Ketone Bodies,Yapa Wijeratne
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Ketone bodies are synthesized in the liver from fatty acids and are utilized by extrahepatic tissues as an energy source when glucose levels are low, such as during fasting or carbohydrate restriction. The three main ketone bodies are acetoacetate, beta-hydroxybutyrate, and acetone. Ketogenesis is regulated by the mobilization of fatty acids from adipose tissue and the partitioning of acetyl-CoA between the ketogenesis pathway and the citric acid cycle in the liver. Elevated levels of ketone bodies in the blood (ketonemia) or urine (ketonuria), known as ketosis, can occur during starvation, prolonged exercise, or in pathological states like uncontrolled diabetes mellitus.
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![Ketone bodies<br />Synthesis & oxidation<br />Ketone bodies<br />Acetoacetate (Acetoacetic acid)<br />ßHBA-ß-hydroxybutyrate (3-hydroxybutyrate)<br />Acetone<br />These three substances are collectively known as the ketone bodies<br />Ketogenesis Occurs When There Is a High Rate of Fatty Acid Oxidation in the Liver.(when the amount of acetyl CoA exceeds the oxidative capacity)<br />[Total ketone bodies]in the blood of well-fed mammals does not normally exceed 0.2 mmol/L except in ruminants.<br />Extrahepatic tissues utilize them as respiratory substrates.( in starvation)<br />Skeletal muscles<br />Cardiac muscles<br />Renal cortex<br />Brain <br />Enzymes responsible for ketone body formation are associated mainly with the mitochondria. So not in RBC.<br />3-hydroxy-3-methylglutaryl-CoA synthase <br />3-Hydroxy-3-methylglutaryl-CoA lyase <br />Both enzymes must be present in mitochondria for ketogenesis to take place. <br />This occurs solely in liver and rumen epithelium. <br />ßHBA is quantitatively the predominant ketone body present in the blood and urine in ketosis.<br />Acetoacetate only oxidize among Ketone bodies<br />ßHBA<br />Acetone no use for the cell<br />No regulatory point in Ketogenesis pathway. Only regulation is Acetyl CoA.<br />Ketogenesis is regulated at 3 crucial steps: <br />(1) control of free fatty acid mobilization from adipose tissue.<br />Free fatty acids are the precursors of ketone bodies in the liver.<br />The factors regulating mobilization of free fatty acids from adipose tissue are important in controlling ketogenesis<br />(2) the activity of carnitine palmitoyltransferase-I (CPT-1)in liver, which determines the proportion of the fatty acid flux that is oxidized rather than esterified.<br />(3) partition of acetyl-CoA between the pathway of ketogenesis and the citric acid cycle. <br />Utilization of Ketone bodies<br />Liver produces Ketone bodies<br />Liver cannot use Acetoacetate as fuel.(lacks the enzyme for conversion of Acetoacetate> Acetoacetyl CoA)<br />Acetoacetyl CoA > 2 Acetyl CoA<br />Clinical Aspects<br />Higher than normal quantities of ketone bodies present in the blood (ketonemia (hyperketonemia) ) or urine (ketonuria)<br />The overall condition is called ketosis. <br />The basic form of ketosis occurs in starvation and involves depletion of available carbohydrate coupled with mobilization of free fatty acids.<br />During fasting or carbohydrate starvation, OAA is depleted in liver due to gluconeogenesis. This impedes entry of Acetyl CoA -> Krebs cycle <br />This general pattern of metabolism is exaggerated to produce the pathologic states found in diabetes mellitus & ….<br />Nonpathologic forms of ketosis are found under conditions of high-fat feeding and after severe exercise in the postabsorptive state.<br />Acetoacetic and ßHBA are both moderately strong acids and are buffered when present in blood or other tissues. However, their continual excretion in quantity progressively depletes the alkali reserve, causing ketoacidosis. This may be fatal in uncontrolled diabetes mellitus.<br />](https://image.slidesharecdn.com/ketonebodies-100324132715-phpapp02/85/Ketone-Bodies-Yapa-Wijeratne-1-320.jpg)
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bio%20lecture.pptx
1. Ketone bodies like acetoacetic acid and beta-hydroxybutyric acid are produced in the liver from fatty acids and serve as an alternative fuel for tissues during periods of low glucose such as fasting or starvation.
2. Ketogenesis is regulated by fatty acid levels, carnitine palmitoyl transferase 1 activity, and the partitioning of acetyl-CoA between the citric acid cycle and ketone body synthesis.
3. Pathological ketosis can occur in uncontrolled diabetes when insulin is low and fatty acids are broken down but cannot be used for energy due to lack of glucose, leading to excess ketone production.
Ketone Bodies.pptx
Ketone bodies are produced by the liver and used peripherally as an energy source when glucose is not readily available.
Ketone bodies.pptx
Ketone bodies are water soluble molecules that contain the ketone groups produced from fatty acids by the liver.
biochm ketons new.pptx
The document discusses ketone bodies, which are water-soluble compounds produced by the liver from fatty acids during times of low blood glucose such as fasting or a low-carbohydrate diet. The three main ketone bodies are acetoacetate, acetone, and beta-hydroxybutyrate. They are released from the liver and used by tissues like the brain and heart as an energy source when glucose levels are low. Conditions like prolonged fasting, starvation, untreated type 1 diabetes, or a very low-carb diet can lead to ketosis, which occurs when ketone body levels in the blood and urine are high.
Ketone bodies
Ketone Bodies
Fatty acids undergo 𝛽-oxidation in the liver mitochondria to generate a high amount of energy and form three compounds, that are known as “ketone bodies”. These ketone bodies are water-soluble and do not require lipoproteins for transportation across the membrane. Ketone bodies are lipid molecules having a carbonyl group attached to two -R groups.
The three ketone bodies formed are –
1. Acetoacetate
2. D-3-hydroxybutyrate
3. Acetone
Ketogenesis – Definition
Ketogenesis is a catabolic pathway of metabolism. In this process, fatty acids and certain ketogenic amino acids are broken down to derive energy by alternative means. Ketone bodies are produced in the ketogenesis process.
Our body continuously produces ketone bodies in low amounts, but in certain cases like starving, when carbohydrates are present in less amount in diet, ketogenesis is preferred to compensate for the energy requirements.
Ketone bodies accumulated in an excess amount may lead to a condition called ketoacidosis, which may be fatal.
Ketogenesis Pathway
Our body normally derives energy from stored carbohydrate by the process of glycogenolysis (glycogen → glucose) or from non-carbohydrate sources such as lactate by the process of gluconeogenesis.
Ketogenesis occurs continuously in a healthy individual, but under certain conditions, when there is an increased concentration of fatty acids or carbohydrate reserves are decreased, ketogenesis happens at a higher rate:
• Under low blood glucose level, e.g. during fasting or starvation
• On exhaustion of carbohydrate reserve, e.g. glycogen
• When there is insufficient insulin, e.g. Type-1 diabetes
All the main body parts such as the brain, skeletal muscles, heart, etc. can utilise the energy formed by ketogenesis.
Insufficient gluconeogenesis results in hypoglycemia and excessive production of ketone bodies resulting in a fatal condition called ketoacidosis.
Ketogenesis Steps
The ketogenesis process occurs primarily in the mitochondria of liver cells. Below are the steps in the process of ketogenesis:
1. Transfer of fatty acids in mitochondria by carnitine palmitoyltransferase CPT-1
2. 𝛽-oxidation of fatty acid to form acetyl CoA
3. Acetoacetyl-CoA formation: 2 acetyl CoA form acetoacetyl CoA. The reaction is catalyzed by the enzyme thiolase
4. 3-hydroxy-3-methylglutaryl-CoA (HMG-CoA) synthesis: the step is catalyzed by HMG-CoA synthase
5. Acetoacetate formation: HMG-CoA is broken down to acetoacetate and acetyl-CoA by the action of HMG-CoA lyase
Acetoacetate thus produced forms other ketone bodies, acetone by decarboxylation and D-3-hydroxybutyrate by reduction.
Significance of Ketogenesis
• Ketogenesis is used to get energy by the brain, heart and skeletal muscles under fasting condition
• The ketogenic diet (low-carb, fat-rich diet) is used these days to lose weight.
Ketosis a quick revision
This document discusses ketone bodies and ketosis. It defines ketone bodies as water-soluble transporters of acetyl units produced in the liver from fatty acids during periods of low carbohydrate availability. The three main ketone bodies are acetoacetate, beta-hydroxybutyrate, and acetone. Ketone bodies serve as an alternative fuel for tissues like the brain during glucose deprivation. The document outlines the pathways of ketone body synthesis in the liver and utilization in other tissues, as well as conditions that cause excess ketone production (ketosis).
Lipid Metabolism, Energy yield from fatty acid oxidation & ketone bodies
1. Lipid metabolism yields a high amount of energy through the beta-oxidation pathway. The oxidation of palmitoyl CoA produces 8 acetyl CoA molecules, 7 NADH molecules, and 7 FADH2 molecules, which can generate a total of 131 ATP molecules, with a net yield of 129 ATP after accounting for activation costs.
2. Ketone bodies, including acetoacetate, beta-hydroxybutyrate, and acetone, are produced by the liver during periods of fasting and starvation from acetyl CoA generated through fatty acid oxidation. Ketone bodies can be used as an energy source by tissues like brain and muscle.
3. During fasting, fatty acids are oxid
907471 properties-of-triacylglycerols
The document discusses various topics related to lipids and their metabolism, including the properties and breakdown of triglycerides, cholesterol metabolism and its role in atherosclerosis, ketone body formation during fasting as an energy source, and diabetic ketoacidosis resulting from high levels of ketone bodies in the blood. It also provides information on examville.com, an online resource for practice tests, classes, tutoring and other educational materials.
907471 properties-of-triacylglycerols
The document discusses various topics related to lipids and their metabolism, including the properties and reactions of triacylglycerols, cholesterol metabolism and its role in atherosclerosis, ketone body formation and their role as an energy source, particularly for the brain during periods of starvation. Atherosclerosis results from elevated cholesterol levels, especially LDL cholesterol, and diet and exercise can help lower cholesterol. Ketone bodies are produced from fatty acids and certain amino acids in the liver during periods of fasting or low carbohydrate availability and serve as an energy source.
Metabolism of ketone bodies
The document discusses ketone body metabolism. It states that during prolonged starvation or fasting, ketone bodies including acetone, acetoacetate, and beta-hydroxybutyrate are produced in the liver from acetyl-CoA. This is because oxaloacetate is depleted due to gluconeogenesis, preventing acetyl-CoA from entering the Krebs cycle. Ketone bodies can then be used as an alternative fuel source by tissues like the heart, kidney, and muscle. Their overproduction can lead to ketoacidosis.
ketogenesis and utilisation of ketone bodies.pptx
The document discusses ketone bodies, which are produced when fatty acids are broken down in excess. The three major ketone bodies are acetoacetate, acetone, and beta-hydroxybutyrate. Ketone bodies are an alternative energy source and are produced when glucose availability is limited, such as during starvation or uncontrolled diabetes. They are synthesized in the liver and can be used by tissues like the brain. Conditions that result in excessive ketone body production are called ketosis.
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KETONE BODY METABOLISM. FOR MBBS, BDS, LABORATORY MEDICINE pptx
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Ketone Bodies,Yapa Wijeratne
- 1. Ketone bodies<br />Synthesis & oxidation<br />Ketone bodies<br />Acetoacetate (Acetoacetic acid)<br />ßHBA-ß-hydroxybutyrate (3-hydroxybutyrate)<br />Acetone<br />These three substances are collectively known as the ketone bodies<br />Ketogenesis Occurs When There Is a High Rate of Fatty Acid Oxidation in the Liver.(when the amount of acetyl CoA exceeds the oxidative capacity)<br />[Total ketone bodies]in the blood of well-fed mammals does not normally exceed 0.2 mmol/L except in ruminants.<br />Extrahepatic tissues utilize them as respiratory substrates.( in starvation)<br />Skeletal muscles<br />Cardiac muscles<br />Renal cortex<br />Brain <br />Enzymes responsible for ketone body formation are associated mainly with the mitochondria. So not in RBC.<br />3-hydroxy-3-methylglutaryl-CoA synthase <br />3-Hydroxy-3-methylglutaryl-CoA lyase <br />Both enzymes must be present in mitochondria for ketogenesis to take place. <br />This occurs solely in liver and rumen epithelium. <br />ßHBA is quantitatively the predominant ketone body present in the blood and urine in ketosis.<br />Acetoacetate only oxidize among Ketone bodies<br />ßHBA<br />Acetone no use for the cell<br />No regulatory point in Ketogenesis pathway. Only regulation is Acetyl CoA.<br />Ketogenesis is regulated at 3 crucial steps: <br />(1) control of free fatty acid mobilization from adipose tissue.<br />Free fatty acids are the precursors of ketone bodies in the liver.<br />The factors regulating mobilization of free fatty acids from adipose tissue are important in controlling ketogenesis<br />(2) the activity of carnitine palmitoyltransferase-I (CPT-1)in liver, which determines the proportion of the fatty acid flux that is oxidized rather than esterified.<br />(3) partition of acetyl-CoA between the pathway of ketogenesis and the citric acid cycle. <br />Utilization of Ketone bodies<br />Liver produces Ketone bodies<br />Liver cannot use Acetoacetate as fuel.(lacks the enzyme for conversion of Acetoacetate> Acetoacetyl CoA)<br />Acetoacetyl CoA > 2 Acetyl CoA<br />Clinical Aspects<br />Higher than normal quantities of ketone bodies present in the blood (ketonemia (hyperketonemia) ) or urine (ketonuria)<br />The overall condition is called ketosis. <br />The basic form of ketosis occurs in starvation and involves depletion of available carbohydrate coupled with mobilization of free fatty acids.<br />During fasting or carbohydrate starvation, OAA is depleted in liver due to gluconeogenesis. This impedes entry of Acetyl CoA -> Krebs cycle <br />This general pattern of metabolism is exaggerated to produce the pathologic states found in diabetes mellitus & ….<br />Nonpathologic forms of ketosis are found under conditions of high-fat feeding and after severe exercise in the postabsorptive state.<br />Acetoacetic and ßHBA are both moderately strong acids and are buffered when present in blood or other tissues. However, their continual excretion in quantity progressively depletes the alkali reserve, causing ketoacidosis. This may be fatal in uncontrolled diabetes mellitus.<br />