Gut microbiome-derived ammonia modulates stress vulnerability in the host

Area of Science:

• Neuroscience
• Microbiology
• Metabolic Science

Background:

• Ammonia is recognized as a neurotoxic waste product.
• The beneficial roles of endogenous ammonia, particularly from gut microbiota, are largely unexplored.
• Gut-brain axis communication in stress response requires further elucidation.

Purpose of the Study:

• To investigate the beneficial function of endogenous ammonia in host stress vulnerability.
• To explore the link between gut microbial nitrogen metabolism and brain glutamine availability.
• To identify potential therapeutic targets for stress-related disorders.

Main Methods:

• Utilized male mouse models to study chronic stress and its effects on blood ammonia levels.
• Investigated the role of urease-positive gut microbiota, including Streptococcus thermophilus.
• Assessed behavioral changes, brain glutamine levels, and GABAergic function in response to ammonia modulation.
• Examined the therapeutic potential of ammonium chloride (NH4Cl).

Main Results:

• Chronic stress reduced blood ammonia by altering gut urease-positive microbiota.
• Streptococcus thermophilus reversed stress-induced depression-like behaviors.
• Pharmacological inhibition of gut ammonia production increased stress vulnerability.
• Low blood ammonia levels were linked to reduced brain glutamine and cortical GABAergic dysfunction, increasing stress vulnerability.
• Ammonium chloride treatment rescued behavioral and GABAergic deficits in depression models.

Conclusions:

• Gut-derived ammonia plays a beneficial role in host stress buffering by maintaining brain glutamine availability.
• Gut microbiota-derived ammonia influences host emotional behavior through a gut-brain signaling pathway.
• Modulating gut ammonia production presents a potential therapeutic strategy for stress-related disorders and depression.