The Molecular Size Distribution of Glycogen and its Relevance to Diabetes

Glycogen is a highly branched polymer of glucose, functioning as a blood-glucose buffer. It comprises relatively small beta-particles, which may be joined as larger aggregate alpha-particles. The size distributions from size-exclusion chromatography (SEC, also known as GPC) of liver glycogen from non-diabetic and diabetic mice show that diabetic mice have impaired alpha-particle formation, shedding new light on diabetes. SEC data also suggest the type of bonding holding beta-particles together in alpha-particles. SEC characterisation of liver glycogen at various time points in a day/night cycle indicates that liver glycogen is initially synthesised as beta-particles, and then joined by an unknown process to form alpha-particles. These alpha-particles are more resistant to degradation, presumably because of their lower surface area-to-volume ratio. These findings have important implications for new drug targets for diabetes management.