Carbohydrate metabolism | The function of the liver

Carbohydrate metabolism

The carbohydrate metabolism is colloquially also called sugar metabolism. Some cells in the body, especially the red blood cells and nerve cells, depend on a continuous supply of blood sugar (glucose). Since humans consume their food at intervals with their few daily meals, they need a system with which they can store the elevated concentrations of nutrients after eating and release them between meals as needed.

This is essentially the task of the liver. After a meal, the liver is stimulated by the hormone insulin to store the increased concentration of blood sugar in a special form (glycogen). In total, up to 10% of the total weight of the liver, i.e. about 150 grams, can be stored in the liver as sugar in this form.

When the blood sugar level begins to drop in the time between meals, the liver, under the influence of the hormone glucagon, starts to break down the stored sugar. This sugar is released into the blood in the service of the body. However, the liver’s sugar stores are only sufficient for less than a day without food.

Therefore, the liver also has the ability to produce sugar from proteins. The proteins are primarily obtained by breaking down the protein in muscle cells. Some rare, always genetic diseases affect this function of the liver.

Individual proteins (enzymes), which are necessary for the release of sugar into the blood, are missing. In these cases, the patient can eat normally and fill his or her stores. But the moment the body is dependent on the release of sugar into the blood, the defect becomes apparent and the patient suffers from hypoglycaemia. The therapy is a careful diet with regular, small meals.

Fat metabolism

The liver is capable of storing numerous vital substances and releasing them when needed. These include vitamins A, B12, D, E and folic acid as well as the metals iron and copper. Diseases have been described for both metals in which a genetic defect leads to the abnormal storage of these metals, which can also lead to liver damage and even liver cirrhosis (Wilson’s disease, hemosiderosis).