metabolic disease
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What is a metabolic disease?
Metabolic diseases disrupt normal metabolism, the process of converting food to energy at the cellular level. These diseases affect the ability of cells to process proteins, carbohydrates, or lipids due to dysfunctional enzymes in metabolic pathways.
Most metabolic diseases are hereditary, often appearing after a period of seemingly good health, with symptoms triggered by stress on the body, such as during prolonged fasting or illness. These diseases, as a group, are relatively common, affecting approximately 1 in 1,000 individuals. Individually, specific metabolic disorders range in incidence from approximately 1 in 500 to fewer than 1 in 1,000,000.
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What does 'pathology' mean in the context of metabolic diseases?
In the context of metabolic diseases, pathology refers to the study of the causes and effects of these diseases, focusing on disrupted metabolism at the cellular level. Metabolic diseases involve the disruption of normal metabolism, which is the process of converting food into energy.
These diseases, often hereditary, impact the cell's ability to perform biochemical reactions that involve the processing or transport of proteins, carbohydrates, or lipids. A key aspect of pathology in this context is identifying defects in specific biochemical pathways, often due to enzyme deficiencies, which can lead to the accumulation of toxic substrates and disruption of normal metabolic processes.
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How can metabolic diseases affect how the body uses energy and nutrients?
Metabolic diseases disrupt normal metabolism, which is the process of converting food into energy at the cellular level. These diseases impair the body's ability to process or transport proteins, carbohydrates, or lipids.
These diseases often stem from defects in specific biochemical pathways, resulting from diminished activity or the absence of particular enzymes. When an enzyme is deficient, the metabolic pathway becomes blocked, causing a deficiency in the final product and the accumulation of the enzyme's substrate, potentially at toxic levels. This imbalance can lead to various health issues, including intellectual disability, seizures, and organ failure.
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What are some common examples of metabolic diseases?
Metabolic diseases disrupt normal metabolism, which is the process of converting food to energy at the cellular level. These diseases impair the ability of cells to perform critical biochemical reactions that involve processing or transporting proteins, carbohydrates, or lipids.
Common examples of metabolic diseases:
* Phenylketonuria (PKU) PKU is a hereditary condition where the body can't metabolize the amino acid phenylalanine.
* Gout Gout results from the accumulation of uric acid within the tissues, which is an end product of nucleic acid metabolism.
* Type 2 Diabetes This late-onset diabetes results from impaired insulin release and reduced responsiveness of body tissues to insulin, leading to an inability to properly metabolize sugars and fats.
* Lysosomal storage diseases These are genetic disorders where a mutation affects the activity of acid hydrolases. This blocks the normal metabolism of macromolecules, causing them to accumulate inside lysosomes.6 Britannica SourcesCreated from Britannica articles using AI. AI can make mistakes, so verify using Britannica articles. -
How do doctors diagnose metabolic diseases?
Doctors diagnose metabolic diseases through a variety of methods, including biochemical tests, which utilize techniques such as chromatography, electrophoresis, and enzymatic analysis to measure metabolites in blood and urine. Newborn screening programs use mass spectrometry to detect multiple disorders from blood samples, facilitating early intervention before severe developmental issues arise.
Genetic testing is also employed to identify genetic mutations that cause metabolic disorders and can be used to assess high-risk fetuses. Urinalysis helps reveal metabolic disorders through deviations in urine color, concentration, and the presence of abnormal substances such as sugars and fats. Positron emission tomography (PET) is valuable for diagnosing certain degenerative and metabolic disorders by mapping the metabolic activity of the brain using radioisotopes.
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What are some ways pathology helps scientists understand and treat metabolic diseases?
Pathology aids in understanding and treating metabolic diseases by determining the causes and structural/functional changes in abnormal conditions. It involves examining surgically removed body parts, blood, and other fluids.
By studying metabolic pathways, scientists can describe chemical changes catalyzed by enzymes and intracellular controls governing pathway function. Analyzing accumulated metabolites, using metabolic poisons, and isotope labeling help identify intermediates and enzyme defects.
Genetic testing and newborn screening, facilitated by mass spectrometry, enable early diagnosis and treatment. Diet therapy, transplants, and gene therapy are potential treatments for inborn errors of metabolism.
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metabolic disease, any of the diseases or disorders that disrupt normal metabolism, the process of converting food to energy on a cellular level. Thousands of enzymes participating in numerous interdependent metabolic pathways carry out this process. Metabolic diseases affect the ability of the cell to perform critical biochemical reactions that involve the processing or transport of proteins (amino acids), carbohydrates (sugars and starches), or lipids (fatty acids).
Metabolic diseases are typically hereditary, yet most persons affected by them may appear healthy for days, months, or even years. The onset of symptoms usually occurs when the body’s metabolism comes under stress—for example, after prolonged fasting or during a febrile illness. For some metabolic disorders, it is possible to obtain prenatal diagnostic screening. Such analysis usually is offered to families who have previously had a child with a metabolic disease or who are in a defined ethnic group. For example, testing for Tay-Sachs disease is relatively common in the Ashkenazi Jewish population. Countries that perform screening for metabolic diseases at birth typically test for up to 10 different conditions. Tandem mass-spectrometry is a new technology that allows for the detection of multiple abnormal metabolites almost simultaneously, making it possible to add approximately 30 disorders to the list of conditions for which newborns may be tested. If an infant is known to have a metabolic disorder soon after birth, appropriate therapy can be started early, which may result in a better prognosis. Some metabolic disorders respond very well if treatment is introduced at an early age. However, others have no effective therapy and cause severe problems, despite early diagnosis. In the future, gene therapy may prove successful in the treatment of some of these diseases.
Metabolic diseases are quite rare individually, but they are relatively common when considered as a group. Specific metabolic disorders have incidences ranging from approximately 1 in 500 (or even higher in isolated populations) to fewer than 1 in 1,000,000. As a group, it has been estimated that metabolic disorders affect approximately 1 in 1,000 individuals.
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The origins of metabolic disease
Metabolic pathways
In 1908 British physician Sir Archibald Garrod postulated that four inherited conditions of lifelong duration—alkaptonuria, pentosuria, albinism, and cystinuria—were caused by defects in specific biochemical pathways due to the diminished activity or complete lack of a given enzyme. He called these disorders “inborn errors of metabolism.” Although Garrod was incorrect in his categorization of cystinuria, his insights provided the field of biochemical genetics with a solid foundation, and the list of inherited inborn errors of metabolism has rapidly grown. This article is primarily concerned with these inherited metabolic diseases, although other disorders, including endocrine diseases (e.g., diabetes mellitus and hypothyroidism) and malnutrition (e.g., marasmus and kwashiorkor), also affect cellular metabolism.
Food is broken down in a series of steps by cellular enzymes (proteins that catalyze the conversion of compounds called substrates) into products with a different biochemical structure. These products then become the substrate for the next enzyme in a metabolic pathway. If an enzyme is missing or has diminished activity, the pathway becomes blocked, and the formation of the final product is deficient, resulting in disease. Low activity of an enzyme may result in the subsequent accumulation of the enzyme’s substrate, which may be toxic at high levels. In addition, minor metabolic pathways that usually lie dormant may be activated when a substrate accumulates, possibly forming atypical, potentially toxic, products. Each cell in the body contains thousands of metabolic pathways, all of which are interlinked to some extent, so that a single blockage may affect numerous biochemical processes.
The consequences of metabolic imbalance may be severe; intellectual disability, seizures, decreased muscle tone, organ failure, blindness, and deafness may occur, depending on which enzyme is dysfunctional. In recent years, it has become apparent that even some conditions associated with multiple congenital anomalies (e.g., Smith-Lemli-Opitz syndrome) have an underlying metabolic cause.