Glycogen is a branched polymer of glucose that acts as an
intracellular glucose store. Most tissues are capable of storing
glycogen. However, liver and skeletal muscle contain the most
abundant depots in the body. Glycogen metabolism in the liver is
important for the regulation of blood glucose homeostasis, whereas
in the muscle, glycogen utilisation is the main fuel to provide glucose
and ATP needed for muscle contraction in prolonged high-intensity
exercise. Other tissues capable of metabolising glycogen include the
brain and the adipose tissue. In the brain, glycogen is found both in
astrocytes and neurons and its degradation in the former is thought
to spare blood glucose for neurons during high brain activation [1],
whereas in the latter, it promotes neuronal tolerance to hypoxic
stress [2]. In the adipose tissue, glycogen is tightly coupled with lipid
metabolism and potentially functions as a metabolic sensor to