Bile acids. Functions of bile acids. Biochemistry of the liver

Over the past few decades, it has been possible to obtain a lot of new information about bile and its acids. In this regard, there was a need to revise and expand the notion of their significance for the life of the human body.

The role of bile acids. General information

Rapid development and improvement of research methods made it possible to study bile acids in more detail. For example, now there is a clearer idea of metabolism, their interaction with proteins, lipids, pigments and contents in tissues and liquids. Confirmed information indicating that bile acids are of great importance not only for the normal functioning of the gastrointestinal tract. These compounds are involved in many processes in the body. It is also important that thanks to the use of the latest research methods, it was possible to determine most precisely how bile acids behave in the blood, and also how they affect the respiratory system. Among other things, the compounds affect some parts of the central nervous system. Their importance in intracellular and external membrane processes is proved. This is due to the fact that bile acids act as surfactants in the internal environment of the body.

Historical facts

This type of chemical compounds was discovered by scientist Shtrekker in the middle of the XIX century. He managed to find out that the bile of cattle has two organic acids. The first of them contains sulfur. The second also contains this substance, but it has a completely different formula. In the process of the cleavage of these chemical compounds, cholic acid is formed. As a result of the conversion of the first above-mentioned compound, glycerol is formed. At the same time, the other bile acid forms a completely different substance. It is called taurine. As a result, the original two compounds were given names that were the same name for the substances produced. So tauro- and glycocholic acid appeared respectively. This discovery of the scientist gave a new impetus to the study of this class of chemical compounds.

Bile acid sequestrants

These substances are a group of drugs that have a hypolipidemic effect on the human body. In recent years, they have been actively used to lower the level of cholesterol in the blood. This allowed to significantly reduce the risk of various cardiovascular pathologies and ischemic disease. At the moment, another group of more effective drugs is widely used in modern medicine. These hypolipidemic agents are statins. They are used much more often because of fewer side effects. At present, bile acid sequestrants are used less and less. Sometimes they are used only as part of a comprehensive and supportive treatment.

Detailed Information

The steroid class includes monocarboxylic hydroxy acids. They are active solids that are poorly soluble in water. These acids arise from the processing of cholesterol by the liver. In mammals they consist of 24 carbon atoms. The composition of the dominant bile compounds in different animal species is different. These types form in the body taucholic and glycolic acids. Chenodeoxycholic and cholus compounds belong to the class of primary. How are they formed? In this process, liver biochemistry matters. Primary compounds arise as a result of the synthesis of cholesterol. Next, a conjugation process takes place with taurine or glycine. These types of acids are then secreted in the bile. Lithocholic and desoxycholic substances are part of the secondary compounds. They are formed in the large intestine from primary acids under the influence of local bacteria. The rate of absorption of deoxycholic compounds is much higher than that of lithocholic compounds. Other secondary bile acids arise in very small volumes. For example, ursodeoxycholic belongs to them. If there is chronic cholestasis, then these compounds are present in huge quantities. The normal ratio of these substances is 3: 1. While with cholestasis, the bile acid content is significantly exceeded. Micelles are aggregates of their molecules. They are formed only when the concentration of these compounds in the aqueous solution exceeds the limit. This is due to the fact that bile acids belong to surface-active substances.

Features of cholesterol

This substance is poorly soluble in water. The rate of solubility of cholesterol in bile depends on the ratio of lipid concentration, as well as the molar concentration of lecithin and acids. Mixed micelles arise only when the normal proportion of all these elements is maintained. They contain cholesterol. The precipitation of its crystals is carried out under the condition that this ratio is violated. Functions of bile acids are not limited to removing cholesterol from the body. They promote absorption of fats in the intestines. Micelles are also formed during this process.

Traffic connections

One of the main conditions for the formation of bile is the active movement of acids. These compounds play an important role in the transport of electrolytes, water in the small intestine and large intestine. They are solid powdery substances. Their melting point is quite high. They have a bitter taste. Bile acids are poorly soluble in water, whereas in alkaline and alcohol solutions it is good. These compounds are derived from cholanic acid. All such acids arise exclusively in cholesteric hepatocytes.

Impact

The main value among all acid compounds is salt. This is due to a number of properties of these products. For example, they are more polar than salts of free bile acids, have a small size of the limiting concentration of micelle formation and are more rapidly secreted. The liver is the only organ that can convert cholesterol to special cholanic acids. This is due to the fact that the enzymes that participate in the conjugation are contained in the hepatocytes. The change in their activity is directly dependent on the composition and rate of oscillation of the bile acids of the liver. The synthesis process is regulated by the negative feedback mechanism . This means that the intensity of this phenomenon is in relation to the current of secondary bile acids in the liver. The rate of their synthesis in the human body is quite low - from two hundred to three hundred milligrams per day.

Main goals

Bile acids have a wide range of purposes. In the human body, they mainly carry out the synthesis of cholesterol and affect the absorption of fats from the intestine. In addition, the compounds are involved in the regulation of biliary excretion and bile formation. These substances also have a strong influence on the process of digestion and assimilation of lipids. Their compounds are collected in the small intestine. The process occurs under the influence of monoglycerides and free fatty acids, which are on the surface of fat deposits. In this case, a thin film forms, which prevents the connection of small droplets of fat into more voluminous ones. Due to this, a strong decrease in surface tension occurs . This leads to the formation of micellar solutions. They, in turn, facilitate the action of pancreatic lipase. With the help of fat reaction, it splits them into glycerol, which is subsequently absorbed by the wall of the intestine. Bile acids combine with fatty acids that do not dissolve in water, and form choleinic acids. These compounds are easily cleaved and quickly absorbed by the villi of the upper part of the small intestine. Choleic acids are converted into micelles. Further, they are absorbed into the cells, while easily overcoming their membranes. Information was obtained from the most recent studies in this field. They prove that the interrelation of fatty and bile acids in the cell breaks up. The first represent the final result of lipid absorption. The latter - through the portal vein penetrate into the liver and blood.