Exogenous Carnitine Research Articles

Water stress and exogenous carnitine on growth and essential oil profile of Eryngium foetidum L.

The online version contains supplementary material available at 10.1007/s13205-023-03757-y.

Exogenous Carnitine Mitigates the Deleterious Effects of Mild-Water Stress on Arugula by Modulating Morphophysiological Responses

Exogenous Carnitine Mitigates the Deleterious Effects of Mild-Water Stress on Arugula by Modulating Morphophysiological Responses

Effect of Carnitine Supplementation in Pediatric Patients with Left Ventricular Dysfunction.

Carnitine is an essential amino acid involved in transporting fatty acids across the mitochondrial membrane. Fatty acids are a primary source of energy for the myocardium. Studies in adults demonstrated decreased carnitine levels in the ischemic myocardium, but subsequent exogenous carnitine supplementation showed improvement of myocardial metabolism and left ventricular function. However, only limited data regarding carnitine are available in pediatrics. A single-center retrospective, paired data study was conducted. Patients < 18years, left ventricular ejection fraction (LVEF) < 55% by echocardiography, and had received at least 7days of oral or intravenous carnitine supplementation between January 2018 and March 2021 are included in the study. Several endpoints and covariates were collected for each patient: before, one week after, one month after, and 6months after carnitine supplementation. Univariate analysis consisted of an analysis of variance (ANOVA), followed by an analysis of covariance (ANCOVA) to model LVEF while adjusting for other variables. 44 patients included in the final analyses. LVEF significantly improved from 50.5 to 56.6% (p < 0.01). When LVEF was adjusted for other interventions (mechanical ventilation, afterload reduction, diuretic therapy, spironolactone), the estimated means demonstrated a significant increase from 45.7 to 58.0% (p < 0.01). Free carnitine level increased significantly (p = 0.03), and N-terminal-pro-brain natriuretic peptide (p = 0.03), creatinine (p < 0.01), and lactate (p < 0.01) all significantly decreased over the study period. Carnitine supplementation in pediatric patients with left ventricular systolic dysfunction may be associated with an increase in LVEF and improvement in laboratory markers of myocardial stress and cardiac output.

Gut microbiota production of trimethyl-5-aminovaleric acid reduces fatty acid oxidation and accelerates cardiac hypertrophy

Numerous studies found intestinal microbiota alterations which are thought to affect the development of various diseases through the production of gut-derived metabolites. However, the specific metabolites and their pathophysiological contribution to cardiac hypertrophy or heart failure progression still remain unclear. N,N,N-trimethyl-5-aminovaleric acid (TMAVA), derived from trimethyllysine through the gut microbiota, was elevated with gradually increased risk of cardiac mortality and transplantation in a prospective heart failure cohort (n = 1647). TMAVA treatment aggravated cardiac hypertrophy and dysfunction in high-fat diet-fed mice. Decreased fatty acid oxidation (FAO) is a hallmark of metabolic reprogramming in the diseased heart and contributes to impaired myocardial energetics and contractile dysfunction. Proteomics uncovered that TMAVA disturbed cardiac energy metabolism, leading to inhibition of FAO and myocardial lipid accumulation. TMAVA treatment altered mitochondrial ultrastructure, respiration and FAO and inhibited carnitine metabolism. Mice with γ-butyrobetaine hydroxylase (BBOX) deficiency displayed a similar cardiac hypertrophy phenotype, indicating that TMAVA functions through BBOX. Finally, exogenous carnitine supplementation reversed TMAVA induced cardiac hypertrophy. These data suggest that the gut microbiota-derived TMAVA is a key determinant for the development of cardiac hypertrophy through inhibition of carnitine synthesis and subsequent FAO.

440-P: Dual Long-Term Effects of Free Fatty Acid on Human Endothelial Barrier In Vitro Are Mediated by NO, Mitochondrial ROS, and Dicarbonyl Stress

In diabetes-associated hyperlipidemia, free fatty acids (FFAs) are thought to induce insulin resistance and endothelial dysfunction leading to vascular injury and cardiovascular T2DM complications. However, evidence is scarce regarding the effects of FFA on vascular endothelial barrier. We used human umbilical vein endothelial cells (HUVEC) to model, in vitro, the endothelial barrier and reveal its responses to experimental hyperlipidemia induced by long-term treatment with palmitic acid in complex with albumin. Palmitate was continuously present in the growth medium at 0.8 mM to reproduce FFA levels typical for T2DM. We developed conditions to maintain the HUVEC monolayers in the presence of the high palmitate concentration for up to 2 weeks by adding exogenous carnitine to facilitate mitochondrial β-oxidation of FFA. In this model system, palmitate readily augmented the transendothelial electric resistance (TER) of HUVEC via increased NO production by endothelial NO-synthase (eNOS). Western blots showed that palmitate neither disturbed insulin signaling cascade towards eNOS nor upregulated eNOS expression. After the initial 3-4-day rise in TER, further treatment with palmitate led to barrier stabilization and attenuation as compared to FFA-free conditions. This later phase was associated with increased ROS and malondialdehyde (MDA) accumulation, both prevented by the mitochondria-targeted antioxidant SkQ1. Treatment of HUVEC with exogenous MDA impaired the TER and barrier suggesting that accumulation of MDA-modified proteins may contribute to the barrier dysfunction upon long-term experimental hyperlipidemia. Altogether, obtained evidence suggests that prolonged exposure of vascular endothelium to high levels of palmitate compromises endothelium barrier capacity and insulin-mediated eNOS regulation turning the enzyme permanently active. Disclosure M. Samsonov: None. V. P. Shirinsky: None. N. Podkuychenko: None. A. Y. Khapchaev: None. T. Vlasik: None. V. Lankin: None. M. Skulachev: Other Relationship; Self; Mitotech LLC. I. Stafeev: None. A. V. Vorotnikov: None. M. V. Shestakova: None. Funding Russian Science Foundation (19-15-00361)

THE IMPORTANCE OF CARNITINE AND ITS METABOLISM IN NEWBORN: LITERATURE REVIEW AND CLINICAL CASE

Aim: To analyze the literature on the processes of formation of endogenous and exogenous carnitine, its metabolism and function in the newborn. Material and methods: The literature data and international clinical recommendations for pathological conditions leading to primary and secondary carnitine deficiency have been retrospectively analyzed. A clinical case of a child with suspected systemic carnitine deficiency is presented. Conclusions: Depending on the reasons that led to carnitine deficiency, there are primary and secondary carnitine deficiency. Primary carnitine deficiency is a rare condition that can lead to metabolic decompensation, muscular and cardiac myopathy, and sudden death. Secondary carnitine deficiency can be caused by a genetically determined congenital metabolic defect, insufficient substrate intake, acquired disorder, immaturity of the biochemical pathway in premature infants, renal failure or iatrogenic exposure. Familiarization with the main causes of carnitine deficiency in newborns will more effectively detect and correct the clinical manifestations of this condition.

Exogenous carnitine application augments transport of fatty acids into mitochondria and stimulates mitochondrial respiration in maize seedlings grown under normal and cold conditions

This study aimed to investigate whether exogenous application of carnitine stimulates transportation of fatty acids into mitochondria, which is an important part of fatty acid trafficking in cells, and mitochondrial respiration in the leaves of maize seedlings grown under normal and cold conditions. Cold stress led to significant increases in lipase activity, which is responsible for the breakdown of triacylglycerols, and carnitine acyltransferase (carnitine acyltransferase I and II) activities, which are responsible for the transport of activated long-chain fatty acids into mitochondria. While exogenous application of carnitine has a similar promoting effect with cold stress on lipase activity, it resulted in further increases in the activity of carnitine acyltransferases compared to cold stress. The highest activity levels for these enzymes were recorded in the seedlings treated with cold plus carnitine. In addition, these increases were correlated with positive increases in the contents of free- and long-chain acylcarnitines (decanoyl-l-carnitine, lauroyl-l-carnitine, myristoyl-l-carnitine, and stearoyl-l-carnitine), and with decreases in the total lipid content. The highest values for free- and long-chain acylcarnitines and the lowest value for total lipid content were recorded in the seedlings treated with cold plus carnitine. On the other hand, carnitine with and without cold stress significantly upregulated the expression level of citrate synthase, which is responsible for catalysing the first reaction of the citric acid cycle, and cytochrome oxidase, which is the membrane-bound terminal enzyme in the electron transfer chain, as well as lipase. All these results revealed that on the one hand, carnitine enhanced transport of fatty acids into mitochondria by increasing the activities of lipase and carnitine acyltransferases, and, on the other hand, stimulated mitochondrial respiration in the leaves of maize seedlings grown under normal and cold conditions.

The rheumatoid synovial environment alters fatty acid metabolism in human monocytes and enhances CCL20 secretion.

Fatty acid oxidation (FAO) and glycolysis have been implicated in immune regulation and activation of macrophages. However, investigation of human monocyte intracellular metabolism in the context of the hypoxic and inflammatory rheumatoid arthritis (RA) synovium is lacking. We hypothesized that exposure of monocytes to the hypoxic and inflammatory RA environment would have a profound impact on their metabolic state, and potential to contribute to disease pathology. Human monocytes were isolated from buffy coats and exposed to hypoxia. Metabolic profiling of monocytes was carried out by LC-MS metabolomics. Inflammatory mediator release after LPS or RA-synovial fluid (RA-SF) stimulation was analysed by ELISA. FAO was inhibited by etomoxir or enhanced with exogenous carnitine supplementation. Transcriptomics of RA blood monocytes and RA-SF macrophages was carried out by microarray. Hypoxia exacerbated monocyte-derived CCL20 and IL-1β release in response to LPS, and increased glycolytic intermediates at the expense of carnitines. Modulation of carnitine identified a novel role for FAO in the production of CCL20 in response to LPS. Transcriptional analysis of RA blood monocytes and RA-SF macrophages revealed that fatty acid metabolism was altered and CCL20 increased when monocytes enter the synovial environment. In vitro analysis of monocytes showed that RA-SF increases carnitine abundance and CCL20 production in hypoxia, which was exacerbated by exogenous carnitine. This work has revealed a novel inflammatory mechanism in RA that links FAO to CCL20 production in human monocytes, which could subsequently contribute to RA disease pathogenesis by promoting the recruitment of Th17 cells and osteoclastogenesis.

Neural Stem Cell Fatty Acid Beta‐Oxidation and Autism Spectrum Disease

Inborn errors of metabolism occur with high incidence in human populations, and inborn deficiencies in fatty acid b‐oxidation (FAO) are clinically associated with neurological deficits such as speech weakness, motor delay, and autism. Using in vivo assays for analyzing neural stem cells (NSCs) in the developing mammalian forebrain, we find that neural stem cell (NSC)‐autonomous deficiencies in long‐chain FAO deplete neural stem cell (NSC) pools from mouse embryonic neocortex. Acute interference with activity of TMLHE (catalyzes the first step in carnitine biosynthesis), or with CPT1A (the rate‐limiting enzyme for carnitine‐dependent transport of long‐chain fatty acids into mitochondria), results in impaired NSC self‐renewal. Moreover, dorsal forebrain‐specific eviction of the Cpt1a gene resulted in reduced thickness of the murine neocortex at birth. Importantly, NSC deficits induced by TMLHE insufficiencies are rescued by exogenous carnitine in both cultured explants and by supplementation of the maternal diet. Taken together, the data argue for a direct role for FAO in controlling NSC self‐renewal vs differentiation in mammalian embryonic brain. The data further argue that deranged stem cell homeostasis is a significant mechanism for linking IEMs with human cognitive disorders such as autism. The implications of these findings for new strategies for management of autism risk will be discussed.Support or Funding InformationThis work was supported by the Robert A. Welch Foundation Award BE0017 and grant RO1GM112591 from the National Institute of HealthThis abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Effect of early supplementation of exogenous carnitine on liver mitochondrial damage in severely scalded rats and its pathological mechanism

Objective: To observe the effect of early supplementation of exogenous carnitine on liver mitochondrial damage in severely scalded rats and to explore its pathological mechanism. Methods: Seventy-two adult female Sprague-Dawley rats were divided into sham injury group, scald injury group, and scald injury+ carnitine group according to the random number table, with 24 rats in each group. Rats in sham injury group was sham injured on the back by immersing in 37 ℃ water bath for 12 s without fluid replacement. While rats in scald injury and scald injury+ carnitine groups were inflicted with 30% total body surface area (TBSA) full-thickness scald on the back by immersing in 98 ℃water bath for 12 s. Immediately after injury, rats in scald injury group and scald injury+ carnitine group were injected with Ringer's lactate solution with the dosage of 4 mL·kg(-1)·%TBSA(-1) via tail vein according to the Parkland formula, meanwhile rats in scald injury+ carnitine group were injected with L-carnitine solution with dosage of 300 mg·kg(-1)·d(-1) via tail vein from post injury hour (PIH) 1. At PIH 12, 24, 48 and 72, abdominal aorta blood and liver tissue were collected from 6 rats in each group. The serum levels of carnitine, β-hydroxybutyric acid, and ornithine carbamoyltransferase (OCT) were determined with enzyme-linked immuno sorbent assay, and the serum levels of lactate dehydrogenase (LDH), alanine aminotransferase(ALT), and aspartate transaminase (AST) was determined by automatic biochemical analyzer, Pathological changes of rats liver tissue were detected with HE staining. Data were processed with analysis of variance of factorial design and Student-Newman-Keulstest or Tamhane test, Bonferroni correction. Results: (1) Compared with sham injury group, the serum level of carnitine of rats in scald injury group was significantly lower at each time point (P 0.05]. The serum level of carnitine in scald injury+ carnitine group was significantly higher than that in scald injury group at each time point (P 0.05). The serum levels of LDH of rats in scald injury+ carnitine group were significantly lower than those of scald injury group at each time point (P 0.05). The serum levels of ALT and AST in scald injury+ carnitine group both showed a trend of decrease, and they peaked at PIH 12 [(260±25), (1 511±145) U/L, respectively]. (6) The liver tissue of rats in sham injury group was basically normal at each time point. The degree of liver injury of rats in scald injury+ carnitine group was lighter than that in scald injury group. The liver tissue of rats in scald injury group at PIH 72 showed obvious cytoplasm loose, liver tissue structure loss with diffuse fatty degeneration and large coagulative necrosis. Only partially scattered fatty degeneration was observed in the liver tissue of ras in scald injury+ carnitine group. Conclusions: By early supplementation of exogenous carnitine, serum levels of carnitine and β-hydroxybutyric acid can be restored to normal levels faster, alleviate mitochondrial damage of hepatocytes, and maintain the metabolic stability of hepatocytes in early stage of severe scald.

Carnitine and Acylcarnitines

L-Carnitine (levocarnitine) is a naturally occurring compound found in all mammalian species. The most important biological function of L-carnitine is in the transport of fatty acids into the mitochondria for subsequent β-oxidation, a process which results in the esterification of L-carnitine to form acylcarnitine derivatives. As such, the endogenous carnitine pool is comprised of L-carnitine and various short-, medium- and long-chain acylcarnitines. The physiological importance of L-carnitine and its obligatory role in the mitochondrial metabolism of fatty acids has been clearly established; however, more recently, additional functions of the carnitine system have been described, including the removal of excess acyl groups from the body and the modulation of intracellular coenzyme A (CoA) homeostasis. In light of this, acylcarnitines cannot simply be considered by-products of the enzymatic carnitine transfer system, but provide indirect evidence of altered mitochondrial metabolism. Consequently, examination of the contribution of L-carnitine and acylcarnitines to the endogenous carnitine pool (i.e. carnitine pool composition) is critical in order to adequately characterize metabolic status. The concentrations of L-carnitine and its esters are maintained within relatively narrow limits for normal biological functioning in their pivotal roles in fatty acid oxidation and maintenance of free CoA availability. The homeostasis of carnitine is multifaceted with concentrations achieved and maintained by a combination of oral absorption, de novo biosynthesis, carrier-mediated distribution into tissues and extensive, but saturable, renal tubular reabsorption. Various disorders of carnitine insufficiency have been described but ultimately all result in impaired entry of fatty acids into the mitochondria and consequently disturbed lipid oxidation. Given the sensitivity of acylcarnitine concentrations and the relative carnitine pool composition in reflecting the intramitochondrial acyl-CoA to free CoA ratio (and, hence, any disturbances in mitochondrial metabolism), the relative contribution of L-carnitine and acylcarnitines within the total carnitine pool is therefore considered critical in the identification of mitochondria dysfunction. Although there is considerable research in the literature focused on disorders of carnitine insufficiency, relatively few have examined relative carnitine pool composition in these conditions; consequently, the complexity of these disorders may not be fully understood. Similarly, although important studies have been conducted establishing the pharmacokinetics of exogenous carnitine and short-chain carnitine esters in healthy volunteers, few studies have examined carnitine pharmacokinetics in patient groups. Furthermore, the impact of L-carnitine administration on the kinetics of acylcarnitines has not been established. Given the importance of L-carnitine as well as acylcarnitines in maintaining normal mitochondrial function, this review seeks to examine previous research associated with the homeostasis and pharmacokinetics of L-carnitine and its esters, and highlight potential areas of future research.

Effect of hemodialysis session on the dynamics of carnitine ester profile changes in l-carnitine pretreated end-stage renal disease patients

Carnitine deficiency is common in end-stage renal disease (ESRD) patients receiving hemodialysis (HD) treatment. We investigated the effects of L-carnitine supplementation on acyl carnitine (AC) profile and the changes of distinct ACs during a single HD session in long-term L-carnitine pretreated ESRD patients. Twenty non-diabetic adult patients and 37 healthy controls were studied. Blood samples were drawn before and after 12 weeks of carnitine supplementation, then hourly during an HD session, as well as 30 min after the end of the session. Free and individual AC plasma levels were determined by using ESI MS/MS technique. HD patients showed lower free- and total carnitine levels and elevated ACs and acyl/free carnitine ratio before carnitine supplementation. The L-carnitine supplementation resulted in dramatic elevation of all carnitine esters. The HD session induced a progressive decline in free, short-chain, and dicarboxylic ACs (~80 % of pre-HD amount was washed out); the decrease of medium-chain ACs proved to be more moderate (~60 % washed out), whereas the long-chain ACs remained unaffected. Already 30 min after HD, a substantial increase was seen in free carnitine concentration (reaching 26 % of predialysis level) and the ACs also started to replenish (to 21-52 % of predialysis levels), without further exogenous carnitine load. The washout induced by HD session results in variable depletion of short-, medium-, and long-chain carnitine esters in carnitine-pretreated patients; the recovery of the circulating carnitine esters from the body stores occurs within 30 min after the cessation of the HD procedure.

Carnitine-induced senescence in glioblastoma cells

Carnitine is essential for lipid metabolism in cells and is known to possess antioxidant properties. Previous reports have suggested that antioxidants are able to induce senescence in glioblastoma cells, consequently, in the present study, we investigated the effect of carnitine on glioblastoma cells. Under conditions of hyponutrition (undernutrition), the proliferation of glioblastoma cells was attenuated and the level of intracellular carnitine was increased. Glioblastoma cell proliferation was also attenuated in cultures that were supplemented with exogenous carnitine, where the induction of senescence was detected by senescence-associated β-gal (SA-β-gal) staining. However, there was no evidence of the induction of apoptosis. These effects were not detected when cells were cultured with carnitine plus an inhibitor of p38 mitogen-activated protein kinase (MAPK). It, therefore, appears that carnitine has antioxidant actions in normal cells but induces senescence, which may be regarded as an opposite phenomenon, in glioblastoma cells. Senescence has been reported in cells exposed to temozolomide, which is a standard drug used for the treatment of glioblastoma. Carnitine could, therefore, represent an attractive alternative therapy for glioblastoma.

Dramatic Decrease of Carnitine Esters after Interruption of Exogenous Carnitine Supply in Hemodialysis Patients

L-carnitine supplementation is extensively used in patients on maintenance hemodialysis (HD) to improve dialysis-related clinical symptoms. In a series of studies, we investigated the dynamics of carnitine pool in carnitine-supplemented HD patients; here we report dramatic decrease with special changes of the ester profile due to interruption of the exogenous intake after the last HD session. Serum samples were collected from 18 L-carnitine-repleted end-stage renal disease (ESRD) patients before the L-carnitine supplementation, after completion of a carnitine supplementation period treatment (12 weeks, 1 g/IV/HD), right before the HD session, and 44 h after the dialysis. Levels of free carnitine (FC) and the individual esters were determined using electrospray MS/MS technique. Normally, L-carnitine supplementation causes significant elevation of all carnitine compounds to supraphysiological levels, which reaches a standard steady-state-like profile. In this study we found a dramatic decrease in the level of FC, and in short- and medium-chain acylcarnitines (ACs) 44 h after the last dialysis. At the end of this interdialytic period, FC levels increased to only 65% of the predialysis level, whereas the amounts of C2 and C3 esters recovered to only 50%. The level of C6 was 65% of the predialysis level, whereas the amount of C8 chain length ACs returned to 72% of the predialysis level. No significant change was seen in AC concentrations above C10 chain length. Omission of one single dosage of supplemental carnitine in long-term administration schemes results in dramatic decrease and reprofiling of carnitine esters even after the usual 44 h of interdialytic period.

The effect of carnitine on Arabidopsis development and recovery in salt stress conditions

Carnitine exists in all living organisms where it plays diverse roles. In animals and yeast, it is implicated in lipid metabolism and is also associated with oxidative stress tolerance. In bacteria, it is a major player in osmotic stress tolerance. We investigate the carnitine function in plants and our present work shows that carnitine enhances the development and recovery of Arabidopsis thaliana seedlings subjected to salt stress. Biological data show that exogenous carnitine supplies improve the germination and survival rates of seedlings grown on salt-enriched medium, in a manner comparable to proline. Both compounds are shown to improve seedling survival under oxidative constraint meaning that they may act on salt stress through antioxidant properties. A transcriptome analysis of seedlings treated with exogenous carnitine reveals that it modulates the expression of genes involved in water stress and abscisic acid responses. Analyses of the abscisic acid mutants, aba1-1 and abi1-1, indicate that carnitine and proline may act through a modulation of the ABA pathway.

Investigations on the motility of human spermatozoa in a defined medium in the presence of metabolic inhibitors and of carnitine.

When washed human sperm were incubated in a modified Krebs-Ringer buffer solution in the absence of exogenous metabolizable substrates at 30 degrees C they maintained progressive motility for at least six hours. Under these conditions the spermatozoa apparently utilize endogenous substrates but addition of exogenous substrates (glucose, fructose, acetate, short-chain fatty acids, branched chain amino acids) did not affect the % progressive motility or % total motility of the cells. The phospholipase inhibitors, quinacrine and Upjohn No. 1002, inhibited progressive motility when added to sperm utilizing endogenous substrate, and subsequent addition of oxidative or glycolytic substrates did not reverse the inhibition. In contrast, the inhibition by KCN of progressive motility based upon utilization of endogenous substrate was reversed upon addition of glycolyzable compounds (glucose or fructose). The addition of carnitine or its acetyl-, propionyl-, isobutyryl-, valeryl- or isovaleryl esters did not consistently affect progressive or total motility of sperm samples. The inhibitor, octylsulfobetaine, inhibited sperm motility at a concentration higher than that required for inhibition of carnitine acetyltransferase or translocase activity. On the basis of these results it does not appear that exogenous carnitine has an effect on the motility of human sperm incubated under the conditions described here.

Dietary L-Carnitine Supplementation to Cultivated Fish: A Mini-Review

It is not clear whether animals require exogenous carnitine, and over the past 20 years, the scientific discussion regarding this subject continued with arguments pro and contra. Some studies observed that feeding fish with dietary carnitine supplements may improve growth and protect against several disease outbreak. However, such growth improvement was not always observed. The results can be interpreted in two ways: Firstly, the endogenous carnitine biosynthesis may be adequate to maintain sufficient tissue levels during growth. Secondly, the responses to dietary carnitine supplements are influenced by environmental and physiological interactions. The aim of this mini review was to provide an overview of the positive effects of dietary carnitine supplementation on fish metabolism, and possible factors that might alter dietary carnitine requirements, such as feed composition, species, age, tissue dependence on fatty acid oxidation and metabolic conditions.

Carnitine Deficiency in Pregnancy

Carnitine deficiency is a potential cause of metabolic crisis during periods of high energy demand or stress. Affected individuals have very low carnitine levels in blood, decreased carnitine transport in fibroblasts, and commonly have mutations in the OCTN2 gene. We report management through pregnancy and delivery of a patient with carnitine deficiency who had reduced carnitine transport in fibroblasts, but no mutations in the OCTN2 gene. Carnitine deficiency can be treated with exogenous carnitine in select patients during pregnancy. This is especially helpful, because carnitine levels decrease during pregnancy in normal individuals, and neonates are dependent on exogenous carnitine.

Disruption of AtOCT1, an organic cation transporter gene, affects root development and carnitine‐related responses in Arabidopsis

In animals, organic cation/carnitine transporters (OCTs) are involved in homeostasis and distribution of various small endogenous amines (e.g. carnitine, choline) and detoxification of xenobiotics such as nicotine. Here, we describe the characterization of AtOCT1, an Arabidopsis protein that shares most of the conserved features of mammalian plasma membrane OCTs. Transient expression of an AtOCT1::GFP fusion protein in onion epidermal cells and Arabidopsis protoplasts supported localization in the plasmalemma. AtOCT1 functionally complemented the Deltacit2/Deltaagp2p yeast strain that is defective in plasma membrane carnitine transport. Disruption of AtOCT1 in an Arabidopsis oct1-1 knockout mutant affected both the expression of carnitine-related genes and the developmental defects induced by exogenous carnitine. RT-PCR and promoter-uidA fusion analysis showed that AtOCT1 was expressed in vascular tissues of various organs and at sites of lateral root formation. Correlating with this expression pattern, oct1-1 seedlings grown in vitro exhibited a higher degree of root branching than the wild-type, showing that the disruption of AtOCT1 affected root development under certain conditions.

Effects of L-Carnitine and its Derivatives – Studies on Isolated Hearts

The metabolism in the heart prefers long-chain fatty acids to other substrates. L-Carnitine, a co-factor of coenzyme A, plays an essential role in the transport of long-chain fatty acids through the inner mitochondrial membrane. Without carnitine, metabolisation of long-chain fatty acids in the mitochondria is not possible. In addition, acyl groups from acyl-CoA compounds can be transferred to L-carnitine, thus influencing the enzymatic activities of important mitochondrial enzymes. The isolated heart model developed by Langendorff was used to investigate the effects of L-carnitine on the heart. During aerobic perfusion, the hemodynamic parameters of isolated hearts reacted in a very sensitive way to alterations in the external conditions (temperature, preload, composition of the perfusion solution). During postischemic perfusion, recovery of the hearts was also influenced by the composition of the perfusion. The hemodynamic parameters of the reperfused hearts increased markedly if there was a sufficiently high supply of long-chain fatty acids and/or glucose. The insufficient recovery of hearts perfused without glucose and at low fatty acid concentrations could be improved by adding L-carnitine. Determination of carnitine levels in heart tissue found that the heart loses about 30% of its carnitine content during ischemia, and that exogenous carnitine is taken up by the heart during reperfusion. There it effects the restoration of sufficient concentrations of creatine phosphate and ATP, a fact that was confirmed by 31P NMR spectroscopy. NMR spectroscopy also established that L-carnitine lessens the harmful effects of ischemia-induced metabolic acidosis. The favourable influence of L-carnitine on the heart in the reperfusion period could be due to a reduction in oxygen radicals (lowering of MDA concentrations during reperfusion, raising of GPx and SOD activities). The findings of these experiments on isolated hearts as well as the favourable results of two placebo-controlled and double-blind clinical studies (investigating the effects of carnitine in cardiomyopathy patients and the effects of L-carnitine in hemodialysis patients) demonstrate that L-carnitine produces positive therapeutic effects, particularly in heart and circulatory diseases.