Introduction
Sugar appears in the blood mainly as glucose, which is also the basic unit involved in carbohydrate transport and storage in the body. Thus, the regulation of sugar is actually the regulation of glucose. The breakdown of glucose provides the main source of energy for essential functions of cells in the body. Glucose is taken into the cells by an active system of transport where it is broken down to provide energy.
The levels of glucose are closely monitored and maintained between 70 to 110 milligrams per deciliter of blood. When the level of glucose falls below this range, it becomes insufficient to meet the needs of the cells. When the level rises above this range, it causes malfunctioning in certain organ systems, as well as providing a breeding medium for multiplication of germs in the body.
Regulation of Blood Glucose
The organ responsible for maintaining blood glucose levels is the pancreas, which is located in the abdomen. It regulates blood glucose levels by means of two hormones, namely insulin and glucagon.
Increased blood glucose, usually after a meal or a drink, triggers the pancreas to release insulin. Released insulin has several actions all geared towards the reduction of blood glucose. Insulin acts on the skeletal muscle to increase insulin utilization for energy and to promote glucose storage in the form of glycogen, while shutting down the use of other sources of energy like fatty acids and protein. Insulin also acts on the liver to increase glucose uptake for storage as glycogen and production of triglyceride fats via glycerol formation. Finally, insulin acts on the fat cells to block the breakdown of fat and increase glucose uptake which is used to produce glycerol and triglycerides. These effects of insulin effectively increase clearance of glucose from the blood leading to fall in blood levels (Raju and Cryer, 2004).
Falling levels of blood glucose shuts down insulin production and stimulates release of glucagon. Glucagon acts on the liver to promote glycogen breakdown and release of glucose into the blood. Glucagon also stimulates the breakdown of protein for the manufacture of glucose. Glucagon also acts on the liver to shut down fat production and promote fatty acid breakdown. The overall effect of glucagon is the increase in blood levels of glucose (Jiang and Zhang, 2003).
Thus, between these two hormones produced by the pancreas, the blood level of glucose is largely preserved within normal limits. More recent research is focused on other hormone-like substances that interact with insulin and glucagon, thus modifying the effects of these two hormones
clinical correlates
A deficiency of insulin leads to persistently high levels of glucose from failure of the liver or muscle to take up glucose and manufacture glycogen. Protein and fat stores are broken down for use as energy sources and the manufacture of glucose. Blood glucose level rises to the point where glucose spills over into the urine from the kidneys. This situation is called Diabetes mellitus. Sometimes, the problem is not a deficiency in the amount of insulin released, but a deficiency in the response of the tissues to insulin in diabetic patients.
