home Auditorium 7 What are peptide hormones? Peptide hormones, mimetics and analogues Peptide hormones composition structure properties

What are peptide hormones? Peptide hormones, mimetics and analogues Peptide hormones composition structure properties

No human body can exist without hormones. They accompany people everywhere, actively being developed at the moment when the need for them arises. A large number of different hormonal substances function in the human body. The lion's share of these hormones comes from peptides.

What are peptides and what is the basis of their action?

Peptide hormones are protein substances that are produced by various endocrine glands in the body. These glands include the following:

However, peptides are not only produced in specific glands; some of them are produced by adipose tissue, stomach cells, and some liver and kidney cells.

The mechanism of action of peptide hormones is typical for all active substances of this nature and does not depend on the place of production of the hormone itself. The points of application of activity and the final effect of the impact differ. All hormones act on target organs through communication with special receptors located on the cell membrane. Each receptor recognizes only “its” hormone, only the one that can influence it. In the cell, under the influence of the peptide bound to the receptor, intermediaries are formed in the form of various enzymes. These enzymes in the cell activate the necessary functions, and an effective response to the action of the peptide hormone occurs.

Why does a person need the pituitary gland, and what peptides are formed there?

The pituitary gland is an appendage of the brain that is located on the lower part of the brain. Consists of anterior and posterior lobes. It is the anterior lobe that consists of a large number of glandular cells. Below is a list of peptide hormones of the anterior pituitary gland.

The posterior lobe of the pituitary gland, the neurohypophysis, usually does not produce hormones. Peptides are transported there from the hypothalamus, and they are deposited here. The most important of the stored hormones are vasopressin and oxytocin. Vasopressin performs two main functions: regulating the constancy of water in the body and constricting blood vessels. Oxytocin optimizes the process of childbirth and participates in lactation, facilitating the easy release of milk from the mother's glands.

The pituitary gland is closely connected to the hypothalamus. Together with it, it forms the regulatory hypothalamic-pituitary system, which is involved in many functions of the body. The hypothalamus is not a gland. It is a cluster of cells in a small space in the diencephalon. However, the cells located in the hypothalamus are active producers of vital hormones of peptide structure.

Are there peptides in the hypothalamus?

All peptide hormones of the hypothalamus are three different groups of active substances. The largest group is releasing hormones. They have a stimulating effect on the active substances of the anterior pituitary gland. They are called liberins and, as their name suggests, influence the corresponding hormones in the pituitary gland. The main ones are the following:

corticoliberin;
Thyroliberin;
somatoliberin;
follyliberin;
luliberin.

Thanks to the effects of liberins, the production of pituitary hormones is enhanced at those moments when the human body needs it. However, the production of active components of the pituitary gland does not always need to be enhanced. In some situations, it is necessary, on the contrary, to inhibit pituitary hormones. For this purpose, there is a second group of hypothalamic hormones. These are statins that inhibit the activity of the active components of the pituitary gland corresponding to the name.

somatostatin;
prolactostatin;
melanostatin.

What do pancreatic peptide substances regulate?

Peptide hormones are not produced only in parts of the brain. Two important hormones, insulin and glucagon, are produced by the pancreas. The pancreas is an organ located in the abdominal cavity, in the epigastrium. It has internal secreting activity, aimed at producing digestive hormones, and external, which produces hormones of a peptide nature. The formation of these active components occurs in special areas of the gland - the islets of Langerhans.

Insulin is the most important peptide hormone in the body. It is involved in the metabolism of carbohydrate energy, helps improve the transport of carbohydrates into muscles and adipose tissue. However, the main effect is glycemic control - a decrease in blood sugar concentration. The antipode is the second peptide pancreatic hormone - glucagon. Its participation in energy metabolism is to raise the concentration of sugar in the blood when the body needs it.

Could peptides form somewhere else?

Peptide hormones also include parathyroid hormone, produced in the parathyroid glands. The function of this active component is aimed at regulating calcium metabolism in the body. It inhibits bone formation and is secreted when calcium levels in the blood decrease.

Several active peptide substances are produced in the thyroid gland. One of them is a complete antagonist of parathyroid hormone. Its name is calcitonin. It is involved in the exchange of calcium and phosphorus and stimulates the activity of bone tissue building cells.

Some hormones can affect the composition of the blood. They are called erythropoietins, which control the formation of red blood cells and the formation of hemoglobin in the blood, and thrombopoietins, which are involved in the process of platelet formation. These peptide hormones are produced by the liver and kidneys.

Conclusion

Thus, peptide hormones are involved in many biological processes in the body and play a critical role in controlling the functioning of most organs and systems. In many cases, they are irreplaceable, on which the very existence of a person depends.

Peptide hormones include oxytocin, vasopressin, gastrin, glucagon, insulin and others.

Oxytocin - a 9-membered peptide produced by the posterior lobe of the pituitary gland. Oxytocin already 20-30 s after intravenous administration in an amount of only 1 mcg stimulates the secretion of milk by the mammary glands. In addition, as labor approaches, the sensitivity of the uterine muscles to oxytocin, which contracts under its influence, increases. Therefore, this hormone contributes to the normal course of childbirth, and it is this substance that allows the mother in labor not to associate the pain during childbirth with the newborn, and allows her to forget the pain during childbirth. This hormone can be called hormone of care and love. It affects the psycho-emotional state of women. Immediately after birth, it is produced in large quantities to form a tender and caring relationship in the child-mother system.

Vasopressin similar in structure and functional activity to oxytocin. However, its action is mainly aimed at regulating water metabolism; it increases blood pressure. In the wild, animals that produce a lot of oxytocin and vasopressin, such as swans and voles, form stable pairs.

Gastrin - I7-membered peptide secreted by the gastric mucosa. It stimulates the secretion of gastric juice.

Insulin - a protein produced in pancreatic cells, it regulates carbohydrate metabolism, facilitating the penetration of glucose into the cell, reduces the activity of enzymes that break down glycogen in the liver. In addition to insulin, the pancreas produces two more hormones - glucagon (insulin antagonist) and lipocaine (regulator of lipid metabolism).

Mechanism of action of peptide hormones.

Peptide hormones do not penetrate into target cells; they interact with protein receptors located on the outside of the surface of the plasma membrane. The vast majority of peptide hormones act according to the so-called adenylate cyclase mechanism : the protein-hormone complex with the receptor activates the enzyme adenylate cyclase, which accelerates the formation of cyclic AMP (Fig. 14). C-AMP has the ability to activate special enzymes - protein kinases, which catalyze the phosphorylation reactions of various proteins with the participation of ATP. In this case, phosphoric acid residues are included in the protein molecules. The main result of this phosphorylation process is a change in the activity of the phosphorylated protein. In different types of cells, proteins with different functional activities undergo phosphorylation as a result of activation of the adenylate cyclase system. For example, these could be enzymes, nuclear proteins, membrane proteins. As a result of the phosphorylation reaction, proteins can become functionally active or inactive. Such processes will lead to changes in the rate of biochemical processes in the target cell.

Hormones – amino acid derivatives (other hormones)

To the group other hormones relate adrenalin And norepinephrine , produced by the adrenal medulla; thyroid hormones - thyroxine and triiodothyronine.

Adrenaline and norepinephrine are derivatives of the proteinogenic amino acid tyrosine

These hormones cause an increase in blood pressure (except for the vessels of the brain and lungs), increase cardiac activity, contraction of smooth muscles, activate glycogen phosphorylase, lipase, and promote relaxation of the muscles of the bronchi and intestines. These hormones act via the adenylate cyclase mechanism.

Thyroxine (tetraiodothyronine) and triiodothyronine They are also derivatives of tyrosine (Fig. 32), they affect the activity of many enzymes localized in mitochondria, regulate the processes of biological oxidation in the body, the metabolism of fats and water, and influence the development of the body as a whole. The thyroid gland is the main depot of iodine in the body. In whales, the iodine content in this gland reaches 1 g/kg. With hyperfunction of the thyroid gland, oxidative processes intensify, cardiac and mental activity is disrupted, general exhaustion of the body and bulging eyes (Graves' disease) are observed.

Fig.32. The structure of thyroid hormones

Peptide hormones, or protein-peptide hormones, are the general name for hormones that are proteins or peptides in structure. Peptide hormones in the body often function as triggers. They stimulate the production of other hormones, such as testosterone and corticosteroids. After using peptide hormones, anabolic processes in the body are significantly enhanced, muscle growth increases or the pain sensitivity threshold decreases.

Analogs of human peptide hormones include synthetic drugs or drugs obtained using modern genetic engineering technologies. These are gonadotropin, growth hormone, adrenocorticotropic hormone and erythropoietin.

Gonadotropic hormones are produced in the anterior lobe of the pituitary gland and stimulate the functions of the gonads. This produces effects similar to those of testosterone, i.e. increased muscle mass.

Growth hormone causes human skeletal growth to a certain limit and is used by some athletes to build muscle mass. Drugs containing somatotropin, as growth hormone is also called, cause a number of side effects. These may be anomalies in the size of the hands, face, internal organs, in particular the liver. Exogenous growth hormone causes joint diseases, the development of diabetes, and cardiovascular diseases.

Adrenocorticotropic hormone, or ACTH, increases corticosteroid levels and is used by athletes to repair injured tissue and muscles. With prolonged use of exogenous ACTH, muscle death may occur. In addition, the athlete has problems sleeping, increases blood pressure, develops diabetes, stomach ulcers and other side effects.

Erythropoietin increases the number of red blood cells - erythrocytes. This significantly improves performance in endurance sports by increasing the oxygen transport function of the blood. Therefore, in some sports, international federations are forced to introduce additional doping controls for the number of red blood cells. Erythropoietin affects the body's hematocrit, i.e. it increases blood viscosity. In turn, for the normal supply of oxygen to tissues, although this sounds paradoxical in relation to the action of a drug that stimulates erythropoiesis, the body is forced to turn on mechanisms for increasing blood pressure. Stressful cardiac activity in this case can cause myocardial infarction. Other dangerous effects of erythropoietin are associated with cerebral palsy and the possibility of blood clots in the lungs.

Peptides(Greek πεπτος - nutritious) - a family of substances whose molecules are built from α-amino acid residues linked into a chain by peptide (amide) bonds. These are natural or synthetic compounds containing tens, hundreds or thousands of monomer units - amino acids. To date, more than 1,500 types of peptides are known, their properties have been determined, and synthesis methods have been developed.

Properties of peptides
Peptides are constantly synthesized in all living organisms to regulate physiological processes. The properties of peptides depend mainly on their primary structure - the sequence of amino acids, as well as on the structure of the molecule and its configuration in space (secondary structure).

Meaning

Peptide hormones and neuropeptides, for example, regulate most processes in the human body, including taking part in cell regeneration processes. Peptides of immunological action protect the body from toxins that have entered it. For proper functioning of cells and tissues, an adequate amount of peptides is necessary. However, with age and pathology, a deficiency of peptides occurs, which significantly accelerates tissue wear, which leads to aging of the entire organism. Today, they have learned to solve the problem of peptide deficiency in the body. The cell's peptide pool is replenished with short peptides synthesized in the laboratory.

Peptide synthesis

The formation of peptides in the body occurs within a few minutes, while chemical synthesis in the laboratory is a rather lengthy process that can take several days, and the development of synthesis technology can take several years. However, despite this, there are quite strong arguments in favor of carrying out work on the synthesis of analogues of natural peptides. First, by chemical modification of peptides it is possible to confirm the primary structure hypothesis. The amino acid sequences of some hormones became known precisely through the synthesis of their analogues in the laboratory.

Secondly, synthetic peptides allow us to study in more detail the relationship between the structure of an amino acid sequence and its activity. To clarify the relationship between the specific structure of the peptide and its biological activity, a huge amount of work was carried out on the synthesis of more than one thousand analogues. As a result, it was possible to find out that replacing just one amino acid in the structure of a peptide can increase its biological activity several times or change its direction. And changing the length of the amino acid sequence helps determine the location of the active centers of the peptide and the site of receptor interaction.

Thirdly, thanks to the modification of the original amino acid sequence, it became possible to obtain pharmacological drugs. The creation of analogues of natural peptides makes it possible to identify more “effective” configurations of molecules that enhance the biological effect or make it last longer.

Fourthly, chemical synthesis of peptides is economically beneficial. Most therapeutic drugs would cost tens of times more if they were made from a natural product.

Often, active peptides are found in nature only in nanogram quantities. Plus, methods for purifying and isolating peptides from natural sources cannot completely separate the desired amino acid sequence from peptides of the opposite or different effect. And in the case of specific peptides synthesized by the human body, they can only be obtained through synthesis in laboratory conditions.

Peptide hormones

Peptide hormones- this is the largest and most diverse class of hormonal compounds, which are biologically active substances. Their formation occurs in specialized cells of glandular organs, after which the active compounds enter the circulatory system for transportation to target organs. Upon reaching the goal, hormones specifically affect certain cells, interacting with the corresponding receptor.

Neuropeptides are compounds synthesized in neurons that have signaling properties. The effects of neuropeptides on the central nervous system are very diverse. They act directly on the brain and control sleep, affect memory, behavior, the learning process, and have an analgesic effect.

Peptides of immunological action

The most studied peptides involved in the immune response are tuftsin, thymopotin II and thymosin α1. Their synthesis in the cells of the human body ensures the functioning of the immune system.

Peptide bioregulators

Based on the technology developed by St. Petersburg scientists, peptides were isolated from animal organs and tissues that have a tissue-specific effect and are capable of restoring metabolism in the cells of the tissues from which they are isolated to an optimal level. An important difference between these peptides is their regulatory effect: when the cell function is suppressed, they stimulate it, and when the function is increased, they reduce it to a normal level. This made it possible to create a new class of drugs - peptide bioregulators.

The first of them, the immunomodulator Thymalin, has been on the pharmaceutical market for more than 28 years and is used to restore the function of the immune system in diseases of various origins, including cancer. It was followed by epithalamin (a bioregulator of the neuroendocrine system), samprost (a drug for the treatment of prostate diseases), Cortexin (a drug for the treatment of a wide range of neurological diseases), and retinalamine (a drug for the treatment of degenerative diseases of the retina). Over 25 years of widespread use of peptide bioregulators, more than 15 million people have received them. At the same time, no contraindications to their use or side effects were identified.

Growth hormone stimulants

The main regulators of growth hormone secretion are peptide hormones of the hypothalamus (somatostatin and somatoliberin), which are secreted by the neurosecretory cells of the hypothalamus into the portal veins of the pituitary gland and act directly on somatotropes. However, the balance of these hormones and the secretion of somatotropin are influenced by many physiological factors. Scientists have proven that the level of growth hormone secretion can be increased by 3-5 times, without the use of hormonal agents.

Peptides are the most powerful stimulators of growth hormone, increasing the concentration by 7-15 times, while the cost of an equivalent course is several times lower:

Growth hormone and peptides in bodybuilding

Currently, peptides that are growth hormone stimulants are becoming more and more common on the market. The most popular peptides in bodybuilding:

From the Ghrelin group (GHRP): (create a pronounced peak in GH concentration immediately after administration, regardless of the time of day and the presence of somatostatin in the blood).

GHRP-6 and Hexarelin
GHRP-2
Ipamorelin

From the group Growth Hormone Releasing Hormone (GHRH): (introduction into the body causes a wave-like rise in concentration, which will be weak during hours when the natural secretion of GH is reduced due to somatostatin, and high during the natural rise in GH concentration (for example, at night). In other words, GHRH enhances the secretion of GH without disturbing the natural pulse-like curve.)

GRF (1-29) Sermorelin
CJC-1295

HGH Frag (176-191) - fragment of growth hormone (fat burner)

Benefits of Peptides

Many people have questions: why use new peptide substances if there is an artificial growth hormone? The answer is simple: peptide stimulants have several compelling advantages:

Peptides are much cheaper than growth hormone. The cost of a similar course will be several times lower.
Different mechanisms of action and half-lives allow manipulation of the concentration curve to achieve optimal anabolic response.
Different effects on hunger and metabolism allow one to give preference to one or another substance.
Currently, the production and distribution of peptides is not regulated by law, so they can be safely ordered online.
They are destroyed quickly and without a trace, so you don’t have to worry about doping control.

Peptides, as well as classic growth hormone, can be easily verified for authenticity. To do this, it is enough to take tests for the level of somatotropin in plasma after administration of the drug.

How to take peptides. Basic rules for taking peptides:

The injection site is the abdominal area 8cm from the navel;
The angle of inclination of the syringe during injection is 45 degrees;
Give the injection strictly on an empty stomach;
Do not eat for 40 minutes after the injection;
The break between injections should be at least 4 hours.

Rules for diluting peptides in sterile water for injection:

Dilute the peptide with sterile water for injection along the wall of the ampoule;
When diluting, avoid dropping a drop of water onto the peptide mass;
Do not mix different peptides in one ampoule;
Do not shake the peptide diluted in water;
Do not keep a mixture of peptides from different ampoules in one syringe for a long time;
Keep away from direct sunlight;
Store the prepared solution in the refrigerator at a temperature of 2-8 degrees;
The shelf life of the prepared solution is up to 7-10 days.

Use an insulin syringe for 100 insulin units U100 (orange cap, see picture);
Do not confuse insulin units with divisions;
Strictly follow the dosage and recommendations of the sports doctor;
Increase the amount of protein in the daily diet to 3g per 1 kg of weight;
Keep an injection diary so you don’t forget what to inject and when;
Do the injections in the same sequence (so as not to confuse the drugs and not inject the same thing twice);
There are places in the abdominal area where the injection is painless and vice versa;
Try to avoid injections into blood vessels;
After the injection, do not remove the syringe for 5-10 seconds to prevent the drug from leaking out.

Before starting the course you need to purchase

Insulin syringes U100 (1 milliliter). At the pharmacy 70-100 rubles;
Ampoules with sterile water for injection. At the pharmacy 30-50 rubles;
Syringes with a long needle for diluting peptides. At the pharmacy 5-10 rubles;
Cotton pads. At the pharmacy 30-50 rubles;
Alcohol or alcohol wipes. At the pharmacy 40-60 rubles.

Basic rules of sterility for injections

Carry out the injection with clean hands;
Wipe the neck of the peptide ampoule with alcohol before use;
Wipe the injection site with alcohol (can be neglected, since the risk of infection is too small if you use insulin syringes);
Avoid contact of the needle with non-sterile surfaces;
Prevent air from entering the syringe;
The syringe is used only 1 time (to save money, you can take the daily dose of 1 drug into a separate syringe).

Peptides. Possible side effects

Peptides have been used for quite a long time and no such side effects have been identified, however, some negative reactions of the body to the drug should be noted:

Strong headache;
Periodic feeling of weakness;
Increased pressure;
Reduced attention;
Blistering of the skin and itching at the injection site;
Hard oval lumps under the skin after injections (hematomas).

Polypeptide hormones, or simply peptide hormones are hormones consisting of amino acids secreted by the endocrine system and distributed to nerve endings through the blood circulation. The endocrine organs that secrete peptide hormones are the hypothalamus, pituitary gland, thyroid gland, adrenal glands, ovaries, pancreas, endocrine and adipose tissue. Organs that are not considered part of the endocrine system, such as the heart and gastrointestinal tract, can also secrete peptide hormones.

The process of producing these hormones is the same as the process of producing proteins. In the cell nucleus, deoxyribonucleic acid (DNA) is first converted into template ribonucleic acid (mRNA), after which the mRNA template is translated into chains of amino acids (peptide hormone precursors) in ribosomes. These amino acid chains, also called preprohormones, are then sent to the endoplasmic reticulum to remove the signal or leading sequences, they usually contain from 15 to 30 amino acids and are located on the N-terminal amino acid chain. Cleavage of signal sequences leads to the formation of prohormones. Prohormones are either packaged into secretory vesicles or broken down by enzymes called endopeptidase to form a mature hormone that is released into the blood.

Peptide hormones secreted by the hypothalamus are generally called releasing factors and include corticotropin-, gonadotropin-, somatotropin-, and thyrotropin-releasing hormones.

Hormones secreted by the anterior pituitary gland include melanocyte-stimulating hormone, follicle-stimulating hormone, luteinizing hormone, adrenocorticotropic hormone (ACTH), thyroid-stimulating hormone, and growth hormone or somatotropin. Peptide hormones secreted by the posterior pituitary gland include prolactin or mammotroph hormone, vasopressin or antidiuretic hormone, and oxytocin. Other peptide hormones include thyroxine, secreted by the thyroid gland, cortisol, produced by the adrenal glands, and insulin, produced by the pancreas.

Certain extracellular signals induce the secretion of polypeptide hormones. For example, when the homeostatic balance changes, they are released to restore balance. The endocrine system generally operates on the basis of negative and positive feedback reactions or feedback mechanisms. For example, the anterior pituitary gland secretes adrenocorticotropic hormone, which stimulates the secretion of cortisol from the adrenal cortex. When the pituitary gland detects that the level of cortisol in the blood is increasing, the production of adrenocorticotropic hormone decreases.

To stimulate an organ, the peptide hormone must have a receptor in that organ. Peptide hormone receptors are located in the cell membrane, except for thyroid hormone receptors, which are located in the cell nucleus. When a peptide hormone binds to its receptor, signal transduction occurs and a substance called a second messenger is released to activate specific proteins and to increase or inhibit the production of certain substances. Secondary messengers typically contain calcium, cyclic adenosine monophosphate (cAMP), inositol triphosphate, and diacylglycerol.