This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Nutrition & Digestion, Subject name: Biochemistry
[{'content': 'In the fasting state, which one of the following is utilized by the liver for gluconeogenesis? \nSelect and explain. \nA. Glycerol, B. Even-chain fatty acids, C. Liver glycogen, D. Ketone bodies', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Carbons from lactate, propionate (from odd-chain fatty acids and certain amino acids), glycerol (from fat stores), and amino acids (from muscle) can be used for gluconeogenesis. Fatty acids and ketone bodies are directly utilized for energy and are not used for gluconeogenesis. The end product of even-chain fatty acid oxidation is acetylCoA, which cannot be used as a precursor for net glucose production. Liver glycogen produces glucose through glycogenolysis.', 'role': 'assistant'}]