Principles of Biochemistry, Volume 3 - A. Lehninger 1985

Selected Aspects of Human Biochemistry
Digestion, Nutrient Transport, and Metabolic Interrelationships
In diabetes, urea excretion increases

Severe diabetes is also characterized by an increased excretion of urea, the principal end product of Nitrogen METABOLISM formed during the oxidative degradation of Amino Acids (Sections 19.14–19.16). The amount of urea excreted by a patient per day serves as a measure of the total amount of amino acids broken down via oxidative pathways, which in turn reflects the daily balance between Dietary Protein Intake and the degradation of tissue Proteins. The Blood urea concentration in diabetes can reach 25 mM, i.e., approximately 5 times the normal level (about 5 mM).

The excessive oxidative degradation of amino acids in diabetes is caused by a sharp increase in The rate of Gluconeogenesis from amino acids. Insulin deficiency promotes the release of glucose from the Liver into the bloodstream. As a result, hepatic Glycogen stores become depleted; under these conditions, all available amino acids whose carbon skeletons can be utilized for gluconeogenesis undergo degradation and are channeled into glucose synthesis, which is then released into the blood. It follows that measuring urea levels in the blood and urine provides valuable insight into the metabolic status of diabetic patients.