Risk assessment for carnitine

Effect of exogenous l-carnitine on aortic stiffness in dyslipidemic adolescents: Design of a quadruple-blind, randomized, controlled interventional trial

Background

Atherosclerotic cardiovascular disease (ASCVD) risk factors including vascular remodeling leading to hypertension and dyslipidemia are prevalent among children and adolescents. Conflicting observational and Mendelian randomization data suggest endogenous carnitine may affect arterial stiffness and lipid traits. Because of this, we developed a study to evaluate the causal role for carnitine in arterial stiffness at a point when the lifecourse trajectory to hypertension can be modified.

Methods

This study is a mechanistic, double-blinded, randomized control trial (RCT) in 166 adolescents with dyslipidemia for the effect of 6 months of maximum dose 3 g daily oral l-carnitine supplementation (CS+) versus placebo (CS-) on aortic stiffness measured as carotid-femoral pulse wave velocity (CFPWV) and pulse pressure (PP); lipid concentrations (total cholesterol, HDL-C, triglycerides, and LDL-C) and serum fatty acid oxidation biomarkers by metabolomic analysis.

Conclusions

The simultaneous evaluation of endogenous carnitine genetic effects and exogenous l-carnitine supplementation may facilitate future therapies for youth with cardiometabolic derangement to arrest atherosclerotic changes.

l-carnitine: Nutrition, pathology, and health benefits

Carnitine is a medically needful nutrient that contributes in the production of energy and the metabolism of fatty acids. Bioavailability is higher in vegetarians than in people who eat meat. Deficits in carnitine transporters occur as a result of genetic mutations or in combination with other illnesses such like hepatic or renal disease. Carnitine deficit can arise in diseases such endocrine maladies, cardiomyopathy, diabetes, malnutrition, aging, sepsis, and cirrhosis due to abnormalities in carnitine regulation. The exogenously provided molecule is obviously useful in people with primary carnitine deficits, which can be life-threatening, and also some secondary deficiencies, including such organic acidurias: by eradicating hypotonia, muscle weakness, motor skills, and wasting are all improved l-carnitine (LC) have reported to improve myocardial functionality and metabolism in ischemic heart disease patients, as well as athletic performance in individuals with angina pectoris. Furthermore, although some intriguing data indicates that LC could be useful in a variety of conditions, including carnitine deficiency caused by long-term total parenteral supplementation or chronic hemodialysis, hyperlipidemias, and the prevention of anthracyclines and valproate-induced toxicity, such findings must be viewed with caution.

Serum L-Carnitine Levels Are Associated With First Stroke in Chinese Adults With Hypertension

BACKGROUND

This study aimed to evaluate the association of serum L-carnitine with first stroke and explore potential effect modifiers.

METHODS

This is a nested, case-control study drawn from the China Stroke Primary Prevention Trial among rural Chinese adults with hypertension, including 557 first stroke cases and 557 age-matched, sex-matched, treatment group-matched, and residence-matched controls. Serum L-carnitine was measured by liquid chromatography with tandem quadrupole mass spectrometry. Multiple conditional logistic regression models were used to evaluate the association between L-carnitine and first stroke.

RESULTS

The mean level of serum L-carnitine in the stroke population was 4.7 μg/mL, which was significantly lower than that of the control group (5.7 μg/mL). When L-carnitine was assessed as quintiles, compared with the reference group (quintile 1, <3.3 μg/mL), the odds of stroke were 0.62 (95% CI, 0.39-1.00) in quintile 2, 0.66 (95% CI, 0.40-1.10) in quintile 3, 0.47 (95% CI, 0.28-0.81) in quintile 4, and 0.50 (95% CI, 0.30-0.84) in quintile 5. The trend test was significant (P=0.01). When quintiles 2 to 5 were combined, the adjusted odds ratio of first stroke was 0.58 (95% CI, 0.38-0.87) compared with quintile 1. Similar associations were found for ischemic stroke and hemorrhagic stroke. In subgroup analysis, a significant L-carnitine-stroke association was only observed in the normal folate group (P interaction, 0.039) and in the MTHFR CC genotype group (P interaction, 0.047).

CONCLUSIONS

In this study of rural Chinese adults with hypertension, serum L-carnitine had an inverse but nonlinear association with first stroke. Folate status and the MTHFR C677T variant were significant effect modifiers of the association.

The effects of L-carnitine supplementation on inflammatory factors, oxidative stress, and clinical outcomes in patients with sepsis admitted to the intensive care unit (ICU): study protocol for a double blind, randomized, placebo-controlled clinical trial

BACKGROUND

Sepsis is a common cause for admission to the intensive care unit (ICU), and its incidence has been increasing. It is associated with a significant increase in serum inflammatory biomarkers such as C-reactive protein (CRP) and cytokines such as interleukin 1 (IL-1), IL-6, and tumor necrosis factor (TNF). Sepsis is also associated with pathophysiological changes that include fluid accumulation in the lungs, eventually leading to acute respiratory distress syndrome (ARDS), tissue edema, hypotension, and acute kidney injury (AKI). Conventional therapies include antibiotics, but these may have important adverse effects, so novel therapeutic approaches are required. In animal studies, L-carnitine improves antioxidant status, and in some clinical trials, it has been shown to reduce inflammation. It has also been shown to improve respiratory distress and help maintain coenzyme A homeostasis, metabolic flexibility, promoting the normal function of the tricarboxylic acid (TCA) cycle, and oxidation of fatty acids by peroxisomes. We aim to determine the effects of very high doses of L-carnitine on inflammatory factors, oxidative stress, and clinical outcomes of patients with sepsis in ICU.

METHOD AND DESIGN

In this double-blind, randomized controlled clinical trial, we will use block randomization of 60 patients with sepsis, aged between 20 and 65 years from Al-Zahra Hospital, Isfahan, Iran. The intervention group (n = 30) will receive three capsules of L-carnitine (each capsule contains 1000 mg L-carnitine; totally 3000 mg/day) for 7 days, and a control group (n = 30) will receive a placebo with the same dose and for the same duration in addition to usual care. At baseline, scores for clinical and nutritional status (Acute Physiology and Chronic Health Evaluation II (APACHE II), Sequential Organ Failure Assessment (SOFA), Quick SOFA (qSOFA), and NUTRIC Score) will be assessed. At beginning and end point of the study, inflammatory markers (CRP, erythrocyte sedimentation rate (ESR)), oxidative stress status (total oxidative stress (TOS), total antioxidant capacity (TAC)), and clinical variables will be evaluated also. The mortality rate will be assessed within 28 days of the beginning of the intervention.

DISCUSSION

Because of the anti-inflammatory and antioxidant properties of L-carnitine, it is possible that using a high dose of 3000 mg daily of this nutritional supplement may reduce inflammation and oxidative stress and improve subsequent mortality of critically ill patients with sepsis.

TRIAL REGISTRATION

Iranian Registry of Clinical Trials IRCT20201129049534N1 . Registered on 2 May 2021.

Adverse effects associated with use of specific dietary supplements: The US Military Dietary Supplement Use Study

Dietary supplements (DSs) are used by 50% of Americans and 70% of United States military service members (SMs); some have adverse effects (AEs). This cross-sectional investigation examined AEs associated with specific DSs. A stratified random sample of SMs from the Air Force, Army, Marine Corps, and Navy was obtained. Volunteers completed a questionnaire reporting AEs for 96 generic and 62 specific DSs. The highest prevalence (≥1 AE) in specific DS categories was 35% prohormones, 33% weight loss supplements, 26% pre/post workout supplements, 14% herbal products, 12% multivitamin/multiminerals, 11% protein/amino acids, 9% muscle building supplements, 7% other DSs, 6% joint health products, and 5% individual vitamins/minerals. Specific DSs of concern (with proportion reporting AEs) included: Libido Max® (35%), Hydroxycut Hardcore® (33%), OxyElite® (33%), Roxylean® (31%), Growth Factor 9® (30%), Super HD® (29%), Hydroxycut Advanced® (29%), Lipo 6® (28%), The Ripper® (27%), Test Booster® (27%), Xenadrine Xtreme Thermogenic® (27%), C4 Extreme® (26%), and C4 Origional® (25%). Products marketed for weight loss, use before/after workout, and prohormones had the highest AE prevalence. DSs can contain substances with independent/additive AEs and/or interact with other ingredients or prescribed medications. Methods described here could provide a continuous surveillance system detecting dangerous DSs entering the market.

Potential biomarkers for clinical outcomes of IVF cycles in women with/without PCOS: Searching with metabolomics

BACKGROUND

Polycystic ovary syndrome (PCOS) is a heterogeneous endocrinological and metabolic disorder which is the common cause of female infertility. The dysmetabolism displayed in it has not been completely ascertained. Metabonomics may shed light on understanding many small molecule endogenous metabolites and their associated metabolic pathways.

OBJECTIVE

To analyze the different metabolites and related metabolic pathways in follicular fluid and embryo culture fluid of PCOS and non-PCOS groups. Finding markers predictable for clinical outcomes of in vitro fertilization-embryo transfer (IVF-ET) treatment.

POPULATION AND SAMPLE

60 women who underwent IVF-ET were selected, including 30 with PCOS and 30 with the fallopian tubal issues only. We collected the first tube follicular fluid (FF) of all patients at the time of oocyte pick up and the waste embryo culture medium (ECM) after D3 high-quality embryo transplant.

METHODS

All samples were performed nontargeted Ultra High Performance Liquid Chromatography-Mass Spectrometry (UHPLC-QE-MS) analysis. Related metabolic pathways were screened by KEGG annotation. To search potential indicators, the logistic regression was made combined with clinical data.

MEAN OUTCOME MEASURES

Predictive performance of markers of clinical outcomes (pregnancy rate, delivery rate, live birth rate, miscarriage rate) of assisted reproductive technology (ART).

RESULTS

Comparing the PCOS group against the non-PCOS group, we found 11 significantly different metabolites in the FF and 56 in the ECM. There are a total of 11 kinds of biomarkers associated with clinical outcomes. Androsterone sulfate, Glycerophosphocholine, and Elaidic carnitine seem robust to predict the abortion rate of the PCOS group, with an AUC of 0.941, 0.933, 0.933, respectively. The glycerol phospholipid metabolic pathway is enriched in both the follicular fluid and embryo culture fluid.

CONCLUSIONS

The differential metabolites were mainly a variety of lipids. Some of them can predict clinical outcomes to a certain extent.

L-carnitine: Searching for New Therapeutic Strategy for Sepsis Management

In this review, we discussed the biological targets of carnitine, its effects on immune function, and how L-carnitine supplementation may help critically ill patients. L-carnitine is a potent antioxidant. L-carnitine depletion has been observed in prolonged intensive care unit (ICU) stays, while L-carnitine supplementation has beneficial effects in health promotion and regulation of immunity. It is essential for the uptake of fatty acids into mitochondria. By inhibiting the ubiquitin-proteasome system, down-regulation of apelin receptor in cardiac tissue, and reducing β-oxidation of fatty acid, carnitine may decrease vasopressor requirement in septic shock and improve clinical outcomes of this group of patients. We also have an overview of animal and clinical studies that have been recruited for evaluating the beneficial effects of L-carnitine in the management of sepsis/ septic shock. Additional clinical data are required to evaluate the optimal daily dose and duration of L-carnitine supplementation.

Neuroprotective Effects of Carnitine and Its Potential Application to Ameliorate Neurotoxicity

Carnitine is an essential metabolite that is absorbed from the diet and synthesized in the kidney, liver, and brain. It ferries fatty acids across the mitochondrial membrane to undergo β-oxidation. Carnitine has been studied as a therapy or protective agent for many neurological diseases and neurotoxicity (e.g., prolonged anesthetic exposure-induced developmental neurotoxicity in preclinical models). Preclinical and clinical data support the notion that carnitine or acetyl carnitine may improve a patient's quality of life through increased mitochondrial respiration, release of neurotransmitters, and global gene expression changes, showing the potential of carnitine beyond its approved use to treat primary and secondary carnitine deficiency. In this review, we summarize the beneficial effects of carnitine or acetyl carnitine on the central nervous system, highlighting protective effects against neurotoxicity-induced damage caused by various chemicals and encouraging a thorough evaluation of carnitine use as a therapy for patients suffering from neurotoxicant exposure.

The bright and the dark sides of L-carnitine supplementation: a systematic review

Background

L-carnitine (LC) is used as a supplement by recreationally-active, competitive and highly trained athletes. This systematic review aims to evaluate the effect of prolonged LC supplementation on metabolism and metabolic modifications.

Methods

A literature search was conducted in the MEDLINE (via PubMed) and Web of Science databases from the inception up February 2020. Eligibility criteria included studies on healthy human subjects, treated for at least 12 weeks with LC administered orally, with no drugs or any other multi-ingredient supplements co-ingestion.

Results

The initial search retrieved 1024 articles, and a total of 11 studies were finally included after applying inclusion and exclusion criteria. All the selected studies were conducted with healthy human subjects, with supplemented dose ranging from 1 g to 4 g per day for either 12 or 24 weeks. LC supplementation, in combination with carbohydrates (CHO) effectively elevated total carnitine content in skeletal muscle. Twenty-four-weeks of LC supplementation did not affect muscle strength in healthy aged women, but significantly increased muscle mass, improved physical effort tolerance and cognitive function in centenarians. LC supplementation was also noted to induce an increase of fasting plasma trimethylamine-N-oxide (TMAO) levels, which was not associated with modification of determined inflammatory nor oxidative stress markers.

Conclusion

Prolonged LC supplementation in specific conditions may affect physical performance. On the other hand, LC supplementation elevates fasting plasma TMAO, compound supposed to be pro-atherogenic. Therefore, additional studies focusing on long-term supplementation and its longitudinal effect on the cardiovascular system are needed.

L-Carnitine's Effect on the Biomarkers of Metabolic Syndrome: A Systematic Review and Meta-Analysis of Randomized Controlled Trials

A systematic review and meta-analysis of randomized controlled trials (RCTs) was carried out to assess L-carnitine supplements’ influence on the biomarkers of metabolic syndrome (MetSyn). PubMed, EMBASE, Cochrane library, and CINAHL were used to collect RCT studies published prior to February 2020. RCT studies were included if they had at least one of the following biomarker outcome measurements: waist circumference (WC), blood pressure (BP), fasting blood sugar (FBS), triglyceride (TG), or high density lipoprotein-cholesterol (HDLc). Nine of twenty studies with adequate methodological quality were included in this meta-analysis. The dose of L-carnitine supplementation administered varied between 0.75 and 3 g/day for durations of 8–24 weeks. L-carnitine supplementation significantly reduced WC and systolic BP (SBP), with no significant effects on FBS, TG, and HDLc. We found that L-carnitine supplementation at a dose of more than 1 g/d significantly reduced FBS and TG and increased HDLc. In conclusion, L-carnitine supplementation is correlated with a significant reduction of WC and BP. A dose of 1–3 g/d could improve the biomarkers of MetSyn by reducing FBS and TG and increasing HDLc.

The Nutraceutical Value of Carnitine and Its Use in Dietary Supplements

Carnitine can be considered a conditionally essential nutrient for its importance in human physiology. This paper provides an updated picture of the main features of carnitine outlining its interest and possible use. Particular attention has been addressed to its beneficial properties, exploiting carnitine's properties and possible use by considering the main in vitro, in animal, and human studies. Moreover, the main aspects of carnitine-based dietary supplements have been indicated and defined with reference to their possible beneficial health properties.

The acute effect of metabolic cofactor supplementation: a potential therapeutic strategy against non-alcoholic fatty liver disease

The prevalence of non-alcoholic fatty liver disease (NAFLD) continues to increase dramatically, and there is no approved medication for its treatment. Recently, we predicted the underlying molecular mechanisms involved in the progression of NAFLD using network analysis and identified metabolic cofactors that might be beneficial as supplements to decrease human liver fat. Here, we first assessed the tolerability of the combined metabolic cofactors including l-serine, N-acetyl-l-cysteine (NAC), nicotinamide riboside (NR), and l-carnitine by performing a 7-day rat toxicology study. Second, we performed a human calibration study by supplementing combined metabolic cofactors and a control study to study the kinetics of these metabolites in the plasma of healthy subjects with and without supplementation. We measured clinical parameters and observed no immediate side effects. Next, we generated plasma metabolomics and inflammatory protein markers data to reveal the acute changes associated with the supplementation of the metabolic cofactors. We also integrated metabolomics data using personalized genome-scale metabolic modeling and observed that such supplementation significantly affects the global human lipid, amino acid, and antioxidant metabolism. Finally, we predicted blood concentrations of these compounds during daily long-term supplementation by generating an ordinary differential equation model and liver concentrations of serine by generating a pharmacokinetic model and finally adjusted the doses of individual metabolic cofactors for future human clinical trials.

The neural stem cell/carnitine malnutrition hypothesis: new prospects for effective reduction of autism risk?

Autism spectrum disorders (ASDs) are developmental neuropsychiatric disorders with heterogeneous etiologies. As the incidence of these disorders is rising, such disorders represent a major human health problem with escalating social cost. Although recent years witnessed advances in our understanding of the genetic basis of some dysmorphic ASDs, little progress has been made in translating the improved understanding into effective strategies for ASD management or minimization of general ASD risk. Here we explore the idea, described in terms of the neural stem cell (NSC)/carnitine malnutrition hypothesis, that an unappreciated risk factor for ASD is diminished capacity for carnitine-dependent long-chain fatty acid β-oxidation in neural stem cells of the developing mammalian brain. The basic premise is that fetal carnitine status is a significant metabolic component in determining NSC vulnerability to derangements in their self-renewal program and, therefore, to fetal ASD risk. As fetal carnitine status exhibits a genetic component that relates to de novo carnitine biosynthesis and is sensitive to environmental and behavioral factors that affect maternal circulating carnitine levels, to which the fetus is exposed, we propose that reduced carnitine availability during gestation is a common risk factor that lurks beneath the genetically complex ASD horizon. One major prediction of the NSC/carnitine malnutrition hypothesis is that a significant component of ASD risk might be effectively managed from a public policy perspective by implementing a carnitine surveillance and dietary supplementation strategy for women planning pregnancies and for women in their first trimester of pregnancy. We argue that this prediction deserves serious clinical interrogation.

The significant role of carnitine and fatty acids during pregnancy, lactation and perinatal period. Nutritional support in specific groups of pregnant women

BACKGROUND & AIMS

Pregnancy is characterized by a complexity of metabolic processes that may impact fetal health and development. Women's nutrition during pregnancy and lactation is considered important for both mother and infant. This review aims to investigate the significant role of fatty acids and carnitine during pregnancy and lactation in specific groups of pregnant and lactating women.

METHODS

The literature was reviewed using relevant data bases (e.g. Pubmed, Scopus, Science Direct) and relevant articles were selected to provide information and data for the text and associated Tables.

RESULTS

Dynamic features especially of plasma carnitine profile during pregnancy and lactation, indicate an extraordinarily active participation of carnitine in the intermediary metabolism both in pregnant woman and in neonate and may also have implications for health and disease later in life. Maternal diets rich in trans and saturated fatty acids can lead to impairments in the metabolism and development of the offspring, whereas the consumption of long chain-polyunsaturated fatty acids during pregnancy plays a beneficial physiologic and metabolic role in the health of offspring.

CONCLUSIONS

Pregnant women who are underweight, overweight or obese, with gestational diabetes mellitus or diabetes mellitus and those who choose vegan/vegetarian diets or are coming from socially disadvantaged areas, should be nutritionally supported to achieve a higher quality diet during pregnancy and/or lactation.

Effect of chronic L-carnitine supplementation on carnitine levels, oxidative stress and apoptotic markers in peripheral organs of adult Wistar rats

This study investigated the effects of L-carnitine supplementation on carnitine levels, oxidative stress and apoptotic markers in the stomach, kidney, liver and testis tissues in adult rats. Rats were randomized to control and L-carnitine supplemented (LCAR) groups. Control group received distilled water for 7 months by intragastric gavage and the LCAR group was given 50 mg/kg/day L-carnitine via intragastric intubation for the same period. L-carnitine concentrations and caspase-3 activity were measured by fluorometric methods while cleaved caspase-3 was determined by Western blot analysis. Bcl-2 associated X protein (Bax) and B-cell lymphoma/leukemia-2 (Bcl-2) were quantified by enzyme immunoassay and Western blot analysis. Oxygen/nitrogen species (ROS/RNS) and total antioxidant capacity (TAC) were analyzed by colorimetric assay. Tissue L-carnitine concentrations were significantly increased in the LCAR group compared to controls. Anti-apoptotic Bcl-2 levels were significantly increased while pro-apoptotic Bax was significantly decreased in LCAR group rats compared to controls. Tissue caspase-3 was significantly alleviated in the LCAR group compared to controls. L-carnitine supplementation increased TAC and decreased ROS/RNS generation in the kidney, liver, stomach and testis tissues compared to controls. Obtained data suggests that L-carnitine supplementation can potentially be used to lessen both oxidative and apoptotic progression in peripheral organs.

The footprints of mitochondrial impairment and cellular energy crisis in the pathogenesis of xenobiotics-induced nephrotoxicity, serum electrolytes imbalance, and Fanconi's syndrome: A comprehensive review

Fanconi's Syndrome (FS) is a disorder characterized by impaired renal proximal tubule function. FS is associated with a vast defect in the renal reabsorption of several chemicals. Inherited and/or acquired conditions seem to be connected with FS. Several xenobiotics including many pharmaceuticals are capable of inducing FS and nephrotoxicity. Although the pathological state of FS is well described, the exact underlying etiology and cellular mechanism(s) of xenobiotics-induced nephrotoxicity, serum electrolytes imbalance, and FS are not elucidated. Constant and high dependence of the renal reabsorption process to energy (ATP) makes mitochondrial dysfunction as a pivotal mechanism which could be involved in the pathogenesis of FS. The current review focuses on the footprints of mitochondrial impairment in the etiology of xenobiotics-induced FS. Moreover, the importance of mitochondria protecting agents and their preventive/therapeutic capability against FS is highlighted. The information collected in this review may provide significant clues to new therapeutic interventions aimed at minimizing xenobiotics-induced renal injury, serum electrolytes imbalance, and FS.

l-carnitine and fat type in the maternal diet during gestation and lactation modify the fatty acid composition and expression of lipid metabolism-related genes in piglets

This study examined the influence of adding different amounts of maternal dietary l-carnitine and two fat types on fatty acid (FA) composition and the expression of lipid metabolism-related genes in piglets. The experiment was designed as a 2 × 2 factorial with two fat types (3.5% soyabean oil, SO, and 3.5% fish oil, FO) and two levels of l-carnitine (0 and 100 mg/kg) added to the sows' diets. A higher proportion of n-3 polyunsaturated fatty acids (PUFA) and a lower ratio of n-6/n-3 PUFA in sow milk and piglet tissues were observed in the FO groups than in the SO groups. Adding l-carnitine increased the proportion of C16:1 in sow milk and decreased n-3 PUFA in piglet subcutaneous fat. Hepatic peroxisome proliferator-activated receptor α (PPAR-α) was more abundantly expressed in piglets from the FO groups than from the SO groups (p < 0.05), whereas stearoyl-CoA-desaturase (SCD), sterol regulatory element binding protein-1 (SREBP1) and ∆6-desaturase (D6D) genes were less expressed in the FO groups compared with piglets from the SO groups. The expression of fatty acid synthase (FAS) genes was decreased in the SO groups with l-carnitine compared to that of the other dietary treatments. No differences among dietary treatments were observed with regard to the expression of acetyl-CoA carboxylase (ACC). In conclusion, FO and l-carnitine supplementation in sows affect FA composition and hepatic gene expression in piglets.

Mechanism of valproic acid-induced Fanconi syndrome involves mitochondrial dysfunction and oxidative stress in rat kidney

AIM

Drug-induced kidney proximal tubular injury and renal failure (Fanconi syndrome; FS) is a clinical complication. Valproic acid (VPA) is among the FS-inducing drugs. The current investigation was designed to evaluate the role of mitochondrial dysfunction and oxidative stress in VPA-induced renal injury.

METHODS

Animals received VPA (250 and 500 mg/kg, i.p., 15 consecutive days). Serum biomarkers of kidney injury and markers of oxidative stress were assessed. Moreover, kidney mitochondria were isolated and mitochondrial indices, including succinate dehydrogenase activity (SDA), mitochondrial depolarization, mitochondrial permeability transition pore (MPP), reactive oxygen species (ROS), lipid peroxidation (LPO), mitochondrial glutathione, and ATP were determined.

RESULTS

Valproic acid-treated animals developed biochemical evidence of FS as judged by elevated serum gamma-glutamyl transferase (γ-GT), alkaline phosphatase (ALP), creatinine (Cr), and blood urea nitrogen (BUN) along with hypokalaemia, hypophosphataemia, and a decrease in serum uric acid. VPA caused an increase in kidney ROS and LPO. Renal GSH reservoirs were depleted and tissue antioxidant capacity decreased in VPA-treated animals. Renal tubular interstitial nephritis, tissue necrosis, and atrophy were also evident in VPA-treated rats. Mitochondrial parameters including SDA, MMP, GSH, ATP and MPP were decreased and mitochondrial ROS and LPO were increased with VPA treatment. It was found that carnitine (100 mg/kg, i.p.) mitigated VPA adverse effects towards the kidney.

CONCLUSIONS

These data suggest that mitochondrial dysfunction and oxidative stress contributed to the VPA-induced FS. On the other hand, carnitine could be considered a potentially safe and effective therapeutic option in attenuating VPA-induced renal injury.

Physiology of L-carnitine in plants in light of the knowledge in animals and microorganisms

L-carnitine is present in all living kingdoms where it acts in diverse physiological processes. It is involved in lipid metabolism in animals and yeasts, notably as an essential cofactor of fatty acid intracellular trafficking. Its physiological significance is poorly understood in plants, but L-carnitine may be linked to fatty acid metabolism among other roles. Indeed, carnitine transferases activities and acylcarnitines are measured in plant tissues. Current knowledge of fatty acid trafficking in plants rules out acylcarnitines as intermediates of the peroxisomal and mitochondrial fatty acid metabolism, unlike in animals and yeasts. Instead, acylcarnitines could be involved in plastidial exportation of de novo fatty acid, or importation of fatty acids into the ER, for synthesis of specific glycerolipids. L-carnitine also contributes to cellular maintenance though antioxidant and osmolyte properties in animals and microbes. Recent data indicate similar features in plants, together with modulation of signaling pathways. The biosynthesis of L-carnitine in the plant cell shares similar precursors as in the animal and yeast cells. The elucidation of the biosynthesis pathway of L-carnitine, and the identification of the enzymes involved, is today essential to progress further in the comprehension of its biological significance in plants.

The effect of L-carnitine supplementation on serum leptin concentrations: a systematic review and meta-analysis of randomized controlled trials

PURPOSE

The actual effects of L-carnitine administration on leptin serum level is inconsistent. In order to assess the efficacy of L-carnitine supplementation on serum leptin we conducted a meta-analysis of randomized controlled trials (RCTs).

METHODS

Seven studies with 325 cases and 330 controls were included. The pooled weighted mean difference (WMD) was calculated by random-effects model. The heterogeneity across studies was evaluated by using Cochrane's Q and I2 tests. In addition, we carried out the metaninf command to test the effect of each individual study on the overall result.

RESULTS

L-carnitine supplementation seemed to have no significant effect on serum leptin concentrations (WMD: -0.565 ng/mL; 95% CI: -2.417 to 1.287, p = 0.550). However, between-study heterogeneity was higher across all studies (I2 = 84.3%, p < 0.0001). Subgroup analysis to find the sources of heterogeneity showed that L-carnitine dosage (g) ( < 2 g: I2 = 00.0%, p = 0.408), and study population (diabetes: I2 = 46.7%, p = 0.153, and non-diabetes: I2 = 15.1%, p = 0.317) were the potential sources of heterogeneity. Besides, a more significant reduction in serum leptin concentration was observed with a daily dose of ≥ 2 mg L-carnitine (WMD: -2.742 ng/mL; 95% CI: -3.039 to -2.444, p < 0.001), in diabetic patients (WMD: -2.946 ng/mL; 95% CI: -3.254 to -2.638, p < 0.001), and with intervention duration <12 weeks (WMD: -2.772 ng/mL; 95% CI: -3.073 to -2.471, p < 0.001).

CONCLUSION

L-carnitine consumption does not reduce serum leptin significantly. However, a significant effect on leptin was observed in diabetic patients and patients who received doses more than 3 mg per day in the course of <12 weeks.

Oral carnitine supplementation reduces body weight and insulin resistance in women with polycystic ovary syndrome: a randomized, double-blind, placebo-controlled trial

OBJECTIVE

Limited data are available for evaluating the effects of oral carnitine supplementation on weight loss and metabolic profiles of women with polycystic ovary syndrome (PCOS). This study was designed to determine the effects of oral carnitine supplementation on weight loss, and glycaemic and lipid profiles in women with PCOS.

DESIGN, PATIENTS AND MEASUREMENTS

In a prospective, randomized, double-blind, placebo-controlled trial, 60 overweight patients diagnosed with PCOS were randomized to receive either 250 mg carnitine supplements (n = 30) or placebo (n = 30) for 12 weeks. Fasting blood samples were obtained at the beginning and the end of the study to quantify parameters of glucose homoeostasis and lipid concentrations.

RESULTS

At the end of the 12 weeks, taking carnitine supplements resulted in a significant reduction in weight (-2·7 ± 1·5 vs +0·1 ± 1·8 kg, P < 0·001), BMI (-1·1 ± 0·6 vs +0·1 ± 0·7 kg/m(2) , P < 0·001), waist circumference (WC) (-2·0 ± 1·3 vs -0·3 ± 2·0 cm, P < 0·001) and hip circumference (HC) (-2·5 ± 1·5 vs -0·3 ± 1·8 cm, P < 0·001) compared with placebo. In addition, compared with placebo, carnitine administration in women with PCOS led to a significant reduction in fasting plasma glucose (-0·38 ± 0·36 vs +0·11 ± 0·97 mmol/l, P = 0·01), serum insulin levels (-14·39 ± 25·80 vs +3·01 ± 37·25 pmol/l, P = 0·04), homoeostasis model of assessment-insulin resistance (-0·61 ± 1·03 vs +0·11 ± 1·43, P = 0·04) and dehydroepiandrosterone sulphate (-3·64 ± 7·00 vs -0·59 ± 3·20 μmol/l, P = 0·03).

CONCLUSIONS

Overall, 12 weeks of carnitine administration in PCOS women resulted in reductions in weight, BMI, WC and HC, and beneficial effects on glycaemic control; however, it did not affect lipid profiles or free testosterone.

Effects of amino acid derivatives on physical, mental, and physiological activities

Nutritional ergogenic aids have been in use for a long time to enhance exercise and sports performance. Dietary components that exhibit ergogenic activity are numerous and their consumption is common and popular among athletes. They often come under scrutiny by legal authorities for their claimed benefits and safety concerns. Amino acid derivatives are propagated as being effective aids to enhance physical and mental performance in many ways, even though studies have pointed out that individuals who are deficient are more likely to benefit from dietary supplementation of amino acid derivatives than normal humans. In this review, some of the most common and widely used amino acids derivatives in sports and athletics namely creatine, tyrosine, carnitine, HMB, and taurine have been discussed for their effects on exercise performance, mental activity as well as body strength and composition. Creatine, carnitine, HMB, and taurine are reported to delay the onset of fatigue, improve exercise performance, and body strength. HMB helps in increasing fat-free mass and reduce exercise induced muscle injury. Taurine has been found to reduce oxidative stress during exercise and also act as an antihypertensive agent. Although, studies have not been able to find any favorable effect of tyrosine administration on exercise performance, it has been proved to be very effective in fighting stress, improving mood and cognitive performance particularly in sleep-deprived subjects. While available data from published studies and findings are equivocal about the efficacy of creatine, tyrosine, and HMB, more comprehensive researches on carnitine and taurine are necessary to provide evidence for the theoretical basis of their ergogenic role in nutritional modification and supplementation.

L-Carnitine intake prevents irregular feeding-induced obesity and lipid metabolism disorder

L-Carnitine supplementation has been used to reduce obesity caused by high-fat diet, which is beneficial for lowering blood and hepatic lipid levels, and for ameliorating fatty liver. However, whether l-carnitine may affect irregular feeding-induced obesity and lipid metabolism disorder is still largely unknown. In the present study, we developed a time-delayed pattern of eating, and investigated the effects of l-carnitine on the irregular eating induced adiposity in mice. After an experimental period of 8 weeks with l-carnitine supplementation, l-carnitine significantly inhibited body weight increase and epididymal fat weight gain induced by the time-delayed feeding. In addition, l-carnitine administration decreased levels of serum alanine aminotransferase (GPT), glutamic oxalacetic transaminase (GOT) and triglyceride (TG), which were significantly elevated by the irregular feeding. Moreover, mice supplemented with l-carnitine did not display glucose intolerance-associated hallmarks, which were found in the irregular feeding-induced obesity. Furthermore, quantitative real-time polymerase chain reaction (qRT-PCR) analysis indicated that l-carnitine counteracted the negative alterations of lipid metabolic gene expression (fatty acid synthase, 3-hydroxy-3-methyl-glutaryl coenzyme A reductase, cholesterol 7α-hydroxylase, carnitine/acylcarnitine translocase) in the liver and fat of mice caused by the irregular feeding. Therefore, our results suggest that the time-delayed pattern of eating can induce adiposity and lipid metabolic disorders, while l-carnitine supplementation might prevent these negative symptoms.

Carnitine therapy for the treatment of metabolic syndrome and cardiovascular disease: evidence and controversies

As the incidence of metabolic syndrome increases, there is also a growing interest in finding safe and inexpensive treatments to help lower associated risk factors. L-carntine, a natural dietary supplement with the potential to ameliorate atherosclerosis, has been the subject of recent investigation and controversy. A majority of studies have shown benefit of L-C supplementation in the metabolic syndrome or cardiovascular risk factors. However, recent work has suggested that dietary L-C may accelerate atherosclerosis via gut microbiota metabolites, complicating the role of L-C supplementation in health.

Carnitine Profile and Effect of Suppletion in Children with Renal Fanconi Syndrome due to Cystinosis

BACKGROUND

Cystinosis is an autosomal recessive disorder marked by intralysosomal cystine accumulation. Patients present with generalized proximal tubular dysfunction called renal Fanconi syndrome. Urinary carnitine loss results in plasma and muscle carnitine deficiency, but no clinical signs of carnitine deficiency have been described. Also, the optimal dose of carnitine supplementation is undefined. This study aimed to determine whether currently recommended carnitine doses result in adequate correction of plasma carnitine.

METHODS

Five cystinosis patients with renal Fanconi syndrome, aged 2-18 years, were included. L-carnitine was prescribed 50 mg/kg/day since diagnosis: median 36 (range 18-207) months. Total and free plasma and urine carnitine and carnitine profiles were measured at study onset, after stopping L-carnitine for 3 months and 3 months after reintroducing L-carnitine 50 mg/kg/day.

RESULTS

At study onset, plasma free carnitine was normal in all patients, total carnitine (1/5), acetylcarnitine (3/5), and several short- and medium-chain acylcarnitines ≤10 carbons (5/5) were increased indicating carnitine over-supplementation. Three months after cessation, carnitine profiles normalized and 3/5 patients showed plasma carnitine deficiency. Three months after reintroduction, plasma free carnitine normalized in all patients, however, carnitine profiles were disturbed in 4/5 patients. Urine free carnitine, acetylcarnitine, and acylcarnitines ≤10 carbons were increased in all patients independent of carnitine supplementation.

CONCLUSION

Administration of recommended doses L-carnitine (50 mg/kg/day) resulted in over-supplementation. Although the drug is considered to be rather safe, long-term effects of over-supplementation remain unknown warranting cautious use of high doses. Plasma carnitine profile might be used as a monitor, to prevent overdosing.

Nutrition as medical therapy

Recent data support the use of nutritional agents for use as targeted medical therapy. This article reviews some of the pharmacologic roles that parenteral nutritional ingredients (selenium, lipid emulsion, insulin, and levocarnitine) can play in the setting of critical illness.

Effect of lysine, vitamin B(6), and carnitine supplementation on the lipid profile of male patients with hypertriglyceridemia: a 12-week, open-label, randomized, placebo-controlled trial

BACKGROUND

Fat metabolism is known to be altered in hypertriglyceridemia. Fat oxidation requires carnitine, which can be obtained either from the diet (animal or dairy products) or through synthesis in the body using both lysine and vitamin B(6).

OBJECTIVE

The goal of this study was to investigate the effect of lysine, vitamin B(6), and carnitine supplementation on both glycemia and the lipid profiles, specifically triglyceride (TG) levels, in men with hypertriglyceridemia.

METHODS

This 12-week, randomized, placebo-controlled clinical trial was conducted at a Lebanese medical center. A total of 85 hypertriglyceridemic (TG> 150 mg/dL) male patients were randomized to 1 of 5 groups and given supplements of lysine (1 g/d), vitamin B(6) (50 mg/d), lysine (1 g/d) + vitamin B(6) (50 mg/d), carnitine (1 g/d), or placebo for 12 weeks. The lipid profile (TG, total cholesterol, LDL-C, and HDL-C) and fasting plasma glucose levels were assessed at baseline and at 6 and 12 weeks.

RESULTS

Adults (∼50 years) Lebanese males from a low socioeconomic status in Beirut were given the appropriate supplements. Vitamin B(6) supplementation was associated with a significant reduction in total cholesterol and HDL-C of ∼10%. In addition, plasma TG was reduced by 36.6 mg/dL at 6 weeks, whereas levels in the placebo group increased by 18 mg/dL; this difference failed to reach statistical significance. No major changes in the lipid profile were observed in the lysine and carnitine groups or when lysine was added to vitamin B(6).

CONCLUSION

Vitamin B(6) supplementation in these male patients with hypertriglyceridemia reduced plasma total cholesterol and HDL-C concentrations.

The effect of nitric-oxide-related supplements on human performance

Nitric oxide (NO) has led a revolution in physiology and pharmacology research during the last two decades. This labile molecule plays an important role in many functions in the body regulating vasodilatation, blood flow, mitochondrial respiration and platelet function. Currently, it is known that NO synthesis occurs via at least two physiological pathways: NO synthase (NOS) dependent and NOS independent. In the former, L-arginine is the main precursor. It is widely recognized that this amino acid is oxidized to NO by the action of the NOS enzymes. Additionally, L-citrulline has been indicated to be a secondary NO donor in the NOS-dependent pathway, since it can be converted to L-arginine. Nitrate and nitrite are the main substrates to produce NO via the NOS-independent pathway. These anions can be reduced in vivo to NO and other bioactive nitrogen oxides. Other molecules, such as the dietary supplement glycine propionyl-L-carnitine (GPLC), have also been suggested to increase levels of NO, although the physiological mechanisms remain to be elucidated. The interest in all these molecules has increased in many fields of research. In relation with exercise physiology, it has been suggested that an increase in NO production may enhance oxygen and nutrient delivery to active muscles, thus improving tolerance to physical exercise and recovery mechanisms. Several studies using NO donors have assessed this hypothesis in a healthy, trained population. However, the conclusions from these studies showed several discrepancies. While some reported that dietary supplementation with NO donors induced benefits in exercise performance, others did not find any positive effect. In this regard, training status of the subjects seems to be an important factor linked to the ergogenic effect of NO supplementation. Studies involving untrained or moderately trained healthy subjects showed that NO donors could improve tolerance to aerobic and anaerobic exercise. However, when highly trained subjects were supplemented, no positive effect on performance was indicated. In addition, all this evidence is mainly based on a young male population. Further research in elderly and female subjects is needed to determine whether NO supplements can induce benefit in exercise capacity when the NO metabolism is impaired by age and/or estrogen status.

Highest Observed Intake: definition, regulatory uses and provisional values

For nutrients and related substances, the Tolerable Upper Intake Level (UL) has become the internationally accepted risk assessment method. The major limitation of the UL method as applied by authoritative groups thus far is that no UL has been set for nutrients without established adverse effects. In contrast to the limitations inherent in the UL method, an alternative approach is available; it identifies a risk assessment value termed the Highest Observed Intake (HOI). In the absence of a UL, the HOI is the highest intake with adequate data to show, with acceptable confidence, the absence of adverse effects up to that intake. With this concept defined and accepted in a report by the authoritative international organizations FAO and WHO, a complete risk assessment for the nutrients and related substances would have to identify UL values for those with known adverse effects and HOI values for those without known adverse effects. The need for the HOI concept and value is illustrated by the unjustified policy and regulatory actions taken in relation to vitamin B12. Regulatory utility is explained and tentative HOI values are identified for several vitamins and non-essential nutrients. Endorsement of the concept and development of HOI values by authoritative bodies is likely to be required for broad acceptance and use.

Behavior of acetyl-L-carnitine injections (Nicetile fiale) with different drugs used for combined therapy

INTRODUCTION

Acetyl-L-carnitine (Nicetile fiale; Biofutura Pharma S.p.A., Sigma Tau group, Milano, Italy) is a compound widely used for the treatment of many diseases, such as neuropathies, diabetic polyneuropathy, and Parkinson's disease. It is frequently administered via the intramuscular route with other drugs, such as steroidal anti.inflammatories, muscle relaxants, and vitamins.

METHODS

In the present study the behavior of acetyl-L-carnitine injections (Nicetile fiale) with different drugs used for combined therapy was studied. Physicochemical properties including color, clarity, pH, and drug content were observed before and after mixing at room temperature.

RESULTS

The content of all the active drugs after mixing remained optimal within 10% of their nominal values.

CONCLUSIONS

The measurements demonstrate the physicochemical compatibility between Nicetile fiale and the other tested products, meaning that there is no evidence of interactions and degradation.

Chiral toxicology: it's the same thing...only different

Chiral substances possess a unique architecture such that, despite sharing identical molecular formulas, atom-to-atom linkages, and bonding distances, they cannot be superimposed. Thus, in the environment of living systems, where specific structure-activity relationships may be required for effect (e.g., enzymes, receptors, transporters, and DNA), the physiochemical and biochemical properties of racemic mixtures and individual stereoisomers can differ significantly. In drug development, enantiomeric selection to maximize clinical effects or mitigate drug toxicity has yielded both success and failure. Further complicating genetic polymorphisms in drug disposition, stereoselective metabolism of chiral compounds can additionally influence pharmacokinetics, pharmacodynamics, and toxicity. Optically pure pharmaceuticals may undergo racemization in vivo, negating single enantiomer benefits or inducing unexpected effects. Appropriate chiral antidotes must be selected for therapeutic benefit and to minimize adverse events. Enantiomers may possess different carcinogenicity and teratogenicity. Environmental toxicology provides several examples in which compound bioaccumulation, persistence, and toxicity show chiral dependence. In forensic toxicology, chiral analysis has been applied to illicit drug preparations and biological specimens, with the potential to assist in determination of cause of death and aid in the correct interpretation of substance abuse and "doping" screens. Adrenergic agonists and antagonist, nonsteroidal anti-inflammatory agents, SSRIs, opioids, warfarin, valproate, thalidomide, retinoic acid, N-acetylcysteine, carnitine, penicillamine, leucovorin, glucarpidase, pesticides, polychlorinated biphenyls, phenylethylamines, and additional compounds will be discussed to illustrate important concepts in "chiral toxicology."

L-carnitine: implications in the treatment of the metabolic syndrome and Type 2 diabetes

The metabolic syndrome (MS) is a conglomeration of inter-related common clinical disorders, including obesity, glucose intolerance, hypertension and dyslipidemia, which predispose to Type 2 diabetes (T2D) and cardiovascular diseases. Hyperinsulinemia, per se, and insulin resistance are the pathogenic factors associated with the metabolic risk factors. Since these risk factors are the most frequent causes for mortality among patients with T2D and the MS, treatments targeting normalization of both lipid and glucose homeostasis are of interest. The crucial role of L-carnitine (CA) as a regulator of lipid and glucose metabolism has raised considerable interest in its use as a potential tool for therapeutic intervention in the MS. Several clinical studies have, therefore, been undertaken to examine the efficacy and other benefits in the treatment of T2D and the MS. Studies from rodent models of MS have also shown the positive effects of CA on several components of the syndrome. CA, being an endogenous water-soluble nutrient, could be a safe adjunct and a relevant future drug for the MS. This review provides an overview on the importance of CA in T2D and the MS and the need for further evaluation of its inclusion in treatment protocols.

Expanded approach to tolerable upper intake guidelines for nutrients and bioactive substances

The original tolerable upper intake level (UL) method greatly improved the application of risk assessment to the evaluation of nutrient safety for humans, but a UL is only set where the data establish a hazard resulting from high intakes. Absence of a UL for those nutrients with no established hazard has been misinterpreted by regulators and resulted in overly restrictive policies. To prevent such misinterpretation, the observed safe level (OSL) was developed and defined as "the highest intake with convincing evidence of safety, even if there are no established adverse effects at any level." More recently, a FAO/WHO report gave a similar definition for the highest observed intake (HOI). Another disadvantage of the UL method is the application of arbitrary uncertainty factors (UF). An alternative to the traditional adjustment for uncertainty involves arranging the data in decreasing order of daily intake, followed by evaluation of each trial for quantity and quality of data. Studies are selected downward until no adverse effects are observed in a trial of sufficient quality to justify no further correction for uncertainty (i.e. selection of data that qualify for UF = 1). Thus, the no observed adverse effect level or OSL selected requires no further adjustment for uncertainty. For supplemental intakes of some vitamins, many bioactive substances, and most amino acids, no adverse effects that are clearly related to high intakes have been established, but where the dataset is sufficiently robust, application of the OSL-HOI technique can provide risk assessment values.

Risk assessment for the amino acids taurine, L-glutamine and L-arginine

Taurine, glutamine and arginine are examples of amino acids which have become increasingly popular as ingredients in dietary supplements and functional foods and beverages. Animal and human clinical research suggests that oral supplementation of these amino acids provides additional health and/or performance benefits beyond those observed from normal intake of dietary protein. The increased consumer awareness and use of these amino acids as ingredients in dietary supplements and functional foods warrant a comprehensive review of their safety through quantitative risk assessment, and identification of a potential safe upper level of intake. The absence of a systematic pattern of adverse effects in humans in response to orally administered taurine (Tau), l-glutamine (Gln) and l-arginine (Arg) precluded the selection of a no observed adverse effect level (NOAEL) or lowest observed adverse effect level (LOAEL). Therefore, by definition, the usual approach to risk assessment for identification of a tolerable upper level of intake (UL) could not be used. Instead, the newer method described as the Observed Safe Level (OSL) or Highest Observed Intake (HOI) was utilized. The OSL risk assessments indicate that based on the available published human clinical trial data, the evidence for the absence of adverse effects is strong for Tau at supplemental intakes up to 3 g/d, Gln at intakes up to 14 g/d and Arg at intakes up to 20 g/d, and these levels are identified as the respective OSLs for normal healthy adults. Although much higher levels of each of these amino acids have been tested without adverse effects and may be safe, the data for intakes above these levels are not sufficient for a confident conclusion of long-term safety, and therefore these values are not selected as the OSLs.