CARBOHYDRATE METABOLISM

From Big Medical Encyclopedia

CARBOHYDRATE METABOLISM — set of processes of transformation of monosaccharides and their derivatives, and also gomopolisakharid, heteropolysaccharides and various uglevodsoderzhashchy biopolymers (glycoconjugates) in an organism of animals, including at the person. As a result At. the lake occurs supply of an organism with energy (see the Metabolism and energy), processes of transfer biol are carried out. information and intermolecular interactions, are provided reserve, structural, protective and other functions of carbohydrates (see). Synthesis of chains of carbohydrate polymers often leads to formation of branchy and extremely various structures, to-rye can be responsible for processes of a morphogenesis, specific adhesion and contact inhibition of cells and define features of determinants of various group-specific substances (see). Carbohydrate components of many substances, naira. hormones (see), enzymes (see), transport glycoproteins (see), are markers of these substances, thanking the Crimea they «uzna-

yutsyatsya» by specific receptors plasmatic and vnutrik letochny membranes.


Fig. 1. Scheme of a gluconeogenesis.


Synthesis and transformations of of l of a go-goat into body and z m e. One of the most important carbohydrates — glucose (see) is not only the main source of energy, but also the predecessor of pentoses (see), uronic acids (see) and phosphoric ethers of hexoses (see).

Glucose is formed of a glycogen (see) and carbohydrates of food — sucrose (see), lactoses (see), starch (see), dextrins (see); besides, glucose is synthesized in an organism from various not carbohydrate predecessors (fig. 1). This process carries the name of a gluconeogenesis and plays an important role in maintenance of a normal homeostasis (see). In the course of a gluconeogenesis the set of enzymes and fermental systems participates. Enzymes of a gluconeogenesis are localized in various cellular organellas: e.g., fruktozo-1,6-di-phosphatase (KF 3.1.3.11) and a lactate dehydrogenase (see) — in cytoplasm, a pyruvatecarboxymanhole (a gek-sozodifosfataz; KF 6.4.1.1) — in mitochondrions, glyukozo-6-phosphatase (KF 3.1.3.9) — in membranes of a cytoplasmic reticulum. The gluconeogenesis occurs hl. obr. in a liver and kidneys. The Fosforolitichesky way of disintegration of glucose — glycolysis is called by Embden — Meyergofa — Parnassus. In addition to glycolysis, there is an oxidizing way of transformations of glucose (a synonym: pentozofos-fatny way, pentozny way, gekso-zomonofosfatny shunt, etc.). From the glyu-kozo-6-phosphate which is formed as a result of phosphorylation of glucose with the participation of a hexokinase (see) and ATP, 6-phospho-gluconolactone turning then in 6-phosphogluconic to - that is formed (see. Gluconic acid). Decarboxylation (see)


Fig. 2. The scheme of reactions of a glycogenolysis to glucose; figures designated the reactions catalyzed by the following enzymes: 1 — fosfornla-

zo y; 2 — amilo-1,6-glucosidase; z — phospho-glucomutase (KF 2.7.5.1): 4 — hl yukozo-6-fos-fatazoy; 5 — and - amylase; 6 — neutral wasps glucosidases; 7 — - acid and - glucosidase (V-amylase); the dotted line designated reaction of formation of a lactate from glyukozo-6-phosphate in muscles in the conditions of lack of activity of the hatch oz Citi phosphate zy.


6-phosphogluconic to - you lead to education ribulozo-

5 phosphates, to-ry is isomerized in ribozo-

5 phosphate (see the Ribose). Schematically pentozofosfatny way looks so: glyukozo-6-phosphate —>

6-fosfoglyukonolak-tone —> ribulozo-5-fos-veils — >ribozo-5-phosphate. During a pentozofosfat-ny way there is consecutive eliminating from a carbon chain of sugar on one carbon atom in the form of C02. In restructurings, to-rye accompany this process, an important role is played by enzymes of a transketomanhole (KF 2.2.1.1) and trance a dale of an az (KF 2.2.1.2). While glycolysis plays an important role not only in power aspect, but also in formation of intermediate products of synthesis of lipids (see), the pentozofosfatny way leads to formation of a ribose and desoxyribose (see), nucleic acids, necessary for synthesis, (see) and a number of coenzymes (see).

Synthesis and disintegration of of l and-kogena. Two enzymes participate in synthesis of a glycogen — the main reserve polysaccharide of the person and the highest animals —: glycogen synthase [

uridinediphosphate (UDF) glucose: a glycogen -

4ss-glucosyltransferase; KF 2.4.1.11], catalyzing formation of polisakharidny chains, in to-rykh glucose units are connected wasps - 1,4 - communication, and

1,4-a-glucan-vetvyashchy the enzyme (KF 2.4.1.18) forming in molecules of a glycogen of so-called communication of branchings (and - 1,6 - bonds).

For synthesis of a glycogen «primings» are necessary. Their role can be carried out or glucosides with various polymerization degree, or proteinaceous predecessors, to the Crimea with the participation of special enzyme — the initiator of synthesis — join glucose units at r ides in d an ifosfa tg l yu to z y (Udfglyukoza).

Disintegration of a glycogen is carried out phosphorus of l itiches by Kym (of l and a koga a yole and h)

or a hydrolytic way. The glycogenolysis represents cascade process, in Krom a number of enzymes of phosphorylase system — a protein kinase (see Kinases), a kinase of phosphorylase 6, phosphorylase £, phosphorylase and (see Phosphorylases)), amilo-1,6-glucosidase (KF 3.2.1.33), glyukozo-6-phosphatase participates. In a liver as a result of a glycogenolysis glucose from a glyukozo-6-fos-veil thanks to effect on it of glyukozo-6-phosphatase, otsutstvukltsy in muscles where transformations of gluco-zo-6-phosphate lead to formation of a lactate is formed. Hydrolytic (amylolytic) disintegration of a glycogen (fig. 2) is caused by action of a number of the enzymes called am silt by elements (see). Are known wasps - (3-and at - amylase (wasps glucosidase). Depending on localization in a cell distinguish acid (lysosomic) and neutral and - glucosidases.

Synthesis and r asp and d at of l e-in about d with about d e r and shch and x with about e d and - N e N and y. Synthesis of complex sugars and their derivatives happens to the help of the specific glpkozil-transferases (KF 2.4) catalyzing transfer of monosaccharides from donors — various glikoziliukleo-tid or lipidic, carriers to substrates acceptors (see the Transfer elements), to-rymi there can be a carbohydrate rest, polypeptide or a lipid depending on specificity of transferases. The nucleotide rest is usually difosfonuk-leozid. So, I in lyayuts I milk an uridindifosfatsakhar (U D Fsa ha ra) about ra mi

for glycosides (see) glucose, galactoses (see), N-atsetilglyukozamina and N-atsetilgalaktozamina (cm/lyuk deputy and i), xyloses (see) and glucuronic to - you (see. Hexuronic acids); guanozindifosfatsakhara I

manioza (see) and fuk> (see), and derivatives sia-lo'>, 'vlyatsya by donors for synthesis sootvetst-vuyushchp\roizvodny. Ch'Sh (see) are formed of a .tsita of a lppchyufosfat. Variety<!:! and Goya and ha r go y x structures (see. About l and () with and. are and d y) in glycoproteins, nroteogl icons. the hl and a stake both p ides (see) and polisa./arida (see) is explained by existence various siyetsi-fichesny glikoziltraisferaz (ksi-loz of itraisferaz, the Gaul aktoziltrans-feraz. glyukuronnltransferaz and t). There were data about a possible ti of non-enzymatic of l and -

a kozilprovapiya of proteins of in vivo, e.g. hemoglobin, proteins of a crystalline lens. collagen, etc. There are data that non-enzymatic gli-kozilirovaiy plays an important pathogenetic role at nek-ry diseases (a diabetes mellitus,» of l o:n rumple hectare of l, etc.).

([) (*! '.м '-itatpvnoye a rasshchsileniye carbohydrate-sodo]»' / •» ■ p) \\\connections occurs in bases:;;-m; ndroliticheekpm in the way by means of i lsh.'kmgdaz, chipping off trailer. i.<» m ye remains (okzoglikozidaz) of a pla of 'i .iM'< >\arid fragments (endo-glii<>., (. from corresponding gliko-

a game y<. Glikozidaza's km are chrez-vych.ip'> (i mythical enzymes. In zavsh< iiv i 1 «by nature a monosaccharide, KONF | >11 5' (‘GO of a molecule (their D-or

L-ii yu-chgpp!;. and like a hydrolizable linkage (and or (about distinguish «-D-mannozidazy, a - L - fm ides «-y, |-! - 13 galactosidases etc. P i. M'Ti; ax of a glikozidaza is localized.1’ a .lichny cellular organel-

la. Whether-aoco.vfv Mi in N *‘ from them localized in»' m Lysosomic (acid) a glycoside, w ■ michatsya from neutral not Tola; 1 v tzatsiy in cells, optimum 1 f of their action by a pH value and a pier. p (weight), but p zlektroforeti-

chesk< n< of m yyustyyu and some other fi::> - v i (the ISC.

1 i, ii i of m! y play an important role to paradise of n 1 11.\» floor. processes; they can, napr 1vat influence on specifically 11 - a wound f about i> of m 111) about in and N of N y x to l e that to,

on - 1*1. an istviye of cells with

the D1 viruses I).

In z and and m about n p e in r and shch e N and I at of l e in about d about in in about r and N and z m e. In a human body and animals there are many various mechanisms responsible for transformation of one carbohydrates into others as in processes of glycolysis and a gluconeogenesis. and in separate links of a lentozofosfatny way. Uridin-difosfatga lactose (At Dfga lactose) prevrsitsa) e the gay by an epimerization in> DF ISO a goat, this reaction was rolled-zir> (i<> p i (KF 5.J.3.2) Udfglgokoza-4-epi enzyme \c. Education' >ir\i of an oza (naira., in seed IU R, r!>! the l of i) comes from glucose, an intermediate product in this case is eorbitol. As a source and mpnosakhar (see Aminosugar) serve fruktozo-6-phosphate and a glutamine: fruktozo-P-fosfat glutamine of t': glyukozampn-6-phosphate + glutaminic to - that.

The specific kinase (see Kinases) catalyzes transformation of N-atsetilma of a pnozampn in U-atsetilman-nozamiifi >sfat, the ktion of condensation to-rogo with fosfoyepolpiruvaty leads a re to formation of N-acetyl-neyraminil-9-phosphate; the last, being dephosphorylated, forms it-r an amipova yu acid (see). The liver of mammals contains the special specific kinase catalyzing transition of D-xylulose to D - ksilulozo-5-phosphate, to-ry can join in exchange on a pentozofos-fatny way.

T r and N with ii of ORT at of l e in about d about century. In an oral cavity with the participation of hydrolases of saliva (see) digestion of carbohydrates begins. In a stomach hydrolysis of carbohydrates enzymes of saliva [fermentation of carbohydrates of a food lump continues (see Fermentation) it is prevented salt to - that a gastric juice (see)]. In a duodenum under the influence of juice under - ate at d about the h and about and elez y (with m) and about l is and x and - rida of food (starch, a glycogen, etc.) and sugar (oligo-and disaccharides) are split with participation I-glyu-kozidazy and others glikozidaz to monosaccharides, to-rye and soaked up in a small bowel in blood. Speed of absorption of carbohydrates is various, glucose and a galactose, more slowly — fructose, mannose and others of sugar are most quicker soaked up.

Passing of the soaked-up carbohydrates through epithelial cells of intestines and receipt in cells of peripheral fabrics are carried out by means of special transport systems, function to-rykh consists in transfer of molecules of sugars through superficial cellular membranes. There are special proteins carriers — the permeaza specific in relation to sugars and their derivatives. Permeaza call also translocases (e.g., trans-l about for glyukozo-6-phosphate, Udfglyu-kuronova to - you, etc.). Transport of carbohydrates can be passive and active (see Membranes biological, Permeability). At passive transport transfer of carbohydrates is carried out on a gradient of concentration (see the Gradient) so balance is reached when concentration of sugar in intercellular substance or intercellular liquid and in cells are leveled. Passive transport of sugars is characteristic of erythrocytes of the person. At active transport carbohydrates can collect in cells and their concentration in cells can be higher, than in surrounding liquid of a cell. In a human body and animals active transport of carbohydrates occurs hl. obr. in epithelial cells of a mucous membrane of intestines (see Absorption) and in gyrose tubules (proximal departments of an iyefron) of kidneys (see Kidneys, physiology). The system of transport of glucose and galactose is accompanied by system of transport of ions Na+. Assume that active absorption of sugars cells differs from passive in the fact that the last is ^^-независимым process. I would eat m rain y and transport of sugars is studied better than in vitro (on suspensions of erythrocytes, drugs of various sites of intestines, on cuts of a brain, muscles and other fabrics), than in vivo. In spite of the fact that features of this process and its kinetics are studied rather fully, a lot of things in it are still not clear.

P e at l I am c and I am carbohydrate of N of au g about about m e N and. Regulation At. the lake is carried out with the participation of very difficult mechanisms, to-rye can exert impact on induction or suppression of synthesis of various enzymes U. the lake or to promote activation or braking of their action. Insulin (see), catecholamines (see), a glucagon (see), somatotropic hormone (see) and steroid hormones (see) render various, but very expressed influence on the different parties At. lake. So, e.g., insulin, being hormone of universal anabolic action, promotes accumulation in a liver and muscles of a glycogen, activating enzyme to a gliko-gensintaz, and suppresses a glycogen of l from and a gluconeogenesis. The antagonist of insulin — a glucagon stimulates a glycogenolysis. Adrenaline (see), stimulating effect of adenylatecyclase (KF 4.6.1.1), exerts impact on all cascade of reactions of a phosphorolysis (see).

Gonadotropic hormones (see) activate a glycogenolysis in a placenta (see). Glyukokor tikoidny hormones (see) stimulate process of a gluconeogenesis. In regulation of a gluconeogenesis also both the cat and N am ides hell e-

iiidinukleotid take part atsetil-KOA and in wasps from tannins about in l enn y (see). Increase in content of fatty acids (see) in a blood plasma brakes activity of key enzymes of glycolysis — a fosfofruktokinaza (KF 2.7.1.11), etc. Somatotropic hormone exerts impact on activity of enzymes of an iyentozofosfatny way and reduces utilization of glucose peripheral fabrics. In regulation of enzymatic reactions At. the lake an important role is played by ions of Sa2+, directly or with the participation of hormones, is frequent in connection with special Sa2+-svyazyvayushchim protein — a calmodulin.

In regulation of activity of many enzymes of carbohydrate metabolism (e.g., glikogensintaza, phosphorylases, fosfofruktokinaza, etc.) processes of their phosphorylation and dephosphorylation are of great importance (see Phosphorylation).

Pathology of carbohydrate metabolism. Increase in content of glucose in blood ■ — a hyperglycemia (see) can occur owing to excessively intensive gluconeogenesis or as a result of decline in the ability of utilization of glucose fabrics, napr, at disturbance of processes of its transport through cellular membranes. Decrease in content of glucose in blood — a hypoglycemia (see) can be a symptom of various diseases and patol. states, and the brain in this respect is especially vulnerable: irreversible disturbances of its functions can be a consequence of a hypoglycemia.

Genetically caused defects of enzymes U. lakes are the reason of many hereditary diseases (see). (See) the galactosemia (see) developing as a result of defect of synthesis of enzyme galaktozo-1-phosphate-uridililtransferazy (KF 2,7.7.10) can be an example of genetically caused inherited disorder of exchange of monosaccharides. Symptoms of a galactosemia note also at genetic defect Udfglyukoza-of a 4-epimeraza. The first symptoms of a disease note at children soon after the birth. Characteristic symptoms of a galactosemia are a hypoglycemia, hectares lactose a riya, emergence and accumulation in blood along with a galactose (see) galaktozo-1-phosphate, and also decrease in body weight, fatty dystrophy and cirrhosis, jaundice, the cataract developing at early age, a delay of psychomotor development. At a severe form of a galactosemia sick children often perish on the first year of life owing to disturbances of functions of a liver or the lowered resilience to infections. The diagnosis of a galactosemia is made on the basis of results of definition of activity by galaktozo-1-phosphates-uridililtransfe-times in erythrocytes of sick children, and also their parents — heterozygous carriers of this disease inherited on an autosomal re-tsessivnomu to type. Early diagnosis of a galactosemia is extremely important since it is able to afford to avoid defeat of c. and. page and development of a cataract. The exception of food of a galactose and the corresponding dietotherapy applied during the early period of a disease give the expressed therapeutic effect.

Example of hereditary intolerance of monosaccharides is the intolerance of fructose (see), to - paradise fructose phosphate-zymohexase and in some cases — decrease of the activity of fruktozo-1,6-di-phosphate-zymohexase (KF 4.1.2.13) therefore process of glycolysis is blocked on a mode of formation dihydroxy acetone-phosphate and glitseral-degid-3-phosphate from fruktozo-1,6-is caused by genetic defectdiphosphate. The disease is characterized by damages of a liver and kidneys; for a wedge, pictures spasms, frequent vomiting, sometimes coma are characteristic. Symptoms of a disease appear in the first months of life at transfer of children into the mixed and artificial nutrition. Loading fructose causes a sharp hypoglycemia. The exception of food of the products containing fructose provides therapeutic effect.

At genetic insufficiency of a fosfofruktokinaza (KF 2.7.1.11) the riya (see) which is followed by a fruktozemiya, fruktozuriy, but not having a wedge, manifestations develops so-called essentspalny fructose. At loading fructose of a hypoglycemia do not observe. Because at an essential fruktozuriya defect consists in blocking of synthesis of a fruktokinaza, disturbance of exchange of fructose is not followed by accumulation in blood is not turned - nogo enzymatic reaction (fruktozo-6-phosphate).

The diseases caused by defects in exchange of oligosaccharides (see) generally are in disturbance of splitting and absorption of carbohydrates of food that there is a hl. obr. in a small bowel. The maltose and low-molecular dextrins (see) formed of starch and a glycogen of food under action and - ptyalin and juice of a pancreas, lactose (see) milk, sucrose (see), are split by disaccharidases (see Disaccharides), maltase (KF 3.2.1.20), lactase (KF 3.2.1.23) and invertase (KF 3.2.1.26 and 3.2.1.48) to the corresponding monosaccharides generally in microvillis of a mucous membrane of a small bowel, and then if process of transport of monosaccharides is not broken, there is their absorption. Absence or decrease of the activity of disaccharidases serves as the main reason of intolerance of the corresponding disaccharides in a mucous membrane of a small bowel that often leads to damage of a liver and kidneys, is the reason of diarrhea, a meteorism (see Maljabsorb-tion a syndrome). Especially heavy symptoms characterize the hereditary lactose intolerance which is found usually since the birth of the child. Apply usually load tests with introduction to diagnosis of intolerance of sugars on an empty stomach of per os of carbohydrate, to-rogo suspect intolerance. Glycemic curves (see Carbohydrates) at such patients are flattened in comparison with normal. More exact diagnosis can be made by a biopsy of a mucous membrane of intestines and definition in biopsy material of activity of disaccharidases. Treatment consists in an exception of food of the products containing the corresponding disaccharide. More considerable effect is observed, however, during the use of fermental drugs (see Epzi-moterapiya) that allows such patients to eat usual food. In case of, e.g., insufficiency of lactase, the fermental drug supporting her it is desirable to add to milk before the use it in food. The correct diagnosis of the disakhari-doz caused by insufficiency of disaccharidases is extremely important. The most frequent diagnostic mistake in these cases is establishment of the false diagnosis of dysentery and treatment by antibiotics that leads to a bystry aggravation of symptoms of sick children and to serious consequences.

The diseases caused by disturbance of exchange of a glycogen make group of the hereditary enzymopathies (see) combined under the name glycogenoses (see) and characterized excess accumulation of a glycogen in cells. The large number of enzymes and fermental systems takes part in exchange of a glycogen. Disturbances in separate links of these systems lead to considerable decrease in maintenance of a glycogen in cells or, on the contrary, to its abnormal accumulation, a cut can be followed by structural change of molecules of this polysaccharide also. Almost total absence in cells of a glycogen is noted at an aglikogenoza. Reduced activity of a glikogensintaza of a liver or total absence of activity of this enzyme is the reason of an aglikoge-noz. Glycogenoses (a glycogenous disease) — the diseases inherited on autosomal recessively or to the type linked to a floor. Depending on that what defect of enzyme is a cause of infringement of exchange of a glycogen, distinguish glycogenoses of different types. In total 12 types of glycogenoses are still known. Besides, there are different forms (subtypes) of this disease that is defined by localization of fermental defect. E.g., at Mac-Ardla's disease abnormal accumulation of a glycogen happens only in skeletal muscles because of genetically caused defect of phosphorylase (KF 2.4.1.1) of muscles. The disease to Awnless wheat caused by genetic defect of glyukozo-6-phosphatase represents a hepatic form of the glycogenosis having 3 subtypes. At a disease to the Pomp, edges is a consequence of insufficiency or absence lysosomic acid and - glucosidases (at - amylases), observe abnormal accumulation of a glycogen almost in all bodies of the patient (a so-called generalized form of a glycogenosis). Cory's disease caused by defect amilo-1,6-gluco-zidazy — the enzyme splitting bonds in points of branchings in molecules of a glycogen is characterized by accumulation of structural and abnormal glycogens — limitdekstrin, to-rye can collect in different bodies, causing existence of various forms and subtypes of this disease. Depending on emergence of the first symptoms distinguish early, youthful and adult forms of nek-ry types of a disease. At the same patient multiple fermental defects are observed seldom. Glycogenoses carry to so-called diseases of accumulation.

Klien, a picture of glycogenoses is often similar about a wedge, a picture of other diseases. So, e.g., nek-ry glycogenoses of a hepatic form remind hron. hepatitis (see), a disease to Gosha (see Gosha a disease), tumors of a liver. Glycogenoses of a muscular form are quite often similar to the progressing muscular dystrophy and myopathies of various origin (see the Myopathy), and glycogenoses of a generalized form — to a fibroelastosis of an endocardium, myocarditis. In this regard diagnosis of glycogenoses cannot be based only on a wedge, observations and demands special biochemical researches. The final diagnosis of a disease can be made only after detection of euzymatic defect in the fabric received at a biopsy of the struck body. Only after establishment of the diagnosis perhaps correct treatment, various at different types of a glikogeioz. At a generalized form of a disease treatment is not effective yet. At a high risk of the birth of children with such pathology prenatal diagnosis is necessary (see. Medicogenetic consultation). Prenatal diagnosis of generalized forms of glycogenoses is based on definition of activity of the corresponding enzymes in culture of cells of an amniotic fluid of pregnant women with suspicion on a carriage of a disease.

The diseases caused by disturbance of exchange of various glycoconjugates (uglevodsoderzhashchy biopolymers) in most cases are a consequence of inborn disturbances of disintegration of glikoliiid, glycoproteins or glikozaminogli-kan (mucopolysaccharides) in various bodies. They are also diseases of accumulation. Depending on what connection abnormally collects in an organism, distinguish glycolipidoses, of l and to about p r about t of e i sh about z y, mukopolisakharido-za (see). Many lysosomic gliko-zidaza, defect to-rykh is the cornerstone of an inherited disorder

At. lakes, exist in various molecular forms (see Isoenzymes). The disease can be caused by defect of one any isoenzyme. So, e.g., a disease Teja — the Saxophone (see. An amaurotic idiocy) — a consequence of defect of the N-atsetilgeksozaminidazy form A (hexose-minidazy A) while defect of forms A and B of this enzyme leads to Sandgoff's disease (see Gli-kozidoza, t. 10, additional materials).

The majority of diseases of accumulation proceeds extremely hard, many of them are still incurable. The wedge, a picture at various diseases of accumulation can be similar and, on the contrary, the same disease can be shown differently at various patients. Therefore it is necessary to establish in each case the euzymatic defect revealed by the most part in leukocytes and fib uniforms flippers of skin of patients. As substrates apply the native or synthetic substrates specific to the defined enzymes. Synthetic substrates usually are derivatives of glycosides. At various mukopolisakharidoza, and also at nek-ry other diseases of accumulation (e.g., at a mannozidoza) with urine oligosaccharides, various on structure, in significant amounts are removed. Allocation of these connections from urine and their identification are used for diagnosis of diseases of accumulation. Definition of activity of enzyme in culture of cells from the amniotic fluid received at amniocentesis at suspicion of a disease of accumulation allows to make the prenatal diagnosis.

Serious violations At. lakes come for the second time at nek-ry diseases. An example of such disease is the diabetes mellitus (see a diabetes mellitus) caused or defeat (3 cells of the insular device of a pancreas, or defects in structure of the insulin or its receptors on membranes of cells of insulinchuvst-vitelny fabrics. In an organism there is a feedforward between At. the lake and exchange of proteins (see. A nitrogen metabolism), lipids (see the Lipometabolism) and mineral substances (see. Mineral metabolism).

In detail about diseases, the pathogeny to-rykh is connected with disturbances of carbohydrate metabolism — see articles devoted to individual diseases, e.g. An argoilizm, Gosha a disease, Maroto — Lamy a disease, Morkio a disease, Sanfilippo a disease, Fabri a disease (see Glikozidoza, t. 10, additional materials), Sheye a disease, etc., and also articles with descriptions of individual carbohydrates or their groups, e.g. Heparin, Hyaluronic acids, Mannose, Sialic acids, Foo goat, etc.

Features of carbohydrate metabolism at children. A state At. the lake at children normal is defined by degree of a maturity of endocrine mechanisms of regulation and functions of other systems and bodies. In maintenance of a homeostasis of a fruit an important role is played by intake of glucose to it through a placenta. Amount of the glucose arriving through a placenta to a fruit, changeably since its concentration in blood of mother can change several times a day. Change of size of a ratio insulin/glucose at a fruit can cause in it acute or long disbolism. In the last third of the pre-natal period at a fruit stocks of a glycogen in a liver and muscles considerably increase, during this period a glycogenolysis and the gluconeogene z already have for a fruit essential value and as a source of glucose.

Feature At. the island at a fruit and the newborn, allowing them is better to adapt to conditions of a hypoxia, high activity of processes of glycolysis is. Intensity of glycolysis at newborns is 30 — 35% higher, than at adults; in the first months after the birth it gradually decreases. High content in blood and urine of lactic acid (see) — a lactate and higher, than at adults testifies to high intensity of glycolysis at newborns, activity is lactate dehydrogenases (see) in blood. A considerable part of glucose at a fruit is oxidized on a pentozofos-fatny way.

The patrimonial stress, change of ambient temperature, emergence of independent breath in newborns, increase of muscular activity and activity of a brain increase at them power consumption during childbirth and the first days of life, leading to bystry decrease in content of glucose in blood. In 4 — 6 hours after the birth its contents reaches the lowest value — 40 — 60zhg/100 ml, remaining at such level during the next 3 — 4 days. The increased consumption of glucose fabrics at newborns and the period of starvation after the delivery is led to strengthening of a glycogenolysis and use of a reserve glycogen and fat. The stock of a glycogen in a liver at the newborn in the first 6 hours of life is sharply reduced (approximately by 10 times), especially at asphyxia (see) and starvation. Content of glucose in blood reaches age norm at the full-term newborns to 10 — to the 14th day of life, and at premature children is established only to 1 —

to the 2nd month of life.

In intestines of newborns enzymic hydrolysis of the main carbohydrate of food during this period — lactoses — is a little reduced and increases at chest age. Exchange of a galactose at newborns is more intensive, than at adults.

Disturbances At. lakes at children at time l and chn y x with about m and t and h the EU to and x for about l e in and N iya x have secondary character and are connected with influence of the basic patol. process on this type of exchange. La -

11 l and about with t of Kommersant of per mechanisms at l I am i of, and and carbohydrate and a lipometabolism at early children's age creates premises for emergence of I'lriio-and hyper glycemic states, atsetonemichesky vomiting (see L a tsetopemiya). So, e.g., disturbances At. lakes at pneumonia at children of early age are shown by increase in blood on an empty stomach of concentration of glucose and a lactate depending on degree of respiratory insufficiency (see). The Intolerant-nost to carbohydrates comes to light at obesity (see) and is caused by change of secretion of insulin. At children with intestinal syndromes often reveal disturbance of splitting and absorption of carbohydrates, at a Gee's disease (see) note flattening glycemic curve after loading starch, disaccharides and monosaccharides, and at children of early age with acute coloenterites and a soledefitsitny state during an eksikoz observe tendency to a hypoglycemia.

In blood of children of advanced age normal there are no galactose, pentoses and disaccharides, at children of chest age they can appear in blood after meal, rich with these carbohydrates, and also at genetically caused anomalies of exchange of the corresponding carbohydrates or uglevodsoderzhashchy connections. In most cases symptoms of such diseases are shown at children at early and even chest age.

For early diagnosis of the hereditary and acquired disturbances At. lakes at children apply stage system of inspection with use of a genealogical method (see) and various rapid tests, and at the subsequent stages — more in-depth biochemical studies (see Screening in medicine). At the first stage of inspection carry out definition in urine of glucose, fructose, sucrose, lactose qualitative and a floor by quantitative methods, check the size pH a calla (see Kal, methods of a research). During the obtaining the results forcing to suspect pathology At. lakes at the child, pass to the second stage of inspection: to determination

of content of glucose in urine and blood on an empty stomach quantitative method-megapixel, to creation of glycemic and glyukozurichesky curves, a research of glycemic curves after the differentiated sugar loadings, to determination of content of glucose in blood after administration of adrenaline, a glucagon, a leucine, Tolbutamidum. cortisone, insulin; regarding cases carry out direct definition of activity of disaccharidases in a mucous membrane of duodenal and thin guts and hromatografichesky identification of carbohydrates of blood and urine. For identification of disturbances of digestion and absorption of carbohydrates after establishment of the size pH a calla define tolerance to mono - and to disaccharides with obligatory measurement of content of sugars in Calais and their hromatografichesky identification before load tests by carbohydrates. At enzymopathies in blood and fabrics define activity of enzymes U. the lake, defect of synthesis or suppression of activity to-rykh are suspected by clinical physicians.

For correction broken At. lakes at a tendency to a hyperglycemia apply a dietotherapy with restriction of carbohydrates and fats and if necessary insulin or other gipogli-kemiziruyushchy drugs; the means promoting increase in content of glucose in blood cancel. At a hypoglycemia it is necessary to warn her attacks a diet, carbohydrate-rich and proteins. During attacks of a hypoglycemia enter glucose, a glucagon, adrenaline. At intolerance of separate carbohydrates appoint an individual diet with an exception of the corresponding sugars of food of patients. Development of methods of introduction to an organism of missing enzymes U is perspective. whether the lake in a nose ah (see). In cases of disturbances At. about. having secondary character, treatment of a basic disease is necessary.

For prevention of the expressed disturbances At. the lake is necessary their timely detection at children. At probability of hereditary pathology At. the lake is recommended medicogenetic consultation (see. Medicogenetic consultation). The expressed adverse influence of a decompensation of a diabetes mellitus at pregnant women women on At. the lake at a fruit and the newborn (see a diabetes mellitus) dictates need of careful compensation of a disease at mother throughout pregnancy and childbirth.

Change of carbohydrate metabolism in the course of aging. Since 20 — 25 years, tolerance to glucose is broken, i.e. the speed of its use by fabrics decreases. Reduction in the rate of utilization of glucose is combined with increase in blood of concentration of insulin ate meal. This process happens quicker at men; at women to 40 —-49 laid down decrease in tolerance peripheral to fabrics to glucose develops more slowly, but by 60 — 09 years these zp i.\I compare v ie in at persons of both sexes. *

Along with decrease to» yurant-nost of ii to glucose during the aging receipt in blood of insulin therefore time of achievement of its maximum concentration in blood increases from 60 min. to 120 min. is late. On)'! about i at at statement glucosic 1(4"; «» with intravenous administration of 50 m • oP'N.,


seams of a teniye

of concentration of insulin in blood do not find solution of glucose when concentration of insulin in blood is defined through 5--10 min. after the end of administration of glucose, a vozr of stny i.

The combination to an age gpmerglmka of mines and a giperiisulinemiya at to, myvat on decrease effective and the deist - the Viy of insulin on a target tissue, It is known several reasons creating the mechanism of this disturbance: 1) strengthening of influence of koptrainsu-lyarny factors, in particular cortisol, neeterifitsprovaiiy fatty acids (NEZhK) and from ohms of aio of tracks -

11 about go hormone (concentration of the last in blood decreases at development of age obesity); 2) reduction of number of specific receptors on plasmatic, a membrane of cells that is partially connected with development of age obesity and the increase in basal level of insulin caused by it in blood; it brings according to a negative feedback mechanism, between concentration of hormone into blood and number of receptors to it on cellular membranes to decrease in their quantity;

3) increase with age concentration of the pro-insulin (see Insulin) in blood possessing insignificant biol. effect (however improvement of tolerance to carbohydrates under the influence of an antidi betiches whom medicine of a feiformin calls into question a role of increase in a share of pro-insulin in age decrease in tolerance to carbohydrates);

4) change of the mechanism effect of insulin after linkng with receptors of target cells. The combination of an alimentary hyperglycemia and a gi-perinsulinemiya leads to development of obesity that increases l and got also use of NEZhK as power substrate (see the Metabolism and energy, in the course of aging). It even more worsens utilization of glucose in muscular tissue and stimulates glyukonsogenez. In turn, surplus - in NEZhK blood and insulin leads to increase in synthesis in a liver of triglycerides (see Fats) and cholesterol (see)' and respectively to increase in concentration in blood of lipoproteids of very low and low density (I eat. L of an ipoproteida). It creates conditions for development of atherosclerosis, decrease of the activity of immunity, and also, apparently, is one of the reasons of age increase in frequency of developing of cancer. Therefore clarification of the reasons of inclusion of the .mekhanizm leading to a cart-rastno mu to decrease in tolerance of fabrics to carbohydrates is so important. The former explanation of this age phenomenon connecting it with exhaustion of products of insulin lost the value; new explanations for the present have hypothetical character.

Carbohydrate metabolism in the irradiated organism. At impact of ionizing radiation in the doses causing in experimental animals an acute radial illness (see) there are disturbances At. the lakes depending on radio sensitivity of fcM.) and fiziol. features of separate fabrics. Increase in maintenance of a glycogen in a liver with two peaks of raising of maintenance of a glycogen — on 1 — the 2nd and 9 — after radiation is among the 14th days such changes (I eat.). Strengthening of a gluconeogenesis as a result of radiation in spite of the fact that within several days after radiation activity of key enzymes of glycolysis — hexakina zy increases, a fosfofruktokinaza, a glyukozofosfatizomeraza is the main reason for abnormal strengthening of adjournment of a glycogen in a liver. Along with it observe braking of okis-l itet ny decarboxylation of a niruvat in a cycle tricarboxylic to - t (see. Tricarboxylic acids cycle). Nevertheless during the early period of an acute radial illness change is characteristic of hepatic fabric At. the lake is preferential on anabolic type. Parallel to increase in maintenance of a glycogen in a liver in blood of the irradiated animals concentration of glucose increases. Iostradna i «dune gipergl an ikemiya

is caused by change of a hormonal background in the irradiated organism. Oxidation of glucose to C02 is at the same time considerably reduced. Of l and to e m and che - missing a bit the curve after loading glucose is very characteristic: reveal

dvugorbost a glycemic curve and a pseudo-diabetic delay of its decrease. Insulin only in a maxim of l of I.Mых <>dza causes normalization of oxidation of glucose that testifies to the lowered ability of fabrics to utilize glucose. At. the lake in radio resistant fabrics (skeletal muscles, a cardiac muscle, a brain, skin, bones) at action of ionizing radiation does not undergo essential changes. In an adenoid tissue note oppression of a pentozo-phosphatic way of oxidation of glucose. In marrow there is a reorganization of interrelation between glycolysis and a pentozofosfatny way, activity transketo-manholes towards increase in synthesis of fruktozo-6-phosphate and glitseralde-guide-3-phosphate increases. Activity glucose

- phosphate — dehydrogenases within several days after radiation is sharply oppressed. Thus, in the hemopoietic fabric there is an inhibition of a pentozofosfatny way and an intensification of glycolysis. The majority of the specified disturbances At. the lake in fabrics depends on an ionizing radiation dose. At massive single exposition in non-lethal doses these disturbances rather quickly disappear. Hron. radiation by doses of low power (see Dosage rate of radiation) causes rather poorly expressed changes At. lakes, to-rye, however, remain a long time after the termination of beam influence. The majority of the listed disturbances At. the lake has reversible character. In general At. the lake is characterized by high resistance to the striking action of ionizing radiation.

Bibliography: Badalyan L. O., T and au l and N V. A. and Veltishchev Yu. E. Hereditary diseases at children, M., 1971; Vidershayn G. Ya. Biochemical bases of glikozidoz, M., 1980; Hormonal regulation of functions of a children's organism is normal also of pathology, under the editorship of M. Ya. Studenikin, etc., page 33, M., 1979; D and l m and V. M N. Transformation of the program of development in the mechanism of age pathology, Elevatsionnaya model of age pathology and the natural death of the person, Fiziol. person, t. 4, No. 4,

page 579, 1978; To about m and a ditch F. II., To a shouting about in to and B. F. N and M with N sh and - to about in V. V. Biochemical researches in clinic, page 407, L., 1981; M e c-l e r D. Biokhimiya, the lane with English, t. 2, M., 1980; R and h e in L., T about d about r about in Y. and With t and t e in and With t. Metabolism at children's age, the lane with bolg., page 68, 266, Sofia, 1967; R about z e N f e l d E. L. Molecular pathology of exchange of carbohydrates, in book: A pier to. bases patol., under the editorship of

V. N. Orekhovich, page 80, M., 1966; R about -

3 e N f e l d E. L. and P about and about in and I. A. Glikogenovaya a disease (biochemical bases), M., 1979; The Reference book on functional diagnosis in pediatrics, under red-KZ. E. Veltishcheva and N. S. Kislyak, page 107, M., 1979; At and y t And., etc. Fundamentals of biochemistry, the lane with English, t. 2, M., 1981;

4 e r to and L. S.'s owl and M and r about N about -

in and T. M. Influence of ionizing radiation on enzymes of carbohydrate metabolism, Radiobiology, t. 16, century 5, page 657, 1976; Biochemistry of carbohydrates, ed. bv W. J. Whelan, L., 1975; Carbohydrate metabolism and its disorders, ed. by F. Dickens a. o., v. 1 — 2, L. — N. Y., 1968;

H a v W. W. Fetal glucose metabolism, Semin. Perinat., v. 3, p. 157, 1979; P o-1 at with 1) r o n a k about s C. and. lake of Carbohydrate intolerance in children and adolescents with Turner syndrome, J. Pediat., v. 96, p. 1009, 1980. E. L. Rosenfeld

(biochemistry and pathology of carbohydrate metabolism), V. M. Dplman (rep), Yu. A. Knyazek

(week), A. V. Nikolsky (I am glad.).

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