Sugar metabolism is the synonymous term for carbohydrate metabolism. It includes all the processes of absorption, conversion, synthesis and utilization of simple and multiple sugars in the organism. A common disorder of carbohydrate metabolism is known as diabetes mellitus.
What is sugar metabolism?
The liver represents the central organ for carbohydrate metabolism, especially since it stores the complex carbohydrate glycogen as an energy reserve. Sugar metabolism is basically concerned with all metabolic processes in which carbohydrates are involved. Its most important function is to provide energy for the organism. The liver is the central organ for carbohydrate metabolism, especially since it stores the complex carbohydrate glycogen as an energy reserve. Carbohydrates are absorbed as single sugars (e.g. glucose), double sugars (disaccharose) or multiple sugars (complex carbohydrates such as starch) from food and processed by the body. Sugar metabolism is mainly controlled by the two hormones insulin and glucagon. While insulin lowers blood glucose levels, glucagon increases them. The breakdown of carbohydrates (glycolysis) forms the backbone of the entire metabolism. This process produces pyruvate (salt of pyruvic acid), which plays a central role as an intermediate product of many metabolic pathways. If carbohydrates are not supplied through the diet, their synthesis from amino acids takes place in the body. Therefore, the human body is not necessarily dependent on carbohydrates in the diet. Nevertheless, sugar metabolism takes place because glucose is constantly produced via this metabolic pathway.
Function and task
The body is supplied with energy via sugar metabolism. The main suppliers of energy are the carbohydrates contained in food. They are present here in the form of simple sugars, double sugars (disaccharides) and multiple sugars (polysaccharides, starch). Monosaccharides and disaccharides are immediately able to provide energy for the organism. Polysaccharides, however, must first be broken down into glucose before they are absorbed by the intestine. The glucose enters the blood and is transported through the body by the circulatory system to supply energy to the organs. Glucose is absorbed through cell membranes with the help of insulin. If the blood glucose concentration rises due to the supply of carbohydrates, the islet cells of the pancreas are stimulated to secrete insulin via various regulatory mechanisms. The insulin then binds to special membrane receptors in the body’s cells and makes the membranes permeable to glucose. If less energy is needed, insulin ensures that the excess glucose is absorbed into the liver, muscles and fat cells. In the liver and muscles, the glucose building blocks are then reassembled into a polysaccharide (glycogen). Glycogen is stored and used as an energy reserve when needed. In the fat cells, glucose is converted into body fat and stored there as such. If the blood glucose level is too low, another hormone, glucagon, ensures the formation or release of glucose. Blood glucose levels that are too low occur, for example, in a state of hunger, when energy requirements are high, or when insulin output is too high. Glucagon ensures the breakdown of glycogen or the conversion of amino acids into glucose. Thus, the interaction of insulin and glucagon ensures a balanced blood glucose level. Due to the ability of glucagon to form glucose from amino acids, a carbohydrate supply via food is not absolutely necessary in humans. The necessary basic supply of glucose is thus guaranteed in any case for important organs such as the brain. In addition to glucose, sugar metabolism also includes such simple sugars as fructose or galactose.
Diseases and ailments
In connection with sugar metabolism, the most important disease is the so-called diabetes mellitus, also known as diabetes. Diabetes is characterized by an excessively high blood glucose level, which is already above 126 mg/dl in the fasting state. Between 100 and 126 mg/dl, prediabetes is suspected. The cause of the high blood glucose level may be the absence, deficiency or reduced effectiveness of insulin. Diabetes mellitus is not a uniform disease.Thus, diabetes can initially be divided into two distinguishable types:
Type I diabetes mellitus is characterized by the absence or deficiency of insulin. This form of diabetes is often congenital or acquired at an early age. The cause of the insulin deficiency may be the destruction of the islets of Langerhans by an autoimmune disease or their absence from birth. The patient is dependent on lifelong administration of insulin. Otherwise, the sugar could not be utilized. Type II diabetes mellitus was often called adult-onset diabetes because it used to occur mostly at older ages. Today, it often occurs in childhood or adolescence. The cause is acquired insulin resistance due to poor diet, obesity, lack of exercise, smoking or drinking. In this form of the disease, insulin is produced, but its effectiveness decreases because fewer and fewer insulin receptors are present. Due to the increasing insulin resistance, the pancreas has to produce more and more insulin without the blood glucose level dropping significantly. A vicious circle forms that can lead to complete exhaustion of the pancreas. If blood glucose levels are permanently high, the blood vessels and nerve endings are damaged in the long term. As a result, a wide variety of complaints occur, such as arteriosclerosis, circulatory disorders in the limbs, diabetic feet due to nerve damage, polyneuropathy, eye damage up to blindness, and much more. In the early stages of the disease, blood glucose levels can be restored to normal through lifestyle changes. However, when the degenerative changes are too advanced, diabetes is often the starting point of various chronic diseases. A low-carbohydrate diet and plenty of exercise can significantly improve sugar metabolism.
