Effects of fasting on liver glycogen structure in rats with type 2 diabetes

Liver glycogen, a highly branched glucose polymer, is important for blood sugar homeostasis. It comprises alpha particles which are made of linked beta particles; the molecular structure changes diurnally. In diabetic liver, the alpha particles are fragile, easily breaking apart into beta particles in chaotropic agents such as dimethyl sulfoxide. We here use size-exclusion chromatography to study how fasting changes liver-glycogen structure in vivo for mice in which type-2 diabetes had previously been induced. Diabetic glycogen degraded enzymatically more quickly in the fasted animals than did glycogen without fasting, with fewer a particles, which however were still fragile. The glycogen had fewer long chains and more shorter chains after fasting. This study gives an overview of the in vivo dynamic changes in a-particles under starvation conditions in both normal and diabetic livers.