Some molecular structural features of glycogen in the kidneys of diabetic rats.

Glycogen, a highly-branched glucose polymer, functions as a sugar reservoir in many organs and tissues. Liver glycogen comprises small β particles which can bind to form into large agglomerates (α particles) which readily degrade to β particles in diabetic livers. Muscle glycogen has only β particles, optimal for quick energy release. Healthy kidney contains negligible glycogen, but there is an abnormally high accumulation in diabetic kidneys. We here compare the molecular structure of glycogen in diabetic kidneys with that in liver and muscle, using a diabetic rat model. This involved exploring extraction techniques to minimize glycogen degradation. Using size exclusion chromatography and transmission electron microscopy, it was found that there were only β particles in diabetic kidneys. These are postulated to form during periods of abnormally high blood sugar, the driving force being the need to reduce blood sugar under such circumstances.