Cytochrome P450 (isoenzymes CYP2C19 and CYP3A4). The role of the cytochrome p450 family in the pathogenesis and treatment of NAFLD Cytochrome p450 characteristics and biological role

Cytochrome P450(CYP450) is a large group of enzymes responsible for the metabolism of foreign organic compounds and drugs. Enzymes of the cytochrome P450 family carry out oxidative biotransformation of drugs and a number of other endogenous bioorganic substances and, thus, perform a detoxification function. Cytochromes are involved in the metabolism of many classes of drugs, such as proton pump inhibitors, antihistamines, retroviral protease inhibitors, benzodiazepines, calcium channel blockers and others.

Cytochrome P450 is a protein complex with a covalently bound heme (metalloprotein), which ensures the addition of oxygen. Heme, in turn, is a complex of protoporphyrin IX and a divalent iron atom. The number 450 indicates that the reduced heme associated with CO has a maximum light absorption at a wavelength of 450 nm.

Cytochromes P-450 are involved not only in the metabolism of drugs, but also in the conversion of hemoglobin into bilirubin, the synthesis of steroids, etc. All isoforms of cytochrome P-450 are grouped into the families CYP1, CYP2, CYP3. Within the families, subfamilies A, B, C, D, E are distinguished. Within the subfamilies, isoforms are designated by serial number. For example, CYP2C19 is the name of the 19th in order cytochrome of the “C” subfamily, family “2”. In total, there are about 250 different types of cytochrome P-450, of which approximately 50 are found in the human body and only six of them (CYP1A2, CYP2C9, CYP2C19, CYP2D6, CYP2E1, CYP3A4) are relevant to drug metabolism.

The activity of cytochromes P-450 is influenced by many factors - smoking, alcohol, age, genetics, nutrition, disease. These factors are responsible for the formation of individual characteristics of the work of P-450 enzymes and determine the effects of drug interactions in a particular patient.

Importance of cytochromes P450 for gastroenterology

The recently increased interest of gastroenterologists in the cytochrome P450 isoforms CYP2C19 and CYP3A4 is due to their role in the metabolism of benzimidazole derivatives, which include all drugs from the ATC group A02BC “Proton pump inhibitors” (omeprazole, panthorazole, lansoprazole, rabeprazole and esomeprazole) . It is clinically significant that the CYP2C19 gene is polymorphic, and the magnitude of the therapeutic effect of various PPIs largely depends on the state of this gene in the patient.

Among PPIs, lansoprazole exhibits the greatest inhibitory effect on CYP2C19, followed by omeprazole and esomeprazole to a lesser extent. The effect of rabeprazole is even lower, but its thioester, formed during non-enzymatic metabolism, has a significant inhibitory effect on the activity of CYP2C19. Pantoprazole has the least effect on CYP2C19. Pantoprazole has the greatest inhibitory effect on CYP3A4 in vitro, followed by (as the effect decreases) omeprazole, esomeprazole, rabeprazole and lansoprazole. For patients receiving multiple medications, pantoprazole is preferable among PPIs (Bordin D.S.).

Metabolism of five proton pump inhibitors.
Darker arrows indicate more significant metabolic pathways.
Figure taken from the article Marelli S., Pace F.

With the active participation of CYP3A4, the metabolism of domperidone, cisapride and a large number of other drugs occurs.

A number of gastroenterological drugs inhibit cytochrome CYP3A4, thereby affecting the pharmacokinetics of drugs taken together.

Drug interaction problem

In modern clinical practice, the combined use of drugs is widespread, which is associated with the presence of several diseases in the patient or the insufficient effectiveness of monotherapy. With combination therapy, drug interactions are possible. Approximately 56% of patients under 65 years of age and 73% of patients over 65 years of age are taking more than one medication. Taking two medications leads to their interaction in 6% of patients. Prescribing 5 (or 10) drugs increases the interaction rate by up to 50 (or 100)%.

Potentially dangerous drug combinations are a serious clinical problem. There is evidence that from 17 to 23% of drug combinations prescribed by doctors are potentially dangerous. In the United States alone, 48 thousand patients die per year due to unintended drug interactions. The FDA has deregistered several drugs (including the prokinetic drug cisapride) due to their potentially dangerous interactions with other drugs, including fatalities.

The main mechanisms of drug interactions are associated with changes in their pharmacokinetics or pharmacodynamics. The most significant, according to modern concepts, are changes in pharmacokinetics during drug metabolism with the participation of cytochromes P-450.

An example of a dangerous interaction is the recently discovered interaction between PPIs and clopidogrel, which is widely used in the treatment of patients with coronary heart disease. To reduce the risk of gastrointestinal complications, patients receiving acetylsalicylic acid in combination with clopidogrel are prescribed a PPI. Since the bioactivation of clopidogrel occurs with the participation of CYP2C19, taking PPIs metabolized by this cytochrome may reduce the activation and antiplatelet effect of clopidogrel. In May 2009, at the Society for Cardiovascular Angiography and Interventions (SCAI) conference, data were presented showing that concomitant use of clopidogrel and PPIs significantly increases the risk of myocardial infarction, stroke, unstable angina, the need for repeat coronary interventions and coronary death (Bordin D .WITH.).

Cytochrome CYP2C19

The cytochrome P450 isoform CYP2C19 (S-mephenytoin hydroxylase) catalyzes the reactions of 5-hydroxylation of the pyridine ring and 5"-demethylation of the benzimidazole ring. In the human body, CYP2C19 is located in hepatocytes.

All types of CYP2C19 gene mutations can be divided into three groups:

Without mutations (homozygotes), they are also fast metabolizers of PPIs.
Having a mutation in one allele (heterozygotes), an intermediate type of metabolism.
Having mutations in both alleles, they are also slow metabolizers of PPIs.

The prevalence of CYP2C19 genotypes, type of metabolism and the effect of PPIs in the treatment of acid-related diseases are given in the table:

CYP2C19 genotype	Prevalence (Tkach S.M. et al., 2006)			Metabolism type	PPI half-life, T½, hour (Lapina T.L.)	Acid inhibitory effect of PPIs
CYP2C19 genotype	Prevalence (Tkach S.M. et al., 2006)	Caucasian	Mongoloid race	Metabolism type	PPI half-life, T½, hour (Lapina T.L.)	Acid inhibitory effect of PPIs
No mutations (homozygotes)	90% Caucasian population	50,6 %	34,0 %	Fast	1	Short
Mutation in the 1st alley (heterozygotes)	10% Caucasian population	40,5 %	47,6 %	Intermediate	-	Average
Mutation in both alleys	20-30% Asian population	3,3 %	18,4 %	Slow	2–10	High

Slow metabolizers are distinguished from fast and intermediate metabolizers by a twofold higher concentration of PPI in the blood plasma and half-life. Polymorphism of the gene encoding the 2C19 isoform determines different rates of PPI metabolism in patients. In connection with the above, the selection of PPIs is recommended to be carried out under supervision daily pH-metry(Khavkin A.I., Zhikhareva N.S., Drozdovskaya N.V.).

CYP2C19 actively metabolizes the following drugs: tricyclic antidepressants (amitriptyline, clomipramine, imipramine), antidepressant - selective serotonin reuptake inhibitor citalopram, antidepressant - MAO inhibitor moclobemide, anticonvulsants and antiepileptic drugs (diazepam, primidone, phenytoin, phenobarbital, nordazepam), proton pump inhibitors s (omeprazole, panthorazole, lansoprazole, rabeprazole and esomeprazole), the antimalarial drug proguanil, the NSAIDs diclofenac and indomethacin, as well as: warfarin, gliclazide, clopidogrel, propranolol, cyclophosphamide, nelfinavir, progesterone, teniposide, tetrahydrocannabinol, carisoprodol, voriconazole and others
strong CYP2C19 inhibitors: moclobemide, fluvoxamine, chloramphenicol (chloramphenicol)
nonspecific inhibitors of CYP2C19: PPI omeprazole and lansoprazole, H2-blocker cimetidine, NSAID indomethacin, as well as fluoxetine, felbamate, ketoconazole, modafinil, oxcarbazepine, probenecid, ticlopidine, topiramate
CYP2C19 inducers: rifampicin, artemisinin, carbamazepine, norethisterone, prednisone, St. John's wort.

The influence of different CYP2C19 genotypes on the effectiveness of Helicobacter pylori eradication

Patients with the genotype of “fast” metabolizers have a rapid metabolism of proton pump inhibitors, therefore, the antisecretory effect of taking the latter is less pronounced in them than in individuals with the phenotypes of “intermediate” and “slow” metabolizers. Differences in antisecretory effect may determine lower eradication rates Helicobacter pylori in “fast” metabolizers. Thus, there is a higher effectiveness of eradication therapy in patients with genotypes of “slow” (88.9%) and “intermediate” (82.7%) metabolizers compared to “fast” metabolizers (see figure).

The influence of different CYP2C19 genotypes on the effectiveness of Helicobacter pylori eradication.
BM – “fast” metabolizers, PM – “intermediate” metabolizers, MM – “slow” metabolizers (Maev I.V. et al.)

Due to the fact that molecular genetic studies are inaccessible to a practicing physician, “fast” metabolizers can be suspected based on the persistence of abdominal pain syndrome on the 3-4th day from the start of taking PPIs, as well as taking into account the slow endoscopic dynamics during epithelization of erosions and scarring ulcerative defects in the patient. In turn, the insufficiency of the antisecretory effect of therapy with PPIs can be verified by the method of 24-hour intragastric pH-metry (Maev I.V. et al.).

Cytochrome CYP3A4

The CYP3A4 enzyme catalyzes the sulfoxidation reaction, leading to the formation of a sulfonic group. CYP3A4 is one of the most important cytochromes for pharmaceuticals, since it biotransforms, at least partially, about 60% of oxidized drugs. Although the activity of CYP3A4 varies widely, it is not subject to genetic polymorphism. The location of CYP3A4 on the apical membranes of small intestinal enterocytes and hepatocytes facilitates drug metabolism prior to the drug entering the systemic circulation, which is known as the “first pass effect.”

A genetic defect in CYP3A4 may be the cause of the development of secondary long QT interval syndrome when taking cisapride and, as a consequence, the development of cardiac dysrhythmia (Khavkin A.I. et al.).

CYP3A4 is the main enzyme in the metabolism of the following drugs: immunosuppressants (cyclosporine, sirolimus, tacrolimus), drugs used in chemotherapy (anastrozole, cyclophosphamide, docetaxel, erlotinib, tyrphostin, etoposide, ifosfamide, paclitaxel, tamoxifen, teniposide, vinblastine, vindesine, gefitinib) , antifungals (clotrimazole, ketoconazole, itraconazole),

Importance of cytochromes P450 for gastroenterology

Metabolism of five proton pump inhibitors.
Darker arrows indicate more significant metabolic pathways.
Figure taken from the article Marelli S., Pace F.

With the active participation of CYP3A4, the metabolism of domperidone, cisapride and a large number of other drugs occurs.

A number of gastroenterological drugs inhibit cytochrome CYP3A4, thereby affecting the pharmacokinetics of drugs taken together.

Drug interaction problem

Cytochrome CYP2C19

All types of CYP2C19 gene mutations can be divided into three groups:

Without mutations (homozygotes), they are also fast metabolizers of PPIs.
Having a mutation in one allele (heterozygotes), an intermediate type of metabolism.
Having mutations in both alleles, they are also slow metabolizers of PPIs.

The prevalence of CYP2C19 genotypes, type of metabolism and the effect of PPIs in the treatment of acid-related diseases are given in the table:

CYP2C19 genotype	Prevalence (Tkach S.M. et al., 2006)			Metabolism type	PPI half-life, T½, hour (Lapina T.L.)	Acid inhibitory effect of PPIs
CYP2C19 genotype	Prevalence (Tkach S.M. et al., 2006)	Caucasian	Mongoloid race	Metabolism type	PPI half-life, T½, hour (Lapina T.L.)	Acid inhibitory effect of PPIs
No mutations (homozygotes)	90% Caucasian population	50,6 %	34,0 %	Fast	1	Short
Mutation in the 1st alley (heterozygotes)	10% Caucasian population	40,5 %	47,6 %	Intermediate	-	Average
Mutation in both alleys	20-30% Asian population	3,3 %	18,4 %	Slow	2–10	High

CYP2C19 actively metabolizes the following drugs: tricyclic antidepressants (amitriptyline, clomipramine, imipramine), antidepressant - selective serotonin reuptake inhibitor citalopram, antidepressant - MAO inhibitor moclobemide, anticonvulsants and antiepileptic drugs (diazepam, primidone, phenytoin, phenobarbital, nordazepam), proton pump inhibitors s (omeprazole, panthorazole, lansoprazole, rabeprazole and esomeprazole), the antimalarial drug proguanil, the NSAIDs diclofenac and indomethacin, as well as: warfarin, gliclazide, clopidogrel, propranolol, cyclophosphamide, nelfinavir, progesterone, teniposide, tetrahydrocannabinol, carisoprodol, voriconazole and others
strong CYP2C19 inhibitors: moclobemide, fluvoxamine, chloramphenicol (chloramphenicol)
nonspecific inhibitors of CYP2C19: PPI omeprazole and lansoprazole, H2-blocker cimetidine, NSAID indomethacin, as well as fluoxetine, felbamate, ketoconazole, modafinil, oxcarbazepine, probenecid, ticlopidine, topiramate
CYP2C19 inducers: rifampicin, artemisinin, carbamazepine, norethisterone, prednisone, St. John's wort.

The influence of different CYP2C19 genotypes on the effectiveness of Helicobacter pylori eradication

Cytochrome CYP3A4

CYP3A4 is the main enzyme in the metabolism of the following drugs: immunosuppressants (cyclosporine, sirolimus, tacrolimus), drugs used in chemotherapy (anastrozole, cyclophosphamide, docetaxel, erlotinib, tyrphostin, etoposide, ifosfamide, paclitaxel, tamoxifen, teniposide, vinblastine, vindesine, gefitinib) , antifungals (clotrimazole, ketoconazole, itraconazole),

Cytochrome P450 family 2 subfamily C polypeptide 9 (CYP2C9). Detection of the A1075C (Ile359Leu) mutation

Gene name -CYP2C9

Localization of the gene on the chromosome– 10q23.33

*1/*1
*1/*3
*3/*3

Occurrence in the population

Allele CYP2C9*3 occurs in Europeans with a frequency of 6%.

Association of marker with drug metabolism

It is being studied to determine the physiological effectiveness of the use of drugs: oral anticoagulants from the coumarin class (warfarin), sulfonylurea derivatives, non-narcotic analgesics (tenoxicam, flurbiprofen, lornoxicam, piroxicam), losartan and irbesartan (angiotensin II receptor blockers).

General information about the study

The drug most commonly used to prevent and treat thromboembolic complications is warfarin (Coumadin). It is prescribed for long-term use in a series of cases associated with increased blood clotting, as well as in the postoperative period in order to prevent the formation of blood clots due to surgery. It is often practiced to prescribe the drug to people who have suffered strokes or myocardial infarction.

To achieve the effect of drugs, their bioactivation in the body (transformation into an active form) in liver cells (hepatocytes) by the cytochrome P450 (CYP) enzyme system is necessary. The genes encoding these enzymes are polymorphic, and alleles encoding the formation of enzymes with reduced or absent function are common.

The activity of cytochromes, in addition to the structural features of the genes encoding them, is influenced by factors such as age, body weight, lifestyle, bad habits, diet, concomitant diseases, and medications. These factors are responsible for the formation of individual characteristics of the work of P450 enzymes and determine the nature of the metabolism of most drugs. The main enzyme for the biotransformation of indirect anticoagulants is the cytochrome P450 isoenzyme CYP2C9.

Gene CYP2C9 localized on chromosome 10 in region 10q23.33. There are gene variants (alleles) CYP2C9, encoding the formation of an enzyme with reduced or absent function. The gene variant carrying a point substitution of adenine for cytosine at position 1075 (A1075C) leads to a decrease in the metabolic activity of the enzyme and is designated CYP2C9*3. A single nucleotide substitution results in a substitution of the amino acid isoleucine for leucine (Ile359Leu) in the CYP2C9 enzyme. Thus, an enzyme with an altered function is synthesized, the activity of which is less than 5% of the activity of the enzyme *1. The major (unchanged) variant of the gene is designated as CYP2C9*1.

The most common genotype causes normal warfarin metabolism and is designated CYP2C9 *1/*1.

Genetic marker CYP2C9*3(genotypes *3/*3 and *3/*1) is associated with a change in the functional activity of the cytochrome P450 enzyme, which reduces the rate of elimination of warfarin from the body. The presence of the *3 allele in a patient leads to a significant decrease in the activity of the cytochrome isoenzyme, which increases the anticoagulation effect of the drugs up to 7 times and can cause the development of complications such as extensive internal bleeding and episodes of excessive hypocoagulation.

Polunina T.E.

Oksana Mikhailovna Drapkina

– We continue our program. Our lectures and discussions on gynecology are ending, we have completely entered into the regulations, so we will try not to leave them. Professor Tatyana Evgenievna Polunina opens the section of gastroenterology. Lectures “The role of the cytochrome P450 family in the pathogenesis and treatment of non-alcoholic fatty liver disease.”

Tatyana Evgenievna Polunina, professor, doctor of medical sciences:

– Cytochromes P450 (CYP 450) is the name of a large family of universal enzymes in the human body. Cytochromes P450 play an important role in the oxidation of numerous compounds, such as endogenous compounds (steroids, bile acids, fatty acids, prostaglandins, leukotrienes, biogenic amines), as well as exogenous compounds (drugs, industrial pollution products, pesticides, carcinogens and mutagens), the latter are called xenobiotics.

In this slide you can see where the cytochromes P450 are located. They are located in the hepatocyte, in the cytosol. The endoplasmic reticulum is the basis for the location. And, in particular, the lipid membrane, which contains a bilayer of phospholipids, has several connected structures on it. This is a cytochrome, which includes iron protein, nicotinamide adenine dinucleotide and oxidoreductase, which is included in the complex of metabolism of drugs and the above presented xenobiotics.

The most common representatives of this group that clinicians turn to are cytochromes P452 AC, P450 2D, P450 2E1, P450 3A4. These enzymes catalyze a wide range of metabolic reactions and one cytochrome can metabolize several drugs that have different chemical structures. The same drug has different effects in cytochrome P450 and in different organs. And, in particular, the most important cytochrome that we pay attention to is cytochrome P450 2E - the most important isoenzyme of cytochrome P450, it breaks down low-density lipoproteins.

Currently, not only phenotyping methods have been developed that are based on the substrate specificity of certain cytochrome P450 isoenzymes, but also the activity of a particular enzyme and metabolism is determined by the pharmacokinetics of the marker substrate and changes in the concentrations of the unchanged substance and its metabolite. But the determination of cytochrome P450 isoenzymes by identifying the genes for the corresponding isoenzymes is carried out using a polymerase chain reaction. This is called cytochrome P450 isoenzyme genotyping.

On this slide we see that in the hepatocyte, the place where the endoplasmic reticulum, cytochromes P450, of which there are more than 50, and drugs that are broken down in a certain cytochrome are located; in some cases it combines with the cytochrome and forms a vesicle that damages the hepatocyte, causing at the same time stress and cytokines; leads to activation of the tumor necrotic factor and, in particular, is a trigger factor for the launch of caspases, which manifests itself with catalytic processes.

Non-alcoholic fatty liver disease, which was subsequently identified as a nosological entity, began to be called non-alcoholic fatty liver disease (NAFLD) since 1980, after discovering changes in the liver of non-alcoholic patients that were similar to those seen in alcohol-induced damage.

The natural history of non-alcoholic fatty liver disease includes steatosis as an initial stage, which, without progressing, can be asymptomatic, and steatohepatitis, which is accompanied by terrible vegetative manifestations, cytolysis syndrome and dyspeptic manifestations. With the development of fibrosis, a rather serious problem arises - liver cirrhosis, and subsequently portal hypertension and carcinoma develop.

I would like to draw your attention to the fact that back in 1894, Kiernan proposed a certain liver architecture, which consists of a beam structure. On the periphery of the beams, which consist of polygonal hepatocytes, there is a triad: bile duct, portal vein and artery. This slide represents a normal healthy liver and fatty infiltration of hepatocytes. Liver steatosis, which is one of the first phases of development of non-alcoholic fatty liver disease, is presented in morphological form in this diagram.

The next option for the development of the inflammatory process, which leads to fibrous tissue spreading throughout the liver, we see steatohepatitis and subsequently cirrhosis of the liver with the development of portal hypertension. Most often, this is micronodular cirrhosis of the liver, which is already quite clearly established in the stages of development of non-alcoholic fatty liver disease, it is accompanied by portal hypertension, varicose veins of the esophagus, stomach, complications that are typical for cirrhosis of the liver, and death.

With non-alcoholic steatohepatitis, the most common developments are those that are most often associated as concomitant diseases: diabetes mellitus, obesity. In patients, non-alcoholic steatohepatitis develops up to 75%, and if diabetes mellitus and obesity are combined, then 90% of patients have non-alcoholic fatty liver disease.

The liver is undoubtedly the main target organ affected by metabolic syndrome. Insulin resistance is a key feature that is the basis for intrahepatocyte lipid accumulation, fatty liver, non-alcoholic steatohepatitis and liver cirrhosis.

I would like to draw attention to the fact that metabolic syndrome includes not only impaired glucose tolerance, but also dyslipidemia, abdominal-visceral obesity, insulin resistance and hyperinsulinemia, arterial hypertension, early atherosclerosis, impaired hemostasis, hyperuricemia, hyperandrogenism. I would like to say that non-alcoholic fatty liver disease, steatosis, is part of the metabolic syndrome and is currently a quintet that used to be called the “deadly quartet”.

The risk factors presented on this slide sometimes vary from country to country, with US positions and European positions differing slightly. But, nevertheless, waist circumference, levels of triglycerides, lipoproteins, blood pressure, in particular 130/85, glucose levels are indicators that must be monitored in a patient with metabolic syndrome.

Diseases associated with lipid metabolism are: non-alcoholic fatty liver disease, type 2 diabetes mellitus, coronary liver disease, hypertension.

In the pathogenesis scheme, insulin resistance of adipose tissue is of particular importance. An increase in lipogenesis, that is, an increase in the level of fatty acids, an increase in the synthesis of triglycerides and lipotoxicity lead to the development of insulin resistance, and this leads to metabolic dysfunction, stress of the endoplasmic reticulum, in which the metabolism of fatty acids and in particular lipoproteins also occurs, and to the activation of inflammation . These are Kupffer cells and stellate cells, which further lead not only to the fact that the level of very low density lipids increases, but undoubtedly this leads to the development of steatohepatitis with fibrosis, and we get the activity of a process that moves towards cirrhosis of the liver.

At the hepatocyte level, fatty acids undergo esterification into triglycerides and are exported as low-density lipoproteins, a situation in the normal hepatocyte that is associated with oxidation in mitochondria, peroxisomes and microsomes.

Undoubtedly, in the mechanism of insulin resistance, which is presented here, a key role belongs to the tumor necrosis factor, free radicals, leptin, fatty acids and increased lipolysis, which leads to the absorption of fatty acids, to a violation of β-oxidation of fatty acids in mitochondria and also to the accumulation of fatty acids in hepatocyte.

Induction of cytochromes P450 4A11 and P450 2E1 leads to lipid peroxidation, which undoubtedly leads to the activation of factors associated with the accumulation of triglycerides. Hyperinsulinemia is a key factor that leads to insulin resistance. It also leads to an increase in glycolysis, fatty acid synthesis and triglyceride accumulation in hepatocytes.

The next slide shows the mechanism of interaction between microsomal oxidation and mitochondrial β-oxidation. Note that mitochondrial Ω-oxidation and mitochondrial β-oxidation lead to the triggering of so-called peroxisomal β-oxidation receptors and in particular peroxisome proliferator-activated receptors. This leads to the expression of the accumulation of a certain protein and, accordingly, acetyl-coenzyme A, which accumulates and triggers a mechanism that leads to an overload of dicarboxylic fatty acids.

In the next slide you see that steatohepatitis and fibrosis are formed against the background of mitochondrial reactive oxygen species. The key to triggering fibrosis is undoubtedly the accumulation of malondialdehyde, which leads to the formation of inflammatory infiltrates, fibrosis and activation of stellate cells. Stellate cells trigger the induction of cytokines such as tumor necrotic factor and transforming growth factors. Depletion of the antioxidant system leads to the launch of Fas-legand, a mitochondrial reactive oxygen species, necrosis of the hepatocyte occurs, and fibrous tissue subsequently develops, which is the basis for the development of cirrhosis.

This slide shows a diagram; you see excess lipids that accumulate in the hepatocyte. Mitochondrial dysfunction and dysfunction of cytochrome P450 leads to activation of lipid peroxidation, the launch of Kupffer cells, inflammatory cytokines, activation of stellate cells and apoptosis, which subsequently leads to the development of hepatocyte necrosis.

Metabolic syndrome is very important because non-alcoholic fatty liver disease is part of the metabolic syndrome. And not only on the hepatocyte, in which there is an increase in the level of low-density and very low-density lipoproteins, triglycerides (this is very important), but also on the endothelial cell. Endothelial dysfunction occurs and a moment is also triggered that is associated with lipid peroxidation, the accumulation of substances that affect atherosclerosis, sudden death, and heart attacks.

Undoubtedly, the increase in free fatty acid levels is associated with adipocytes. And a decrease in esterified cholesterol in particular also leads to various stresses of the nuclear receptor. And the so-called activated peroxisome proliferator receptor is especially important at present; it is to it that all the attention of scientists who work with obesity, diabetes, and non-alcoholic fatty liver disease is directed.

A monocyte (macrophage), in some cases, by increasing the level of inflammatory responders (tumor necrotic factor, interleukins-6, membrane toll-like receptors, free fatty acids) also triggers events that are associated specifically with the pathological effects of fatty acids.

The criteria for assessing insulin resistance have been known to everyone since 1985. It is determined by the HOMA index - Homeostasis Model Assessment, and the more modern QUICKI index - Quantitave Insulin Sensitivity. Insulin concentration, serum glucose, and norms are presented here.

We would like to point out that not all patients with non-alcoholic fatty liver disease need a liver biopsy. We currently have points that enable us to determine the level of fatty infiltration of the liver. And in particular this is a fibrotest.

In the algorithm for diagnosing non-alcoholic fatty liver disease, we pay attention not only to specific signs, but also to the activity of the enzymes alanine and aspartic transaminase, gamma-glutamyl transpeptidase, alkaline phosphatase, and we pay attention to alcohol intake, which was discussed by previous colleagues. And I would like to draw attention, of course, to risk factors: metabolic syndrome, insulin resistance, diabetes. Therapy is prescribed to correct this situation, and if necessary, a liver biopsy. Undoubtedly, absolute indications for biopsy are required. And if the body mass index exceeds 35 and 40, then measures are already being taken that are related to surgical treatment.

I would like to draw your attention to a number of medications (non-steroidal - anti-inflammatory glucocorticosis, and steroid drugs, tetracycline antibiotics), a number of nutritional factors (fasting, rapid weight loss, surgical interventions, metabolic genetic factors, in particular, hereditary hemochromatosis, various poisons) and other concomitant diseases. This is very important for differential diagnosis.

At the stage of steatosis, it is important to treat obesity, insulin resistance, and dyslipidemia. In the stage of steatohepatitis, the most important point is the elimination of oxidative stress, inflammation and fibrosis.

Excessive induction of cytochrome P450 2E has detrimental effects on hepatocytes due to the release of free radicals. Essential phospholipids act not only as antioxidants, but also serve as a very important factor for reducing the activity of cytochrome 2E1, as shown in the works of M. Aleynik. The results of some studies suggest that the introduction of essential phospholipids can reduce the induction of cytochrome P450 2E (work by Vladimir Trofimovich Ivashkin, who was presented with Marina Viktorovna Mayevskaya in Russian sources in 2004).

Stellate cells take part in the formation of the final stage of non-alcoholic fatty liver disease. And in laboratory experiments, it has been demonstrated that complete prevention of stellate cell activation using CYP2E1 inhibitors prevents the development of cirrhosis.

I would like to draw your attention to the fact that not only the Russian author M. Aleynik, but also the Japanese author Akiyama in the journal “Hepatology” in 2009, based on the model of alcoholic liver damage, also pays attention to cytochrome P450 2E, acetyl-CoA oxidase and nicotinamide adenine dinucleotide oxidases, that essential phospholipids exhibit anti-inflammatory, anti-apoptotic and anti-fibrotic activity in this pathology.

This is a theoretical version of the assumption of the use of cytochrome P450 inhibitors, and in particular the drug “Essentiale”, which is the reference, and is the most important point for the inhibition of cytochromes P450 2E and, accordingly, P450 4A11. This prevents lipid oxidation, glycolysis and reduces fatty acid synthesis.

The following drugs are used in the treatment of non-alcoholic fatty liver disease: insulin sensitizers, antioxidants, hepatoprotectors, antimicrobials.

But I would like to draw attention to membrane phospholipids. They are the main lipid components of cell membranes. Damage to phospholipid membranes leads to cytolysis syndrome, and excess reactive oxygen species leads to damage to phospholipid membranes based on microsomal γ-oxidation and peroxymal β-oxidation. Accordingly, damage to phospholipid membranes results in cell death, which leads to the initiation of fibrosis and activation of stellate cells.

Damage to the liver structure is damage to the membranes. In the version of essential phospholipids, it is a material that restores cell membranes instead of lipids. Restoring the liver structure makes it possible to restore liver function.

Our patients suffer not only from alcoholic fatty liver disease, alcoholic hepatitis, but also from other liver diseases, this is an indisputable fact. I would like to draw your attention to the fact that according to E. Kunz (2008 monograph), essential phospholipids have an antifibrotic effect, an effect that stabilizes bile and the hepatocyte membrane.

This is a publication that was released in 2008 based on pharmacological and clinical data. Therapy with essential phospholipids seems to be the preferred choice for significantly reducing the manifestation and eliminating fatty liver disease of various etiologies, which has developed due to alcohol consumption, obesity, and even if the cause cannot be discerned.

I would like to point out that there are several studies on Essential. These studies are well known to everyone. But I would like to say that even with diabetes mellitus, Essentiale makes it possible to normalize the level of glucose, glycated hemoglobin, and serum cholesterol in patients with non-alcoholic liver disease.

In conclusion, I would like to say that liver damage characterized by fat accumulation in the absence of alcohol abuse is known as non-alcoholic fatty liver disease. Risk factors include obesity and type 2 diabetes. In the pathogenesis of non-alcoholic fatty liver disease, particular importance is given to the excessive activity of cytochromes P450 2E1. Clinical variants of the course of the disease: pain in the right hypochondrium, asthenovegetative and dyspeptic disorders, hepatomegaly. And our diagnostic algorithm is based on the consistent exclusion of alcoholic and iatrogenic, as well as viral liver damage.

Cytochrome P450 proteins human - a large family of 56 different enzymes encoded by different CYP genes. All P450 enzymes are heme-containing liver proteins; The Fe+2 in heme allows them to accept electrons from electron donors such as nicotinamide adenine dinucleotide phosphate (NADP) and use them to catalyze many different reactions, most commonly the combination of one of the molecular oxygen atoms (O2) with carbon, nitrogen or sulfur atoms.

In the case of many drugs under by the action of cytochromes P450 a hydroxyl group is added to the molecule. This process is usually called phase I of drug metabolism - the introduction of a more polar group into the drug, which provides easy access to the side group. The hydroxyl group attached in phase I creates a point of attachment of a carbohydrate or acetyl group to the drug, which leads to detoxification of the drug and greatly facilitates its excretion (phase II of drug metabolism).

Cytochromes P450 grouped into 20 families according to amino acid sequence homology. Three families - CYP1, CYP2 and CYP3 contain enzymes that are not specific to substrates and are involved in the metabolism of a large number of foreign substances (xenobiotics), including drugs. For pharmacogenetics, six genes in particular (CYP1A1, CYP1A2, CYP2C9, CYP2C19, CYP2D6 and CYP3A4) are especially important, since the six enzymes they encode are responsible for phase I metabolism in more than 90% of all commonly used drugs.

Only CYP3A4 is involved in the metabolism of over 40% of all drugs used in clinical medicine. In addition, many CYP genes are highly polymorphic, with alleles having real functional consequences for response to drug therapy. CYP alleles can result in absent, decreased, or increased enzyme activity, affecting the rate of metabolism of many drugs. For example, CYP2D6, the primary cytochrome in phase I metabolism, is active for more than 70 different drugs. 26 alleles have been described in the CYP2D6 gene, affecting its activity by decreasing, eliminating or increasing it (block).

Missense mutations reduce the activity of these cytochromes; alleles in which there is no activity at all are caused by splicing or frameshift mutations. In contrast, the CYP2D6*1XN allele represents a series of copies of allele numerical polymorphism, when the CYP2D gene is present in three, four or more copies on the same chromosome. As would be expected, the copies result in high enzyme activity. There are more than a dozen alleles that do not affect protein function and are considered wild type. Different combinations of the four classes of alleles result in quantitative differences in metabolic activity, although some combinations are very rare and have not been well studied. There are usually three main phenotypes: normal, reduced and rapid metabolism.

Individuals with reduced metabolism have a clear risk of accumulating toxic drug levels. With rapid metabolism, there is a risk of insufficient effect when using conventional doses that are inadequate to maintain therapeutic levels of the drug in the blood.

Changes cytochrome P450 enzymes Not only are they important for drug detoxification, they are also involved in the activation of certain drugs. For example, codeine is a weak narcotic that has an analgesic effect by being converted to morphine, an active metabolite with a 10-fold increased potency.

Conversion performs CYP2D6 enzyme. Individuals who are poor metabolizers caused by loss of active alleles in the CYP2D6 gene are unable to convert codeine to morphine and will therefore receive little therapeutic benefit. Conversely, for patients with a high metabolic rate, low doses of codeine may be toxic.

Cases of slow and fast metabolism have another complication that is essential for the use of pharmacogenetics in personalized genetic medicine. The frequency of many cytochrome P450 alleles varies among populations. For example, the CYP2D6 poor metabolizer phenotype is present in 1 in 14 Caucasians, is rare in Mongoloids, and is virtually absent in American Indians and Oceanians. Similarly, the slow metabolizer alleles of the CYP2C19 gene have marked ethnic variation, accounting for 3% in Caucasians and almost 16% in all slow metabolizers.