Implications for biological function of lobe dependence of the molecular structure of liver glycogen

Liver glycogen, a complex branched polymer of glucose, plays a major role in controlling blood sugar levels. Understanding its molecular structure is important for diabetes, especially since it has been found that this structure is more fragile in diabetic than in healthy mouse liver. However, there are differences in metabolic processes between liver lobes, which would be expected to be reflected in differing glycogen molecular structures. This structure was examined for separated lobe regions in rat livers, using size-exclusion chromatography (SEC) and fluorophore-assisted carbohydrate electrophoresis. The results show that the SEC weight distribution of glycogen, and the molecular weight distribution of individual branches (chains), from different lobes are similar. This shows that (a) molecular structural characterization of glycogen from whole-liver biopsy is representative (which is convenient because the commonest animal model for diabetes is the mouse, whose livers are very small), and (b) the fact that molecular structure is conserved (regulated) in different lobes suggests that this structure plays an important role in blood-sugar regulation.