Krebs Cycle Metabolites
Overview
Krebs cycle metabolites measure the concentrations of tricarboxylic acid (TCA) cycle intermediates such as citrate, alpha-ketoglutarate, succinate, fumarate, and malate in biological samples. These compounds are central to cellular respiration, linking carbohydrate, fat, and protein metabolism to the electron transport chain while also serving as precursors for amino acid, nucleotide, and lipid biosynthesis. Abnormal levels can indicate mitochondrial dysfunction, inborn errors of metabolism, cancer metabolic reprogramming, or systemic metabolic disorders. Clinically, Krebs cycle metabolite profiling is primarily used in research and specialized diagnostic settings to evaluate mitochondrial diseases and inherited metabolic disorders rather than as routine clinical tests.
Clinical Use Cases
- Diagnosing mitochondrial disorders and respiratory-chain defects.
- Evaluating inborn errors of metabolism affecting TCA cycle enzymes (e.g., alpha-ketoglutarate dehydrogenase deficiency).
- Research assessment of cancer metabolism and Warburg effect phenotypes.
- Monitoring nutritional status and metabolic reprogramming in critical illness.
Specimen Types
- Plasma.
- Serum.
- Urine (for organic acid analysis).
- Cerebrospinal fluid (for neurological presentations).
- Tissue biopsy (rarely, for definitive enzyme studies).
Measurement Methods
- Gas chromatography-mass spectrometry (GC-MS) for organic acids.
- Liquid chromatography-tandem mass spectrometry (LC-MS/MS) for targeted metabolite panels.
- Nuclear magnetic resonance (NMR) spectroscopy for metabolomic profiling.
- Capillary electrophoresis-mass spectrometry (CE-MS) in research settings.
Test Preparation and Influencing Factors
- Fasting preferred to minimize dietary effects on certain metabolites.
- Acute illness, fasting, or high-protein diets alter metabolite patterns.
- Sample handling critical: requires immediate freezing and acidification to prevent metabolite degradation.
- Hemolysis or delayed processing affects plasma metabolite stability.
Synonyms
- TCA cycle intermediates.
- Tricarboxylic acid cycle metabolites.
- Citric acid cycle metabolites.