According to a story from The New York Times, a new wave of research is starting to reveal the close connection between the human gut microbiome and the brain. Some scientists are also finding some remarkable results that suggest that the microbiome could influence the course of human diseases and even our behavior. Some studies are beginning to reveal that the microbiome may be connected to a number of human diseases that affect the brain, such as Alzheimer’s, depression, autism, Parkinson’s disease, and schizophrenia.
What is the Microbiome?
The cells that make up your body all comprise a single organism, but there are just as many cells in your body that are not directly part of the you. They are small, single celled microbes, often bacteria. The fact is, microorganisms reside in almost every nook and cranny of the human body and may include not just bacteria but viruses, fungi, and protists. In a sense, the human body is its own unique ecosystem. Most of them have little impact on your health and body, but others can be beneficial and aid in critical body processes like digestion. However, the latest research may change the way that we understand the impact of the microbiome and particularly the gut microbiome, where hundreds of species of bacteria reside.
Microbiome Discoveries
Dr. Sangram Sisodia of the University of Chicago led an experiment in which they gave antibiotics to mice predisposed to Alzheimer’s. The drugs wiped out the gut microbiota of the mice, and as a result the typical clumps of protein that appear in brains of mice with the disease were much reduced in number upon examination. Other research has led Dr. Sisodia to suspect that a couple of different bacteria species could influence the course of the disease.
In another mouse study, feces from mice with a mutation that caused them to eat heavily and get overweight were transplanted into mice who had no gut bacteria. The recipient mice soon began to overeat and gain weight as well. Before receiving the feces, these mice also behaved differently; they often isolated themselves and did not socialize with other mice. This suggests that the microbiome could influence social behavior. A similar study of mice with a mutation that caused them to avoid other mice found that they lacked a common bacteria called Lactobacillus reuteri. When this strain was introduced into the diet, the mice began to socialize. The researchers found that this species releases a compound that sends a nerve signal from the gut to the brain and causes the release of hormones that promote social behavior.
Another study has found the people with autism have a distinctive composition of bacteria in their intestines compared to others. This doesn’t prove that changes to the microbiome are necessarily causing the disorder however.
Other researchers have isolated a single bacteria species that appears to trigger Parkinson’s disease symptoms. The leader of that research is now starting a company that is testing a possible drug that could block the compound released by the bacteria so that it doesn’t reach the nerves and trigger symptoms.
All of these discoveries highlight the fact that there is an intimate connection between the bacteria in our digestive tract and our brains. While continued research is necessary to understand these interactions more clearly, it is obvious that it could lead to a whole new class of therapies that could act on these interactions in order to treat diseases affecting the brain.