Abstract

Long-Term Neurobehavioral Status and the Metabolism-Related Gene Expressions in Healthy Rat Hippocampus Following a Ketogenic Diet

Author(s): Ya Ling, Dong-jing Zhao, Hong Ni

While as a well-established therapy for medically intractable epilepsy, clinical evidence of relevant adverse events of ketogenic diet (KD) has also been reported. We asked whether this kind of diet would have deleterious effects on normal brain function by evaluating KDinduced biochemical changes in hippocampus as well as neurobehavioral changes occurring in normal animals. Fifty-four Sprague-Dawley rats on postnatal day 28 (P28) were randomly assigned to three groups: normal rats fed with KD qd (daily for 4 weeks, NS+KD) or qod (every other day for 4 weeks, NS+KOD), and normal rats fed with standard normal laboratory diet (NS+ND). Neurobehavioral changes were observed on P35, P42 and P49. The hippocampal mossy fiber sprouting, the expression levels of zinc transporters (ZnTs) and lipid metabolism related genes were detected by Timm staining, real-time RT-PCR and Western blot analysis on P58, respectively. The results revealed that there were no significant differences in the three reflection tests (surface righting, cliff avoidance, forelimb suspension) among the three groups. KD-treated NS+KOD and NS+KD groups showed a significant delay of negative geotaxis reflex only on P35, but not on P42 and P49. In respect with open field test, daily KD treatment only leaded a reduction in exploratory activity and increased grooming times, but induced no significant changes in the score of vertical activity and delay time. KD qod treated rats (NS+KOD) displayed a slight delay in the place navigation test on P35 compared with that in NS+KD group. There were no significant differences in Timm staining among the three groups. In parallel with these changes, KD treatment (both NS+KD and NS+KOD) induced significantly down-regulated mRNA levels of Apoa1, Pdk4, and upregulated expression of ApoE, ANXN7, cPLA2 in hippocampus when compared with NS+ND group (except ApoE in NS+KOD group). Notably, both the mRNA and protein levels of cPla2 in NS+KOD rats were significantly down-regulated compared with that of NS+KD group, but still markedly higher than that in the NS+ND group. No significant difference was found in concern with ZnTs among the three groups. Our data suggest that early life daily KD treatment in normal rats KD may have no long-term adverse effects on most of the neurobehavioral parameters, but minor neurobehavioral damage may exist. The hippocampal lipid metabolism signaling pathway, especially cPLA2, may be the target of protective effect of KD on long-term brain injury after developmental seizures.