The most prevalent of the KETONE BODIES, which are acids produced by the liver. Acetoacetic acid is a useful fuel; it is readily oxidized by the heart and brain for the production of ATP, the energy currency of cells.
Though small amounts of ketone bodies are normally produced by liver metabolism, an excessive buildup of acetoacetic acid and its derivative, BETA HYDROXYBUTYRIC ACID, in the blood (ketonemia) can occur during excessive fat breakdown, when the liver cannot completely oxidize massive amounts of fatty acids released from fat (ADIPOSE TISSUE). Conditions conducive to excessive acetoacetic acid production include STARVATION (prolonged FASTING), crash DIETING, uncontrolled DIABETES MELLITUS, and chronic ALCOHOLISM.
Ketone body production serves an important role in the physiologic adaptation to starvation. With prolonged starvation, the blood levels of ketone bodies rise, and more of them cross the BLOOD-BRAIN BARRIER to be taken up by nerve tissue, where they are burned for energy. Consequently, the brain requires less blood glucose (blood sugar) for energy at a time when this fuel is at a premium. The sustained build-up of acetoacetic acid in the blood (KETOSIS) can acidify the blood, leading to metabolic ACIDOSIS, and alter the acid-base balance of the body, a potentially dangerous condition.
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