Insulin and glucagon are key hormones that regulate blood sugar. How do they interact to keep blood sugar constant?
In multicellular organisms, the functions of the constituent cells are regulated by the nervous and endocrine systems. The nervous system responds quickly through nerve signals, while the endocrine system is responsible for slow but continuous regulation through hormones. The action of the endocrine system is caused by hormones secreted by the endocrine glands. The glands that secrete hormones are both digestive and endocrine glands. There are more than a million small cell clusters all over the glands. These are called Langerhans islands. On Langerhans Island, there are β-cells that secrete insulin and α-cells that secrete glucagon.
The main function of insulin is to lower the concentration of glucose in the blood by promoting the influx of glucose into cells. It also causes the liver to store glucose in the form of glycogen, increases protein synthesis in cells, and promotes fat production. This process plays an important role in regulating energy metabolism and storage in our bodies. For example, after eating, glucose absorbed from food enters the blood, increasing the amount of blood sugar. At this time, insulin moves the increased blood sugar to the cells, which use it as an energy source or store it if necessary.
On the other hand, glucagon has an opposite effect to insulin, and its main effect is to increase the concentration of glucose in the blood by breaking down the glycogen stored in the liver into glucose. It also plays a role in separating amino acids and fatty acids from the storage site into the blood. Glucagon is mainly activated in a state of fasting, and at this time, it promotes the secretion of glucose from the liver to meet the body’s energy needs. For example, when exercising or being in a state of prolonged fasting, glucagon is essential for maintaining the body’s energy balance.
The secretion of insulin and glucagon is regulated by the amount of blood sugar. After eating, the amount of glucose in the blood, or the amount of blood sugar, increases, which stimulates the β-cells and increases the amount of insulin secretion. Insulin absorbs glucose in the blood and moves it to the cells, which reduces the amount of blood sugar and therefore the amount of insulin secretion. On the other hand, when a person does not eat for a long time or when the blood sugar level drops below 70 mg/dl due to exercise, the α cells of the Langerhans island increase the amount of glucagon secreted. Glucagon breaks down the glycogen stored in the liver to make glucose and send it to the blood. As a result, the blood sugar level rises again.
The importance of controlling blood sugar levels is evident in many parts of the body. For example, if the proper blood sugar level is not maintained, the brain may not receive enough glucose, which is its energy source, and may malfunction. Generally, a blood sugar level of 99 mg/dl or less after an eight-hour fast is considered normal, and a level of 126 mg/dl or higher is considered diabetes. These criteria emphasize the importance of blood sugar control and show how insulin and glucagon interact to maintain homeostasis in the body.
Glucose is used as the main energy source in the brain. The brain requires a stable supply of glucose throughout the day, and insulin and glucagon work in opposition to each other to help maintain this glucose concentration within a normal range. Therefore, if the balance of these two hormones is disrupted, various problems can occur throughout the body. For example, a lack or malfunction of insulin can lead to diabetes, which can cause long-term health problems. On the other hand, excessive secretion of glucagon can cause hyperglycemia, which requires proper treatment and management.
In addition to insulin and glucagon, several hormones are involved in blood sugar regulation. For example, cortisol, which is secreted by the adrenal glands, plays a role in raising blood sugar and is especially important in stressful situations. Growth hormone also contributes to raising blood sugar, which plays an important role in the growth and development of the body. These various hormones interact with each other to maintain homeostasis in the body.
Understanding the mechanisms of blood glucose control provides an important foundation for the treatment and management of metabolic diseases such as diabetes. Recent studies are exploring drugs that increase insulin sensitivity, treatments that improve β-cell function, and new hormonal control mechanisms. These studies are contributing to the development of more effective diabetes treatments and the establishment of prevention strategies.
