Regulation of brain PPARgamma2 contributes to ketogenic diet anti-seizure efficacy

Abstract

The ketogenic diet (KD) is an effective therapy primarily used in pediatric patients whom are refractory to current anti-seizure medications. The mechanism of the KD is not completely understood, but is thought to involve anti-inflammatory and anti-oxidant processes. The nutritionally-regulated transcription factor peroxisome proliferator activated receptor gamma, PPARγ, regulates genes involved in anti-inflammatory and anti-oxidant pathways. Moreover, endogenous ligands of PPARγ include fatty acids suggesting a potential role in the effects of the KD. Here, we tested the hypothesis that PPARγ contributes to the anti-seizure efficacy of the KD. We found that the KD increased nuclear protein content of the PPARγ2 splice variant by 2–4 fold (p < 0.05) in brain homogenates from wild-type (WT) and epileptic Kv1.1 knockout (KO) mice, while not affecting PPARγ1. The KD reduced the frequency of seizures in Kv1.1KO mice by ~70% (p < 0.01). GW9662, a PPARγ antagonist, prevented KD-mediated changes in PPARγ2 expression and prevented the anti-seizure efficacy of the KD in Kv1.1KO mice. Further supporting the association of PPARγ2 in mediating KD actions, the KD significantly prolonged the latency to flurothyl-induced seizure in WT mice by ~20–35% (p < 0.01), but was ineffective in PPARγ2KO mice and neuron-specific PPARγKO mice. Finally, administering the PPARγ agonist pioglitazone increased PPARγ2 expression by 2-fold (p < 0.01) and reduced seizures in Kv1.1KO mice by ~80% (p < 0.01). Our findings implicate brain PPARγ2 among the mechanisms by which the KD reduces seizures and strongly support the development of PPARγ2 as a therapeutic target for severe, refractory epilepsy.

New insights into the mechanisms of the ketogenic diet

“…PPARγ is activated by fatty acids, such as decanoic acid, and might therefore mediate anti-inflammatory and anti-oxidant properties of the KD. A PPARγ antagonist abrogated KD-induced seizure protection in Kv1.1 knockout mice, a spontaneously epileptic mouse strain responsive to KD therapy [32], whereas an PPARγ agonist conferred seizure protection; in line with these findings KD therapy was ineffective in preventing seizures in PPARγ knockout mice [33 • ]. Since seizure suppression was associated with a PPARγ induced increase in PPARγ 2 expression, the authors of this study concluded that PPARγ 2 contributes to the anti-seizure effects of KD therapy.…”

Synergistic protection against acute flurothyl‐induced seizures by adjuvant treatment of the ketogenic diet with the type 2 diabetes drug pioglitazone

“…Our previous study indicated that the KD and pioglitazone share a mechanism of action via the transcription factor PPARγ 4 . Therefore, we hypothesized that co-administration of a KD and pioglitazone would have additive effects.…”

“…The KD has been demonstrated to have consistent effects across laboratories on seizure threshold in the flurothyl model of acutely provoked generalized clonic and tonic-clonic seizures 4,13,14 ; thus, this model was chosen to test our hypothesis. Before performing co-administration studies, it was necessary to determine both effective and ineffective KD ratios against flurothyl-induced clonic and GTC seizures.…”

“…Regulation of the nuclear transcription factor PPARγ contributes to the antiseizure efficacy of the KD 4 . Here, we demonstrate that the KD and the PPARγ agonist pioglitazone delay the onset of flurothyl-induced GTC seizures.…”

“…Recently, we identified the peroxisome proliferator activated receptor gamma (PPARγ) as a significant contributor to the anti-seizure mechanism of the KD 4 . PPARγ is a nuclear transcription factor most noted as a master regulator of adipogenesis, lipid metabolism and insulin sensitivity; but, PPARγ also increases transcription of anti-inflammatory, anti-oxidant and mitochondrial genes 5 .…”