The possibility of replacing threonine by nitrogen-free analogues in a diet of patients with diabetic nephropathy: a biochemical aspect

There is a well established theory that an essential amino acid of threonine is incapable of transamination. According to this theory, in a diet of patients who suffer from nephropathy, including diabetic threonine, is not replaced by its ketoanalogue. However, transamination of threonine, in the human organism in particular, has been discovered by a number of researchers. This suggests that there is a possibility of replacing threonine by its nitrogen-free analogues in nutrition of patients with nephropathy. At the same time nitrogen-free analogues of all amino acids can be subject to oxidative decomposition subsequently not only up to the finishing products, but they can also form glucose or ketone bodies, or both. Depending on this, amino acids are divided into glucogenic only, ketogenic only or both at the same time.

With reference to diabetes this becomes especially important as introduction of glucogenic amino acids and their nitrogen-free analogues has a positive effect, whereas that of ketogenic amino acids and their nitrogen-free analogues is inadmissible. This is caused by the fact that before being transformed into glucose, glucogenic amino acids are transformed into one or another component of Krebs cycle or into the pyruvic acid which is in balance with the components which stimulates oxydation of acetyl coenzyme A and, therefore, ketone bodies.

Ketose with reference to diabetes can be caused by two reasons. While the main source of energy of a healthy person is carbohydrate, in case with diabetes fats perform the function — being oxydized intensively, they form a great number of ketone bodies. The second reason is a decrease in the formation of oxaloacetic acid (Krebs cycle catalyst) from pyruvic acid due to a decrease in the formation of the latter from glucose and an increase in the use of the components of the Krebs cycle for gluconeogenesis.

Ketose causes a sharp shift of pH value to more acidity as a result of accumulation of the acetoacetic acid and the β-hydroxybutyric acid in blood and narcotic actions of the third ketonic body — acetone. The reason for lethal outcome with reference to diabetes is diabetic coma caused by a sharp shift of pH value to more acidity, which disturbs the work of the ferments. Threonine has a strong glucogenic effect in the complete absence of a ketogenic effect on the human body. In this respect, nitrogen-free analogues of threonine do not differ from it.