A new study has found that a specific type of bacteria in the gut, called Lactobacillus, can help the body deal with stress and prevent depression and anxiety. The researchers discovered how Lactobacillus interacts with the immune system and the brain to modulate stress responses and mood.
The study, published in the journal Nature Immunology, was conducted by a team of scientists from the University of Virginia School of Medicine and other institutions. They used mice and humans as their subjects and exposed them to chronic social defeat stress (CSDS), a standard test to study stress-related disorders.
They found that some mice and humans were more resilient to CSDS than others, meaning that they did not show signs of depression or anxiety after the stress exposure. They also found that the resilient mice and humans had higher levels of Lactobacillus in their gut microbiota, the community of microorganisms that live in the digestive tract.
Lactobacillus is a type of probiotic, or beneficial bacteria, that is found in fermented foods and yogurt. It has been shown to have various health benefits, such as improving digestion, immunity, and metabolism. The new study suggests that it can also have a positive impact on mental health by enhancing stress resilience.
How Lactobacillus works
The researchers further investigated how Lactobacillus affects the stress response and mood. They found that Lactobacillus interacts with a specific type of immune cell in the gut, called gamma delta T cells (γδ T cells). These cells produce a protein called interferon-gamma (IFNγ), which regulates stress-related behaviors and inflammation.
The researchers showed that Lactobacillus stimulates γδ T cells to produce more IFNγ, which in turn modulates the gut microbiota and reduces inflammation. This creates a positive feedback loop that helps the body cope with stress and maintain a balanced mood.
The researchers also found that Lactobacillus influences the brain through the serotonin system. Serotonin is a neurotransmitter that is involved in mood, emotion, and cognition. It is produced by a type of brain cell called tryptophan hydroxylase 2 (TPH2) in the dorsal raphe nucleus (DRN), a region that is implicated in depression and anxiety.
The researchers showed that Lactobacillus increases the expression of TPH2 and the production of serotonin in the DRN. This enhances the communication between the gut and the brain and improves the mood and behavior of the stressed mice and humans.
Implications and future directions
The study reveals a novel mechanism by which Lactobacillus can help the body and the brain deal with stress and prevent depression and anxiety. It also opens the door to new therapies that target the gut microbiota, the immune system, and the serotonin system to treat stress-related disorders.
The researchers plan to further explore the role of Lactobacillus and other gut microbes in stress resilience and susceptibility. They also hope to translate their findings into clinical applications that can benefit people who suffer from stress, depression, and anxiety.