A team of researchers* led by associate professor of environmental health sciences (ENHS) Dr. Saurabh Chatterjee (Arnold School of Public Health; University of South Carolina) have published the first study to link the gastrointestinal disturbances (e.g., bloating, flatulence, indigestion) of Gulf War Illness (GWI) with changes in the intestinal microbiota. This connection potentially explains both the gastrointestinal inflammation and the neurological abnormalities (e.g., impairments to cognition, memory, learning) that define GWI. GWI exposures alter the microbiome (i.e., bacterial content in the gut). The affected microbiota then produce endotoxins, which pass through a thinned lining of the gut (i.e., leaky gut) and into the blood where they circulate throughout the body. These compounds trigger an inflammatory response that, in turn, initiates several neurological abnormalities commonly observed in GWI. These findings open up new treatment options that may improve both gastrointestinal and neurological symptoms among soldiers and veterans with GWI.
[Photo: Dr. Saurabh Chatterjee]
Characterized by symptoms such as chronic headache, cognitive difficulties, debilitating fatigue, widespread pain, respiratory problems, sleep problems, gastrointestinal problems, and other unexplained medical abnormalities, GWI continues to affect 25-32 percent of the 700,000 U.S. veterans who served in the 1990-1991 Persian Gulf War. Twenty years of scientific research has traced these symptoms to Gulf War chemical exposures and the drugs taken during deployment that were meant to prevent or counteract these exposures. However, the vast majority of these studies have focused on neurological effects (rather than gastrointestinal), and none of them have successfully revealed the pathways through which GWI affects the brain.
The present study, published in PLOS ONE, looked at how the various exposures experienced by Gulf War veterans might have changed the microbiome. “Humans and animals have specific types of bacteria that help aid various physiological processes, including digestion, absorption, immunity and gut integrity, and when external factors change the bacterial composition in our digestive systems, we have problems,” says Dr. Chatterjee. “Obesity, metabolic syndrome, inflammatory bowel syndrome, and liver disease have already been linked with changes in bacterial composition of the gut.”
The scientists observed that not only did exposures to the suspected GWI agents lead to inflammation in the intestines, but to neuroinflammation as well. Changes to the frontal cortex, which controls many physical activities, alerted them to the connection, which they investigated further.
“Usually, the gut is very selective about letting only certain elements from what we eat and drink into our blood — thanks to good bacteria,” explains Dr. Chatterjee. “But when the composition changes due to an increase in certain bad bacteria, this causes disruption to the mucosal lining of the intestinal walls — leading more intestinal contents to leak into the blood.”