Metabolism in children

The most important component of the body's vital activity is metabolism, i.e. the body's ability to accept, process, maintain at some optimal levels and eliminate various chemical substances. One of the functions of metabolism is the assimilation of food, its transformation into its own cells and tissues to provide energy needs for vital activity, physical activity and growth.

Metabolic processes in children and adults consist of assimilation processes - the absorption of substances entering the body from the environment, their transformation into simpler substances suitable for subsequent synthesis, the processes of synthesis of substances themselves, or "blocks" - "parts" for the construction of one's own living matter or energy carriers, and dissimilation processes - the breakdown of substances that make up a living organism. The processes of synthesis of organic compounds (consuming energy) are called anabolic (anabolism), the processes of breakdown (forming energy) - catabolic (catabolism). Life is possible only with a constant and inseparable connection between the processes of breakdown and synthesis, due to which the development and self-renewal of the organism is carried out.

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Features of metabolism in children

In children, during their growth and development, anabolic processes predominate over catabolic processes, and the degree of predominance corresponds to the growth rate, which reflects the change in mass over a certain period of time.

Metabolic processes in the human body are associated with certain structural formations. Most metabolic processes, especially oxidative and energy processes (Krebs cycle, respiratory chain, oxidative phosphorylation, etc.), occur in mitochondria. Therefore, mitochondria of a cell are often called the "power stations" of the cell, which supply energy to all its other parts. Protein synthesis occurs in ribosomes, and the energy required for synthesis is obtained from mitochondria. The main substance of protoplasm - hyaloplasm - takes a large part in the processes of glycolysis and other enzymatic reactions.

Along with the cellular structures, tissues and organs created during ontogenesis only once and for life, many cellular structures are not permanent. They are in the process of continuous construction and breakdown, which depends on metabolism. It is known that the lifespan of erythrocytes is 80-120 days, neutrophils - 1-3 days, platelets - 8-11 days. Half of all blood plasma proteins are renewed in 2-4 days. Even bone matter and tooth enamel are constantly renewed.

The progressive development of the human organism is determined by hereditary information, thanks to which proteins specific to each human tissue are formed. Many of the genetically determined proteins are part of the enzyme systems of the human organism.

Thus, in essence, all metabolic processes are enzymatic and proceed sequentially, which is coordinated by a complex system of regulatory chains with direct and feedback connections.

In a child, unlike an adult, the formation and maturation of metabolic processes occurs, reflecting the general tendency of development and maturation of the organism with all their disharmonies and critical states. Environmental factors can act as inductors and stimulators of the maturation of metabolic processes or entire functional systems. At the same time, the boundaries between a positive, development-stimulating external influence (or its dose) and the same influence with a destructive pathological effect can often be very thin. This is expressed in the lability of metabolism, its frequent and more pronounced disturbances under various living conditions or diseases.

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Metabolic disorders in children

In children, metabolic disorders can be conditionally divided into three groups.

The first group of metabolic diseases are hereditary, genetically determined diseases, less often - anatomical malformations. As a rule, the basis of such metabolic diseases is a deficiency (of varying severity) of an enzyme or enzymes necessary for the metabolization of a particular substance, and a stable unfavorable situation is noted with the breakdown of the original food components, intermediate transformation or synthesis of new metabolites or elimination of end products. Often, the deficiency or excess of substances that arise under conditions of altered metabolism have a very significant effect on the viability of the child or his physiological functions. Maintaining health or normal life for such patients requires constant measures of correction and assistance, often lifelong restrictions, replacement measures, clinical and laboratory monitoring, special food products. A significant part of genetically determined diseases or metabolic disorders may not manifest clinically at all in childhood. Children who are carriers of this pathological condition attract attention only in adulthood after the onset of relatively early or severe forms of vascular diseases (atherosclerosis of the cerebral or cardiac vessels), hypertension, chronic obstructive pulmonary diseases, liver cirrhosis, etc. Relatively early detection of genetic or biochemical markers of these diseases is extremely effective in preventing their rapid progression in adulthood.

The second group is transient metabolic disorders. They are caused by a delay in the maturation of certain enzyme systems by the time the child is born or by too early contact with a substance that is normally tolerated by children at an older age. We define these as diseases, conditions or reactions of maladaptation.

Children suffering from delayed development of enzyme systems usually cannot cope with the food load that most children tolerate. One of these transient disorders is, for example, transient lactase deficiency, which manifests itself in frequent loose stools of an acidic reaction and foamy appearance in the first 1/2-2 months of life. At the same time, children gain weight normally and do not have any visible deviations. Usually, by 2-3 months, the stool is normalized, and even, on the contrary, the child suffers from constipation. Such conditions usually do not require the approaches necessary for genetically determined lactase deficiency. In some children in the first days of life, transient hyperphenylalaninemia occurs when breastfeeding, which disappears as the child grows. This is a group of predominantly somatic disorders that are not hereditary. They can be interpreted as "critical states of development", as a physiological basis for reactions or states of maladaptation.

The third group - syndromes of metabolic disorders that occur during various diseases or persist for some period after the disease (for example, malabsorption syndrome after intestinal infections). This is the most numerous group that the doctor encounters. Among them, lactase and sucrose deficiency are often observed, causing a syndrome of prolonged (sometimes chronic) diarrhea after intestinal infections. Usually, appropriate dietary measures can eliminate these manifestations.

It is possible that there is a very significant genetic basis in such transient conditions, since they are not detected in every child, but the degree of expression of this genetic predisposition to metabolic disorders is significantly lower than with permanent food intolerance.