A Warburg-like metabolic program coordinates Wnt, AMPK, and mTOR signaling pathways in epileptogenesis

Abstract

Epilepsy is a complex neurological condition characterized by repeated spontaneous seizures and can be induced by initiating seizures known as status epilepticus (SE). Elaborating the critical molecular mechanisms following SE are central to understanding the establishment of chronic seizures. Here, we identify a transient program of molecular and metabolic signaling in the early epileptogenic period, centered on day five following SE in the pre-clinical kainate or pilocarpine models of temporal lobe epilepsy. Our work now elaborates a new molecular mechanism centered around Wnt signaling and a growing network comprised of metabolic reprogramming and mTOR activation. Biochemical, metabolomic, confocal microscopy and mouse genetics experiments all demonstrate coordinated activation of Wnt signaling, predominantly in neurons, and the ensuing induction of an overall aerobic glycolysis (Warburg-like phenomenon) and an altered TCA cycle in early epileptogenesis. A centerpiece of the mechanism is the regulation of pyruvate dehydrogenase (PDH) through its kinase and Wnt target genes PDK4. Intriguingly, PDH is a central gene in certain genetic epilepsies, underscoring the relevance of our elaborated mechanisms. While sharing some features with cancers, the Warburg-like metabolism in early epileptogenesis is uniquely split between neurons and astrocytes to achieve an overall novel metabolic reprogramming. This split Warburg metabolic reprogramming triggers an inhibition of AMPK and subsequent activation of mTOR, which is a signature event of epileptogenesis. Interrogation of the mechanism with the metabolic inhibitor 2-deoxyglucose surprisingly demonstrated that Wnt signaling and the resulting metabolic reprogramming lies upstream of mTOR activation in epileptogenesis. To augment the pre-clinical pilocarpine and kainate models, aspects of the proposed mechanisms were also investigated and correlated in a genetic model of constitutive Wnt signaling (deletion of the transcriptional repressor and Wnt pathway inhibitor HBP1). The results from the HBP1-/- mice provide a genetic evidence that Wnt signaling may set the threshold of acquired seizure susceptibility with a similar molecular framework. Using biochemistry and genetics, this paper outlines a new molecular framework of early epileptogenesis and advances a potential molecular platform for refining therapeutic strategies in attenuating recurrent seizures.

Harnessing Metabolomics to Advance Epilepsy Research

“…They found enhanced aerobic glycolysis (the Warburg phenomenon) in the epilepsy hippocampus along with increased signaling through the Wnt, the 5' adenosine monophosphate-activated protein kinase (AMPK), and the mammalian target of rapamycin (mTOR) pathways. 25 The above publications support the notions from other studies that perturbations involving energy metabolism, 26 red-ox homeostasis, 27 and signaling molecules (e.g., adenosine) 28 may play important roles in epileptogenesis.…”

Enhanced glycolysis in granulosa cells promotes the activation of primordial follicles through mTOR signaling

“…Pyruvate is the final product of glycolysis, and cells in the pyruvate-free medium will experience a temporary energy shortage inside the cells. This energy shortage activates AMPK to increase catabolism, especially glycolysis [ 20 ], and enhanced glycolysis triggers the inhibition of AMPK and the subsequent activation of mTOR in the mouse brain [ 30 ]. In this study, the standard medium for culturing ovarian tissues contains pyruvate [ 10 – 12 ].…”

Transcriptome profiling implicates a role for Wnt signaling during epileptogenesis in a mouse model of temporal lobe epilepsy

“…Furthermore, different Wnt pathways and signaling mediators may play different roles in the formation of the epileptogenic zone and peri-ictal zone. Indeed, Wnt signaling has been reported as both protective and deleterious in rat generalized epilepsy models; network/region specific changes remain to be fully elucidated (Fasen, 2002; Madsen, 2003; Sun, 2020; Alqurashi, 2021; Jean, 2022).…”

“…There is growing evidence that the Wnt pathway may provide some of the key early signaling events during epileptogenesis (Gupta, 2019; Sun, 2020; Alqurashi, 2021; Jean, 2022). Wnt signaling encompasses a family of 19 secreted Wnt protein ligands, which bind a family of 10 membrane frizzled receptors and co-receptors; these signal to downstream canonical beta-catenin-dependent and non-canonical planar cell polarity and calcium pathways (Oliva, 2013).…”