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Ketone Bodies Synthesis

Ketone

Ketone

ke·tone (kē′tōn′) n. 1. Any of a class of organic compounds, such as acetone, characterized by having a carbonyl group in which the carbon atom is bonded to two other hydrocarbon groups and having the general formula R(CO)R′, where R may be the same as R′. [German Keton, shortening and alteration of Aceton, acetone : Latin acētum, vinegar; see acetum + German -on, n. suff. (alteration of -en, from Greek -ēnē).] American Heritage® Dictionary of the English Language, Fifth Edition. Copyright © 2016 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved. ketone (ˈkiːtəʊn) [C19: from German Keton, from Aketon acetone] Collins English Dictionary – Complete and Unabridged, 12th Edition 2014 © HarperCollins Publishers 1991, 1994, 1998, 2000, 2003, 2006, 2007, 2009, 2011, 2014 ke•tone (ˈki toʊn) n. any of a class of organic compounds containing a carbonyl group, CO, attached to two alkyl groups, as CH3COCH3. Random House Kernerman Webster's College Dictionary, © 2010 K Dictionaries Ltd. Copyright 2005, 1997, 1991 by Random House, Inc. All rights reserved. ke·tone (kē′tōn′) Any of a class of organic compounds, such as acetone, having a group consisting of a carbon and an oxygen atom (CO) joined on either side to a carbon atom of a hydrocarbon radical. The American Heritage® Student Science Dictionary, Second Edition. Copyright © 2014 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved. Noun 1. ketone - any of a class of organic compounds having a carbonyl group linked to a carbon atom in each of two hydrocarbon radicalsnabumetone, Relafen - a nonsteroidal anti-inflammatory drug (trade name Relafe Continue reading >>

Regulation Of Ketone Body Production: Answer

Regulation Of Ketone Body Production: Answer

What regulates ketone body synthesis? The primary regulator of ketone body synthesis is fatty acid availability. When hormonal conditions (e.g., high glucagon, low insulin) cause fatty acid concentration in the plasma to be high, malonyl CoA concentration in the liver cytoplasm is low (because acetyl CoA carboxylase is in the less active phosphorylated state). Fatty acyl CoA can enter the mitochondria at a high rate (because there is no inhibition of CAT I), and beta-oxidation proceeds at a high rate. The ensuing high mitochondrial concentration of acetyl CoA results in active ketone body synthesis. Continue reading >>

Synthesis And Degradation Of Ketone Bodies (homo Sapiens)

Synthesis And Degradation Of Ketone Bodies (homo Sapiens)

Description Ketone bodies are three water-soluble compounds that are produced as by-products when fatty acids are broken down for energy in the liver and kidney. They are used as a source of energy in the heart and brain. In the brain, they are a vital source of energy during fasting. Source: Wikipedia Ontology Terms Compare Revision Action Time User Comment 68921FeaturedApproved view 17:32, 8 July 2013 MaintBot Updated to 2013 gpml schema 67674 view 11:47, 26 June 2013 Ddigles Ontology Term : 'ketone bodies metabolic pathway' added ! 61697 view 23:23, 16 April 2013 MaintBot removed data source without identifer 48248 view 06:21, 17 May 2012 MaintBot Updating PubChem xrefs 48220 view 05:29, 17 May 2012 MaintBot Automatic update of PubChem xrefs 45110 view 22:36, 6 October 2011 Khanspers Ontology Term : 'ketone bodies biosynthetic pathway' added ! 45108 view 22:36, 6 October 2011 Khanspers Ontology Term : 'ketone bodies degradation pathway' added ! 43510 view 09:33, 24 June 2011 AdrienDefay add database name + database ID 41068 view 23:19, 1 March 2011 MaintBot Removed redundant pathway information and comments 38846 view 17:47, 24 September 2010 Khanspers 38738 view 21:54, 23 September 2010 Khanspers Changed interactions 38736 view 21:52, 23 September 2010 Khanspers Added pathway links, Changed lines 38735 view 21:47, 23 September 2010 Khanspers Added pathway links 35389 view 09:33, 12 February 2010 Thomas fixed connections 35359 view 09:09, 12 February 2010 Thomas fixed reference 35355 view 09:07, 12 February 2010 Thomas Modified description 35354 view 09:07, 12 February 2010 Thomas added literature 34452 view 18:23, 10 December 2009 MaintBot Automatic update of empty xrefs 21335 view 11:31, 14 November 2008 MaintBot [[Pathway:Homo sapiens:Synthesis and Degradation of Continue reading >>

Ketone Bodies Formed In The Liver Are Exported To Other Organs

Ketone Bodies Formed In The Liver Are Exported To Other Organs

Ketone Bodies In human beings and most other mammals, acetyl-CoA formed in the liver during oxidation of fatty acids may enter the citric acid cycle (stage 2 of Fig. 16-7) or it may be converted to the "ketone bodies" acetoacetate, D-β-hydroxybutyrate, and acetone for export to other tissues. (The term "bodies" is a historical artifact; these compounds are soluble in blood and urine.) Acetone, produced in smaller quantities than the other ketone bodies, is exhaled. Acetoacetate and D-β-hydroxybutyrate are transported by the blood to the extrahepatic tissues, where they are oxidized via the citric acid cycle to provide much of the energy required by tissues such as skeletal and heart muscle and the renal cortex. The brain, which normally prefers glucose as a fuel, can adapt to the use of acetoacetate or D-β-hydroxybutyrate under starvation conditions, when glucose is unavailable. A major determinant of the pathway taken by acetyl-CoA in liver mitochondria is the availability of oxaloacetate to initiate entry of acetyl-CoA into the citric acid cycle. Under some circumstances (such as starvation) oxaloacetate is drawn out of the citric acid cycle for use in synthesizing glucose. When the oxaloacetate concentration is very low, little acetyl-CoA enters the cycle, and ketone body formation is favored. The production and export of ketone bodies from the liver to extrahepatic tissues allows continued oxidation of fatty acids in the liver when acetyl-CoA is not being oxidized via the citric acid cycle. Overproduction of ketone bodies can occur in conditions of severe starvation and in uncontrolled diabetes. The first step in formation of acetoacetate in the liver (Fig. 16-16) is the enzymatic condensation of two molecules of acetyl-CoA, catalyzed by thiolase; this is simply Continue reading >>

Ketone Bodies

Ketone Bodies

Introductory discusion of fat metabolism, exercise, and fasting. Fatty acids can be used as the major fuel for tissues such as muscle, but they cannot cross the blood-brain barrier, and thus cannot be used by the central nervous system (CNS). This becomes a major problem during starvation (fasting), particularly for organisms such as ourselves in which CNS metabolism constitute a major portion of the resting basal metabolic rate. These organism must provide glucose to the CNS to provide for metabolic needs, and thus during the initial fasting period must break down substantial amounts of muscle tissue (protein) to provide the amino acid precursors of gluconeogenesis. Obviously the organism could not survive long under such a regime. What is needed is an alternate fuel source based on fat rather than muscle. The so-called ketone bodies serve this function: Note that only two of the ketone bodies are in fact ketones, and that acetone is an "unintentional" breakdown product resulting from the instability of acetoacetate at body temperature. Acetone is not available as fuel to any significant extent, and is thus a waste product. CNS tissues can use ketone bodies any time, the problem is the normally very low concentrations (< 0.3 mM) compared to glucose (about 4 mM). Since the KM's for both are similar, the CNS doesn't begin to use ketone bodies in preference to glucose until their concentration exceed's the concentration of glucose in the serum. The system becomes saturated at about 7 mM. The limiting factor in using ketone bodies then becomes the ability of the liver to synthesis them, which requires the induction of the enzymes required for acetoacetate biosynthesis. Normal glucose concentrations inhibit ketone body synthesis, thus the ketone bodies will only begin to be Continue reading >>

What Are Ketone Bodies And Why Are They In The Body?

What Are Ketone Bodies And Why Are They In The Body?

If you eat a calorie-restricted diet for several days, you will increase the breakdown of your fat stores. However, many of your tissues cannot convert these fatty acid products directly into ATP, or cellular energy. In addition, glucose is in limited supply and must be reserved for red blood cells -- which can only use glucose for energy -- and brain tissues, which prefer to use glucose. Therefore, your liver converts many of these fatty acids into ketone bodies, which circulate in the blood and provide a fuel source for your muscles, kidneys and brain. Video of the Day Low fuel levels in your body, such as during an overnight fast or while you are dieting, cause hormones to increase the breakdown of fatty acids from your stored fat tissue. These fatty acids travel to the liver, where enzymes break the fatty acids into ketone bodies. The ketone bodies are released into the bloodstream, where they travel to tissues that have the enzymes to metabolize ketone bodies, such as your muscle, brain, kidney and intestinal cells. The breakdown product of ketone bodies goes through a series of steps to form ATP. Conditions of Ketone Body Utilization Your liver will synthesize more ketone bodies for fuel whenever your blood fatty acid levels are elevated. This will happen in response to situations that promote low blood glucose, such as an overnight fast, prolonged calorie deficit, a high-fat and low-carbohydrate diet, or during prolonged low-intensity exercise. If you eat regular meals and do not typically engage in extremely long exercise sessions, the level of ketone bodies in your blood will be highest after an overnight fast. This level will drop when you eat breakfast and will remain low as long as you eat regular meals with moderate to high carbohydrate content. Ketone Bodi Continue reading >>

6.9: Ketone Body Synthesis

6.9: Ketone Body Synthesis

In ketone body synthesis, an acetyl-CoA is split off from HMG-CoA, yielding acetoacetate, a four carbon ketone body that is somewhat unstable, chemically. It will decarboxylate spontaneously to some extent to yield acetone. Ketone bodies are made when the blood levels of glucose fall very low. Ketone bodies can be converted to acetyl-CoA, which can be used for ATP synthesis via the citric acid cycle. People who are very hypoglycemic (including some diabetics) will produce ketone bodies and these are often first detected by the smell of acetone on their breath. Figure 6.9.1: Ketone Body Reactions Acetone is of virtually no use for energy production since it is not readily converted to acetyl-CoA. Consequently, cells convert acetoacetate into beta- hydroxybutyrate, which is more chemically stable. Though technically not a ketone, beta-hydroxybutyrate is frequently referred to as a ketone body. Upon arrival at a target cell, it can be oxidized back to acetoacetate with conversion to acetyl-CoA. Both acetoacetate and beta-hydroxybutyrate can cross the blood-brain barrier and provide important energy for the brain when glucose is limiting. Continue reading >>

6 Health Benefits Of Ketogenesis And Ketone Bodies

6 Health Benefits Of Ketogenesis And Ketone Bodies

With heavy coverage in the media, ketogenic diets are all the rage right now. And for a good reason; for some people, they truly work. But what do all these different terms like ketogenesis and ketone bodies actually mean? Firstly, this article takes a look at what the ketogenesis pathway is and what ketone bodies do. Following this, it will examine six potential health benefits of ketones and nutritional ketosis. What is Ketogenesis? Ketogenesis is a biochemical process through which the body breaks down fatty acids into ketone bodies (we’ll come to those in a minute). Synthesis of ketone bodies through ketogenesis kicks in during times of carbohydrate restriction or periods of fasting. When carbohydrate is in short supply, ketones become the default energy source for our body. As a result, a diet to induce ketogenesis should ideally restrict carb intake to a maximum of around 50 grams per day (1, 2). Ketogenesis may also occur at slightly higher levels of carbohydrate intake, but for the full benefits, it is better to aim lower. When ketogenesis takes place, the body produces ketone bodies as an alternative fuel to glucose. This physiological state is known as ‘nutritional ketosis’ – the primary objective of ketogenic diets. There are various methods you can use to test if you are “in ketosis”. Key Point: Ketogenesis is a biological pathway that breaks fats down into a form of energy called ketone bodies. What Are Ketone Bodies? Ketone bodies are water-soluble compounds that act as a form of energy in the body. There are three major types of ketone body; Acetoacetate Beta-hydroxybutyrate Acetone (a compound created through the breakdown of acetoacetate) The first thing to remember is that these ketones satisfy our body’s energy requirements in the same w Continue reading >>

Ketone

Ketone

(redirected from Synthesis and degradation of ketone bodies) Also found in: Dictionary, Thesaurus, Encyclopedia. ketone [ke´tōn] any compound containing the carbonyl group, C=O, and having hydrocarbon groups attached to the carbonyl carbon, i.e., the carbonyl group is within a chain of carbon atoms. ketone bodies the substances acetone, acetoacetic acid, and β-hydroxybutyric acid; except for acetone (which may arise spontaneously from acetoacetic acid), they are normal metabolic products of lipid and pyruvate within the liver, and are oxidized by muscles. Excessive production leads to urinary excretion of these bodies, as in diabetes mellitus; see also ketosis. Called also acetone bodies. Miller-Keane Encyclopedia and Dictionary of Medicine, Nursing, and Allied Health, Seventh Edition. © 2003 by Saunders, an imprint of Elsevier, Inc. All rights reserved. ke·tone (kē'tōn), Any organic compound in which two carbon atoms are linked by the carbon of a carbonyl group (C-O). The simplest ketone and the most important in medicine is dimethyl ketone (acetone). ketone /ke·tone/ (ke´tōn) any of a class of organic compounds containing the carbonyl group, CdbondO, whose carbon atom is joined to two other carbon atoms, i.e., with the carbonyl group occurring within the carbon chain. ketone (kē′tōn′) n. 1. Any of a class of organic compounds, such as acetone, characterized by having a carbonyl group in which the carbon atom is bonded to two other hydrocarbon groups and having the general formula R(CO)R′, where R may be the same as R′. ketone an organic chemical compound characterized by having in its structure a carbonyl, or keto, group, ═CO, attached to two alkyl groups. It is produced by oxidation of secondary alcohols. ke·tone (kē'tōn) A substance with the Continue reading >>

Ketone Body Synthesis

Ketone Body Synthesis

Sort 1. Ketone body synthesis: Ketone bodies are x forms of lipid-based energy and consist mainly of x acid and its reduction product, x acid. β-hydroxybutyryl CoA and acetoacetyl CoA are x near the end of the β-oxidation scheme. x in an intermediate in the synthesis of acetoacetate from Acetyl CoA The primary site for formation of ketone bodies is x, with lesser activity in x. The entire process occurs within the x, beginning with condensation of two acetyl CoA molecules to make acetoacetyl CoA, as catalyzed by xase. Acetoacetyl CoA then condenses with another acetyl CoA to form β- hydroxymethylglutaryl coenzyme A (aka x). Cleavage of HMG CoA by HMG CoA xase yields acetoacetic acid and acetyl CoA. 1. Ketone body synthesis: Ketone bodies are water soluble forms of lipid-based energy and consist mainly of acetoacetic acid and its reduction product, β-hydroxybutyric acid. β-hydroxybutyryl CoA and acetoacetyl CoA are intermediates near the end of the β-oxidation scheme. HMG-CoA in an intermediate in the synthesis of acetoacetate from Acetyl CoA The primary site for formation of ketone bodies is liver, with lesser activity in kidney. The entire process occurs within the mitochondrial matrix, beginning with condensation of two acetyl CoA molecules to make acetoacetyl CoA, as catalyzed by β-ketothiolase. Acetoacetyl CoA then condenses with another acetyl CoA to form β- hydroxymethylglutaryl coenzyme A (aka HMG CoA). Cleavage of HMG CoA by HMG CoA Lyase yields acetoacetic acid and acetyl CoA. Acetoacetate Forms both D-β-Hydroxybutyrate and acetone In mitochondria a fraction of acetoacetate is reduced to D-β-hydroxybutyrate depending on the intramitochondrial x ratio. Some acetoacetate continually undergoes slow spontaneous nonx decarboxylation to acetone. In these pa Continue reading >>

Ketone Body Metabolism

Ketone Body Metabolism

Ketone body metabolism includes ketone body synthesis (ketogenesis) and breakdown (ketolysis). When the body goes from the fed to the fasted state the liver switches from an organ of carbohydrate utilization and fatty acid synthesis to one of fatty acid oxidation and ketone body production. This metabolic switch is amplified in uncontrolled diabetes. In these states the fat-derived energy (ketone bodies) generated in the liver enter the blood stream and are used by other organs, such as the brain, heart, kidney cortex and skeletal muscle. Ketone bodies are particularly important for the brain which has no other substantial non-glucose-derived energy source. The two main ketone bodies are acetoacetate (AcAc) and 3-hydroxybutyrate (3HB) also referred to as β-hydroxybutyrate, with acetone the third, and least abundant. Ketone bodies are always present in the blood and their levels increase during fasting and prolonged exercise. After an over-night fast, ketone bodies supply 2–6% of the body's energy requirements, while they supply 30–40% of the energy needs after a 3-day fast. When they build up in the blood they spill over into the urine. The presence of elevated ketone bodies in the blood is termed ketosis and the presence of ketone bodies in the urine is called ketonuria. The body can also rid itself of acetone through the lungs which gives the breath a fruity odour. Diabetes is the most common pathological cause of elevated blood ketones. In diabetic ketoacidosis, high levels of ketone bodies are produced in response to low insulin levels and high levels of counter-regulatory hormones. Ketone bodies The term ‘ketone bodies’ refers to three molecules, acetoacetate (AcAc), 3-hydroxybutyrate (3HB) and acetone (Figure 1). 3HB is formed from the reduction of AcAc i Continue reading >>

Ketone Body Synthesis

Ketone Body Synthesis

Types of Ketone Bodies and Their Function There are three substances in our body that are considered ketone bodies: Acetoacetate is a metabolic product of the liver. It can be converted into acetone and beta-hydroxybutyrate. Acetone is a product of spontaneous decarboxylation of acetoacetate or via the action of acetoacetate decarboxylase. It is disposed of with the respiratory air or in the urine. Acetone does not have any function in our metabolism. Beta-hydroxybutyrate is not a ketone body strictly speaking. It is derived from acetoacetate via the action of D-beta hydroxy butyrate dehydrogenase. It is the most abundant ketone body. Acetoacetate and beta-hydroxybutyrate are only synthesized in the mitochondrial matrix of hepatocytes. Brain, myocardial and skeletal muscles all rely on the re-conversion of these substances in times of low glucose levelssince they can traverse membranes easily. Since the brain cannot use fatty acids for energy generation because the blood-brain barrier is not permeable to fatty acids, it is dependent on ketone bodies in periods of fasting as its sole energy resource. Using ketone bodies, the brain can reduce its glucose demand from an average of about 150g/day to about 50g/day.They are transported to the brain via monocarboxylate transporters 1 and 2. Activation of Ketone Body Synthesis From a biochemical perspective, ketone body synthesis will be reinforced whenever there is an increased presence of acetyl-CoA (the starting substance of ketone body synthesis), as is the case during longer periods of fasting or starvation. Furthermore, diabetes mellitus causes an accumulation of acetyl-CoA: the lower insulin production or higher insulin resistance leads to an increase in the degradation of fatty acids which, in turn, leads to more acetyl Continue reading >>

Ketone Bodies As Signaling Metabolites

Ketone Bodies As Signaling Metabolites

Outline of ketone body metabolism and regulation. The key irreversible step in ketogenesis is synthesis of 3-hydroxy-3-methylglutaryl-CoA by HMGCS2. Conversely, the rate limiting step in ketolysis is conversion of acetoacetate to acetoacetyl-CoA by OXCT1. HMGCS2 transcription is heavily regulated by FOXA2, mTOR, PPARα, and FGF21. HMGCS2 activity is post-translationally regulated by succinylation and acetylation/SIRT3 deacetylation. Other enzymes are regulated by cofactor availability (e.g., NAD/NADH2 ratio for BDH1). All enzymes involved in ketogenesis are acetylated and contain SIRT3 deacetylation targets, but the functional significance of this is unclear other than for HMGCS2. Although ketone bodies are thought to diffuse across most plasma membranes, the transporter SLC16A6 may be required for liver export, whereas several monocarboxylic acid transporters assist with transport across the blood–brain barrier. Abbreviations: BDH1, β-hydroxybutyrate dehydrogenase; FGF21, fibroblast growth factor 21; FOXA2, forkhead box A2; HMGCS2, 3-hydroxy-3-methylglutaryl (HMG)-CoA synthase 2; HMGCL, HMG-CoA lyase; MCT1/2, monocarboxylic acid transporters 1/2; mTOR, mechanistic target of rapamycin; OXCT1, succinyl-CoA:3-ketoacid coenzyme A transferase; PPARα, peroxisome proliferator-activated receptor α; SIRT3, sirtuin 3; SLC16A6, solute carrier family 16 (monocarboxylic acid transporter), member 6; TCA cycle, tricarboxylic acid cycle. Continue reading >>

Ketone Bodies

Ketone Bodies

The use of ketone bodies as fuel by most tissues during a fast reduces the need for gluconeogenesis from amino acid carbon skeletons, slowing the loss of essential protein. During a fast, the liver is flooded with liberated FAs from adipose tissue. Liver mitochondria have the capacity to convert excess acetyl CoA, derived from fatty acid oxidation, into ketone bodies when the amount of Acetyl CoA exceeds oxidative capacity. These include acetoacetate, 3-hydroxybutyrate, and acetone. As ketone bodies are soluble, they can be transported in the blood to peripheral tissues where they can be reconverted into Acetyl CoA and oxidized in the TCA cycle. Production of Ketone Bodies During a fast, the liver is flooded with liberated FAs from adipose tissue. This inhibits pyruvate dehydrogenase in the TCA cycle and activates pyruvate carboxylase, shunting pyruvate towards OAA for transport out of the mitochondria and into gluconeogenesis. This leaves Acetyl CoA available for ketone body synthesis. Use of Ketone Bodies Ketone bodies are reconverted into acetyl CoA in the periphery, including brain, heart and muscle, although the liver cannot use them as fuel. Excessive Production of Ketone Bodies Excessive ketone production results in ketonemia and ketonuria, often observed in Type I diabetes. This results from high levels of fatty acid degradation and concomitant acetyl CoA synthesis. In diebetic individuals, urinary excretion can be as high as 5000 mg/d, and blood levels can go from 3 mg/dl (normal) to 90 mg/dl. Elevated ketone levels causes acidemia, as the pKa of the carboxyl group is 4. Excretion of glucose and ketone bodies also causes dehydration, and as a result, profound acidosis can occur. Ketoacidosis can also be the result of profound fasting. This information is for tr Continue reading >>

Introduction To Degradation Of Lipids And Ketone Bodies Metabolism

Introduction To Degradation Of Lipids And Ketone Bodies Metabolism

Content: 1. Introduction to degradation of lipids and ketone bodies metabolism 2. Lipids as source of energy – degradation of TAG in cells, β-oxidation of fatty acids 3. Synthesis and utilisation of ketone bodies _ Triacylglycerol (TAG) contain huge amounts of chemical energy. It is very profitable to store energy in TAG because 1 g of water-free TAG stores 5 times more energy than 1 g of hydrated glycogen. Complete oxidation of 1 g of TAG yields 38 kJ, 1g of saccharides or proteins only 17 kJ. Man that weighs 70 kg has 400 000 kJ in his TAG (that weight approximately 10,5 kg). This reserve of energy makes us able to survive starving in weeks. TAG accumulate predominantly in adipocyte cytoplasm. There are more types of fatty acid oxidation. Individual types can be distinguished by different Greek letters. Greek letter denote atom in the fatty acid chain where reactions take place. β-oxidation is of major importance, it is localised in mitochondrial matrix. ω- and α- oxidation are localised in endoplasmic reticulum. Animal cells cannot convert fatty acids to glucose. Gluconeogenesis requires besides other things (1) energy, (2) carbon residues. Fatty acids are rich source of energy but they are not source of carbon residues (there is however one important exception, i.e. odd-numbered fatty acids). This is because cells are not able to convert AcCoA to neither pyruvate, nor OAA. Both carbons are split away as CO2. PDH is irreversible. Plant cells are capable of conversion of AcCoA to OAA in glyoxylate cycle. _ Lipids as source of energy – degradation of TAG in cells, β-oxidation of fatty acids Lipids are used for energy production, this process take place in 3 phases: 1) Lipid mobilisation – hydrolysis of TAG to FA and glycerol. FA and glycerol are transported Continue reading >>

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