Metformin improves the impairment of cognitive function caused by total abdominal irradiation via the miR-34a-5p/BDNF/CREB axis.

The gastrointestinal system is of particular importance in radiation biodosimetry because of its constant cell renewal and sensitivity to radiation-induced injury. It has been reported that total abdominal irradiation causes distant cognitive defects in a mouse model. In this study, we demonstrated that metformin alleviated the cognitive dysfunction caused by total abdominal irradiation. No neuropathological changes were observed in hippocampal tissues in control, irradiated, and irradiated plus metformin-treated groups. However, we found that metformin treatment improved the expression of brain-derived neurotrophic factor and the phosphorylation level of cAMP response element-binding in the hippocampus from irradiated mice. Furthermore, our results revealed that metformin treatment reduced the expression of miR-34a-5p, which targets the brain-derived neurotrophic factor mRNA, in the small intestine, peripheral blood, and hippocampus. More importantly, injection of miR-34a-5p agomir inhibited the enhancement effects of metformin on the cognitive defects induced by total abdominal irradiation, as well as the enhanced expression of BNDF and the phosphorylation level of cAMP response element-binding in the hippocampus. Thus, our results provide alternative strategies for the treatment of total abdominal irradiation-induced distant cognitive impairment using metformin and further confirmed that miR-34a-5p is a potential drug target to reduce the cognitive defects caused by total abdominal irradiation.