Effects of exercise on mature or precursor brain-derived neurotrophic factor pathways in ovariectomized rats

Abstract

Ovariectomy (OVX) is a method used to block estrogen in female rats that induces hippocampal dysfunction and affects brain-derived neurotrophic factor (BDNF) pathways. The majority of previous studies investigating OVX focused on BDNF expression in the hippocampus and cognitive function. The present study focused on the pathways of each BDNF type, precursor (proBDNF) and mature (mBDNF), and the effects of regular exercise in the hippocampus of ovariectomized rats. Female Sprague-Dawely rats were used and OVX surgery was performed. After 1 week of recovery from surgery, two groups of rats that received OVX surgery were subjected to regular treadmill exercise for 8 weeks. The results of protein levels by western blotting indicated that the expression of proBDNF, p75 neurotrophin receptor (p75NTR) and c-Jun N-terminal protein kinase (JNK) was increased, and mBDNF, tropomyosin-related kinase B (TrkB) and nuclear factor-kB expression was significantly reduced in the OVX control group compared with the sham control group SC (P<0.05). Thus, the survival pathway by mBDNF was impaired and the pro-apoptotic response was activated by increased JNK expression due to proBDNF-p75NTR binding in the hippocampus of ovariectomized rats. By contrast, exercise reduced activation of the pro-apoptotic response and increased mBDNF-TrkB expression in the hippocampus of ovariectomized rats. Thus, regular exercise may increase the activation of survival pathways via mBDNF and reducing the activation of the pro-apoptotic pathway of proBDNF in the hippocampus of ovariectomized rats.