Antonino Amato

Propionyl-L-carnitine improves exercise performance and functional status in patients with claudication ∗

Abstract PURPOSE: We tested the hypothesis that propionyl-L-carnitine would improve peak walking time in patients with claudication. Secondary aims of the study were to evaluate the effects of propionyl-L-carnitine on claudication onset time, functional status, and safety. SUBJECTS AND METHODS: In this double-blind, randomized, placebo-controlled trial, 155 patients with disabling claudication from the United States (n = 72) or Russia (n = 83) received either placebo or propionyl-L-carnitine (2g/day orally) for 6 months. Subjects were evaluated at baseline and 3 and 6 months after randomization with a graded treadmill protocol at a constant speed of 2 miles per hour, beginning at 0% grade, with increments in the grade of 2% every 2 minutes until maximal symptoms of claudication forced cessation of exercise. Questionnaires were used to determine changes in functional status. RESULTS: At baseline, peak walking time was 331 ± 171 seconds in the placebo group and 331 ± 187 seconds in the propionyl-L-carnitine group. After 6 months of treatment, subjects randomly assigned to propionyl-L-carnitine increased their peak walking time by 162 ± 222 seconds (a 54% increase) as compared with an improvement of 75 ± 191 seconds (a 25% increase) for those on placebo ( P CONCLUSIONS: Propionyl-L-carnitine safely improved treadmill exercise performance and enhanced functional status in patients with claudication.

Intravenous l-carnitine increases plasma carnitine, reducesfatigue, and may preserve exercise capacity in hemodialysis patients

Exercise capacity in patients with end-stage renal disease (ESRD) remains impaired despite correction of anemia. Carnitine insufficiency may contribute to impaired exercise and functional capacities in patients with ESRD. Two randomized placebo-controlled trials were conducted to test whether intravenous L-carnitine improves exercise capacity (assessed by maximal rate of oxygen consumption [VO(2max)]) and quality of life (measured by the Kidney Disease Questionnaire [KDQ]) in patients with ESRD. In study A, patients were administered L-carnitine, 20 mg/kg (n = 28), or placebo (n = 28) intravenously at the conclusion of each thrice-weekly dialysis session for 24 weeks. In study B, a dose-ranging study, patients were administered intravenous L-carnitine, 10 mg/kg (n = 32), 20 mg/kg (n = 30), or 40 mg/kg (n = 32), or placebo (n = 33) as in study A. The prospective primary statistical analysis evaluated changes in VO(2max) in each study and specified that changes in the KDQ were assessed only in the combined populations. L-Carnitine supplementation increased plasma carnitine concentrations, but did not affect VO(2max) in either study. Because change in VO(2max) showed significant heterogeneity, a secondary analysis using a mixture of linear models approach on the combined study populations was performed. L-Carnitine therapy (combined all doses) was associated with a statistically significant smaller deterioration in VO(2max) (-0.88 +/- 0.26 versus -0.05 +/- 0.19 mL/kg/min, placebo versus L-carnitine, respectively; P = 0.009). L-Carnitine significantly improved the fatigue domain of the KDQ after 12 (P = 0.01) and 24 weeks (P = 0.03) of treatment compared with placebo using the primary analysis but did not significantly affect the total score (P = 0.10) or other domains of the instrument (P > 0.11). Carnitine was well tolerated, and no drug-related adverse effects were identified. Intravenous L-carnitine treatment increased plasma carnitine concentrations, improved patient-assessed fatigue, and may prevent the decline in peak exercise capacity in hemodialysis patients. VO(2max) in the primary analysis and other assessed end points were unaffected by carnitine therapy.

CARNITINE REPLACEMENT IN END-STAGE RENAL DISEASE AND HEMODIALYSIS

Abstract: In patients with chronic renal failure, not yet undergoing hemodialysis (HD), plasma acylcarnitines accumulate in part due to a decreased renal clearance of esterified carnitine moieties. In these patients, a high acylcarnitine/free‐carnitine ratio is usually found in plasma. Patients undergoing maintenance HD, usually present with plasma carnitine insufficiency, due to accumulation of metabolic intermediates combined with impaired carnitine biosynthesis, reduced protein intake and increased removal via HD. Plasma carnitine concentrations rapidly decrease to 40% of baseline level during the dialysis session, with a slow restoration of the carnitine concentration during the interdialytic period, mainly from organs of storage (skeletal muscle). Dietary intake also plays an important role in carnitine homeostasis of HD patients since the prevalence of malnutrition ranges from 18% to 75% of these cases. This could differentially affect various body compartments, with clinical consequences such as impaired muscle function, decreased wound healing, altered ventilatory response, and abnormal immune function. Repeated hemodialytic treatments are associated with decreased carnitine stores in skeletal muscle. The administration of intravenous l‐carnitine (LC) postdialysis replenishes the free carnitine removed from the blood and contributes to replenishment of muscle carnitine content. LC supplementation in selected uremic patients may yield clinical benefits by ameliorating several conditions, such as erythropoietin‐resistant anemia, decreased cardiac performance, intradialytic hypotension, muscle symptoms, as well as impaired exercise and functional capacities. Furthermore, LC may positively influence the nutritional status of HD patients by promoting a positive protein balance, and by reducing insulin resistance and chronic inflammation, possibly through an effect on leptin resistance.

Effects of Carnitine on Thyroid Hormone Action

Abstract: By experiments on cells (neurons, hepatocytes, and fibroblasts) that are targets for thyroid hormones and a randomized clinical trial on iatrogenic hyperthyroidism, we validated the concept that l‐carnitine is a peripheral antagonist of thyroid hormone action. In particular, l‐carnitine inhibits both triiodothyronine (T3) and thyroxine (T4) entry into the cell nuclei. This is relevant because thyroid hormone action is mainly mediated by specific nuclear receptors. In the randomized trial, we showed that 2 and 4 grams per day of oral l‐carnitine are capable of reversing hyperthyroid symptoms (and biochemical changes in the hyperthyroid direction) as well as preventing (or minimizing) the appearance of hyperthyroid symptoms (or biochemical changes in the hyperthyroid direction). It is noteworthy that some biochemical parameters (thyrotropin and urine hydroxyproline) were refractory to the l‐carnitine inhibition of thyroid hormone action, while osteocalcin changed in the hyperthyroid direction, but with a beneficial end result on bone. A very recent clinical observation proved the usefulness of l‐carnitine in the most serious form of hyperthyroidism: thyroid storm. Since hyperthyroidism impoverishes the tissue deposits of carnitine, there is a rationale for using l‐carnitine at least in certain clinical settings.

Effect of Propionyl-L-carnitine on a Background of Monitored Exercise in Patients With Claudication Secondary to Peripheral Artery Disease

PURPOSE Exercise training is established for the treatment of peripheral artery disease; however the additional benefit of pharmacologic therapy with exercise has not been studied. This trial tested the hypothesis that propionyl-L-carnitine (PLC), in combination with monitored home-based exercise training, would improve treadmill peak walking time (PWT) over exercise training alone. METHODS Subjects with claudication were randomized to 6 months of therapy with PLC (2 g daily, n = 32) or matching placebo (n = 30). After supervised exercise instruction, all subjects performed exercise training sessions 3 times a week for 30 to 50 minutes/session and compliance was monitored by activity monitors and diary. Change in PWT was the primary outcome measure with other functional assessments predefined as secondary endpoints. RESULTS After 6 months of treatment, patients randomized to training and placebo had an increase in PWT of 218 ± 367 seconds, while those randomized to training plus PLC had an increase of 266 ± 243 seconds, P = .258. Across the total study cohort, the dose of exercise training (total number of minutes of exercise of at least moderate intensity) was correlated with the change in PWT (r = 0.259, P = .048), suggesting that the monitored exercise was effective in improving walking performance in both treatment arms. CONCLUSIONS In all subjects, the increase in PWT from baseline to month 6 was correlated with the amount of exercise training. However, although favoring PLC, the combination of exercise training and PLC did not result in a statistically significant benefit in peak treadmill performance or quality of life compared with exercise alone.

Phase I and Pharmacokinetic Study of Gimatecan Given Orally Once a Week for 3 of 4 Weeks in Patients with Advanced Solid Tumors

Purpose: A phase I study was conducted to determine the dose-limiting toxicities (DLT) and maximum tolerated dose (MTD) of gimatecan, a lipophilic camptothecin analogue, administered orally once a week for 3 weeks. Experimental Design: Adult patients with advanced solid tumors with good performance status and adequate hematologic, hepatic, and renal function were eligible for the study. The plasma pharmacokinetics of the drug was characterized during the initial 28-day cycle. Results: A total of 33 patients were evaluated at 7 dose levels ranging from 0.27 to 3.20 mg/m2/wk. Anemia, fatigue, neutropenia, nausea, and vomiting were the principal toxicities. DLTs experienced by 3 of 7 patients in dose level 7 (3.20 mg/m2) were grade 2 hyperbilirubinemia and grade 3 to 4 fatigue. DLT (anorexia and nausea) occurred in only 1 of 11 patients evaluated at the MTD of 2.40 mg/m2. There were no objective responses, although disease stabilization was observed in 4 patients. Gimatecan has a very long apparent biological half-life (mean ± SD, 77 ± 37 h) and exists in plasma almost entirely as the pharmacologically active intact lactone form. At the MTD, mean peak concentrations of the drug in plasma ranged from 67 to 82 ng/mL for the 3 weekly doses and the mean concentration 7 days after dosing was 15 ± 18 ng/mL. Conclusions: Administration of gimatecan orally once a week at doses that are well tolerated provides continuous exposure to potentially effective plasma concentrations of the biologically active form of the drug. This regimen deserves further evaluation to define its antitumor activity in specific tumor types either alone or in combination with other agents.

A systematic review and meta-analysis of propionyl-l-carnitine effects on exercise performance in patients with claudication

Propionyl-l-carnitine (PLC) may improve exercise performance in patients with peripheral artery disease, but results from clinical trials have been inconsistent. The safety and efficacy of PLC for treatment of claudication was evaluated by a systematic review and meta-analysis of clinical trials for which data were available through September 2010. Eighty-five studies were identified, of which 13 were randomized controlled trials. Owing to database availability for the six phase III studies carried out with PLC (1 g orally, twice daily), a patient-level meta-analysis was conducted as the primary analysis. Treadmill performance data from these six studies were harmonized to peak walking distance (PWD) on a 7% grade at a speed of 3 km/hour. PLC (n = 440) was associated with a net 16 meter improvement (95% CI, 8–20 meters) in PWD as compared with placebo (n = 427) in the primary analysis (p = 0.002). The effect of PLC was similar in subpopulations defined using clinical and demographic variables, with possible enhanced benefit in patients engaged in an exercise program or enrolled at study sites in Russia. The systematic review of the effect of PLCs on claudication identified seven additional randomized controlled trials for a total of 13 trials, which included 681 patients on placebo and 672 on PLC. This meta-analysis confirmed a 45 meter net improvement on PLC using a random-effects model. In conclusion, oral PLC is associated with a statistically significant increase in PWD in patients with claudication, which may be clinically relevant.

Identification of rat hippocampal mRNAs altered by the mitochondrial toxicant, 3-NPA.

Abstract: 3‐Nitropropionic acid (3‐NPA) is a model mitochondrial inhibitor that causes selective neurodegeneration in brain. 3‐NPA‐induced neurodegeneration occurs via a secondary neurotoxicity, caused initially by ATP depletion and redox changes in the cell. It is known that the hippocampal degeneration caused by mitochondrial dysfunction affects learning and memory, cognitive functions commonly disturbed in neurodegenerative diseases. The 3‐NPA‐ treated animal model can be used to study molecular mechanisms underlying selective degeneration in the brain. In this study, a microarray approach was utilized to define changes in the expression of 530 genes in the rat hippocampus after acute exposure to 3‐NPA at 30 mg/kg, sc. The microarray data were collected at 30 min, 2 h, and 4 h post‐3‐NPA. Statistical modeling using an ANOVA mixed model applied to Van der Waerden scores of rank‐transformed intensity data was used to assign statistical significance to 44 transcripts. These transcripts represent genes associated with energy metabolism, calcium homeostasis, the cytoskeleton, neurotransmitter metabolism, and other cellular functions. Changes in the transcripts of genes encoding 2 transporters [blood‐brain specific anion transporter (Slco1c1) and sodium‐dependent inorganic phosphate cotransporter (Slc17a7)] were confirmed by real‐time RT‐PCR. In conclusion, this study identified 2 new potential targets for enhancement of neuroprotection or inhibition of neurodegeneration associated with ATP depletion in the hippocampus.

Co-regulation of dopamine D1 receptor and uncoupling protein-2 expression in 3-nitropropionic acid-induced neurotoxicity: neuroprotective role of L-carnitine.

This study tested the hypothesis that the expression of uncoupling proteins (UCPs) and dopamine (DA) system genes is responsive to 3-nitropropionic acid (3-NPA) neurotoxic effects and to the neuroprotective effects of the mitochondrial enhancer, L-carnitine (LC), in the rat striatum. Inactivation of mitochondrial succinate dehydrogenase (SDH) by 3-NPA results in hypoxic brain damage. Hypoxic conditions induce uncoupling protein-2 (UCP-2). An increase in UCP-2 expression may lead to a decrease in production of reactive oxygen species (ROS) associated with energy depletion. However, this adaptive response can also lead to a reduction of ATP that may further contribute to energy deficit and mitochondrial dysfunction. Here, male adult Sprague-Dawley rats (n=5/group) were injected either with saline or 3-NPA at 30 mg/kg, s.c. alone or 30 min after pre-treatment with LC (100mg/kg, i.p.). Rectal temperature was monitored before treatment and 4h following 3-NPA administration. Animals were sacrificed 4h post-treatment. Total RNA was isolated from the striatum and transcripts of UCP-2, UCP-4 and UCP-5 genes, as well as genes related to dopamine metabolism, such as DA D(1) and D(2) receptors, tyrosine hydroxylase (TH), monoamine oxidase-B (MAO-B), and vesicular monoamine transporter-2 (VMAT-2), were measured using real-time reverse transcription polymerase chain reaction (RT-PCR). While core temperature decreased significantly in 3-NPA-treated rats, LC significantly inhibited the hypothermic effect of 3-NPA (p<0.05). 3-NPA caused a significant increase in UCP-2 and DA D(1) receptor gene expression in the striatum and both effects were attenuated by pre-treatment with LC. Since LC maintains the ATP/ADP ratio and was previously shown to be neuroprotective against 3-NPA toxicity, the modulation of UCP-2 expression by LC suggests that LC counteracts energy dissipation and thus prevents the negative effects of ATP decline on DA neurotransmission.

Effects of L-carnitine pretreatment in methamphetamine and 3-nitropropionic acid-induced neurotoxicity.

Abstract:  Adult, male Sprague‐Dawley rats were injected with 3‐ni‐tropropionic acid (3‐NPA) at 30 mg/kg or methamphetamine (METH) at 20 mg/kg alone or following pretreatment with L‐cartnitine (LC) at 100 mg/kg. Rectal temperature was measured before and 4 h following treatment. Animals were sacrificed at 4 h posttreatment. Monoamine neurotransmitters, dopamine (DA) and serotonin (5‐HT), and their metabolites were analyzed in the striatum using high‐performance liquid chromatography method coupled with electrochemical detection (HPLC/ED) . Transcripts of several genes related to DA metabolism were quantified using real time reverse transciption polymerase chain reaction (RT‐PCR). Core temperature decreased significantly after 3‐NPA acid and increased in METH‐treated rats (P < 0.05). Temperature change at 4 h exhibited a significant LC effect for 3‐NPA, preventing hypothermia (P < 0.05) and no effect for METH. Concentration of DA and 5‐HT, and their metabolites, 3,4‐dihydroxyphenylacetic acid (DOPAC), homovanillic acid (HVA), and 5‐hydroxyindoleacetic acid (5‐HIAA), increased significantly in 3‐NPA and decreased in METH‐treated rats. An increase in DOPAC/DA turnover and serotonin observed after 3‐NPA was abolished in LC‐/3‐NPA‐treated rats. In both 3‐NPA‐ and METH‐treated rats, LC prevented an increase in DA receptor D1 gene expression. It appears that carnitine effect preventing hypothermia after 3‐NPA treatments may be related not only to its mitochondriotropic actions but also to inhibitory effect on the DA and 5‐HT systems activated after the exposure to 3‐NPA. The same effect observed at the transcriptional level, at least for the DA receptor D1, may account for protection against METH toxicity.