Disturbed rhythmicity of intestinal hydrogen peroxide alters gut microbial oscillations in BMAL1-deficient monkeys

Gut microbiota-astrocyte axis: new insights into age-related cognitive decline

With the rapidly aging human population, age-related cognitive decline and dementia are becoming increasingly prevalent worldwide. Aging is considered the main risk factor for cognitive decline and acts through alterations in the composition of the gut microbiota, microbial metabolites, and the functions of astrocytes. The microbiota-gut-brain axis has been the focus of multiple studies and is closely associated with cognitive function. This article provides a comprehensive review of the specific changes that occur in the composition of the gut microbiota and microbial metabolites in older individuals and discusses how the aging of astrocytes and reactive astrocytosis are closely related to age-related cognitive decline and neurodegenerative diseases. This article also summarizes the gut microbiota components that affect astrocyte function, mainly through the vagus nerve, immune responses, circadian rhythms, and microbial metabolites. Finally, this article summarizes the mechanism by which the gut microbiota-astrocyte axis plays a role in Alzheimer's and Parkinson's diseases. Our findings have revealed the critical role of the microbiota-astrocyte axis in age-related cognitive decline, aiding in a deeper understanding of potential gut microbiome-based adjuvant therapy strategies for this condition.

Effects of housing conditions on health and gut microbiome of female cynomolgus monkeys and improvement of welfare by checking menstruation under socially housed condition

Laboratory non-human primates (NHPs) are commonly subjected to social deprivation in various scientific researches. However, the impact of social deprivation on gut microbiome remains largely unknown. We examined the health status and gut microbiota of female cynomolgus monkeys housed in isolation or social conditions and found that social deprivation brought adverse effects to monkeys by inhibiting their growth, remodeling the immune status, and decreasing the level of beneficial biochemical parameters. 16S rRNA gene sequencing revealed that the gut microbial composition and function differed between grouped and isolated monkeys. Specifically, grouping the single-caged young monkeys to socially housed condition could decrease the relative abundance of Firmicutes and increase the relative abundance of Bacteroidetes, while separating the socially housed middle-aged monkeys into single cages showed the opposite trend. Besides, training female monkeys to detect menstruation under socially-housed condition could increase their body weight change and adjusting their immune status, thus attenuating the adverse effects of separating them to single cages. Our results verified the significant role of grouping in mitigating adverse health and microbiota alterations caused by isolation in female cynomolgus monkeys and emphasized the importance of training NHPs to cooperate with experimental procedures under socially housed condition, which could not only improve the welfare of cynomolgus monkeys but also enhance the accuracy and reliability of scientific results.

Circadian metabolic adaptations to infections

Circadian clocks are biological oscillators that evolved to coordinate rhythms in behaviour and physiology around the 24-hour day. In mammalian tissues, circadian rhythms and metabolism are highly intertwined. The clock machinery controls rhythmic levels of circulating hormones and metabolites, as well as rate-limiting enzymes catalysing biosynthesis or degradation of macromolecules in metabolic tissues, such control being exerted both at the transcriptional and post-transcriptional level. During infections, major metabolic adaptation occurs in mammalian hosts, at the level of both the single immune cell and the whole organism. Under these circumstances, the rhythmic metabolic needs of the host intersect with those of two other players: the pathogen and the microbiota. These three components cooperate or compete to meet their own metabolic demands across the 24 hours. Here, we review findings describing the circadian regulation of the host response to infection, the circadian metabolic adaptations occurring during host-microbiota-pathogen interactions and how such regulation can influence the immune response of the host and, ultimately, its own survival.This article is part of the Theo Murphy meeting issue 'Circadian rhythms in infection and immunity'.

Murine gut microbial interactions exert antihyperglycemic effects

The correlations between gut microbiota and host metabolism have been studied extensively, whereas little relevant work has been done to investigate the impact of gut microbial interactions on host metabolism. With the use of a bacteriocin-targeting strategy, we aimed to identify the gut microbes associated with glucose and lipid metabolism by adjusting the gut microbial composition of mice fed a high-fat diet. To fulfill this goal, a Listeria monocytogenes (Lmo)-derived bacteriocin Lmo2776 secretion module was constructed and integrated into the genome of Escherichia coli Nissle 1917 (EcN), yielding the Lmo2776-secreting strain EcN-2776. In high-fat diet-fed mice, EcN-2776 administration decreased blood glucose and increased serum triglyceride, and gene amplicon sequencing of 16S rRNA in these mice indicated that intestinal secretion of Lmo2776 led to adjustment of the gut microbial composition. Specifically, Lmo2776 restricted the growth of Ligilactobacillus murinus, thus alleviating its inhibitory impact towards Faecalibaculum rodentium. Further analyses indicated that F. rodentium administration decreased the fasting blood glucose of high-fat diet-fed mice, an effect that may be attributable to the intestinal consumption of glucose by F. rodentium. In this study, we identified the gut microbes associated with glucose metabolism, uncovered their interactions, and deciphered the impact of these gut microbial interactions on the host glucose metabolism. Our findings may pave the way for the treatment of hyperglycemia from the perspective of gut microbial interactions.

Characterizing the rhythmic oscillations of gut bacterial and fungal communities and their rhythmic interactions in male cynomolgus monkeys

The circadian oscillation of gut microbiota plays vital roles in the normal physiology and health of the host. Although the diurnal oscillation of intestinal bacteria has been extensively studied, little relevant work has been done on intestinal fungi. Besides, the rhythmic correlations between bacterial and fungal microbes are also scarcely reported. Here, we investigated the diurnal oscillations of bacterial and fungal communities in male cynomolgus monkeys by performing 16S rRNA and ITS amplicon sequencing. As for bacterial genera, we found that the relative abundance of Prevotella, norank_f_Eubacterium_coprostanoligenes_group, and Peptococcus underwent significant changes at ZT12 (19:00) and exhibited obvious rhythmic oscillations. Consequently, most of the bacterial functions varied at ZT12 and were positively correlated with the bacterial genera norank_f_Eubacterium_coprostanoligenes_group and Prevotella. Among the fungal genera, the relative abundance of Aspergillus and Talaromyces decreased at ZT18 (1:00) and showed slight rhythmic oscillations. As for the fungal function, the undefined saprotroph showed slight rhythmic oscillation and was positively correlated with the fungal genus Aspergillus. Notably, we characterized the correlations between intestinal bacteria and fungi every 6 h over the course of a day and found that the bacterial and fungal microbes interacted closely, with the most bacteria-fungi interactions occurring at ZT12. Our study contributed to a more comprehensive understanding of the diurnal oscillation patterns of bacterial and fungal microbes in male cynomolgus monkeys and uncovered their correlations during a diurnal cycle.

IMPORTANCE

The rhythmic oscillation of gut microbiota can impact the physiology activity and disease susceptibility of the host. Until now, most of the studies are focused on bacterial microbes, ignoring other components of gut microbes, such as fungal microbes (mycobiota). Besides, only few studies have addressed the rhythmic correlations between gut bacteria and fungi. Here, we analyzed the rhythmic oscillations of bacterial and fungal communities in male cynomolgus monkeys by performing 16S rRNA and ITS amplicon sequencing. Apart from identifying the rhythmically oscillated bacterial and fungal microbes, we conducted the correlation analysis between these two microbial communities and found that the intestinal bacteria and fungi exhibited close interactions rhythmically, with the most interactions occurring at ZT12. Thus, our study not only investigated the rhythmic oscillations of gut bacterial and fungal communities in male cynomolgus monkeys but also uncovered their rhythmic interactions.

Improving the growth and intestinal colonization of Escherichia coli Nissle 1917 by strengthening its oligopeptides importation ability

Escherichia coli Nissle 1917 (EcN), the probiotic featured with well-established safety in different host, is emerging as a favored chassis for the construction of engineered probiotics for disease treatment. However, limited by the low intestinal colonization ability of EcN, repeated administration is required to maximize the health benefits of the EcN-derived engineered probiotics. Here, using fecal metabolites as "metabolites pool", we developed a metabolomic strategy to characterize the comprehensive metabolic profile of EcN. Compared with Prevotella copri DSM 18205 (P. copri), one of the dominant microbes in gut flora, EcN exhibited minor growth advantage under the fecal metabolites-containing condition for its lower metabolic capability towards fecal metabolites. Further study indicated that EcN lacked the ability to import the oligopeptides containing more than two amino acids. The shortage of oligopeptides-derived amino acids might limit the growth of EcN by restricting its purine metabolism. Assisted with the bioinformatic and qRT-PCR analyses, we identified a tripeptides-specific importer Pc-OPT in P. copri, which was mainly distributed in genera Prevotella and Bacteroides. Overexpression of Pc-OPT improved the tripeptides importation of EcN and promoted its growth and intestinal colonization. Notably, 16S rRNA gene amplicon sequencing results indicated that strengthening the oligopeptides importation ability of EcN might promote its intestinal colonization by adjusting the gut microbial composition. Our study reveals that the growth and intestinal colonization of EcN is limited by its insufficient oligopeptides importation and paves road for promoting the efficacy of the EcN-derived synthetic probiotics by improving their intestinal colonization ability.

Hydrogen peroxide in breast milk is crucial for gut microbiota formation and myelin development in neonatal mice

Early life environment influences mammalian brain development, a growing area of research within the Developmental Origins of Health and Disease framework, necessitating a deeper understanding of early life factors on children's brain development. This study introduces a mouse model, LAO1 knockout mice, to investigate the relationship between breast milk, the gut microbiome, and brain development. The results reveal that breast milk's reactive oxygen species (ROS) are vital in shaping the neonatal gut microbiota. Decreased hydrogen peroxide (H2O2) levels in milk disrupt the gut microbiome and lead to abnormal metabolite production, including D-glucaric acid. This metabolite inhibits hippocampal myelin formation during infancy, potentially contributing to behavioral abnormalities observed in adulthood. These findings suggest that H2O2 in breast milk is crucial for normal gut microbiota formation and brain development, with implications for understanding and potentially treating neurodevelopmental disorders in humans.

Studying the Human Microbiota: Advances in Understanding the Fundamentals, Origin, and Evolution of Biological Timekeeping

The recently observed circadian oscillations of the intestinal microbiota underscore the profound nature of the human-microbiome relationship and its importance for health. Together with the discovery of circadian clocks in non-photosynthetic gut bacteria and circadian rhythms in anucleated cells, these findings have indicated the possibility that virtually all microorganisms may possess functional biological clocks. However, they have also raised many essential questions concerning the fundamentals of biological timekeeping, its evolution, and its origin. This narrative review provides a comprehensive overview of the recent literature in molecular chronobiology, aiming to bring together the latest evidence on the structure and mechanisms driving microbial biological clocks while pointing to potential applications of this knowledge in medicine. Moreover, it discusses the latest hypotheses regarding the evolution of timing mechanisms and describes the functions of peroxiredoxins in cells and their contribution to the cellular clockwork. The diversity of biological clocks among various human-associated microorganisms and the role of transcriptional and post-translational timekeeping mechanisms are also addressed. Finally, recent evidence on metabolic oscillators and host-microbiome communication is presented.

Role of Bmal1 and Gut Microbiota in Alzheimer's Disease and Parkinson's Disease Pathophysiology: The Probable Effect of Melatonin on Their Association

In recent years, the role of new factors in the pathophysiology of neurodegenerative diseases has been investigated. Alzheimer's disease (AD) and Parkinson's disease (PD) are the most common neurodegenerative diseases worldwide. Although pathological changes such as the accumulation of aggregated proteins in the brain and inflammatory responses are known as the main factors involved in the development of these diseases, new studies show the role of gut microbiota and circadian rhythm in the occurrence of these changes. However, the association between circadian rhythm and gut microbiota in AD and PD has not yet been investigated. Recent results propose that alterations in circadian rhythm regulators, mainly Bmal1, may regulate the abundance of gut microbiota. This correlation has been linked to the regulation of the expression of immune-related genes and Bmal-1 mediated oscillation of IgA and hydrogen peroxide production. These data seem to provide new insight into the molecular mechanism of melatonin inhibiting the progression of AD and PD. Therefore, this manuscript aims to review the role of the gut microbiota and circadian rhythm in health and AD and PD and also presents a hypothesis on the effect of melatonin on their communication.