Ketone bodies are water-soluble molecules or compounds that contain the ketone groups produced from fatty acids by the liver (ketogenesis).[1][2] Ketone bodies are readily transported into tissues outside the liver, where they are converted into acetyl-CoA (acetyl-Coenzyme A)—which then enters the citric acid cycle (Krebs cycle) and is oxidized for energy.[3][4] These liver-derived ketone groups include acetoacetic acid (acetoacetate), beta-hydroxybutyrate, and acetone, a spontaneous breakdown product of acetoacetate (see graphic).
Ketone bodies are produced by the liver during periods of caloric restriction of various scenarios: low food intake (fasting), carbohydrate restrictive diets, starvation, prolonged intense exercise,[5] alcoholism, or during untreated (or inadequately treated) type 1 diabetes mellitus. Ketone bodies are produced in liver cells by the breakdown of fatty acids.[6] They are released into the blood after glycogen stores in the liver have been depleted. (Glycogen stores typically are depleted within the first 24 hours of fasting.)[2]
Ketone bodies are also produced in glial cells under periods of food restriction to sustain memory formation [7]
When two acetyl-CoA molecules lose their -CoAs (or coenzyme A groups), they can form a (covalent) dimer called acetoacetate. β-hydroxybutyrate is a reduced form of acetoacetate, in which the ketone group is converted into an alcohol (or hydroxyl) group (see illustration on the right). Both are 4-carbon molecules that can readily be converted back into acetyl-CoA by most tissues of the body, with the notable exception of the liver. Acetone is the decarboxylated form of acetoacetate which cannot be converted back into acetyl-CoA except via detoxification in the liver where it is converted into lactic acid, which can, in turn, be oxidized into pyruvic acid, and only then into acetyl-CoA.
Ketone bodies have a characteristic smell, which can easily be detected in the breath of persons in ketosis and ketoacidosis. It is often described as fruity or like nail polish remover (which usually contains acetone or ethyl acetate).
Apart from the three endogenous ketone bodies, other ketone bodies like β-ketopentanoate and β-hydroxypentanoate may be created as a result of the metabolism of synthetic triglycerides, such as triheptanoin.
^Cahill, George F.; Veech, Richard L. (2003). "Ketoacids? Good medicine?". Transactions of the American Clinical and Climatological Association. 114: 149–161, discussion 162–163. ISSN 0065-7778. PMC 2194504. PMID 12813917.
^ abStryer, Lubert (1995). Biochemistry (Fourth ed.). New York: W.H. Freeman and Company. pp. 510–515, 581–613, 775–778. ISBN 0-7167-2009-4.
^Silva, B., Mantha, O. L., Schor, J., Pascual, A., Plaçais, P. Y., Pavlowsky, A., & Preat, T. (2022). Glia fuel neurons with locally synthesized ketone bodies to sustain memory under starvation. Nature Metabolism, 4(2), 213–224. https://doi.org/10.1038/s42255-022-00528-6 Archived 2024-03-06 at the Wayback Machine
^Mary K. Campbell; Shawn O. Farrell (2006). Biochemistry (5th ed.). Cengage Learning. p. 579. ISBN 0-534-40521-5.
KetonebodiesKetonebodies are water-soluble molecules or compounds that contain the ketone groups produced from fatty acids by the liver (ketogenesis)...
a ketone /ˈkiːtoʊn/ is an organic compound with the structure R−C(=O)−R', where R and R' can be a variety of carbon-containing substituents. Ketones contain...
Ketosis is a metabolic state characterized by elevated levels of ketonebodies in the blood or urine. Physiological ketosis is a normal response to low...
Ketogenesis is the biochemical process through which organisms produce ketonebodies by breaking down fatty acids and ketogenic amino acids. The process...
Exogenous ketones are a class of ketonebodies that are ingested using nutritional supplements or foods. This class of ketonebodies refers to the three...
shortage of insulin; in response, the body switches to burning fatty acids, which produces acidic ketonebodies. DKA is typically diagnosed when testing...
uncontrolled production of ketonebodies that cause a metabolic acidosis. While ketosis refers to any elevation of blood ketones, ketoacidosis is a specific...
(Dymelor Dimelor) Acetone A byproduct of fat metabolism. One of three ketonebody substances. Produced in high levels during periods of stress, infection...
ketoacidosis produce it in larger amounts. Ketogenic diets that increase ketonebodies (acetone, β-hydroxybutyric acid and acetoacetic acid) in the blood are...
fatty acids and ketonebodies, the latter passing into the brain and replacing glucose as an energy source. An elevated level of ketonebodies in the blood...
been attributed to the elevated ketone levels and increased ketolysis. Kolb H, Kempf K, Martin S (2021). "Ketonebodies: from enemy to friend and guardian...
can be degraded directly into acetyl-CoA, which is the precursor of ketonebodies and myelin, particularly during early childhood, when the developing...
Raspberry ketone is a natural phenolic compound that is the primary aroma compound of red raspberries. Raspberry ketone occurs in a variety of fruits...
blood sugar is not elevated) because of the renal tubular absorption of ketonebodies. A particularly high risk period for ketoacidosis is the perioperative...
week, the brain will use these ketones and any available glucose. Using ketones lowers the need for glucose, and the body slows the breakdown of proteins...
medical condition in which ketonebodies are present in the urine. It is seen in conditions in which the body produces excess ketones as an indication that...
Ketonebodies can be used as fuels, yielding 22 ATP and 2 GTP molecules per acetoacetate molecule when oxidized in the mitochondria. Ketonebodies are...
glycerol reserves start declining, the liver starts producing ketonebodies. Ketonebodies are short-chain derivatives of the free fatty acids mentioned...
mitochondrial matrix enzyme that plays a central role in extrahepatic ketonebody catabolism by catalyzing the reversible transfer of coenzyme A (CoA)...
in contrast to the ketogenic amino acids, which are converted into ketonebodies. The production of glucose from glucogenic amino acids involves these...
nutrients (hypoperfusion), the body's cells burn glucose anaerobically for energy, causing the release of lactic acid, ketonebodies, and other acidic compounds...
slices becomes inhibitory if glucose in perfusate is supplemented with ketonebodies, pyruvate, or lactate, or that the excitatory GABA was an artefact of...
Eicosanoids are made from fatty acids in the body and they are used for cell signaling. Ketonebodies: Ketonebodies are made from fatty acids in the liver...
are organic compounds that contain a carboxylic acid group (−COOH) and a ketone group (>C=O). In several cases, the keto group is hydrated. The alpha-keto...
precursors to triglycerides, phospholipids, second messengers, hormones and ketonebodies. For example, phospholipids form the phospholipid bilayers out of which...
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