From the Research
The correct statement concerning the liver in the absorptive state is "Insulin stimulates the uptake of glucose." During the absorptive state, which occurs after a meal, insulin levels rise in response to increased blood glucose. In the liver, insulin promotes glucose uptake by activating glucose transporters, primarily GLUT2, as shown in a study where insulin stimulated liver glucose uptake in humans 1. This allows the liver to take up glucose from the bloodstream for various metabolic processes. In the absorptive state, the liver uses this glucose to replenish glycogen stores through glycogenesis, and excess glucose is converted to fatty acids through lipogenesis. Additionally, insulin activates glycolysis and inhibits gluconeogenesis during this state. The other statements are incorrect because in the absorptive state:
- fructose 2,6-bisphosphate is elevated (not decreased), as it plays a role in regulating glucose metabolism 2, 3
- regulated enzymes are generally dephosphorylated (not phosphorylated), as insulin signaling leads to dephosphorylation and activation of key enzymes
- acetyl CoA oxidation is decreased (as energy needs are met by glucose), as the liver's energy needs are met by glucose and not by fatty acid oxidation
- glucokinase synthesis is induced (not repressed) to facilitate glucose phosphorylation, as glucokinase is a key enzyme in glucose metabolism and its expression is regulated by insulin 3.
Some key points to consider:
- Insulin's role in glucose uptake is crucial for maintaining glucose homeostasis 1
- Fructose 2,6-bisphosphate plays a significant role in regulating glucose metabolism, including glycolysis and gluconeogenesis 2, 3
- The liver's metabolic state is tightly regulated by insulin and other hormones to maintain glucose and lipid homeostasis 4, 3