Respiratory chain enzymes in muscle of endurance athletes: Effect of L-carnitine

Huertas, Rosa; Campos, Yolanda; Díaz, Enrique; Esteban, Jesús; Vechietti, Leonardo; Montanari, Giussepe; D'Iddio, S; Corsi, Marco; Arenas, Joaquı́n

doi:10.1016/0006-291x(92)92355-2

Cited by 44 publications

(28 citation statements)

References 16 publications

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“…Carnitine is pivotal for the fetal organism because it seems to be an important stimulator of the mitochondrial respiratory chain (Huertas et al, 1992) and production of surfactant (Lohninger et al, 1990). Another issue is its potential role in energy metabolism.…”

Section: Discussionmentioning

confidence: 99%

Expression, Localization, and Function of the Carnitine Transporter Octn2 (Slc22a5) in Human Placenta

Grube¹,

Schwabedissen²,

Draber³

et al. 2004

Drug Metab Dispos

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ABSTRACT:L-carnitine is assumed to play an important role in fetal development, and there is evidence that carnitine is transported across the placenta. The protein involved in this transfer, however, has not been identified on a molecular level. We therefore characterized localization and function of the carnitine transporter OCTN2 in human placenta. Significant expression of OCTN2 mRNA was detected in human placenta applying real-time polymerase chain reaction technology. Confocal immunofluorescence microscopy using an antibody directed against the carboxy terminus of OCTN2 protein revealed that it is predominantly expressed in the apical membrane of syncytiotrophoblasts. This was confirmed by the costaining of organic anion-transporting polypeptide B and MRP2, which are known to be expressed mainly in the basal and apical syncytiotrophoblasts membrane, respectively. To further support this finding, we performed transport studies using basal and apical placenta membrane vesicles. We could demonstrate that the carnitine uptake into the apical vesicles was about eight times higher compared with the basal ones. Moreover, this uptake was sodiumand pH-dependent with an apparent K m value of 21 M and inhibited by verapamil, which is in line with published data for recombinant OCTN2. Finally, experiments using trophoblasts in cell culture revealed that expression of OCTN2 paralleled human choriogonadotropin production and thus is modulated by cellular differentiation. In summary, we show expression and function of OCTN2 in human placenta. Moreover, several lines of evidence indicate that OCTN2 is localized in the apical membrane of syncytiotrophoblasts, thereby suggesting a major role in the uptake of carnitine during fetal development.Carnitine plays an important physiological role, in particular, in ␤-oxidation because it facilitates long-chain fatty acid transport across the inner mitochondrial membrane. Moreover, carnitine is involved in intracellular coenzyme A homeostasis and functions as an antioxidant (Bremer, 1983;Arduini et al., 1992;Pons and De Vivo, 1995). Only a few organs like brain, liver, and kidney have the ability to biosynthesize carnitine (Bremer, 1983), whereas other tissues like skeletal and heart muscles, where ␤-oxidation plays a major role in energy metabolism, are highly dependent on active carnitine uptake from blood to maintain their carnitine steady-state concentration (Siliprandi et al., 1989).Recent studies describe the organic cation transporter novel type II (OCTN2) as a high affinity uptake system for carnitine. The OCTN2 cDNA codes for 557 amino acids consisting of 12 putative transmembrane domains with a predicted molecular mass of 63 kDa . The transport of carnitine is sodium-dependent (Tamai et al., 1998), whereas other compounds such as tetraethylammonium are transported by OCTN2 in a sodium-independent way (Ohashi et al., 2001).Besides its physiological function, OCTN2 is of pharmacological relevance. Drugs like verapamil, pyrilamine, and ␤-lactam antibiotics have been characte...

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Section: Discussionmentioning

confidence: 99%

Expression, Localization, and Function of the Carnitine Transporter Octn2 (Slc22a5) in Human Placenta

Grube¹,

Schwabedissen²,

Draber³

et al. 2004

Drug Metab Dispos

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show abstract

“…On the other hand, long-term administration of L-carnitine over months has been shown to improve physical performance and to be associated with a trophic effect on skeletal muscle in patients on long-term hemodialysis [27,28] or suffering from peripheral arterial disease [29]. Furthermore, longterm administration of L-carnitine to endurance athletes was associated with increased activities of some mitochondrial enzymes, compatible with mitochondrial proliferation [30,31]. Although studies in patients with chronic hemodialysis [32] or aged mice [33] suggest that long-term administration of L-carnitine can increase the skeletal muscle or heart carnitine content, this has so far not been studied in healthy human subjects.…”

Section: L-carnitine and Physical Performancementioning

confidence: 99%

<i>L</i>-Carnitine, a ‘Vitamin-Like Substance’ for Functional Food. Proceedings of the Symposium on <i>L</i>-Carnitine, April 28 to May 1, 2000, Zermatt, Switzerland

Walter¹,

Schaffhauser²

2000

Ann Nutr Metab

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“…Consistently the large majority of studies observed a beneficial effect of L-carnitine supplementation on maximum oxygen uptake or respiratory quotient in healthy athletes [88] whereas only a minority of studies failed to observe such effects [88]. In particular, several scientific reports highlight that carnitine supplement could be an ergogenic aid for endurance exercise [89,90] as in presence of concomitant low carnitine concentration in skeletal muscle limiting carnitine acyltransferases to operate at a high rate, the oral ingestion of carnitine would result in an increase of the total carnitine concentration. This effect may be followed by increased rate of oxidation of intramuscular fatty acids and triacylglycerols during exercise thus reducing muscle glycogen breakdown and postponing fatigue appearance [88].…”

Section: Carnitinementioning

confidence: 83%

Nutritional Interventions as Potential Strategy to Minimize Exercise-Induced Muscle Injuries in Sports

D’Antona¹

2013

Muscle Injuries in Sport Medicine

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Respiratory chain enzymes in muscle of endurance athletes: Effect of L-carnitine

Cited by 44 publications

References 16 publications

Expression, Localization, and Function of the Carnitine Transporter Octn2 (Slc22a5) in Human Placenta

Expression, Localization, and Function of the Carnitine Transporter Octn2 (Slc22a5) in Human Placenta

<i>L</i>-Carnitine, a ‘Vitamin-Like Substance’ for Functional Food. Proceedings of the Symposium on <i>L</i>-Carnitine, April 28 to May 1, 2000, Zermatt, Switzerland

Nutritional Interventions as Potential Strategy to Minimize Exercise-Induced Muscle Injuries in Sports

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