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Questions and Answers
What is the predominant stereoisomer of lactate produced in the human body?
Which mechanism allows the liver to process lactate?
What condition is indicated when serum lactate concentration exceeds 4 mmol/L?
In which of the following conditions is lactic acidosis NOT a potential consequence?
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Which organ contributes approximately 10 to 20% of total lactate metabolism?
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What is the pH threshold indicating acidemia in the context of lactic acidosis?
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What reaction catalyzes the conversion of pyruvate into lactate under anaerobic conditions?
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Which of the following is NOT a known deficiency that can lead to lactic acidosis?
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Study Notes
Lactic Acid Production
- L-lactate is the predominant stereoisomer among the two types of lactic acid, alongside D-lactate.
- Key substrates for intracellular L-lactate production include glucose and alanine via transamination mediated by alanine aminotransferase (ALT).
- In anaerobic conditions, pyruvate is reduced to lactate by lactate dehydrogenase (LDH) when the citric cycle is saturated.
Lactate Metabolism
- The liver is primarily responsible for converting lactate to glucose through gluconeogenesis in the Cori cycle, consuming 6 ATP molecules.
- The kidneys play a role in lactate removal, handling approximately 10 to 20% through excretion, gluconeogenesis, and oxidation.
- Other tissues can oxidize lactate to carbon dioxide and water, whereas only the liver and kidneys possess the necessary enzymes for lactate-to-glucose conversion.
Lactic Acidosis
- Lactic acidosis manifests when lactic acid production outpaces its clearance, characterized by:
- Serum lactate concentration exceeding 4 mmol/L (normal range: 0.5 – 1.5 mmol/L).
- Acidemia indicated by serum pH below 7.35.
Causes of Lactic Acidosis
- Inborn metabolic disorders linked to lactic acidosis include:
- Glucose-6-phosphatase deficiency (von Gierke disease, glycogen storage disease type I).
- Fructose-1,6-bisphosphatase deficiency.
- Pyruvate carboxylase deficiency.
- Pyruvate dehydrogenase deficiency.
- Oxidative phosphorylation deficiencies.
- Methylmalonic aciduria.
- MELAS syndrome is a neurodegenerative disorder caused by mutations in mitochondrial DNA, associated with lactic acidosis and strokes.
- Lactic acidosis can also arise from various conditions, including:
- Diabetes mellitus.
- Alcoholic ketoacidosis.
- Severe iron-deficiency anemia.
- Liver diseases and renal failure.
- Pancreatitis and short gut syndrome.
- Infections such as malaria and cholera.
- Certain malignancies, e.g., leukemia, lymphoma, lung cancer.
- Thiamine deficiency and carbohydrate malabsorption syndromes.
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Description
Explore the processes of lactic acid production, metabolism, and the implications of lactic acidosis. Understand the roles of key organs and enzymes in managing lactate levels in the body. This quiz covers essential biochemical concepts related to lactic acid and its effects on human health.
