A new study done at the renowned University of Michigan Medical School in Ann Arbor indicates that the gut microbiome may have a role in the regulator of body temperature, both in health and illness.
Dr. Robert Dickson led the study, which used health record data from patients hospitalized with sepsis. They also experimented with mice, examining the mix of bacteria in the gut, temperature variation, and health outcomes.
Sepsis is a life-threatening infection throughout the body, causing dramatic changes in body temperature. The body temperatures swing widely, with the variation correlated to survival.
“There’s a reason that temperature is a vital sign,” says Dr. Kale Bongers, a clinical instructor in the Department of Internal Medicine, in a statement. “It’s easily measured and tells us important information about the body’s inflammatory and metabolic state.”
The causes of the variation, both in illness and in health, are unknown. “We know that temperature response is important in sepsis, because it strongly predicts who lives and who dies,” said Dickson. “But we don’t know what drives this variation and whether modification to help patients.”
To try to understand the cause of this variation, the team analyzed rectal swabs from 116 patients admitted to the hospital. The patients’ gut microbiota varied widely.
“Arguably, our patients have more variation in their microbiota than they do in their own genetics,” explains Bongers. “Any two patients are more than 99% identical in their own genomes, while they may have literally 0% overlap in their gut bacteria.”
The variation in gut bacteria correlated with temperature trajectories during hospitalization. Bacteria from the Firmicutes phylum had the greatest correlation with fever response. These common bacteria produce metabolic products that enter the bloodstream, where they influence the body’s immune response and metabolism.
“We found that the same kind of gut bacteria explained temperature variation both in our human subjects and in our laboratory mice,” says Dickson. “This gave us confidence in the validity of our findings and gives us a target for understanding the biology behind this finding.”
Healthy mice without a microbiome had lower body temperatures than conventional mice. Treating normal mice with antibiotics also reduced their body temperature.
“While we certainly haven’t proven that changes in the microbiome explain the drop in human body temperature, we think it is a reasonable hypothesis,” said Bongers. “Human genetics haven’t meaningfully changed in the last 150 years, but changes in diet, hygiene, and antibiotics have had profound effects on our gut bacteria.”
Additional research is needed to understand if using the microbiome to manipulate body temperature could affect the outcome for patients with sepsis.
This work is published in the American Journal of Respiratory and Critical Care Medicine.