Cholesterol

Cholesterol (Gk.: chole = bile, stereos = solid) is a natural substance with physical properties similar to the formula steroida fat, like many other natural compounds. Cholesterol is an important substance for the body to wake synthesis (formation) substances such as cell membranes, insulation around nerve fibers, sex hormones and young kidneys, vitamin D and bile acids. Cholesterol is found in animal fats, egg yolks and gallstones. Absorption or resorption of food from the intestine occurs only when there is enough bile acids to mengemulsinya. The amount of absorption depends on the composition of foods, such as the content of cholesterol, animal fat and vegetable fibers. Every day can be absorbed as much as 200-600 mg of cholesterol. Besides the body, especially the liver, forming 700-1000 mg of cholesterol a day to meet their needs.

Cholesterol and eggs. Has long been suspected that the egg can increase blood cholesterol levels, the intake should be limited to one egg a week. Today it is known that healthy people can eat an egg every day without increasing the risk of PJP (heart and blood vessel disease) or stroke (JAMA 1999; 281: 1387-94 and BMJ 1999; 318: 1094). Maybe once saturated fatty acid levels were higher in eggs also play a role in this case.

Synthesis. Under normal circumstances the liver release cholesterol into the blood as needed. But if the food contains a lot of cholesterol or saturated animal fats that will increase blood cholesterol levels. Once absorbed by the body, some of the fat in food is used as an energy source, through the decomposition reaction: CO2 + H2O + calories. Other reforms substances in the liver is used again for the synthesis of cholesterol and other fats. Synthesis of endogenous (forming process that occurs in the body by itself) is tailored to the needs, eg during fasting or when there are a lot of cholesterol in food, its formation is reduced. Conversely, when bile acid levels decreased, increased synthesis of bile acids to dibiotransformasikan be again. Typically, about 2/3 of the body's cholesterol is synthesized endogenously, only 1/3 comes from food (exogenous). Some people, by default tend to form many endogenous cholesterol, regardless of his eating habits. They are people with familial hypercholesterolemia (offspring).

1.2 Lipoprotein

Cholesterol is a substance with similar physical properties of fats or lipids. Blood lipids, especially to type (1) cholesterol, (2) triglycerides (oils), (3) and free fatty acids (4) phospholipids, which are not soluble in the blood (more than 50% of blood consists of water). Transported in the blood plasma lipids in the form of particles that have skin (shell) consisting of hydrophilic phospholipids and cholesterol free. The surface layer of these particles also consist of apolipoprotein that functions as a "tag" (label identifier) ​​for cell receptors. Complexes with proteins called lipoproteins that transport can be mixed well with blood. Approximately two-thirds of plasma lipoproteins synthesized in the liver.

There are several types of lipoproteins are distinguished according lipidanya content is:

(1) chylomicron (read: chylomicrons) was formed in the intestinal wall of triglycerides and cholesterol from food. Then TG (trigeliserida) is hydrolyzed by lipoproteinlipase and the rest is excreted by the liver.

Kiomikron has value ratio of the highest fat and protein (more fat than protein), and his job is to bring energy in the form of fat to muscle. Although these molecules high in fat, it is believed that chylomicrons does not cause heart disease for two reasons. First, the chylomicrons are 90% triglycerides in weight and has less cholesterol in it. Second, people with normal lipid metabolism clearing chylomicrons from the blood stream for about 12 hours after eating fatty foods. This is the reason why doctors ask patients to fast for 12 hours before having a cholesterol test-so chylomicrons in the blood will not be there at all. This allows the doctor to get accurate figures from other lipoproteins, which are considered to have a greater impact on the risk of heart disease or atherosclerosis (hardening due to calcification of blood vessels due to deposition of LDL - see 1.5) in general.

In a normal lipid metabolism, the gut is usually packed triglycerides from food consumed Iemak into chylomicrons and released into the bloodstream. Chylomicrons and release a lot of fatty acids to tissues tissues (such as liver and skeletal muscles), provides energy to the heart and skeletal muscle needs to function properly. The remaining remnants of chylomicrons go to the liver where it will be filtered out of the bloodstream.

There are three possibilities that occur when fatty acids carried in chylomicrons in circulation. (1) They can be used as energy by the various tissues of the body, (2) they can be taken up by the adipose tissue (fat) and stored as energy in the future, or (3) they can go to the liver, where they can be used as fuel or converted into triglycerides. If they go to the heart, this organ will take the triglycerides that have been modified, packaged with cholesterol and protein, and releasing these packages into the bloodstream as lipoproteins by very low density (VLDL).

(2) VLDL (very low density lipoprotein) of the liver, which together carry most of the chylomicron TG and free fatty acids into muscle and fat tissue.

VLDL, lipoprotein or very low density is made by the liver from fat, protein, and carbohydrates are taken from food. VLDL perform the same function as chylomicrons carry fat into muscle so that the muscle can be used as energy. However, unlike chylomicrons, when the body releases most of triglycerides from the VLDL particles to produce energy, it will be the LDL VLDL.

(3) LDL (low density lipoprotein) transports the majority (70% kl) blood cholesterol from the liver who have LDL receptors to the network. The process of withdrawal from the plasma via LDL receptors is the primary mechanism in controlling LDL levels. In particular, oxy-LDL, the cholesterol that has been oxidized by free radicals, can be deposited on vessel walls and cause atherosclerosis.

(4) HDL (High Density Lipoprotein) transports excess cholesterol (and fatty acid) - which can not be used by peripheral tissues - back to the liver for conversion into bile acids. With the help of the enzyme LCAT (= lecithine cholesterol acyl-transferase), which has terendap the vessel wall "dissolved" (chemically: ester formation by lecithin) and transported to the liver as well. HDL has the highest density.

Lipoprotein particles (VLDL and chylomicron) aterogen is not because of their large size (30-600 nm diameter) that does not allow to penetrate the walls of blood vessels. Instead LDL particles (diameter 19-25 can easily penetrate the arterial wall and the main cause of atherosclerosis. HDL which has the smallest particles (4-10 nm in diameter) capable of transporting cholesterol from the arterial wall, which is the basis of anti - aterogennya.

* Apolipoprotein (apo) protein is an important component of various lipid components of lipoproteins in addition to the above. Apo serves a.l. as ligand (label, tags) for binding to the LDL receptor. There are five types, namely apo-A, B, C, D and E, with the sub-class. In addition to lipid fractions, as well as apo-B and apo-AI (protein in each VLDL / LDL and HDL) aterogen turns out to be strong and is an indicator of risk for PJP anyway.

Table 1: Types of lipoproteins, diameter, density and composition.

1.3 hyperlipidemia (HLD)

Hyperlipidemia (more precisely hiperlipoproteinemia) is a disorder or disease in a state where the blood lipoprotein levels increase due to a genetic predisposition (hereditary) (primary hiperlipidaemia) and / or associated also with eating habits (diet) individually.
For primary hyperlipidemia can be divided into two types, namely:

- Hypercholesterolemia with increased levels of LDL (cholesterol and total cholesterol).
Disturbances in lipid metabolism is the most common disorder and about 5% of cases are familial (hereditary), but in 95% of cases the cause is unknown.

- Hypertriglyceridemia, is a disorder or disease where TG levels increased.

Chylomicrons are formed from fatty food in the intestinal wall was about 85% consists of TG and only about 4% of the cholesterol in the capillary-muscle tissue and tissue-fat, TG lipoproteinlipase overhauled under the influence of a product that still contains a lot of TG and cholesterol. This product is typically further processed by the liver. But if the processing is not perfect, then the rest after the meal is still circulating in the blood for a long time, thus going hypertriglyceridemia. HLD type can be determined by the rising levels of chylomicrons immediately after eating. In general, these disorders far today has caused serious forms of atherosclerosis and the occurrence of problems around the age of 30 years.

1.4 Limitation Normal Cholesterol Value

Normal cholesterol values ​​varied geographically. In the countries of Asia and Africa, everyday foods usually contain fewer calories, animal fat and protein. Thus, the value is generally lower than in Western countries, such as total cholesterol levels each an average of 3.9 mmol / l (= 150 mg%) and 5.2 mmol / l (= 200 mg%) . In table 2 are given the numbers that are considered normal for Indonesian and Western countries, and the number rises above normal.
Table 2 Numbers Cholesterol and TG

All babies are born with average cholesterol levels of 80-100 mg% (2 to 2.6 mmol / l) during which growth gradually increased until kl 150 mg% (3.9 mmol / 1). In developing countries, in general, the levels settled at this level, whereas in Western countries rise in value by an average of 220 mg% (5.8 mmol / 1). The rise is not physiologically normal and expected no causal relationship with the composition of the food that is not right, especially containing too much saturated fat.