Diseases caused by a violation of the synthesis of the functioning of proteins. Humoral changes in epilepsy

It is known that proteins undergo hydrolysis under the influence of endo- and exopeptidases formed in the stomach, pancreas, and intestines. Endopeptidases (pepsin, trypsin and chymotrypsin) cause protein cleavage in its middle part to albumose and peptones. Exopeptidases (carbopeptidase, aminopeptidase and dipeptidase), which are formed in the pancreas and small intestine, ensure the cleavage of the terminal sections of protein molecules and their decay products to amino acids, the absorption of which occurs in the small intestine with the participation of ATP.

Violations of protein hydrolysis can be caused by many reasons: inflammation, tumors of the stomach, intestines, pancreas; resection of the stomach and intestines; general processes such as fever, overheating, hypothermia; with increased peristalsis due to disorders of neuroendocrine regulation. All of the above reasons lead to a deficiency of hydrolytic enzymes or an acceleration of peristalsis, when peptidases do not have time to ensure the breakdown of proteins.

Unsplit proteins enter the large intestine, where, under the influence of microflora, putrefaction processes begin, leading to the formation of active amines (cadaverine, tyramine, putrescine, histamine) and aromatic compounds such as indole, skatole, phenol, cresol. These toxic substances are neutralized in the liver by combining with sulfuric acid. Under conditions of a sharp increase in the processes of decay, intoxication of the body is possible.

Absorption disorders are caused not only by cleavage disorders, but also by ATP deficiency associated with inhibition of conjugation of respiration and oxidative phosphorylation and blockade of this process in the wall of the small intestine during hypoxia, poisoning with phloridzin, monoiodoacetate.

Violations of the breakdown and absorption of proteins, as well as insufficient intake of proteins in the body, lead to protein starvation, impaired protein synthesis, anemia, hypoproteinemia, a tendency to edema, and immunity deficiency. As a result of the activation of the hypothalamus-pituitary-adrenal cortex and the hypothalamic-pituitary-thyroid system, the formation of glucocorticoids and thyroxine increases, which stimulate tissue proteases and protein breakdown in the muscles, gastrointestinal tract, and lymphoid system. In this case, amino acids can serve as an energy substrate and, in addition, are intensively excreted from the body, ensuring the formation of a negative nitrogen balance. Protein mobilization is one of the causes of dystrophy, including in muscles, lymph nodes, and the gastrointestinal tract, which exacerbates the breakdown and absorption of proteins.

With the absorption of unsplit protein, allergization of the body is possible. So, artificial feeding of children often leads to allergization of the body in relation to cow's milk protein and other protein products. Causes, mechanisms and consequences of violations of the breakdown and absorption of proteins are presented in Scheme 8.

Scheme 8. Violations of hydrolysis and absorption of proteins
	Hydrolysis disorders	Malabsorption
The reasons	Inflammation, tumors, resections of the stomach and intestines, increased peristalsis (nervous influences, decreased acidity of the stomach, eating poor quality food)
Mechanisms	Deficiency of endopeptidases (pepsin, trypsin, chymotrypsin) and exopeptidases (carbo-, amino- and dipeptidases)	ATP deficiency (absorption of amino acids is an active process and occurs with the participation of ATP)
Effects	Protein starvation -> hypoproteinemia edema, anemia; impaired immunity -> susceptibility to infectious processes; diarrhea, disruption of hormone transport. Activation of protein catabolism -> atrophy of muscles, lymph nodes, gastrointestinal tract, followed by aggravation of violations of the processes of hydrolysis and absorption of not only proteins, vitamins, but also other substances; negative nitrogen balance. Absorption of unsplit protein -> allergization of the body. When unsplit proteins enter the large intestine, the processes of bacterial cleavage (decay) increase with the formation of amines (histamine, tyramine, cadaverine, putrescine) and aromatic toxic compounds (indole, phenol, cresol, skatole)

This type of pathological processes includes insufficiency of synthesis, increased protein breakdown, and disturbances in the conversion of amino acids in the body.

Violation of protein synthesis.
Biosynthesis of proteins occurs on ribosomes. With the participation of transfer RNA and ATP, a primary polypeptide is formed on ribosomes, in which the amino acid inclusion sequence is determined by DNA. The synthesis of albumins, fibrinogen, prothrombin, alpha and beta globulins occurs in the liver; gamma globulins are produced in the cells of the reticuloendothelial system. Protein synthesis disorders are observed during protein starvation (as a result of starvation or disruption of splitting and absorption), with liver damage (circulatory disorders, hypoxia, cirrhosis, toxic-infectious lesions, deficiency of anabolic hormones). An important reason is the hereditary damage to the B-system of immunity, in which the formation of gamma globulins in boys is blocked (hereditary agammaglobulinemia).
Lack of protein synthesis leads to hypoproteinemia, impaired immunity, dystrophic processes in cells, possibly slowing down blood clotting due to a decrease in fibrinogen and prothrombin.
The increase in protein synthesis is due to excessive production of insulin, androgens, somatotropin. So, with a pituitary tumor involving eosinophilic cells, an excess of somatotropin is formed, which leads to activation of protein synthesis and increased growth processes. If excessive formation of somatotropin occurs in an organism with incomplete growth, then the growth of the body and organs is enhanced, manifested in the form of gigantism and macrosomia. If an increase in somatotropin secretion occurs in adults, then an increase in protein synthesis leads to the growth of protruding parts of the body (hands, feet, nose, ears, superciliary arches, lower jaw, etc.). This phenomenon is called acromegaly (from the Greek acros - tip, megalos - large). With a tumor of the reticular zone of the adrenal cortex, a congenital defect in the formation of hydrocortisone, as well as a tumor of the testes, the formation of androgens is enhanced and protein synthesis is activated, which is manifested in an increase in muscle volume and early formation of secondary sexual characteristics. An increase in protein synthesis is the cause of a positive nitrogen balance.
An increase in the synthesis of immunoglobulins occurs during allergic and autoallergic processes.
In some cases, a perversion of protein synthesis and the formation of proteins that are not normally found in the blood are possible. This phenomenon is called paraproteinemia. Paraproteinemia is observed in multiple myeloma, Waldenström's disease, some gammopathy.
With rheumatism, severe inflammatory processes, myocardial infarction, hepatitis, a new, so-called C-reactive protein is synthesized. It is not an immunoglobulin, although its appearance is due to the body's reaction to the products of cell damage.

Increased protein breakdown.

With protein starvation, an isolated increase in the formation of thyroxine and glucocorticoids (hyperthyroidism, Itsenko-Cushing's syndrome and disease), tissue cathepsins and protein breakdown are activated, primarily in the cells of striated muscles, lymphoid nodes, and the gastrointestinal tract. The resulting amino acids are excreted in excess in the urine, which contributes to the formation of a negative nitrogen balance. Excessive production of thyroxine and glucocorticoids is also manifested in impaired immunity and increased susceptibility to infectious processes, dystrophy of various organs (striated muscles, heart, lymphoid nodes, gastrointestinal tract).

Observations show that in three weeks in the body of an adult, proteins are renewed by half through the use of amino acids from food, and due to decay and resynthesis. According to McMurray (1980), with nitrogen balance, 500 g of proteins are synthesized daily, that is, 5 times more than is supplied with food. This can be achieved through the reuse of amino acids, including those formed during the breakdown of proteins in the body.

The processes of enhancing the synthesis and breakdown of proteins and their consequences in the body are presented in Schemes 9 and 10.

Scheme 10. Violation of nitrogen balance
	positive nitrogen balance	Negative nitrogen balance
The reasons	An increase in synthesis and, as a result, a decrease in the excretion of nitrogen from the body (tumors of the pituitary gland, reticular zone of the adrenal cortex).	The predominance of protein breakdown in the body and, as a result, the release of nitrogen in a larger amount compared to intake.
Mechanisms	Increased production and secretion of hormones that provide protein synthesis (insulin, somatotropin, androgenic hormones).	An increase in the production of hormones that stimulate protein catabolism by activating tissue catheins (thyroxine, glucocorticoids).
Effects	Acceleration of growth processes, premature puberty.	Dystrophy, including the gastrointestinal tract, impaired immunity.

Violations of the transformation of amino acids.
During the intermediate exchange, amino acids undergo transamination, deamination, decarboxylation. Transamination is aimed at the formation of new amino acids by transferring an amino group to a keto acid. The acceptor of the amino groups of most amino acids is alpha-ketoglutaric acid, which is converted to glutamic acid. The latter can again donate an amino group. This process is controlled by transaminases, the coenzyme of which is pyridoxal phosphate, a derivative of vitamin B 6 (pyridoxine). Transaminases are found in the cytoplasm and mitochondria. The donor of amino groups is glutamic acid, which is located in the cytoplasm. From the cytoplasm, glutamic acid enters the mitochondria.
Inhibition of transamination reactions occurs during hypoxia, vitamin B6 deficiency, including suppression of intestinal microflora, which partially synthesizes vitamin B6, with sulfonamides, ftivazid, as well as with toxic-infectious liver lesions.
With severe cell damage with necrosis (heart attack, hepatitis, pancreatitis), transaminases from the cytoplasm enter the blood in large quantities. So, in acute hepatitis, according to McMurray (1980), the activity of glutamate-allanine transferase in the blood serum increases 100 times.
The main process leading to the destruction of amino acids (their degradation) is non-amination, in which, under the influence of amino oxidase enzymes, ammonia and keto acid are formed, which are further converted in the tricarboxylic acid cycle to CO 2 and H 2 0. Hypoxia, hypovitaminosis C, PP, B 2 , B 6 block the breakdown of amino acids along this pathway, which contributes to their increase in the blood (aminoacidemia) and excretion in the urine (aminoaciduria). Usually, when deamination is blocked, part of the amino acids undergoes decarboxylation with the formation of a number of biologically active amines - histamine, serotonin, gamma-aminobutyric acid, tyramine, DOPA, etc. Decarboxylation is inhibited in hyperthyroidism and excess glucocorticoids.

As a result of deamination of amino acids, ammonia is formed, which has a pronounced cytotoxic effect, especially for cells of the nervous system. A number of compensatory processes have been formed in the body that ensure the binding of ammonia. In the liver, urea is synthesized from ammonia, which is a relatively harmless product. In the cytoplasm of cells, ammonia binds with glutamic acid to form glutamine. This process is called amidation. In the kidneys, ammonia combines with a hydrogen ion and is excreted in the form of ammonium salts in the urine. This process, called ammoniogenesis, is also an important physiological mechanism aimed at maintaining acid-base balance.

Thus, as a result of deamination and synthetic processes in the liver, such end products of nitrogen metabolism as ammonia and urea are formed. During the transformation in the tricarboxylic acid cycle of the products of the intermediary metabolism of proteins - acetylcoenzyme-A, alpha-ketoglutarate, succinylcoenzyme-A, fumarate and oxaloacetate - ATP, water and CO 2 are formed.

The end products of nitrogen metabolism are excreted from the body in different ways: urea and ammonia - mainly with urine; water with urine, through the lungs and sweating; CO 2 - mainly through the lungs and in the form of salts with urine and sweat. These non-protein substances containing nitrogen make up the residual nitrogen. Normally, its content in the blood is 20-40 mg% (14.3-28.6 mmol / l).

The main phenomenon of violations of the formation and excretion of the end products of protein metabolism is an increase in non-protein blood nitrogen (hyperasotemia). Depending on the origin, hyperazotemia is divided into production (hepatic) and retention (renal).

Production hyperazotemia is caused by liver damage (inflammation, intoxication, cirrhosis, circulatory disorders), hypoproteinemia. In this case, the synthesis of urea is disturbed, and ammonia accumulates in the body, providing a cytotoxic effect.

Retention hyperazotemia occurs with kidney damage (inflammation, circulatory disorders, hypoxia), impaired urine outflow. This leads to retention and an increase in residual nitrogen in the blood. This process is combined with the activation of alternative pathways for the excretion of nitrogenous products (through the skin, gastrointestinal tract, lungs). With retention hyperazotemia, an increase in residual nitrogen occurs mainly due to the accumulation of urea.

Violations of the formation of urea and the release of nitrogenous products are accompanied by disorders of the water and electrolyte balance, dysfunction of the organs and systems of the body, especially the nervous system. Perhaps the development of hepatic or uremic coma.

The causes of hyperazotemia, mechanisms and changes in the body are presented in Scheme 11.

Scheme 11. Violations of the formation and excretion of the end products of protein metabolism
HYPERAZOTEMIA
	Hepatic (productive)	Renal (retention)
The reasons	Liver damage (intoxication, cirrhosis, circulatory disorders), protein starvation	Violation of the formation of urea in the liver
Mechanisms	Inflammation of the kidneys, circulatory disorders, urinary outflow disorders	Insufficient excretion of nitrogenous products in the urine
Changes in the body	Effects- Dysfunction of organs and systems, especially the nervous system. Perhaps the development of hepatic or uremic coma. Compensation mechanisms- Amidation in cells, ammoniogenesis in the kidneys, excretion of nitrogenous products in alternative ways (through the skin, mucous membranes, gastrointestinal tract)

Source: Ovsyannikov V.G. Pathological physiology, typical pathological processes. Tutorial. Ed. Rostov University, 1987. - 192 p.

Scientists have found that increasing the production of a protein that is involved in the mechanism of long-term memory formation prevents epileptic attacks. In the course of the study, scientists managed to significantly increase protein synthesis using genetic engineering. eEF2 in laboratory mice. The relationship between the action of this protein and epilepsy has not been previously known, which gives hope for the development of new possibilities in the treatment of the disease.

The study was conducted at the University of Haifa (Israel) together with scientists from Milan and a number of other European universities. Professor Kobi Rosenblum, scientific director of the study, says: "By changing the genetic code, we were able to prevent the development of epilepsy in mice that were supposed to be born with this disease, as well as cure mice that already suffered from this disease."

Epilepsy is a neurological disease in which there is a sudden and uncontrolled activity in the nerve cells of the cerebral cortex, which is expressed in epileptic seizures of varying frequency and power. The drugs used today for the treatment of epilepsy can eliminate or reduce the number of seizures in only a subset of patients. In some cases, they resort to minimally invasive neurosurgical operations, which give good results. However, they may not be suitable for all patients either.

Interestingly, initially Israeli scientists planned to conduct a study to study the mechanisms that affect the formation of long-term memory. The goal of the scientists was to study the molecular mechanisms that contribute to the formation of long-term memory and are located in the hypothalamus (a part of the brain). To do this, they focused on the study of protein eEF2, which takes part in the processes of memory formation and the formation of new cells of the nervous system. Using genetic engineering methods, scientists managed to achieve increased protein production, which led to a change in the activity of nerve cells responsible for the formation of epileptic seizures.

In order to test how the production of this protein affects the development of epileptic seizures, mice were divided into two groups. The first group had a gene mutation and, accordingly, intensively produced protein eEF2, and the second control group of mice was without any genetic changes. The mice of both groups were injected with a solution that causes epileptic seizures. This led to epileptic seizures in mice from the control group, and mice with the genetic mutation did not develop signs of epilepsy.

However, scientists did not stop there and decided to test the effect of the mutation in hereditary epilepsy. To do this, they crossed mice with a gene mutation eEF2 with mice that had a gene responsible for the development of epilepsy. According to the results of the experiment, mice with a protein mutation did not experience epileptic seizures. Throughout the study, the mice were exposed to various texts defining motor, cognitive, and behavioral functions. All of them remained normal in mice that had a mutation of this protein.

“The results of the study give us more understanding about the processes of excitation and inhibition in the hypothalamus, the violation of which is associated with various pathologies of the nervous system,” says Professor Rosenblum, “we continue research in this direction in order to better understand the cause of the development of epileptic seizures. This will allow us to create new methods of treating the disease in the future.”

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Epilepsy in inborn errors of metabolism in children

Authors: Nicole I. WOLFF, Thomas BAST, Department of Pediatric Neurology, University Children's Hospital, Heidelberg, Germany; Robert SURTES, Neurological Research Fellowship, Institute of Child Health, University College London, UK

Summary

Although congenital metabolic disorders are rare enough to be considered a cause of epilepsy, seizures are common symptoms of metabolic disorders. In some of these disorders, epilepsy responds to specific treatment with diet or supplements. However, in most cases, such treatment does not work, and it is necessary to prescribe conventional antiepileptic therapy, which is also often ineffective. Rarely, the types of seizures are specific for certain metabolic disorders, and they are usually not recorded on the EEG. In order to make a diagnosis, it is necessary to take into account other symptoms and syndromes, and in some cases additional methods of examination. We give an overview of the most important symptoms of epilepsy due to congenital disorders of metabolism, memory, intoxication and disorders of the neurotransmitter systems. We also consider vitamin-sensitive epilepsy and a variety of other metabolic disorders, possibly similar in pathogenesis, as well as the importance of their symptoms for diagnosis and treatment.

Keywords

congenital metabolic disorders, memory disorders, neurotransmitters, vitamin-sensitive epilepsy, epilepsy.

Seizures are a common symptom for a large number of metabolic disorders occurring in the neonatal period and in childhood. Sometimes attacks occur only until adequate treatment is prescribed, or they are the result of an acute decompensated metabolic disorder, such as, for example, hyperammonemia or hypoglycemia. In other cases, seizures are the main manifestation of the disease and can lead to drug-resistant epilepsy, as, for example, in one of the syndromes of creatinine deficiency and guanidine acetate methyltransferase (GAMT) deficiency. In some cases of metabolic disorders, epilepsy can be prevented by early initiation of individually tailored "metabolic" treatment, which has been adopted following screening of newborns with phenylketonuria (PKU) or biotinidase deficiency in some countries. For some disorders, such as celiac aciduria type 1 (GA 1), "metabolic" therapy should be given in conjunction with conventional antiepileptic drugs; however, for many metabolic disorders, antiepileptic drug monotherapy is the only means of leveling seizures.

Epilepsy in congenital metabolic disorders can be classified in different ways. One of the correct options is to use pathogenetic mechanisms for classification: seizures may be due to a lack of energy consumption, intoxication, memory impairment, damage to neurotransmitter systems with cases of excitation or lack of inhibition, or may be associated with malformations of cerebral vessels (Table 1). Other classifications take into account clinical manifestations with an emphasis on seizure semiotics, epileptic syndromes and their manifestations on the EEG (Table 2), or the age at which the onset of the disease occurred (Table 3). To order these types of epilepsy means to identify those that are and are not amenable to the same treatment as metabolic disorders (Table 4). In this review, we will focus on pathogenesis and its role in diagnosis and treatment.

Epilepsy due to congenital disorders of energy metabolism

Mitochondrial disorders

Mitochondrial disorders often co-occur with epilepsy, although there are few definitive data in this area, with only a few publications on the subject. In the neonatal period and childhood, epilepsy is detected in 20-60% of cases of all mitochondrial disorders. In the general subgroup, with Leig's syndrome, epilepsy is detected in half of all patients. In our experience, epilepsy is a common disease with early onset and severe psychomotor retardation, which is less common in milder disease, and in which there are predominantly white inclusions on MRI. All seizures are clinically manifested.

A decrease in the production of ATP, the main biochemical successor of the disturbed respiratory chain, may cause an unstable membrane potential and convulsive readiness of the nervous system, because about 40% of neurons require Na-K-ATPase in the process of ATP production and to maintain membrane potential. One of the mitochondrial DNA (mtDNA) mutations causes myoclonic epilepsy with intermittent red waves (MEKV), with damaged calcium metabolism leading to increased convulsive readiness. Another possible mechanism currently under discussion has shown the importance of mitochondrial glutamate in causing early myoclonic encephalopathy (EME), which may also be due to an imbalance of excitatory neurotransmitters. One of the first mitochondrial disorders to be described, MEPKV, is due to a mutation in the mitochondrial tRNA for lysine present in the second decade or later as progressive myoclonic epilepsy with typical EEG changes of high amplitude somatosensory potentials and photosensitivity. Clinically, patients have cortical myoclonuses, as well as other types of seizures. Another mitochondrial disorder caused by a mitochondrial tRNA mutation for leucine, mitochondrial encephalopathy with lactic acidosis and stroke-like episodes (MELIE), also often leads to seizures, especially during acute stroke-like episodes, when focal seizures occur in the involved areas of the cortex (Fig. 1) leading to focal epistatus. This pronounced epileptic activity is also responsible for the spread of damage that is noted in some acute episodes.

With the onset of mitochondrial encephalopathy in the neonatal period or in childhood, myoclonic seizures are frequent, sometimes with rare single clinical manifestations (eyelid tremor) and severe mental retardation. EEG patterns range from suppressive bursts to irregular polyspike wave paroxysms during myoclonus. However, other types of seizures may occur, such as tonic, tonic-clonic, partial, hypo- and hypermotor seizures, or infantile spasms. One study found that 8% of all children with infantile spasms had mitochondrial disorders. Epistatus has also been observed with or without seizures. Long-term partial epilepsy, such as focal epilepsy, is common in Alpers disease, some cases of which are due to a mutation in mitochondrial DNA polymerase-gamma caused by mitochondrial depletion. Alpers disease should be suspected in children with this symptom and should be differentiated from Ramussen's encephalitis.

Non-convulsive epistatus or the development of hypoarrhythmia can lead to progressive dementia, which may be mistaken for an unchanged and refractory progression of the underlying disease, but they must be treated.

Creatine metabolism disorders

Creatine metabolism disorders include three different defects: impaired transport of creatine to the brain due to a defect in the linked creatine transporter, impaired creatine synthesis due to defects in GAMT (guanidine acetate methyltransferase) and AGAT (arginine glycine amidine transferase). Only GAMT deficiency is consistently associated with epilepsy, which is resistant to conventional treatment (Fig. 2). Prescribing creatine supplements often results in improvement. However, in some patients, the reduction of the toxic constituents of guanidinoacetate through the restriction of arginine intake and supplements containing ornithine, has made it possible to achieve the ability to control epilepsy. In addition, preventive treatment makes it possible to prevent the occurrence of neurological symptoms. There are many types of seizures, they are diverse. Newborns are characterized by West's syndrome with atypical absences, astatic and generalized tonic-clonic seizures, followed by general generalization. Such findings may be normal even in adult patients, but in some patients an abnormal signal from the basal ganglia is detected. The diagnosis of GAMT deficiency may be questionable when biochemically detecting increased urinary excretion of guanidine constituents; all three disorders are allowed when proton magnetic resonance spectroscopy of the brain or SMPS reveals the absence of free creatine or creatine phosphate.

GLUT-1 deficiency

Violation of glucose transport to the brain through the blood is caused by a mutation in the dominant gene of glucose transporter 1 (GLUT-1). The mutation usually occurs de novo, although autosomal dominant inheritance has been described in some families. Clinical manifestations of drug-resistant epilepsy begin in the first year of life and are complemented by the development of microcephaly and intellectual impairment. Ataxia is a common finding, and movement disorders such as dystonia also occur. Symptoms may develop rapidly, the EEG may show increased generalized or localized epileptiform changes that regress after eating. Cerebral imaging is normal. This diagnosis should be suspected if a low blood glucose level is found (< 0,46). Диагноз должен быть подтвержден исследованием транспорта глюкозы через мембрану эритроцита (эритроциты переносят также транспортер глюкозы) и анализом генных мутаций. Лечение целесообразно и включает в себя кетогенную диету, так как кетоновые тела являются альтернативной энергетических субстратов для мозга. Различные антиконвульсанты, особенно фенобарбитал, хлоргидрат и диазепам, могут в дальнейшем снижать ГЛУТ-1 и не должны использоваться при этом заболевании.

hypoglycemia

Hypoglycemia is a common and easily correctable metabolic disorder leading to seizures and should therefore be excluded in all patients with seizures. Prolonged seizures caused by hypoglycemia can cause hippocampal sclerosis and subsequently parietal lobe epilepsy; in newborns, the lesion of the temporal lobe dominates. Hypoglycemia can also cause certain metabolic diseases, such as defects in gluconeogenesis, so additional testing is needed. Every child with hypoglycemia should be given tests for blood glucose, beta-hydroxybutyrate, amino acids, acylcarnitine, ammonium, insulin, growth hormone, cortisol, brain ketone bodies, and organic acids.

Dysfunction of the nervous system caused by impaired memory

Many memory disorders are associated with epilepsy and are difficult to treat. Epilepsy is the leading symptom of Tay-Sachs disease with myoclonus, atypical absence seizures, and motor seizures.

Sialidosis type 1 leads to the development of progressive myoclonic epilepsy, a characteristic symptom is the retinal symptom of "cherry pit". With various neuronal seroid lipofuscinoses (NSL, Batten's disease), epilepsy occurs in most cases. In infantile forms (NSL-1), seizures begin and end in the first year of life and manifest as myoclonic, atopic, and tonic-clonic seizures. An early deep depression is recorded on the EEG. The diagnosis is confirmed by rapidly progressive dementia and the development of a movement disorder complex almost immediately after the onset of epilepsy. MRI in NSL reveals atrophy of the cortex, cerebellum, and white matter and a secondary pathological signal from the white matter (Fig. 3). Electroretinograms are highly sparse, and evoked potentials disappear quickly. Milder variants are similar to late-onset juvenile forms of the disease.

Clinical manifestations of late infantile forms (LTS-2) usually occur in the second year of life. A transient slowdown in speech function develops, but this development of seizures has prompted further research. Seizures may be generalized, tonic-clonic, atonic, and myoclonic; children may have a clinic of myoclonic-astatic epilepsy. The EEG reveals spikes with slow photostimulation (Fig. 4). High-amplitude potentials with visually evoked and somatosensory responses are revealed. Seizures are often resistant to treatment. An early clinical diagnostic symptom is the presence of active myoclonus, which can be mistaken for cerebellar ataxia.

The diagnosis of HSL-1 and HSL-2 is currently based on the determination of the activity of enzymes such as palmiteyl protein thioesterase (HSL-1) or tripeptidyl peptidase (NSL-2) in blood drops or leukocytes or in gene mutation assays ( NSL-1, NSL-2, and in late infantile variants SLN-5, SLN-6, SLN-8). The juvenile form (NSL-3) also causes the development of epilepsy, although it does not develop immediately and is not one of the early clinical symptoms.

Toxic effects

Urea cycle disorder

During the early development of hyperammonemia, before deep coma occurs, seizures often develop, especially in newborns. With good metabolic control, epilepsy is a rare symptom in these disorders.

Amino acid metabolism disorders

With untreated phenylketonuria, epilepsy develops in about a quarter or half of all patients. West syndrome with hypsarrhythmia and infantile seizures is the most common syndrome in newborns, which completely regresses with symptomatic therapy. Seizures may be accompanied by maple syrup disease in the neonatal period; the EEG reveals a "ridge-like" rhythm, similar to the rhythm in the central regions of the brain. With the appointment of an adequate diet, epilepsy does not develop. In some rare disorders of amino acid metabolism, epilepsy can be one of the main symptoms.

Metabolic disorders of organic acids

Various organic aciduria can lead to seizures or episodes of acute decompensation. The most important are methylmalonic acidemia and propionic acidemia. With adequate treatment, seizures are rare and reflect persistent brain damage. In glutaric aciduria type 1, attacks may develop in an acute case, but they disappear after the start of adequate treatment. In 2-methyl-3-hydroxybutyrate-CoA dehydrogenase deficiency, which has recently been described as a congenital disorder of the acid responsible for brachiocephalic obesity and isoleucine metabolism disorder, severe epilepsy is common.

Purine and pyrimidine metabolism disorders

With a deficiency of adenyl succinate, whose de novo effects induce purine synthesis, epilepsy often develops in the first year of life or in the neonatal period. Patients additionally show severe psychomotor disorders and autism. The modified Bratton-Marshall test is used to test urine. There is no adequate treatment for this disease, so the prognosis in most cases is poor. Seizures also develop in half of all patients with dihydropyrimidine dehydrogenase deficiency.

Neurotransmitter system disorders

Nonketotic hyperglycemia

Typically, this disorder of inadequate glycine digestion manifests early in the neonatal period with lethargy, hypotension, hiccups (which is present before birth), ophthalmoplegia, and autonomic disturbances. With aggravation of coma, apnea and frequent focal myoclonic convulsive twitches develop. Over the next 5 months (usually more than 3), a severe, difficult-to-treat epilepsy with myoclonic seizures develops, in most cases including infantile spasms or partial motor seizures. The development of severe mental retardation and tetraplegia has also been proven. In the first days and weeks, the EEG shows normal background activity, but areas of epileptic acute waves (so-called depression flashes) appear, followed by high-amplitude slow activity and then hypsarrhythmia for 3 months if the newborn survives. Diagnosis is based on a high concentration of glycine in all body fluids and cerebrospinal fluid (> 0.08), which is confirmed by a reduced activity of the hepatic glycine breakdown system. An MRI may show a normal picture or agenesis or hypoplasia of the corpus callosum. Glycine is one of the major inhibitors of neurotransmitters in the brain and spinal cord. Excessive inhibition of the structures of the brain and spinal cord gives the appearance of the first symptoms in the clinic of the disease. However, glycine can also be a co-antagonist of the exotoxic NMDA glutamate receptor. Under physiological conditions, the coantagonist is not completely located on the NMDA receptor, and its binding is a prerequisite for the passage of the ion through the receptor. Excess glycine is hypothesized to saturate the coantagonist-binding site of the NMDA receptor, causing excessive excitation of neurotransmission and postsynaptic toxicity. The excitatory toxic effect of an overactive NMDA receptor is obviously the cause of epilepsy and, in part, of tetraplegia and mental retardation. Specific treatment is not advisable, although lowering glycine levels with sodium benzoate provides survival. Some patients have presented therapeutic trials of NMDA antagonists with some EEG findings and frequent seizures. Severe epilepsy in surviving patients is usually treated with conventional antiepileptic drugs. Valproic acid is not theoretically used as it inhibits the hepatic glycine breakdown system.

GABA metabolism disorders

GABA transaminase deficiency is a rather rare pathology, described in only 3 patients. Seizures are noted from birth. The level of GABA in CSF and plasma increases. Only 2 patients survived to adulthood. So far, there is no treatment regimen for this disease. Succinate semialdehyde dehydrogenase deficiency causes severe mental retardation. Nearly half of patients develop epilepsy and other neurological symptoms, mostly ataxia. A biochemical sign is the accumulation of 4-hydroxybutyrate in body fluids. The antiepileptic drug vagabatrin, which irreversibly inhibits GABA transaminase, is effective in many patients but may worsen the condition in some.

Malformations in the brain

Among peroxisomal disorders, severe Zellweger syndrome is characterized by malformations in the cerebral cortex. Polymicrogyria of the frontal and opercular regions is common, and pachygyria is also occasionally seen. Typical are congenital cysts in the caudothalamic nodes (Fig. 5). Epilepsy in Zellweger syndrome typically includes partial motor seizures that are treatable with standard antiepileptic drugs and indicate which area of the brain the malformation is present. Violation of O-glycosylation (Walker-Warburg syndrome, disease of the muscles of the eyes, brain, Fukuyama muscular dystrophy) leads to brain malformations, including lissencephaly (Fig. 6). Patients often have seizures that cannot be treated. The EEG shows abnormal beta activity.

Vitamin dependent epilepsy

Pyridoxine-dependent epilepsy and pyridox(am)inphosphate-oxygenase deficiency

The phenomenon of pyridoxine-dependent epilepsy has been known since 1954, but its molecular basis still had to be elucidated. A possible metabolic marker for this disease appears to have been plasma and CSF pipecolic acid, which increased before pyridoxine administration and decreased during treatment, although still not reaching normal levels. When studying genetics in some families, a chain was identified that includes chromosome 5q-31.

In the classification of pyridoxine-dependent epilepsy, typical, early onset, appearing in the first days of life, and atypical, late onset, manifesting itself by the age of 34, are distinguished. With early onset, there may be prenatal seizures occurring around 20 weeks' gestation. Often found (in 1/3 of cases) neonatal encephalopathy with increased anxiety, irritability and sensitivity to external stimuli. It may be accompanied by systemic involvement such as respiratory distress syndrome, nausea, abdominal disturbances, and metabolic acidosis. Many seizures begin in the first days of life and are not amenable to standard treatment. There may be structural brain disorders such as hypoplasia of the posterior corpus callosum, cerebral hypoplasia or hydrocephalus and other disorders such as hemorrhages or organic lesions of the white matter of the brain. A clear (up to minutes) reaction is determined in the form of a cessation of convulsive activity on the intravenous administration of 100 mg of pyridoxine. However, in 20% of newborns with pyridoxine-dependent epilepsy, the first dose of pyridoxine can cause depression: newborns become hypotonic and sleep for several hours, less often develop apnea, dysfunction of the cardiovascular system and isoelectric pattern on the EEG. Cerebral depression from the first dose of pyridoxine is more common when anticonvulsants are given to newborns.

On the contrary, with late onset pyridoxine-dependent epilepsy, encephalopathy and structural brain disorders do not develop. In children older than 3 years of age, seizures develop in any year of life. Often they develop in the context of febrile states and can transform into epistatus. Usually, antiepileptic drugs have a positive effect, but then it still becomes difficult to control these attacks. Pyridoxine in a daily dose of 100 mg per os ensures the cessation of convulsive activity for 2 days. With late-onset pyridoxine-dependent epilepsy, cerebral depression is not observed.

Currently, the only confirmation of the diagnosis of pyridoxine-dependent epilepsy is the cessation of seizures with the appointment of pyridoxine. The treatment is lifelong, and the daily dose of pyridoxine is 15-500 mg/kg. A constant symptom of pyridoxine-dependent epilepsy is learning difficulties, especially when learning languages. Discontinuation of treatment for several months or years causes the development of severe movement disorders, learning difficulties, and sensory disturbances. Every newborn with seizures, even with diagnosed perinatal asphyxia or sepsis, should be given pyridoxine.

Pyridox(am)inphosphate oxidase (PPO) catalyzes the conversion of pyridoxine phosphate to the active cofactor, pyridoxal phosphate. PFO deficiency causes neonatal seizures similar to those in early-onset pyridoxine-deficient epilepsy, but they are not treatable with pyridoxine, but are treated with pyridoxal phosphate at a daily dose of 10–50 mg/kg. Pyridoxal phosphate is a cofactor for various enzymes in the process of neurotransmitter synthesis and the breakdown of threonine and glycine. The biochemical marker of the disease is a decrease in the concentration of homovanillic acid and 5-hydroxyindole acetate (the breakdown product of dopamine and serotonin) and an increase in the concentration of 3-methoxytyrosine, glycine and threonine in the cerebrospinal fluid. The prognosis for the treatment of PFO deficiency has not been clarified. It is assumed that if left untreated, death occurs.

Folate-dependent seizures

This is a rare disease that is treated with folic acid. The molecular basis of this pathology is not clear. In all cases, an unidentified substance has been found in the cerebrospinal fluid so far. Newborns with folate-dependent epilepsy need trial folic acid if pyridoxine and pyridoxal phosphate fail.

Biotinidase and holocarboxylase synthase deficiency

Biotinidase is a cofactor for various carboxylases. Various metabolites accumulate in the urine and lactic acidosis often develops. With a deficiency of biotinidase, endogenous disorders of biotin metabolism develop. Epilepsy usually begins after 3–4 months of age, and infantile spasms, optic nerve atrophy, and hearing loss are common. The key to the diagnosis is the presence of alopecia and dermatitis. Attacks are usually stopped with the appointment of biotin at a dose of 5-20 mg / day. With holocarboxylase synthase deficiency, symptoms appear in the neonatal period. Seizures are observed only in 25-50% of patients. Biotin is effective at the dosage described above, although higher doses may be needed in some children.

Mixed Violations

Molybdenum cofactor and sulfite oxidase deficiency

These rare inborn errors of metabolism usually present in the neonatal period with encephalopathy, intractable seizures (often myoclonic), and lens displacement. MRI reveals cysts in the white matter of the brain and severe atrophy. The light screening test is a simple test using sulfite strips by dropping them into a sample of freshly collected urine. Fibroblasts are deficient in various enzymes. There are no treatment regimens for this pathology yet.

Menkes disease

Children with this recessive X defect always suffer from epilepsy, often with treatment-resistant infantile spasms. The diagnosis is confirmed by detecting low levels of copper and ceruloplasmin in the blood serum. The appointment of subcutaneous administration of copper histidinate can cause the cessation of seizures and stop the development of the disease.

Serine biosynthesis deficiency

Serine biosynthesis is impaired by a deficiency of two enzymes: 3-phosphate glycerate dehydrogenase and 3-phosphoserine phosphatase. Only one case of this pathology in the older age group has been described. In general, this is a rather rare disease. Children with this pathology are born with microcephaly. They develop seizures in the first year of life, more often it is West's syndrome. Seizures regress when prescribing supplements with serine per os. The key to a correct diagnosis is the detection of low levels of serine in the CSF. MRI reveals white matter atrophy and demyelination.

Congenital disorders of the glycosylation process (CNG)

In children with CNH type 1a (phosphomanmutase deficiency), epilepsy is rare, sometimes only in the form of acute stroke-like episodes. However, it is a common syndrome in type 1 CNH. Patients with other subtypes of type 1 CNH have been described in isolated cases of seizures. The clinical picture of seizures is variable depending on the subgroups. Treatment with standard antiepileptic drugs is carried out depending on the clinical picture of seizures. The diagnosis is made on the basis of isoelectric focusing of transferrin, which is included in the complex examination of children with unspecified epilepsy and mental retardation.

Congenital disorders of brain excitability

The concept of innate metabolic disorders is that this name implies a violation of the flow of substances through cell membranes. Neuronal excitability ends with the appearance of a membrane potential, which is maintained by an energy-dependent ion pump (Na-K-ATPase and K/Cl-transporter) and modulated by ion flow through protein channels. They are constantly closed and open (and thus allow the flow of ions across the membrane) in response to the action of ligands (such as neurotransmitters) or changes in membrane potential. Genetic defects in ion channels can be the cause of various epileptic syndromes. So, in some cases, such as a consequence of metabolic disorders, primary epilepsy may develop.

Genetic defects in the alpha-2 subunit of Na-K-ATPase 1 are one of the causes of familial migratory hemiplegia in children. In both cases, the likelihood of epilepsy is high. One family tried to find out if the familial spasms were an isolated disease or if they were associated with migratory hemiplegia. Genetic defects in the K / Cl transporter 3 are one of the causes of Andermann's syndrome (Charlevox disease, or agenesis of the corpus callosum in combination with peripheral neuropathy). With this disease, epilepsy also often develops.

Gated ion channel ligand disorders can also present with episyndrome. Genetic defects in neuronal nicotinic acetylcholine receptors (alpha-4 or beta-2 subunits) are one of the causes of autosomal dominant frontal epilepsy. Hereditary defects in the alpha-1 subunit of the GABA-A receptor are one of the causes of juvenile myoclonic epilepsy. Mutations in the gene code for the gamma-2 subunit of this receptor cause generalized epileptic febrile plus convulsions (GEFS+), severe myoclonic epilepsy of the newborn (SMEN), and absence seizures in children.

Other congenital channelopathies may also present with episyndromes. Defects in voltage-gated potassium channels are one of the causes of familial neonatal spasms. Disorders in voltage-gated chloride channels are one of the causes of juvenile absence seizures, juvenile myoclonic epilepsy, and generalized epilepsy with grand-mal seizures. Mutations in genes encoding various alpha subunits of voltage-gated brain potassium channels cause neonatal infantile spasms (type II alpha subunit), GEPS+, and TMEN. Since HEPS+ and TMEN are allelic disorders at two different loci, and both forms of epilepsy can occur in members of the same family, TMEN is considered the most severe phenotype on the HEPS+ epilepsy spectrum.

Conclusion

Congenital metabolic disorders are rarely manifested by epilepsy. However, the epileptic syndrome is often characteristic of other metabolic disorders. What kind of patients need a screening examination and in the presence of what metabolic disorders? The answer to this question is, of course, not simple. Metabolic disorders should be suspected if the epilepsy is resistant to standard treatment and if symptoms such as mental retardation and movement disorders are present. Occasionally, findings from patient examinations are characteristic of a particular metabolic disorder, such as the typical MRI pattern in mitochondrial disorders. If the first attack occurs in the adult age of the patient, the spectrum of metabolic disorders is narrower compared to that in children.

In children, certain diagnostic methods are used depending on age. In the neonatal period, pyridoxine- or pyridoxal phosphate should be given to everyone for diagnostic purposes, even if the attacks are due to sepsis or perinatal asphyxia. If seizures do not respond to standard antiepileptic drugs, folic acid should be tried. In the presence of congenital myoclonic encephalopathy, a congenital metabolic disorder is often assumed, although sometimes it is not possible to clarify its nature. Additional examinations are prescribed if deterioration is detected on the pre-meal EEG (GLUT-1 deficiency), movement disorders (creatine deficiency), changes in the skin and hair (Menkes disease and biotinidase deficiency), dysmorphological symptoms (Zelweger syndrome), other disorders (mitochondrial diseases). Patients with partial epilepsy (unless it is Ramussen syndrome) and antiepileptic drug-resistant epilepsy should be evaluated for mitochondrial disorders, especially mitochondrial DNA depletion, which is common in Alpers disease. Basic metabolic examinations should include tests such as serum and CSF glucose levels, blood and CSF lactate, ammonium and amino acid levels, and uric acid levels.

The diagnosis of a metabolic disorder in a patient with seizures makes it possible to choose the right treatment and thereby improve the patient's condition. Often, in spite of everything, antiepileptic drugs must also be prescribed. If it is not possible to prescribe a specific treatment, non-specific antiepileptic drugs are prescribed; in some variants of seizures, it is advisable to prescribe any of the antiepileptic drugs, except for valproic acid. It is not used in cases of mitochondrial disorders, disorders in the urea cycle, and is prescribed with caution in many other metabolic disorders. Clarification of the diagnosis helps not only to determine the tactics of treatment, but also makes it possible to tell the patient's family members what is most important in changing the patient's condition.

Bibliography

1. Applegarth D.A., Toone J.R. Glycine encephalopathy (nonketotic hyperglycinaemia): review and update // J Inherit Metab Dis, 2004; 27:417-22.

2. Barkovich A.J., Peck W.W. MR of Zellweger syndrome // AJNR, 1997; 18:1163-70.

3. Baxter P. Epidemiology of pyridoxine dependent and pyridoxine responsive seizures in the UK // Arch. Dis. Child., 1999; 81:431-3.

4. Baxter P., Griffiths P., Kelly T., Gardner-Medwin D. Pyridoxine-dependent seizures: demographic, clinical, MRI and psychometric features, and effect of dose on intelligence quotient // Dev Med Child Neurol., 1996; 38:998-1006.

5. Berkovic S.F., Heron S.E., Giordano L. et al. Benign familial neonatal-infantile seizures: characterization of a new sodium channelopathy // Ann Neurol, 2004; 55:550-7.

6. Brautigam C., Hyland K., Wevers R. et al. Clinical and laboratory findings in twins with neonatal epileptic encephalopathy mimicking aromatic L-amino acid decarboxylase deficiency // Neuropediatrics, 2002; 33:113-7.

7. Brini M., Pinton P., King M.P., Davidson M., Schon E.A., Rizzuto R. A calcium signaling defect in the pathogenesis of a mitochondrial DNA inherited oxidative phosphorylation deficiency // Nat Med 1999; 5:951-4.

8. Brockmann K., Wang D., Korenke C.G. et al. Autosomal dominant glut-1 deficiency syndrome and familial epilepsy // Ann Neurol, 2001; 50:476-85.

9. Castro M., Perez-Cerda C., Merinero B. et al. Screening for adenylosuccinate lyase deficiency: clinical, biochemical and molecular findings in four patients // Neuropediatrics, 2002; 33:186-9.

10. Charlier C., Singh N.A., Ryan S.G. et al. A pore mutation in a novel KQT-like potassium channel gene in an idiopathic epilepsy family // Nat Genet, 1998; 18:53-5.

11. Claes L., Ceulemans B., Audenaert D. et al. De novo SCN1A mutations are a major cause of severe myoclonic epilepsy of infancy // Hum Mutat, 2003; 21:615-21.

12. Claes L., Del Favero J., Ceulemans B., Lagae L., Van Broeckhoven C., De Jonghe P. De novo mutations in the sodium-channel gene SCN1A cause severe myoclonic epilepsy of infancy // Am J Hum Genet ., 2001; 68:1 322-7.

13. Clayton P.T., Surtees R.A., DeVile C., Hyland K., Heales S.J. Neonatal epileptic encephalopathy // Lancet, 2003; 361:1614.

14. Collins J.E., Nicholson N.S., Dalton N., Leonard J.V. Biotinidase deficiency: early neurological presentation // Dev Med Child Neurol 1994; 36:268-70.

15. Cooper J.D. Progress towards understanding the neurobiology of Batten disease or neuronal ceroid lipofuscinosis // Curr Opin Neurol, 2003; 16:121-8.

16. Cormier-Daire V., Dagoneau N., Nabbout R. et al. A gene for pyridoxine-dependent epilepsy maps to chromosome 5q31 // Am J Hum Genet, 2000; 67:991-3.

17. Cossette P., Liu L., Brisebois K. et al. Mutation of GABRA1 in an autosomal dominant form of juvenile myoclonic epilepsy // Nat Genet, 2002; 31:184-9.

18. Darin N., Oldfors A., Moslemi A.R., Holme E., Tulinius M. The incidence of mitochondrial encephalomyopathies in childhood: clinical features and morphological, biochemical, and DNA abnormalities // Ann Neurol, 2001; 49:377-83.

19. De Fusco M., Becchetti A., Patrignani A. et al. The nicotinic receptor beta 2 subunit is mutant in nocturnal frontal lobe epilepsy // Nat Genet, 2000; 26:275-6.

20. de Koning T.J., Klomp L.W. Serine-deficiency syndromes // Curr Opin Neurol, 2004; 17:197-204.

21. Dupre N., Howard H.C., Mathieu J. et al. Hereditary motor and sensory neuropathy with agenesis of the corpus callosutn // Ann Neurol., 2003; 54:9-18.

22. Escayg A., MacDonald B.T., Meisler M.H. et al. Mutations of SCN1A, encoding a neuronal sodium channel, in two families with GEFS+2 // Nat Genet, 2000; 24:343-5.

23. Ferrari G., Lamantea E., Donati A. et al. Infantile hepatocerebral syndromes associated with mutations in the mitochondrial DNA polymerase-gA // Brain, 2005; 128:723-31.

24. Coutieres F., Aicardi J. Atypical presentations of pyridoxine-dependent seizures: a treatable cause of intractable epilepsy in infants // Ann Neurol, 1985; 17:117-20.

25. Grewal P.K., Hewitt J.E. Glycosylation defects: a new mechanism for muscular dystrophy? // Hum Mol Genet 2003; 1 2: R259-R264.

26. Gropman A. Vigabatrin and newer interventions in succinic semialdehyde dehydrogenase deficiency // Ann Neurol, 2003; 54(Suppl 6):S66-S72.

27 Grunewald S., Imbach T., Huijben K. et al. Clinical and biochemical characteristics of congenital disorder of glycosylation type Ic, the first recognized endoplasmic reticulum defect in N-glycan synthesis // Ann Neurol, 2000; 47:776-81.

28. Hamosh A., Maher J.F., Bellus G.A., Rasmussen S.A., Johnston M.V. Long-term use of high-dose benzoate and dextromethorphan for the treatment of nonketotic hyperglycinemia // J Pediatr, 1998; 1 32:709-13.

29. Harkin L.A., Bowser D.N., Dibbens L.M. et al. Truncation of the GABA(A)-receptor γ2 subunit in a family with generalized epilepsy with febrile seizures plus // Am J Hum Genet., 2002; 70:530-6.

30. Haug K., Warnstedt M., Alekov A.K. et al. Mutations in CLCN2 encoding a voltage-gated chloride channel are associated with idiopathic generalized epilepsies // Nat Genet, 2003; 33:527-32.

31. Howard H.C., Mount D.B., Rochefort D. et al. The K-CI cotrans-porter KCC3 is mutant in a severe peripheral neuropathy associated with agenesis of the corpus callosum // Nat Genet, 2002; 32:384-92.

32. Hunt Jr. A.D., Stokes Jr. J., McCrory W.W., Stroud H.H. Pyridoxine dependency: report of a case of intractable convulsions in an infant controlled by pyridoxine // Pediatrics, 1954; 13:140-5.

33. Lizuka T., Sakai F., Kan S., Suzuki N. Slowly progressive spread of the stroke-like lesions in MELAS // Neurology, 2003; 61:1238-44.

34. Lizuka T., Sakai F., Suzuki N. et al. Neuronal hyperexcitability in stroke-like episodes of MELAS syndrome // Neurology, 2002; 59:816-24.

35. Item C.B., Stockler-lpsiroglu S., Stromberger C. et al. Arginine:gly-cine amidinotransferase deficiency: the third inborn error of creatine metabolism in humans // Am J Hum Genet, 2001; 69:1127-33.

36. Jaeken J. Genetic disorders of gamma-aminobutyric acid, glycine, and serine as causes of epilepsy // J Child Neurol, 2002; 17(Suppl 3): 3S84-3S87.

37. Jaeken J. Komrower Lecture. Congenital disorders of glycosylation (CDC): it's all in it! // J Inherit Metab Dis., 2003; 26: 99-118.

38. Jaeken J., Corbeel L., Casaer P., Carchon H., Eggermont E., Eeckels R. Dipropylacetate (valproate) and glycine metabolism // Lancet 1977; 2:617.

39. Klepper J., Fischbarg J., Vera J.C., Wang D., De Vivo D.C. GLUT1-deficiency: barbiturates potentiate haploinsufficiency in vitro // Pediatr. Res., 1999; 46:677-83.

40. Kunz W.S. The role of mitochondria in epileptogenesis // Curr. Opin. Neurol., 2002; 15:179-84.

41. Kuo M.F., Wang H.S. Pyridoxal phosphate-responsive epilepsy with resistance to pyridoxine // Pediatr Neurol., 2002; 26:146-7.

42. MacDermot K., Nelson W., Weinberg J.A., Schulman J.D. Valproate in nonketotic hyperglycinemia // Pediatrics, 1980; 65:624.

43. Mitchison H.M., Hofmann S.L., Becerra C.H. et al. Mutations in the palmitoyl-protein thioesterase gene (PPT; CLN1) causing juvenile neuronal ceroid lipofuscinosis with granular osmiophilic deposits // Hum Mol Genet, 1998; 7:291-7.

44. Molinari F., Raas-Rothschild A., Rio M. et al. Impaired mitochon-drial glutamate transport in autosomal recessive neonatal myoclonic epilepsy // Am J Hum Genet., 2004; 76:334-9.

45. Naviaux R.K., Nguyen K.V. POLC mutations associated with Alp-ers "syndrome and mitochondrial DNA depletion // Ann Neurol., 2004; 55: 706-12.

46. Pearl P.L., Gibson K.M., Acosta M.T. et al. Clinical spectrum of suc-cinic semialdehyde dehydrogenase deficiency // Neurology, 2003; 60:1413-7.

47. Plecko B., Stockler-lpsiroglu S., Paschke E., Erwa W., Struys E.A., Jakobs C. Pipecolic acid elevation in plasma and cerebrospinal fluid of two patients with pyridoxine-dependent epilepsy // Ann Neurol., 2000; 48:121-5.

48. Rahman S., Blok R.B., Dahl H.H. et al. Leigh syndrome: clinical features and biochemical and DNA abnormalities // Ann Neurol., 1996; 39:343-51.

49. Sadleir L.G., Connolly M.B., Applegarth D. et al. Spasms in children with definite and probable mitochondrial disease // Eur J Neurol., 2004; 11:103-10.

50. Salbert B.A., Pellock J.M., Wolf B. Characterization of seizures associated with biotinidase deficiency // Neurology, 1993; 43:1351-5.

51. Salomons G.S., van Dooren S.J., Verhoeven N.M. et al. X-linked creatine-transporter gene (SLC6A8) defect: a new creatine-deficiency syndrome // Am I Hum Genet, 2001; 68:1497-500.

52. Schulze A., Bachert P., Schlemmer H. et al. Lack of creatine in muscle and brain in an adult with GAMT deficiency // Ann Neurol, 2003; 53:248-51.

53. Schulze A., Ebinger F., Rating D., Mayatepek E. Improving treatment of guanidinoacetate methyltransferase deficiency: reduction of guanidinoacetic acid in body fluids by arginine restriction and ornithine supplementation // Mol Genet Metab, 2001; 74:413-9.

54. Seidner G., Alvarez M.G., Yeh J.l. et al. GLUT-1 deficiency syndrome caused by haploinsufficiency of the blood-brain barrier hexose carrier // Nat Genet, 1998; 18:188-91.

55. Sfaello I., Castelnau P., Blanc N., Ogier H., Evrard P., Arzimanoglou A. Infantile spasms and Menkes disease // Epileptic Disord, 2000; 2:227-30.

56. Singh N.A., Charlier C., Stauffer D. et al. A novel potassium channel gene, KCNQ2, is mutated in an inherited epilepsy of new-borns // Nat. Genet., 1998; 18:25-9.

57. Singh R., Andermann E., Whitehouse W.P. et al. Severe myoclonic epilepsy of infancy: extended spectrum of GEFS+? // Epilepsia, 2001; 42:837-44.

58. So N., Berkovic S., Andermann F., Kuzniecky R., Cendron D., Quesney L.F. Myoclonus epilepsy and ragged-red fibers (MERRF). 2. Electrophysiological studies and comparison with other progressive myoclonus epilepsies // Brain, 1989; 112:1261-76.

59. Steinlein O.K., Mulley J.C., Propping P. et al. A missense mutation in the neuronal nicotinic acetylcholine receptor alpha 4 subunit is associated with autosomal dominant nocturnal frontal lobe epilepsy // Nat Genet 1995; 11:201-3.

60. Stockier S., Isbrandt D., Hanefeld F., Schmidt B., von Figura K. Cuanidinoacetate methyltransferase deficiency: the first inborn error of creatine metabolism in man // Am J. Hum Genet, 1996; 58:914-22.

61. Swoboda K.J., Kanavakis E., Xaidara A. et al. Alternating hemiplegia of childhood or familial hemiplegia migraine? A novel ATP1A2 mutation // Ann Neurol, 2004; 55:884-7.

62. Takahashi Y., Suzuki Y., Kumazaki K. et al. epilepsy in peroxisomal. Diseases // Epilepsia, 1997; 38:182-8.

63. Tharp B.R. Unique EEC pattern (comb-like rhythm) in neonatal maple syrup urine disease // Pediatr. Neurol., 1992; 8:65-8.

64. Thomson A.M. Glycine is a coagonist at the NMDA receptor/channel complex // Prog Neurobiol., 1990; 35:53-74.

65. Torres O.A., Miller V.S., Buist N.M., Hyland K. Folinic acid-responsive neonatal seizures // J. Child Neurol, 1999; 14:529-32.

66. Van den Berghe G., Vincent M.F., Jaeken J. Inborn errors of the purine nucleotide cycle: adenylosuccinase deficiency // J. Inherit Metab Dis., 1997; 20:193-202.

67. Van Kuilenburg A.B., Vreken P., Abeling N.G. et al. Genotype and phenotype in patients with dihydropyrimidine dehydrogenase deficiency // Hum Genet., 1999; 104:1-9.

68. Vanmolkot K.R., Kors E.E., Hottenga J.J. et al. Novel mutations in the Na+, K+-ATPase pump gene ATP1A2 associated with familial hemiplegic migraine and benign familial infantile convulsions // Ann Neurol., 2003; 54:360-6.

69. Von Moers A., Brockmann K., Wang D. et al. EEC features of glut-1 deficiency syndrome // Epilepsia, 2002; 43:941-5.

70. Wallace R.H., Marini C., Petrou S. et al. MutantGABA(A) receptor γ2-subunit in childhood absence epilepsy and febrile seizures // Nat Genet 2001; 28:49-52.

71. Wolf N.l., Smeitink J.A. Mitochondrial disorders: a proposal for consensus diagnostic criteria in infants and children // Neurology, 2002; 59:1402-5.

72. Yanling Y., Qiang G., Zhixiang Z., Chunlan M., Lide W., Xiru W. A clinical investigation of 228 patients with phenylketonuria in mainland China // Southeast Asian J TropMed Public Health, 1999; 30(Suppl 2): 58-60.

73. Zschocke J., Ruiter J.P., Brand J. et al. Progressive infantile neuro-degeneration caused by 2-methyl-3-hydroxybutyryl-CoA dehydrogenase deficiency: a novel inborn error of branched-chain fatty acid and isoleucine metabolism // Pediatr. Res., 2000; 48:852-5.

74. Zupanc M.L., Legros B. Progressive myoclonic epilepsy // Cerebellum, 2004; 3:156-71.

Proteins are those chemical compounds whose activity leads to the formation of normal signs of a healthy body. The cessation of the synthesis of a particular protein or a change in its structure leads to the formation of pathological signs and the development of diseases. Let us name several diseases caused by a violation of the structure or intensity of protein synthesis.

Classical hemophilia is caused by the absence in the blood plasma of one of the proteins involved in blood clotting; sick people have increased bleeding
Sickle cell anemia is caused by a change in the primary structure of hemoglobin: in sick people, red blood cells are sickle-shaped, the number of red blood cells is reduced as a result of the accelerated process of their destruction; hemoglobin binds and carries less than normal amount of oxygen.
Gigantism is due to an increased amount of growth hormone; patients are overly tall.
Color blindness is caused by the absence of retinal cone pigment, which is involved in the formation of color perception; colorblind people cannot distinguish some colors.
Diabetes is associated with the so-called insufficiency of the hormone insulin, which can be due to various reasons: a decrease in the amount or a change in the structure of insulin secreted, a decrease in the amount or a change in the structure of the insulin receptor. In sick people, an increased amount of glucose in the blood is observed and pathological signs accompanying this develop.
Malignant cholesterolemia is caused by the absence of a normal receptor protein in the cytoplasmic membrane of cells that recognizes a transport protein that carries cholesterol molecules; in the body of patients, the cholesterol necessary for cells does not penetrate into the cells, but accumulates in large quantities in the blood, is deposited in the wall of blood vessels, which leads to their narrowing and the rapid development of hypertension at an early age.

Progressive xeroderma is caused by a malfunction of enzymes that normally carry out the restoration of DNA damaged by UV rays in skin cells; patients cannot be in the light, as in these conditions they develop numerous skin ulcers and inflammation.

8. Cystic fibrosis is caused by a change in the primary structure of the protein that forms a channel for SG ions in the outer plasma membrane; in patients, a large amount of mucus accumulates in the airways, which leads to the development of respiratory diseases.

2. Proteomics

The past 20th century was characterized by the emergence and rapid development of scientific disciplines that dissected a biological phenomenon into its constituent components and sought to explain the phenomena of life through a description of the properties of molecules, primarily biopolymers that make up living organisms. These sciences were biochemistry, biophysics, molecular biology, molecular genetics, virology, cell biology, bioorganic chemistry. Currently, scientific areas are being developed that are trying, based on the properties of the components, to give a complete picture of the entire biological phenomenon. This new, integrative strategy for understanding life requires a huge amount of additional information. The sciences of the new century - genomics, proteomics and bioinformatics have already begun to supply the source material for it.

Genomics is a biological discipline that studies the structure and mechanism

functioning of the genome in living systems. Genome- the totality of all genes and intergenic regions of any organism. Structural genomics studies the structure of genes and intergenic regions, which are of great importance in the regulation of gene activity. Functional genomics studies the functions of genes, the functions of their protein products. The subject of comparative genomics is the genomes of different organisms, the comparison of which will make it possible to understand the mechanisms of evolution of organisms, the unknown functions of genes. Genomics emerged in the early 1990s with the Human Genome Project. The objective of this project was to determine the sequence of all nucleotides in the human genome with an accuracy of 0.01%. By the end of 1999, the structure of the genome of many dozens of species of bacteria, yeast, roundworm, Drosophila, Arabidopsis plants was fully disclosed. In 2003, the human genome was deciphered. The human genome contains about 30,000 protein-coding genes. Only 42% of them know their molecular function. It turned out that only 2% of all hereditary diseases are associated with defects in genes and chromosomes; 98% of diseases are associated with dysregulation of a normal gene. Genes show their activity in synthesized proteins that perform various functions in the cell and organism.

In each specific cell at a certain point in time, a certain set of proteins functions - proteome. Proteomics- a science that studies the totality of proteins in cells under different physiological conditions and at different periods of development, as well as the functions of these proteins. There is a significant difference between genomics and proteomics - the genome is stable for a given species, while the proteome is individual not only for different cells of the same organism, but also for one cell, depending on its state (division, dormancy, differentiation, etc.). The multitude of proteomes characteristic of multicellular organisms makes their study extremely difficult. So far, the exact number of proteins in the human body is not even known. By some estimates there are hundreds of thousands; only a few thousand proteins have already been isolated, and even fewer have been studied in detail. The identification and characterization of proteins is an extremely technically complex process that requires a combination of biological and computer analysis methods. However, methods developed in recent years for detecting gene activity products—mRNA molecules and proteins—give hope for rapid progress in this area. Methods have already been created that allow one to simultaneously detect hundreds of cellular proteins simultaneously and compare protein sets in different cells and tissues in normal conditions and in various pathologies. One such method is to use biological chips, allowing to detect thousands of different substances at once in the object under study: nucleic acids and proteins. Great opportunities are opening up for practical medicine: having a proteomic map, a detailed atlas of the entire protein complex, doctors will finally have the long-awaited opportunity to treat the disease itself, and not the symptoms.

Genomics and proteomics operate with such vast amounts of information that there is an urgent need for bioinformatics- a science that collects, sorts, describes, analyzes and processes new information about genes and proteins. Using mathematical methods and computer technology, scientists build gene networks, model biochemical and other cellular processes. In 10-15 years, genomics and proteomics will reach such a level that it will be possible to study metabolome- a complex scheme of interactions of all proteins in a living cell. Experiments on cells and the body will be replaced by experiments with computer models. It will be possible to create and use individual medicines, develop individual preventive measures. New knowledge will have a particularly strong impact on developmental biology. It will become possible to obtain a holistic and at the same time sufficiently detailed idea of individual cells, starting from the egg and spermatozoon and up to differentiated cells. This will allow for the first time to follow on a quantitative basis the interaction of individual cells at different stages of embryogenesis, which has always been the cherished dream of scientists studying developmental biology. New horizons are opening up in solving such problems as carcinogenesis and aging. Advances in genomics, proteomics and bioinformatics will have a decisive influence on the theory of evolution and the systematics of organisms.
3. Protein engineering
The physical and chemical properties of natural proteins often do not satisfy the conditions in which these proteins will be used by humans. A change in its primary structure is required, which will ensure the formation of a protein with a different than before, spatial structure and new physicochemical properties, which make it possible to perform the functions inherent in a natural protein under other conditions. Is engaged in the construction of proteins protein engineering. Methods are used to obtain an altered protein. combinatorial chemistry and carry out site-directed mutagenesis- the introduction of specific changes in the coding DNA sequences, leading to certain changes in the amino acid sequences. To effectively design a protein with desired properties, it is necessary to know the patterns of formation of the spatial structure of the protein, on which its physicochemical properties and functions depend, that is, it is necessary to know how the primary structure of the protein, each of its amino acid residues affects the properties and functions of the protein. Unfortunately, for most proteins, the tertiary structure is unknown, it is not always known which amino acid or amino acid sequence needs to be changed in order to obtain a protein with the desired properties. Already, scientists using computer analysis can predict the properties of many proteins based on the sequence of their amino acid residues. Such an analysis will greatly simplify the procedure for creating the desired proteins. In the meantime, in order to obtain a modified protein with the desired properties, they go basically in a different way: they get several mutant genes and find the protein product of one of them that has the desired properties.

For site-directed mutagenesis, different experimental approaches are used. Having received a modified gene, it is built into a genetic construct and introduced into prokaryotic or eukaryotic cells that synthesize the protein encoded by this genetic construct. Potential opportunities of protein engineering are as follows.

By changing the binding strength of the converted substance - the substrate - with the enzyme, it is possible to increase the overall catalytic efficiency of the enzymatic reaction.
By increasing the stability of the protein in a wide range of temperatures and acidity of the medium, it can be used under conditions in which the original protein denatures and loses its activity.
By creating proteins that can function in anhydrous solvents, it is possible to carry out catalytic reactions under non-physiological conditions.

4. By changing the catalytic center of the enzyme, it is possible to increase its specificity and reduce the number of unwanted side reactions

5. By increasing the resistance of the protein to enzymes that break it down, it is possible to simplify the procedure for its purification.

b. By changing the protein so that it can function without its usual non-amino acid component (vitamin, metal atom, etc.), it can be used in some continuous technological processes.

7. By changing the structure of the regulatory regions of the enzyme, it is possible to reduce the degree of its inhibition by the product of the enzymatic reaction by the type of negative feedback and thereby increase the yield of the product.

8. You can create a hybrid protein that has the functions of two or more proteins. 9. It is possible to create a hybrid protein, one of the sections of which facilitates the release of the hybrid protein from the cultured cell or its extraction from the mixture.

Let's meet some advances in the genetic engineering of proteins.

1. By replacing several amino acid residues of lysozyme of bacteriophage T4 with cysteine, an enzyme with a large number of disulfide bonds was obtained, due to which this enzyme retained its activity at a higher temperature.

2. Replacing a cysteine residue with a serine residue in the human p-interferon molecule synthesized by Escherichia coli prevented the formation of intermolecular complexes, in which the antiviral activity of this drug decreased by about 10 times.

3. The replacement of the threonine residue in position 51 with a proline residue in the tyrosyl-tRNA synthetase enzyme molecule increased the catalytic activity of this enzyme tenfold: it began to quickly attach tyrosine to tRNA, which transfers this amino acid to the ribosome during translation.

4. Subtilisins - serine-rich enzymes that break down proteins. They are secreted by many bacteria and are widely used by humans for biodegradation. They strongly bind calcium atoms, which increase their stability. However, in industrial processes, there are chemical compounds that bind calcium, after which subtilisins lose their activity. By changing the gene, the scientists removed the amino acids involved in calcium binding from the enzyme and replaced one amino acid with another in order to increase the stability of subtilisin. The modified enzyme proved to be stable and functionally active under conditions close to industrial ones.

5. It was shown that it is possible to create an enzyme that functions like restriction enzymes that cleave DNA in strictly defined places. Scientists have created a hybrid protein, one fragment of which recognizes a certain sequence of nucleotide residues in a DNA molecule, and the other cleaves DNA in this area.

6. Tissue plasminogen activator - an enzyme that is used in the clinic to dissolve blood clots. Unfortunately, it is rapidly cleared from the circulatory system and must be administered repeatedly or in large doses, resulting in side effects. By introducing three directed mutations into the gene of this enzyme, a long-lived enzyme was obtained with an increased affinity for degradable fibrin and with the same fibrinolytic activity as the original enzyme.

7. By replacing one amino acid in the insulin molecule, scientists have ensured that when this hormone is administered subcutaneously to diabetic patients, the change in the concentration of this hormone in the blood was close to the physiological one that occurs after eating.

8. There are three classes of interferons with antiviral and anticancer activity, but showing different specificity. It was tempting to create a hybrid interferon with the properties of three types of interferons. Hybrid genes have been created that include fragments of natural interferon genes of several types. Some of these genes, being integrated into bacterial cells, ensured the synthesis of hybrid interferons with greater anticancer activity than that of the parent molecules.

9. Natural human growth hormone binds not only to the receptor of this hormone, but also to the receptor of another hormone - prolactin. In order to avoid undesirable side effects during the treatment, the scientists decided to eliminate the possibility of attaching growth hormone to the prolactin receptor. They achieved this by replacing some of the amino acids in the primary structure of growth hormone through genetic engineering.

10. While developing drugs against HIV infection, scientists obtained a hybrid protein, one fragment of which provided specific binding of this protein only to virus-affected lymphocytes, another fragment penetrated the hybrid protein into the affected cell, and another fragment disrupted protein synthesis in the affected cell, which led to her death.

Thus, we were convinced that by changing specific parts of the protein molecule, it is possible to impart new properties to already existing proteins and create unique enzymes.

Proteins are the main target for medicines. About 500 drug targets are now known. In the coming years, their number will increase to 10,000, which will allow the creation of new, more effective and safe drugs. Recently, fundamentally new approaches to the search for drugs have been developed: not single proteins, but their complexes, protein-protein interactions, and protein folding are considered as targets.