How does diet affect blood levels of LDL in individuals with familial hypercholesterolemia?
Diet affects blood levels of low-density lipoprotein (LDL) by influencing both the activity of LDL receptors and the synthesis of cholesterol in the liver. LDL receptors bind to LDL, which is the primary carrier of cholesterol in the blood. The receptors sit on the outer surface of many types of cells, where they pick up LDL circulating in the bloodstream and transport them into the cell. Once inside the cell, the LDL is broken down to release cholesterol. The cholesterol is then used by the cell, stored, or removed from the body. After the receptors drop off their "cargo," they are recycled back to the cell surface to pick up more LDL. LDL receptors therefore play a critical role in regulating the amount of cholesterol in the blood. They are particularly abundant in the liver, which is the organ responsible for removing most excess cholesterol from the body. The number of LDL receptors on the surface of liver cells determines how quickly cholesterol (in the form of LDL) is removed from the bloodstream.
The goal of dietary therapy in individuals with familial hypercholesterolemia (FH) is to increase the activity of LDL receptors while decreasing the synthesis of cholesterol in the liver. Two dietary factors have a major effect on LDL receptors: the amount of cholesterol in the diet and the amount of saturated fat in the diet. Both cholesterol and fat inhibit the activity of LDL receptors, and thus inhibit the removal of LDL from the blood by the liver. Dietary cholesterol and fat can also enhance or diminish the therapeutic effects of cholesterol-lowing drugs in individuals with FH.
How might familial hypercholesterolemia be treated?
The overall goal of treatment for familial hypercholesterolemia (FH) is to lower the risk for atherosclerosis (build-up of plaque in the arteries) by lowering the LDL cholesterol levels in the blood stream. The first step in treatment for individuals with the heterozygous form (also called the autosomal dominant form) is changing the diet to reduce the total amount of fat eaten. This may be accomplished by limiting the amount of beef, pork, and lamb in the diet; cutting out butter, whole milk, fatty cheeses and oils; and eliminating egg yolks, organ meats and other sources of saturated fat from animals. Dietary counseling is often recommended to help individuals change their eating habits. Exercise and weight loss may also help in lowering cholesterol levels.
Individuals with the more severe, homozygous form of FH (also called the autosomal recessive form) need more aggressive therapies to treat their significantly elevated levels of cholesterol. Drug therapy is often not effective enough at lowering LDL cholesterol levels. Therefore, individuals with this form may need periodical LDL apheresis, a procedure that removes LDL from the blood. In some cases, major surgery such as a liver transplant is necessary.
Last updated: 10/22/2013
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