Activity-dependent neuroprotective protein (ADNP) derived peptide NAP prevents musculoskeletal abnormalities in ovariectomized mice

Estrogen is an essential hormone that critically impacts bodily and brain functions, supporting learning, memory, and motor activities. A decrease in estrogen levels is associated with cognitive decline and motor dysfunction, such as muscle weakness. While conventional hormone replacement treatments (HRT) exist, those have limitations and potentially severe side effects. NAP (davunetide) is the smallest neuroprotective peptide site of activity-dependent neuroprotective protein (ADNP), a master regulator of cognition, essential for brain formation. It is known that NAP restores ADNP activity in cases of deficiency and it has already shown potential in preventing cognitive impairment, protecting against tauopathy, and improving motor function in various animal models and in clinical trials. Based on the dynamic regulation of ADNP by the estrous cycle and its involvement in steroidogenic pathways, we hypothesize that NAP may restore ADNP activity and thus serve as an alternative to conventional hormonal treatments. To test this hypothesis, 3-month-old female ICR mice underwent bilateral ovariectomy (OVX) or sham surgery and received daily intranasal administration of NAP, estrogen, or vehicle. Results showed a significant reduction in weight-normalized forelimb grip strength in the OVX model. Interestingly, grip strength was the only test that yielded significant OVX effects, and no significant differences were observed in the novel object recognition (NOR) test or computed tomography (CT) scans. Daily intranasal administration of either NAP or estrogen resulted in an apparent increase in the weight-normalized grip strength compared to the sham-treated OVX group. Furthermore, both the NAP- and the estrogen-treated OVX mouse groups did not statistically differ from the vehicle-treated sham control. These findings suggest that NAP may effectively prevent the loss of physical force production typically seen following ovarian hormone depletion, presenting a viable, non-hormonal candidate strategy for managing musculoskeletal symptoms. We hypothesize that the lack of significance OVX effects in other parameters was due to soy-derived phytoestrogens in the current Tel Aviv University’s standard diet. Thus, the standard diet may have exerted a systemic estrogenic effect that masked the expected physiological phenotypes typically observed in OVX models. Future replication using phytoestrogen-deficient food is required to isolate the specific neuroprotective and musculoskeletal effects of NAP from dietary influence and clarify broader therapeutic benefits.