During early fasting, glycogen is used as a source of glucose for the blood. After liver glycogen is depleted, which of the following is most likely to contribute to the maintenance of endogenous serum glucose levels?
A) amino acids of muscle proteins are used to synthesize glucose in the brain
B) fatty acids of adipose tissue are converted into glucose in the liver
C) intestinal glutamine is used as a gluconeogenic substrate
D) liver fatty acids are degraded as precursors for blood glucose
E) skeletal muscle glycogen is broken down and the glucose delivered to the blood

Question

Quizplus · Accepted Answer

Intestinal glutamine is used as a gluconeogenic substrate. During periods of fasting and starvation, when liver glycogen levels are depleted, the major source of carbon atom for hepatic gluconeogenesis is from the amino acids released due to protein degradation within skeletal muscle. However, the kidneys and the small intestine do contribute to endogenous glucose production via the use of glutamine as a carbon source for gluconeogenesis in these 2 tissues.

During Early Fasting, Glycogen Is Used as a Source of Glucose