How Our Bodies Turn Food Into Energy
All parts of the body (muscles, brain, heart, and liver) need energy to work. This energy comes from the food we eat. Our bodies digest the food we eat by mixing it with fluids (acids and enzymes) in the stomach. When the stomach digests food, the carbohydrate (sugars and starches) in the food breaks down into another type of sugar, called glucose. The stomach and small intestines absorb the glucose and then release it into the bloodstream. Once in the bloodstream, glucose can be used immediately for energy or stored in our bodies, to be used later. However, our bodies need insulin in order to use or store glucose for energy. Without insulin, glucose stays in the bloodstream, keeping blood sugar levels high. Insulin is a hormone made by beta cells in the pancreas. Beta cells are very sensitive to the amount of glucose in the bloodstream. Normally beta cells check the blood's glucose level every few seconds and sense when they need to speed up or slow down the amount of insulin they're making and releasing. When someone eats something high in carbohydrates, like a piece of bread, the glucose level in the blood rises and the beta cells trigger the pancreas to release more insulin into the bloodstream. When insulin is released from the pancreas, it travels through the bloodstream to the body's cells and tells the cell doors to open up to let the glucose in. Once inside, the cells convert glucose into energy to use right then or store it to use later. As glucose moves from the bloodstream into the cells, blood sugar levels start to drop. The beta cells in the pancreas can tell this is happening, so they slow down the amount of insulin they're making. At the same time, the pancreas slows down the amount of insulin that it's releasing into the bloodstream. When this happens, Continue reading >>
How Does The Liver Control Glucose In The Blood?
Your body needs a constant supply of glucose, or sugar, for cells to have energy, so it requires a readily available reservoir to keep blood glucose in balance. One of the liver’s main roles in the body is controlling the amount of glucose circulating in the blood. By storing excess glucose as glycogen and creating new glucose from proteins and fat byproducts, the liver is able to maintain balanced glucose levels in your body at all times. Video of the Day When you eat carbohydrates, the body releases glucose into the bloodstream immediately, triggering the production of insulin. The body cannot be in a state of constant consumption, so when insulin levels are high enough, the body links long chains of glucose together into a compound called glycogen, which is then stored in the liver and the muscles. The liver uses this stored glucose energy as its main reservoir for releasing glucose into the bloodstream when levels drop. Breakdown of Glycogen Blood glucose levels drop when you're not eating, such as during sleep or between meals. This low blood sugar signals the liver to produce glucose and release it back into the bloodstream. The liver favors glycogen as its primary source since it is efficiently broken down into glucose in a process known as glycogenolysis. In this process, the liver breaks the bonds that hold glucose molecules together as glycogen, degrading most but not all of the glycogen molecule. Effects of Insulin Resistance When your body is chronically subjected to high levels of blood sugar and insulin, such as after you've eaten an excessive amount of foods high in sugar, it develops a resistance to the hormone, and the liver cannot respond properly, eventually leading to type-2 diabetes if the resistance is not controlled. According to a study publish Continue reading >>
Regulation Of Glucose Production By The Liver.
Abstract Glucose is an essential nutrient for the human body. It is the major energy source for many cells, which depend on the bloodstream for a steady supply. Blood glucose levels, therefore, are carefully maintained. The liver plays a central role in this process by balancing the uptake and storage of glucose via glycogenesis and the release of glucose via glycogenolysis and gluconeogenesis. The several substrate cycles in the major metabolic pathways of the liver play key roles in the regulation of glucose production. In this review, we focus on the short- and long-term regulation glucose-6-phosphatase and its substrate cycle counter-part, glucokinase. The substrate cycle enzyme glucose-6-phosphatase catalyzes the terminal step in both the gluconeogenic and glycogenolytic pathways and is opposed by the glycolytic enzyme glucokinase. In addition, we include the regulation of GLUT 2, which facilitates the final step in the transport of glucose out of the liver and into the bloodstream. Continue reading >>
How Does The Liver Work?
The liver is one of the largest organs in the body. It has many important metabolic functions. It converts the nutrients in our diets into substances that the body can use, stores these substances, and supplies cells with them when needed. It also takes up toxic substances and converts them into harmless substances or makes sure they are released from the body. The human adult liver weighs about 1.4 kg (3.1 pounds) and is found in the right upper abdomen, below the diaphragm. It takes up most of the space under the ribs and some space in the left upper abdomen, too. Viewed from the outside, a larger right lobe and smaller left lobe can be distinguished. The two lobes are separated by a band of connective tissue that anchors the liver to the abdominal cavity. The gallbladder, where bile is stored, is found in a small hollow on the underside of the liver. Liver tissue is made up of lots of smaller units of liver cells called lobules. Many canals carrying blood and bile run between the liver cells. Blood coming from the digestive organs flows through the portal vein to the liver, carrying nutrients, medication and also toxic substances. Once they reach the liver, these substances are processed, stored, altered, detoxified, and passed back into the blood or released in the bowel to be eliminated. In this way the liver can, for example, remove alcohol from your blood and get rid of by-products from the breakdown of medications. With the help of vitamin K, the liver produces proteins that are important in blood clotting. It is also one of the organs that break down old or damaged blood cells. The liver plays a central role in all metabolic processes in the body. In fat metabolism the liver cells break down fats and produce energy. They also produce about 800 to 1,000 ml of bi Continue reading >>
Quantifying The Contribution Of The Liver To Glucose Homeostasis: A Detailed Kinetic Model Of Human Hepatic Glucose Metabolism
Quantifying the Contribution of the Liver to Glucose Homeostasis: A Detailed Kinetic Model of Human Hepatic Glucose Metabolism Affiliation Institute of Biochemistry, University Medicine Charit Berlin, Berlin, Germany Affiliation Institute of Biochemistry, University Medicine Charit Berlin, Berlin, Germany Affiliation Institute of Biochemistry, University Medicine Charit Berlin, Berlin, Germany Quantifying the Contribution of the Liver to Glucose Homeostasis: A Detailed Kinetic Model of Human Hepatic Glucose Metabolism Despite the crucial role of the liver in glucose homeostasis, a detailed mathematical model of human hepatic glucose metabolism is lacking so far. Here we present a detailed kinetic model of glycolysis, gluconeogenesis and glycogen metabolism in human hepatocytes integrated with the hormonal control of these pathways by insulin, glucagon and epinephrine. Model simulations are in good agreement with experimental data on (i) the quantitative contributions of glycolysis, gluconeogenesis, and glycogen metabolism to hepatic glucose production and hepatic glucose utilization under varying physiological states. (ii) the time courses of postprandial glycogen storage as well as glycogen depletion in overnight fasting and short term fasting (iii) the switch from net hepatic glucose production under hypoglycemia to net hepatic glucose utilization under hyperglycemia essential for glucose homeostasis (iv) hormone perturbations of hepatic glucose metabolism. Response analysis reveals an extra high capacity of the liver to counteract changes of plasma glucose level below 5 mM (hypoglycemia) and above 7.5 mM (hyperglycemia). Our model may serve as an important module of a whole-body model of human glucose metabolism and as a valuable tool for understanding the role of t Continue reading >>
Schematic two-dimensional cross-sectional view of glycogen: A core protein of glycogenin is surrounded by branches of glucose units. The entire globular granule may contain around 30,000 glucose units. A view of the atomic structure of a single branched strand of glucose units in a glycogen molecule. Glycogen (black granules) in spermatozoa of a flatworm; transmission electron microscopy, scale: 0.3 µm Glycogen is a multibranched polysaccharide of glucose that serves as a form of energy storage in humans, animals, fungi, and bacteria. The polysaccharide structure represents the main storage form of glucose in the body. Glycogen functions as one of two forms of long-term energy reserves, with the other form being triglyceride stores in adipose tissue (i.e., body fat). In humans, glycogen is made and stored primarily in the cells of the liver and skeletal muscle. In the liver, glycogen can make up from 5–6% of the organ's fresh weight and the liver of an adult weighing 70 kg can store roughly 100–120 grams of glycogen. In skeletal muscle, Glycogen is found in a low concentration (1–2% of the muscle mass) and the skeletal muscle of an adult weighing 70 kg can store roughly 400 grams of glycogen. The amount of glycogen stored in the body—particularly within the muscles and liver—mostly depends on physical training, basal metabolic rate, and eating habits. Small amounts of glycogen are also found in other tissues and cells, including the kidneys, red blood cells, white blood cells,[medical citation needed] and glial cells in the brain. The uterus also stores glycogen during pregnancy to nourish the embryo. Approximately 4 grams of glucose are present in the blood of humans at all times; in fasted individuals, blood glucos Continue reading >>
How Sugar Messes Up Your Liver And Gives You Diabetes
Modern man is plagued with many diseases that you will not find in some "primitive" populations like modern hunter-gatherers. These include obesity, heart disease, some cancers and last but not least, type II diabetes... which has reached epidemic proportions in the past few decades and now afflicts about 300 million people worldwide. This disease is a common cause of early death, blindness, amputation and a severely decreased quality of life... and it is advancing rapidly, every single year. In the video above, Dr. Robert H. Lustig and Dr. Elissa S. Epel explain how excess sugar can mess up liver metabolism and ultimately lead to diabetes. Dr. Lustig recently took part in a study where they examined the associations between sugar consumption and diabetes in 175 countries (1). They found very clear associations, where each 150 kcal (about one can of soda) per day of sugar increased the prevalence of diabetes by 1.1%. To put this number in perspective, if all of the U.S. added one can of soda to their daily diet, almost 3.5 million more people would become diabetic. In this study, added sugar was the only part of the diet that correlated with diabetes when they adjusted for confounding factors. These types of studies are so-called observational studies, which can not prove that one thing caused another, it can only show that they are correlated. However, there are other lines of evidence linking sugar to the development of type II diabetes and this specifically involves how sugar affects the liver. Sugar is composed of two molecules... glucose and fructose. Glucose can be metabolized by every cell in the body and if we don't get it from the diet, our bodies make it. However, fructose is different. The only organ that can metabolize sugar is the liver, because only the li Continue reading >>
Four Grams Of Glucose
Department of Molecular Physiology and Biophysics and Mouse Metabolic Phenotyping Center, Vanderbilt University School of Medicine, Nashville, Tennessee Department of Molecular Physiology and Biophysics and Mouse Metabolic Phenotyping Center, Vanderbilt University School of Medicine, Nashville, Tennessee Address for reprint requests and other correspondence: D. H. Wasserman, Light Hall Rm. 702, Vanderbilt Univ. School of Medicine, Nashville, TN 37232 (e-mail: [email protected] ) Received 2008 Jul 7; Accepted 2008 Oct 1. Copyright 2009, American Physiological Society This article has been cited by other articles in PMC. Four grams of glucose circulates in the blood of a person weighing 70 kg. This glucose is critical for normal function in many cell types. In accordance with the importance of these 4 g of glucose, a sophisticated control system is in place to maintain blood glucose constant. Our focus has been on the mechanisms by which the flux of glucose from liver to blood and from blood to skeletal muscle is regulated. The body has a remarkable capacity to satisfy the nutritional need for glucose, while still maintaining blood glucose homeostasis. The essential role of glucagon and insulin and the importance of distributed control of glucose fluxes are highlighted in this review. With regard to the latter, studies are presented that show how regulation of muscle glucose uptake is regulated by glucose delivery to muscle, glucose transport into muscle, and glucose phosphorylation within muscle. Keywords: insulin, mice, rat, dog, glycogen, epinephrine, hexokinase, glucose transport, glucose delivery four grams of glucose circulates in the blood of a person weighing 70 kg. This is the amount needed to fill a teaspoon. Although these 4 g constitute an infini Continue reading >>
The Liver & Blood Sugar
During a meal, your liver stores sugar for later. When you’re not eating, the liver supplies sugar by turning glycogen into glucose in a process called glycogenolysis. The liver both stores and produces sugar… The liver acts as the body’s glucose (or fuel) reservoir, and helps to keep your circulating blood sugar levels and other body fuels steady and constant. The liver both stores and manufactures glucose depending upon the body’s need. The need to store or release glucose is primarily signaled by the hormones insulin and glucagon. During a meal, your liver will store sugar, or glucose, as glycogen for a later time when your body needs it. The high levels of insulin and suppressed levels of glucagon during a meal promote the storage of glucose as glycogen. The liver makes sugar when you need it…. When you’re not eating – especially overnight or between meals, the body has to make its own sugar. The liver supplies sugar or glucose by turning glycogen into glucose in a process called glycogenolysis. The liver also can manufacture necessary sugar or glucose by harvesting amino acids, waste products and fat byproducts. This process is called gluconeogenesis. When your body’s glycogen storage is running low, the body starts to conserve the sugar supplies for the organs that always require sugar. These include: the brain, red blood cells and parts of the kidney. To supplement the limited sugar supply, the liver makes alternative fuels called ketones from fats. This process is called ketogenesis. The hormone signal for ketogenesis to begin is a low level of insulin. Ketones are burned as fuel by muscle and other body organs. And the sugar is saved for the organs that need it. The terms “gluconeogenesis, glycogenolysis and ketogenesis” may seem like compli Continue reading >>
How Is Excess Glucose Stored?
The human body has an efficient and complex system of storing and preserving energy. Glucose is a type of sugar that the body uses for energy. Glucose is the product of breaking down carbohydrates into their simplest form. Carbohydrates should make up approximately 45 to 65 percent of your daily caloric intake, according to MayoClinic.com. Video of the Day Glucose is a simple sugar found in carbohydrates. When more complex carbohydrates such as polysaccharides and disaccharides are broken down in the stomach, they break down into the monosaccharide glucose. Carbohydrates serve as the primary energy source for working muscles, help brain and nervous system functioning and help the body use fat more efficiently. Function of Glucose Once carbohydrates are absorbed from food, they are carried to the liver for processing. In the liver, fructose and galactose, the other forms of sugar, are converted into glucose. Some glucose gets sent to the bloodstream while the rest is stored for later energy use. Once glucose is inside the liver, glucose is phosphorylated into glucose-6-phosphate, or G6P. G6P is further metabolized into triglycerides, fatty acids, glycogen or energy. Glycogen is the form in which the body stores glucose. The liver can only store about 100 g of glucose in the form of glycogen. The muscles also store glycogen. Muscles can store approximately 500 g of glycogen. Because of the limited storage areas, any carbohydrates that are consumed beyond the storage capacity are converted to and stored as fat. There is practically no limit on how many calories the body can store as fat. The glucose stored in the liver serves as a buffer for blood glucose levels. Therefore, if the blood glucose levels start to get low because you have not consumed food for a period of time Continue reading >>
How Insulin And Glucagon Work
Insulin and glucagon are hormones that help regulate the levels of blood glucose, or sugar, in your body. Glucose, which comes from the food you eat, moves through your bloodstream to help fuel your body. Insulin and glucagon work together to balance your blood sugar levels, keeping them in the narrow range that your body requires. These hormones are like the yin and yang of blood glucose maintenance. Read on to learn more about how they function and what can happen when they don’t work well. Insulin and glucagon work in what’s called a negative feedback loop. During this process, one event triggers another, which triggers another, and so on, to keep your blood sugar levels balanced. How insulin works During digestion, foods that contain carbohydrates are converted into glucose. Most of this glucose is sent into your bloodstream, causing a rise in blood glucose levels. This increase in blood glucose signals your pancreas to produce insulin. The insulin tells cells throughout your body to take in glucose from your bloodstream. As the glucose moves into your cells, your blood glucose levels go down. Some cells use the glucose as energy. Other cells, such as in your liver and muscles, store any excess glucose as a substance called glycogen. Your body uses glycogen for fuel between meals. Read more: Simple vs. complex carbs » How glucagon works Glucagon works to counterbalance the actions of insulin. About four to six hours after you eat, the glucose levels in your blood decrease, triggering your pancreas to produce glucagon. This hormone signals your liver and muscle cells to change the stored glycogen back into glucose. These cells then release the glucose into your bloodstream so your other cells can use it for energy. This whole feedback loop with insulin and gluca Continue reading >>
How Is Glucose Stored In The Liver?
The liver is large and in charge. The dark reddish-brown organ sits in the upper right abdomen and, at about 3 pounds, is the largest one inside the body (the skin is the largest organ overall). The liver manages a dizzying array of tasks, including digesting fats, making and storing glucose, and serving as the body's detox center. Glucose Warehouse The liver is an insulin-guided organ: Its behavior changes depending on the level of the hormone insulin in the body and how sensitive the liver is to that insulin. After eating, blood glucose levels rise, which in people without diabetes triggers the pancreas to release insulin into the blood. Insulin is the signal for the body to absorb glucose from the blood. Most cells just use the glucose to supply them with energy. But the liver has a special job when it comes to glucose. When levels of glucose (and consequently insulin) are high in the blood, the liver responds to the insulin by absorbing glucose. It packages the sugar into bundles called glycogen. These glucose granules fill up liver cells, so the liver is like a warehouse for excess glucose. When glucose levels drop, insulin production falls, too. The shortage of insulin in the blood is the signal that the liver needs to liquidate its assets, sending its glucose stores back into the blood to keep the body well fed between meals and overnight. The liver doles out stored glucose and has the singular ability to make glucose from scratch. This is a critical function that keeps people alive when food is scarce. In people with diabetes, however, the liver doesn't process and produce glucose normally, adding to the challenge of blood glucose control. The liver can't directly detect blood glucose levels; it knows only what insulin tells it. So, if there is a shortage of ins Continue reading >>
The Liver And Blood Glucose Levels
Tweet Glucose is the key source of energy for the human body. Supply of this vital nutrient is carried through the bloodstream to many of the body’s cells. The liver produces, stores and releases glucose depending on the body’s need for glucose, a monosaccharide. This is primarily indicated by the hormones insulin - the main regulator of sugar in the blood - and glucagon. In fact, the liver acts as the body’s glucose reservoir and helps to keep your circulating blood sugar levels and other body fuels steady and constant. How the liver regulates blood glucose During absorption and digestion, the carbohydrates in the food you eat are reduced to their simplest form, glucose. Excess glucose is then removed from the blood, with the majority of it being converted into glycogen, the storage form of glucose, by the liver’s hepatic cells via a process called glycogenesis. Glycogenolysis When blood glucose concentration declines, the liver initiates glycogenolysis. The hepatic cells reconvert their glycogen stores into glucose, and continually release them into the blood until levels approach normal range. However, when blood glucose levels fall during a long fast, the body’s glycogen stores dwindle and additional sources of blood sugar are required. To help make up this shortfall, the liver, along with the kidneys, uses amino acids, lactic acid and glycerol to produce glucose. This process is known as gluconeogenesis. The liver may also convert other sugars such as sucrose, fructose, and galactose into glucose if your body’s glucose needs not being met by your diet. Ketones Ketones are alternative fuels that are produced by the liver from fats when sugar is in short supply. When your body’s glycogen storage runs low, the body starts conserving the sugar supplies fo Continue reading >>
What Is Glucose?
Glucose comes from the Greek word for "sweet." It's a type of sugar you get from foods you eat, and your body uses it for energy. As it travels through your bloodstream to your cells, it's called blood glucose or blood sugar. Insulin is a hormone that moves glucose from your blood into the cells for energy and storage. People with diabetes have higher-than-normal levels in their blood. Either they don't have enough insulin to move it through or their cells don't respond to insulin as well as they should. High blood glucose for a long period of time can damage your kidneys, eyes, and other organs. How Your Body Makes Glucose It mainly comes from foods rich in carbohydrates, like bread, potatoes, and fruit. As you eat, food travels down your esophagus to your stomach. There, acids and enzymes break it down into tiny pieces. During that process, glucose is released. It goes into your intestines where it's absorbed. From there, it passes into your bloodstream. Once in the blood, insulin helps glucose get to your cells. Energy and Storage Your body is designed to keep the level of glucose in your blood constant. Beta cells in your pancreas monitor your blood sugar level every few seconds. When your blood glucose rises after you eat, the beta cells release insulin into your bloodstream. Insulin acts like a key, unlocking muscle, fat, and liver cells so glucose can get inside them. Most of the cells in your body use glucose along with amino acids (the building blocks of protein) and fats for energy. But it's the main source of fuel for your brain. Nerve cells and chemical messengers there need it to help them process information. Without it, your brain wouldn't be able to work well. After your body has used the energy it needs, the leftover glucose is stored in little bundles Continue reading >>
Why Diabetics Over Produce Sugar In The Liver
Why Diabetics Over Produce Sugar in the Liver Type 2 diabetics often suffer from an over-production of sugar within the liver, a response to falling blood glucose levels. This potentially dangerous mechanism was poorly understood until recently, when researchers uncovered the role that a certain master regulator plays in sugar production within the liver. While an inability to regulate blood glucose levels, due to resistance to insulin produced by pancreatic beta cells, is the primary mechanism that leads to and enhances type 2 diabetes, the liver plays a large role as well. Beta-cells, in a healthy body, produce insulin, which helps regulate blood glucose levels, but the liver itself directly responds to low blood glucose levels by producing more sugar. In type 2 diabetics, who suffer from insulin resistance (and therefore dysfunctional regulation of blood glucose with insulin), the liver often has a tendency to produce sugar when not really needed, which can cause potential harm. In other words, the liver continues to produce sugar past what it should, because insulin is not regulating the sugar already being produced, in type 2 diabetics. To illustrate the role that the liver plays in type 2 diabetics, researcher Dr. Jenny Gunton explains that over-production of sugar within the liver is why many diabetics wake up with higher blood glucose levels than they had when going to sleep: It upsets people when their blood sugar behaves as if theyre getting up in the night and having a really big snack. I have to tell them its just one of those unfair things about having diabetes. Researchers looked at ARNT, a so-called master regulator, which is known to play a large role in insulin production and blood glucose control. Past research by the same research team demonstrated t Continue reading >>