A healthy adult consumes only water for several days. Compared with the fed state, which combination of metabolic changes is most likely?
Select one answer.
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Answer: A (Increased adipose triacylglycerol hydrolysis; increased hepatic ketone body synthesis; decreased skeletal muscle glucose uptake)
During prolonged fasting, decreased insulin signaling and increased glucagon signaling promote the hydrolysis of triacylglycerols in adipose tissue. The released fatty acids undergo hepatic beta-oxidation, producing acetyl-CoA. Because oxaloacetate is increasingly used for gluconeogenesis, much of this acetyl-CoA is converted to ketone bodies. Decreased insulin signaling also reduces GLUT4 translocation in skeletal muscle, thereby decreasing muscle glucose uptake. Thus, choice A is correct. Choice B incorrectly predicts increased muscle glucose uptake, choice C incorrectly predicts decreased ketone body synthesis, and choice D incorrectly predicts decreased mobilization of stored fatty acids.