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Early environmental exposure to oxytetracycline in Danio rerio may contribute to neurobehavioral abnormalities in adult zebrafish.
The common antibiotic oxytetracycline (OTC) is nowadays commonly found in natural aquatic environments. However, the underlying mechanisms of low-dose OTC exposure and its neurotoxic effects on aquatic animals remain unknown. In this study, we exposed zebrafish larvae to environmental concentrations of OTC in early life and performed neurobehavioral, 16S rRNA gene sequencing, and transcriptomic analyses. OTC exposure resulted in hyperactivity of larvae and a significant reduction in the number of neurons in the midbrain. The expression levels of 15 genes related to neural function changed. Additionally, the composition of 65 genera of the gut microbiota of larvae was altered, which may be one of the reasons for the abnormal neural development. We further studied the long-term outcomes among adult fish long after cessation of OTC exposure. OTC treatment caused adult fish to be depressive and impulsive, symbolizing bipolar disorder. Adult fish exposed to OTC had significantly fewer neurons and their gut bacteria composition did not recover 104 days after terminating OTC exposure. Finally, we analyzed the correlation between the gut microbiota of larvae, genes related to neural function, and metabolites of adult fish brain tissue. The results showed that the abundance of several members of the biome in larvae was related to the transcription levels of genes related to neural function, which were related to the metabolic levels in the adult brain. In conclusion, our study showed that early-life exposure to environmental concentrations of OTC can lead to persistent neurobehavioral abnormalities until adulthood through dysbiosis in the gut microbiota.
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Mind-altering with the gut: Modulation of the gut-brain axis with probiotics.
It is increasingly evident that bidirectional interactions exist among the gastrointestinal tract, the enteric nervous system, and the central nervous system. Recent preclinical and clinical trials have shown that gut microbiota plays an important role in these gut-brain interactions. Furthermore, alterations in gut microbiota composition may be associated with pathogenesis of various neurological disorders, including stress, autism, depression, Parkinson's disease, and Alzheimer's disease. Therefore, the concepts of the microbiota-gut-brain axis is emerging. Here, we review the role of gut microbiota in bidirectional interactions between the gut and the brain, including neural, immune-mediated, and metabolic mechanisms. We highlight recent advances in the understanding of probiotic modulation of neurological and neuropsychiatric disorders via the gut-brain axis.
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Molecular imaging of microbiota-gut-brain axis: searching for the right targeted probe for the right target and disease.
The highly bidirectional dialogue between the gut and the brain is markedly stimulated and influenced by the microbiome through integrated neuroendocrine, neurological and immunological processes. Gut microbiota itself communicate with the host producing hormonal intermediates, metabolites, proteins, and toxins responsible for a variety of biochemical and functional inputs, thereby shaping host homeostasis. Indeed, a dysregulated microbiota-gut-brain axis might be the origin of many neuroimmune-mediated disorders, e.g. autism, multiple sclerosis, depression, Alzheimer's and Parkinson's disease, which appear months or even years prior to a diagnosis, corroborating the theory that the pathological process is spread from the gut to the brain. A much deeper comprehension of how commensal microbe can be manipulated to interfere with disease progression is crucial for developing new strategies to diagnose and treat diseases. In recent years, the potential of positron-emission-tomography (PET) in the field of bacteria detection has gained attention. The uptake of several PET tracers has been evaluated to investigate infection pathophysiology, e.g. sterile or pathogen-mediated infection, monitoring of progression, or as a surrogate endpoint in clinical trials. In this minireview, we briefly describe the role of microbiome-gut-brain axis in health and disease and we discuss the imaging modalities and agents that could be applied to study the dynamic interactions between microbiome, gut and brain. These are key aspects in understanding the biochemical lexicon underpinning the microbiome-host crosstalk that would enable the development of diagnostics and therapeutics by targeting the human microbiota.
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Influence of gut microbiota on neuropsychiatric disorders.
The last decade has witnessed a growing appreciation of the fundamental role played by an early assembly of a diverse and balanced gut microbiota and its subsequent maintenance for future health of the host. Gut microbiota is currently viewed as a key regulator of a fluent bidirectional dialogue between the gut and the brain (gut-brain axis). A number of preclinical studies have suggested that the microbiota and its genome (microbiome) may play a key role in neurodevelopmental and neurodegenerative disorders. Furthermore, alterations in the gut microbiota composition in humans have also been linked to a variety of neuropsychiatric conditions, including depression, autism and Parkinson's disease. However, it is not yet clear whether these changes in the microbiome are causally related to such diseases or are secondary effects thereof. In this respect, recent studies in animals have indicated that gut microbiota transplantation can transfer a behavioral phenotype, suggesting that the gut microbiota may be a modifiable factor modulating the development or pathogenesis of neuropsychiatric conditions. Further studies are warranted to establish whether or not the findings of preclinical animal experiments can be generalized to humans. Moreover, although different communication routes between the microbiota and brain have been identified, further studies must elucidate all the underlying mechanisms involved. Such research is expected to contribute to the design of strategies to modulate the gut microbiota and its functions with a view to improving mental health, and thus provide opportunities to improve the management of psychiatric diseases. Here, we review the evidence supporting a role of the gut microbiota in neuropsychiatric disorders and the state of the art regarding the mechanisms underlying its contribution to mental illness and health. We also consider the stages of life where the gut microbiota is more susceptible to the effects of environmental stressors, and the possible microbiota-targeted intervention strategies that could improve health status and prevent psychiatric disorders in the near future.
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Research Progress on the Regulatory Mechanisms of Gut Microbiota in Methamphetamine Addiction and Targeted Interventions.
Methamphetamine (METH) is a globally prevalent, highly addictive synthetic psychostimulant, for which no FDA-approved pharmacotherapy is currently available for METH use disorder (MUD). The microbiota-gut-brain axis has been well established as a key regulatory pathway in substance use disorders, yet its specific mechanistic basis and translational potential in METH addiction remain to be systematically elucidated. This review synthesizes current preclinical and clinical evidence demonstrating that METH exposure induces profound gut microbiota dysbiosis, characterized by the depletion of beneficial genera such as Faecalibacterium and Lactobacillus, enrichment of proinflammatory phylum Proteobacteria and concurrent dysregulation of microbial metabolites including short-chain fatty acids (SCFAs), tryptophan derivatives and bile acids. These microbial signals mediate bidirectional gut-CNS crosstalk through neuroimmune, neuroendocrine (hypothalamic-pituitary-adrenal (HPA) axis) and vagal pathways, thereby exacerbating the core central pathologies of METH addiction: neurotransmitter system imbalance, neuroinflammation and oxidative stress and dysfunction of addiction-related neural circuits. We further elaborate that gut microbiota-driven epigenetic modifications and transgenerational effects reinforce the persistence and heritability of addictive phenotypes. Importantly, microbiota-targeted interventions, including probiotics, prebiotics, faecal microbiota transplantation (FMT) and dietary modulation, can alleviate METH-induced affective disturbances (anxiety/depression-like behaviours), multiorgan damage (neurotoxicity, reproductive impairment) and relapse risk, via restoring gut microbial homeostasis, repairing intestinal barrier integrity and normalizing gut-brain axis signalling. Collectively, this review positions the gut microbiota as a critical peripheral regulatory node in METH addiction, providing a robust preclinical foundation for the development of gut-brain axis-targeted combination therapies for MUD.
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Ergothioneine, a metabolite of the gut bacterium Lactobacillus reuteri, protects against stress-induced sleep disturbances.
The relationships between depression and gut microbiota, particularly those involving the immune system, have become a major focus of recent research. Here, we analyzed changes in gut microbiota and their sulfur metabolites in the feces of a depression rat model using the modified 14-day social defeat stress (SDS) paradigm. Our results showed that SDS increased fecal Lactobacillus reuteri in correlation with ergothioneine levels at around day 11, which continued for at least 1 month following SDS administration. In vitro study further revealed that L. reuteri is capable of producing ergothioneine. Although the known anti-inflammatory and anti-oxidative actions of ergothioneine suggested that the increased fecal ergothioneine levels may be related to intestinal anti-inflammatory defense mechanisms, no change was observed in the plasma ergothioneine levels during the same observation period, indicating that the defense mechanisms may not be sufficiently reflected in the body. As ergothioneine is a natural ingredient that is absorbed mainly from the upper gastrointestinal tract, we hypothesized that oral ergothioneine may exert antidepressant effects. As expected, oral administration of ergothioneine prior to and during the SDS paradigm had a preventative effect on SDS-induced depressive behaviors, such as social avoidance and depression-like sleep abnormalities, particularly those of rapid eye movement sleep. These findings indicate that ergothioneine, a metabolite of L. reuteri, may be a common substance in the microbiota-gut-brain axis that prevents stress-induced sleep disturbances, especially those associated with depression.
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The influence of endocrine disruptors on the gut microbiota.
Endocrine disruptors (EDs) are closely associated with the second brain, the microbiota-derived enteric nervous system, commonly referred to as the gut microbiota. The microbiota plays a crucial role in human health and the development of diseases. In today's industrialized world, the presence of EDs in air, water, and soil leads to primary human exposure through dermal contact and ingestion. The impact of these EDs on the microbiota remains unclear. EDs that disrupt the balance of the gut microbiota may contribute to a range of disorders, including metabolic (obesity, diabetes mellitus), cardiovascular (vascular stenosis, cerebrovascular disease), reproductive (infertility, ovarian and testicular tumors), neurological (dysfunction of the amygdala, cortex, and cerebellum), and behavioral disorders (dementia, depression, anxiety, and schizophrenia). This review examines the effects of commonly encountered environmental EDs on the gut microbiota and summarizes the most recent findings on this topic. The concept of the microbiota-derived enteric nervous system and the modulation of the hormonal system through interactions between microorganisms and environmental chemicals have prompted specialists in endocrinology and metabolism to reconsider patient management and treatment strategies. This necessitates a comprehensive evaluation of treatment options that incorporate microbiome data. The information presented in this review will help illuminate future research directions and serve as a valuable resource for subsequent studies.
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Loss of eating control and cognitive flexibility: Involvement of gut microbiota.
Loss of eating control is a crucial factor in developing obesity, which has become a global health concern, causing important cardiovascular, metabolic, emotional, and cognitive co-morbidities. A major cognitive alteration associated with loss of eating control and obesity is the impairment of cognitive flexibility and inhibitory control. An increasing number of studies confirm that gut microbiota is a significant contributor to loss of eating control, obesity, and cognitive function. Therefore, we have investigated whether gut microbiota transfer from humans with impaired/not impaired cognitive flexibility could substantially affect this behavioral response in mice in the context of obesogenic versus standard diet. Mice were pretreated with an antibiotic cocktail and later received a gut microbiota transplant from human subjects. The transferred microbiota was maintained in mice for seven weeks. Afterward, behavioral tests were performed to evaluate different cognitive responses, locomotor activity, anxiety-like, and depression-like behaviors. Antibiotic treatment significantly impaired short-term memory in mice, as previously reported. Furthermore, mice that received microbiota from high and low cognitive flexibility subjects modified their short-term and long-term memory performance depending on the diet exposure. Slight changes were observed in the locomotor activity, primarily in the high-fat diet-fed antibiotic-treated mice, and no significant alterations were observed in anxiety-like or depressive-like behaviors. In summary, this study shows that gut microbiota is a major contributor to cognitive flexibility, which may open novel therapeutic strategies for combating loss of eating control and related metabolic co-morbidities.
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Special issue on "Brain-body communication in health and diseases".
Bidirectional interaction between the brain and the peripheral organs plays a key role in homeostasis in the body. Abnormalities in brain-body communication potentially leads to a number of brain diseases, including psychiatric and neurodegenerative disorders. For example, dysbiosis of gut microbiota and altered levels of microbes-derived compounds plays an important role in the pathophysiology of a number of psychiatric disorders and neurodegenerative disorders. Furthermore, depression is the most common psychiatric symptom in patients with physical disorders, including pain and cardiovascular diseases. This special issue brings together current information on the brain-body communication in health and diseases.
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Optimized oxygen therapy improves sleep deprivation-induced cardiac dysfunction through gut microbiota.
Adequate sleep is of paramount importance for relieving stress and restoring mental vigor. However, the adverse physiological and pathological responses resulting from sleep insufficiency or sleep deprivation (SD) are becoming increasingly prevalent. Currently, the impact of sleep deficiency on gut microbiota and microbiota-associated human diseases, especially cardiac diseases, remains controversial. Here, we employed the following methods: constructed an experimental sleep-deprivation model in mice; conducted 16S rRNA sequencing to investigate the changes in gut microbiota; through fecal microbiota transplantation (FMT) experiments, transplanted fecal microbiota from sleep-deprived mice to other mice; established an environment with a 30% oxygen concentration to explore the therapeutic effects of oxygen therapy on gut microbiota-associated cardiac fibrosis and dysfunction; and utilized transcriptome data to study the underlying mechanisms of oxygen therapy. The results revealed that: sleep-deprived mice exhibited weakness, depression-like behaviors, and dysfunction in multiple organs. Pathogenic cardiac hypertrophy and fibrosis occurred in sleep-deprived mice, accompanied by poor ejection fraction and fractional shortening. 16S rRNA sequencing indicated that sleep deprivation induced pathogenic effects on gut microbiota, and similar phenomena were also observed in mice that received fecal microbiota from sleep-deprived mice in the FMT experiments. The environment with a 30% oxygen concentration effectively alleviated the pathological impacts on cardiac function. Transcriptome data showed that oxygen therapy targeted several hypoxia-dependent pathways and inhibited the production of cardiac collagen. In conclusion, these results demonstrate the significance of sufficient sleep for gut microbiota and may represent a potential therapeutic strategy, where the oxygen environment exerts a protective effect on insomniacs through gut microbiota.