F. prausnitzii depletion and reduced L-arginine biosynthesis are consistent features of insomnia that drive elevated cortisol via the POMC-ACTH-cortisol axis, and administration of either F. prausnitzii or L-arginine restores sleep and normalizes corticosterone levels in a mouse model.
Key Findings
Results
F. prausnitzii was consistently depleted in both primary insomnia and post-COVID insomnia patients compared to controls.
The study integrated metagenomic sequencing from 171 individuals across three groups: primary insomnia, post-COVID insomnia, and healthy controls.
F. prausnitzii depletion was identified as a consistent feature shared across both insomnia subtypes.
Metagenomic sequencing was used to characterize gut microbial composition across all groups.
The finding was supported by functional pathway analysis in addition to taxonomic profiling.
Results
Reduced L-arginine biosynthesis was a consistent microbial pathway finding in both insomnia subtypes.
L-arginine biosynthesis reduction was identified across both primary insomnia and post-COVID insomnia cohorts.
Functional pathway analysis of metagenomic data was used to identify this metabolic deficit.
Genomic and in vitro analyses confirmed that F. prausnitzii is a key microbial contributor to L-arginine production.
Reduced L-arginine biosynthesis co-occurred with elevated cortisol levels in insomnia patients.
Results
Insomnia patients exhibited elevated cortisol levels alongside gut microbial dysbiosis.
Elevated cortisol was identified as a consistent feature accompanying F. prausnitzii depletion and reduced L-arginine biosynthesis in insomnia subjects.
Both primary insomnia and post-COVID insomnia subtypes showed this pattern of elevated cortisol.
The cortisol elevation was associated with dysregulation of the POMC-ACTH-cortisol axis.
This endocrine finding was observed in the human cohort of 171 individuals.
Results
Administration of F. prausnitzii in a chronic mild stress mouse model restored sleep duration and normalized corticosterone levels.
A chronic mild stress mouse model was used for preclinical validation.
F. prausnitzii administration restored sleep duration in stressed mice.
Corticosterone levels were normalized following F. prausnitzii treatment.
F. prausnitzii treatment also reversed stress-induced gut dysbiosis in the mouse model.
Results
L-arginine administration in the chronic mild stress mouse model restored sleep duration, normalized corticosterone levels, and reversed gut dysbiosis.
Direct administration of L-arginine recapitulated the beneficial effects seen with F. prausnitzii administration.
Sleep duration was restored in stress-exposed mice treated with L-arginine.
Corticosterone levels were normalized following L-arginine treatment.
Stress-induced gut dysbiosis was reversed by L-arginine administration.
These mechanistic findings implicate the POMC-ACTH-cortisol axis as a key target of L-arginine action.
These mechanistic analyses were conducted to explain how gut-derived L-arginine modulates sleep through endocrine signaling.
Results
F. prausnitzii was confirmed as a key microbial contributor to L-arginine production through genomic and in vitro analyses.
Both genomic analysis and in vitro experiments were used to validate F. prausnitzii's role in L-arginine biosynthesis.
This confirmation links the observed microbial depletion in insomnia patients to the reduced L-arginine levels detected via pathway analysis.
The finding positions F. prausnitzii as a functionally relevant bacterium in the gut-brain axis through metabolite production.
What This Means
This research suggests that a specific gut bacterium called Faecalibacterium prausnitzii plays an important role in sleep health by producing an amino acid called L-arginine. The study examined the gut bacteria of 171 people, including those with common insomnia, insomnia following COVID-19 infection, and healthy individuals. In both types of insomnia, F. prausnitzii was found to be reduced, and the body's ability to produce L-arginine was diminished. At the same time, these individuals had elevated levels of the stress hormone cortisol, which is known to interfere with sleep.
To understand the connection, the researchers conducted experiments in mice subjected to chronic stress, which disrupts sleep similarly to insomnia in humans. When these mice were given either F. prausnitzii or L-arginine directly, their sleep returned to normal, their stress hormone levels normalized, and the imbalances in their gut bacteria were reversed. The study found that L-arginine works by dialing down a hormonal stress pathway — specifically by reducing the activity of a gene called POMC and reducing the hormone signal (ACTH) that tells the body to release cortisol.
This research suggests that the gut microbiome communicates with the brain through metabolites like L-arginine to regulate sleep, and that disruptions in this communication — caused by loss of beneficial bacteria like F. prausnitzii — may contribute to insomnia by keeping the body's stress hormone system overactive. These findings open a potential avenue for treating insomnia by targeting gut bacteria or supplementing with L-arginine, though further research in humans would be needed to confirm safety and effectiveness.