Creatine supplementation and neural plasticity in CNS development

Creatine (Cr) is a guanidine compound primarily known for the ergogenic role. Recently, because of its pleiotropic properties, including antioxidant (Sestili et al. 2006) and neuroprotective (Beal 2011; Sartini et al. 2012) effects, interest is growing surrounding a possible use of creatine supplementation during pregnancy as a tool to prevent CNS damage caused by pre-, peri-, and post-natal hypoxic-ischemic events. Little is known on the effects and safety of Cr supplementation on neuron differentiation, and our in vitro study has shown a positive effect of Cr in protecting developing neuroblasts from oxidative stress (Sartini et al. 2012), a status closely associated to peri-natal hypoxia-ischemia. However, Cr supplementation induced also a significant and dose-dependent anticipation of Na+ and K+ current expression and a higher excitability (Sartini et al. 2012). Moreover, in our in vivo study, maternal Cr supplementation at low dosage (1% of Cr in drinking water) was demonstrated to affect the morpho-functional development of hippocampal neurons in neonatal rats at postnatal day 14-21 (P14-21). Cr supplementation was decisive for an enhanced dendritic tree development, larger evoked-synaptic responses and increased Long Term Potentiation (LTP) maintenance (Sartini et al. 2016), but the higher excitability was also confirmed, leaving the safety of Cr supplementation during CNS development as an open question. Because of these findings, in this study, the epileptic threshold was analyzed at P14-21 to investigate the effect of the hyperexcitability on the probability of epileptiform activities induction. Furthermore, the long-term effects of maternal Cr supplementation on adult brains (P60-70) were investigated using electrophysiological recordings, morphological analysis, and calcium imaging. Finally, considering that LTP is one of the crucial cellular mechanisms involved in learning processes, the ability of spatial learning using the Morris Water Maze has been consequently studied. Results showed that maternal creatine supplementation positively affects the morpho-functional development of CA1 pyramidal neurons of rat offspring. Some morpho-functional changes found in the Cr-treated group at P60-70, such as a similar dendritic length and complexity in Cr-treated and untreated groups, suggest the results previously obtained as an anticipation of neural development; other changes could be identified also in adulthood. In fact, also 60 days old Cr-treated group showed a higher LTP maintenance in comparison to controls, likely related to a lower calcium transient during neural activity. This is an interesting finding considering that LTP is one of the main mechanisms underlying learning processes, thus, maternal Cr supplementation might improve behavioral and cognitive tasks in rat progeny through these permanent modifications, although we found no differences in the Morris Water Maze between the two groups. Furthermore, maternal Cr supplementation appears to be safe, at least in our experimental setting. These findings might be encouraging towards the conducting of future human studies, and to a possible use of Cr during pregnancy to prevent and treat CNS damage following hypoxia/ischemia caused by premature birth or placental insufficiency (Dickinson et al. 2014; Ellery et al. 2016)