[L-carnitine: metabolism, functions and value in pathology]

Area of Science:

• Biochemistry and Metabolism
• Nutritional Science

Context:

• L-carnitine, vital for fatty acid transport into mitochondria for energy production, is synthesized endogenously but can be deficient in neonates, particularly premature infants.
• Dietary L-carnitine, primarily from animal sources, is well-absorbed, with lysine and methionine as key biosynthesis precursors.
• Carnitine homeostasis involves complex tissue exchange, muscle storage, and renal excretion, influenced by hormones and diet.

Purpose:

• To elucidate the physiological role of L-carnitine in energy metabolism and its implications in various deficiency states.
• To review the biosynthesis, absorption, distribution, and elimination pathways of L-carnitine in the human body.
• To categorize and discuss the causes and clinical manifestations of L-carnitine deficiencies, including myopathic and systemic types.

Summary:

• L-carnitine facilitates the transfer of long-chain fatty acids into mitochondria for beta-oxidation, regenerating coenzyme A and supporting energy metabolism.
• Carnitine deficiencies, classified as myopathic or systemic, are linked to impaired fatty acid oxidation and can arise from genetic factors, malnutrition, or specific diseases.
• Plasma L-carnitine levels may not reflect total body stores, and its metabolism is altered in conditions like diabetes, renal failure, and Reye's syndrome.

Impact:

• Understanding L-carnitine's role is critical for managing metabolic disorders and nutritional deficiencies, especially in vulnerable populations like premature infants.
• The study highlights the importance of L-carnitine in energy production and detoxification, with numerous supplementation trials indicating therapeutic potential.
• Accurate assessment of L-carnitine status requires consideration of tissue-specific levels beyond plasma concentrations, guiding clinical interventions.