Glycogen function in adult central and peripheral nerves

Area of Science:

• Neuroscience
• Cellular Metabolism
• Neurobiology

Background:

• Glycogen is a polysaccharide that serves as a form of energy storage in animals and fungi.
• The role of glycogen in the function of axonal pathways in the central nervous system (CNS) and peripheral nervous system (PNS) is not fully understood.
• Understanding glycogen's role is critical for comprehending neuronal energy metabolism and function under various physiological conditions.

Purpose of the Study:

• To investigate the functional significance of glycogen in axonal pathways of the CNS and PNS.
• To determine the impact of glycogen depletion on nerve conduction under conditions of aglycemia.
• To identify the cellular localization of glycogen within the CNS and PNS and its metabolic contribution to axonal energy supply.

Main Methods:

• Electrophysiological recordings to assess compound action potential (CAP) in mouse optic nerve (MON) and mouse sciatic nerve (MSN).
• Biochemical glycogen assays to quantify glycogen levels in neural tissues.
• Pharmacological inhibition of glycogen phosphorylase using diaminobenzidine to assess its impact on lactate release.

Main Results:

• Glycogen is present in astrocytes (MON) and myelinating Schwann cells (MSN), but absent in Schwann cells of unmyelinated C fibers.
• Aglycemia led to CAP loss, correlating with glycogen exhaustion, except in MSN C fibers.
• Lactate, derived from glycogen metabolism, supports A fiber conduction in glucose absence, indicating a conserved energy pathway in CNS and PNS.

Conclusions:

• Glycogen acts as a vital backup energy substrate for both CNS and PNS axons.
• Metabolized glycogen provides lactate, supporting axonal energy demands during glucose deprivation and high activity.
• This study highlights a common metabolic pathway for axonal energy supply across the CNS and PNS.