What is a Protein Metabolism Disorder?
Protein is an important nutrient found in many foods we consume, including meat, milk and dairy products, eggs, legumes and cereals. Proteins that are taken into the body through food are broken down into units called “amino acids” during digestion. Then, these amino acids are processed by some “enzymes” produced in the body and made usable by the body.
However, these events cannot occur in individuals with protein metabolism disorders. Because of an innate error in the genes of these patients, these enzymes that convert amino acids are either not produced at all or are produced in a non-working form. For this reason, these amino acids taken with food cannot be converted by the body. As a result, either the amino acids themselves, which can not be converted by enzymes, or their toxic residues begin to accumulate in body fluids and blood, causing permanent destruction of the brain, nervous system and organs.
The method of treatment for all disorders of protein metabolism is based on the exclusion from the daily diet of amino acids that cannot be converted by the body. In other treatment methods, it is aimed to give the missing enzyme from the outside or to ensure that the missing substances that cause the enzyme to work incorrectly are added to the diet and the enzyme functions. These treatment methods, which are alternatives to nutrition therapy, do not give results in all patients or cannot completely eliminate diet therapy. Studies on “gene therapy”, based on the repair of the gene responsible for the error-free production of the enzyme, are quite limited and there is no accepted method yet. Disorders of protein metabolism are classified into 3 types:
*** Amino Acid Metabolism Disorders ***
WHAT IS HOMOCYSTINURIA?
A disorder in the metabolism of “metinonin”, an amino acid that is taken into the body with food, is called “Homocystinuria”. In these individuals, the enzyme that will convert an amino acid called “methionine” into another amino acid called “cysteine” cannot be produced correctly. Since methionine amino acid cannot be converted, its density begins to increase in the blood.
HOW IS THE TREATMENT APPLIED?
* Methionine-restricted diet therapy is applied. There is no exchange of nutrients.
* The amino acid cysteine is added to the diet.
* Vitamins B6, B12, folic acid and choline are added to the diet.
* In patients with signs of anemia, the mineral “Iron” is added to the diet.
* Formula foods that do not contain meitonin; contain plenty of cysteine, vitamins and minerals are used.
WHAT IS Maple Syrup Urine Disease (MSUD)?
In this metabolic disorder, called the smell of maple syrup in the urine, enzymes that process amino acids called “leucine”, “isoleucine” and “valine” cannot be produced. Therefore, since these amino acids cannot be converted, they begin to accumulate in body fluids. If left untreated, MSUD can lead to seizures, coma, and death.
The most common and severe form of the disease is the classical type, which occurs shortly after birth. Variant forms occur in infancy and childhood and are typically milder. But if it is not treated, health problems arise.
HOW IS THE TREATMENT APPLIED?
*Requires diet therapy with restriction of amino acids ”Valine“, ”leucine“, ”isoleucine".
* The diet is adjusted according to the amino acid "leucine". The patient's “isoleucine” and “valine” values are checked. If the values are low, these amino acids are added to the food in powdered form.
* There is no unloading diet. The disease shows too rapid results to respond to the unloading diet.
*In some types, the addition of vitamin B1 to the diet increases dietary tolerance.
WHAT IS TYROSINEMIA?
It is a disorder of amino acid metabolism called ”tyrosine". The amino acid tyrosine is the building block of most proteins. They are converted with the help of enzymes secreted from the liver and used for various events in the body. The disease is caused by the inability to produce these enzymes. The increased density of tyrosine and its derivatives in the blood causes serious health problems. 40% of patients without treatment develop liver cancer.
There are three types.
Type 1 is the most severe and most common form of tyrosinemia disorder. It is caused by incomplete or incorrect production of an enzyme called “fumaryl acetoacetate hydroxylase”, which converts the amino acid tyrosine. It poses vital risks if not controlled.
Type 2 is caused by a deficiency of the enzyme “transaminase””, which converts the amino acid tyrosine. Mental disability occurs in about 50% of type 2 individuals.
Type 3 is the rarest form of the disorder Tyrosinemia. It can be seen temporarily in 10% of newborns. This condition is not genetic. The most common cause is a lack of vitamin C, which occurs due to premature birth, or liver enzymes that have not yet matured.
HOW IS THE TREATMENT APPLIED?
*Diet therapy is performed with a restriction of the amino acid tyrosine.
*Phenylalanine and tyrosine-restricted, vitamin and mineral-rich formula foods are used.
* It is important to supplement the diet with vitamins and minerals. In particular, Vitamin D, folic acid and Vitamin K should be added to the diet.
*In dietary therapy, the amino acid “phenylalanine" is also limited. Because the amino acid phenylalanine is converted into tyrosine with the help of liver enzymes.
***Organic Acidemia Disorders ***
What Is Propionic Acidemia and Methyl Malonic Acidemia (MMA)?
The amino acids “isoleucine”, “valine”, “threonine” and “methionine”, which are the protein building blocks, are converted into a substance called “propionic acid” with the help of an enzyme called ”Propioyl CoA Carboxylase”. However, in individuals with Propionic Acidemia, this conversion does not occur because this enzyme is produced insufficiently. 50% of this substance, which is necessary for various events in the body, is produced through this transformation. Since this transformation does not occur, toxic residues of these amino acids accumulate in the blood, causing permanent damage to the brain and organs.
Similarly, in individuals with Methyl Malonic Acidemia (MMA), the amino acids “isoleucine”, “valine”, “threonine” and “methionine” cannot be used correctly by the body. Toxic versions of these unavailable amino acids begin to accumulate in body fluids.
HOW IS THE TREATMENT APPLIED?
Similar treatment is applied for both ailments:
*Requires lifelong diet therapy. Total protein intake is limited. The diet is limited to the amino acids ”isoleucine“, ”valine“, ”threonine“ and”methionine
* The patient undergoes dialysis at certain intervals.
* Formula foods are used. These foods contain amino acids and vitamins and minerals that are necessary for the body, limited by the amino acids mentioned.
*Substances such as “carnitine” and “biotin” are added to the diet.
What Is Isovaleric Acidemia?
”Leucine" is a disorder of amino acid metabolism. In patients with isovaleric acidemia, the amino acid called “leucine”, which is taken into the body with food, cannot be processed correctly, and a substance called “isovaleric acid” is formed. This substance accumulates in the blood and body fluids, causing damage to the nervous system, especially to the brain.
How is the Treatment Applied ?
* Restricted diet therapy is applied from the amino acid "Leucine“
* Formula foods are used. These foods are limited in amino acid ”leucine", they contain amino acids necessary for the body, as well as vitamins and minerals.
* It has been observed that the addition of substances called “glycine” and “carnitine” to the diet reduces the symptoms.
***Urea Cycle Defects***
What Is Hyperammonemia and Citrulinemia?
“Nitrogenous substances” that are formed during the digestion of amino acids taken into the body through nutrients are converted into a substance called “urea” through a series of chemical events that occur in the liver. But in individuals with Hyperammonemia and Citrulinemia, this transformation does not occur due to genetic damage, and the “Ammonia” that occurs during these chemical events begins to accumulate in the blood. Ammonia is an extremely toxic substance, and if its density in the blood is not reduced, it can cause permanent damage to the brain and nervous system and even death.
HOW IS THE TREATMENT APPLIED?
* Protein-restricted diet therapy is applied.
* The patient is taken to dialysis at certain intervals. Excess ammonia in the blood is excreted outside.
* Formula foods are used. These foods contain tyrosine, cystine amino acids and vitamins and minerals.
Gülşah Kurtoğlu
Food Engineer