INTRODUCTION:

L-carnitine is an amino acid that is naturally produced in the body. L-carnitine supplements are used to increase L-carnitine levels in people whose natural level of L-carnitine is too low because they have a genetic disorder, are taking certain drugs (valproic acid for seizures), or because they are undergoing a medical procedure (hemodialysis for kidney disease) that uses up the body's L-carnitine. Carnitine may exist in two isomers, labeled D-carnitine and L-carnitine, as they are optically active. At room temperature, pure carnitine is a white powder, and a water soluble zwitterion with low toxicity. Carnitine only exists in animals as the L-enantiomer, and D-carnitine is toxic because it inhibits the activity of L-carnitine. Carnitine was discovered in 1905 as a result of its high concentration in muscle tissue. It was originally labeled vitamin BT; however, because carnitine is synthesized in the human body, it is no longer considered a vitamin^1,2. Carnitine is involved in the oxidation of fatty acids, and involved in systemic primary carnitine deficiency. It has been studied for preventing and treating other conditions, and is used as a purported performance enhancing drug. It is also used as a replacement supplement in strict vegetarians, dieters, and low-weight or premature infants. L-carnitine is used for conditions of the heart and blood vessels including heart related chest pain, congestive heart failure (CHF), heart complications of a disease called diphtheria, heart attack, leg pain caused by circulation problems (intermittent claudication), and high cholesterol. Some people use L-carnitine for muscle disorders associated with certain AIDS medications, difficulty fathering a child (male infertility), a brain development disorder called Rett syndrome, anorexia, chronic fatigue syndrome, diabetes, overactive thyroid, attention deficit-hyperactivity disorder (ADHD), leg ulcers, Lyme disease, and to improve athletic performance and endurance. The body can convert L-carnitine to other amino acids called acetyl-L-carnitine and propionyl-L-carnitine. But, no one knows whether the benefits of carnitines are interchangeable. Until more is known, don't substitute one form of carnitine for another. L-carnitine helps the body produce energy. It is important for heart and brain function, muscle movement, and many other body processes. Many eukaryotes have the ability to synthesize carnitine, including humans. Humans synthesize carnitine from the substrate TML (6-N-trimethyllysine), which is in turn derived from the methylation of the amino acid lysine. TML is then hydroxylated into hydroxytrimethyllysine (HTML) by trimethyllysine dioxygenase, requiring the presence of ascorbic acid. HTML is then cleaved by HTML aldose, yielding 4-trimethylaminobutyraldehyde (TMABA) andglycine. TMABA is then dehydrogenated into gamma-butyrobetaine, in an NAD+-dependent reaction, catalyzed by TMABA dehydrogenase. Gamma-butyrobetaine is then hydroxylated by gamma butyrobetaine hydroxylase into L-carnitine, requiring iron in the form of Fe2+³. Many eukaryotes have the ability to synthesize carnitine, including humans. Humans synthesize carnitine from the substrate TML (6-N-trimethyllysine), which is in turn derived from the methylation of the amino acid lysine. TML is then hydroxylated into hydroxytrimethyllysine (HTML) by trimethyllysine dioxygenase, requiring the presence of ascorbic acid. HTML is then cleaved by HTML aldose, yielding 4-trimethylaminobutyraldehyde (TMABA) andglycine. TMABA is then dehydrogenated into gamma-butyrobetaine, in an NAD+-dependent reaction, catalyzed by TMABA dehydrogenase. Gamma-butyrobetaine is then hydroxylated by gamma butyrobetaine hydroxylase into L-carnitine, requiring iron in the form of Fe2+⁴. Carnitine is involved in transporting fatty acids across the mitochondrial membrane, by forming a long chain acetylcarnitine ester and being transported by carnitine palmitoyltransferase I and carnitine palmitoyltransferase-II ⁵. Carnitine also plays a role in stabilizing Acetyl-CoA and coenzyme A levels through the ability to receive or give an acetyl group⁶.

Clinical research and therapeutic importance of carnitin:

Hemodialysis:

Since carnitine deficiency has been reported in some patients undergoing maintenance hemodialysis. Ahmad and researcher studied the effects of intravenous infusion of L-carnitine or placebo at the end of each dialysis treatment. The trial, which lasted seven months (one month baseline, 6 months treatment) was multicenter, double blind, placebo controlled, and randomized. Eighty-two long-term hemodialysis patients, who were given either carnitine (N = 38) or placebo (N = 44), completed this study. In each group, clinical and biochemical parameters during treatment were compared with baseline values. Intra-dialytic hypotension and muscle cramps were reduced only in the carnitine treated group, while improvement in post-dialysis asthenia was noticed in both carnitine and placebo groups. Maximal oxygen consumption, measured during a progressive work exercise test, improved significantly in the carnitine group (111 +/- 50 ml/min. P less than 0.03) and was unchanged in the placebo group. L-carnitine treatment was associated with a significant drop in pre-dialysis concentrations of serum urea nitrogen, creatinine and phosphorus (means +/- SEM, 101+/-4.5 to 84+/-3.9, 16.7+/-0.67 to 14.7+/-0.64, and 6.4+/-0.3 to 5.5+/-0.4 mg/dl, respectively, P less than 0.004). No significant changes in any of these variables were noticed in the placebo group. Mid-arm circumference and triceps skinfold thickness were measured in 11 carnitine and 13 placebo treated patients. Calculated mid-arm muscle area increased in the carnitine patients (41.37+/-2.68 to 45.6 +/-2.82 cm2, P = 0.05) and remained unchanged in the placebo patients⁷.

Heart Failure:

Heart failure (HF) is characterized by perturbations in energy homeostasis and metabolism. The reversibility and prognostic value of circulating markers associated with these changes remain unclear. Ahmaad and researchers sought to described the metabolomic profiles of patients along the spectrum of systolic HF, determine their association with adverse outcomes in a clinical trial of HF, and evaluate whether identified metabolites change with treatment for end-stage systolic HF. They assed association of metabolites with clinical outcomes, moreover; evaluated a population of 453 chronic systolic HF patients who had been randomized to exercise training versus usual care. To assess change in metabolites with mechanical circulatory support, 41 patients with end-stage HF who underwent left ventricular assist device (LVAD) placement were studied. Targeted, quantitative profiling of 60 metabolites using tandem flow injection mass spectrometry was performed on frozen plasma samples obtained prior to randomization, as well as prior to and >/=90 days post-placement in the LVAD group. Principal components analysis was used for data reduction. Five principal components analysis-derived factors were significantly associated with peak Vo2 levels at baseline in fully adjusted models. Of these, factor 5 (composed of long-chain acylcarnitines) was associated with increased risk of all 3 pre-specified clinical trial outcomes: all-cause mortality/all-cause hospitalization, all cause-hospitalization, and cardiovascular death or cardiovascular hospitalization. Individual components of factor 5 were significantly higher in patients with end-stage HF prior to LVAD placement and decreased significantly post-implantation. In chronic HF patients, circulating long chain acylcarnitine metabolite levels were independently associated with adverse clinical outcomes and decreased after long-term mechanical circulatory support. These metabolites may serve as potential targets for new diagnostics or therapeutic interventions⁸.

Hypothyroidism:

Hypothyroid patients experience fatigue-related symptoms despite adequate thyroid hormone replacement. Thyroid hormone plays an essential role in carnitine-dependent fatty acid import and oxidation. Kim et.al investigated the effects of L-carnitine supplementation on fatigue in patients with hypothyroidism. In total, 60 patients (age 50.0 +/- 9.2 years, 3 males, 57 females) who still experienced fatigue (fatigue severity scale [FSS] score >/= 36) were given L-carnitine (n = 30, 990 mg L-carnitine twice daily) or placebo (n = 30) for 12 weeks. After 12 weeks, although neither the FSS score nor the physical fatigue score (PFS) changed significantly, the mental fatigue score (MFS) was significantly decreased by treatment with L-carnitine compared with placebo (from 4.5 +/- 1.9 to 3.9 +/- 1.5 vs. from 4.2 +/- 1.8 to 4.6 +/- 1.6, respectively; P < 0.01). In the L-carnitine group, 75.0%, 53.6%, and 50.0% of patients showed improvement in the FSS score, PFS, and MFS, respectively, but only 20.0%, 24.0%, and 24.0%, respectively, did so in the placebo group (all P < 0.05). Both the PFS and MFS were significantly improved in patients younger than 50 years and those with free T3 >/= 4.0 pg/mL by treatment with L-carnitine compared with placebo. Additionally, the MFS was significantly improved in patients taking thyroid hormone after thyroid cancer surgery. These results suggest that L-carnitine supplementation may be useful in alleviating fatigue symptoms in hypothyroid patients, especially in those younger than 50 years and those who have hypothyroidism after thyroidectomy for thyroid cancer⁹.

Oxygen Consumption:

The effects of L-carnitine on the pyruvate dehydrogenase (PDH) complex and carnitine palmitoyl transferase (CPT) were studied in muscle of 16 long distance runners (LDR). These subjects received placebo or L-carnitine (2 g orally) during a 4-week period of training. Athletes receiving L-carnitine showed a dramatic increase (P < 0.001) in the PDH complex activities. By contrast, the levels of CPT, both 1 and 2, were unchanged. No significant changes were observed after placebo administration. It was reported that L-carnitine induces an increase in the activities of complexes I, III and IV of the respiratory chain in muscle of LDR. Taken together, our data suggest that the improvement in (maximal oxygen consumption) VO2max observed in LDR after L-carnitine administration is based on these biochemical findings¹⁰.

Anemia:

Anemia is a common disorder in CKD patients. It is largely attributed to decreased erythropoietin (EPO) production and iron deficiency. Therefore, besides EPO, therapy includes iron replenishment. However, the latter induces oxidative stress. Haptoglobin (Hp) protein is the main line of defense against the oxidative effects of Hemoglobin/Iron. There are 3 genotypes: 1-1, 2-1 and 2-2. Hp 2-2 protein is inferior to Hp 1-1 as antioxidant. So far, there is no evidence whether haptoglobin phenotype affects iron-induced oxidative stress in CKD patients. Armaly and co-workers presented study and examined the influence of carnitine treatment on the intravenous iron administration (IVIR)-induced oxidative stress in CKD patients, and whether Hp phenotype affects this response. The study included 26 anemic (Hb = 10.23 +/- 0.28) CKD patients (stages 3-4) that were given a weekly IVIR (Sodium ferric gluconate, [125 mg/100 ml] for 8 weeks, and during weeks 5-8 also received Carnitine (20 mg/kg, IV) prior to IVIR. Weekly blood samples were drawn before and after each IVIR for Hp phenotype, C-reactive protein (CRP), advanced oxidative protein products (AOPP), neutrophil gelatinase-associated lipocalin (NGAL), besides complete blood count and biochemical analyses. RESULTS: Eight percent of CKD patients were Hp1-1, 19 % Hp2-1, and 73 % Hp2-2. IVIR for 4 weeks did not increase hemoglobin levels, yet worsened the oxidative burden as was evident by elevated plasma levels of AOPP. The highest increase in AOPP was observed in Hp2-2 patients. Simultaneous administration of Carnitine with IVIR abolished the IVIR-induced oxidative stress as evident by preventing the elevations in AOPP and NGAL, preferentially in patients with Hp2-2 phenotype. CONCLUSIONS: This study demonstrates that Hp2-2 is a significant risk factor for IVIR-induced oxidative stress in CKD patients. Our finding, that co-administration of Carnitine with IVIR preferentially attenuates the adverse consequences of IVIR, suggests a role for Carnitine therapy in these patients¹¹.

Skeletal Muscles:

Berthon et al designed to compared the activity of skeletal muscle carnitine palmitoyltransferase I (CPT I) in trained and inactive men (n = 14) and women (n = 12). CPT I activity was measured in intact mitochondria, isolated from needle biopsy vastus lateralis muscle samples (approximately 60 mg). The variability of CPT I activity determined on two biopsy samples from the same leg on the same day was 4.4, whereas it was 7.0% on two biopsy samples from the same leg on different days. The method was sensitive to the CPT I inhibitor malonyl-CoA (88% inhibition) and therefore specific for CPT I activity. The mean CPT I activity for all 26 subjects was 141.1+/-10.6 micromol . min-1. kg wet muscle (wm)-1 and was not different when all men vs. all women (140.5+/-15.7 and 142.2+/-14.5 micromol . min-1 . kg wm-1, respectively) were compared. However, CPT I activity was significantly higher in trained vs. inactive subjects for both men (176.2 +/- 21.1 vs. 104.1+/-13.6 micromol . min-1 . kg wm-1) and women (167.6+/-14.1 vs. 91.2 +/- 9.5 micromol . min-1. kg wm-1). CPT I activity was also significantly correlated with citrate synthase activity (all subjects, r = 0.76) and maximal oxygen consumption expressed in milliliters per kilogram per minute (all subjects, r = 0.69). The results of this study suggest that CPT I activity can be accurately and reliably measured in intact mitochondria isolated from human muscle biopsy samples. CPT I activity was not affected by gender, and higher activities in aerobically trained subjects appeared to be the result of increased mitochondrial content in both men and women¹².

Peyronie's disease:

Biagiotti and co-workers detected whether oral acetyl-L-carnitine might be useful in the acute and early chronic phases of Peyronie's disease, compared with tamoxifen, a drug currently in use. The study included 48 patients with Peyronie's disease (15 acute and 33 initial chronic), randomized equally into two groups. The first group used tamoxifen 20 mg twice daily for 3 months and the second acetyl-L-carnitine 1 g twice daily for 3 months. The disease and stages were diagnosed and identified using a history, objective examination, pharmaco logically induced erection, autophotography during erection, and basic and dynamic colour Doppler ultrasonography. Penile curvature, plaque size, pain and disease progression were assessed. The differences between the groups or between the variables before and after therapy were compared using analysis of variance or the chi-squared test. Acetyl-L-carnitine was significantly more effective than tamoxifen in reducing pain and in inhibiting disease progression. Acetyl-L-carnitine reduced penile curvature significantly, while tamoxifen did not; both drugs significantly reduced plaque size. Tamoxifen induced significantly more side-effects than acetyl-L-carnitine. These results suggest that acetyl-L-carnitine is significantly more effective and safe than tamoxifen in the therapy of acute and early chronic Peyronie's disease¹³.

Diabetes Mellitus:

Bin and researchers explained metabolic derangements in type 2 diabetes mellitus (T2DM) are likely to affect skeletal muscle contractile functions adversely. L-carnitine improves muscle contractile functions in healthy humans and rats and corrects metabolic derangements in T2DM. Therefore, it is likely to improve muscle contractile functions in T2DM as well. This study was designed to determine the effect of L-carnitine on serum L-carnitine levels, oxidative stress and contractile parameters of fast muscle in T2DM. METHODS: Ninety Sprague-Dawley rats were randomly divided into three equal groups. Healthy rats served as the controls, while T2DM was induced in diabetic and carnitine groups. The carnitine group was administered levo-carnitine 200 mg/kg/day intraperitoneally for 6 days. At 28th day, extensor digitorum longus muscles were removed and their functions were assessed using iWorx data acquisition unit (AHK/214). Blood obtained by intra-cardiac sampling at 28th day was used for estimation of serum malondialdehyde (MDA) and levo-carnitine levels. Maximum isometric twitch tension, time-to-peak twitch tension and time-to-relax to 50% of the peak twitch tension were not significantly different amongst the groups. Carnitine group showed significant improvement in maximum fused tetanic tension, maximum fused tetanic tension after fatigue protocol and recovery from fatigue after 5 minutes of rest period compared to the diabetic group. Serum MDA levels were reduced, while serum L-carnitine levels were elevated significantly in carnitine group as compared to the diabetic group. L-carnitine supplementation increases serum L-carnitine levels which decrease oxidative stress. This action improves contractile force but delays fatigue in fast muscles of diabetic rats¹⁴.

Obstructive Pulmonary Disease:

Borghil et al described the effects of adding L-carnitine to a whole-body and respiratory training program were determined in moderate-to-severe chronic obstructive pulmonary disease (COPD) patients. Sixteen COPD patients (66+/-7 years) were randomly assigned to L-carnitine (CG) or placebo group (PG) that received either L-carnitine or saline solution (2 g/day, orally) for 6 weeks (forced expiratory volume on first second was 38 +/-16 and 36+/-12%, respectively). Both groups participated in three weekly 30-min treadmill and threshold inspiratory muscle training sessions, with 3 sets of 10 loaded inspirations (40%) at maximal inspiratory pressure. Nutritional status, exercise tolerance on a treadmill and six-minute walking test, blood lactate, heart rate, blood pressure, and respiratory muscle strength were determined as baseline and on day 42. Maximal capacity in the incremental exercise test was significantly improved in both groups (P < 0.05). Blood lactate, blood pressure, oxygen saturation, and heart rate at identical exercise levels were lower in CG after training (P < 0.05). Inspiratory muscle strength and walking test tolerance were significantly improved in both groups, but the gains of CG were significantly higher than those of PG (40+/-14 vs 14+/-5 cmH2O, and 87+/-30 vs 34+/-29 m, respectively; P<0.05). Blood lactate concentration was significantly lower in CG than in PG (1.6+/-0.7 vs 2.3+/-0.7 mM, P< 0.05). The present data suggest that carnitine can improve exercise tolerance and inspiratory muscle strength in COPD patients, as well as reduce lactate production¹⁵.

Malignant Diseases:

Abnormally low intramuscular glutamate and glutathione (GSH) levels and/or a decreased muscular uptake of glutamate by the skeletal muscle tissue have previously been found in malignant diseases and simian immunodeficiency virus (SIV) infection and may contribute to the development of cachexia. Breitkreutz tested the hypothesis that an impaired mitochondrial energy metabolism may compromise the Na+-dependent glutamate transport. A randomized double-blind clinical trial was designed to study the effects of L-carnitine, i.e. an agent known to enhance mitochondrial integrity and function, on the glutamate transport and plasma glutamate level of cancer patients. The effect of carnitine on the intramuscular glutamate and GSH levels was examined in complementary experiments with tumour-bearing mice. In the mice, L-carnitine treatment ameliorated indeed the tumour-induced decrease in muscular glutamate and GSH levels and the increase in plasma glutamate levels. The carnitine-treated group in the randomized clinical study showed also a significant decrease in the plasma glutamate levels but only a moderate and statistically not significant increase in the relative glutamate uptake in the lower extremities. Further studies may be warranted to determine the effect of L-carnitine on the intramuscular GSH levels in cancer patients¹⁶.

Bipolar Disorder:

Bipolar disorder may be associated with mitochondrial dysfunction. Therefore, agents that enhance mitochondrial functioning may be efficacious in bipolar disorder. Brennan et al performed a randomized placebo-controlled trial of the mitochondrial enhancers acetyl-L-carnitine (ALCAR) and alpha-lipoic acid (ALA) in patients with bipolar depression, and assessed markers of cerebral energy metabolism using phosphorus magnetic resonance spectroscopy. Brenen administered ALCAR (1000-3000 mg daily) plus ALA (600-1800 mg daily) or placebo for 12 weeks to 40 patients with bipolar depression and obtained imaging data at baseline, week 1, and week 12 of treatment in 20 patients using phosphorus 3-dimensional chemical-shift imaging at 4 T. Statistical analysis used random effects mixed models. We found no significant difference between ALCAR/ALA and placebo on change from baseline in the Montgomery-Asberg Depression Rating Scale in both the longitudinal (mean difference [95% confidence interval], -1.4 [-6.2 to 3.4], P = 0.58) and last-observation-carried-forward (-3.2 [-7.2 to 0.9], P = 0.12) analyses. ALCAR/ALA treatment significantly reduced phosphocreatine levels in the parieto-occipital cortex at week 12 (P = 0.002). Reduction in whole brain total nucleoside triphosphate levels from baseline to week 1 was associated with reduction in Montgomery-Asberg Depression Rating Scale scores (P = 0.02) in patients treated with ALCAR/ALA. However, this was likely a chance finding attributable to multiple statistical comparisons. Treatment with ALCAR and ALA at the dose and duration used in this study does not have antidepressant effects in depressed bipolar patients and does not significantly enhance mitochondrial functioning in this patient group¹⁷.

Peripheral Arterial Disease:

Carnitine metabolism is altered in peripheral arterial disease. L-carnitine supplementation may correct these alterations and improve walking performance. Plasma levels of carnitine and its esters were measured at rest and after maximally tolerated exercise in 22 claudicant patients and 8 normal subjects. One week later, this protocol was repeated in patients after random administration of placebo or L-carnitine (500 mg IV as a single bolus). Two groups of patients emerged. In 10 patients (group IC1), the plasma level of acetylcarnitine at rest was 3.7+/-0.2 micromol/L and increased significantly (P<.01) at maximally tolerated exercise. In 12 patients (group IC2), the resting level of plasma acetylcarnitine was elevated (7.9+/-0.7 micromol/L, P<.01) and decreased with exercise. Furthermore, group IC2 patients had a significantly lower walking capacity than group IC1 patients. In both groups, placebo did not affect the metabolic profile, nor did it improve exercise performance. Conversely, after L-carnitine administration all but one patient in group IC2 (n=7) showed an increase in plasma acetylcarnitine concentration during exercise versus the decrease observed without L-carnitine. This metabolic effect was accompanied by a significant increase (P<.01) in walking capacity. Interestingly, in group IC1 patients (n=5), L-carnitine neither improved walking capacity nor modified the metabolic profile. Statistical analysis showed that changes in walking capacity with L-carnitine treatment were influenced exclusively by exercise-induced changes in plasma acetylcarnitine. In patients with intermittent claudication, assessment of plasma acetylcarnitine at rest and after exercise may be a means to select a target population for L-carnitine therapy¹⁸.

Intermittent Claudication:

Brevetti et al performed to identify a target population of claudicants for propionyl-L-carnitine treatment. After run-in, 485 claudicant patients were randomized to placebo or propionyl-L-carnitine (1 g bid, p.o.) and then stratified on the basis of maximal walking distance (cutoff point 250 m) and maximal walking distance variability (cutoff point 25%). Treatment lasted 12 months. Walking capacity was assessed by treadmill and quality of life by a questionnaire exploring various aspects of daily life. In the target population, that is, patients who at baseline walked < or = 250 m and showed a maximal walking distance variability < or = 25%, per-protocol analysis showed that the effect of propinyl-L-carnitine was significantly greater than that with placebo for both maximal walking distance and initial claudication distance (ICD). In the intention-to-treat population, maximal walking distance increased by 62+/-14% on propionyl-L-carnitine and by 46 +/- 9% (p < 0.05) on placebo, while no difference between treatments was observed for ICD. The beneficial effect of propionyl-L-carnitine was confirmed when data of the target population were pooled with those of patients who at baseline walked < or = 250 m and showed a > 25% maximal walking distance < 50% variability. Actually, maximal walking distance increased by 98+/-16% in the propionyl-L-carnitine group and by only 54+/-10% in the placebo group (p < 0.01). The corresponding values for ICD were 99+/-21% and 51+/-8% (p < 0.05). For patients with baseline maximal walking distance > 250 m, no difference between treatments was observed. Claudicants with maximal walking distance < or = 250 m benefited from the use of propionyl-L-carnitine, with improvement in walking distance and quality of life. However, patients with mild functional impairment (i.e., walking distance > 250 m) showed no response to propionyl-L-carnitine¹⁹. The double-blind, placebo-controlled, dose titration, multicenter trial was to assess the efficacy and safety of propionyl-carnitine in intermittent claudication. Human and animal studies indicate that propionyl-L-carnitine increases carnitine content and improves energy metabolism in the ischemic skeletal muscle. After a 2-week preliminary period to assess maximal walking distance, 245 patients were randomly assigned to receive propionyl-L-carnitine (n = 118) or placebo (n = 127). The initial oral dose of 500 mg twice daily was increased at 2-month intervals to 2 g/day and then to 3 g/day in patients showing improvement in treadmill performance < 30% over baseline. Efficacy analysis was conducted for the 214 patients who completed the 24 weeks of treatment by comparing the effect of placebo and propionyl-L-carnitine on day 180. Analysis of variance showed a significant improvement of 73+/-9% (mean+/-SE) in maximal walking distance with propionyl-L-carnitine (n = 99) compared with 46+/-6% for placebo (n = 115, p = 0.03). For distance walked at onset of claudication, propionyl-L-carnitine showed about double the improvement of placebo; however, the difference was not statistically significant. There were no changes in electrocardiographic and routine biochemical and hematologic tests that would indicate an adverse effect of propionyl-L-carnitine. Adverse events requiring drug discontinuation (11 in the propionyl-L-carnitine group, 3 in the placebo group) were unrelated to study medication. The dose titration design of the study also provided information on the dose-response relation. Slightly less than 67% of patients were expected to improve their maximal walking distance by at least 30%, assuming 2 g/day of propionyl-L-carnitine (95% confidence interval 0.51 to 0.70). The response rate during the entire titration course was significantly in favor of propionyl-L-carnitine compared with placebo. Although the precise mode of therapeutic action requires clarification, propionyl-L-carnitine, at a dose of 1 to 2 g/day, appears to be effective and well tolerated, with minimal adverse effects²⁰.

Multiple Myeloma:

Retreatment with bortezomib (B) is often considered for patients with relapsed multiple myeloma (MM), but this strategy is hindered by uncertainty of response and emergence of B-induced peripheral neuropathy (PN). Callander et al incorporated acetyl-L-carnitine (ALCAR) to prevent PN and allow for adequate dosing. It was also investigated the correlation between B-inducible NF-kappaB activation and response to therapy. METHODS: Nineteen patients with relapsed/refractory MM received up to 8 cycles of intravenous bortezomib, doxorubicin and oral low-dose dexamethasone (BDD) to evaluate response and toxicity. Thirteen additional patients received prophylactic ALCAR (BDD-A). Patients receiving BDD-A were evaluated by FACT-GOG-TX, FACIT-Fatigue, Neuropathic Pain index (NPI) and Grooved Pegboard (GP) testing. Primary MM cells from 11 patients were tested for B-inducible NF-kappaB activation. RESULTS: Seventy-six percent of subjects were refractory to previous treatment, 39% refractory to bortezomib. Median cycles received were 5. CR + PR for the entire group were 53% and did not differ between groups. Incidence of >/=3 PN was 32% in the BDD group versus 15 % in the BDD-A group (p = ns). Patient-reported fatigue and PN measured by FACT-GOG-TX increased throughout the treatment period in the BDD-A group, although time to complete GP testing declined. In a sub-study examining constitutive bortezomib-inducible NF-kappaB activity in primary subject-specific MM cells, the presence of NF-kappaB activation correlated with lower likelihood of response. CONCLUSIONS: Addition of ALCAR to BDD did not alter the incidence or severity of PN in relapsed MM patients receiving a B-based regimen. Bortezomib-inducible NF-kappaB activation in patient-derived primary MM cells may be associated with poorer response²¹.

Fragile X syndrome:

Hyperactivity is a significant problem for almost all young males affected by fragile X syndrome (FXS), the most common inherited disease causing mental retardation. Therapeutical approaches are actually based on Central Nervous System (CNS) stimulants lacking a well defined rationale and efficacy while they further decrease the patient's limited attention span. A pilot study on 17 fragile X male treated with L-acetylcarnitine (LAC) over one year, showed a significant reduction of their hyperactivity behaviour tested by the Conners Abbreviated Parent-Teacher Questionnaire. LAC use in FXS patients derives from the hypothesis that the biochemical and physiological properties this substance has may preserve brain activity. LAC is a small, hydrosoluble molecule that easily diffuses in the extracellular space and enters any cell in the nervous system through specific transporters. Different cerebral areas use this molecule differently to metabolize glucose and lipids to provide for ATP and neurotrasmitters synthesis. The acetyl group LAC carriers represents a key metabolic signaling element possibly mediating its effect in the CNS. The exogenous administration of LAC may affect brain activity in FXS by: I) modulation of fuel partitioning for energy production, which at the mithocondrial level is associated with the Kreb's cycle metabolic role in neurotransmitter synthesis; II) remodelling of lipid membrane in terms of LAC actively determining the production of polyunsaturated fatty acids; III) preferential effect on the attention component of the cholinergic system which relies on its peculiar modality of communication in the CNS. Based on the above premises an explorative, double-blind, placebo controlled, multicenter study is ongoing. A total population of 160 children from nine European centers will be enrolled. The objective of this study is to determine the effect of LAC on the hyperactive behaviour of FXS children as evaluated by the administration of the Conners Abbreviated Parent Questionnaire²².

Peripheral neuropathy:

Peripheral neuropathy (PN) is a recognized side effect of microtubule-targeting agents and the most clinically relevant toxicity observed with the epothilone sagopilone (SAG). Studies suggest that acetyl-L-carnitine (ALC) may prevent chemotherapy-induced PN. Campone and co-workers conducted a prospective, placebo (PBO)-controlled, double-blind, randomized trial to investigate the safety and efficacy of ALC for the prevention of SAG-induced PN. Methods. Patients with ovarian cancer (OC) or castration-resistant prostate cancer (CRPC) and no evidence of neuropathy received SAG (16 mg/m(2) intravenously over 3 hours every 3 weeks) with ALC (1,000 mg every 3 days) or placebo (PBO). The primary endpoint was incidence of PN within six or fewer cycles in both treatment groups. Results. Overall, 150 patients enrolled (98 OC patients, 52 CRPC patients), with 75 per treatment arm. No significant difference in overall PN incidence was observed between treatment arms. The incidence of grade >/=3 PN was significantly lower in the ALC arm in OC patients. Median duration of neuropathy was similar between treatment arms. The best overall response (according to the modified Response Evaluation Criteria in Solid Tumors), response according to tumor markers, time-to-event variables, and discontinuations because of adverse events (AEs) were comparable between treatment arms. Conclusion. Administration of ALC with SAG did not result in a significant difference in overall PN incidence compared with a PBO. OC patients in the SAG/ALC arm had a significantly lower incidence of grade 3 or 4 PN compared with OC patients in the SAG/PBO arm²³.

Antioxidant activity:

L-carnitine has been used as a supplement to treat cardiovascular or liver disease. However, Cao et al explained 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 micromol/L. After single oral administration, the maximum plasma concentration (C(max)) and area under the curve (AUC(0-infinity)) were 84.7+/-25.2 micromol/L and 2,676.4+/-708.3 micromol/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 stress²⁴ .

Oligoasthenospermia:

Cavallini et al detected a therapy for idiopathic and varicocele-associated oligoasthenospermia (OAT). Idiopathic and varicocele OAT patients were randomized into 3 groups. Each group was composed of varying degrees of left varicoceles (graded into 5 grades with echo-color Doppler) and of idiopathic OATs. Group 1 used a placebo, group 2 used oral L-carnitine (2 g/d) + acetyl-L-carnitine (1g/d), group 3 used L-carnitine /acetyl-L-carnitine + 1 x 30-mg cinnoxicam suppository every 4 days. Drugs were administered for 6 months. The groups were composed as follows: group 1, 71 varicoceles and 47 idiopathic OATs; group 2, 62 varicoceles and 39 idiopathic OATs; group 3, 62 varicoceles and 44 idiopathic OATs. Sperm concentration, motility, and morphology before during and after treatments were assessed. Pregnancy rates and side effects were recorded. Group 1 did not have modified sperm patterns during treatment. Group 2 had significantly increased sperm patterns at 3 and 6 months into therapy in idiopathic patients and in patients with grades I, II, and III varicocele, but not in grades IV and V. Group 3 had significantly increased sperm parameters in all patients, with the exception of grade V varicocele. Group 3 sperm patterns proved significantly higher during therapy than group 2. All sperm patterns fell to baseline after therapy suspension. Minor side effects occurred. Pregnancy rates were 1.7% (group 1), 21.8% (group 2), and 38.0% (group 3) (P<.01). L-carnitine/acetyl-L-carnitine + cinnoxicam suppositories proved a reliable treatment for low-grade varicoceles and idiopathic OATs²⁵.

Weight loss:

The efficacy, safety, and metabolic consequences of rapid weight loss in privately owned obese cats by means of a canned weight-reduction diet and the influence of orally administered L-carnitine on rate of weight loss, routine clinical evaluations, hepatic ultrasonography, plasma amino acid profiles, and carnitine analytes were evaluated. A double-blinded placebo-controlled design was used with cats randomly divided into 2 groups: Group 1 (n=14) received L-carnitine (250 mg PO q24h) in aqueous solution and group 2 (n=10) received an identical-appearing water placebo. Median obesity (body condition scores and percentage ideal body weight) in each group was 25%. Caloric intake was restricted to 60% of maintenance energy requirements (60kcal/kg) for targeted ideal weight. The reducing formula was readily accepted by all cats. Significant weight loss was achieved by week 18 in each group without adverse effects (group 1 = 23.7%, group 2 = 19.6%). Cats receiving carnitine lost weight at a significantly faster rate (P < .05). Significant increases in carnitine values developed in each group (P < .02). However, significantly higher concentrations of all carnitine moieties and a greater percentage of acetyl carnitine developed in cats of group 1 (P < .01). The dietary formula and described reducing strategy can safely achieve a 20% weight reduction within 18 weeks in obese cats. An aqueous solution of L-carnitine (250 mg PO q12h) was at least partially absorbed, was nontoxic, and significantly increased plasma carnitine analyte concentrations as well as rate of weight loss²⁶.

Epilepsy:

Serum concentrations of total carnitine, free carnitine and acylcarnitine were measured in forty-one epileptic patients treated with valproic acid (VPA). Among them, 14 patients were on VPA monotherapy and 27 were on VPA polytherapy. Forty-one age and sex matched healthy normal controls were also evaluated for carnitine metabolism. The mean total and free carnitine were significantly lower in both the VPA monotherapy and polytherapy groups compared with the controls. However, there were no significant differences in concentrations of carnitine between the VPA polytherapy and VPA monotherapy groups. Patients treated with VPA polytherapy had lower carnitine than those treated with VPA monotherapy. An inverse correlation was found between serum concentrations of carnitine and duration of treatment in patients treated with VPA. However, there was no significant correlations between serum concentrations of carnitine and those of VPA. Also, correlation between serum concentrations of carnitine and the activities of serum GOT and GPT was not significant. After L-carnitine supplementation in eleven patients with hypo carnitinemia, the concentrations of carnitine were significantly increased²⁷.

Fatigue:

L-carnitine, a popular complementary and alternative medicine product, is used by patients with cancer for the treatment of fatigue, the most commonly reported symptom in this patient population. The purpose of this study was to determine the efficacy of L-carnitine supplementation as a treatment for fatigue in patients with cancer. In this double-blind, placebo-controlled trial, patients with invasive malignancies and fatigue were randomly assigned to either 2 g/d of L-carnitine oral supplementation or matching placebo. The primary end point was the change in average daily fatigue from baseline to week 4 using the Brief Fatigue Inventory (BFI). Three hundred seventy-six patients were randomly assigned to treatment with L-carnitine supplementation or placebo. L-carnitine supplementation resulted in significant carnitine plasma level increase by week 4. The primary outcome, fatigue, measured using the BFI, improved in both arms compared with baseline (L-carnitine: -0.96, 95% CI, -1.32 to -0.60; placebo: -1.11, 95% CI -1.44 to -0.78). There were no statistically significant differences between arms (P=.57). Secondary outcomes, including fatigue measured by the Functional Assessment of Chronic Illness Therapy-Fatigue instrument, depression, and pain, did not show significant difference between arms. A separate analysis of patients who were carnitine-deficient at baseline did not show statistically significant improvement in fatigue or other outcomes after L-carnitine supplementation. Four weeks of 2 g of L-carnitine supplementation did not improve fatigue in patients with invasive malignancies and good performance status²⁸.

Carpal tunnel syndrome:

Carpal tunnel syndrome (CTS) is the most common form of peripheral nerve injury, affecting approximately 3 % of the population. While surgery is effective in mild and moderate cases, nerve and functional recovery are often not complete in severe cases. Therefore, there is a need for adjuvant methods to improve nerve regeneration in those cases. Acetyl-L-carnitine (ALCAR) is involved in lipid transport, vital for mitochondrial function. Although it has been shown to be effective in various forms of neuropathies, it has not been used in traumatic or compressive peripheral nerve injury. In this pilot study we will utilize a double-blind, randomized, placebo-controlled design. Inclusion criteria will include adult patients with severe CTS. This will be confirmed by nerve conduction studies and motor unit number estimation (MUNE). Only those with severe motor unit loss in the thenar muscles (2 standard deviations [SD] below the mean for the age group) will be included. Eligible patients will be randomized to receive 3,000 mg/day of ALCAR orally or placebo following carpal tunnel release surgery for 2 months. The primary outcome will be MUNE with supplementary secondary outcome measures that include:1) two-point discrimination; 2) Semmes-Weinstein monofilaments for pressure sensitivity; 3) cold and pain threshold for small fiber function; 4) Boston self-assessment Carpal Tunnel Questionnaire and 5) Disabilities of the Arm, Shoulder and Hand (DASH) questionnaire for symptom severity; and 6) Purdue Pegboard Test for hand functional performance. To follow post treatment recovery and monitor safety, patients will be seen at 3 months, 6 months and 1 year. The outcome measures will be analyzed using two-way ANOVA, with treatment assignment and time points being the independent factors. If significant associations are detected, a post hoc analysis will be completed. We aim to recruit ten patients into each of the two groups. Data from this pilot will provide the basis for power calculation for a full-scale trial. ALCAR is a physiologic peptide crucial for fatty acid transport. ALCAR has been shown to be effective in neuroprotection in the central nervous system and increase peripheral nerve regeneration. This has been applied clinically to various systemic peripheral neuropathies including diabetic neuropathy, antiretroviral toxic neuropathy, and chemotherapy-induced peripheral neuropathy. While animal evidence exists for the benefit of ALCAR in compression neuropathy, there have been no human studies to date. This trial will represent the first use of ALCAR in peripheral nerve injury/compression neuropathy²⁹.

Lipid control, and insulin resistance state in type 2 diabetic:

Derosa and researcher evaluated the effects of one year treatment with orlistat plus L-carnitine compared to orlistat alone on body weight, glycemic and lipid control, and insulin resistance state in type 2 diabetic patients. Two hundred and fifty-eight patients with uncontrolled type 2 diabetes mellitus (T2DM) [glycated hemoglobin (HbA(1c))>8.0%] in therapy with different oral hypoglycemic agents or insulin were enrolled in this study and randomised to take orlistat 120 mg three times a day plus L-carnitine 2 g one time a day or orlistat 120 mg three times a day. They evaluated at baseline, and after 3, 6, 9, and 12 months these parameters: body weight, body mass index (BMI), HbA(1c), fasting plasma glucose (FPG), post-prandial plasma glucose (PPG), fasting plasma insulin (FPI), homeostasis model assessment insulin resistance index (HOMA-IR), total cholesterol (TC), low density lipoprotein-cholesterol (LDL-C), high density lipoprotein-cholesterol (HDL-C), triglycerides (Tg), retinol binding protein-4 (RBP-4), resistin, visfatin, high sensitivity-C reactive protein (Hs-CRP). It was observed a faster, and better decrease of body weight, HbA(1c), FPG, PPG, LDL-C, HOMA-IR with orlistat plus L-carnitine compared to orlistat. A faster improvement of TC, Tg, FPI, resistin, RBP-4, visfatin, and Hs-CRP was reached with orlistat plus L-carnitine compared to orlistat. It can safely conclude that the association of orlistat plus L-carnitine was better than orlistat in improving body weight, glycemic and lipid profile, insulin resistance, and inflammatory parameters and no significant adverse events were recorded [30]. Two hundred and fifty-four patients with uncontrolled type 2 diabetes mellitus (T2DM) [glycated hemoglobin (HbA(1c))>8.0%] in therapy with different oral hypoglycemic agents or insulin were enrolled in this study and randomised to take sibutramine 10 mg plus L-carnitine 2 g or sibutramine 10 mg in monotherapy. They evaluated at baseline, and after 3, 6, 9, and 12 months these parameters: body weight, body mass index (BMI), glycated hemoglobin (HbA(1c)), fasting plasma glucose (FPG), post-prandial plasma glucose (PPG), fasting plasma insulin (FPI), homeostasis model assessment insulin resistance index (HOMA-IR), total cholesterol (TC), low density lipoprotein-cholesterol (LDL-C), high density lipoprotein-cholesterol (HDL-C), triglycerides (Tg), retinol binding protein-4 (RBP-4), resistin, visfatin, high sensitivity-C reactive protein (Hs-CRP). There was a decrease in body weight, BMI, HbA(1c), FPI, HOMA-IR, and RBP-4 in both groups, even when the values obtained with sibutramine plus L-carnitine were lower than the values obtained in sibutramine group. There was a faster decrease of FPG, PPG, TC, LDL-C, resistin and Hs-CRP with sibutramine plus L-carnitine even when no differences between the two groups were obtained. Furthermore, only sibutramine plus L-carnitine improved Tg, and visfatin. Sibutramine plus L-carnitine gave a faster improvement of lipid profile, insulin resistance parameters, glycemic control, and body weight compared to sibutramine³¹.

Resting metabolic rate and oxidation of free fatty acids:

Faria et al investigated the effects of L-carnitine supplementation, over thirty days, on the resting metabolic rate (RMR) and oxidation of free fatty acids (FFA) under rested or exercised conditions. SUBJECTS AND Twenty-one overweight active volunteers (40 to 58 years old) were randomized into two groups: supplemented (GS; N = 11; 1,8 g/day of L-carnitine) or placebo (GP; N = 10; maltodextrin). Caloric intake, anthropometry, RMR, VO(2max), respiratory exchange ratio and plasma FFA were measured. No significant changes were found in the caloric intake (-244,66 vs. -126,00 kcal/day), body composition (-0.07 vs. -0.17 kg/m(2)), RMR (0.06 vs. -0.02 kcal/day), respiratory exchange ratio at rest (3.69 vs. -1.01) and exercise (0.01 vs. -0.01) or VO(2max) (0.50 vs. 1.25 mL/kg/min) between GS and GP. Plasma FFA levels were increased under resting conditions only in the GP group (0.27), but no significant changes were observed before or after physical activity in any of the groups. Supplementation with L-carnitine caused no changes in the variables analyzed in this study³².

Normoxic and hypoxic conditions:

Skeletal muscle CoA and carnitine metabolism were investigated in six human volunteers at rest and after exhaustive exercise under normoxic and hypoxic conditions. In comparison to the values at rest, exhaustive exercise was associated with a three- to fourfold increase in the skeletal muscle lactate, and with a twofold increase in the acetyl-CoA content, both under normoxic and hypoxic conditions. Since exercise did not significantly affect the skeletal muscle CoA radical (CoASH), total acid-soluble, or total CoA contents, the increase in the acetyl-CoA content was at the expense of short-chain acyl-CoAs different from acetyl-CoA. With exhaustive exercise, the skeletal muscle acetylcarnitine and short-chain acylcarnitine contents increased by a factor of three to four both under normoxic and hypoxic conditions. In contrast to the CoA pool, these increases were associated with a decrease in the free carnitine content, whereas the total acid-soluble and total carnitine contents were not affected by exercise. After exhaustive exercise, the skeletal muscle acetyl-CoA/CoASH ratio showed a linear correlation with the corresponding acetylcarnitine/free carnitine ratio. The plasma short-chain acylcarnitine concentration increased by a factor of two to three during exercise, and was not significantly different from the values at rest 40 min after completion of exercise. Thus, the current studies illustrate the close interaction between the CoA and carnitine pools in the exercising human skeletal muscle, and they underscore the important role of carnitine in maintaining the muscular CoASH content during exhaustive exercise³³.

Autism spectrum disorder:

L-carnitine was proposed as a potential treatment for patients diagnosed with an autism spectrum disorder to improve mitochondrial dysfunction, but no prior randomized controlled trials have been conducted. Thirty subjects diagnosed with an ASD were randomly assigned to receive a standardized regimen (50 mg L-carnitine/kg bodyweight/day) of liquid L-carnitine (n=19) or placebo (n=11) for 3-months. Measures included changes in professionally completed Childhood Autism Rating Scale (CARS), hand muscle testing, and modified clinical global impression (CGI) forms; parent completed Autism Treatment Evaluation Checklist (ATEC), treatment adherence measurement (TAM), frequency and intensity of side effect rating (FISER)/global rating of side effect burden (GRSEB)/patient report of incidence of side effects (PRISE) forms; and lab testing. Significant improvements were observed in CARS (-2.03, 95% CI=-3.7 to -0.31), CGI (-0.69, 95% CI=-1.1 to -0.06), and ATEC scores. Significant correlations between changes in serum free-carnitine levels and positive clinical changes were observed for hand muscle strength (R2=0.23, P=0.046), cognitive scores (R2=0.27, P=0.019), and CARS scores (R2=0.20, P=0.047). Study subjects were protocol-compliant (average adherence was >85%) and generally well-tolerated the L-carnitine therapy given.: L-carnitine therapy (50 mg/kilogram-bodyweight/day) administered for 3-months significantly improved several clinical measurements of ASD severity, but subsequent studies are recommended³⁴.

CONCLUSION:

Carnitine is a quaternary ammonium compound involved in metabolism in most mammals, plants and some bacteria. Carnitine may exist in two isomers, labeled D-carnitine and L-carnitine, as they are optically active. L-carnitine is a naturally occurring amino acid derivative that’s often taken as a weight loss supplement. It plays a crucial role in the production of energy by transporting fatty acids into your cells’ mitochondria. The mitochondria act as engines within cells, burning these fats to create usable energy. Basically body can actually produce L-carnitine out of the amino acids lysine and methionine with use of plenty if vitamin C. In addition to the L-carnitine produced in the body, but also consume small amounts from the diet by eating animal products like meat or fish. L-carnitine is a naturally occurring amino acid derivative that’s often taken as a weight loss supplement. Most research suggests that taking L-carnitine by mouth or intravenously (by IV) can improve red blood cell counts during hemodialysis. The US Food and Drug Administration (FDA) has approved L-carnitine for the treatment and prevention of L-carnitine deficiency in people with serious kidney disease who are undergoing hemodialysis.L-carnitine deficiency. The FDA has approved L-carnitine for treating L-carnitine deficiency caused by certain genetic diseases. Taking L-carnitine by mouth seems to improve exercise tolerance in people with chest pain because it seems to reduce chest pain and improve exercise ability in people who have chest pain but not blocked arteries. L-carnitine by mouth seems to improve symptoms and increase exercise ability in people with heart failure. Taking L-carnitine seems to improve symptoms such as rapid or pounding heartbeat, nervousness, and weakness in people with high thyroid hormone levels. Most research shows that taking L-carnitine, alone or in combination with acetyl-L-carnitine, increases sperm count and sperm movement in men with fertility problems. Taking L-carnitine by mouth seems to reduce the risk of death from myocarditis.

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Received on 23.07.2017 Accepted on 21.10.2017

Asian J. Pharm. Res. 2017; 8(1): 47-58.

DOI: 10.5958/2231-5691.2018.00010.2