Metabolic Fate of Dietary Carnitine in Human Adults: Identification and Quantification of Urinary and Fecal Metabolites

• Published in: The Journal of nutrition Vol. 121; no. 4; pp. 539 - 546
• Main Authors: Rebouche, Charles J., Chenard, Catherine A.
• Format: Journal Article
• Language: English
• Published: Bethesda, MD Elsevier Inc 01.04.1991; American Society for Nutritional Sciences
• Subjects: absorption; administration & dosage; Adult; adulte; adultos; adults; aminas; amine; AMINES; AMINO ACIDS; AMMONIUM COMPOUNDS; analogs & derivatives; analysis; ANIMALS; balance studies; BASIC BIOLOGICAL SCIENCES; BETAINE; Betaine - analogs & derivatives; Betaine - analysis; bioavailability; Biological and medical sciences; BIOLOGICAL MATERIALS; BIOLOGICAL WASTES; Biotransformation; CARBOXYLIC ACIDS; carnitina; CARNITINE; Carnitine - administration & dosage; Carnitine - pharmacokinetics; Carnitine - urine; chemistry; Chromatography, Ion Exchange; COUNTING TECHNIQUES; diagnostic use; DIET; dieta; disponibilidad de nutrientes; DRUGS; element nutritif disponible; Enzymes. Coenzymes. Vitamins. Pigments; excrecion; excretion; experimental diets; experimentation; experimentos; experiments; faeces; FECES; Feces - chemistry; Fundamental and applied biological sciences. Psychology; heces; hombres; homme; Humans; HYDROGEN COMPOUNDS; HYDROXY ACIDS; ISOTOPE APPLICATIONS; isotope labeling; L-carnitine; LIPOTROPIC FACTORS; Male; MAMMALS; MAN; MATERIALS; men; METABOLISM; metabolisme; metabolismo; Metabolisms and neurohumoral controls; metabolite; METABOLITES; metabolitos; Methylamines; Methylamines - analysis; nutrient availability; ORAL ADMINISTRATION; ORGANIC ACIDS; ORGANIC COMPOUNDS; orina; pharmacokinetics; PRIMATES; QUATERNARY COMPOUNDS; regime alimentaire; SCINTILLATION COUNTING; technique des traceurs; tecnicas de trazadores; TRACER TECHNIQUES; trimethylamine; trimethylamine N-oxide; Tritium; TRITIUM COMPOUNDS; urine; VERTEBRATES; Vertebrates: anatomy and physiology, studies on body, several organs or systems; VITAMIN B GROUP; VITAMINS; WASTES 550501 > Metabolism > Tracer Techniques; γ-butyrobetaine; L-carnitine; trimethylamine N-oxide; absorption; humans; γ-butyrobetaine; Human; Excretion; Absorption; Diet; Metabolite; Vitamin; Metabolism; Feeding; Carnitine
• ISSN: 0022-3166; 1541-6100
• DOI: 10.1093/jn/121.4.539

Results of kinetic and pharmacokinetic studies have suggested that dietary carnitine is not totally absorbed and is in part degraded in the gastrointestinal tract of humans. To determine the metabolic fate of dietary carnitine in humans, we administered orally a tracer dose of [methyl-3H]L-carnitine with a meal to subjects who had been adapted to a low-carnitine diet or a high-carnitine diet. Urinary and fecal excretion of radiolabeled carnitine and metabolites was monitored for 5 to 11 d following administration of the test dose. Total radioactive metabolites excreted ranged from 13 to 34% (low carnitine diet) and 27 to 46% (high carnitine diet) of the ingested tracer. Major metabolites found were [3H]trimethylamine N-oxide (8 to 39% of the administered dose; excreted primarily in urine) and [3H]γ-butyrobetaine (0.09 to 8% of the administered dose; excreted primarily in feces). Urinary excretion of total carnitine was 42 to 95% (high carnitine diet) and 190 to 364% (low carnitine diet) of intake. These results indicate that oral carnitine is 54 to 87% bioavailable from normal Western diets; the percentage of intake absorbed is related to the quantity ingested.