Lipids constitute a large and quite heterogeneous in chemical composition group of organic substances that make up living cells, soluble in low-polar organic solvents (ether, benzene, chloroform, etc.) and insoluble in water. In general, they are regarded as derivatives of fatty acids.
The peculiarity of the structure of lipids is the presence in their molecules of simultaneously polar (hydrophilic) and non-polar (hydrophobic) structural fragments, which gives lipids an affinity for both water and the non-aqueous phase. Lipids are biphilic substances, which allows them to carry out their functions at the interface.
10.1. Classification
Lipids are divided into simple(two-component), if the products of their hydrolysis are alcohols and carboxylic acids, and complex(multicomponent), when, as a result of their hydrolysis, other substances are also formed, for example, phosphoric acid and carbohydrates. Simple lipids include waxes, fats and oils, as well as ceramides, complex ones - phospholipids, sphingolipids, and glycolipids (Scheme 10.1).
Scheme 10.1.General classification of lipids
10.2. Structural components of lipids
All lipid groups have two essential structural components - higher carboxylic acids and alcohols.
Higher fatty acids (HFA). Many higher carboxylic acids were first isolated from fats, hence the name fatty. Biologically important fatty acids can be saturated(Table 10.1) and unsaturated(Table 10.2). Their common structural features are:
Are monocarboxylic;
Includes an even number of carbon atoms in the chain;
Have a cis-configuration of double bonds (if present).
Table 10.1.Essential Saturated Fatty Acids Lipids
In natural acids, the number of carbon atoms ranges from 4 to 22, but acids with 16 or 18 carbon atoms are more common. Unsaturated acids contain one or more double bonds with a cis configuration. The double bond closest to the carboxyl group is usually located between the C-9 and C-10 atoms. If there are several double bonds, then they are separated from each other by the methylene group CH 2.
The IUPAC rules for DRCs allow the use of their trivial names (see Tables 10.1 and 10.2).
Currently, its own nomenclature of unsaturated HFAs is also used. In it, the terminal carbon atom, regardless of the chain length, is denoted by the last letter of the Greek alphabet ω (omega). The position of the double bonds is counted not as usual from the carboxyl group, but from the methyl group. So, linolenic acid is designated as 18: 3 ω-3 (omega-3).
Linoleic acid itself and unsaturated acids with a different number of carbon atoms, but with the arrangement of double bonds also at the third carbon atom, counting from the methyl group, constitute the omega-3 HFA family. Other types of acids form similar families of linoleic (omega-6) and oleic (omega-9) acids. For normal human life, the correct balance of lipids of three types of acids is of great importance: omega-3 (flaxseed oil, fish oil), omega-6 (sunflower, corn oil) and omega-9 (olive oil) in the diet.
Of the saturated acids in the lipids of the human body, the most important are palmitic C 16 and stearic C 18 (see Table 10.1), and of the unsaturated ones, oleic C18: 1, linoleic C18: 2, linolenic and arachidonic C 20: 4 (see table 10.2).
It should be emphasized the role of polyunsaturated linoleic and linolenic acids as compounds, irreplaceable for humans ("vitamin F"). They are not synthesized in the body and must be supplied with food in an amount of about 5 g per day. In nature, these acids are found mainly in vegetable oils. They promote
Table 10 .2. Essential lipid unsaturated fatty acids
* Included for comparison. ** For cis isomers.
normalization of the lipid profile of blood plasma. Linetol, which is a mixture of ethyl esters of higher fatty unsaturated acids, is used as a hypolipidemic herbal medicine. Alcohols. Lipids may include:
Higher monohydric alcohols;
Polyhydric alcohols;
Amino alcohols.
In natural lipids, saturated and less often unsaturated long-chain alcohols (C 16 and more) are most often found with an even number of carbon atoms. As an example of higher alcohols, cetyl CH 3 (CH 2 ) 15 OH and melissilic CH 3 (CH 2) 29 OH alcohols that are part of the waxes.
Polyhydric alcohols in most natural lipids are represented by the trihydric alcohol glycerol. There are other polyhydric alcohols, such as the dihydric alcohols ethylene glycol and propanediol-1,2, as well as myo-inositol (see 7.2.2).
The most important amino alcohols that are part of natural lipids are 2-aminoethanol (colamine), choline, also related to the α-amino acids serine and sphingosine.
Sphingosine is an unsaturated long chain dihydric amino alcohol. The double bond in sphingosine has trance-configuration, and asymmetric atoms C-2 and C-3 - D-configuration.
Alcohols in lipids are acylated with higher carboxylic acids at the corresponding hydroxyl groups or amino groups. In glycerol and sphingosine, one of the alcoholic hydroxyls can be esterified with substituted phosphoric acid.
10.3. Simple lipids
10.3.1. Waxes
Waxes are esters of higher fatty acids and higher monohydric alcohols.
Waxes form a protective lubricant on human and animal skin and prevent plants from drying out. They are used in the pharmaceutical and perfumery industries in the manufacture of creams and ointments. An example is cetyl palmitic acid ester(cetin) - the main component spermacet. Spermaceti is secreted from the fat contained in the cranial cavities of sperm whales. Another example is melissil ester of palmitic acid- a component of beeswax.
10.3.2. Fats and oils
Fats and oils are the most abundant group of lipids. Most of them belong to triacylglycerols - complete esters of glycerol and HFA, although mono- and diacylglycerols are also found and are involved in the metabolism.
Fats and oils (triacylglycerols) are esters of glycerol and higher fatty acids.
In the human body, triacylglycerols play the role of a structural component of cells or a storage substance ("fat depot"). Their energy value is about twice that of proteins.
or carbohydrates. However, an increased level of triacylglycerols in the blood is one of the additional risk factors for the development of coronary heart disease.
Solid triacylglycerols are called fats, liquid ones are called oils. Simple triacylglycerols contain residues of the same acids, mixed ones - different.
In the composition of triacylglycerols of animal origin, residues of saturated acids usually predominate. Such triacylglycerols are generally solids. In contrast, vegetable oils contain mainly residues of unsaturated acids and have a liquid consistency.
Below are examples of neutral triacylglycerols and their systematic and (in parentheses) commonly used trivial names based on the names of their constituent fatty acids are indicated.
10.3.3. Ceramides
Ceramides are N-acylated derivatives of sphingosine alcohol.
Ceramides are present in small amounts in the tissues of plants and animals. Much more often they are part of complex lipids - sphingomyelins, cerebrosides, gangliosides, etc.
(see 10.4).
10.4. Complex lipids
Some complex lipids are difficult to classify unambiguously, since they contain groupings that allow them to be simultaneously assigned to different groups. According to the general classification of lipids (see Figure 10.1), complex lipids are usually divided into three large groups: phospholipids, sphingolipids, and glycolipids.
10.4.1. Phospholipids
The phospholipid group includes substances that cleave phosphoric acid during hydrolysis, for example, glycerophospholipids and some sphingolipids (Scheme 10.2). In general, phospholipids are characterized by a fairly high content of unsaturated acids.
Scheme 10.2.Classification of phospholipids
Glycerophospholipids. These compounds are the main lipid components of cell membranes.
According to the chemical structure, glycerophospholipids are derivatives l -glycero-3-phosphate.
l-Glycero-3-phosphate contains an asymmetric carbon atom and therefore can exist as two stereoisomers.
Natural glycerophospholipids have the same configuration, being derivatives of l-glycero-3-phosphate, which is formed during metabolism from dihydroxyacetone phosphate.
Phosphatides. Among glycerophospholipids, the most common are phosphatides - ester derivatives of l-phosphatidic acids.
Phosphatidic acids are derivatives l -glycero-3-phosphate esterified with fatty acids at alcoholic hydroxyl groups.
As a rule, in natural phosphatides in position 1 of the glycerol chain there is a saturated residue, in position 2 - an unsaturated acid, and one of the hydroxyls of phosphoric acid is esterified with a polyhydric alcohol or amino alcohol (X is the residue of this alcohol). In the body (pH ~ 7.4) the remaining free hydroxyl of phosphoric acid and other ionogenic groups in phosphatides are ionized.
Examples of phosphatides are compounds in which phosphatidic acids esterified for phosphate hydroxyl with the corresponding alcohols:
Phosphatidylserines, the esterifying agent is serine;
Phosphatidylethanolamines, the esterifying agent is 2-aminoethanol (in the biochemical literature it is often, but not quite correctly, called ethanolamine);
Phosphatidylcholines, esterifying agent - choline.
These esterifying agents are interrelated because ethanolamine and choline fragments can be metabolized from a serine fragment by decarboxylation and subsequent methylation with S-adenosylmethionine (SAM) (see 9.2.1).
A number of phosphatides, instead of an amine-containing esterifying agent, contain residues of polyhydric alcohols - glycerol, myoinositol, etc. The phosphatidylglycerols and phosphatidylinositols given below as an example refer to acidic glycerophospholipids, since their structures lack aminoalcohol fragments that impart neutral and rhodylethanolamines to phosphatidylethanolamines.
Plasmalogens. Less common in comparison with ester glycerophospholipids are lipids with an ether bond, in particular plasmalogens. They contain the remainder of the unsaturated
* For convenience, the way of writing the configuration formula of the myo-inositol residue in phosphatidylinositols has been changed in comparison with the one given above (see 7.2.2).
alcohol linked by an ether bond to the C-1 atom of glycero-3-phosphate, such as, for example, plasmalogens with an ethanolamine moiety - L-phosphatidal ethanolamines. Plasmalogens make up 10% of all lipids in the central nervous system.
10.4.2. Sphingolipids
Sphingolipids are structural analogs of glycerophospholipids in which sphingosine is used instead of glycerol. The ceramides discussed above (see 10.3.3) are another example of sphingolipids.
An important group of sphingolipids are sphingomyelins, first discovered in nervous tissue. In sphingomyelins, the hydroxyl group at C-1 of ceramide is esterified, as a rule, with choline phosphate (less often with colamine phosphate); therefore, they can also be attributed to phospholipids.
10.4.3. Glycolipids
As the name suggests, the compounds of this group include carbohydrate residues (more often D-galactose, less often D-glucose) and do not contain a phosphoric acid residue. Typical representatives of glycolipids - cerebrosides and gangliosides - are sphingosine-containing lipids (therefore, they can be considered sphingolipids as well).
V cerebrosides the ceramide residue is linked to D-galactose or D-glucose by a β-glycosidic bond. Cerebrosides (galactocerebrosides, glucocerebrosides) are part of the membranes of nerve cells.
Gangliosides- carbohydrate-rich complex lipids - were first isolated from the gray matter of the brain. Structurally, gangliosides are similar to cerebrosides, differing in that instead of a monosaccharide, they contain a complex oligosaccharide containing at least one residue V-acetylneuraminic acid (see Appendix 11-2).
10.5. Lipid properties
and their structural components
A feature of complex lipids is their biphilicity, due to non-polar hydrophobic and highly polar ionized hydrophilic groups. In phosphatidylcholines, for example, the hydrocarbon radicals of fatty acids form two non-polar "tails", and the carboxyl, phosphate and choline groups form the polar part.
At the interface, these compounds act as excellent emulsifiers. In the composition of cell membranes, lipid components provide a high electrical resistance of the membrane, its impermeability to ions and polar molecules, and permeability to non-polar substances. In particular, most anesthetic drugs dissolve well in lipids, which allows them to penetrate the membranes of nerve cells.
Fatty acids are weak electrolytes( p K a~ 4.8). They are dissociated to a small extent in aqueous solutions. At pH< p K a non-ionized form predominates, at pH> p K a, that is, under physiological conditions, the ionized form RCOO - prevails. Soluble salts of higher fatty acids are called soaps. Sodium salts of higher fatty acids are solid, potassium salts are liquid. As salts of weak acids and strong bases of soaps are partially hydrolyzed in water, their solutions are alkaline.
Natural unsaturated fatty acids having cis-configuration of a double bond, have a large supply of internal energy and, therefore, in comparison with trance-isomers are thermodynamically less stable. Their cis-trans -isomerization proceeds easily upon heating, especially in the presence of radical initiators. Under laboratory conditions, this transformation can be carried out by the action of nitrogen oxides formed during the decomposition of nitric acid upon heating.
Higher fatty acids exhibit the general chemical properties of carboxylic acids. In particular, they readily form the corresponding functional derivatives. Fatty acids with double bonds exhibit the properties of unsaturated compounds - they add hydrogen, hydrogen halides and other reagents to the double bond.
10.5.1. Hydrolysis
With the help of the hydrolysis reaction, the structure of lipids is established, and also valuable products (soaps) are obtained. Hydrolysis is the first stage in the utilization and metabolism of dietary fats in the body.
Hydrolysis of triacylglycerols is carried out either by exposure to superheated steam (in industry), or by heating with water in the presence of mineral acids or alkalis (saponification). In the body, lipid hydrolysis takes place under the action of lipase enzymes. Some examples of hydrolysis reactions are shown below.
In plasmalogens, as in ordinary vinyl ethers, the ether bond is cleaved in an acidic, but not in an alkaline environment.
10.5.2. Addition reactions
Lipids containing residues of unsaturated acids in the structure are attached via double bonds with hydrogen, halogens, hydrogen halides, and water in an acidic medium. Iodine number is a measure of the unsaturation of triacylglycerols. It corresponds to the number of grams of iodine that can be added to 100 g of the substance. The composition of natural fats and oils and their iodine numbers vary within a fairly wide range. As an example, we give the interaction of 1-oleoyl-distearoylglycerol with iodine (the iodine number of this triacylglycerol is 30).
The catalytic hydrogenation (hydrogenation) of unsaturated vegetable oils is an important industrial process. In this case, hydrogen saturates the double bonds and liquid oils turn into solid fats.
10.5.3. Oxidation reactions
Oxidative processes involving lipids and their structural components are quite diverse. In particular, the oxidation of unsaturated triacylglycerols by oxygen in the air during storage (autoxidation, see 3.2.1), accompanied by hydrolysis, is part of a process known as oil rancidity.
The primary products of the interaction of lipids with molecular oxygen are hydroperoxides, which are formed as a result of a free radical chain process (see 3.2.1).
Lipid peroxidation - one of the most important oxidative processes in the body. It is the main cause of damage to cell membranes (for example, in radiation sickness).
Structural fragments of unsaturated higher fatty acids in phospholipids serve as targets for attack active forms of oxygen(ROS, see Appendix 03-1).
When attacked, in particular, by the hydroxyl radical HO ", the most active of the ROS, of the LH lipid molecule, a homolytic cleavage of the C-H bond in the allyl position occurs, as shown by the example of the model of lipid peroxidation (Scheme 10.3). The resulting allyl type radical L" instantly reacts with molecular oxygen in the oxidation medium to form the lipid-peroxyl radical LOO ". From this moment, a chain cascade of lipid peroxidation reactions begins, since there is a constant formation of allyl lipid radicals L", which resume this process.
Lipid peroxides LOOH are unstable compounds and can decompose spontaneously or with the participation of variable valence metal ions (see 3.2.1) with the formation of lipidoxyl radicals LO "capable of initiating further oxidation of the lipid substrate. Such an avalanche-like process of lipid peroxidation poses a risk of destruction of membrane structures cells.
The intermediate formed radical of the allyl type has a mesomeric structure and can further undergo transformations in two directions (see Scheme 10.3, paths a and b), leading to intermediate hydroperoxides. Hydroperoxides are unstable and decompose even at ordinary temperatures with the formation of aldehydes, which are further oxidized into acids - the end products of the reaction. The result is generally two monocarboxylic and two dicarboxylic acids with shorter carbon chains.
Unsaturated acids and lipids with residues of unsaturated acids under mild conditions are oxidized with an aqueous solution of potassium permanganate, forming glycols, and in harder conditions (with rupture of carbon-carbon bonds), the corresponding acids.
LIPIDS - This is a heterogeneous group of natural compounds, completely or almost completely insoluble in water, but soluble in organic solvents and in each other, giving high molecular weight fatty acids during hydrolysis.
In a living organism, lipids perform various functions.
Biological functions of lipids:
1) Structural
Structural lipids form complex complexes with proteins and carbohydrates, of which the membranes of the cell and cellular structures are built, and participate in a variety of processes in the cell.
2) Spare (energy)
Reserve lipids (mainly fats) are the body's energy reserve and are involved in metabolic processes. In plants, they accumulate mainly in fruits and seeds, in animals and fish, in subcutaneous adipose tissues and tissues surrounding internal organs, as well as in the liver, brain and nervous tissues. Their content depends on many factors (species, age, nutrition, etc.) and in some cases amounts to 95-97% of all lipids released.
Caloric content of carbohydrates and proteins: ~ 4 kcal / gram.
Caloric content of fat: ~ 9 kcal / gram.
The advantage of fat as an energy reserve, in contrast to carbohydrates, is hydrophobicity - it is not associated with water. This ensures the compactness of fat reserves - they are stored in anhydrous form, taking up a small volume. On average, a person's supply of pure triacylglycerols is approximately 13 kg. These reserves could be enough for 40 days of fasting under conditions of moderate physical activity. For comparison: the total reserves of glycogen in the body is approximately 400 grams; when starving, this amount is not enough even for one day.
3) Protective
Subcutaneous adipose tissue protects animals from cooling, and internal organs from mechanical damage.
The accumulation of fat in the body of humans and some animals is seen as an adaptation to irregular diets and to living in a cold environment. Especially large reserves of fat are found in animals that hibernate (bears, marmots) and are adapted to living in cold conditions (walruses, seals). The fetus has practically no fat, and appears only before birth.
Protective lipids of plants - waxes and their derivatives, covering the surface of leaves, seeds and fruits - constitute a special group in terms of their functions in a living organism.
4) An important component of food raw materials
Lipids are an important component of food, largely determining its nutritional value and taste. The role of lipids in various processes of food technology is extremely important. Spoilage of grain and its processing products during storage (rancidity) is primarily associated with a change in its lipid complex. Lipids isolated from a number of plants and animals are the main raw material for obtaining the most important food and industrial products (vegetable oil, animal fats, including butter, margarine, glycerin, fatty acids, etc.).
2 Classification of lipids
There is no generally accepted classification of lipids.
It is most expedient to classify lipids depending on their chemical nature, biological functions, as well as in relation to some reagents, for example, to alkalis.
According to their chemical composition, lipids are usually divided into two groups: simple and complex.
Simple lipids - esters of fatty acids and alcohols. These include fats , waxes and steroids .
Fats - esters of glycerin and higher fatty acids.
Waxes - esters of higher aliphatic alcohols (with a long carbohydrate chain of 16-30 C atoms) and higher fatty acids.
Steroids - esters of polycyclic alcohols and higher fatty acids.
Complex lipids - in addition to fatty acids and alcohols, they contain other components of various chemical nature. These include phospholipids and glycolipids .
Phospholipids - these are complex lipids, in which one of the alcohol groups is associated not with FA, but with phosphoric acid (phosphoric acid can be combined with an additional compound). Depending on what alcohol is included in the phospholipids, they are subdivided into glycerophospholipids (contain alcohol glycerin) and sphingophospholipids (contain sphingosine alcohol).
Glycolipids Are complex lipids in which one of the alcohol groups is associated not with FA, but with a carbohydrate component. Depending on which carbohydrate component is included in the glycolipids, they are subdivided into cerebrosides (contain a monosaccharide, disaccharide or a small neutral homooligosaccharide as a carbohydrate component) and gangliosides (contain an acidic hetero-oligosaccharide as a carbohydrate component).
Sometimes in an independent group of lipids ( minor lipids ) secrete fat-soluble pigments, sterols, fat-soluble vitamins. Some of these compounds can be classified as simple (neutral) lipids, while others are complex.
According to another classification, lipids, depending on their relationship to alkalis, are divided into two large groups: saponifiable and unsaponifiable.... The group of saponifiable lipids includes simple and complex lipids, which, when interacting with alkalis, hydrolyze to form salts of high molecular weight acids, called "soaps". The group of unsaponifiable lipids includes compounds that do not undergo alkaline hydrolysis (sterols, fat-soluble vitamins, ethers, etc.).
According to their functions in a living organism, lipids are divided into structural, storage and protective.
Structural lipids are mainly phospholipids.
Storage lipids are mainly fats.
Protective lipids of plants - waxes and their derivatives, covering the surface of leaves, seeds and fruits, animals - fats.
FATS
The chemical name for fats is acylglycerols. These are esters of glycerol and higher fatty acids. "Acyl-" means "fatty acid residue".
Depending on the number of acyl radicals, fats are divided into mono-, di- and triglycerides. If the molecule contains 1 fatty acid radical, then the fat is called MONOACYLGLYCERIN. If there are 2 fatty acid radicals in the molecule, then the fat is called DIACYLGLYCERIN. In humans and animals, TRIACYLGLYCERINS predominate (contain three radicals of fatty acids).
The three hydroxyls of glycerol can be esterified either with just one acid, for example palmitic or oleic, or with two or three different acids:
Natural fats contain mainly mixed triglycerides, including residues of various acids.
Since the alcohol in all natural fats is the same - glycerin, the differences observed between fats are solely due to the composition of fatty acids.
More than four hundred carboxylic acids of various structures have been found in fats. However, most of them are present only in small quantities.
The acids found in natural fats are monocarboxylic acids built from unbranched carbon chains containing an even number of carbon atoms. Acids containing an odd number of carbon atoms, having a branched carbon chain or containing cyclic moieties are present in minor amounts. The exceptions are isovaleric acid and a number of cyclic acids found in some very rare fats.
The most common acids in fats contain 12 to 18 carbon atoms and are often referred to as fatty acids. Many fats contain small amounts of low molecular weight acids (C 2 -C 10). Acids with more than 24 carbon atoms are present in waxes.
The glycerides of the most common fats in a significant amount include unsaturated acids containing 1-3 double bonds: oleic, linoleic and linolenic. Arachidonic acid containing four double bonds is present in animal fats; acids with five, six or more double bonds are found in fats of fish and marine animals. Most of the unsaturated lipid acids have a cis-configuration, their double bonds are isolated or separated by a methylene (-CH 2 -) group.
Of all the unsaturated acids found in natural fats, oleic acid is the most abundant. In very many fats, oleic acid makes up more than half of the total mass of acids, and only a few fats contain less than 10%. Two other unsaturated acids, linoleic and linolenic, are also very widespread, although they are present in significantly lower amounts than oleic acid. Linoleic and linolenic acids are found in significant quantities in vegetable oils; for animal organisms, they are essential acids.
Of the saturated acids, palmitic acid is almost as widespread as oleic acid. It is present in all fats, with some containing 15-50% of the total acid content. Stearic and myristic acids are widespread. Stearic acid is found in large quantities (25% or more) only in the storage fats of some mammals (for example, in sheep fat) and in the fats of some tropical plants, for example, in cocoa butter.
It is advisable to divide the acids contained in fats into two categories: major and minor acids. The main acids of fat are acids, the content of which in fat exceeds 10%.
Physical properties of fats
As a rule, fats do not withstand distillation and decompose even when distilled under reduced pressure.
The melting point, and, accordingly, the consistency of fats depends on the structure of the acids that make up their composition. Solid fats, that is, fats that melt at a relatively high temperature, consist mainly of glycerides of saturated acids (stearic, palmitic), and oils that melt at a lower temperature and are thick liquids contain significant amounts of glycerides of unsaturated acids (oleic , linoleic, linolenic).
Since natural fats are complex mixtures of mixed glycerides, they melt not at a certain temperature, but in a certain temperature range, and they are preliminarily softened. To characterize fats, as a rule, is used solidification temperature, which does not coincide with the melting point - it is slightly lower. Some natural fats are solids; others are liquids (oils). The solidification temperature varies within wide limits: -27 ° C for linseed oil, -18 ° C for sunflower oil, 19-24 ° C for cow and 30-38 ° C for beef lard.
The solidification temperature of fat is determined by the nature of its constituent acids: the higher the content of saturated acids, the higher it is.
Fats dissolve in ether, polyhalogenated derivatives, carbon disulfide, aromatic hydrocarbons (benzene, toluene) and gasoline. Solid fats are difficult to dissolve in petroleum ether; insoluble in cold alcohol. Fats are insoluble in water, but they can form emulsions that are stabilized in the presence of surfactants (emulsifiers) such as proteins, soaps, and some sulfonic acids, mainly in a slightly alkaline environment. Milk is a natural emulsion of protein-stabilized fat.
Chemical properties of fats
Fats enter into all chemical reactions characteristic of esters, but their chemical behavior has a number of features associated with the structure of fatty acids and glycerol.
Among the chemical reactions involving fats, several types of transformations are distinguished.
What are lipids, what is the classification of lipids, what is their structure and function? The answer to this and many other questions is provided by biochemistry, which studies these and other substances that are of great importance for metabolism.
What it is
Lipids are organic substances that do not dissolve in water. The functions of lipids in the human body are diverse.
Lipids - this word means "small particles of fat"
This is primarily:
- Energy. Lipids serve as a substrate for storing and using energy. The breakdown of 1 gram of fat releases about 2 times more energy than the breakdown of protein or carbohydrates of the same weight.
- Structural function. The structure of lipids determines the structure of the cell membranes in our body. They are arranged in such a way that the hydrophilic part of the molecule is inside the cell, and the hydrophobic part is on its surface. Due to these properties of lipids, each cell, on the one hand, is an autonomous system, fenced off from the outside world, and on the other hand, each cell can exchange molecules with others and with the environment using special transport systems.
- Protective. The surface layer that we have on the skin and serves as a kind of barrier between us and the outside world is also composed of lipids. In addition, they, in the composition of adipose tissue, provide the function of thermal insulation and protection from harmful external influences.
- Regulatory. They are part of vitamins, hormones and other substances that regulate many processes in the body.
The general characteristics of lipids are based on structural features. They have twofold properties, since they have soluble and insoluble parts in the molecule.
Intake of the body
Lipids partly enter the human body with food, partly they are able to synthesize endogenously. The splitting of the main part of dietary lipids occurs in the duodenum 12 under the influence of pancreatic juice secreted by the pancreas and bile acids in the bile. Having split, they are resynthesized again in the intestinal wall and, already in the composition of special transport particles ─ lipoproteins, ─ are ready to enter the lymphatic system and the general bloodstream.
With food, a person needs to get about 50-100 grams of fat every day, which depends on the state of the body and the level of physical activity.
Classification
The classification of lipids, depending on their ability to form soaps under certain conditions, divides them into the following classes of lipids:
- Saponified. The so-called substances that, in an environment with an alkaline reaction, form salts of carboxylic acids (soaps). This group includes simple lipids, complex lipids. Both simple and complex lipids are important for the body, they have a different structure and, accordingly, lipids perform different functions.
- Unsaponifiables. They do not form carboxylic acid salts in an alkaline medium. This biological chemistry includes fatty acids, derivatives of polyunsaturated fatty acids ─ eicosanoids, cholesterol, as the most prominent representative of the main class of sterols-lipids, as well as its derivatives ─ steroids and some other substances, for example, vitamins A, E, etc.
General classification of lipids
Fatty acid
Substances that belong to the group of so-called simple lipids and are of great importance for the body are fatty acids. Depending on the presence of double bonds in the non-polar (water-insoluble) carbon "tail", fatty acids are divided into saturated (do not have double bonds) and unsaturated (have one or even more double carbon-carbon bonds). Examples of the first: stearic, palmitic. Examples of unsaturated and polyunsaturated fatty acids: oleic, linoleic, etc.
It is the unsaturated fatty acids that are especially important for us and must be taken with food.
Why? Because they:
- Serve as a component for the synthesis of cell membranes, participate in the formation of many biologically active molecules.
- They help to maintain the normal functioning of the endocrine and reproductive systems.
- They help prevent or slow down the development of atherosclerosis and many of its consequences.
Fatty acids are divided into two large groups: unsaturated and saturated
Inflammatory mediators and more
Another type of simple lipids are such important mediators of internal regulation as eicosanoids. They have a unique (like almost everything in biology) chemical structure and, accordingly, unique chemical properties. The main basis for the synthesis of eicosanoids is arachidonic acid, which is one of the most important unsaturated fatty acids. It is eicosanoids that are responsible in the body for the course of inflammatory processes.
Their role in inflammation can be briefly described as follows:
- They change the permeability of the vascular wall (namely, increase its permeability).
- Stimulates the release of leukocytes and other cells of the immune system into the tissue.
- With the help of chemicals, they mediate the movement of immune cells, the release of enzymes and the absorption of particles foreign to the body.
But the role of eicosanoids in the human body does not end there, they are also responsible for the blood coagulation system. Depending on the developing situation, eicosanoids can dilate blood vessels, relax smooth muscles, reduce aggregation, or, if necessary, cause opposite effects: vasoconstriction, contraction of smooth muscle cells and thrombus formation.
Eicosanoids - a large group of physiologically and pharmacologically active compounds
Studies were carried out according to which people who received sufficient amounts of the main substrate for the synthesis of eicosanoids ─ arachidonic acid ─ with food (found in fish oil, fish, vegetable oils) suffered less from diseases of the cardiovascular system. Most likely, this is due to the fact that such people have a more perfect exchange of eicosanoids.
Substances of a complex structure
Complex lipids are a group of substances that are no less important for the body than simple lipids. The main properties of this group of fats:
- Participate in the formation of cell membranes, along with simple lipids, and also provide intercellular interactions.
- They are part of the myelin sheath of nerve fibers, which is necessary for the normal transmission of nerve impulses.
- They are one of the important components of a surfactant ─ a substance that ensures breathing processes, namely, prevents the alveoli from collapsing during exhalation.
- Many of them play the role of receptors on the cell surface.
- The significance of some complex fats secreted from cerebrospinal fluid, nervous tissue, and heart muscle is not fully understood.
The simplest representatives of this group of lipids include phospholipids, glyco- and sphingolipids.
Cholesterol
Cholesterol is a substance of a lipid nature with the most important value in medicine, since the violation of its metabolism negatively affects the state of the whole organism.
Some of the cholesterol is ingested with food, and some is synthesized in the liver, adrenal glands, gonads and skin.
It also participates in the formation of cell membranes, the synthesis of hormones and other chemically active substances, and also participates in the metabolism of lipids in the human body. Indicators of cholesterol in the blood are often studied by doctors, as they show the state of lipid metabolism in the human body as a whole.
Lipids have their own special transport forms ─ lipoproteins. With their help, they can be carried with the blood stream without causing embolism.
Disorders of fat metabolism are most rapidly and clearly manifested by disorders of cholesterol metabolism, the predominance of atherogenic carriers (the so-called low and very low density lipoproteins) over antiatherogenic (high density lipoproteins).
The main manifestation of lipid metabolism pathology is the development of atherosclerosis.
It manifests itself as a narrowing of the lumen of arterial vessels throughout the body. Depending on the prevalence in the vessels of various localizations, a narrowing of the lumen of the coronary vessels develops (accompanied by angina pectoris), cerebral vessels (with impaired memory, hearing, possible headaches, noise in the head), renal vessels, vessels of the lower extremities, vessels of the digestive system with corresponding symptoms ...
Thus, lipids are at the same time an indispensable substrate for many processes in the body and, at the same time, when fat metabolism is disturbed, they can cause many diseases and pathological conditions. Therefore, fat metabolism requires control and correction when such a need arises.
07.04.2009
In the diet, fat is approximately 44 percent. Recommendations on the correct diet advise that this figure does not exceed 30 percent of the total calories, and 25 percent would be even better.
Your fat intake should lean towards polyunsaturated and monounsaturated fat, with a maximum saturated fat of no more than 10 percent or less, of that total 25 percent fat.
* To reduce the fat content of omelettes, remove the yolk of every other egg; this will reduce the fat and cholesterol levels, and you won't even feel the difference.
* Cottonseed oil is 25 percent saturated fat and is not the best to use.
* Soybean oil changes taste during long-term storage due to changes in the levels of linolenic acid it contains.
* Sixty-four percent of the calories from caviar are from fat.
* Butter absorbs fridge odors and should be kept in a closed container.
* Butter, stored in the refrigerator for only two weeks. If you need to store it for a longer time, store it in the freezer.
* Eight ounces of potato chips equals 12 to 20 teaspoons of fat.
* Try using water instead of fat in some recipes. It is true that it makes dressings from fats, etc., the taste becomes even, but if you mix water with flour, with cornstarch (corn flour) or potato starch, it will save you extra calories.
* Oils should be stored in dark containers and stored in a dark, cool place to reduce the risk of rancidity.
* When carob is made into candy, fat is added for texture, which brings the fat level close to that of real chocolate. In fact, the cocoa butter used in chocolate is 60 percent saturated fat, while the fat in carob candies is, in most cases, 85 percent saturated fat.
* Using non-stick cookware and vegetable oil sprays will reduce your fat intake.
* Never eat salad dressing or mayonnaise-based salad until you are sure they were chilled before you are ready to eat them. Neglect is the culprit in thousands of food poisoning cases every year.
* Oils related to fish are healthier than those related to meat. Fish contains a high percentage of omega fatty acids.
* Any margarine containing coconut or palm oil will be very high in saturated fat. They are now called tropical oils (tropical plant oils) on labels.
* New fat substitutes continue to appear in our products. Do not forget that they are all the same synthetic production, and not a natural product. They should not be seen as a panacea for fat replacement in our diet.
* The best butter is made from AA grade sweet cream.
* An ounce of seeds (sunflower) contains 160 calories and is not considered a diet food.
* Burrito with sour cream and guacamole (a sauce made from mashed avacado, spiced tomatoes and mayonnaise) can contain up to 1000 calories and 59 percent fat.
* Studies have shown that stearic acid, one of the saturated fats, has little effect on raising cholesterol levels.
* New Low Fat Peanut Butter has the same calories per serving as regular peanut butter, approximately 190 calories per serving, sweeteners have been added instead of fat.
* When you store some oils in the refrigerator, they may become hazy (opaque, light hazy) due to the formation of harmless crystals. Manufacturers sometimes chill the oils before they are released for sale and remove these crystals in a process called winterizing. These oils will now remain clear when cooled.
* Pork fat has large crystals, while butter is small. This is highly dependent on the texture of the fat and can be controlled during processing. The size of the crystals can be changed by stirring (shaking) the oil while it is cooling.
* Studies have shown that people on a diet miss fat more than sweets.
* People on a high-fat diet are more prone to colon cancer, prostate cancer, or breast cancer. Future research may show that it also has a detrimental effect on the immune system.
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They are organic compounds insoluble in water. They are composed of fatty acid molecules linked in a chain of hydrogen and carbon atoms. If the carbon atoms are connected to each other by a stable bond, then such fatty acids are called "saturated". Accordingly, if the carbon atoms are loosely bound, then the fatty acids are unsaturated. For the human body, the most important are arachidonic, linoleic, and oleic fatty acids.
The separation according to the chemical formula into saturated and unsaturated acids has been developed for a long time. Unsaturated, in turn, are subdivided into polyunsaturated and monounsaturated. Today it is known that saturated acids in our food can be found in pates, meat, milk, eggs. And unsaturated ones are found in olive, peanut, sunflower oil; fish, goose and duck fat.
The term "lipids" denotes the entire spectrum of fat-like substances extracted by fat solvents (chloroform, ether, gasoline).
Lipids include esters of triacylglycerols. These are substances in which glycerol binds to three fatty acid residues. Lipids include oils and fats. Oils contain a large amount of unsaturated acids and have a liquid consistency (with the exception of margarines). Fats, on the other hand, are hard and contain a lot of saturated acids.
Lipids fall into two main categories depending on their origin:
- Vegetable fats (olive oil, nut oil, margarine, etc.).
- Animal fats (found in fish, meat, cheese, butter, cream, etc.).
When fats combine with "bad" carbohydrates, the metabolism is disrupted, and as a result, most of them are deposited in the body by fat layers.
As a rule, in our diet, an excess of fat - fried fatty foods, in particular - fast food, is becoming more popular and habitual. At the same time, food may well be tasty, even if you give up sunflower and butter when cooking it.
Some of the lipids directly affect the increase in blood cholesterol levels. Cholesterol can be roughly divided into "good" and "bad". The goal of a healthy diet is the dominance of "good" cholesterol over "bad". The total blood level of this substance should be normal. If there is too much cholesterol, then it is deposited on the walls of our blood vessels and disrupts blood circulation, which disrupts the trophism of organs and tissues. And insufficient blood supply, in turn, leads to serious disruption of the functioning of organs. The main danger is the possibility of tearing off a blood clot from the wall and spreading it through the blood stream throughout the body. His blood clot will clog the blood vessels of the heart, the person will be instantly fatal. Everything happens so instantly that it is simply impossible to help and save a person.
Not all fats increase the amount of "bad" cholesterol in the blood, some of them, on the contrary, lower its level.
- Fats that raise cholesterol levels are found in butter, lard, meat, cheese, smoked and dairy products, and palm oil. These are saturated fats.
- Fats, which almost do not contribute to the formation of cholesterol, are found in eggs, oysters, and poultry meat (without skin).
- The fats that help lower cholesterol are vegetable oils: olive, rapeseed, corn, sunflower.
Saturated
Frequent consumption of saturated fat is harmful to health. Sausages, lard, butter and cheese should not form the basis of the diet. By the way, palm and coconut oils also contain saturated fatty acids. When shopping for groceries, pay attention to the ingredients in them. Palm oil is a frequent “guest” in our diet, although we do not always know about it. However, some housewives will use it for baking instead of margarine. Meat contains stearic acid, which is contraindicated in large quantities for the body. The amount of fat in the daily diet should not exceed 50 grams. An optimal nutritional balance should be 50% monounsaturated fatty acids, 25% polyunsaturated, and 25% saturated.Most people consume too much saturated fat to the detriment of unsaturated fats. Of these, about 70% are "invisible" (sausages, sets for aperitifs, cheeses, chips, and, of course, meat), and 30% are "visible" (this is all that can be used for frying dishes and spreading on bread) ...
Those fats that the body did not use remain in reserve in the body and, when combined with sugars, become the main cause of excess weight. And only physical activity and a balanced diet can correct this situation. Therefore, it is imperative to adjust the intake of fatty acids in accordance with their expenditure.
Monounsaturated
This type of fat is found in vegetable oils, and its main component is monounsaturated oleic acid. Monounsaturated fats are neutral in relation to the body, and do not affect either the propensity to thrombosis or the level of cholesterol in the blood.Olive oil is great for cooking, as it can withstand quite high temperatures (in fact, up to 210 ° C), and at the same time retains a significant part of its valuable properties. It is advisable to buy unrefined first cold-pressed oil, and the darker the color, the better. Store it in a dark and cold place.
To get one liter of oil, you need 5 kg of black olives. The cold pressing method preserves most of all vitamins and mineral salts in the oil: copper, phosphorus, magnesium, calcium, potassium, copper, iron. Fun fact: The lipid balance in olive oil is almost the same as in breast milk.
Of all the oils, olive is the best absorbed, besides, it is great for constipation and liver failure. Another useful property is that it can neutralize the intoxication of the body after drinking alcohol. Recent studies have shown that olive oil increases the absorption of calcium. And this means that it is irreplaceable in the diet of children, at the age when their bone apparatus is being formed and developed.
Oleic acid is contained in olive oil (77%), rapeseed oil (55%), peanut oil (55%), grape seed oil (41%), soybean oil (30%), sunflower oil (25%), in wheatgrass oil (25%), in walnut oil (20%).
Polyunsaturated
They consist of two groups in which the active ingredient is the so-called basic fatty acid. Since the body cannot produce it on its own, this acid must be supplied with food.
Main sources: cereal sprouts (up to 50% fatty acids), corn, oatmeal, brown rice, and oils.
Linoleic acid (Omega-6) is found in: sunflower oil (57%), soybean oil (55%), grape seed oil (54%), walnut oil (54%), wheatgrass oil (53%) , in pumpkin (45%), sesame (41%), peanut (20%), rapeseed (20%), olive (7%).
Linolenic acid (Omega-3): in flaxseed (55%), in walnut oil (13%), rapeseed (8%), in wheatgrass oil (6%), soybean (6%), sesame (1 %), olive (0.8%). Omega-3 is also found in fish.
Flaxseed oil is very rich in omega-6 and omega-3 unsaturated fatty acids, which are essential for building cells. It softens the skin, helps the body fight allergies, protects the brain and nerve structures, and stimulates the production of hormones. It must not be heated or cooked with it. Linseed oil is added exclusively to a ready-made cooled dish: soups, cereals, salads, vegetables.
Fish and fish oil are the most valuable sources of omega-3 fatty acids. It is these acids that our body needs most of all. They are very useful for brain activity. However, the current ecology is such that it is advisable for a child to be given sea fish, and not pure fish oil. It is made from cod liver, and the liver tends to accumulate various toxins in high doses. In addition, when eating cod liver, there is a high probability of an overdose of vitamins A and D. For people who eat vegetarian food, flaxseed oil will be a good substitute for fish oil.
Food additives that are valuable sources of polyunsaturated fatty acids:
- Pollen.
- Sprouted wheat.
- Brewer's yeast.
- Evening primrose and borage oils (they can be found in capsules in pharmacies).
- Soy lecithins.
In addition to some oils
The table presents data on the critical temperatures of some oils (in degrees Celsius) at which they decompose and release carcinogenic toxic substances that primarily affect the liver.Light and heat sensitive oils
- Walnut oil.
- Pumpkin.
- Linseed.
| Oils | Mg per 100g butter |
| Wheatgrass | 300 |
| Walnuts | 170 |
| Soybean | 94 |
| Corn | 28 |
| Olive | 15 |
It is best not to eat coconut oil. It contains too many fatty acids. Nevertheless, many people, especially those living in the places where coconut oil is obtained, consider it literally a panacea for all diseases. It is one of the oldest types of oils produced by humans. It is obtained from compressed dried coconut fruits. On the other hand, the advantage of coconut oil is that the saturated fat it contains has a completely different structure than the saturated fat used for preparing fast food. That is why there is still debate about whether this oil is harmful or not.
Butter is, on the one hand, an excellent source of vitamins A and D, and on the other hand, cholesterol. But for young children, a small amount of butter will be beneficial, because when the body is actively growing, it needs saturated fats for the harmonious and complete development of the brain.
What you should definitely know about butter: it absolutely does not tolerate heating above 120 °. This means that you cannot fry food on it. On contact with the hot surface of the frying pan, the oil immediately begins to release carcinogens that affect the intestines and stomach.
Margarine is an intermediate between vegetable and butter. It was created as a substitute for butter. The composition of margarines may vary from manufacturer to manufacturer. Some are fortified with wheatgrass oil, while others contain only saturated fatty acids or are hydrogenated.
If you carry out a minimum of processing, that is, do not hydrogenate the margarine, then some vitamins are preserved in it. But it must be remembered that the hardness of a margarine depends on the amount of palm and coconut oils added to it. Therefore, margarine is not recommended for those with a tendency to cardiovascular diseases.
Paraffin oil is a petroleum derivative and should be avoided. With food use of paraffin oil, the absorption of fat-soluble vitamins worsens. Moreover, when the oil is removed from the intestines, it binds to the already dissolved vitamins and comes out together with them.
Functions of fats
Lipids in our body perform energy and plastic functions. Unsaturated fatty acids are essential because not all of them are synthesized in the body. They are the precursors of prostaglandins. Prostaglandins are hormones that maintain a liquid state of cellular lipids, and also prevent the development of atherosclerotic plaques, prevent cholesterol and other lipids from adhering to the walls of blood vessels.Phospholipids are the fundamental structures of most cell membranes. They are part of the white and gray matter of the nervous tissue.
Fats are by nature an excellent solvent. Those substances that do not dissolve in water dissolve well in fats. Most of the fat is stored in the cells of the adipose tissue, which are the fat depot. Depot can be up to 30% of body weight. The function of adipose tissue is to fix the neurovascular bundles and internal organs. Fat is a heat insulator that keeps you warm, particularly during childhood. Lipid metabolism is closely related to protein and carbohydrate metabolism. With an excessive intake of carbohydrates in the body, they can turn into fats. In unfavorable conditions for the body, during starvation, fats are converted back into carbohydrates.
The energetic function consists in the fact that lipids of all nutrients give the body the greatest amount of energy. It has been proven that the oxidation of 1 gram of fat releases 9.3 kilocalories of heat, which is two times more than the oxidation of 1 gram of proteins or carbohydrates. When 1 g of proteins and carbohydrates are oxidized, 4.1 kcal of heat is released.
Food fats
Triacylglycerols predominate among them. There are vegetable and animal fats, and vegetable fats are more complete, since they contain much more unsaturated acids. Along with food, a small amount of free fatty acids also enters the body. Normally, up to 40% of all calories consumed by our body are lipids.Absorption and digestion of fats
Digestion of fats is a process of enzymatic hydrolysis that takes place in the small intestine and duodenum under the influence of enzyme substances found in the juices of the pancreas and intestinal glands.For fats to be digested, the body must produce bile. It contains detergents (or bile acids) that emulsify lipids so that enzymes break them down better. The products that are formed as a result of digestive hydrolysis - fatty, bile acids and glycerin - are absorbed from the intestinal cavity into the cells of the mucous membrane. In these cells, the fat is resynthesized again and forms special particles called "chylomicrons", which are sent to the lymph and lymphatic vessels, and then through the lymph into the blood. At the same time, only a small part of the fatty acids formed in the process of hydrolysis, which have a relatively short carbon chain (in particular, these are the products of hydrolysis of dairy fats) are absorbed and enter the blood of the portal vein, and then into the liver.
The role of the liver in lipid metabolism
The liver is responsible for the processes of mobilization, processing and biosynthesis of lipids. Short-chain fatty acids in conjunction with bile acids come from the digestive tract through the portal vein with blood flow to the liver. These fatty acids are not involved in lipid synthesis processes and are oxidized with the assistance of the liver enzyme systems. In adults, they generally do not play an important role in metabolism. The only exceptions are children, in their diet the most fat in milk.Other lipids enter the hepatic artery as lipoproteins or chylomicrons. They are oxidized in the liver, as in other tissues. Most of the lipids, except for a few unsaturated ones, are synthesized again in the body. Those of them that are not synthesized must necessarily go inside along with food. The total process of fatty acid biosynthesis is called "lipogenesis", and it is the liver that participates most intensively in this process.
In the liver, enzymatic processes of transformation of phospholipids and cholesterol are carried out. The synthesis of phospholipids ensures the renewal of the structural units of its cell membranes in the liver.
Blood lipids
Blood lipids are called lipoproteins. They are associated with different protein fractions in the blood. Their own fractions during centrifugation are separated according to their relative density.The first fraction is called the "chylomicrons"; they are composed of a thin protein coat and fats. The second fraction is very low density lipoproteins. They contain a large amount of phospholipids. The third fraction is lipoproteins, which contain a lot of cholesterol. The fourth fraction is high-density lipoproteins, they contain the most phospholipids. The fifth fraction is lipoproteins with high density and low content.
The function of lipoproteins in the blood is to carry lipids. Chylomicrons are synthesized in intestinal mucous cells and carry fat, which is resynthesized from fat hydrolysis products. The fats of the chylomicrons enter, in particular, adipose tissue and the liver. Cells of all tissues of the body can use chylomicron fatty acids if they have the necessary enzymes.
Lipoproteins with a very low density carry only fats that are synthesized in the liver. These lipids are generally consumed by adipose tissue, although they can be used by other cells as well. Fatty acids of high-density lipoproteins are products of enzymatic breakdown of fat contained in adipose tissue. This faction has a kind of mobility. For example, during a hunger strike, up to 70% of all energy costs of the body are covered by fatty acids of this particular fraction. Phospholipids and cholesterol of high and low density lipoprotein fractions are a source of exchange with the corresponding components of cell membranes, with which these lipoproteins can interact.
Transformation of lipids in tissues
In tissues, lipids are cleaved under the influence of various lipases, and the formed fatty acids are attached to other formations: phospholipids, cholesterol esters, etc.; or they are oxidized to final products. Oxidation processes take place in several ways. One part of fatty acids, during oxidative processes in the liver, produces acetone. With a severe form of diabetes mellitus, with lipoid nephrosis and some other diseases, the amount of acetone bodies in the blood increases sharply.
Regulation of fat metabolism
Regulation of lipid metabolism is carried out by a rather complex neuro-humoral pathway, while the mechanisms of precisely humoral regulation prevail in it. If the functions of the gonads, pituitary gland, thyroid gland decrease, then the processes of fat biosynthesis are enhanced. The saddest thing is that not only lipid synthesis increases, but also their deposition in adipose tissue, and this leads to obesity.Insulin is a pancreatic hormone and is involved in the regulation of lipid metabolism. Since there is a crossover possibility of transforming carbohydrates into fats, and then fats into carbohydrates, with a deficiency of insulin, the processes of carbohydrate synthesis are intensified, which is accompanied by an acceleration of the processes of lipid breakdown, during which intermediate metabolic products are formed that are used for the biosynthesis of carbohydrates.
Phospholipids are similar in structure to triacylglycerols, only their molecules contain phosphorus-containing groups. Steroids are cholesterol derivatives and have a different structure. Lipids also include a large group of fat-soluble substances, which include vitamins A, D, K, E. Lipids are needed not only to create the shell of our body - they are necessary for hormones, for brain development, for blood vessels and nerves, for the heart. It is known that lipids make up 60% of the brain.
Disruption of the normal concentration of lipids in the blood
If an abnormally high lipid level is observed in the blood, then this pathological condition is called hyperlipemia. With hypothyroidism, nephrosis, diabetes and disorders, doctors are faced with a secondary form of hyperlipemia. In these diseases, there is a high content of cholesterol and triglycerides. Primary hyperlipemia is a rather rare hereditary pathology that contributes to the development of arteriosclerosis and coronary heart disease.
With hypoglycemia, fasting, after injections of growth hormone, adrenaline, the amount of free fatty acids in the body sharply increases and the mobilization of previously deposited fat begins. This form of the disease is called mobilization hyperlipemia.
With hypercholesterolemia in the blood serum, there is a high level of cholesterol and a moderate level of fatty acids. When interviewing the closest relatives in the anamnesis, cases of early atherosclerosis are necessarily identified. Hypercholesterolemia, even at an early age, can contribute to the development of myocardial infarction. As a rule, there are no external symptoms. If a disease is detected, treatment is carried out with diet therapy. Its essence consists in the substitution of saturated acids by unsaturated acids. Correct correction of the diet significantly reduces the likelihood of developing pathologies of the vascular system.
With dyslipidemia, the balance of various types of lipids is disturbed in the blood. In particular, the main lipids found in the blood are cholesterol and triglycerides in different ratios. It is the violation of the ratio that leads to the development of diseases.
High levels of low-density lipids in the blood, as well as low levels of high-density cholesterol, are serious risk factors for cardiovascular complications in patients with diagnosed type 2 diabetes mellitus. Abnormal lipoprotein levels in this case may be the result of improper glycemic control.
It is dyslipidemia that is considered the main cause of the development of atherosclerotic changes.
Factors influencing the development of dyslipidemia
The most significant causes of dyslipidemia are genetic disorders of lipid metabolism. They consist in mutations of genes responsible for the synthesis of apolipoproteins - constituent lipoproteins.The second important factor is a healthy / unhealthy lifestyle. Under unfavorable circumstances, in the absence of physical activity, with the use of alcohol, lipid metabolism is disrupted. Obesity is directly related to an increase in triglycerides, with a violation of cholesterol concentration.
Another factor in the development of dyslipidemia is psychoemotional stress, which, through neuroendocrine stimulation, contributes to disorders of lipid metabolism. By neuroendocrine stimulation is meant an increase in the activity of the autonomic nervous system.
The clinical classification of the types of dyslipidemia provides for their subdivision into the so-called primary and secondary. Among the primary ones, one can distinguish polygenic (acquired during life, but due to hereditary disposition), and monogenic (genetically determined family diseases).
The cause of the secondary form of the disease can be: alcohol abuse, insufficient kidney function, diabetes, cirrhosis, hyperthyroidism, medications that give side effects (antiretroviral drugs, progestins, estrogens, glucocorticosteroids).
Diagnostic methods used to diagnose "dyslipidemia" are to determine the parameters of lipoproteins (high and low density), total cholesterol, triglycerides. During the diurnal cycle, even in perfectly healthy people, fluctuations in cholesterol levels of the order of 10% are observed; and fluctuations in triglyceride levels - up to 25%. To determine these indicators, blood donated on an empty stomach is centrifuged.
Determination of the lipid profile is recommended every five years. At the same time, it is desirable to identify other potential risk factors for the development of cardiovascular pathologies (smoking, diabetes mellitus, a history of ischemia in the next of kin).
Atherosclerosis
The main factor in the appearance of ischemia is the formation of many small atherosclerotic plaques, gradually increasing in the lumens of the coronary arteries and narrowing the lumen of these vessels. In the early stages of the development of the disease, plaques do not impair blood flow, and the process does not manifest itself clinically. The gradual growth of the plaque and the simultaneous narrowing of the vessel duct can provoke the manifestation of signs of ischemia.
At first, they will begin to manifest themselves with intense physical exertion, when the myocardium requires more oxygen and this need cannot be provided by an increase in coronary blood flow.
The clinical manifestation of the ischemic state of the myocardium is a sudden attack of angina pectoris. It is accompanied by such phenomena as pain and a feeling of constriction behind the breastbone. The attack passes as soon as the load of an emotional or physical nature stops.
The main (but not the only main) cause of ischemia is considered by doctors to be lipid metabolism disorders, but in addition, significant factors are smoking, obesity, carbohydrate metabolism disorders and genetic predisposition. Cholesterol levels directly affect the occurrence of complications of diseases of the heart system.
Treatment for this disease is to normalize cholesterol levels. Correction of the diet alone is not enough for this. It is also necessary to deal with other risk factors for development: to reduce weight, increase physical activity, quit smoking. Correction of nutrition implies not only a decrease in the total calorie content of food, but also the replacement of animal fats with vegetable fats in the diet:
consumption of animal fats and a simultaneous increase in the consumption of vegetable fats, fiber. It must be remembered that a significant part of cholesterol in our body does not come with food, but is formed in the liver. Therefore, diet is not a panacea.
To lower cholesterol levels, medications are also used - nicotinic acid, estrogen, dextrothyroxine. Of these agents, nicotinic acid acts most effectively against ischemia, but its use is limited due to concomitant side effects. The same applies to other medications.
In the 80s of the last century, know-how - drugs from the statin group - began to be used in lipid-lowering therapy. Currently, there are 6 drugs available on the pharmaceutical market that belong to this group. Pravastatin and lovastatin are drugs based on the waste products of fungi. Rosuvastatin, atorvastatin, fluvastatin are synthetic drugs, and simvastatin is semisynthetic.
These agents help lower low-density lipoprotein levels and lower total cholesterol and, to a lesser extent, triglycerides. Several studies have also shown a reduction in overall mortality among ischemic patients.
Cardiosclerosis
This disease is a complication of atherosclerosis and consists in the replacement of myocardial connective tissue. The connective tissue is not elastic, unlike the myocardium, therefore, the elasticity of the entire organ, on which the inelastic "patch" has appeared, suffers, and the heart valves are deformed.Cardiosclerosis (or myocardiosclerosis) is a logical consequence of an untreated disease: myocarditis, atherosclerosis, rheumatism. The acute development of this disease occurs with myocardial infarction and coronary artery disease. When atherosclerotic plaques appear everywhere in the coronary arteries in the heart, then the blood supply to the myocardium suffers, it does not have enough oxygen, carried with the blood stream.
The acute form of ischemic disease is myocardial infarction. So, an improper lifestyle, unbalanced diet and smoking can become an implicit cause of a heart attack, and acute psycho-emotional stress, against the background of which a heart attack appears, is a visible, but far from the main reason.
In addition to the acute form, there is also a chronic one. It is manifested by regularly occurring attacks of angina pectoris (that is, chest pain). You can relieve pain during an attack with nitroglycerin.
The body is designed in such a way that it tries to decompensate any violation. Connective tissue scars prevent the heart from stretching and contracting elastically. Gradually, the heart adapts to the scars and simply increases in size, which leads to impaired blood circulation through the vessels, to impaired muscle contractile activity, and to the expansion of the cardiac cavities. All this together is the cause of the failure of the heart function.
Cardiosclerosis is complicated by a violation of the heart rhythm (extrasystole, arrhythmia), protrusion of a fragment of the heart wall (aneurysm). The danger of an aneurysm is that the slightest stress can cause it to rupture, which leads to instant death.
Diagnosis of the disease is carried out using an electrocardiogram and ultrasound of the heart.
Treatment consists in the following: identification and treatment of exactly the disease that was the main cause of the development of cardiosclerosis; adherence to bed rest if the disease has led to myocardial infarction (at rest, scarring and healing occurs without the formation of a dangerous aneurysm); normalization of the rhythm; stimulating metabolic processes in the heart muscle, limiting any stress; adherence to a properly balanced diet, in particular, reducing the amount of lipids in the diet.
The diet provides good anti-allergic and anti-inflammatory effects, and is also considered an excellent preventive measure for preventing heart disease.
The basic rule of nutrition is moderation in the amount of food. It is also helpful to lose those extra pounds that put stress on the heart. The selection of food products should be carried out in terms of their value as energy and plastic materials for the heart. It is imperative to exclude spicy, sweet, fatty, salty foods from food. The use of alcoholic beverages in patients with vascular disorders is contraindicated. Food should be fortified with minerals and vitamins. Fish, boiled meat, vegetables, fruits, dairy products should be the basis of the diet.
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