Glutamic acid is an amino acid that builds proteins in our body. At the same time, it is the most important excitatory neurotransmitter in the nervous system. Learning and remembered processes depend on its activity. At the same time, its too high concentration kills nerve cells. What other role does glutamic acid play in the body?

Glutamic acidis usually found in the body in the form of an anion called glutamate. This compound is an amino acid, i.e. the basic organic building block from which proteins are made. At the same time, it is one of the most important neurotransmitters. This term covers substances that are involved in the transmission of information between nerve cells. This substance is believed to be the most important compound involved in the formation of the memory trace in the brain. For this reason, its presence is essential in the process of learning and remembering events.

Excessive concentration of glutamic acid in the central nervous system is not beneficial, however. It damages the nerve cells. There are studies showing that the toxicity of high levels of glutamate is involved in the formation of damage to areas of the brain during Alzheimer's disease. These changes lead to disturbances in cognitive processes.

Glutamic acid is very often associated with chemical food additives. This is due to the fact that its s alt, i.e. monosodium glutamate, is a flavor enhancer added to dishes and spice mixtures. It is one of the most popular chemicals used in the food industry. Monosodium glutamate is officially not recognized as a harmful substance in the European Union.

Glutamateis a protein component and is therefore a common food component. Its taste is felt only when it is not bound in protein. An example of a food that contains glutamic acid is soy sauce. The sensation of taste that this chemical produces has been called "umami".

Glutamic acid as an amino acid

Glutamate is chemically an amino acid. This name means that it has a carboxylic acid group and an amino group in its structure, placed at one carbon atom. Amino acids linked together by chemical bonds, lined upin a long chain, they make up all existing proteins.

Glutamic acid is an endogenous amino acid, i.e. one that can be synthesized by our body. Of course, its source can be proteins supplied with food. All meats, poultry, fish, eggs and dairy products are excellent sources of glutamic acid. Certain protein-rich plant foods can also be sources of protein. For example, gluten, the main protein in wheat, contains 30% to 35% glutamic acid.

Glutamic acid as a neurotransmitter

Glutamate, in addition to being involved in the formation of proteins, also acts as a neurotransmitter. This means that it is a substance released into the gap between two nerve cells. The entry of glutamate molecules from one nerve cell to receptors on the other causes excitation. Receptors are specialized protein structures that recognize a specific neurotransmitter.

Glutamic acid, used as a neurotransmitter, is produced directly by glutamatergic neurons. They make up the dominant part of the nerve cells found in the brain. Hence, the disruption of glutamic acid transmission has very serious consequences. It leads to neurological diseases and mental disorders.

Glutamic acid is stored in special vesicles that are located in synapses, i.e. in the endings of nerve cells that connect with each other. Nerve impulses trigger the release of glutamate into the synaptic cleft, which eventually triggers another neuron. Glutamate receptors, such as the NMDA receptor or AMPA, are responsible for receiving the information carried by this neurotransmitter. The connection of the glutamic acid molecule with the receptor causes its activation, and thus the transmission of the nerve impulse further.

Glutamate is the most common excitatory neurotransmitter in the nervous system of vertebrates, including humans. It is involved in cognitive functions in the brain, such as learning and memory. It is present at glutamatergic synapses in the hippocampus, neocortex, and other parts of the brain.

Balance between glutamate and gamma aminobutyric acid

Glutamic acid, as the main excitatory neurotransmitter, under physiological conditions occurs in equilibrium with the main inhibitory neurotransmitter, i.e. gamma aminobutyric acid (GABA). The appropriate relationship of these substances determines the proper functioning of the nervous system.

In the case of disease states, we will usually talk about an advantageglutamate mediated transmission over GABA. Such imbalance leads to psychotic states. There are theories linking overactivity of glutamic acid receptors with schizophrenia. For this reason, the search for psychotropic drugs that inhibit the glutamatergic system is ongoing.

Researchers with overactivity or decreased glutamate neurotransmission activity are associated with the following disorders:

  • anxiety
  • depression
  • schizophrenia
  • neurodegenerative diseases
  • bipolar disorder

Depression and the activity of glutamic acid

Scientists and doctors are unsure of the role of the glutamatergic system in depression. Some research studies suggest an increase in the activity of this neurotransmitter during this disease. Others show that glutamate transmission is inhibited.
Studies have shown that the use of drugs that block glutamate activity has a short-lasting antidepressant effect. An example of such a drug is ketamine, which is an anesthetic in surgery and veterinary medicine.

The effect of improving well-being also occurs in the case of bipolar disorder after administration of drugs from this group.

The drug riluzole has the ability to reduce the amount of glutamic acid released from neurons. Thus, it inhibits glutamatergic transmission. Studies have shown that this drug acts as an antidepressant in patients with this disorder.

The above-mentioned tests for drugs that inhibit the glutamatergic system suggest a strong correlation between its hyperactivity and depressive symptoms. Further research in this area may set a new direction in the treatment of depression and bipolar disorder.

Glutamic acid and schizophrenia

There is a hypothesis of the genesis of schizophrenia related to disturbances in glutamate activity. The theory was initially based on a set of clinical and neuropathological findings suggesting an underactive glutamatergic signaling via NMDA receptors. In later years, there were also genetic data supporting this thesis.

Current knowledge shows, however, that this disorder has both glutaminergic and dopaminergic abnormalities. They are part of a complex system of neurochemical, psychological, psychosocial, and brain-related factors that together contribute to schizophrenia.

Glutamic acid and Alzheimer's disease

Numerous studies have shown a link between the nephrotoxicity of high glutamate levels and dementia inthe course of Alzheimer's disease. These damages result from the influence of the excessive activation of receptors by this neurotransmitter. As a result, nerve cells are swollen and damaged.

Memantadine is administered to reduce the symptoms of Alzheimer's disease. This drug blocks glutamate receptors. Ultimately, excitation by this neurotransmitter is reduced, which leads to the inhibition of neurodegenerative processes.

Importance of glutamic acid for the future of medicine

We are currently exploring the importance of the glutamatergic system. An in-depth understanding of the mechanisms that govern it gives hope for the development of drugs effective in the treatment of mental and neurological disorders.

Research on glutamic acid, which is active in the human brain, is also a chance to understand how human memory works.

About the authorSara Janowska, MA in pharmacyPhD student of interdisciplinary doctoral studies in the field of pharmaceutical and biomedical sciences at the Medical University of Lublin and the Institute of Biotechnology in Białystok. A graduate of pharmaceutical studies at the Medical University of Lublin with a specialization in Plant Medicine. She obtained a master's degree defending a thesis in the field of pharmaceutical botany on the antioxidant properties of extracts obtained from twenty species of mosses. Currently, in his research work, he deals with the synthesis of new anti-cancer substances and the study of their properties on cancer cell lines. For two years she worked as a master of pharmacy in an open pharmacy.

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