• In the liver, fatty acids and amino acids are metabolized to acetoacetate and β-hydroxybutyrate (to be used in muscle and brain).
• In prolonged starvation and diabetic ketoacidosis, oxaloacetate is depleted for gluconeogenesis. In alcoholism, excess NADH shunts oxaloacetate to malate. Both processes cause a buildup of acetyl-CoA, which shunts glucose, amino acids, and FFAs toward the production of ketone bodies.
• Ketone bodies: acetone, acetoacetate, β-hydroxybutyrate.
• Breath smells like acetone (fruity odor).
• Urine test for ketones can detect acetoacetate, but not β-hydroxybutyrate.
• RBCs cannot utilize ketones; they strictly use glucose.
• HMG-CoA lyase for ketone production.
• HMG-CoA reductase for cholesterol synthesis.