Dextrose is an older term, still commonly used in medicine today, for the sugar glucose. Glucose is a six-carbon sugar molecule that is a predominant source of energy in the blood. It is derived from food and transferred from the blood into cells. Insulin facilitates this transfer. Since insulin is a hormone that helps regulate glucose levels, the level of glucose affects insulin levels and the level of insulin affects glucose levels. Once insulin signals cells to take up glucose, the glucose is used to make the energy-containing product adenosine triphosphate, or ATP.
Role of Glucose
Glucose can be ingested in food. Many carbohydrates are broken down into glucose in the intestine. It is absorbed, and levels of glucose rise in the bloodstream. Alternatively, when levels of glucose are dropping in the blood, the liver may release glucose. The levels of glucose in the blood are tightly regulated to maintain health. Glucose triggers insulin to be released, which in turn affects the glucose level.
Insulin Signaling
When the glucose levels rise in the blood, insulin is released from the pancreas. It binds to receptors on target cells throughout the body. These receptors cause a reaction that results in the cell adding glucose transporters to its surface. The glucose transporters take up glucose from the bloodstream. For the entire process to begin, however, there must be a mechanism involving signaling from glucose to the insulin-releasing cells in the pancreas.
Insulin Release
Insulin is synthesized and released by beta cells of the pancreas. The insulin is stored in little compartments in the cell called vesicles. The beta cells have open glucose channels on their surface. When a meal causes the glucose levels to rise, glucose flows into the beta cells, where it is metabolized to make ATP. The ATP signals special channels on the surface of the beta cells, which changes the electrical current of the cell. Specifically, it closes potassium channels, resulting in the cells going from a negative to a positive charge. This signal leads to the insulin-containing vesicles binding to the surface of the cells and releasing insulin into the blood.
Diabetes and Insulin
Glucose and insulin signaling can be deranged in type I and type II diabetes mellitus. In type I diabetes, the glucose entering the bloodstream fails to stimulate the pancreas to release insulin. Usually this is caused by damage to the beta cells. In type II diabetes, the cells of the body do not respond to insulin, so that glucose is not taken up into the cells.
References
- “Physiology”; Linda S.Costanzo; 2010
- "Lehninger Principles of Biochemistry"; David L. Nelson, et al.; 2004
- “Robbins and Cotran Pathologic Basis of Disease”; Vinay Kumar, et al.; 2009
