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Where Are Ketone Bodies Broken Down?

How Your Body Fights To Keep You Alive When You’re Starving

How Your Body Fights To Keep You Alive When You’re Starving

The human body can go without oxygen for about five to ten minutes, and about three to eight days without water. But remarkably, people have been known to live upwards of 70 days without food. How is this possible? The answer lies in a series of evolved physiological and metabolic defenses that work to keep you alive for as long as possible in the unfortunate event that you don't have access to food. Just because you're starving doesn't mean you've become helpless. Here's how your body fights to keep you alive and active. By definition, starvation is a process. Our bodies are not like cars which immediately shut down when they're out of gas. When we experience prolonged low energy intake, and as long as water is available, our bodies enter into a successive series of metabolic modes. It's the body's way of recognizing that food is scarce, and that it needs to re-allocate resources in preparation for what could be an extended period. In essence, your body is buying you some valuable time to give you a fair chance of finding some food. 0-6 hours after eating Soon after eating, our bodies start to break down glycogen (molecules that store energy) to produce glucose (an important carbohydrate that fuels cells). When we're eating normally, we use glucose as our primary fuel source; all is well, we're happy, and in storage mode. Glucose gets packed into our liver and muscle, with the fatty acids getting stored around our body for (potential) future use. In terms of energy allocation, our brains require 25% of the body's total stored energy (which is a lot if you think about it), with the rest going to fuel our muscle tissues and red blood cells. We can go for about six hours in this glucose-burning mode, which is why we tend to get a bit cranky if we have to go without food f Continue reading >>

What Are Ketones?

What Are Ketones?

With the gradual resurgence of low-carb diets in recent years, the word “ketones” is thrown around a lot. But many people aren’t really aware of the details. What are ketones, really? And what do they do in the body? There can be a lot of misinformation regarding the answers to these questions, so read on for a full overview of ketones and their role in a ketogenic diet. Ketones, also known as “ketone bodies,” are byproducts of the body breaking down fat for energy that occurs when carbohydrate intake is low. Here’s how it works: When there isn’t a sufficient level of available glucose — which is what the body uses for its main source of fuel — and glycogen levels are depleted, blood sugar and insulin are lowered and the body looks for an alternative source of fuel: in this case, fat. This process can happen when a person fasting, after prolonged exercise, during starvation, or when eating a low-carb, ketogenic diet. And when the body begins breaking down fats for energy like this, a process known as beta-oxidation, ketones are formed for use as fuel for the body and brain. This is known as ketosis. People following a ketogenic diet specifically reduce their carbohydrate intake for this reason: to create ketones for energy. Many people use the benefits of ketosis — less reliance on carbs and more burning of fat — to possibly help lower blood pressure, reduce cravings, improve cholesterol, increase weight loss, improve energy, and more. TYPES OF KETONE BODIES So, what else about ketones do we need to know? To start, there are technically three types of ketone bodies: Acetoacetate (AcAc) Beta-hydroxybutyric acid (BHB) Acetone Both acetoacetate and beta-hydroxybutyrate are responsible for transporting energy from the liver to other tissues in the body Continue reading >>

Metabolic Effects Of The Very-low-carbohydrate Diets: Misunderstood

Metabolic Effects Of The Very-low-carbohydrate Diets: Misunderstood "villains" Of Human Metabolism

Abstract During very low carbohydrate intake, the regulated and controlled production of ketone bodies causes a harmless physiological state known as dietary ketosis. Ketone bodies flow from the liver to extra-hepatic tissues (e.g., brain) for use as a fuel; this spares glucose metabolism via a mechanism similar to the sparing of glucose by oxidation of fatty acids as an alternative fuel. In comparison with glucose, the ketone bodies are actually a very good respiratory fuel. Indeed, there is no clear requirement for dietary carbohydrates for human adults. Interestingly, the effects of ketone body metabolism suggest that mild ketosis may offer therapeutic potential in a variety of different common and rare disease states. Also, the recent landmark study showed that a very-low-carbohydrate diet resulted in a significant reduction in fat mass and a concomitant increase in lean body mass in normal-weight men. Contrary to popular belief, insulin is not needed for glucose uptake and utilization in man. Finally, both muscle fat and carbohydrate burn in an amino acid flame. Keywords low-carbohydrate dietsketogenic dietsketogenesisketosisdiabetic ketoacidosisketone bodiesgluconeogenesisinsulinglucagoncarbohydrate recommendationsglucose utilizationglucose transportersfatty acids Introduction According to the American Heart Association (AHA) Nutrition Committee, "Some popular high-protein/low-carbohydrate diets limit carbohydrates to 10 to 20 g/d, which is one fifth of the minimum 100 g/day that is necessary to prevent loss of lean muscle tissue [1]." Clearly, this is an incorrect statement since catabolism of lean body mass is reduced by ketone bodies (possibly through suppression of the activity of the branched-chain 2-oxo acid dehydrogenase), which and probably explains the pr Continue reading >>

Dublin Institute Of Technology

Dublin Institute Of Technology

Size: 25 Glucose is used as our primary energy source acids get stored for later use. • Glucose fuels us for about six hours, and once it runs out we rely of glycogen stores to produce energy • Ketone bodies are produced from fatty acids when liver glycogen is entirely depleted, and are used for energy • Once the fats are broken down, your body turns to breaking down protein in muscles, essentially wasting away your muscles. • Breaking down protein and releasing amino acids into the bloodstream will produce more glucose In diabetes, hepatocytes cannot efficiently take up glucose to use as a fuel. Acetyl-CoA accumulates in the hepatocytes and are converted into ketone bodies as the TCA cycle is slowed Increased conc. of acetoacetate and D-β-hydroxybutyrate lower pH= acidosis (coma, death) Acetoacetate & β hydroxybutyrate minimal in blood & minimally produced by hepatocytes. Most acetyl CoA fatty acid or pyruvate oxidation enter the TCA cycle only if fat and carbohydrates degradation are balanced. 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 >>

Ketosis

Ketosis

There is a lot of confusion about the term ketosis among medical professionals as well as laypeople. It is important to understand when and why nutritional ketosis occurs, and why it should not be confused with the metabolic disorder we call ketoacidosis. Ketosis is a metabolic state where the liver produces small organic molecules called ketone bodies. Most cells in the body can use ketone bodies as a source of energy. When there is a limited supply of external energy sources, such as during prolonged fasting or carbohydrate restriction, ketone bodies can provide energy for most organs. In this situation, ketosis can be regarded as a reasonable, adaptive physiologic response that is essential for life, enabling us to survive periods of famine. Nutritional ketosis should not be confused with ketoacidosis, a metabolic condition where the blood becomes acidic as a result of the accumulation of ketone bodies. Ketoacidosis can have serious consequences and may need urgent medical treatment. The most common forms are diabetic ketoacidosis and alcoholic ketoacidosis. What Is Ketosis? The human body can be regarded as a biologic machine. Machines need energy to operate. Some use gasoline, others use electricity, and some use other power resources. Glucose is the primary fuel for most cells and organs in the body. To obtain energy, cells must take up glucose from the blood. Once glucose enters the cells, a series of metabolic reactions break it down into carbon dioxide and water, releasing energy in the process. The body has an ability to store excess glucose in the form of glycogen. In this way, energy can be stored for later use. Glycogen consists of long chains of glucose molecules and is primarily found in the liver and skeletal muscle. Liver glycogen stores are used to mai 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 >>

Beta-oxidation & Ketone Body Metabolism Flashcards Preview

Beta-oxidation & Ketone Body Metabolism Flashcards Preview

- stored in adipocytes - when blood glucose levels are low, hormones (cortisol and epinephrine) activate hormone-sensitive lipase - hormone-sensitive lipase cleaves triglycerides into glycerol and free fatty acids, which are released into the blood - (glycerol is H2O soluble, but fatty acids require albumin to traverse the blood) - to power gluconeogenesis! - gluconeogenesis requires ATP (and since this is occurring in the starved state, we need to get ATP from alternate sources); in addition, acetyl-CoA is needed to turn on pyruvate carboxylase, which begins gluconeogenesis - the acetyl-CoA is then used for ketogenesis - B-oxidation moves high energy electrons from the beta-carbon (3rd carbon) of the fatty acid and uses it in the ETC to make ATP (in the liver this ATP is used to power gluconeogenesis, in other cells, this ATP is used for their own needs) - B-oxidation also creates acetyl-CoA, which is used to create ketone bodies in the liver, and is used to create more ATP via the TCA cycle in other cells for their own needs - occurs in the mitochondrial matrix (so any cell with mitochondria can generate ATP via B-oxidation; again, RBCs lack mitochondria so they can NOT) - 1) fatty acids diffuse from the cytoplasm into the outer mitochondrial membrane, where it is attached to a CoA to form FA-CoA (this requires an enzyme, CoA, and ATP) - 2) FA-CoA then becomes FA-carnitine via carnitine acyltransferase-1 (CAT-1) - 3) FA-carnitine enters the matrix via carnitine transporters in the inner mitochondrial membrane - 4) in the matrix, FA-carnitine is returned to FA-CoA via CAT-2 - defective CAT-1, carnitine transport, or CAT-2, resulting in muscle aches, weakness, myoglobinuria, etc. - (it's myopathic, because muscles are the most affected due to their high energy demand) - Continue reading >>

Understanding Ketosis

Understanding Ketosis

To gain a better understanding of ketosis and the ketogenic diet, it is important to take a look at the physiology behind the diet. If you recall from the article What is a Ketogenic Diet? the goal of a ketogenic diet is to induce ketosis by increasing ketone body production. A key step in understanding the diet is to learn what ketosis is, what are ketones and what do they do. “Normal” Metabolism Learning the basics of the various metabolic processes of the body will better your ability to understand ketosis. Under the normal physiological conditions that are common today, glucose is our body’s primary source of energy. Following ingestion, carbohydrates are broken down into glucose and released into the blood stream. This results in the release of insulin from the pancreas. Insulin not only inhibits fat oxidation but also acts as a key holder for cells by allowing glucose from the blood to be shuttled into cells via glucose transporters (GLUT). The amount of insulin required for this action varies between individuals depending on their insulin sensitivity. Once inside the cell, glucose undergoes glycolysis, a metabolic process that produces pyruvate and energy in the form of adenosine triphosphate (ATP). Once pyruvate is formed as an end product of glycolysis, it is shuttled into the mitochondria, where it is converted to acetyl-CoA by pyruvate dehydrogenase. Acetyl-CoA then enters the TCA cycle to produce additional energy with the aid of the electron transport chain. Since glucose is so rapidly metabolized for energy production and has a limited storage capacity, other energy substrates, such as fat, get stored as triglycerides due to our body’s virtually infinite fat storage capacity. When a sufficient source of carbohydrates is not available, the body adap Continue reading >>

Regulation Of Ketone Body Metabolism And The Role Of Pparα

Regulation Of Ketone Body Metabolism And The Role Of Pparα

1. Introduction Adaptation to limited nutritional resources in the environment requires the development of mechanisms that enable temporal functioning in a state of energy deficiency at both systemic and cellular levels. Different molecular and cellular mechanisms have evolved allowing survival during nutrient insufficiency. Some rely on the decrease of metabolic rates, body temperature, or even shutting down most of the live functions during deep hibernation, aestivation or brumation. Other strategies require development of metabolic flexibility and effective fuel management. Peroxisome Proliferator Activated Receptors (PPARs) are important regulators of cellular responses to variable nutrient supply during both fed and fasted states. Acting as transcription factors, and directly modulated by fatty acids and their derivatives, PPARs induce transcription of the proper set of genes, encoding proteins and enzymes indispensable for lipid, amino acid and carbohydrate metabolism. In this review, we make an attempt to outline the regulation of ketone body synthesis and utilization in normal and transformed cells, as well as summarize the role of PPARα in these processes. 2. Ketogenesis and Ketolysis Metabolic adaptation to prolonged fasting in humans is based both on coordinated responses of vital organs, mainly liver, kidneys and muscles, and on restoring nutritional preferences at the cellular level. In the fed state, cells primarily rely on glucose metabolism, whereas during longer food deprivation blood glucose levels drop because glycogen reserves are only sufficient for less than a day. In such conditions, glucose is spared mainly for neurons, but also for erythrocytes and proliferating cells in bone marrow or those involved in tissue regeneration. The most important c 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 >>

The Catabolism Of Fats And Proteins For Energy

The Catabolism Of Fats And Proteins For Energy

Before we get into anything, what does the word catabolism mean? When we went over catabolic and anabolic reactions, we said that catabolic reactions are the ones that break apart molecules. To remember what catabolic means, think of a CATastrophe where things are falling apart and breaking apart. You could also remember cats that tear apart your furniture. In order to make ATP for energy, the body breaks down mostly carbs, some fats and very small amounts of protein. Carbs are the go-to food, the favorite food that cells use to make ATP but now we’re going to see how our cells use fats and proteins for energy. What we’re going to find is that they are ALL going to be turned into sugars (acetyl) as this picture below shows. First let’s do a quick review of things you already know because it is assumed you learned cell respiration already and how glucose levels are regulated in your blood! Glucose can be stored as glycogen through a process known as glycogenesis. The hormone that promotes this process is insulin. Then when glycogen needs to be broken down, the hormone glucagon, promotes glycogenolysis (Glycogen-o-lysis) to break apart the glycogen and increase the blood sugar level. Glucose breaks down to form phosphoglycerate (PGAL) and then pyruvic acid. What do we call this process of splitting glucose into two pyruvic sugars? That’s glycolysis (glyco=glucose, and -lysis is to break down). When there’s not enough oxygen, pyruvic acid is converted into lactic acid. When oxygen becomes available, lactic acid is converted back to pyruvic acid. Remember that this all occurs in the cytoplasm. The pyruvates are then, aerobically, broken apart in the mitochondria into Acetyl-CoA. The acetyl sugars are put into the Krebs citric acid cycle and they are totally broken Continue reading >>

Metabolism

Metabolism

Reactions and Metabolic Pathways A progression of metabolic reactions from beginning to end is called a pathway Intermediates of reactions Anabolic pathways Catabolic pathways Energy for the cell Energy used in cells come from the chemical bonds found between atoms in carbohydrate, fat, protein, and alcohol Most energy is from the sun and involved in reactions converting carbon dioxide and water into glucose – (photosynthesis) Glucose used in cell respiration to produce ATP used by all reactions in all cells Types of energy: chemical, mechanical, electrical, osmotic Oxidation-Reduction Reactions A substance is oxidized when it loses one or more electrons A substance is reduced when it gains one or more electrons Oxidation-reduction reactions are controlled by enzymes Antioxidants – compounds that donate electrons to oxidized compounds, putting them into a more reduced (stable) state Oxidized compounds tend to be highly reactive Vitamins E and C are antioxidants Remember phytochemicals! Glycolysis, Citric Acid Cycle (also called Krebs Cycle), and Electron Transport Chain (ETC) Glycolysis Occurs in the cytosol of the cell Begin process with glucose 2 ATP used 4 ATP produced = 2 ATP net Water molecule is removed Hydrogen atoms removed from intermediates by NAD molecules 2 pyruvate molecules produced at end of the pathway If no oxygen present in the cell then pyruvates are converted into lactate – this process is called anaerobic respiration Intermediate step: Pyruvate to Acetyl CoA (occurs in the mitochodria) Citric Acid Cycle Occurs in the mitochondria Acetyl CoA added to compound in the cycle Hydrogens are removed by NAD molecules and FAD molecules Carbon dioxide is removed from intermediates GTP produced (a usable energy source like ATP) Electron Transport Chain H Continue reading >>

Scb 204.1738, 1739 Robyn O’kane, Ph.d.

Scb 204.1738, 1739 Robyn O’kane, Ph.d.

Quiz 6 FORM A Spring I 2008 Name_________________________________________________________________ Nutrients and Metabolism Match the following terms with their descriptions: 1. Glycogenolysis A. Occurs when blood glucose levels are low 2. Lipogenesis B. Anaerobic breakdown of glucose 3. Glycogenesis C. Glucose molecules get packaged into glycogen 4. Glycolysis D. Occurs when caloric intake exceeds energy expenditures 5. All of the following are correct descriptions of the vitamin EXCEPT A. A is produced from beta-carotene. B. B vitamins are fat soluble. C. C is an antioxidant. D. D is a fat soluble vitamin. 6. Hepatocytes and skeletal muscle fibers A. can both undergo glycogenolysis. B. are where carbohydrates are stored. C. can both produce lactic acid. D. All of the above are correct. E. A and B are correct only. 7. Beta oxidation A. can result in ketone bodies being produced from acetyl CoA. B. is the process by which glycerol is broken down. C. occurs in the cytosol. D. relies on the chemiosmotic mechanism to produce ATP. 8. The majority of the ATP production from the catabolism of glucose occurs directly via A. glycolysis. B. electron transport chain. C Kreb’s cycle. 9. All of the following occur in the mitochondria EXCEPT A. electron transport chain. B. beta-oxidation. C. Kreb’s cycle. D. glycolysis. 10. Catabolism of amino acids A. creates ammonia. B. breaks peptide bonds. C. forms proteins. D. only occurs in the skeletal muscle cells. 11. Which of the following is correct? A. Essential amino acids are produced within the body via transamination reactions. B. All complete proteins have all 20 amino acids in them. C. Incomplete proteins are missing some essential amino acids. D. Essential fatty acids are produced within the body. 12. Which lipoprotei Continue reading >>

Ketone Body

Ketone Body

ketone body n. Any of three compounds, acetoacetic acid, acetone, and beta-hydroxybutyric acid, that are ketones or derivatives of ketones and are intermediate products of fatty acid metabolism. Ketone bodies accumulate in the blood and urine when fats are being used for energy instead of carbohydrates, as in individuals affected by starvation or uncontrolled diabetes mellitus. Also called acetone body. 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 body n (Biochemistry) biochem any of three compounds (acetoacetic acid, 3-hydroxybutanoic acid, and acetone) produced when fatty acids are broken down in the liver to provide a source of energy. Excess ketone bodies are present in the blood and urine of people unable to use glucose as an energy source, as in diabetes and starvation. Also called: acetone body Collins English Dictionary – Complete and Unabridged, 12th Edition 2014 © HarperCollins Publishers 1991, 1994, 1998, 2000, 2003, 2006, 2007, 2009, 2011, 2014 ke′tone bod′y n. any of several compounds, as acetoacetic acid, acetone, and hydroxybutyric acid, that are intermediate in the metabolism of fatty acids and are produced in excessive amounts under certain abnormal conditions, as in diabetes mellitus. Random House Kernerman Webster's College Dictionary, © 2010 K Dictionaries Ltd. Copyright 2005, 1997, 1991 by Random House, Inc. All rights reserved. Noun 1. ketone body - a ketone that is an intermediate product of the breakdown of fats in the body; any of three compounds (acetoacetic acid, acetone, and/or beta-hydroxybutyric acid) found in excess in blood and urine of persons with meta Continue reading >>

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