French scientist Claude Bernard discovered glycogen - a polysaccharide. Experiments undertaken by him revealed that the human liver enclosed a substance that has the aptitude to lessen sugar in the liver by means of an action called 'ferment'. Claude Bernard was successful in isolating a substance, which he named 'la matière glycogène' by 1857. When translated into English, this French term means a 'substance that forms sugar'. Shortly after Claude Bernard discovered presence of glycogen inside the liver, another scientist named A. Sanson discovered that the tissues of our muscles also enclose glycogen.
Glucose is mainly stored in the form of glycogen in the animal cells. In the case of humans, nearly all glycogen is present inside the liver, comprising about 10 per cent of the liver, while our muscles enclose a comparatively small quantity of this polysaccharide (only about 1 per cent of the muscle composition). Besides the liver and the muscles, a little quantity of glycogen is also present in particular glial cells inside the brain.
Occasionally referred to as 'animal starch' owing to its similarity to the starch present in plants, glycogen is amassed in the liver as well as muscle cells. When required, glycogen may be converted into glucose. A hormone called glucagon regulates the conversion of glycogen to glucose in the liver. In specific situations, for instance, in between meals, the glycogen stored in the livers forms a vital supply of blood glucose. Glycogen stored in the muscles only appears to be used locally. As aforementioned, glycogen is the main mechanism for storing glucose (may also be called energy) in our body. This polysaccharide is generally stored as granules inside the cytosol - the water-soluble components of the cytoplasm of a cell, where glycolysis or conversion of glycogen to glucose occurs. These granules enclose glycogen as well as the enzymes required to convert it into glucose.
Precisely speaking, glycogen is a storage device for our body, because it amasses large quantities of glucose when it is not required for additional energy. Glycogen has been classified as a polysaccharide. This is despite the fact that very much akin to amylopectin, glycogen also encloses other branched chains and possesses an elevated molecular weight. While glycogen is stored in the liver as well as the muscles, most of it is amassed in the liver and is available readily when we require additional energy and it is essential to maintain the blood sugar levels. On the other hand, glycogen stored in the muscles is mainly used locally in the form of energy for the muscles.
Among all the body parts, our brain consumes the maximum amount (about 75 per cent) of glucose daily through aerobic conduits. Most of the left over glucose is used by erythrocytes (red blood cells), the heart muscles and the skeletal muscles. Our body received glucose directly from ingested foods or the amino acids as well as lactate through a process called gluconeogenesis. The glucose that is acquired by the body from these two major sources is stored as glycogen (a polymeric form) or stays soluble in the fluids present in the body.
Following the disintegration of glycogen inside our body, it is converted into glucose - a vital energy source for all animals. Glucose has a vital function in all animals - something akin to the role of starch in plants. From the time scientists have identified glycogen to have a vital role in the body's energy storage mechanism; numerous studies have been undertaken to ascertain the attributes of this molecule as well as its function in our body.
Animals obtain glycogen molecules from carbohydrates and, during the digestive process, it is produced inside the liver, the muscles as well as the alimentary canal. The level of glycogen that is amassed in the tissues of the liver and in the muscles reaches peak soon after having a meal. In the case of humans, the body is able to store roughly 2,000 kilocalories of glycogen at any point of time. When people consume any food, the intensity of glycogen is restored. Meanwhile, the body continues to work with the objective to maintain a stable amount of glycogen all the time so there is sufficient energy supply when required.
Compared to that of fatty acids, storage of glycogen molecule is not as efficient. This may actually make some people question as to why our body does not stock up the entire energy in this form. Notwithstanding the problematic efficiency, there are numerous reasons why animals store energy in the form of glycogen. The main reason for this is that our brain requires glucose and, hence, it needs energy to be reserved to fulfill its requirements all the time. Secondly, glycogen molecule is utilized to control the blood glucose levels between meals.
Generally, sportspersons, especially athletics, experience exhaustion of their energy reserves when they exert themselves too much. This especially happens when they take endurance activities, wherein the body gradually utilizes nearly all its energy reserved during events, such as a marathon race. The energy reserves touch this point, often called 'hitting the wall', owing to the strain caused by the event on the body. Usually, the condition as well as the size of an athlete determines when the individual will precisely hit the wall. In such cases, athletes try to put off hitting the wall by loading themselves with carbohydrates prior to the event. In addition, they also consume enough food immediately after the event is over with a view to restore their energy reserves.
A number of people endure conditions called glycogen storage disease. These conditions are basically hereditary in nature and are attributable to disorders related to the genes that control the process of creating as well as storing glycogen. Such people may generally find it difficult to convert the glycogen molecule into glucose. It has been found that people suffering from glycogen storage disease may endure various health disorders, conditional on the variety of disease they are suffering from and also how soon the disease is diagnosed.
Diabetes is the most common ailment wherein metabolism of glycogen turns out to be anomalous. In fact, the storage of glycogen in the liver may be increased or exhausted abnormally owing to anomalous amounts of insulin. When the normal metabolism of glucose in the liver is restored, it also normalizes the metabolism of glycogen.
Excessive insulin results in hypoglycemia, wherein the content of glycogen in the liver is elevated. Administration of too much insulin puts off glycogenolysis that is essential for maintaining the standard level of glucose in the bloodstream. Commonly, glucagon is used to treat this kind of hypoglycemia.
Even the dearth of enzymes essential for synthesizing or breaking down glycogen is also responsible for a variety of inherent disorders related to glycogen metabolism. Together, these disorders are called glycogen storage diseases. At times, glycogen storage diseases or GSDs are also called glycogenoses since they are also a result of difficulties in metabolizing glycogen.
It is important to note that the entire glycogen storage diseases are regarded to be metabolic disorders that have been inherited. In effect, a metabolic disorder is a condition that interferes with metabolism. Precisely speaking, metabolism is a process that involves the breaking down or synthesis of ingested foods and transforming them into energy. Hence, any individual who is suffering from any metabolic disorder finds it difficult to synthesize specific foods and generating energy for vital activities. Most often, metabolic diseases are a result of a dearth or absence of an enzyme (protein). The body produces and secretes several enzymes which work akin to a machine on any assembly line. When any of these enzymes fail to function as they should, the process of disintegrating particular foods may become very slow or even completely shut down.
In all diseases related to glycogen storage, using as well as storing glycogen is the fundamental problem. In effect, glycogen is the form in which glucose or sugar is stored by the body. Analyzing metabolism briefly, our body derives its primary energy from a simple sugar form called glucose. Soon after we eat anything, the level of glucose in the bloodstream goes up and, hence, the surplus glucose is stored by our body as glycogen. At times, our body is under strain and requires additional energy. In such circumstances, specific enzymes transform the stored glycogen into glucose. This glycogen is drawn from the liver as well as the muscles, where it is normally stored. Basically, glycogen is a compound substance (sugar) composed of separate types of glucoses that are related to one another in the form of an elongated chain; some of these glucoses may even branch off to form separate chains.
Any individual suffering from any glycogen storage disease (GSD) is also having a deficit or total absence of any one enzyme whose function is to synthesize glycogen in our body. Such a condition is referred to as an enzyme deficiency, which is responsible for anomalous (excessive or very poor) stock of glycogen in the tissues, or wrongly or unusually formed glycogen (having an atypical shape). Subject to the kind of glycogen storage deficiency one is suffering from, the enzyme deficit may possibly be significant in all body parts, or restricted only to specific body parts - for instance the muscles or the liver. Usually, the different types of glycogen storage diseases (GSD) are depicted depending on the specific body part that is having problems owing to deficiency of enzymes that break down glycogen in our body. Some of the categories are usually described as - the muscles only, the liver only, or together the muscles and the liver. The blood cells - red blood cells (erythrocytes), white blood cells (leucocytes), the platelets, the kidneys, heart and other systems are some of the additional body system that may also be affected by GSD.
Every form of glycogen storage disease affects the body in two ways - either they make the body incapable of producing sufficient amounts of glucose, or they may make the body unable to utilize glucose as an energy form. The type of GSD one is suffering from is determined by diagnosing the symptoms he/ she may have developed. Usually, the physician will examine the patient physically and also ask him/ her to undertake specific blood and urine tests. Sometimes, it may also be essential to get a liver and/ or muscle biopsy done with a view to ascertain the amount of enzyme being secreted in that particular body part.
All forms of glycogen storage disease or GSD are essentially problems related to the genes and, thus, inherited by the sufferers. In other words, GSDs are a result of partial change in a person's genetic information, which is stored up in the genes. The genes work in the form of an instruction guidebook for the body and initiate our bodies on how it should grow as well as function. In addition, genes also decide on our physical characteristics, for instance, the color of the hair and eyes. In all, each cell of the human body roughly contains 30,000 genes. We actually inherit two groups of genes from our parents - one group from our mother and the other group from the father. This is the reason why we have some resemblance to both our parents. However, our parents do not have any control whatsoever on the particular genes that they transfer to us. In fact, the genes that we all receive from our parent purely occur by chance.
Whenever any kind of modification occurs in relation to the genetic information enclosed by the genes, our body is not able to decode the instructions send by them. Hence, in such instances, it is possible that our body will function differently from what it should do. This may be compared to a situation where a page may be missing from an instruction handbook meant for assembling an appliance. In the absence of that particular page, we are not able to put the appliance together appropriately and, therefore, the appliance will fail to work. It has been found that nearly all types of glycogen storage diseases (GSD) take place when any child receives any wrong genetic instruction/ information from his/ her parents - mother as well as the father. On the other hand, a number of types of glycogen storage diseases are a fall-out of a genetic transformation that the mother passes on to her son (for instance, X-linked or sex inheritance).
