The liver is a vital organ in that it helps with various body processes, including body detoxification and bile production. It can also be described as a "glucose buffer." A buffer is something that acts as a protective barrier against excessive fluctuations. Therefore, a healthy liver helps keep blood glucose within the normal range of 80 to 120 mg/dL. This is an important aspect of liver function, because hyperglycemia (high blood sugar) and hypoglycemia (low blood sugar) can both be dangerous for the human body.
Liver Anatomy & Function
With approximately 1.4 kg (3 lb) in the average adult, the liver is the heaviest gland. It is also the second largest human organ, after the skin. The liver is located slightly below the lowest ribs, and occupies the upper right side of the abdomen. It is made up of cells (hepatocytes) arranged in layers that surround and separate the numerous channels and small bile ducts that travel the whole organ. It is through these channels that arteries and veins carry blood to and from the liver. It is also through these same channels that the liver receives the different substances it needs to process. The liver thus acts as a major filter of the blood traveling from the digestive tract to the rest of the body.
In order to help maintain blood sugar levels, the liver uses various processes that are regulated by various hormones, such as insulin and glucagon. These processes are: glycogen storage, lipogenesis, glycogen breakdown, gluconeogenesis, and the conversion of other sugars into glucose.
How the Liver Regulates Blood Glucose
During absorption and digestion, the carbohydrates contained in a meal are reduced to their simplest form, glucose. As nutrient-rich blood travels through the hepatic portal vein, the liver removes excess glucose from the blood, to process and store it. Hepatocytes use glycogenesis to convert most of the excess glucose into glycogen, the storage form of glucose. A smaller fraction of excess glucose is stored in the form of fats via lipogenesis.
Blood glucose concentration sometimes drops, as in short-term fasts (24 to 48 hours). In such cases, the liver enters glycogenolysis. In this process, hepatocytes mobilize their stores of glycogen, reconvert them into glucose, and continually release them it into the blood, until levels approach normal range.
Long fasts deplete the body glycogen stores, and require additional sources of blood sugar. When blood glucose drops during a long fast, the liver enters gluconeogenesis. This is a mechanism whereby the liver, along with the kidneys, uses lactic acid, glycerol, and amino acids to make glucose.
When blood sugar drops because a person’s diet does not meet the body’s needs in glucose, the liver may convert other sugars into glucose. Examples of such “convertible sugars” include sucrose, fructose, and galactose.
When Blood Sugar Is Not Well Regulated
Improper blood glucose regulation can occur for different reasons, including lifestyle, diet, hormone-related problems, or dysfunction of organs, such as the liver, pancreas, or kidneys. The result may be hyperglycemia (high blood sugar) or hypoglycemia (low blood sugar).
Hyperglycemia and hypoglycemia can both be dangerous for the human body. On one hand, hypoglycemia can be harmful because some organs, such as the brain, need glucose to carry their functions. On the other hand, chronically high blood sugar elevates the risk of vascular accidents by speeding plaque-formation in blood vessels.
Resources
Understanding the Process Behind the Regulation of Blood Glucose
References
Gastrointestinal Physiology; Functional Anatomy of the Liver and Biliary System (Chapter 10); Kim E. Barrett; 2006
Diabetes Journal (Vol. 55); Effects of Hyperglycemia and Hyperinsulinemia on Circulating Tissue Factor Pro-coagulant Activity and Platelet CD40 Ligand; Vijender R. Vaidyula et al; January 2006
 |
 |
