Proglycogen and macroglycogen: artifacts of glycogen extraction?

When optimized, 52% to 64% of glycogen in rat muscles is found as acid-soluble glycogen.

• The acid extraction protocol significantly increases the proportion of acid-soluble glycogen compared to a homogenization-free method, which yields about 16%.
• There is no indication that the acid-insoluble glycogen corresponds to proglycogen, as both fractions show similar characteristics in gel chromatography.
• Acid-soluble glycogen is primarily responsible for the changes in total muscle glycogen levels during the transition from fasting to fed states, while acid-insoluble glycogen levels remain stable or increase slightly.
• The findings suggest that previous studies using homogenization-free extraction methods may have underestimated the amount of acid-soluble glycogen.

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