Glucose Homeostasis & the Liver

Blood glucose homeostasis is an important biologic process that involves a variety of mechanisms. The muscles, kidneys and liver all have important functions in glucose regulation. The liver is especially important for its ability to store glycogen and prevent low blood glucose.

Human digestive system with the liver highlighted in red (Image: SomkiatFakmee/iStock/Getty Images)

Importance of Glucose Homeostasis

Maintaining blood glucose within the normal range is referred to as glucose homeostasis. Your brain and nervous system depend solely on glucose for fuel and require a steady supply of glucose at all times. It is critical that your blood glucose concentration remains within the range of 70 to 110 mg/dL to supply your brain and nervous system with adequate fuel. Low blood glucose can lead to symptoms such as dizziness or lack of concentration, whereas, over time, high blood glucose can damage blood vessels and nerves.

Role of the liver

Your liver plays a key role in blood glucose homeostasis. After a meal when blood glucose is high, the liver has the ability to remove glucose from the blood and store it as part of a molecule called glycogen. In between meals, as blood glucose begins to decline, the liver can make new glucose to release into the blood. Hormones, such as insulin and glucagon, regulate these homeostatic processes.

Liver Glycogen

In your body, glycogen serves as the glucose storage molecule. Glucose is stored as glycogen when blood glucose concentrations exceed energy demands. Glycogen is found primarily in your liver, but is found in smaller amounts in your muscles. Glycogen can be synthesized, or broken down, according to the needs of your body. Insulin directs the synthesis of glycogen, thus helping to lower elevated blood glucose. In response to the hormone glucagon, stored liver glycogen can be broken down and released into the blood to help raise blood glucose.

Gluconeogenesis

In addition to the breakdown of glycogen, in an effort to raise blood glucose, the liver participates in another process called gluconeogenesis, which is the synthesis of new glucose molecules from other substances such as lactic acid and amino acids. Gluconeogenesis is important for preventing low blood glucose during times of fasting. Similar to the breakdown of glycogen, gluconeogenesis is also stimulated by the hormone glucagon. Together, the processes of glycogen synthesis and breakdown and gluconeogenesis in the liver help maintain glucose homeostasis.