Characterization of 1,4‐dideoxy‐1,4‐imino‐d‐arabinitol (DAB) as an inhibitor of brain glycogen shunt activity

Abstract

The pharmacological properties of 1,4‐dideoxy‐1,4‐imino‐d‐arabinitol (DAB), a potent inhibitor of glycogen phosphorylase and synthase activity in liver preparations, were characterized in different brain tissue preparations as a prerequisite for using it as a tool to investigate brain glycogen metabolism. Its inhibitory effect on glycogen phosphorylase was studied in homogenates of brain tissue and astrocytes and IC50‐values close to 400 nM were found. However, the concentration of DAB needed for inhibition of glycogen shunt activity, i.e. glucose metabolism via glycogen, in intact astrocytes was almost three orders of magnitude higher. Additionally, such complete inhibition required a pre‐incubation period, a finding possibly reflecting a limited permeability of the astrocytic membrane. DAB did not affect the accumulation of 2‐deoxyglucose‐6‐phosphate indicating that the transport of DAB is not mediated by the glucose transporter. DAB had no effect on enzymes involving glucose‐6‐phosphate, i.e. glucose‐6‐phosphate dehydrogenase, phosphoglucoisomerase and hexokinase. Furthermore, DAB was evaluated in a functional preparation of the isolated mouse optic nerve, in which its presence severely reduced the ability to sustain evoked compound action potentials in the absence of glucose, a condition in which glycogen serves as an important energy substrate. Based on the experimental findings, DAB can be used to evaluate glycogen shunt activity and its functional importance in intact brain tissue and cells at a concentration of 300–1000 μM and a pre‐incubation period of 1 h.

Functional Astrocyte-Neuron Lactate Shuttle in a Human Stem Cell-Derived Neuronal Network

“…We also demonstrate that lactate production and glycogen breakdown occur in astrocytes after neuronal activation and hypoglycemia and is blocked using 1,4-dideoxy-1,4-imino-d-arabinitol. [34][35][36][37] These results, together with glycogen staining, suggest that NT2.A cells possess the machinery required for glycogen synthesis and glycogen breakdown. The decrease in glycogen levels and subsequent increase in lactate suggest that NT2.A respond to glutamate and potassium, not only by increasing glucose uptake, but also by degrading glycogen as demonstrated in vivo and in primary cultures.…”

Introduction: Special Issue in Honor of Bruce Ransom

“…This brought him in contact with Arne Schousboe and Arne's colleague Helle Waagepetersen to discuss brain glycogen metabolism and the three had a successful collaboration [1,30] Bruce has contributed many excellent papers to the scientific community. He has an h-factor of 69 which is mainly based on basic scientific papers, but he also published some papers on clinical topics.…”

Brain Energy Metabolism in Health and Disease

“…Glycogenolysis produces glucose-6-phosphate. It has been proposed that glucose-6-phosphate is used to produce metabolic substrates such as lactate, which can be exported from astrocytes to neuronal cells (Benarroch, 2010;Walls et al, 2008). It has also been proposed that glucose-6-phosphate from glycogen in astrocytes inhibits glycolysis (by hexokinase inhibition) and thus, glucose consumption is favored by neurons (DiNuzzo et al, 2011).…”

“…During synaptic activity, breakdown of astrocytic glycogen is stimulated by neurotransmitters such as glutamate and norepinephrine (Walls et al, 2008). Adrenergic agents cause protein kinase A (PKA) activation in astrocytes through metabotropic receptor binding.…”

“…Serotonin and other neurotransmitters induce an increase in intracellular concentrations of Ca 2+ (via IP 3 production) and thus, activate glycogenolysis (Chen & Hertz, 1999). Activation of glycogen synthesis and degradation is termed the glycogen shunt (Walls et al, 2008). Glucose-6-phosphate from glycogen can be oxidized through glycolysis to produce lactate which is exported to neurons (Figure 7).…”