The enzyme glutamate dehydrogenase (GDH) catalyzes the interconversion of glutamate and α-ketoglutarate using NAD(P)+/NAD(P)H + H+ as the coenzyme in the redox process. Under physiological conditions in the brain the reaction proceeds as an oxidative conversion of glutamate to α-ketoglutarate. In neurons that do not express the anaplerotic enzyme pyruvate carboxylase the GDH reaction can provide the TCA cycle with the intermediate α-ketoglutarate thus acting as an anaplerotic enzyme ameliorating any drain of TCA cycle intermediates. As astrocytes express the alternative anaplerotic enzyme, pyruvate carboxylase the GDH catalyzed process is of less importance for anaplerosis in these cells. However, in the astrocytes the GDH enzyme appears to be of importance in energy production via the TCA cycle and oxidative phosphorylation as well as a means to enhance TCA cycle capacity facilitating oxidative glucose metabolism. The main text will provide detailed discussions of these different scenarios.