A 24‑hour fast can prime the intestines to recover from radiation damage, but only when a specific gut bacterium is present, researchers at The University of Texas MD Anderson Cancer Center have shown. In a preclinical study published in the Proceedings of the National Academy of Sciences, the team uncovered how fasting and a beneficial microbe cooperate to activate the body’s innate tissue‑repair pathways.
The discovery could lead to new strategies for protecting healthy tissue during cancer treatment. By enhancing the intestine’s ability to rebound after radiation exposure, clinicians may be able to lessen serious side effects and potentially make radiation therapy safer and more effective.
The research was led by Helen Piwnica‑Worms, Ph.D., professor of Experimental Radiation Oncology, and Kunal Rai, Ph.D., professor of Genomic Medicine.
“Fasting helps prepare intestinal cells to respond more quickly and effectively after injury, almost like training the cells with an emergency preparedness plan,” Piwnica‑Worms said. “This study helps explain how that plan is organized and identifies a key bacterium involved in coordinating the response.”
Why Radiation Therapy Can Damage the Intestines
Radiation therapy is a common treatment for abdominal cancers, including pancreatic, colorectal, and gynecologic malignancies. While radiation destroys cancer cells, it also harms nearby healthy tissue. The small intestine is especially vulnerable because its delicate lining is highly sensitive to radiation.
When this protective lining becomes damaged, patients may experience nausea, diarrhea, and infections. Severe injuries can lead to life‑threatening complications and may limit the amount of radiation oncologists can safely deliver.
Previous work from the Piwnica‑Worms Laboratory demonstrated that fasting before radiation exposure helped the intestines recover afterward. However, the underlying mechanisms were unclear.
How a 24‑Hour Fast Activates Gut Repair
The investigators found that a day without food increased the abundance of the beneficial bacterium Akkermansia muciniphila (AKK) in the small intestine. AKK produces the short‑chain fatty acid propionate, which works together with other fasting‑induced metabolic changes to modify histone proteins that package DNA.
These histone modifications make portions of the genome more accessible, enabling cells to turn on genes involved in tissue regeneration. During fasting, a population of intestinal cells carrying these repair programs expands, effectively preparing the gut for potential injury.
When radiation later strikes, the pre‑conditioned cells can proliferate and rebuild the damaged intestinal lining more efficiently.
One Gut Bacterium Proves Essential for Recovery
To test AKK’s role, the researchers selectively removed the bacterium from the mice. In its absence, fasting no longer conferred the regenerative benefits. Restoring AKK together with fasting revived the protective response, indicating that neither component alone is sufficient.
These results suggest that fasting, in concert with AKK, re‑programs intestinal cells before radiation exposure, placing them in a state that supports rapid recovery after damage.
By linking nutrition, gut microbiota, and cellular regeneration, the study points to a potential new avenue for protecting healthy organs during cancer therapy. The findings may also apply to other rapidly dividing tissues, such as bone marrow, that are vulnerable to treatment‑related injury.
Could Gut Bacteria Make Cancer Treatment Safer?
The work remains at the preclinical stage. Further studies are needed to confirm that the same protective mechanism operates in humans and that it can be safely harnessed to improve outcomes for patients undergoing abdominal radiation.
Researchers are exploring ways to mimic the fasting‑AKK effect without requiring patients to abstain from food. Potential approaches include delivering beneficial bacteria or their metabolites, such as propionate, directly to the gut.
“Fasting is not always practical for cancer patients, and this work supports several other potential ways to enhance recovery after treatment,” Rai noted. “Whether through dietary interventions, targeted microbes or their metabolites, the goal is to help repair healthy tissue more effectively while patients receive the cancer therapies they need.”
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