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: ude.t[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 >>
How Sugar, Not Fat, Raises Your Cholesterol
Excess carbohydrates and sugar lead to cholesterol and weight gain, explains Dr. Doni Wilson, which is why balancing blood sugar levels every day is so important. When you go to the doctor and get a cholesterol reading, you may be cautioned against eating high-fat foods. But very little fat from foods becomes cholesterol in your blood. What produces cholesterol is rather the excessive consumption of carbs at any one time. The cholesterol and triglycerides in your bloodstream come not from consuming excess fat, but rather, from consuming excess glucose. I’m not just talking about excess glucose over the course of a week or even a day. I’m talking about what happens when you consume excess glucose in one sitting. Let’s take a closer look at exactly happens when your body gets too many carbs at one particular meal. First, you digest the carb-containing food, breaking it down into the individual glucose molecules that are small enough to cross the cells of your intestinal walls and enter your bloodstream. Because you have eaten too many carbs, you have far too much glucose stuck in your blood. You don’t have enough insulin to move all that glucose into your cells. So what happens to that excess glucose? Some of it is stored in your liver as a substance known as glycogen, to be released when you don’t eat. Harking back to our hunter-gatherer days, our bodies created a backup system to ensure that even if we can’t get any food for a couple of days, we won’t starve to death. The liver can only hold so much glycogen, however. So what about the glucose that doesn’t fit? Your body has three choices: convert the glucose into body fat, which translates into weight gain, most likely around your middle; convert the glucose into lipids (fats), which remain in your bloo Continue reading >>
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Nih Study Shows How Insulin Stimulates Fat Cells To Take In Glucose
Findings could aid in understanding diabetes, related conditions. Using high-resolution microscopy, researchers at the National Institutes of Health have shown how insulin prompts fat cells to take in glucose in a rat model. The findings were reported in the Sept. 8 issue of the journal Cell Metabolism. By studying the surface of healthy, live fat cells in rats, researchers were able to understand the process by which cells take in glucose. Next, they plan to observe the fat cells of people with varying degrees of insulin sensitivity, including insulin resistance — considered a precursor to type 2 diabetes (These observations may help identify the interval when someone becomes at risk for developing diabetes. "What we're doing here is actually trying to understand how glucose transporter proteins called GLUT4 work in normal, insulin-sensitive cells," said Karin G. Stenkula, Ph.D., a researcher at the National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK) and a lead author of the paper. "With an understanding of how these transporters in fat cells respond to insulin, we could detect the differences between an insulin-sensitive cell and an insulin-resistant cell, to learn how the response becomes impaired. We hope to identify when a person becomes pre-diabetic, before they go on to develop diabetes." Glucose, a simple sugar, provides energy for cell functions. After food is digested, glucose is released into the bloodstream. In response, the pancreas secretes insulin, which directs the muscle and fat cells to take in glucose. Cells obtain energy from glucose or convert it to fat for long-term storage. Like a key fits into a lock, insulin binds to receptors on the cell's surface, causing GLUT4 molecules to come to the cell's surface. As their name impli Continue reading >>
What Happens To Unburned Carbohydrates?
Your body uses mostly carbohydrates as well as fats for energy. Because the body doesn’t store carbs efficiently, they’re used first. Carbohydrates turn into glucose, which your body burns immediately or converts to glycogen to be stored in the muscles and liver for between meals. If you eat more calories from carbs or other sources than your body can use, the cells store the excess as fat. Of the three major nutrients -- carbohydrates, fat and protein -- the body burns carbs first for energy because they can’t be stored in great quantities. The carbohydrates in food get broken down into glucose, which moves into the small intestine, then the liver and into the blood. As blood sugar rises, the pancreas produces insulin, which signals the cells to take up sugar. Whatever glucose the cells don’t need immediately for energy is stored in the liver and muscles as glycogen. When the blood sugar levels fall -- such as between meals -- the liver releases glycogen. This cycle keeps your body supplied with a steady source of fuel. Insulin Resistance If you have insulin resistance or diabetes, the sugar-insulin cycle doesn’t work properly, leading to too much sugar and insulin circulating in the blood until eventually your body doesn’t produce enough insulin or is resistant to its effects. This is why people with diabetes or prediabetes often track the carbs they eat; eating too many carbohydrates, especially sugars and refined starches, can cause blood sugar and/or insulin to spike to potentially dangerous levels in people with diabetes. How Carbs Turn Into Fat When you eat too many calories, especially in the form of sugars and quickly burned starches, your body may reach its storage capacity for glycogen. The liver converts the stored sugars into triglycerides, or f 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 >>
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How Insulin Really Works: It Causes Fat Storage…but Doesn’t Make You Fat
Many people believe that insulin is to blame for the obesity epidemic. When you understand how it actually works, you’ll know why this is a lie. Insulin has been taking quite a beating these days. If we’re to listen to some “experts,” it’s an evil hormone whose sole goal is making us fat, type 2 diabetics. Furthermore, we’re told that carbohydrates also are in on the conspiracy. By eating carbs, we open the insulin floodgates and wreak havoc in our bodies. How true are these claims, though? Does it really make sense that our bodies would come with an insidious mechanism to punish carbohydrate intake? Let’s find out. What is Insulin, Anyway? Insulin is a hormone, which means it’s a substance the body produces to affect the functions of organs or tissues, and it’s made and released into the blood by the pancreas. Insulin’s job is a very important one: when you eat food, it’s broken down into basic nutrients (protein breaks down into amino acids; dietary fats into fatty acids; and carbohydrates into glucose), which make their way into the bloodstream. These nutrients must then be moved from the blood into muscle and fat cells for use or storage, and that’s where insulin comes into play: it helps shuttle the nutrients into cells by “telling” the cells to open up and absorb them. So, whenever you eat food, your pancreas releases insulin into the blood. As the nutrients are slowly absorbed into cells, insulin levels drop, until finally all the nutrients are absorbed, and insulin levels then remain steady at a low, “baseline” level. This cycle occurs every time you eat food: amino acids, fatty acids, and/or glucose find their way into your blood, and they’re joined by additional insulin, which ushers them into cells. Once the job is done, insu 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 >>
Carbohydrates, Proteins, Fats, And Blood Sugar
The body uses three main nutrients to function-carbohydrate, protein, and fat. These nutrients are digested into simpler compounds. Carbohydrates are used for energy (glucose). Fats are used for energy after they are broken into fatty acids. Protein can also be used for energy, but the first job is to help with making hormones, muscle, and other proteins. Nutrients needed by the body and what they are used for Type of nutrient Where it is found How it is used Carbohydrate (starches and sugars) Breads Grains Fruits Vegetables Milk and yogurt Foods with sugar Broken down into glucose, used to supply energy to cells. Extra is stored in the liver. Protein Meat Seafood Legumes Nuts and seeds Eggs Milk products Vegetables Broken down into amino acids, used to build muscle and to make other proteins that are essential for the body to function. ADVERTISINGinRead invented by Teads Fat Oils Butter Egg yolks Animal products Broken down into fatty acids to make cell linings and hormones. Extra is stored in fat cells. After a meal, the blood sugar (glucose) level rises as carbohydrate is digested. This signals the beta cells of the pancreas to release insulin into the bloodstream. Insulin helps glucose enter the body's cells to be used for energy. If all the glucose is not needed for energy, some of it is stored in fat cells and in the liver as glycogen. As sugar moves from the blood to the cells, the blood glucose level returns to a normal between-meal range. Several hormones and processes help regulate the blood sugar level and keep it within a certain range (70 mg/dL to 120 mg/dL). When the blood sugar level falls below that range, which may happen between meals, the body has at least three ways of reacting: Cells in the pancreas can release glucagon, a hormone that signals the b Continue reading >>
Why Eating Too Many Carbs Makes You Fat
Carbs and carbs alone, not fat, increase body weight. It doesn't matter whether the carbs are from sugar, bread, fruit, or vegetables: They’re all rapidly digested and quickly converted to blood glucose. A short time after a carb-rich meal, the glucose in your bloodstream rises rapidly, and your pancreas produces a large amount of insulin to take the excess glucose out. Just as eating fat doesn’t raise blood glucose, it doesn't raise insulin levels either. This is important because insulin is the hormone responsible for body fat storage. Because fats do not elicit an insulin response, they cannot be stored as body fat. Insulin takes glucose out of the bloodstream. It is converted first into a starch called glycogen, which is stored in the liver and in muscles. But the body can store only a limited amount of glycogen, so the excess glucose is stored as body fat. This is the process of putting on weight. When your blood glucose level returns to normal, after about 90 minutes, the insulin level in your bloodstream is still near maximum. As a result, the insulin continues to stack glucose away in the form of fat. Ultimately, the level of glucose in your blood falls below normal, and you feel hungry again. So you have a snack of more carbohydrates, and the whole process starts over again. You're getting fatter, but feeling hungry at the same time. Ultimately, insulin resistance caused by continually high insulin levels in your bloodstream impairs your ability to switch on a satiety center in the brain. You enter a vicious cycle of continuous weight gain combined with hunger. Under such circumstances, it is almost impossible not to overeat. Taking Off Weight: Only Cutting Carbs Can Do It So you've put the weight on–now you need to take it off again. Here again, “healt Continue reading >>
How Fat Cells Work
In the last section, we learned how fat in the body is broken down and rebuilt into chylomicrons, which enter the bloodstream by way of the lymphatic system. Chylomicrons do not last long in the bloodstream -- only about eight minutes -- because enzymes called lipoprotein lipases break the fats into fatty acids. Lipoprotein lipases are found in the walls of blood vessels in fat tissue, muscle tissue and heart muscle. Insulin When you eat a candy bar or a meal, the presence of glucose, amino acids or fatty acids in the intestine stimulates the pancreas to secrete a hormone called insulin. Insulin acts on many cells in your body, especially those in the liver, muscle and fat tissue. Insulin tells the cells to do the following: The activity of lipoprotein lipases depends upon the levels of insulin in the body. If insulin is high, then the lipases are highly active; if insulin is low, the lipases are inactive. The fatty acids are then absorbed from the blood into fat cells, muscle cells and liver cells. In these cells, under stimulation by insulin, fatty acids are made into fat molecules and stored as fat droplets. It is also possible for fat cells to take up glucose and amino acids, which have been absorbed into the bloodstream after a meal, and convert those into fat molecules. The conversion of carbohydrates or protein into fat is 10 times less efficient than simply storing fat in a fat cell, but the body can do it. If you have 100 extra calories in fat (about 11 grams) floating in your bloodstream, fat cells can store it using only 2.5 calories of energy. On the other hand, if you have 100 extra calories in glucose (about 25 grams) floating in your bloodstream, it takes 23 calories of energy to convert the glucose into fat and then store it. Given a choice, a fat cell w Continue reading >>
How Are Carbohydrates Converted Into Fat Deposits?
How are carbohydrates converted into fat deposits? There are two ways that carbohydrates and body fat interact. One is directly by turning into body fat, and the other is via insulin. Turning into body fat is like adding fat into the fat cells, whereas carbohydrates spiking insulin does not add anything to fat cells per se, but hinders the release. The former is like a + equation, where the latter is a double negative which results in something that seems positive. There is a process called de novo lipogenesis (literally: Creation of fat from non-fat sources) that can occur in the body. This process turns glucose into lipids, which are then stored as body fat. This process is normally quite inefficient in the body  , which suggests that carbohydrates cannot be stored as fat to a high degree. The process can be upregulated (enhanced) if dietary fat comprised almost none of the diet (lesser than 10%, as a rough estimate), if carbohydrate intake is excessively high for a period of a few days, or if one follows an obesogenic diet (diet that is likely to make you fat) for a prolonged period of time.    Carbohydrates spike insulin , which is a hormone that mediates glucose metabolism. Insulin is not good or bad, insulin is insulin. It can be thought of as a lever that switches the body from fat burning mode into carbohydrate burning mode. This allows carbohydrates (and glycogen) to be burnt at a greater rate, but directly reduces the ability of fat to be lost. Overall metabolic rate (calories burnt over the course of a day) does not change significantly, just where the calories come from. When insulin is spiked in presence of ingested dietary fat, the dietary fat can go into body fat stores and not be released since glucose from glycogen is being used in place of 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 >>
Glycogen And Diabetes - Role, Storage, Release & Exercise
Glycogen is a stored form of glucose. It is a large multi-branched polymer of glucose which is accumulated in response to insulin and broken down into glucose in response to glucagon . Glycogen is mainly stored in the liver and the muscles and provides the body with a readily available source of energy if blood glucose levels decrease. Energy can be stored by the body in different forms. One form of stored energy is fat and glycogen is another. Fatty acids are more energy rich but glucose is the preferred energy source for the brain and glucose also can provide energy for cells in the absence of oxygen, for instance during anaerobic exercise. Glycogen is therefore useful for providing a readily available source of glucose for the body. In a healthy body, the pancreas will respond to higher levels of blood glucose , such as in response to eating, by releasing insulin which will lower blood glucose levels by prompting the liver and muscles to take up glucose from the blood and store it as glycogen. People with diabetes either do not make enough of their own insulin and/or their insulin does not work effectively enough. As a result, the pancreas may not be able to respond effectively enough to rises in blood glucose. In these situations, when the body feels extra glucose is needed in the blood, the pancreas will release the hormone glucagon which triggers the conversion of glycogen into glucose for release into the bloodstream. Glycogen plays an important role in keeping our muscles fuelled for exercise. When we exercise, our muscles will take advantage of their stored glycogen. Glucose in our blood and glycogen stored in the liver can also be used to keep our muscles fuelled. Once we complete our exercise session, our muscles will replenish their glycogen stores. The tim Continue reading >>
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 Sugar Makes You Fat
Look at how many grams of sugar are in what you’re eating (on the nutritional label). Now divide that number by 4. That’s how many teaspoons of pure sugar you’re consuming. Kinda scary, huh? Sugar makes you fat and fatfree food isn’t really free of fat. I’ve said it before in multiple articles, but occasionally, I’ve had someone lean over my desk and say “How in the heck does sugar make you fat if there’s no fat in it?”. This article will answer that puzzler, and provide you with some helpful suggestions to achieve not only weight loss success, but improved body health. First, let’s make some qualifications. Sugar isn’t inherently evil. Your body uses sugar to survive, and burns sugar to provide you with the energy necessary for life. Many truly healthy foods are actually broken down to sugar in the body – through the conversion of long and complex sugars called polysaccharides into short and simple sugars called monosaccharides, such as glucose. In additions to the breakdown products of fat and protein, glucose is a great energy source for your body. However, there are two ways that sugar can sabotage your body and cause fat storage. Excess glucose is the first problem, and it involves a very simple concept. Anytime you have filled your body with more fuel than it actually needs (and this is very easy to do when eating foods with high sugar content), your liver’s sugar storage capacity is exceeded. When the liver is maximally full, the excess sugar is converted by the liver into fatty acids (that’s right – fat!) and returned to the bloodstream, where is taken throughout your body and stored (that’s right – as fat!) wherever you tend to store adipose fat cells, including, but not limited to, the popular regions of the stomach, hips, but Continue reading >>