MICROBIOME NEWS: Microbes in the gut could be protective against hazardous radiation exposure. “A new study by scientists at UNC Lineberger Comprehensive Cancer Center and colleagues published Oct. 30, 2020, in Science, showed that mice exposed to potentially lethal levels of total body radiation were protected from radiation damage if they had specific types of bacteria in their gut.
The researchers noted that only an ‘elite’ set of mice had a high abundance of two types of bacteria, Lachnospiraceae and Enterococcaceae, in their guts that strongly countered the effects of the intense radiation. Importantly for humans, these two types of bacteria were found to be abundant in leukemia patients with mild GI symptoms who underwent radiotherapy.
The study showed that the presence of the two bacteria led to an increased production of small molecules known as propionate and tryptophan. These metabolites provided long-term protection from radiation, lessened damage to bone marrow stem cell production, mitigated the development of severe gastrointestinal problems and reduced damage to DNA. Both metabolites can be purchased in some countries as health supplements but there is currently no evidence that the supplements could aid people exposed to intense forms of radiation.
Because radiotherapy that is widely used to treat cancer often leads to GI side-effects, the investigators wanted to understand how their experiments in mice could translate to people. They worked with colleagues at Duke University, Memorial Sloan Kettering and Weill Cornell Medical College, and studied fecal samples from 21 leukemia patients due to receive radiation therapy as part of an arduous stem cell transplant conditioning. The scientists found that patients with shorter periods of diarrhea had significantly higher abundances of Lachnospiraceae and Enterococcaceae than patients with longer periods of diarrhea. These findings correlated closely with the researcher’s findings in mice although Ting cautions that much larger studies are needed to verify these conclusions.
Importantly for potential human use, in mice that were supplemented with Lachnospiraceae, the benefits of cancer radiotherapy were not lessened.