Fine Mapping and Functional Analysis Reveal a Role of SLC22A1 in Acylcarnitine Transport.

Genome-wide association studies have identified a signal at the SLC22A1 locus for serum acylcarnitines, intermediate metabolites of mitochondrial oxidation whose plasma levels associate with metabolic diseases. Here, we refined the association signal, performed conditional analyses, and examined the linkage structure to find coding variants of SLC22A1 that mediate independent association signals at the locus. We also employed allele-specific expression analysis to find potential regulatory variants of SLC22A1 and demonstrated the effect of one variant on the splicing of SLC22A1. SLC22A1 encodes a hepatic plasma membrane transporter whose role in acylcarnitine physiology has not been described. By targeted metabolomics and isotope tracing experiments in loss- and gain-of-function cell and mouse models of Slc22a1, we uncovered a role of SLC22A1 in the efflux of acylcarnitines from the liver to the circulation. We further validated the impacts of human variants on SLC22A1-mediated acylcarnitine efflux in vitro, explaining their association with serum acylcarnitine levels. Our findings provide the detailed molecular mechanisms of the GWAS association for serum acylcarnitines at the SLC22A1 locus by functionally validating the impact of SLC22A1 and its variants on acylcarnitine transport.

Effects of L-carnitine on the erythrocytes of stored human blood.

OBJECTIVES: This study aimed to assess the effects of L-carnitine on oxidative stress in human erythrocytes during storage. BACKGROUND: Using antioxidants as components of blood storage solutions may combat the effects of storage-induced oxidative stress on erythrocytes. METHODS: Blood from male adults was stored at 4 °C for 55 days in citrate phosphate dextrose adenine solution, without L-carnitine (Control) and with L-carnitine as an additive (at concentrations of 10, 30 and 60 mM - Experiments). Every fifth day, erythrocyte markers (morphology, count, haemoglobin, haemolysis and osmotic fragility), antioxidant defences (antioxidant enzymes and total antioxidant capacity) and oxidative stress markers (superoxides, lipid peroxidation and protein oxidation products) were analysed. RESULTS: Oxidative damage was observed in controls (day 25 onwards) and in experiments (day 35 onwards). L-carnitine (10 and 30 mM) protected erythrocytes from damage up to day 35 by maintaining haemoglobin and lipid peroxidation, assisting antioxidant enzymes and increasing antioxidant capacity by elevating sulfhydryls and ascorbic acid. L-carnitine was beneficial in prolonging storage up to 55 days but could not prevent oxidative damage completely in terms of haemolysis and osmotic fragility. CONCLUSIONS: L-carnitine ameliorated oxidative stress, but combinations with other antioxidants may provide comprehensive protection to erythrocytes during storage.

Effect of L-Carnitine on Amino Acid Metabolism in Elderly Patients Undergoing Regular Hemodialysis.

INTRODUCTION: Among patients regularly undergoing hemodialysis, hypocarnitinaemia often develops as a consequence of inadequate dietary intake, reduced synthesis in the body, and considerable losses during hemodialysis. OBJECTIVES: To evaluate the effects of L-carnitine supplementation on patients with end-stage kidney disease (ESKD) who underwent hemodialysis. METHODS: Thirty-one patients with ESKD, comprising 18 men and 13 women, with a median age of 72 (range 58-89) years, who underwent regular hemodialysis received treatment with L-carnitine for 1 year. The total and free carnitine, acylcarnitine, and amino acids (AA) levels before and after L-carnitine treatment were analyzed, and the blood biochemistry results and clinical profiles of the subjects were compared before and after treatment. RESULTS: The median (interquartile range [IQR]) serum total and free carnitine and acylcarnitine levels significantly increased from 34.5 (28.2-44.3), 20.9 (15.8-27.6), and 14.1 (11.2-17.6) µmol/L, respectively to 407.4 (371.6-493.5), 270.2 (228.3-316.0), and 155.0 (136.1-168.5) µmol/L, respectively, after treatment (all p < 0.001). The median (IQR) blood valine, tyrosine, phenylalanine, and citrulline levels increased from 0.94 (0.80-1.09), 0.45 (0.39-0.55), 0.61 (0.56-0.79), and 1.04 (0.79-1.26) mg/dL, respectively to 1.24 (1.13-1.54), 0.76 (0.62-0.85), 0.90 (0.70-1.04), and 1.22 (0.92-1.39) mg/dL, respectively, following L-carnitine treatment (p < 0.001, p < 0.001, p = 0.002, and p = 0.030, respectively); however, the median (IQR) blood arginine level decreased from 0.20 (0.13-0.24) to 0.09 (0.06-0.14) mg/dL after treatment (p < 0.001). The median (IQR) percentage fractional shortening (41.5 vs. 41.9%; p = 0.012) and left ventricular ejection fraction (65.2 vs. 67.3%; p = 0.036) increased significantly following treatment. CONCLUSIONS: L-Carnitine increased the blood acylcarnitine levels, enhanced fatty acid metabolism, and affected AAs metabolism; this may be beneficial for energy production within the cardiac and skeletal muscles.

Polymeric Nanoparticle Versus Liposome Formulations: Comparative Physicochemical and Metabolomic Studies as L-Carnitine Delivery Systems.

L-Carnitine has attracted much more attention especially in the treatment of crucial diseases such as diabetes, regional slimming, and obesity because of its metabolic activities. However, because of its short half-life, low bioavailability, and inability to be stored in the body, frequent dosing is required. In this study, L-carnitine-loaded liposome (lipo-carnitine) and PLGA nanoparticle (nano-carnitine) formulations were prepared and characterized. For lipo-carnitine and nano-carnitine formulations, particle size values were 97.88 ± 2.96 nm and 250.90 ± 6.15 nm; polydispersity index values were 0.35 ± 0.01 and 0.22 ± 0.03; zeta potential values were 6.36 ± 0.54 mV and - 32.80 ± 2.26 mV; and encapsulation efficiency percentage values were 14.26 ± 3.52% and 21.93 ± 4.17%, respectively. Comparative in vitro release studies of novel formulations and solution of L-carnitine revealed that L-carnitine released 90% of its content at the end of 1st hour. On the other hand, lipo-carnitine and nano-carnitine formulations maintained a controlled-release profile for 12 h. The in vitro efficacy of the formulations on cardiac fibroblasts (CFs) was evaluated by metabolomic studies and pathway analysis. Besides the prolonged release, lipo-carnitine/nano-carnitine formulations were also found to be effective on amino acid, carbohydrate, and lipid metabolisms. As a result, innovative nano-formulations were successfully developed as an alternative to conventional preparations which are available on the market.

Relative bioavailability of carnitine delivered by ruminal or abomasal infusion or by encapsulation in dairy cattle.

Two studies were designed to evaluate the relative bioavailability of l-carnitine delivered by different methods in dairy cattle. In experiment 1, 4 Holstein heifers were used in a split-plot design to compare ruminally or abomasally infused l-carnitine. The study included 2 main-plot periods, with infusion routes allocated in a crossover design. Within main-plot periods, each of 3 subplot periods consisted of 4-d infusions separated with 4-d rest periods. Subplot treatments were infusion of 1, 3, and 6 g of l-carnitine/d in conjunction with 6 g/d of arabinogalactan given in consideration of eventual product manufacturing. Doses increased within a period to minimize carryover risk. Treatments were solubilized in 4 L of water and delivered in two 10-h infusions daily. Blood was collected before the start of infusion period and on d 4 of each infusion period to obtain baseline and treatment l-carnitine concentrations. There was a dose × route interaction and route effect for increases in plasma carnitine above baseline, with increases above baseline being greater across all dose levels when infused abomasally compared with ruminally. Results demonstrated superior relative bioavailability of l-carnitine when ruminal exposure was physically bypassed. In experiment 2, 56 lactating Holstein cows (143 ± 72 d in milk) were used in 2 cohorts in randomized complete block designs (blocked by parity and milk production) to evaluate 2 rumen-protected products compared with crystalline l-carnitine. Treatments were (1) control, (2) 3 g/d of crystalline l-carnitine (crystalline), (3) 6 g/d of crystalline, (4) 5 g/d of 40COAT (40% coating, 60% l-carnitine), (5) 10 g/d of 40COAT, (6) 7.5 g/d of 60COAT (60% coating, 40% l-carnitine), and (7) 15 g/d of 60COAT. Treatments were top-dressed to diets twice daily. Each cohort used 14-d and included a 6-d baseline measurement period with the final 2 d used for data and sample collection, and an 8-d treatment period with the final 2 d used for data and sample collection. Plasma, urine, and milk samples were analyzed for l-carnitine. Crystalline and 40COAT linearly increased plasma l-carnitine, and 60COAT tended to linearly increase plasma l-carnitine. Total excretion (milk + urine) of l-carnitine averaged 1.52 ± 0.04 g/d in controls, increased linearly with crystalline and 40COAT, and increased quadratically with 60COAT. Crystalline increased plasma l-carnitine and l-carnitine excretion more than 40COAT and 60COAT. In conclusion, preventing ruminal degradation of l-carnitine increased delivery of bioavailable carnitine to cattle, but effective ruminal protection and postruminal bioavailability is challenging.

Kinetics of carnitine concentration after switching from oral administration to intravenous injection in hemodialysis patients.

Carnitine has high dialyzability and is often deficient in dialysis patients. This deficiency is treated by either intravenous (IV) or oral supplementation of carnitine. In this study, the mode of carnitine administration was changed from oral to IV in 17 hemodialysis (HD) patients, and the treatment was discontinued after 1 year. We found that the levels of total carnitine (TC), free-carnitine (FC), and acyl-carnitine (AC) significantly increased after 3 months of switching to IV administration (p < .05). After discontinuation of carnitine administration, the TC, FC, and AC levels decreased before dialysis. The average FC value was maintained at the normal levels until 9 months, but fell below the normal values when measured at the 12th month of discontinuation. In conclusion, carnitine was maintained at significantly high levels despite the smaller dose by IV infusion as compared with that by oral administration. We therefore suggest that our results be considered while determining both the carnitine administration route and the administration period in dialysis patients under clinical settings.

Characterization of an L-Carnitine Transport System in Murine Photoreceptor Cell Line.

While it is well known that L-carnitine [3-hydroxy-4-(trimethylazaniumyl)-butanoate] is an essential molecule for ß-oxidation, it provides anti-oxidative effects as well. Since these effects have been observed in photoreceptor cells, the carnitine's intracellular concentration is considered to play a protective role against oxidative damage to those cells. However, even though its high hydrophilicity makes it likely that carnitine import is accomplished via a dedicated host transport system, the specific uptake process into those cells is currently unknown. Therefore, in this study, we sought to identify and characterize photoreceptor cell carnitine uptake transporter(s) utilizing 661W cells as a photoreceptor cell model. The results of our uptake assays showed that carnitine was transported into 661W cells in a saturable manner (Km=5.5 mM), and that the activity was susceptible to extracellular pH and Na+. While these data suggest the involvement of a transporter in 661W cell carnitine uptake, the observed transport profile did not correspond to any of the currently known carnitine transporters such as organic cation/carnitine transporter 1 (Octn1), Octn2, Octn3, B0,+ and Ct2. In fact, in our experiments, the mRNA expressions for such carnitine transporters in 661W cells were consistently very low and the carnitine transporter substrates did not inhibit the uptake activities. Taken as a whole, our results indicate that carnitine is transported into 661W cells in a carrier-mediated manner. However, since its transport modes cannot be fully explained by known carnitine transporters, it is highly likely that photoreceptor cells utilize a unique molecularly-based carnitine uptake system.

Bioavailabilty of a liquid Vitamin Trace Element Composition in healthy volunteers.

BACKGROUND: Many Vitamins and minerals for dietary supplements lack a standard scientific and regulatory definition that accurately reflects the bioavailabilities in humans. Especially the bioavailability of natural compounds in complex mixtures, where the different ingredients may interfere with each other, is unknown. METHODS: To learn more about the bioavailability of the ingredients in the complex compound LaVita® we examined blood levels of subjects, who ingested the multivitamin and trace element composition for 6 month continuously. Blood samples for the analysis of the ingredients were taken before, during, and after administration. RESULTS: Our data indicated a significant increase of most ingredients after 3 month, and additional three months, except for Vitamin (B9 Folic acid). The semivitamins Q10 and carnitine increased in the first 3 month (both p<0.001). While carnitine dropped during the second term, Q10 levels increased further slowly. After three months a significant increase was observed for iron (serum p=0.039; blood cells p=0.025), Selenium (serum p=0.048; cells p=0.006), and chromium (serum p=0.029). Zinc - known to interfere with the iron resorption - increased slowly in the first term of 3 months, but was raised significantly after 6 months (serum and blood cells, each p<0.001). The Copper/Zink ratio dropped accordingly (p<0.001). CONCLUSION: We conclude that resorption interference between specific ingredients, and after resorption redistribution of specific ingredients to various tissue compartments precludes a linear increase of the respective serum parameters. We observed no deleterious resorption competitions for individual compounds. No parameter reached critical levels. We conclude that the test substance (LaVita®) is a sufficiently safe composite for long term consumption.

[L-carnitine: properties and perspectives for use in sports practice].

The analysis of published data relating to the use in sports practice metabolic non-doping agent--L-carnitine. The review discusses some aspects of the mechanism of its action on the human body. The information is given about the role of carnitine in the energy processes, mechanisms of carnitine deficiency. On the basis of the literature is given scientific rationale for applying this metabolite in athletes, particularly with cardiovascular and immune disorders.

Effect of carnitine, acetyl-, and propionylcarnitine supplementation on the body carnitine pool, skeletal muscle composition, and physical performance in mice.

PURPOSE: Pharmacokinetics and effects on skeletal muscle and physical performance of oral acetylcarnitine and propionylcarnitine are not well characterized. We therefore investigated the influence of oral acetylcarnitine, propionylcarnitine, and carnitine on body carnitine homeostasis, energy metabolism, and physical performance in mice and compared the findings to non-supplemented control animals. METHODS: Mice were supplemented orally with 2 mmol/kg/day carnitine, acetylcarnitine, or propionylcarnitine for 4 weeks and studied either at rest or after exhaustive exercise. RESULTS: In the supplemented groups, total plasma and urine carnitine concentrations were significantly higher than in the control group receiving no carnitine, whereas the skeletal muscle carnitine content remained unchanged. The supplemented acylcarnitines were hydrolyzed in intestine and liver and reached the systemic circulation as carnitine. Bioavailability of carnitine and acylcarnitines, determined as the urinary excretion of total carnitine, was in the range of 19 %. Skeletal muscle morphology, including fiber-type composition, was not affected, and oxygen consumption by soleus or gastrocnemius fibers was not different between the groups. Supplementation with carnitine or acylcarnitines had no significant impact on the running capacity, but was associated with lower plasma lactate levels and a higher glycogen content in white skeletal muscle after exhaustive exercise. CONCLUSIONS: Oral supplementation of carnitine, acetylcarnitine, or propionylcarnitine in mice is associated with increased plasma and urine total carnitine concentrations, but does not affect the skeletal muscle carnitine content. Despite better preservation of skeletal muscle glycogen and lower plasma lactate levels, physical performance was not improved by carnitine or acylcarnitine supplementation.

Pharmacokinetic and pharmacological effects of ß-hydroxyphosphocarnitine in animal models.

The purpose of this research was to describe the pharmacokinetic parameters of ß-hydroxyphosphocarnitine (ß-HPC; CAS No. 1220955-20-3) after a single oral dose in rats and rabbits as well as to assess the impact of 14 weeks of ß-HPC (100 mg/kg) treatment on the serum metabolites and liver enzymes, body weight, and hepatic steatosis of lean and obese Zucker fa/fa rats. In the case of the rat and rabbit study, the ß-HPC area under the curve, biological half-life, and clearance were 2,174.4 versus 3,128 µg ∙ h/ml, 23.7 versus 8.87 h, and 13.9 versus 151.1 ml/h in the rats versus the rabbits, respectively. The values for the time of maximal concentration were 0.58 versus 1.53 h, for the maximal concentration, they were 62.4 versus 221.4 µg/ml, and for the absorption rate constant 0.02 versus 2.40 h(-1), respectively. In the case of the Zucker fa/fa rat study, ß-HPC administered orally once a day reduced insulin, triglyceride, and cholesterol levels in the liver and serum; it also reduced weight gain and decreased liver steatosis in obese rats after 14 weeks. ß-HPC could therefore potentially be used in the treatment of metabolic syndrome.

Short communication: the pharmacological peroxisome proliferator-activated receptor α agonist WY-14,643 increases expression of novel organic cation transporter 2 and carnitine uptake in bovine kidney cells.

Recent studies in rodents demonstrated that peroxisome proliferator-activated receptor α (PPARα), a central regulator of energy homeostasis, is an important transcriptional regulator of the gene encoding the carnitine transporter novel organic cation transporter 2 (OCTN2). Less is known with regard to the regulation of OCTN2 by PPARα and its role for carnitine transport in cattle, even though PPARα activation physiologically occurs in the liver of high-producing cows during early lactation. To explore the role of PPARα for OCTN2 expression and carnitine transport in cattle, we studied the effect of the PPARα activator WY-14,643 on the expression of OCTN2 in the presence and absence of PPARα antagonists and on OCTN2-mediated carnitine transport in the Madin-Darby bovine kidney (MDBK) cell line. The results show that WY-14,643 increases mRNA and protein levels of OCTN2, whereas co-treatment of MDBK cells with WY-14,643 and the PPARα antagonist GW6471 blocks the WY-14,643-induced increase in mRNA and protein levels of OCTN2 in bovine cells. In addition, treatment of MDBK cells with WY-14,643 stimulates specifically Na(+)-dependent carnitine uptake in MDBK cells, which is likely the consequence of the increased carnitine transport capacity of cells due to the elevated expression of OCTN2. In conclusion, our results indicate that OCTN2 expression and carnitine transport in cattle, as in rodents, are regulated by PPARα.

L-carnitine modified nanoparticles target the OCTN2 transporter to improve the oral absorption of jujuboside B.

As a bioactive saponin derived from the seeds of Ziziphus jujuba Mill. var. spinosa (Bunge) Hu ex H. F. Chow, jujuboside B (JuB) shows great potential in anti-anxiety, anti-depression and improving learning and memory function. However, its oral bioavailability is very poor. In this study, a novel drug-loading nanoparticles system was prepared with polyethylene glycol and polylactic-co-glycolic acid copolymer (PEG-PLGA), and further modified with L-carnitine (LC) to target intestinal organic cation/carnitine transporter 2 (OCTN2) to improve the oral absorption of JuB. Under the optimized preparation conditions, the particle sizes of obtained JuB-PEG-PLGA nanoparticles (B-NPs) and LC modified B-NPs (LC-B-NPs) were 110.67 ± 11.37 nm and 134.00 ± 2.00 nm with the entrapment efficiency (EE%) 73.46 ± 1.26 % and 76.01 ± 2.10 %, respectively. The pharmacokinetics in SD rats showed that B-NPs and LC-B-NPs increased the bioavailability of JuB to 134.33 % and 159.04 % respectively. In Caco-2 cell model, the prepared nanoparticles significantly increased cell uptake of JuB, which verified the pharmacokinetic results. The absorption of LC-B-NPs mainly depended on OCTN2 transporter, and Na+ played an important role. Caveolin and clathrin were involved in the endocytosis of the two nanoparticles. In conclusion, both B-NPs and LC-B-NPs can improve the oral absorption of JuB, and the modification of LC can effectively target the OCTN2 transporter.

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.

Carnitine palmitoyltransferase 2: New insights on the substrate specificity and implications for acylcarnitine profiling.

Over the last years acylcarnitines have emerged as important biomarkers for the diagnosis of mitochondrial fatty acid beta-oxidation (mFAO) and branched-chain amino acid oxidation disorders assuming they reflect the potentially toxic acyl-CoA species, accumulating intramitochondrially upstream of the enzyme block. However, the origin of these intermediates still remains poorly understood. A possibility exists that carnitine palmitoyltransferase 2 (CPT2), member of the carnitine shuttle, is involved in the intramitochondrial synthesis of acylcarnitines from accumulated acyl-CoA metabolites. To address this issue, the substrate specificity profile of CPT2 was herein investigated. Saccharomyces cerevisiae homogenates expressing human CPT2 were incubated with saturated and unsaturated C2-C26 acyl-CoAs and branched-chain amino acid oxidation intermediates. The produced acylcarnitines were quantified by ESI-MS/MS. We show that CPT2 is active with medium (C8-C12) and long-chain (C14-C18) acyl-CoA esters, whereas virtually no activity was found with short- and very long-chain acyl-CoAs or with branched-chain amino acid oxidation intermediates. Trans-2-enoyl-CoA intermediates were also found to be poor substrates for CPT2. Inhibition studies performed revealed that trans-2-C16:1-CoA may act as a competitive inhibitor of CPT2 (K(i) of 18.8 microM). The results obtained clearly demonstrate that CPT2 is able to reverse its physiological mechanism for medium and long-chain acyl-CoAs contributing to the abnormal acylcarnitines profiles characteristic of most mFAO disorders. The finding that trans-2-enoyl-CoAs are poorly handled by CPT2 may explain the absence of trans-2-enoyl-carnitines in the profiles of mitochondrial trifunctional protein deficient patients, the only defect where they accumulate, and the discrepancy between the clinical features of this and other long-chain mFAO disorders such as very long-chain acyl-CoA dehydrogenase deficiency.

L-carnitine is an osmotic agent suitable for peritoneal dialysis.

Excessive intraperitoneal absorption of glucose during peritoneal dialysis has both local cytotoxic and systemic metabolic effects. Here we evaluate peritoneal dialysis solutions containing L-carnitine, an osmotically active compound that induces fluid flow across the peritoneum. In rats, L-carnitine in the peritoneal cavity had a dose-dependent osmotic effect similar to glucose. Analogous ultrafiltration and small solute transport characteristics were found for dialysates containing 3.86% glucose, equimolar L-carnitine, or combinations of both osmotic agents in mice. About half of the ultrafiltration generated by L-carnitine reflected facilitated water transport by aquaporin-1 (AQP1) water channels of endothelial cells. Nocturnal exchanges with 1.5% glucose and 0.25% L-carnitine in four patients receiving continuous ambulatory peritoneal dialysis were well tolerated and associated with higher net ultrafiltration than that achieved with 2.5% glucose solutions, despite the lower osmolarity of the carnitine-containing solution. Addition of L-carnitine to endothelial cells in culture increased the expression of AQP1, significantly improved viability, and prevented glucose-induced apoptosis. In a standard toxicity test, the addition of L-carnitine to peritoneal dialysis solution improved the viability of L929 fibroblasts. Thus, our studies support the use of L-carnitine as an alternative osmotic agent in peritoneal dialysis.

Enhanced bioavailability of L-carnitine after painless intradermal delivery vs. oral administration in rats.

PURPOSE: In vitro and in vivo permeation studies were conducted to evaluate the characteristic of percutaneous administration of high hydrophilic drug L-carnitine (LC) by Functional MicroArray (FMA) painless intradermal delivery system. METHODS: In vitro study was designed to assess the effects of various skins, donor concentration and hydrogels from different carbomer derivatives on the release of LC in a Franz-type diffusion cell. The LC gel patches with carbomer 980 P were prepared and successfully applied to pharmacokinetic study of SD rats with and without FMA. Intravenous injection and oral administration were performed to support pharmacokinetic calculations and comparison of bioavailability. RESULTS: Enhanced delivery of LC using FMA was achieved in skin of different species in vitro studies. The 750 mg LC gel patches were applied to rats over 6 h, and approximately 27% of loaded dose was transported into rat. A 2.8-fold enhancement of absolute bioavailability for LC with FMA intradermal delivery system was observed compared with oral LC administration in vivo study. CONCLUSIONS: Both in vitro and in vivo studies demonstrated that the FMA intradermal delivery system can enhance the delivery and bioavailability of LC.

Plasma pharmacokinetics and gastrointestinal transit of a new propionyl-L-carnitine controlled release formulation.

Propionyl-L-carnitine is a naturally occurring analogue of L-carnitine (LC) produced in the body. PLC administration has shown beneficial effects in cardiovascular pathologies. In ulcerative colitis (UC), oral PLC treatment increased clinical presentation and positively influenced colon histology. In the present study, the MMX Multi Matrix System® (MMX™) was used as drug delivery strategy for targeted PLC colon delivery. A pharmacoscintigraphic study (n = 6 healthy volunteers) described release characteristics of two MMX-PLC-HCl controlled release 500 mg tablets. A pharmacokinetic (PK) parallel group study (n = 24) determined safety, plasma PLC concentrations and PK parameters after single and multiple doses. Gastrointestinal transit was slow and variable. The colon was the main site of PLC release and absorption. After single 500 or 1000 mg PLC doses plasma PLC and LC increased up to 2.6 and 1.2-1.3-fold compared to baseline. Multiple doses of 500 and 1000 mg twice a day over 7 days did not significantly increase maximum plasma concentrations of PLC or LC with respect to concentrations achieved after single dose administration. The colon is the main site of PLC release and absorption from MMX-PLC tablets. A daily dose of 500 mg to 1000 mg PLC twice a day was well tolerated, justifying further studies in patients with pathologies of the distal gastrointestinal tract to evaluate the efficacy of the MMX-PLC formulation.

Dynamic adaptive changes of the serum carnitine esters during and after L-carnitine supplementation in patients with maintenance haemodialysis.

BACKGROUND: Here we report the serum carnitine ester profile during and after 1g iv/day L-carnitine supplementation in haemodialysis patients. MATERIALS AND METHODS: Seven patients were studied over 29 weeks. After a control day, 12 weeks of replacement therapy was introduced followed by 17 weeks of washout period. The serum acylcarnitine concentrations were determined by isotope dilution ESI MS/MS technique. RESULTS: At baseline significantly decreased free carnitine (48%, p < 0.01) and a 1.5-16-fold elevation of 16 out of 27 acylcarnitines were detected in HD patients compared with the controls. On the last day of L-carnitine supplementation a 1.6-4.8-fold increase was observed in the acylcarnitine levels compared with day 0; the increase-profile was achieved in four different patterns. The increase rate was rapid and early saturable for C5, C5OH, C6DC, C8:1, C10DC and C18:2 esters, slower for C2, C4, C6, C18 and C18:1 esters, it was slowest and reached a late plateau for C3, C8DC, C14:2, C16 and C16:1, and finally almost gradual increase was seen for 11 acylcarnitines. Three months after the cessation of carnitine treatment marked concentration drops were found for almost all acylcarnitines (by 11-74 % of week 12, p < 0.05); the values further decreased over the five remaining weeks of the observation period. CONCLUSION: Carnitine administration affected the levels of circulating esters in different dynamics and kinetics suggesting a regulated, non-random adaptive reallocation of nutrients. A considerable washout was achieved 3 months after discontinuation of the supplementation; however, the profile still was suggestive for presence of rest of accumulated supplement.

Single dose administration of L-carnitine improves antioxidant activities in healthy subjects.

L-carnitine has been used as a supplement to treat cardiovascular or liver disease. However, there has been little information about the effect of L-carnitine on anti-oxidation capability in healthy human subjects. This study was designed to investigate the correlation between plasma L-carnitine concentration and antioxidant activity. Liquid L-carnitine (2.0 g) was administered orally as a single dose in 12 healthy subjects. Plasma concentration of L-carnitine was detected by HPLC. The baseline concentration of L-carnitine was 39.14 ± 5.65 µmol/L. After single oral administration, the maximum plasma concentration (C(max)) and area under the curve (AUC(0-∞)) were 84.7 ± 25.2 µmol/L and 2,676.4 ± 708.3 µmol/L·h, respectively. The half-life and the time required to reach the C(max) was 60.3 ± 15.0 min and 3.4 ± 0.46 h, respectively. There was a gradual increase in plasma concentrations of superoxide dismutase (SOD), glutathione peroxidase (GSH-Px), catalase and total antioxidative capacity (T-AOC) in the first 3.5 h following L-carnitine administration. The plasma concentrations of SOD, GSH-Px, catalase and T-AOC returned to baseline levels within 24 h. A positive correlation was found between L-carnitine concentration and the antioxidant index of SOD (r = 0.992, P < 0.01), GSH-Px (r = 0.932, P < 0.01), catalase (r = 0.972, P < 0.01) or T-AOC (r = 0.934, P < 0.01). In conclusion, L-carnitine increases activities of antioxidant enzymes and the total antioxidant capacity in healthy subjects. It may be useful as a supplementary therapy for chronic illnesses involving excessive oxidative stress.