Effects of L-carnitine supplementation on renal anemia in poor responders to erythropoietin

Genomic Selection Signals in Andean Highlanders Reveal Adaptive Placental Metabolic Phenotypes That Are Disrupted in Preeclampsia

BACKGROUND

The chronic hypoxia of high-altitude residence poses challenges for tissue oxygen supply and metabolism. Exposure to high altitude during pregnancy increases the incidence of hypertensive disorders of pregnancy and fetal growth restriction and alters placental metabolism. High-altitude ancestry protects against altitude-associated fetal growth restriction, indicating hypoxia tolerance that is genetic in nature. Yet, not all babies are protected and placental pathologies associated with fetal growth restriction occur in some Andean highlanders.

METHODS

We examined placental metabolic function in 79 Andeans (18-45 years; 39 preeclamptic and 40 normotensive) living in La Paz, Bolivia (3600-4100 m) delivered by unlabored Cesarean section. Using a selection-nominated approach, we examined links between putatively adaptive genetic variation and phenotypes related to oxygen delivery or placental metabolism.

RESULTS

Mitochondrial oxidative capacity was associated with fetal oxygen delivery in normotensive but not preeclamptic placenta and was also suppressed in term preeclamptic pregnancy. Maternal haplotypes in or within 200 kb of selection-nominated genes were associated with lower placental mitochondrial respiratory capacity (PTPRD [protein tyrosine phosphatase receptor-δ]), lower maternal plasma erythropoietin (CPT2 [carnitine palmitoyl transferase 2], proopiomelanocortin, and DNMT3 [DNA methyltransferase 3]), and lower VEGF (vascular endothelial growth factor) in umbilical venous plasma (TBX5 [T-box transcription factor 5]). A fetal haplotype within 200 kb of CPT2 was associated with increased placental mitochondrial complex II capacity, placental nitrotyrosine, and GLUT4 (glucose transporter type 4) protein expression.

CONCLUSIONS

Our findings reveal novel associations between putatively adaptive gene regions and phenotypes linked to oxygen delivery and placental metabolic function in highland Andeans, suggesting that such effects may be of genetic origin. Our findings also demonstrate maladaptive metabolic mechanisms in the context of preeclampsia, including dysregulation of placental oxygen consumption.

Potential Role of Lipase Activity on the Internal Exposure Assessment of Glycidol Released from Its Fatty Acid Esters

Glycidyl fatty acid esters (GEs) can be found in food, and they can be converted into genotoxic animal carcinogen glycidol in vivo by the action of lipase. This study examined whether human ingestion of charbroiled pork containing high levels of GEs (300 µg/day) increased glycidol-hemoglobin adduct (diHOPrVal), a marker of internal exposure to glycidol using LC-MS/MS. Contrary to expectation, the diHOPrVal value before ingesting charbroiled pork was 3.11 ± 1.10 pmol/g globin, which slightly decreased to 2.48 ± 0.47 pmol/g globin after 5 days of consumption. The decrease in lipase activity caused by the continuous consumption of lipid-rich foods such as meat in humans might decrease internal exposure to glycidol released from its esters. Thus, lipase activity was measured in C57/BL6J mice fed a high-fat diet (HFD) for 8 weeks, and diHOPrVal formation was measured after the administration of glycidyl oleate. Lipase activity was significantly lower in the HFD group than in the normal diet group. The amount of diHOPrVal was reduced in the HFD group. Therefore, the lipase activity was reduced by HFD, thereby decreasing the degradation of glycidol from glycidyl oleate. These results indicate that changes in lipase activity depending on the amount of lipids in the diet may affect the assessment of GEs exposure, and monitoring the lipase activity would provide a comprehensive understanding of exposure assessment.

Carnitine supplements for people with chronic kidney disease requiring dialysis

BACKGROUND

Carnitine deficiency is common in patients with chronic kidney disease (CKD) who require dialysis. Several clinical studies have suggested that carnitine supplementation is beneficial for dialysis-related symptoms. However, the clinical effectiveness and potential adverse effects of carnitine supplementation in dialysis patients have not been determined.

OBJECTIVES

This review aimed to evaluate the effectiveness and safety of carnitine supplementation for the treatment of dialysis-related complications in CKD patients requiring dialysis.

SEARCH METHODS

We searched the Cochrane Kidney and Transplant Register of Studies up to 16 August 2022 through contact with the Information Specialist using search terms relevant to this review. Studies in the Register are identified through searches of CENTRAL, MEDLINE, and EMBASE, conference proceedings, the International Clinical Trials Register (ICTRP) Search Portal and ClinicalTrials.gov.

SELECTION CRITERIA

We included all randomised controlled trials (RCTs) and quasi-RCTs (RCTs in which allocation to treatment was obtained by alternation, use of alternate medical records, date of birth, or other predictable methods) that compared carnitine supplements with placebo or standard care in people with CKD requiring dialysis.

DATA COLLECTION AND ANALYSIS

Two authors independently extracted study data and assessed study quality. We used a random-effects model to perform a quantitative synthesis of the data.  We used the I² statistic to measure heterogeneity amongst the studies in each analysis. We indicated summary estimates as a risk ratio (RR) for dichotomous outcomes, mean difference (MD) for continuous outcomes, or standardised mean differences (SMD) if different scales were used, with 95% confidence intervals (CI). We assessed the certainty of the evidence for each of the main outcomes using the GRADE (Grades of Recommendation, Assessment, Development, and Evaluation) approach.

MAIN RESULTS

We included 52 studies (47 parallel RCTs and five cross-over RCTs) (3398 randomised participants). All studies compared L-carnitine with a placebo, other treatment, or no treatment. Standard care was continued as co-interventions in each group. Most studies were judged to have an unclear or high risk of bias. L-carnitine may have little or no effect on the quality of life (QoL) SF-36 physical component score (PCS) (4 studies, 134 participants: SMD 0.57, 95% CI -0.15 to 1.28; I² = 73%; low certainty of evidence), and the total QoL score (Kidney Disease Quality of Life (KDQOL), VAS (general well-being), or PedsQL) (3 studies, 230 participants: SMD -0.02, 95% CI -0.29 to 0.25; I² = 0%; low certainty of evidence). L-carnitine may improve SF-36 mental component score (MCS) (4 studies, 134 participants: SMD 0.70, 95% CI 0.22 to 1.18; I² = 42%; low certainty of evidence). L-carnitine may have little or no effect on fatigue score (2 studies, 353 participants: SMD 0.01, 95% CI -0.20 to 0.23; I² = 0%; low certainty of evidence), adverse events (12 studies, 1041 participants: RR, 1.14, 95% CI 0.86 to 1.51; I² = 0%; low certainty of evidence), muscle cramps (2 studies, 102 participants: RR, 0.44, 95% CI 0.18 to 1.09; I² = 23%; low certainty of evidence), and intradialytic hypotension (3 studies, 128 participants: RR, 0.76, 95% CI 0.34 to 1.69; I² = 0%; low certainty of evidence). L-carnitine may improve haemoglobin levels (26 studies, 1795 participants: MD 0.46 g/dL, 95% CI 0.18 to 0.74; I² = 86%; low certainty of evidence) and haematocrit values (14 studies, 950 participants: MD 1.78%, 95% CI 0.38 to 3.18; I² = 84%; low certainty of evidence).

AUTHORS' CONCLUSIONS

The available evidence does not currently support the use of carnitine supplementation in the treatment of dialysis-related carnitine deficiency. Although carnitine supplementation may slightly improve anaemia-related markers, carnitine supplementation makes little or no difference to adverse events. However, these conclusions are based on limited data and, therefore, should be interpreted with caution.

Significance of Levocarnitine Treatment in Dialysis Patients

Carnitine is a naturally occurring amino acid derivative that is involved in the transport of long-chain fatty acids to the mitochondrial matrix. There, these substrates undergo β-oxidation, producing energy. The major sources of carnitine are dietary intake, although carnitine is also endogenously synthesized in the liver and kidney. However, in patients on dialysis, serum carnitine levels progressively fall due to restricted dietary intake and deprivation of endogenous synthesis in the kidney. Furthermore, serum-free carnitine is removed by hemodialysis treatment because the molecular weight of carnitine is small (161 Da) and its protein binding rates are very low. Therefore, the dialysis procedure is a major cause of carnitine deficiency in patients undergoing hemodialysis. This deficiency may contribute to several clinical disorders in such patients. Symptoms of dialysis-related carnitine deficiency include erythropoiesis-stimulating agent-resistant anemia, myopathy, muscle weakness, and intradialytic muscle cramps and hypotension. However, levocarnitine administration might replenish the free carnitine and help to increase carnitine levels in muscle. This article reviews the previous research into levocarnitine therapy in patients on maintenance dialysis for the treatment of renal anemia, cardiac dysfunction, dyslipidemia, and muscle and dialytic symptoms, and it examines the efficacy of the therapeutic approach and related issues.

Serum carnitine concentration and the acyl to free carnitine ratio in nondialysis chronic kidney disease and hemodialysis patients

Mechanisms of impaired fatty acid metabolism may not be the same in nondialysis and hemodialysis patients. Correlations between the serum-free carnitine concentration (FC), acylcarnitine concentration (AC), acyl to free carnitine ratio (AC/FC), and estimated glomerular filtration rate (eGFR) in the nondialysis population and the duration of hemodialysis in hemodialysis patients were investigated. As the eGFR decreased, the FC and AC increased, and as the duration of hemodialysis became longer, the FC and AC decreased. The AC/FC increased consistently as the eGFR decreased and the duration of hemodialysis increased. As an exception, the AC/FC decreased in the patients with a hemodialysis duration less than 90 days, which was not explained by carnitine removal by hemodialysis. In nondialysis patients, a functional, rather than an absolute, carnitine deficiency is a main cause of impaired fatty acid metabolism. Long-term hemodialysis exacerbates absolute carnitine deficiency, whereas hemodialysis treatment may improve impaired fatty acid metabolism.

Protective Effects and Metabolic Regulatory Mechanisms of Shenyan Fangshuai Recipe on Chronic Kidney Disease in Rats

Background

Chronic kidney disease (CKD) is one of the major causes of renal damage. Shenyan Fangshuai Recipe (SFR), a modified prescription of traditional medicine in China, showed potent effects in alleviating edema, proteinuria, and hematuria of CKD in clinical practices. In this study, we aimed to investigate scientific evidence-based efficacy as well as metabolic regulations of SFR in CKD treatment.

Materials and Methods

The effect of SFR on CKD was observed in a rat model which is established with oral administration of adenine-ethambutol mixture for 21 days. Further, metabolites in serum were detected and identified with ultra-performance liquid chromatography-high resolution mass spectrometry (UPLC-HRMS). Metabolomics study was performed using Ingenuity Pathway Analysis (IPA) software.

Results

With H&E staining and Masson's trichrome, the results showed that chronic kidney damage is significantly rescued with SFR treatment and recovered to an approximately normal condition. Along with 44 differential metabolites discovered, the regulation of SFR on CKD was enriched in glycine biosynthesis I, mitochondrial L-carnitine shuttle pathway, phosphatidylethanolamine biosynthesis III, sphingosine-1-phosphate signaling, L-serine degradation, folate transformations I, noradrenaline and adrenaline degradation, salvage pathways of pyrimidine ribonucleotides, cysteine biosynthesis III (Mammalia), glycine betaine degradation, and cysteine biosynthesis/homocysteine degradation. Further, TGFβ-1 and MMP-9 were observed playing roles in this regulatory process by performing immunohistochemical staining.

Conclusion

SFR exerts potent effects of alleviating glomerular sclerosis and interstitial fibrosis in the kidney, mainly via integrated regulations on metabolism and production of homocysteine, L-carnitine, and epinephrine, as well as the expression of TGFβ-1. This study provides evidence for SFR's protective effects on CKD and reveals the metabolic mechanism behind these benefits for the first time.

Efficacy of L-carnitine on ribavirin-induced hemolytic anemia in patients with hepatitis C virus infection

Background/Aims

L-carnitine not only alleviates hyperammonemia and reduces muscle cramps in patients with liver cirrhosis, but also improves anemia in patients with chronic hepatitis and renal dysfunction. This study prospectively evaluated the preventative efficacy of L-carnitine supplementation against hemolytic anemia during antiviral treatment using ribavirin in patients with hepatitis C virus (HCV)-related chronic liver disease.

Methods

A total of 41 patients with chronic hepatitis were consecutively enrolled in this study. Group A (n=22) received sofosbuvir plus ribavirin for 3 months, whereas group B (n=19) was treated with sofosbuvir, ribavirin, and L-carnitine. Hemoglobin concentration changes, the effects of antiviral treatment, and the health status of patients were analyzed using short form-8 questionnaires.

Results

A significantly smaller decrease in hemoglobin concentration was observed in group B compared to group A at every time point. Moreover, the prescribed dose intensity of ribavirin in group B was higher than that of group A, resulting in a higher ratio of sustained virological response (SVR) 24 in group B compared with group A. The physical function of patients in group B was also significantly improved compared to group A at the end of antiviral treatment.

Conclusions

L-carnitine supplementation alleviates ribavirin-induced hemolytic anemia in patients with HCV and helps relieve the physical burden of treatment with ribavirin-containing regimens. These advantages significantly increase the likelihood of achieving SVR.

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.

Levocarnitine Injections Decrease the Need for Erythropoiesis-Stimulating Agents in Hemodialysis Patients with Renal Anemia

AIMS

The aim of this study was to evaluate the efficacy of levocarnitine injection for renal anemia in hemodialysis patients.

METHODS

In this randomized controlled clinical trial, we randomly assigned patients on maintenance hemodialysis at our hospital to receive levocarnitine injections (n = 30) or no injection (n = 30) and monitored the patients during 12 months of treatment. In the treatment group, patients received an injection of levocarnitine 1,000 mg 3 times weekly after hemodialysis sessions. All patients received recombinant human erythropoietin as an erythropoiesis-stimulating agent (ESA). Response to ESA therapy was determined by calculating the erythropoietin responsiveness index (ERI; ESA dose·kg^-1·g^-1· dL^-1·week^-1).

RESULTS

(1) The target levels of hemoglobin and hematocrit were maintained during the study period in both the levocarnitine group and the control group. (2) The dose of ESAs required to maintain these levels decreased gradually in the levocarnitine group and was significantly lower at 6 and 12 months than at study initiation. Furthermore, the dose of ESAs was significantly lower than that in the control group at 12 months. (3) The ERI showed a significant decrease at 6 and 12 months in the levocarnitine group, with a significant difference between the 2 groups at 12 months.

CONCLUSION

Our results suggest that levocarnitine administration can reduce the dose of ESAs required in patients with renal anemia on hemodialysis and improve the response to ESA therapy.

Levocarnitine and Dialysis: A Review

Among the various metabolic abnormalities documented in dialysis patients are abnormalities related to the metabolism of fatty acids. Aberrant fatty-acid metabolism has been associated with the promotion of free-radical production, insulin resistance, and cellular apoptosis. These processes have been identified as important contributors to the morbidity experienced by dialysis patients. There is evidence that levocarnitine supplementation can modify the deleterious effects of defective fatty-acid metabolism. Patients receiving hemodialysis and, to a lesser degree, peritoneal dialysis have been shown to be carnitine deficient, as manifested by reduced levels of plasma free carnitine and an increase in the acyl:free carnitine ratio. Cardiac and skeletal muscles are particularly dependent on fatty-acid metabolism for the generation of energy. A number of clinical abnormalities have been correlated with a low plasma carnitine status in dialysis patients. Clinical trials have examined the efficacy of levocarnitine therapy in a number of conditions common in dialysis patients, including skeletal-muscle weakness and fatigue, cardiomyopathy, dialysis-related hypotension, hyperlipidemia, and anemia poorly responsive to recombinant human erythropoietin therapy (rHuEPO). This review examines the evidence for carnitine deficiency in patients requiring dialysis, and documents the results of relevant clinical trials of levocarnitine therapy in this population. Consensus recommendations by expert panels are summarized and contrasted with present guidelines for access to levocarnitine therapy by dialysis patients.

L-carnitine supplementation improves hematological pattern in patients affected by HCV treated with Peg interferon-α 2b plus ribavirin

AIM: To evaluate the efficacy of L-carnitine on alleviating anemia, thrombocytopenia and leukopenia, and minimizing dose reductions in patients with chronic hepatitis C virus (HCV) in treatment with Interferon α (IFN-α) plus ribavirin.

METHODS: Sixty-nine patients with chronic hepatitis C were enrolled in the study and divided into two groups. group A (n = 35) received Peg-IFN-α 2b plus ribavirin plus L-carnitine, and group B (n = 34) received Peg-IFN-α and ribavirin for 12 mo. All patients underwent laboratory investigations including: red cell count, hemoglobin, white cell count, platelets, bilirubin, alanine aminotransferase (ALT), aspartate aminotransferase (AST), and viremia.

RESULTS: After 12 mo in group A compared to group B we observed significant differences in AST 108.8 vs 76.8 (IU/L; P < 0.001), ALT 137.9 vs 112.3 (IU/L; P < 0.001), viremia 4.04 vs 2.36 (× 10⁶ copies/mL; P < 0.001), Hb 1 vs 3.5 (g/dL; P < 0.05), red blood cells 0.3 vs 1.1 (× 10¹²/L; P < 0.001), white blood cells 1.5 vs 3 (× 10⁹/L; P < 0.001) and platelets 86 vs 85 (× 10⁹/L; P < 0.001). The end treatment responders were 18 vs 12 (60% vs 44%) and the non responders were 12 vs 15 (40% vs 50%) [odds ratio (OR) 1.65, 95% CI = 0.65-5.37, P < 0.05]. In group A compared to group B there was a significant improvement of sustained virological response in 15 vs 7 patients (50% vs 25%), while the relapsers were 3 vs 5 (10% vs 18%) (OR 3.57, 95% CI = 0.65-19.3, P < 0.001).

CONCLUSION: L-carnitine supplementations modulate erythropoiesis, leucopoiesis and thrombocytopoiesis, and may be useful in patients treated for HCV. L-carnitine treatment offers the possibility of achieving a sustained virological response while preventing overtreatment.

CE: Continuing Education Article: MANAGEMENT OF ANAEMIA IN CHRONIC KIDNEY DISEASE

SUMMARY Anaemia is an almost universal issue that develops in the later stages of chronic kidney disease (CKD) primarily due to a lack of erythropoietin (EPO) and the depressed EPO response in bone marrow. This can have a profound effect on the patient's lifestyle and quality of life. Knowledge of both the psychosocial and clinical areas of CKD is imperative for healthcare professionals so that they can be at the forefront of improvements of CKD patient care.

The Impact of Pre-Dialytic Endurance Training on Nutritional Status and Quality of Life in Stable Hemodialysis Patients (Sawada Study)

BACKGROUND

Protein-energy malnutrition and decreased quality of life (QOL) are common in hemodialysis (HD) patients. Although several studies have proved that regular exercise has beneficial effects, few control studies have shown the effects of exercise training on the nutritional status and QOL in HD patients.

METHODS

Fifty-five HD patients were recruited, and 22 of them were trained to exercise on an ergometer prior to dialysis three times a week for one year. Serum albumin levels, creatinine generation rate (CGR), and the Short Form 36 were assessed as outcome measures.

RESULTS

The serum albumin levels and CGR increased in the training group compared with baseline. The QOL scores also increased in half of the physical health and mental health dimensions in the training group.

CONCLUSION

These observations suggest that low-dose, long-term pre-dialytic endurance training might reverse the poor clinical outcome by improving the nutritional status and QOL in HD patients.

Endogenous plasma carnitine pool composition and response to erythropoietin treatment in chronic haemodialysis patients

BACKGROUND

Anaemia is a common complication associated with haemodialysis and is usually managed by treatment with recombinant human erythropoietin (rHuEPO). However, many patients remain hyporesponsive to rHuEPO treatment despite adequate iron therapy. The effect of L-carnitine administration on rHuEPO dose and/or haematocrit in haemodialysis patients has been previously reported with equivocal results. This study examined the relationship between endogenous carnitine pool composition and rHuEPO requirements in long-term haemodialysis patients.

METHODS

Pre-dialysis blood samples were collected from 87 patients and analysed for plasma L-carnitine and individual acylcarnitine levels by LCMS/MS. As an indication of rHuEPO responsiveness, erythropoietin resistance index (ERI) was calculated as rHuEPO dose/kg/week normalized for haemoglobin levels.

RESULTS

A significant negative correlation between L-carnitine levels and ERI was found (P = 0.0421). All patients categorized as high ERI (>0.02 microg/kg/week/gHb) exhibited subnormal L-carnitine levels (<30 microM); conversely, patients with normal L-carnitine levels (>30 microM) displayed low ERI values (<0.02 microg/kg/week/gHb). More importantly, the ratio of non-acetyl acylcarnitines/total carnitine was significantly positively correlated with ERI (P = 0.0062).

CONCLUSIONS

These data illustrate the relationship between carnitine levels and response to rHuEPO treatment in haemodialysis patients, in particular, the importance of the proportion of long-chain acylcarnitines within the plasma carnitine pool. This proportion may be more indicative of the response to L-carnitine supplementation than absolute L-carnitine levels alone.

L-carnitine supplementation in the dialysis population: are Australian patients missing out?

It has been widely established that patients with end-stage renal disease undergoing chronic haemodialysis therapy exhibit low endogenous levels of L-carnitine and elevated acylcarnitine levels; however, the clinical implication of this altered carnitine profile is not as clear. It has been suggested that these disturbances in carnitine homeostasis may be associated with a number of clinical problems common in this patient population, including erythropoietin-resistant anaemia, cardiac dysfunction, and dialytic complications such as hypotension, cramps and fatigue. In January 2003, the Centers for Medicare and Medicaid Services (USA) implemented coverage of intravenous L-carnitine for the treatment of erythropoietin-resistant anaemia and/or intradialytic hypotension in patients with low endogenous L-carnitine concentrations. It has been estimated that in the period of 1998-2003, 3.8-7.2% of all haemodialysis patients in the USA received at least one dose of L-carnitine, with 2.7-5.2% of patients receiving at least 3 months of supplementation for one or both of these conditions. The use of L-carnitine within Australia is virtually non-existent, which leads us to the question: Are Australian haemodialysis patients missing out? This review examines the previous research associated with L-carnitine administration to chronic dialysis patients for the treatment of anaemia, cardiac dysfunction, dyslipidaemia and/or dialytic symptoms, and discusses whether supplementation is warranted within the Australian setting.

Protective effect of intravenous levocarnitine on subsequent-month hospitalization among prevalent hemodialysis patients, 1998 to 2003

BACKGROUND

Levocarnitine deficiency in hemodialysis patients is common. Although the effect of intravenous levocarnitine therapy was studied in small trials, the effect on global outcomes in larger populations is unclear.

STUDY DESIGN

Retrospective observational study.

SETTING & PARTICIPANTS

Centers for Medicare & Medicaid Services data; prevalent hemodialysis patients, 1998 to 2003.

PREDICTOR

Intravenous levocarnitine use, clinical characteristics, comorbid conditions.

OUTCOMES & MEASUREMENTS

Effect of 1 g or greater per dialysis session of levocarnitine for 10 or more sessions during a month on subsequent hospitalization days. Repeated-measures and marginal structural models were fit, the latter to account for time-dependent confounding.

RESULTS

Of the study population, 3% to 7% received levocarnitine for 1 month per year or more. Treated patients were older with more severe comorbidity and larger erythropoietin doses than untreated patients. In repeated-measures model analysis adjusted for demographic characteristics and disease severity, 1 g or greater per dialysis session of levocarnitine for 10 or more sessions during a month was associated with a 10.8% (95% confidence interval, 9.7 to 11.9; P < 0.01) subsequent-month decrease in hospitalization days. In marginal structural model analysis, levocarnitine therapy was associated with a 21.7% (95% confidence interval, 18.4 to 24.9; P < 0.01) decrease in hospitalization days.

LIMITATIONS

Algorithm for identifying comorbid conditions from claims validated only for diabetes; biochemical marker levels unavailable in Medicare claims; levocarnitine therapy quantified only while patients were not hospitalized.

CONCLUSION

Because hemodialysis patients are hospitalized about 15 days yearly, the association of monthly levocarnitine regimen with lower hospitalization rate is clinically significant. The causality of this association must be confirmed by randomized clinical trials.

Supplementation of L-carnitine in athletes: does it make sense?

Studies in athletes have shown that carnitine supplementation may foster exercise performance. As reported in the majority of studies, an increase in maximal oxygen consumption and a lowering of the respiratory quotient indicate that dietary carnitine has the potential to stimulate lipid metabolism. Treatment with L-carnitine also has been shown to induce a significant postexercise decrease in plasma lactate, which is formed and used continuously under fully aerobic conditions. Data from preliminary studies have indicated that L-carnitine supplementation can attenuate the deleterious effects of hypoxic training and speed up recovery from exercise stress. Recent data have indicated that L-carnitine plays a decisive role in the prevention of cellular damage and favorably affects recovery from exercise stress. Uptake of L-carnitine by blood cells may induce at least three mechanisms: 1) stimulation of hematopoiesis, 2) a dose-dependent inhibition of collagen-induced platelet aggregation, and 3) the prevention of programmed cell death in immune cells. As recently shown, carnitine has direct effects in regulation of gene expression (i.e., carnitine-acyltransferases) and may also exert effects via modulating intracellular fatty acid concentration. Thus there is evidence for a beneficial effect of L-carnitine supplementation in training, competition, and recovery from strenuous exercise and in regenerative athletics.

Pharmacologic adjuvants to epoetin in the treatment of anemia in patients on hemodialysis

Anemia is a common complication of chronic kidney disease, particularly in patients who are on dialysis. The use of recombinant human erythropoietin has led to the eradication of severe anemia in the dialysis population. Correction of anemia in these patients has been associated with better quality of life and clinical outcomes. Some hemodialysis patients have anemia that either is relatively refractory to epoetin therapy or requires very high doses of epoetin (i.e., hyporesponsiveness), despite having adequate iron stores, and are thus unable to achieve or maintain target hemoglobin levels. Several pharmacologic agents have been studied for effects on improving response to epoetin, either to counter hyporesponsiveness or simply to reduce epoetin use for purely economic reasons. This review examines the available literature regarding the efficacy of these potential pharmacologic adjuvants to epoetin in the treatment of anemia in patients on maintenance hemodialysis, with special emphasis on androgens, vitamin C (ascorbic acid), and L-carnitine. A review of published guidelines and recommendations for use of these agents in hemodialysis patients is provided.

Veterinary hemodialysis: advances in management and technology

Hemodialysis (HD) is a renal replacement therapy that can enable recovery of patients in acute kidney failure and prolong survival for patients with end-stage kidney failure. HD is also uniquely suited for management of refractory volume overload and removal of certain toxins from the bloodstream. Over the last decade, veterinary experience with HD has deepened and refined and its geographic availability has increased. As awareness of the usefulness and availability of dialytic therapy increases among veterinarians and pet owners and the number of veterinary dialysis facilities increases, dialytic management will become the standard of advanced care for animals with severe intractable uremia.

The role of carnitine in normal and altered fatty acid metabolism

Carnitine is a low-molecular-weight compound obtained from the diet that also is biosynthesized from the essential amino acids lysine and methionine. Carnitine has been identified in a variety of mammalian tissues and has an obligate role in the mitochondrial oxidation of long-chain fatty acids through the action of specialized acyltransferases. Other roles for carnitine include buffering of the acyl coenzyme A (CoA)-CoA ratio, branched-chain amino acid metabolism, removal of excess acyl groups, and peroxisomal fatty acid oxidation. The growing body of evidence about carnitine function has led to increased understanding and identification of disorders associated with altered carnitine metabolism. Disorders of fatty acid oxidation and metabolism typically are associated with primary and secondary forms of carnitine deficiency. These disorders, which include increased lipolysis, increased lipid peroxidation, accumulation of acylcarnitines, and altered membrane permeability, have significant consequences for patients with myocardial diseases and kidney failure. Therapeutic administration of carnitine shows promise in treating selected groups of patients who have altered carnitine homeostasis, resulting in improved cardiac function, increased exercise capacity, reduced muscle cramps, and reduced intradialytic complications.

L-carnitine treatment of anemia

Recombinant human erythropoietin (rHuEPO) and iron supplementation have had a profoundly positive impact on the anemia of patients with chronic kidney disease. However, a significant number of patients remain hyporesponsive to rHuEPO, with hemoglobin values less than target levels. A suboptimal response to rHuEPO is associated with complications that can reduce quality of life and increase morbidity, mortality, and costs. There are a number of other metabolic derangements associated with uremia that can impact on the production and survival of red blood cells. Dialysis-related carnitine disorder is a functional metabolic deficiency, common in chronic dialysis patients, that can have a negative impact on erythrocyte production and survival. This article reviews the role of L-carnitine in the pathogenesis and adjunctive treatment of anemia associated with kidney failure. After a comprehensive database search, primary and secondary reports were analyzed. Laboratory studies examining the influence of carnitine on red blood cell function and clinical trials of L-carnitine in dialysis patients support the use of L-carnitine in the setting of rHuEPO hyporesponsiveness. Consensus groups, including the National Kidney Foundation-Kidney Disease Outcome Quality Initiative (K/DOQI), consider the use of L-carnitine for hyporesponsive rHuEPO-dependent anemia a promising application of this therapy, recommending an empiric trial of L-carnitine in these patients.

Carnitine and hemodialysis

Carnitine, gamma-trimethyl-beta-hydroxybutyrobetaine, is a small molecule widely present in all cells from prokaryotic to eukaryotic. It is an important element in the beta-oxidation of fatty acids. A lack of carnitine in hemodialysis patients is caused by insufficient carnitine synthesis and particularly by the loss through dialytic membranes, leading in some patients to carnitine depletion with a relative increase of esterified forms. The authors found a decrease in plasma-triglyceride and increase of high-density lipoprotein cholesterol (HDL-Chol) in dialysis patients during carnitine treatment. Many studies have shown that L-carnitine supplementation leads to improvements in several complications seen in uremic patients, including cardiac complications, impaired exercise and functional capacities, muscle symptoms, increased symptomatic intradialytic hypotension, and erythropoietin-resistant anemia, normalizing the reduced carnitine palmitoyl transferase activity in red cells. In addition, carnitine supplementation may improve protein metabolism and insulin resistance. Recently, carnitine supplementation has been approved by the US Food and Drug Administration not only for the treatment, but also for the prevention of carnitine depletion in dialysis patients. Regular carnitine supplementation in hemodialysis patients can improve their lipid metabolism, protein nutrition, antioxidant status, and anemia requiring large doses of erythropoietin, It also may reduce the incidence of intradialytic muscle cramps, hypotension, asthenia, muscle weakness, and cardiomyopathy.

History of L-carnitine: implications for renal disease

L-carnitine (LC) plays an essential metabolic role that consists in transferring the long chain fatty acids (LCFAs) through the mitochondrial barrier, thus allowing their energy-yielding oxidation. Other functions of LC are protection of membrane structures, stabilizing a physiologic coenzyme-A (CoA)-sulfate hydrate/acetyl-CoA ratio, and reduction of lactate production. On the other hand, numerous observations have stressed the carnitine ability of influencing, in several ways, the control mechanisms of the vital cell cycle. Much evidence suggests that apoptosis activated by palmitate or stearate addition to cultured cells is correlated with de novo ceramide synthesis. Investigations in vitro strongly support that LC is able to inhibit the death planned, most likely by preventing sphingomyelin breakdown and consequent ceramide synthesis; this effect seems to be specific for acidic sphingomyelinase. The reduction of ceramide generation and the increase in the serum levels of insulin-like growth factor (IGF)-1, could represent 2 important mechanisms underlying the observed antiapoptotic effects of acetyl-LC. Primary carnitine deficiency is an uncommon inherited disorder, related to functional anomalies in a specific organic cation/carnitine transporter (hOCTN2). These conditions have been classified as either systemic or myopathic. Secondary forms also are recognized. These are present in patients with renal tubular disorders, in which excretion of carnitine may be excessive, and in patients on hemodialysis. A lack of carnitine in hemodialysis patients is caused by insufficient carnitine synthesis and particularly by the loss through dialytic membranes, leading, in some patients, to carnitine depletion with a relative increase in esterified forms. Many studies have shown that LC supplementation leads to improvements in several complications seen in uremic patients, including cardiac complications, impaired exercise and functional capacities, muscle symptoms, increased symptomatic intradialytic hypotension, and erythropoietin-resistant anemia, normalizing the reduced carnitine palmitoyl transferase activity in red cells.

Plasma carnitine profile during chronic renal anemia treatment with recombinant human erythropoietin

Recombinant human erythropoietin (epoetin) is widely used for correction of anaemia in patients with chronic renal disease and its efficacy has been confirmed in numerous studies. Disturbances in carnitine metabolism may also contribute to the development of renal anaemia. Although increases in erythrocyte count (RBC) and changes in RBC metabolism during L-carnitine administration have been observed, supplementation with L-carnitine in anaemic hemodialysis patients is not routine. The aim of our study was to determine the influence of epoetin on hematological parameters and plasma carnitine profile in anaemic hemodialysis patients. 36 hemodialysis patients (22 men, 14 female, aged from 17 to 64 years, mean 43) and 30 healthy volunteers (12 men, 18 female, aged from 25 to 65 years, mean 40) were studied. Epoetin (Eprex, Janssen-Cilag) was administered subcutaneously for twelve months with the starting dose 2000 IU three times per week (range from 75 to 133, mean 102 +/- 21 IU/kg/week). The target hemoglobin (Hb) range at the time of the study was between 10-11 g/dL. Laboratory markers of hematological response, carnitine and iron status, were measured before epoetin administration and then controlled every three months. During epoetin treatment a significant increase in Hb concentration was observed (100% of patients responded to epoetin). In the third and six month of epoetin treatment, along with a significant increase in mean reticulocyte count and the highest increment of RBC count and Hb levels, probably due to increased erythropoiesis, a significant, transient decrease of mean total and free plasma carnitine levels was observed. This may suggest the utilisation of carnitine by a new RBC population. It also indicates that there is a need for L-carnitine in carnitine deficient maintenance hemodialysis patients particularily during erythropoiesis induced by epoetin treatment.