In the IBS-Std rats, the not significant increase of the mitochondrial specific scavengers of ROS (SOD 2 and PrxIII), along with the higher presence of oxidatively modified purines in the D-loop region of mtDNA, a hot spot for the damage [27], appeared to be indicative of the inability of these animals to set up an efficacious antioxidant response inside the mitochondria. This evidence concerns the gene PRDX3 and irritable bowel syndrome.