Neuron-specific enolase – or NSE for short – is a biocatalyst (enzyme) of sugar metabolism. It is present in the body in diverse cells such as the peripheral and central nervous systems and in organ tissues. Elevated NSE levels in the blood and cerebrospinal fluid (CSF) can be detected, particularly in the case of disease. Therefore, cancer diagnostics uses the enzyme as an indicator of the presence of tumors.
What is neuron-specific enolase?
Neuro(nene)specific enolase (ENOG, NSE) is the medical/biochemical term for an enzyme responsible for glucose metabolism in the body. Also called phosphopyruvate hydratase, this biocatalyst occurs in three forms in the body, which have a similar mode of action and can even work together. NSE is found in the nerve cells (neurons) of the brain and peripheral nervous system, in neuroendocrine tissue, and also in cerebrospinal fluid. In many organs, such as the thyroid, lungs, gastrointestinal tract, and urinary tract, it is particularly present in apud cells. They are found in the pancreas, gastrointestinal tract, bronchi, urinary draining organs and cardiovascular system. Neuron-specific enolase controls glycolysis (sugar metabolism) in the body and can therefore also be detected in blood serum. In blood, it serves as an indicator for the presence of various diseases and even cancer. In cancer diagnostics, it serves as a tumor marker.
Function, effects, and roles
As a tumor marker, its function is to determine the type of cancer present (small cell carcinoma or non-small cell carcinoma) and its size. This is done by determining the level of NSE in the blood serum. If it is elevated, it indicates the presence of a disease or tumor in the body. Cancer diagnostics uses the enzyme neuron-specific enolase primarily to differentiate benign cancer cells from malignant ones. Since the biocatalyst prevents the breakdown of glucose (glycolysis) under the influence of fluorides, sugar levels can be determined in the laboratory. If the NSE value in the blood serum is elevated, this may indicate the presence of a health disorder and, in extreme cases, even cancer. However, elevated NSE values are also sometimes found in people with less serious complaints. If this is the case in a pregnant woman, neural tube damage in the child may be to blame for the abnormality. In tumor diagnostics, measuring the concentration of neurospecific enolase is the third and final step after microscopic detection of cancer cells and cancer tissue. Regular testing of the NSE value in cancer patients and other patients serves to monitor and evaluate the course of the disease and the success of the therapy. Prognosis is also possible on the basis of the values. Lower neuron-specific enolase values in the normal range after chemotherapy, for example, suggest that the patient’s treatment was successful. However, for tumor search and cancer prophylaxis, the determination of enzyme concentration is not suitable.
Formation, occurrence, properties, and optimal values
Neuron-specific enolase, as its name suggests, is formed in the neurons (nerve cells) of the brain and in endocrine tissue. There are a total of three emolase groups: Alpha emolase is tissue nonspecific, meaning it is found in all types of body tissue. Beta-enolase, on the other hand, is localized exclusively in muscle cells. Gamma enolase is predominantly found in nervous tissue. All enolase groups can also be detected in combinations. Thus, alpha/beta enolase can be detected alongside beta/beta enolase in striated muscle. Gamma/gamma enolase occurs alongside alpha/gamma enolase in nerves. All three enolase groups have a similar biochemical reaction mode. To measure the NSE value, blood is drawn from the patient and analyzed in the laboratory using the immunoassay. The biologically active substance is identified by the antigen-antibody reaction. The very accurate method allows measurements of even the smallest amounts. Depending on the laboratory commissioned and the measurement method chosen, the maximum NSE value in blood serum is 10 or 12.5 micrograms/liter. A limit value of 12.5 micrograms/liter (adults) is often used. For infants under one year of age, the enolase maximum value is 25 micrograms/liter.All NSE values exceeding 4 micrograms should be viewed critically, as they are an indication of the presence of brain and nerve tissue disease. However, only a slight increase in the value is not a cause for concern. Because the enzyme is present in high concentrations in red blood cells and platelets, even an error in centrifugation can cause the NSE value to rise.
Diseases and disorders
To find out whether a patient who has suffered a serious accident has brain damage, draw blood 24 hours after resuscitation and check the NSE level. A second blood draw and blood analysis is done after 48 hours. If the NSE value has normalized after 72 hours (third blood sample), the physician assumes that there is no permanent brain damage and that there is no further increase in the values. Elevated NSE levels are found in the rarely occurring Creutzfeldt-Jakob disease, the human counterpart of BSE, which occurs primarily in cattle. Brain injuries with intracerebral hemorrhage, meningitis, encephalitis, cerebral infarcts, and a brain disease associated with multiple sclerosis (encephalomyelitis disseminata) also cause NSE levels to rise above the normal range. The same is true for liver and lung diseases (pulmonary fibrosis, bronchopneumonia), circulatory and vascular diseases (stroke), and cancers (bronchial carcinoma, neuroblastoma, etc.).
