The term "metabolism", in the context of metabolic abnormalities, implies a set of processes of cleavage of basic nutrients - proteins, fats and carbohydrates. In this article, violations of the metabolism of carbohydrates and proteins are examined.
Carbohydrates
Carbohydrates are molecules consisting of carbon, hydrogen and oxygen. There are simple and complex carbohydrates. Simple carbohydrates are represented by sugars, which are divided into mono- and disaccharides. The most important of the simple carbohydrates is glucose monosaccharide. Complex carbohydrates, or polysaccharides, such as starch, have a more complex structure. To assimilate in the digestive tract, all carbohydrates entering the food should be split to simple sugars.
Proteins
Proteins are large molecules consisting of chains of amino acids. Each protein has a unique structure, having its own sequence of amino acids. Normally, in the process of metabolism, large protein molecules are split into their constituent amino acids. These amino acids are used by the body as a source of energy or are involved in the synthesis of other proteins.
Enzyme systems
The process of splitting carbohydrates and proteins depends on the full functioning of the enzyme systems of the body. With a deficiency of even one enzyme, the metabolic process is disrupted, which is observed, for example, in congenital metabolic disorders. There are many types of metabolic disorders, but they are all quite rare.
Heredity
Congenital metabolic disorders refer to genetic diseases and are usually inherited in an autosomal recessive manner. At the same time for the development of the disease it is necessary that the child receives two defective genes: one from the father and one from the mother.
Diagnostics
Metabolic disorders can be diagnosed in the prenatal period, immediately after birth or in older children. It is possible to suspect the diseases of this group before the birth of the child, if the family had cases of metabolic disorders.
Symptoms in newborns
Infants with congenital metabolic disorders usually look painful already in the first weeks of life. They often do not suck well, are sleepy and sluggish, even to a coma. In some cases, convulsions develop. These signs are not specific for this group of diseases. A characteristic feature of patients with congenital metabolic disorders is an unusual smell of the skin.
Symptoms in older age
If the disorder is diagnosed at an older age, it is likely that the child has a mild degree of disease. Such children have similar signs of the disease, as in infancy, as well as mental retardation and physical development. Other symptoms include vomiting, convulsions and coma. The main violations of the metabolism of carbohydrates are galactosemia and glycogenoses. These diseases with similar symptoms are associated with a defect in the synthesis of enzymes. Treatment consists in the appointment of a special diet. Galactosemia is a hereditary disorder of carbohydrate metabolism. Monosaccharide galactose is a part of lactose - the main carbohydrate component of breast milk and milk mixtures.
Influence of enzyme deficiency on the body
With galactosemia, there is a deficiency of the key enzyme of metabolism - galactose-1-phosphaturidyl transferase. In its absence, the process of converting galactose to glucose (the main source of energy for the body) is disrupted. Children with galactosemia have a high level of galactose in the blood and a tendency to a critical decrease in glucose levels. This disease can be inherited from both the mother and the father.
Symptoms
Children with galactosemia at birth do not differ from healthy peers, but their condition begins to worsen after the beginning of feeding (breast or bottle). The following symptoms develop:
- jaundice (skin and sclera of the eyes acquire a yellow color);
- enlargement of the liver;
- liver failure.
Treatment and prognosis
Treatment consists in the appointment of a lactose-free and gluten-free diet. Early treatment will help prevent the development of chronic liver failure and other complications, such as developmental delay and cataract. However, despite adherence to the necessary diet from an early age, children with galactosemia often have learning difficulties. Glycogen is the main form of energy storage in the human body. Its large molecule consists of smaller glucose molecules connected together. When the body needs glucose as a source of energy, it is released from glycogen under the influence of certain hormones. Stocks of glycogen are found in the muscles and liver.
Enzymatic defects
With glycogenoses there is a violation of the processes of glycogen storage, which leads to the lack of glucose stores. There are several types of defects in enzyme systems that lead to the development of glycogenases. Depending on the synthesis of which enzyme is broken, the disease can be accompanied by
damage and weakness of the muscles, damage to the liver or heart. In such children, there is a possibility of a critical reduction in blood glucose (hypoglycemia).
Tactics of treatment
Children with glycogenosis require continuous 24-hour treatment to prevent a critical reduction in blood glucose levels. They must often be fed. Infants who can not normally swallow food are fed through a nasogastric tube (a tube that is inserted into the stomach through the nose). Nasogastric tube can also be needed for children who need carbohydrate food during sleep with a tendency to lower blood glucose levels. Older children are prescribed dietary treatment with corn starch (a complex carbohydrate consisting of various simple sugars). This ensures a slower flow of glucose into the blood and maintenance of its level within the norm. Congenital malformations of protein metabolism are rare, but they can have a significant effect on the child's body. The most common of these are phenylketonuria, tyrosinemia, homocystinuria and valinoleucinuria. There are many types of congenital disorders of protein metabolism. The most common of these are phenylketonuria, tyrosinemia, homocystinuria and valinoleucinuria.
Phenylketonuria
Phenylketonuria is a disease characterized by deficiency of the enzyme phenylal-ninhydroxylase. Frequency of occurrence of phenylketonuria is from 1:10 000 to 1:20 000 live births. It is one of the most common metabolic disorders, but its incidence is low enough.
Enzyme insufficiency
Enzyme deficiency in phenylketonuria leads to an increase in the blood level of the amino acid phenylalanine and its metabolites - phenylketones. They appear in the patient's urine (hence the name of the disease). Phenylalanine is also found in breast milk, however, so that its blood level in the child's blood rises to a clinically significant level, it takes four to five days of breastfeeding. In many countries, newborns are screened for this pathology a week after birth. A blood sample is taken from the heel of the child for laboratory analysis.
Dietotherapy
While maintaining a low level of phenylalanine in the blood, a child can normally grow and develop. A diet with the exception of phenylalanine is the preferred method of treatment, and it must be adhered to throughout life. In the absence of treatment, these children develop a severe form of epilepsy, the so-called infantile spasms, a delay in physical and mental development. They have a significantly lower IQ than their peers, although the degree of learning can vary. Tyrosinemia is a rare disease. Like most of the disorders of protein metabolism, it develops when the child passes the defective genes from both parents. Tyrosinemia occurs about 10 times less frequently than phenylketonuria. The disease is characterized by a deficiency of the fumaryl acetoacetase enzyme and is accompanied by an increase in the level of amino acid tyrosine and its metabolites in the blood.
Symptoms
In patients with tyrosinemia, renal and hepatic insufficiency develops. Especially quickly it is manifested in infants with severe disease. Less severe forms are characterized by chronic impairment of liver and kidney function. Most children with tyrosinemia subsequently develop hepatoma (a liver tumor).
Treatment
Therapeutic diet with the restriction of products containing tyrosine, and the use of food additives improves the patient's blood picture. However, the diet can not prevent liver damage. In most cases, patients require liver transplantation. Until recently, this operation was the only effective method of treatment. However, medicines are currently being developed that can prevent the development of liver failure and liver tumors. Homocystinuria is a severe metabolic disorder, manifested in infancy. The disease is characterized by a deficiency of the cystathione synthetase enzyme. Homocystinuria is extremely rare - approximately 1 in 350,000 newborns.
Characteristic
Children with homocystinuria may have:
- violation of physical development;
- lack of body weight;
- mental retardation with low IQ;
- propensity to convulsions;
- dislocation (subluxation) of the lens of the eye;
- unusually tall stature and long fingers.
Homocystinuria is accompanied by an increased risk of myocardial infarction and stroke. There can also be a characteristic shuffling gait (the so-called walk of Charlie Chaplin). Some children develop epileptic seizures. About half of patients with homocystinuria respond well to vitamin B (pyridoxine) treatment, which increases the activity of the defective enzyme. This vitamin is found in meat, fish and whole grains, but it is needed in much higher doses than can be obtained with food. If therapy with vitamin B is ineffective, a diet with restriction of products containing the amino acid methionine and an increased content of another amino acid, cysteine, is prescribed. Valinooleucinuria is a rare disorder in the metabolism of amino acids. It occurs in 1 case per 200,000 newborns. The disease is characterized by an increase in the level of amino acids with a branched chain.
Symptoms
The disease has many symptoms. Its distinctive feature is the smell of maple syrup of urine. Valynoleucinuria is characterized by the following symptoms: a painful appearance of the child; convulsions; more acidic blood reaction than normal, the tendency to a critical reduction in blood sugar levels. If the diagnosis is made in the first day of life, a favorable prognosis is possible. Nevertheless, many children with valinoleucinuria die at an early age. Survivors may have abnormalities in the development of the brain and often experience learning difficulties.