The function of an insulin receptor is to control the movement of the hormone insulin from the blood stream into certain types of cells. Insulin, which is crucial for many cell processes, is involved in the metabolism of carbohydrate and fat by providing fuel for cells through regulating glucose and storing body fat. Eating too much and exercising too little can lead to faulty insulin receptor processes, which can lead to insulin resistance and diabetes.
Not all cells have insulin receptors. The cells that do include muscle and fat cells. An insulin receptor responds to a cell’s need for insulin by moving back and forth from the surface to the interior of the cell. Up regulation is when the insulin receptors move to the surface of the cell. Down regulation is when the receptors move to the exterior.
In muscle cells, the receptors allows for specific muscle tissues, such as those in parts of the body that have been exercised, to take insulin when needed. For example, when a body builder who was weight training his upper body next eats, his upper body muscle cells will have up regulated, and so will take in insulin, which allows them to take in glucose and refuel. Muscle cells in the legs, however, do not need to be refueled, so they will be in a down regulated state and will not take in insulin.
The actions of insulin in removing glucose from the blood, which are enabled by insulin receptors, also assist in maintaining stable blood sugar levels. This is important because some types of cells, such as nerve cells, do not have insulin receptors and do not use insulin to regulate the intake of glucose. These cells uptake glucose through diffusion, and they are very affected by blood glucose levels.
Overeating, lack of exercise, and genetic predispositions may cause an insulin receptor to stop functioning correctly. Poorly functioning insulin receptors can lead to insulin resistance, which occurs when too few insulin receptors are at the cells’ surfaces to respond to insulin, allowing glucose to enter. The cells are in effect starving, but they don’t have the means to allow glucose to enter.
Insulin resistance can lead to diabetes mellitus type 2. With this disorder, the body produces sufficient insulin but is not able to use it because the insulin receptor processes do not uptake enough insulin, leaving high levels of glucose in the blood. This disease can lead to blindness and cardiovascular disease.