlying signalling pathways in which the microbiota impacts these disorders is crucial for the development of future therapeutics for improving CNS functionality. One of the major pathways through which the microbiota influences the brain is the immune system, where there is an increasing appreciation for the role of monocyte trafficking in regulating brain homeostasis. In this review, we will shed light on the role of monocyte trafficking as a relay of microbiota signals in conditions where the central nervous system is in disorder, such as stress, peripheral inflammation, ageing, traumatic brain injury, stroke, multiple sclerosis, Alzheimer's disease and Parkinson's disease. We also cover how the gastrointestinal microbiota is implicated in these mental illnesses. In addition, we aim to discuss how the monocyte system can be modulated by the gut microbiota to mitigate disorders of the central nervous system, which will lead to novel microbiota-targeted strategies.

Meta-taxonomic analysis of prokaryotic and eukaryotic gut flora in stool samples from visceral leishmaniasis cases and endemic controls in Bihar State India

Visceral leishmaniasis (VL) caused by Leishmania donovani remains of public health concern in rural India. Those at risk of VL are also at risk of other neglected tropical diseases (NTDs) including soil transmitted helminths. Intestinal helminths are potent regulators of host immune responses sometimes mediated through cross-talk with gut microbiota. We evaluate a meta-taxonomic approach to determine the composition of prokaryotic and eukaryotic gut microflora using amplicon-based sequencing of 16S ribosomal RNA (16S rRNA) and 18S rRNA gene regions. The most abundant bacterial taxa identified in faecal samples from Bihar State India were Prevotella (37.1%), Faecalibacterium (11.3%), Escherichia-Shigella (9.1%), Alloprevotella (4.5%), Bacteroides (4.1%), Ruminococcaceae UCG-002 (1.6%), and Bifidobacterium (1.5%). Eukaryotic taxa identified (excluding plant genera) included Blastocystis (57.9%; Order: Stramenopiles), Dientamoeba (12.1%; Family: Tritrichomonadea), Pentatrichomonas (10.1%; Family: Trichomonodea), Entamoeba (3.5%; Family: Entamoebida), Ascaridida (0.8%; Family: Chromodorea; concordant with Ascaris by microscopy), Rhabditida (0.8%; Family: Chromodorea; concordant with Strongyloides), and Cyclophyllidea (0.2%; Order: Eucestoda; concordant with Hymenolepis). Overall alpha (Shannon's, Faith's and Pielou's indices) and beta (Bray-Curtis dissimilarity statistic; weighted UniFrac distances) diversity of taxa did not differ significantly by age, sex, geographic subdistrict, or VL case (N = 23) versus endemic control (EC; N = 23) status. However, taxon-specific associations occurred: (i) Ruminococcaceae UCG- 014 and Gastranaerophilales_uncultured bacterium were enriched in EC compared to VL cases; (ii) Pentatrichomonas was more abundant in VL cases than in EC, whereas the reverse occurred for Entamoeba. Across the cohort, high Escherichia-Shigella was associated with reduced bacterial diversity, while high Blastocystis was associated with high bacterial diversity and low Escherichia-Shigella. Individuals with high Blastocystis had low Bacteroidaceae and high Clostridiales vadin BB60 whereas the reverse held true for low Blastocystis. This scoping study provides useful baseline data upon which to develop a broader analysis of pathogenic enteric microflora and their influence on gut microbial health and NTDs generally.

Anti-ageing and antioxidant effects of sulfate oligosaccharides from green algae Ulva lactuca and Enteromorpha prolifera in SAMP8 mice

Oligosaccharides from green algae Ulva lactuca (ULO) and Enteromorpha prolifera (EPO) were used for investigation of anti-ageing effects and the underlying mechanism in SAMP8 mice. The structural properties of ULO and EPO were analyzed by fourier-transform infrared spectroscopy, gas chromatography-mass spectrometry, and agarose gel electrophoresis. These oligosaccharides enhanced the glutathione, superoxide dismutase, catalase, and telomerase levels and total antioxidant capicity, and decreased the levels of malondialdehyde and advanced glycation end products. After ULO and EPO treatment, the levels of inflammatory factors, including IFN-γ, TNF-α, and IL-6, decreased; the BDNF and ChAT levels increased; and hippocampal neurons were protected. Downregulation of the p53 and FOXO1 genes and upregulation of the Sirt1 gene indicated that ULO and EPO have potential therapeutic effects in the prevention of ageing in SAMP8 mice. By 16S rRNA gene high-throughput sequencing, the abundance of Desulfovibrio was discovered to be markedly different in mice treated with ULO and EPO. The abundances of Verrucomicrobiaceae, Odoribacteraceae, Mogibacteriaceae, Planococcaceae, and Coriobacteriaceae were positively correlated with age-related indicators. These results demonstrated that oligosaccharides from U. lactuca and E. prolifera are ideal candidate compounds that can be used in functional foods and pharmaceuticals to prevent ageing.

Akkermansia muciniphila ameliorates the age-related decline in colonic mucus thickness and attenuates immune activation in accelerated aging Ercc1 -/Δ7 mice

BACKGROUND

The use of Akkermansia muciniphila as potential therapeutic intervention is receiving increasing attention. Health benefits attributed to this bacterium include an improvement of metabolic disorders and exerting anti-inflammatory effects. The abundance of A. muciniphila is associated with a healthy gut in early mid- and later life. However, the effects of A. muciniphila on a decline in intestinal health during the aging process are not investigated yet. We supplemented accelerated aging Ercc1 -/Δ7 mice with A. muciniphila for 10 weeks and investigated histological, transcriptional and immunological aspects of intestinal health.

RESULTS

The thickness of the colonic mucus layer increased about 3-fold after long-term A. muciniphila supplementation and was even significantly thicker compared to mice supplemented with Lactobacillus plantarum WCFS1. Colonic gene expression profiles pointed towards a decreased expression of genes and pathways related to inflammation and immune function, and suggested a decreased presence of B cells in colon. Total B cell frequencies in spleen and mesenteric lymph nodes were not altered after A. muciniphila supplementation. Mature and immature B cell frequencies in bone marrow were increased, whereas B cell precursors were unaffected. These findings implicate that B cell migration rather than production was affected by A. muciniphila supplementation. Gene expression profiles in ileum pointed toward a decrease in metabolic- and immune-related processes and antimicrobial peptide production after A. muciniphila supplementation. Besides, A. muciniphila decreased the frequency of activated CD80+CD273- B cells in Peyer's patches. Additionally, the increased numbers of peritoneal resident macrophages and a decrease in Ly6Cint monocyte frequencies in spleen and mesenteric lymph nodes add evidence for the potentially anti-inflammatory properties of A. muciniphila.

CONCLUSIONS

Altogether, we show that supplementation with A. muciniphila prevented the age-related decline in thickness of the colonic mucus layer and attenuated inflammation and immune-related processes at old age. This study implies that A. muciniphila supplementation can contribute to a promotion of healthy aging.

Influence of Porphyromonas gingivalis in gut microbiota of streptozotocin-induced diabetic mice

OBJECTIVES

Increasing evidence suggests that periodontitis can exacerbate diabetes, and gut bacterial dysbiosis appears to be linked with the diabetic condition. The present study examined the effects of oral administration of the periodontopathic bacterium, Porphyromonas gingivalis, on the gut microbiota and systemic conditions in streptozotocin-induced diabetic mice.

MATERIALS AND METHODS

Diabetes was induced by streptozotocin injection in C57BL/6J male mice (STZ). STZ and wild-type (WT) mice were orally administered P. gingivalis (STZPg, WTPg) or saline (STZco, WTco). Feces were collected, and the gut microbiome was examined by 16S rRNA gene sequencing. The expression of genes related to inflammation, epithelial tight junctions, and glucose/fatty acid metabolism in the ileum or liver were examined by quantitative PCR.

RESULTS

The relative abundance of several genera, including Brevibacterium, Corynebacterium, and Facklamia, was significantly increased in STZco mice compared to WTco mice. The relative abundances of Staphylococcus and Turicibacter in the gut microbiome were altered by oral administration of P. gingivalis in STZ mice. STZPg mice showed higher concentrations of fasting blood glucose and inflammatory genes levels in the ileum, compared to STZco mice.

CONCLUSIONS

Oral administration of P. gingivalis altered the gut microbiota and aggravated glycemic control in streptozotocin-induced diabetic mice.

Clostridium Difficile Infection: An Immunological Conundrum

The lack of comprehensive understanding of the way immunity backfires on incidence and complications has made Clostridium difficile infection (CDI), the infectious disease of our times, as evidenced by in the parallel course it follows along epidemic of chronic degenerative diseases. Within these ailments, if as suspected the main effect of Clostridium difficile A and B toxins depends on inflammation, then aberrant immune function due to antibiotics would explain IBD triggering after treatment but also, the higher incidence and mortality surrounding disorders that are inflammatory and/or that show abatement of neutrophils. This review will discuss severity of the disease in terms of challenges to immunity during the progression of acute illness. We will identify the common signals in the communication between microbiota and inflammatory cells, as well as the sequestration of the regulatory network by Clostridium difficile, which leads to tissue damage and prevents its elimination from intestinal lumen.

The intestinal microbiome and its relevance for functionality in older persons

PURPOSE OF REVIEW

This article summarizes the advances of research on the role of the intestinal microbiota in influencing sarcopenia, frailty, and cognitive dysfunction in older individuals, and thus its relevance for healthy active ageing.

RECENT FINDINGS

Age-related alterations of intestinal microbiota composition may negatively influence muscle protein synthesis and function by promoting chronic systemic inflammation, insulin resistance, oxidative stress, and reducing nutrient bioavailability. However, this 'gut-muscle axis' hypothesis is not supported by human data to date. Some observational studies have instead demonstrated that, in older individuals, frailty and Alzheimer-type dementia are associated with fecal microbiota dysbiosis, that is, reduced biodiversity and overexpression of pathobionts. The main possible mechanisms of the 'gut-brain axis' in cognitive function modulation include effects on neurotransmission, neuroinflammation, and amyloid deposition. Conversely, longevity in good health may be associated with the maintenance of a fecal microbiota composition similar to that of healthy young adults. However, the role of gut microbiota as an independent modulator of frailty and cognition still remains uncertain, being influenced by several physiological factors, including diet and exercise.

SUMMARY

The intestinal microbiome composition represents a possible determinant of functional performance in older people, and a promising target for antiaging therapeutic interventions.