Glutamate oxaloacetate transaminase enables anaplerotic refilling of TCA cycle intermediates in stroke‐affected brain

Abstract

Ischemic stroke results in excessive release of glutamate, which contributes to neuronal cell death. Here, we test the hypothesis that otherwise neurotoxic glutamate can be productively metabolized by glutamate oxaloacetate transaminase (GOT) to maintain cellular energetics and protect the brain from ischemic stroke injury. The GOT-dependent metabolism of glutamate was studied in primary neural cells and in stroke-affected C57-BL6 mice using magnetic resonance spectroscopy and GC-MS. Extracellular Glu sustained cell viability under hypoglycemic conditions and increased GOT-mediated metabolism Correction of stroke-induced hypoxia using supplemental oxygen lowered Glu levels as measured by H magnetic resonance spectroscopy. GOT knockdown abrogated this effect and caused ATP loss in the stroke-affected brain. GOT overexpression increased anaplerotic refilling of tricarboxylic acid cycle intermediates in mouse brain during ischemic stroke. Furthermore, GOT overexpression not only reduced ischemic stroke lesion volume but also attenuated neurodegeneration and improved poststroke sensorimotor function. Taken together, our results support a new paradigm that GOT enables metabolism of otherwise neurotoxic extracellular Glu through a truncated tricarboxylic acid cycle under hypoglycemic conditions.-Rink, C., Gnyawali, S., Stewart, R., Teplitsky, S., Harris, H., Roy, S., Sen, C. K., Khanna, S. Glutamate oxaloacetate transaminase enables anaplerotic refilling of TCA cycle intermediates in stroke-affected brain.

Glutamate metabolism in cerebral mitochondria after ischemia and post‐ischemic recovery during aging: relationships with brain energy metabolism

“…Also Rink et al . () recently pointed out that, in ischemic conditions, glutamate‐oxaloacetate transaminase may be primarily involved in glutamate conversion into metabolic fuel, that is, α‐ketoglutarate.…”

“…; Rink et al . ). In this perspective, glutamate should be studied from a different point of view, because it is not only a neurotransmitter, but primarily a key metabolite for brain bioenergetics (Cooper ; Villa et al .…”

Interaction of Excitatory Amino Acid Transporters 1 – 3 (EAAT1, EAAT2, EAAT3) with N-Carbamoylglutamate and N-Acetylglutamate

“…Oxaloacetate was recently introduced as a neuroprotective drug [19-22] due to ability to decrease blood glutamate levels by the activation of the blood-resident enzyme glutamate-oxaloacetate transaminase (GOT). This enzyme catalyzes, by transfer of an amino group, the transformation of glutamate into α-ketoglutarate and of oxaloacetate into L-aspartate.…”

Phytoestrogen isoflavone intervention to engage the neuroprotective effect of glutamate oxaloacetate transaminase against stroke

“…To that end, research efforts that have focused on the removal of pathologically elevated glutamate in the injured brain have been increasingly recognized for the therapeutic potential of glutamate removal to mitigate neurotoxicity (1)(2)(3)(4). Our laboratory has recently demonstrated the therapeutic potential of inducible glutamate oxaloacetate transaminase (GOT), a glutamate metabolizing enzyme that can repurpose otherwise neurotoxic glutamate in the stroke-affected brain as energy substrate for glucose-starved neurons (5)(6)(7). Specifically, GOT enables glutamate metabolism and the anaplerotic refilling of tricarboxylic acid (TCA; or the Krebs) cycle intermediates via at r u n c a t e dT C A cycle in the ischemic stroke-affected and, subsequently, hypoglycemic brain (6).…”

“…Our laboratory has recently demonstrated the therapeutic potential of inducible glutamate oxaloacetate transaminase (GOT), a glutamate metabolizing enzyme that can repurpose otherwise neurotoxic glutamate in the stroke-affected brain as energy substrate for glucose-starved neurons (5)(6)(7). Specifically, GOT enables glutamate metabolism and the anaplerotic refilling of tricarboxylic acid (TCA; or the Krebs) cycle intermediates via at r u n c a t e dT C A cycle in the ischemic stroke-affected and, subsequently, hypoglycemic brain (6). Our observation identified that the correction of focal hypoxia during ischemic stroke induces GOT expression and rescues brain tissue from injury.…”