The gut microbiota, consisting of trillions of microorganisms residing in the intestines, has long been known to influence various aspects of human health, from digestion to immune function. However, its role in mental health has only recently gained attention. The consortium led by Zhang, Chen, Xu, and their colleagues has now provided compelling evidence that disturbances in this microbial community can provoke depression-related symptoms by disrupting key cellular processes in the brain. By focusing on adolescent rats, the study importantly highlights a developmental window when the brain is particularly susceptible to environmental and physiological stressors, emphasizing the potential vulnerability of young individuals to microbiota-related mental health issues.

Central to this discovery is the identification of the lysine-regulated mTOR (mechanistic Target of Rapamycin) autophagy pathway as a mediator between gut dysbiosis and depression-like behavior. The mTOR pathway is a well-characterized regulator of cell growth, metabolism, and autophagy—a process by which cells degrade and recycle damaged components to maintain homeostasis. Lysine, an essential amino acid, emerges as a pivotal modulator in this pathway, linking alterations in the gut microbiome to functional changes in neuronal autophagy. The disruption of this finely tuned mechanism appears to contribute to synaptic dysfunction and neuroinflammation, hallmarks of depressive disorders.

This study employed an integrative approach combining advanced microbiome sequencing, behavioral assays, and molecular biology techniques to unravel the complex interactions involved. The researchers induced gut microbiota dysbiosis in adolescent rats through dietary interventions and antibiotic treatments, observing significant shifts in microbial diversity and composition. These animals subsequently exhibited marked depression-like behaviors, including anhedonia and increased immobility in forced swim tests. Such behavioral phenotypes provide robust models for human depressive symptoms, lending translational value to the findings.

On a molecular level, the research team measured the expression of critical components in the mTOR autophagy pathway, noting significant downregulation associated with dysbiotic states. Importantly, lysine supplementation was able to partially rescue these defects, normalizing autophagy flux and alleviating depressive behaviors. This points to dietary or pharmacological modulation of lysine metabolism as a promising therapeutic avenue. The interventional aspect of the study underscores the reversible nature of microbiome-induced behavioral changes, which has profound implications for developing targeted treatments for depression.

From a neuroscience perspective, these findings reveal novel insights into how peripheral signals mediated by the gut microbiota can influence central nervous system function. The study suggests that microbial metabolites or immune factors released during gut dysbiosis may alter lysine availability or metabolism, thereby impacting neuronal signaling cascades governed by mTOR and autophagic pathways. These cellular changes contribute to synaptic plasticity deficits, which are widely recognized as underlying mechanisms in mood disorders.

Importantly, the timing of exposure to gut microbiota alterations during adolescence highlights a critical period of neurodevelopmental vulnerability. Adolescence represents a phase characterized by profound synaptic pruning and maturation of neural circuits involved in emotion regulation. Disruptions during this time are often linked to the emergence of psychiatric illnesses. This study positions gut microbiota as a potent environmental factor capable of perturbing these developmental trajectories, offering a new dimension to our understanding of depression pathogenesis in youth.

The implications of this research extend beyond depression, suggesting that gut microbiota dysbiosis may play a role in a broad spectrum of neuropsychiatric conditions where aberrant mTOR signaling and autophagy dysfunction are implicated, such as anxiety disorders, schizophrenia, and neurodegenerative diseases. This opens new possibilities for microbiome-targeted interventions as part of holistic neuropsychiatric treatment strategies.

Methodologically, the study’s sophisticated use of multi-omics analyses, including metabolomics and transcriptomics, allowed for a comprehensive mapping of biochemical changes triggered by gut microbiota alterations. This integrative framework enabled the identification of key molecular players within the lysine-regulated mTOR autophagy axis, bridging the gap between systemic gut changes and localized brain effects. Such detailed molecular delineation is critical for the rational design of future therapeutics.

Furthermore, these findings highlight the importance of dietary factors and gut microbiota integrity in mental health maintenance, supporting growing evidence that nutrition and microbiome health are intricately linked to psychiatric well-being. Lysine, as an essential amino acid typically obtained from diet, serves as a clear example of how nutritional status may intersect with microbial and neuronal pathways to influence mood and behavior.

Critically, this study challenges the traditional view that depressive disorders are primarily brain-centric, reinforcing the concept of a bidirectional gut-brain axis where peripheral physiological systems exert considerable influence on mental states. Therapeutic targeting of the microbiome or its metabolic pathways, such as the lysine-mTOR-autophagy cascade, may herald a new era of personalized psychiatry rooted in systems biology.

While these findings are groundbreaking, the authors emphasize the need for further research to validate these mechanisms in humans and to explore the translational relevance of lysine supplementation or probiotic strategies in clinical settings. Longitudinal studies tracking gut microbiota composition and depression onset in adolescents could provide critical data to support these preclinical insights.

In summary, this pioneering research intricately connects gut microbiota dysbiosis with depression-like behavior through the lysine-regulated mTOR autophagy pathway in adolescent rats. By elucidating this complex biochemical dialogue, it advances our understanding of the gut-brain axis and offers promising new targets for therapeutic intervention in depression and related mental health disorders, particularly during vulnerable developmental stages.

Subject of Research: The study investigates how gut microbiota dysbiosis influences depression-like behaviors in adolescent rats through the lysine-regulated mTOR autophagy pathway.

Article Title: Gut microbiota dysbiosis drives depression-like behavior in adolescent rats via lysine-regulated mTOR autophagy pathway.

Article References:
Zhang, J., Chen, F., Xu, X. et al. Gut microbiota dysbiosis drives depression-like behavior in adolescent rats via lysine-regulated mTOR autophagy pathway. Transl Psychiatry (2026). https://doi.org/10.1038/s41398-026-04095-2

Image Credits: AI Generated

DOI: https://doi.org/10.1038/s41398-026-04095-2

Sleep disorders afflict vast populations globally, manifesting in diverse forms such as chronic insomnia, obstructive sleep apnea, and circadian rhythm disruptions. These conditions exact a profound toll on physiological health, cognitive capacity, and emotional resilience. Historically, sleep research has prioritized central nervous system mechanisms; however, this landmark review underscores the critical influence of peripheral systems, particularly gut microbiota, in modulating brain function and behavior. The convergence of microbiome science with sleep physiology heralds a transformative era whereby digestive ecosystems are recognized as active contributors to sleep regulation rather than passive participants.

The gut microbiome—comprising an immense and dynamic population of bacteria, viruses, and fungi—engages in continuous bidirectional communication with the brain via neural, immune, and endocrine routes. Central among these is the vagus nerve, which enables rapid neuronal crosstalk, while circulating immune factors and microbial metabolites serve as systemic messengers capable of traversing the blood-brain barrier. Professor Lu emphasizes that aberrations in microbial community structure, or dysbiosis, consistently correlate with sleep disruptions, suggesting that altered gut ecology is both a marker and a mediator of sleep pathology.

Human clinical investigations alongside controlled animal studies reveal compelling patterns: individuals suffering from chronic insomnia exhibit markedly reduced microbial diversity and deficits in bacterial families known for beneficial metabolic functions. Similarly, patients diagnosed with obstructive sleep apnea display diminished alpha-diversity, with microbial signatures correlating directly with disease severity measures such as apnea-hypopnea indices and oxygen saturation. These findings not only establish a robust associative framework but also hint at mechanistic underpinnings.

At the molecular interface of gut-brain communication, microbial metabolites emerge as critical modulators. Short-chain fatty acids (SCFAs), particularly butyrate, synthesized by bacterial fermentation of dietary fibers, demonstrate neuroprotective and anti-inflammatory properties that preserve sleep integrity. Empirical data from clinical trials suggest that butyrate supplementation enhances sleep quality in inflammatory bowel disease patients, while animal experiments confirm its capacity to attenuate inflammation and cognitive deficits induced by sleep deprivation. Altered bile acid profiles further delineate gut microbiome involvement, with chronic insomnia linked to elevated primary bile acids and depleted secondary bile acids, implicating a dysregulated microbiota-bile acid axis that may exacerbate cardiometabolic comorbidities associated with poor sleep.

The production of neurotransmitters by gut microbes elucidates additional pathways of influence. Select strains of Lactobacillus and Bifidobacterium harbor genes responsible for generating gamma-aminobutyric acid (GABA), the principal inhibitory neurotransmitter central to sleep initiation and maintenance. Electroencephalographic evidence corroborates that both endogenous and exogenous GABA can modulate cortical activity, reinforcing the gut’s neurochemical impact. Moreover, the gut is the predominant extraneural site of serotonin synthesis, with more than 90% of the body’s serotonin produced within the intestinal tract. Serotonin’s rhythmic fluctuations align with sleep-wake cycles, and disturbances in its metabolism—linked to gut microbiota alterations—may precipitate circadian misalignment and sleep deficits. The gastrointestinal tract also paradoxically serves as a major melatonin reservoir, with concentrations vastly exceeding plasma levels, further emphasizing the gut’s centrality in circadian biology.

Delineating the microbial landscapes characteristic of specific sleep disorders, the review synthesizes extensive data sets revealing both unique and overlapping microbial taxonomic shifts. Chronic insomnia studies involving thousands have documented consistent declines in Ruminococcaceae species, bacterial groups implicated in bile acid metabolism and systemic inflammation. Obstructive sleep apnea research echoes this narrative, where diminished levels of these commensals associate with hypoxia-induced gut inflammation. Investigations into circadian disruption conditions, especially in shift workers, reveal compositional microbiota oscillations tied to altered metabolic pathways that favor glucose intolerance, signifying a link between microbiota and metabolic sequelae of sleep loss. Likewise, rarer disorders such as narcolepsy and REM sleep behavior disorder exhibit discrete microbial signatures, some predictive of neurodegenerative progression, offering novel biomarker avenues.

Sleep disturbances frequently co-occur with neuropsychiatric disorders, including major depressive disorder, anxiety, autism spectrum disorder, and Parkinson’s disease. The review highlights commensurate shifts in gut microbial genera like Blautia, Coprococcus, and Dorea correlating with sleep parameters in depression, as well as decreased Faecalibacterium and Agathobacter in autistic children with sleep impairments. Parkinson’s disease subtypes characterized by early sleep disturbances similarly demonstrate gut dysbiosis, marked by elevated Escherichia coli and Akkermansia muciniphila alongside diminished SCFA producers, underscoring shared pathogenic routes.

Translating mechanistic elucidations into therapeutic potentials, the review appraises emerging microbiota-targeted interventions. Probiotic administration manifests tangible improvements in sleep metrics across chronic insomnia, Parkinson’s disease, and substance use disorders, with strains such as Lactobacillus plantarum PS128 and Bifidobacterium breve CCFM1025 demonstrating modulation of neurophysiological markers including delta power during deep sleep and attenuation of hypothalamic-pituitary-adrenal axis hyperactivity. Complementary animal research substantiates these findings, noting enhancements in non-rapid eye movement sleep duration and reductions in anxiety-like behaviors consequent to probiotic supplementation.

Prebiotics—nondigestible fibers fostering beneficial microbial growth—also show promise in ameliorating sleep disruptions, particularly those induced by circadian misalignment and metabolic disorders. Clinical trials affirm that compounds like partially hydrolyzed guar gum and resistant dextrin improve sleep quality scores, while animal studies suggest mechanisms involving bile acid metabolism and gut barrier integrity. Synbiotics, combining both probiotics and prebiotics, offer synergistic effects, exhibiting notable efficacy in post-acute COVID-19 syndrome and other sleep-compromised populations, enhancing subjective sleep quality and physiological markers in randomized controlled settings.

Fecal microbiota transplantation (FMT) represents a potent, albeit complex, therapeutic frontier. Clinical interventions deploying FMT in chronic insomnia patients with comorbidities have yielded remarkable augmentations in sleep quality and symptom alleviation, accompanied by favorable shifts in gut bacterial populations. Similar benefits extend to fibromyalgia and pediatric autism sufferers, signaling FMT’s expansive potential. Nonetheless, practical constraints—stringent donor screening, procedural standardization, regulatory hurdles—currently restrict widespread FMT application to research contexts and select refractory cases.

This comprehensive synthesis proposes an integrated research framework designed to propel the field forward. The authors advocate a tiered approach beginning with multimodal phenotyping, incorporating neuroimaging modalities alongside robust microbiome and metabolomic profiling. Subsequent tiers focus on biomarker discovery through machine learning-driven multi-omic integration, causal inference employing germ-free animal models and longitudinal human trials, and the rigorous evaluation of microbiota-directed interventions through carefully controlled clinical studies. Harmonization of methodologies and standardization of biomarkers are emphasized as critical to advancing translatability and reproducibility.

Despite promising advancements, the review acknowledges persistent challenges, including interindividual variability in microbiota compositions and responses to interventions, methodological discrepancies across studies, and incomplete long-term safety data for microbiome-targeted therapies. Prioritizing well-powered, standardized clinical trials—particularly targeting conditions with robust microbiome-sleep mechanistic links like chronic insomnia and obstructive sleep apnea—will be imperative. Additionally, elucidating personalized microbial signatures and tailoring interventions accordingly offers an exciting horizon in precision medicine for sleep disorders.

In conclusion, this landmark review firmly establishes the microbiota-gut-brain axis as a central regulator in the complex architecture of sleep physiology and pathology. The identification of shared microbial alterations across a spectrum of sleep disorders accentuates the gut microbiome’s dual roles as both consequence and catalyst of sleep dysfunction. By bridging gaps across disciplines, this work lays a robust foundation for microbiota-based diagnostics and therapeutics, with the potential to revolutionize management strategies for sleep disorders globally. As the nexus of microbiology, neuroscience, and clinical medicine strengthens, the vision of harnessing gut microbiota to restore healthy sleep and enhance brain function draws ever closer to reality.

Subject of Research: People
Article Title: Brain-gut-microbiota interactions in sleep disorders
News Publication Date: 4 November 2025
Web References: https://doi.org/10.61373/bm025i.0128
References: The review article published in Brain Medicine supported by STI2030-Major Projects and the National Natural Science Foundation of China
Image Credits: Lin Lu
Keywords: microbiota-gut-brain axis, sleep disorders, gut microbiome, chronic insomnia, obstructive sleep apnea, circadian rhythm, short-chain fatty acids, bile acids, neurotransmitters, probiotics, fecal microbiota transplantation, sleep regulation