page_title: Exogenous ketone
section_title: Structure
hierarchical_section_title: Exogenous ketone / Structure
context_page_description: Exogenous ketones are a class of ketone bodies that are ingested using nutritional supplements. This class of ketone bodies refers to the three water-soluble ketones. These ketone bodies are produced by interactions between macronutrient availability such as low glucose and high free fatty acids or hormone signaling such as low insulin and high glucagon/cortisol. Under physiological conditions, ketone concentrations can increase due to starvation, ketogenic diets, or prolonged exercise, leading to ketosis. However, with the introduction of exogenous ketone supplements, it is possible to provide a user with an instant supply of ketones even if the body is not within a state of ketosis before ingestion.
  Most supplements rely on β-hydroxybutyrate as the source of exogenous ketone bodies. It is the most common exogenous ketone body because of its efficient energy conversion and ease of synthesis. In the body, β-HB can be converted to acetoacetic acid. It is this acetoacetic acid that will enter the energy pathway using beta-ketothialase, becoming two Acetyl-CoA molecules. The Acetyl CoA is then able to enter the Krebs cycle in order to generate ATP.
context_section_description: Acetoacetate is produced in the mitochondria of liver cells by the addition of an acetyl group from acetyl CoA. This creates 3-hydroxy-3-methylgluteryl CoA which loses an acetyl group, becoming acetoacetate.
  β-Hydroxybutyrate is also synthesized within liver cells; this is accomplished through the metabolism of fatty acids. Through a series of reactions, acetoacetate is first produced; and it is this acetoacetate that is reduced into β-hydroxybutyrate, catalyzed by the β-hydroxybutyrate dehydrogenase enzyme.  Although, β-hydroxybutyrate is technically not a ketone due to the structure of the molecule (OH- attached to carbonyl group makes this an acid), β-HB acts like a ketone, providing the body with energy in the absence of glucose. In fact, β-Hydroxybutyrate is the most abundant ketone in the blood during ketosis.
  Acetone is an organic compound with the formula (CH3)2CO and is one of the simplest and smallest ketones. It is synthesized from the breakdown of acetoacetate in ketotic individuals within the liver.
caption: Acetone