Deficient energy metabolism and network hyperactivity are the early symptoms of Alzheimer's disease (AD). In this study, we show that administration of exogenous oxidative energy substrates (OES) corrects neuronal energy supply deficiency that reduces the amyloid-beta-induced abnormal neuronal activity in vitro and the epileptic phenotype in AD model in vivo. In vitro, acute application of protofibrillar amyloid-b 1-42 (Ab 1-42 ) induced aberrant network activity in wild-type hippocampal slices that was underlain by depolarization of both the neuronal resting membrane potential and GABA-mediated current reversal potential. Ab 1-42 also impaired synaptic function and long-term potentiation. These changes were paralleled by clear indications of impaired energy metabolism, as indicated by abnormal NAD(P)H signaling induced by network activity. However, when glucose was supplemented with OES pyruvate and 3-beta-hydroxybutyrate, Ab 1-42 failed to induce detrimental changes in any of the above parameters.We administered the same OES as chronic supplementation to a standard diet to APPswe/PS1dE9 transgenic mice displaying AD-related epilepsy phenotype. In the ex-vivo slices, we found neuronal subpopulations with significantly depolarized resting and GABA-mediated current reversal potentials, mirroring abnormalities we observed under acute Ab 1-42 application. Ex-vivo cortex of transgenic mice fed with standard diet displayed signs of impaired energy metabolism, such as abnormal NAD(P)H signaling and strongly reduced tolerance to hypoglycemia. Transgenic mice also possessed brain glycogen levels twofold lower than those of wild-type mice. However, none of the above neuronal and metabolic dysfunctions were observed in transgenic mice fed with the OES-enriched diet. In vivo, dietary OES supplementation abated neuronal hyperexcitability, as the frequency of both epileptiform discharges and spikes was strongly decreased in the APPswe/PS1dE9 mice placed on the diet. Altogether, our results suggest that early AD-related neuronal malfunctions underlying hyperexcitability and energy metabolism deficiency can be prevented by dietary supplementation with native energy substrates.

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Epileptic activity without visible convulsions is common in Alzheimer's disease (AD) and may contribute adversely to the disease progress and symptoms. Transgenic mice with amyloid plaque pathology also display epileptic seizures, but those are too infrequent to assess the effect of anti-epileptic treatments. Besides spontaneous seizures, these mice also display frequent epileptic spiking in epidural EEG recordings, and these have provided a means to test potential drug treatment to AD-related epilepsy. However, the origin of EEG spikes in transgenic AD model mice has remained elusive, which makes it difficult to relate electrophysiology with underlying pathology at the cellular and molecular level. Using multiple cortical and subcortical electrodes in freely moving APP/PS1 transgenic mice and their wild-type littermates, we identified several types of epileptic spikes among over 15 800 spikes visible with cortical screw electrodes based on their source localization. Cortical spikes associated with muscle twitches, cortico-hippocampal spikes, and spindle and fast-spindle associated spikes were present equally often in both APP/PS1 and wild-type mice, whereas pure cortical spikes were slightly more common in APP/PS1 mice. In contrast, spike-wave discharges, cortico-hippocampal spikes with after hyperpolarization and giant spikes were seen almost exclusively in APP/PS1 mice but only in a subset of them. Interestingly, different subtypes of spikes responded differently to anti-epileptic drugs ethosuximide and levetiracetam. From the translational point most relevant may be the giant spikes generated in the hippocampus that reached an amplitude up to ± 5 mV in the hippocampal channel. As in AD patients, they occurred exclusively during sleep. Further, we could demonstrate that a high number of giant spikes in APP/PS1 mice predicts seizures. These data show that by only adding a pair of hippocampal deep electrodes and EMG to routine cortical epidural screw electrodes and by taking into account underlying cortical oscillations, one can drastically refine the analysis of cortical spike data. This new approach provides a powerful tool to preclinical testing of potential new treatment options for AD related epilepsy.

Several Alzheimer model mice carrying transgenic amyloid precursor protein (APP) with the Swedish mutation have been reported to exhibit spontaneous seizures and/or increased epileptiform EEG activity. The primary cause for the epilepsy phenotype is still under debate. In contrast to mice with APPswe mutation that develop extracellular amyloid plaques, mice with APP Arctic mutation (E693G) have no bias toward β-secretase cleavage and display intracellular amyloid deposits but not plaques. We conducted a systematic long-term video-EEG recording in three two-week sessions on 21 APParc and 11 wild-type control mice between 3.5 and 8 months of age. Spontaneous seizures were not detected more often in APParc mice than in their wild-type control mice. Long (1 - 5 s) epileptiform discharges were occasionally detected in both APParc and wild-type mice, but short (0.5 - <1 s) epileptiform discharges were more common in APParc mice than in wild-types. However, they were far less frequent than in 6 APPswe/PS1dE9 mice recorded in parallel. In pentylenetetrazole test for seizure susceptibility, APParc mice displayed a shorter latency to sharp-wave discharges than wildtype mice but no increase in seizure duration. These data speak for a relatively mild epilepsy phenotype in APParc mice compared to APPswe mice despite even higher extent of APP overexpression. Thus extracellular amyloid plaques or increased β-secretase cleavage products appear important for the epilepsy phenotype in APPswe mice.

Patients with Alzheimer's disease are at increased risk for unprovoked seizures and epilepsy compared with age-matched controls. Experimental evidence suggests that neuronal hyperexcitability and epilepsy can be triggered by amyloid-β (Aβ), the main component of amyloid plaques. Previous studies demonstrated that the administration of an anticonvulsant and histone deacetylase inhibitor, valproic acid, leads to a long-lasting reduction in Aβ levels. Here we used an APdE9 mouse model of Alzheimer's disease with overproduction of Aβ to assess whether treatment with valproic acid initiated immediately after epilepsy onset modifies the occurrence of epileptiform activity. We also analyzed whether the effect is long-lasting and associated with antiamyloidogenesis and histone-modifications. Male APdE9 mice (15 week old) received daily intraperitoneal injections of 30mg/kg valproic acid for 1 week. After a 3-week wash-out, the same animals received injections of a higher dose of valproic acid (300mg/kg) daily for 1 week. Long-term video-electroencephalography monitoring was performed prior to, during, and after the treatments. Aβ and total histone H3 and H4 acetylation levels were measured at 1 month after the final valproic acid treatment. While 30mg/kg valproic acid reduced spontaneous seizures in APdE9 mice (p<0.05, chi-square), epileptiform discharges were not reduced. Administration of 300mg/kg valproic acid, however, reduced epileptiform discharges in APdE9 mice for at least 1 week after treatment discontinuation (p<0.05, Wilcoxon test), but there was no consistent long-term effects on epileptiform activity after treatment withdrawal. Further, we found no long-lasting effect on Aβ levels (p>0.05, Mann-Whitney test), only a meager increase in global acetylation of histone H3 (p<0.05), and no effects on H4 acetylation (p>0.05). In conclusion, valproic acid treatment of APdE9 mice at the stage when amyloid plaques are beginning to develop and epileptiform activity is detected reduced the amount of epileptiform activity, but the effect disappeared after treatment discontinuation.