Caloric restriction alleviates radiation injuries in a sex‐dependent fashion

Safe and effective regimens are still needed given the risk of radiation toxicity from iatrogenic irradiation. The gut microbiota plays an important role in radiation damage. Diet has emerged as a key determinant of the intestinal microbiome signature and function. In this report, we investigated whether a 30% caloric restriction (CR) diet may ameliorate radiation enteritis and hematopoietic toxicity. Experimental mice were either fed ad libitum (AL) or subjected to CR preconditioning for 10 days and then exposed to total body irradiation (TBI) or total abdominal irradiation (TAI). Gross examinations showed that short-term CR pretreatment restored hematogenic organs and improved the intestinal architecture in both male and female mice. Intriguingly, CR preconditioning mitigated radiation-induced systemic and enteric inflammation in female mice, while gut barrier function improved in irradiated males. 16S rRNA high-throughput sequencing showed that the frequency of pro-inflammatory microbes, including Helicobacter and Desulfovibrionaceae, was reduced in female mice after 10 days of CR preconditioning, while an enrichment of short-chain fatty acid (SCFA)-producing bacteria, such as Faecalibaculum, Clostridiales, and Lactobacillus, was observed in males. Using fecal microbiota transplantation (FMT) or antibiotic administration to alter the gut microbiota counteracted the short-term CR-elicited radiation tolerance of both male and female mice, further indicating that the radioprotection of a 30% CR diet depends on altering the gut microbiota. Together, our findings provide new insights into CR in clinical applications and indicate that a short-term CR diet prior to radiation modulates sex-specific gut microbiota configurations, protecting male and female mice against the side effects caused by radiation challenge.