Molecular structure of glycogen in diabetic liver
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Liver glycogen (involved in maintaining blood-sugar levels) is a hyperbranched glucose polymer containing β particles (diameter ~20 nm), which can form composite α particles (diameter ~50–300 nm), and includes a small but significant amount of bound protein. Size distributions of glycogen from livers of healthy and diabetic mice were examined using size-exclusion chromatography with two separate eluents: aqueous eluent and dimethylsulfoxide (DMSO) eluent. Morphologies were examined with transmission electron microscopy. Diabetic glycogen (DG) exhibited many α particles in the mild water-based solvent, but in DMSO, which breaks H bonds, these degraded to β particles; α particles however were always present in healthy glycogen (HG). This DG fragility shows the binding of β into α particles is different in HG and DG. The diabetic α particle fragility may be involved with the uncontrolled blood-sugar release symptomatic of diabetes: small β particles degrade more easily to glucose than α particles. This has implications for diabetes management.
KeywordsGlycogen db/db mice Size-exclusion chromatography Type 2 diabetes
The support of the 1000-Talents program of the Chinese Foreign Experts Bureau, and an Australian Research Council Discovery grant, DP130102461, are gratefully acknowledged. We thank Dr. Enpeng Li and Mr. Shiqing Zhou for help with SEC analysis.
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