Metabolism in Animals

Carbohydrates from nutrition are metabolized into glucose in the body. This glucose is the most important source of energy for normal metabolic procedures. It circulates freely in the body at disposal for the body’s cells; on the other hand unused glucose is stored in the liver or the muscles as glycogen from where it can be released any time.
 
The hormone insulin which is produced in the beta-cells of the pancreas and released into the blood circulation is the key substance for this process. It enables transport of glucose into the muscle, fat and liver cells and additionally regulates the release of glucose through the liver. This way insulin regulates blood glucose levels. There is no alternate hormone which is able to do this job.

More information:

Diabetes in cats and dogs
Ketosis in dairy cows