Cholesterol transport | Cholesterol

Cholesterol transport

Since cholesterol is insoluble in water, it must be bound to proteins for transport in blood. These are called lipoproteins. After absorption from the intestine, the cholesterol is absorbed by chylomicrons.

These transport the cholesterol to the liver. Other lipoproteins (VLDL, IDL and LDL) transport the home-made cholesterol from the liver to the tissues and are therefore also called “bad” cholesterol. The HDLs, on the other hand, absorb the cholesterol from the tissues and transport it back to the liver.

They are therefore referred to as the “good cholesterol”. The “bad” LDL is broken down from the blood in two different ways. Most of the LDL is metabolised via the “LDL receptor pathway”.

These receptors can be found on almost all cells of arteries and liver cells and absorb the “bad” cholesterol through them. Another way is the scavenger pathway. This leads to the breakdown and storage of cholesterol in the blood vessels. Ultimately, this can lead to plaque formation and blockage of blood vessels, which can manifest itself clinically in a heart attack or stroke.

Standard values

The total cholesterol is given for values between 110-230 mg/dl. This applies to women and men. – The LDL level should be between 70-180 mg/dl for women and men.

In both cases significantly higher values increase the risk of stroke and heart attack. – The triglycerides (TAG) should be < 150mg/dl. – Since HDL is the “good cholesterol”, there is no upper limit for this, the higher the HDL the better. It should be at least > 35mg/dl.

Clinic

Related to cholesterol are familial hypercholesterolemia and the formation of gallstones. Familial hypercholesterolemia is a congenital disorder of cholesterol metabolism. It is associated with greatly increased blood cholesterol levels and cannot be influenced by food intake.

In one of the known forms of hypercholesterolemia, the LDL receptors are incompletely formed or completely absent, so that the cholesterol cannot be absorbed from the blood. This leads to an increased uptake of LDL via the scavenger pathway and thus to a significantly increased risk of heart attacks and other vascular diseases at a younger age. The most common form is autosomal dominant familial hypercholesterolemia with a prevalence of 1:500.

Patients often stand out in the laboratory chemically due to very high total cholesterol and LDL cholesterol values, with normal values for HDL cholesterol and triglycerides. The disease can only be treated symptomatically by inhibiting the body’s own synthesis. This is achieved by statins, which lead to the inhibition of HMG-CoA reductase and thus inhibit the body’s own build-up of cholesterol.

Gallstones are caused by a change in the composition of the bile. As a result, large amounts of cholesterol can no longer be emulsified in the bile and gallstones are formed. These consist of 80% partial cholesterol, 50% of the stones consist of pure cholesterol.

Gallstones can occur without symptoms, but they can also lead to gall bladder inflammation, severe pain and bile drainage problems if the stones block the way. In these cases the gallbladder often has to be removed. This also minimises the risk of gallstones forming again, as gallstones can only form in the gall bladder itself.