Gut bacteria is now proved to interact with the central nervous system.
A new study by researchers at Harvard University Medical School, published today in Nature, has uncovered new pathways mediating inflammation in Multiple Sclerosis (MS), involving molecules produced by gut bacteria breaking down food, which could lead to new treatment options for patients.
In MS, the immune system attacks a protein called myelin which normally covers nerve cells in the brain and spinal cord, allowing signals to pass through them. When this occurs, the normal flow of nerve impulses is interrupted, resulting in the wide range of symptoms that people with MS experience.
“We essentially discovered a remote control by which the gut flora can control what is going on at a distant site in the body, in this case the central nervous system,” said Dr Francisco Quintana, lead author of the paper from Brigham and Women’s Hospital.
Two types of neural cells; microglia and astrocytes are principally involved in controlling inflammation and neurodegeneration in the central nervous system which comprises the brain and spinal cord, with communication between the two regulating pro-inflammatory and neurotoxic activities. The new study used a mouse model of MS to show that two proteins TGF alpha and VEGF-B produced by the microglia control these processes. TGF alpha binds to receptors on the astrocytes and stops them from causing inflammation whereas binding of VEGF-B to astrocytes increases inflammation and worsens the MS-like syndrome in the mouse models.
The study also built on previous work by the same group and showed that the production of TGF alpha and VEGF-B by microglia was controlled by binding of small molecules to a receptor on the microglia called AHR. Crucially, these small molecules are produced by natural gut bacteria breaking down a common dietary amino acid called tryptophan, found in large quantities in eggs, chocolate and dairy products. Binding of these tryptophan metabolites to the AHR receptor on the microglia blocked the production of inflammatory proteins and promoted the production of anti-inflammatory proteins, showing for the first time that dietary metabolite molecules produced by gut bacteria travel through the body and directly affect nerve cells in the brain and spinal cord.
Dr. Bruce Bebo, Executive Vice President of Research at the National MS Society, which part-funded the study said: “It is complicated to dissect when this pathway is acting positively to suppress inflammation and promote repair or negatively, causing inflammation and blocking repair. This new research increases understanding these pathways and is likely to lead to strategies and treatments which can slow down and even stop disability in MS.”
|Read on: Researchers Uncover Gut Bacteria’s Potential Role In Multiple Sclerosis|