Question

A second hallmark of glycogen-synthase deficiency is high levels of ketone bodies. Which of the following explains this symptom?

A) When tissues are starved of glucose, the liver responds by making ketone bodies

B) Beta oxidation is intact in these patients. Therefore, the liver of these patients can still readily create the substrate of ketone-body synthesis, acetyl-CoA, despite low levels of pyruvate.

C) Since glucogenic intermediates, like pyruvate, are needed for anaplerosis, Krebs intermediates are low. This leads to a buildup of acetyl-CoA in the matrix, which facilitates ketone-body synthesis.

D) All of the above

the answer is not B.

Answer 1

C. Since glucogenic intermediates, like pyruvate, are needed for anaplerosis, Krebs intermediates are low. This leads to a build-up of acetyl-CoA in the matrix, which facilitates ketone-body synthesis.

Glycogen synthase is a very important enzyme, required in the synthesis of glycogen. It's a glycosyltransferase, which converts UDP-Glucose to UDP and Glycogen. If this enzyme is deficient, more and more glucose will be available, thereby leading to increase in glycolysis. As a result of which, more pyruvate molecules are released and they participate into TCA cycle, leading to production of more and more acetyl-CoA. But since TCA cycle intermediates are low, acetyl-CoA accumulates and hence ketosis increases.