Fasting Activates Gut Microbe AKK to Prime Intestinal Repair After Radiation Injury
Key Insights
A 24-hour fast increases the gut bacterium Akkermansia muciniphila (AKK), which produces propionate (search) that primes intestinal cells for regeneration after radiation damage.
Preclinical research from MD Anderson Cancer Center shows fasting and AKK work together to modify histones, exposing genes linked to tissue repair before injury occurs.
Removing AKK eliminated the protective benefit of fasting, and restoring the bacterium alone was insufficient — both fasting and AKK were required for the regenerative response.
A preclinical study from The University of Texas MD Anderson Cancer Center has identified a gut bacterium that, when combined with short-term fasting, helps prepare the small intestine to regenerate more effectively after radiation damage. The findings, published in Proceedings of the National Academy of Sciences, were co-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."
The Clinical Challenge of Radiation-Induced Intestinal Injury
Radiation therapy is a common treatment for abdominal cancers, including pancreatic, colorectal, and gynecologic cancers (search). However, the small intestine contains rapidly renewing cells that are especially vulnerable to radiation. When the intestinal lining is injured, patients can experience nausea, diarrhea, and infection. Severe damage can lead to life-threatening complications, which may restrict the amount of radiation doctors can safely deliver.
Earlier preclinical work from the Piwnica-Worms Laboratory had demonstrated that fasting before treatment improved intestinal recovery after radiation, but the biological mechanisms behind this effect were not fully understood.
AKK and the Fasting-Microbiome-Chromatin Axis
The researchers found that fasting for 24 hours increased the abundance of Akkermansia muciniphila (AKK) in the small intestine. AKK produces propionate (search), a small molecule created when microbes process nutrients. Propionate worked alongside other metabolic changes caused by fasting to modify histones inside intestinal cells — proteins that package DNA, much like spools organizing long threads. Small chemical tags added to these proteins can loosen or tighten access to particular genes without changing the underlying genetic code.
In this case, the tags helped expose genes connected with tissue regeneration. A group of intestinal cells that accumulated during fasting appeared to carry these repair programs in a more accessible state, leaving them prepared to respond once injury occurred. After radiation exposure, those cells multiplied and helped rebuild the intestinal lining.
Both Fasting and AKK Are Required
To determine whether AKK was simply present during the response or actually necessary for it, the researchers selectively removed the bacterium. The protective benefit associated with fasting then disappeared. Restoring AKK by itself was not enough — the regenerative response returned only when the bacterium was reintroduced together with fasting, indicating that the microbial and metabolic changes worked as a combined system.
The findings suggest that fasting alters intestinal cells before radiation arrives rather than merely helping them recover afterward. By changing gut microbes, metabolism, and access to regeneration genes, the process may allow repair to begin more rapidly once tissue is damaged.
Toward Clinical Translation Without Fasting
Fasting can be physically difficult or medically inappropriate for people undergoing cancer therapy. For that reason, the researchers are interested in reproducing its protective effects without requiring patients to stop eating. Possible approaches could include treatments based on AKK, propionate (search), or other metabolites involved in the repair pathway. Dietary interventions might offer another way to influence the same biological response.
"Fasting is not always practical for cancer patients, and this work supports several other potential ways to enhance recovery after treatment," Rai said. "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."
Future studies will need to determine whether the pathway operates similarly in patients receiving abdominal radiation. Researchers also want to investigate whether it could protect other rapidly dividing tissues, including bone marrow, from damage caused by cancer treatment. If the results are consistent, the approach could potentially be tested in clinical trials for patients receiving abdominal radiation.
This research was supported by the National Cancer Institute (NCI) within the National Institutes of Health (NIH) and the Cancer Prevention and Research Institute of Texas (CPRIT).