Researchers working with animal models traditionally look at the brain, but recent studies are increasingly focused on a different area—the gut, or microbiome, which is emerging as an important factor in human health.
It’s a fertile area of study: The human gut is home to more than 500 different types of bacteria, which line the entire digestive system and play an important role in digestion, metabolism, disease, immunity, mood, and the workings of the nervous system and brain.
Recently, several scientific studies have looked at the microbiome—the mix of bacteria and other microorganisms in the gut—to find clues to other biological manifestations in the body, including diseases, disorders, allergies, and even endurance.
Disrupted Gut Microbiome Linked to Breast Cancer Metastization
The gut microbiome has already been linked to colon cancer, but new research from the University of Virginia has also found a connection between the microbiome and the spread of breast cancer.
Mouse models of the most common type of breast cancer, hormone receptor positive (HR+), were treated with antibiotics to disrupt the microbiome, then were tested for both inflammation and the spread of breast cancer cells.
The disruption in the microbiome caused inflammation in the mice, which enabled tumor cells to more easily metastasize to the blood and lungs.
New Evidence That Parkinson’s Disease Starts in the Gut
A study at Johns Hopkins University School of Medicine using a new mouse model of Parkinson’s disease has found that Parkinson’s can begin in the gut and spread to the brain via the vagus nerve.
The research team injected pathologic α-synuclein, one of the hallmarks of Parkinson’s, into the gut of mouse models. Within a month the pathologic α-synuclein had spread to the lowest part of the brainstem, and within three months it had reached beyond the brainstem to the amygdala, hypothalamus, and prefrontal cortex.
By seven months it had appeared in the hippocampus, striatum, and olfactory bulb, and the mice were showing signs of depression, anxiety, olfactory dysfunction, and cognitive deficits, all of which are common symptoms of Parkinson’s disease.
A Gut Bacteria That Alleviates Food Allergies
Scientists at Boston Children’s Hospital and Brigham and Women’s Hospital discovered that babies and children with food allergies are missing certain species of gut bacteria. When they gave these missing bacteria to mice, the microbes protected the mice from food allergies.
Scientists were able to isolate two groups of Clostridiales or Bacteroidetes microbes that resulted in food allergy resistance. Some members of the team are now setting up a human trial to test the approach to treat humans with peanut allergies.
Gut Bacteria Can Contribute to Autistic Behavior
Researchers at Caltech transferred gut microorganisms from children with Autism Spectrum Disorder (ASD) into mice, which caused the mice to exhibit behaviors characteristic of ASD, including socializing less with other mice, vocalizing less, and engaging in repetitive actions.
In addition to behavioral changes, the mice colonized with intestinal microbiota from ASD humans also showed a reduction in two metabolites: 5-amniovaleric acid (5AV) and taurine. In further tests, researchers treated a strain of mice, BTBR, that naturally display autistic behaviors, with 5AV and taurine. The BTBR mice showed a decreases in ASD-type behaviors.
The research opens the possibility that ASD may be treated with therapies that target the gut rather than the brain.
Replenishing an Aging Gut Could Revive the Immune System
A study at the Babraham Institute at Cambridge found that transplanting gut bacteria from young mice to old mice resulted in a significant boost in the immune systems of the older mice, partly ameliorating the natural age-related drop in immunity.
A Bacteria That Boosts Endurance
In a study conducted at Harvard Medical School, researchers identified a strain of bacteria commonly found in long-distance runners, especially after running a marathon.
Researchers found that putting this bacteria, called Veillonella, in the colons of mice boosted their performance on a treadmill exertion test by 13%.
Jonathan Scheiman, who led the study, hopes to test Veillonella in humans with the goal of creating a probiotic that improves athletic endurance.
As researchers continue to explore this rich new area of discovery, they’ll no doubt continue to uncover new secrets the microbiome holds.
