L-Carnitine augments probenecid anti-inflammatory effect in monoiodoacetate-induced knee osteoarthritis in rats: involvement of miRNA-373/P2X7/NLRP3/NF-κB milieu

Osteoarthritis (OA) is a degenerative joint disease, whereas the underlying molecular trails involved in its pathogenesis are not fully elucidated. Hence, the current study aimed to investigate the role of miRNA-373/P2X7/NLRP3/NF-κB trajectory in its pathogenesis as well as the possible anti-inflammatory effects of probenecid and l-carnitine in ameliorating osteoarthritis via modulating this pathway. In the current study, male Sprague Dawley rats were used and monoiodoacetate (MIA)-induced knee osteoarthritis model was adopted. Probenecid and/or L-carnitine treatments for 14 days succeeded in reducing OA knee size and reestablishing motor coordination and joint mobility assessed by rotarod testing. Moreover, different treatments suppressed the elevated serum levels of IL-1β, IL-18, IL-6, and TNF-α via tackling the miRNA-373/P2X7/NLRP3/NF-κB, witnessed as reductions in protein expressions of P2X7, NLRP3, cleaved caspase-1 and NF-κB. These were accompanied by increases in procaspase-1 and IκB protein expression and in miRNA-373 gene expression OA knee to various extents. In addition, different regimens reversed the abnormalities observed in the H and E as well as Safranin O-Fast green OA knees stained sections. Probenecid or l-carnitine solely showed comparable results on the aforementioned parameters, whereas the combination therapy had the most prominent effect on ameliorating the aforementioned parameters. In conclusion, l-carnitine augmented the probenecid's anti-inflammatory effect to attenuate MIA-induced osteoarthritis in rats by provoking the miRNA-373 level and inhibiting the P2X7/NLRP3/NF-κB milieu, leading to the suppression of serum inflammatory cytokines: IL-1β, IL-18, IL-6, and TNF-α. These findings suggest the possibility of using probenecid and l-carnitine as a useful therapeutic option for treatment of osteoarthritis.

The effect of adding L-Carnitine to the GnRH-antagonist protocol on assisted reproductive technology outcome in women with polycystic ovarian syndrome: a randomized clinical trial

OBJECTIVE

This study aimed to investigate the effect of adding L-Carnitine to the gonadotropins on ART outcome in frozen-thawed embryo transfer cycles among PCOS women.

METHODS

In this randomized clinical trial, 83 patients with PCOS were randomized to either L-Carnitine supplemented (n = 42) or control (n = 41) groups. The L-Carnitine group was given 3000 mg of oral L-Carnitine daily until the final day of ovulation. The numbers of metaphase II (MII) oocytes, 2-pronuclears (2PNs), oocyte maturity rate, fertilization rate, fertilization proportion as well as implantation, chemical and clinical pregnancy rates were compared between the two groups.

RESULTS

Even though the duration of stimulation and endometrial thickness were comparable between groups (p > .05), serum estradiol level on the day of oocyte triggering, was significantly higher in the L-Carnitine group compared to the control group (p < .05). In contrast, the number of retrieved and MII oocytes as well as the number of 2PNs and obtained embryos were similar between groups (p > .05). Moreover, oocyte maturity rate (0.85 ± 0.38 vs. 1.02 ± 0.90), fertilization proportion (0.62 ± 0.44 vs. 0.80 ± 0.86), fertilization rate (0.70 ± 0.22 vs. 0.76 ± 0.19) along with implantation rate (18.1 vs. 13.7%), chemical (26.8 vs. 30.7%) and clinical (24.3 vs. 25.6%) pregnancy rates, were all comparable between L-Carnitine and control groups respectively (p > .05).

CONCLUSIONS

Our result showed that oral L-Carnitine administration during induction of ovulation among PCOS women could not improve laboratory and pregnancy outcome.

Incorporation of L-Carnitine in the OvSynch protocol enhances the morphometrical and hemodynamic parameters of the ovarian structures and uterus in ewes under summer climatic conditions

Heat stress negatively impacts the reproductive performance of sheep including the efficiency of estrous synchronization regimens. This study aimed to investigate the potential effects of L-Carnitine (LC) administration on the efficacy of the OvSynch protocol in ewes under summer climatic conditions. Ewes were synchronized for estrus using the OvSynch protocol and a dose of LC (20 mg/kg body weight) was intravenously (IV) administered on the same day of PGF2α injection to one group (n = 8; LC group), while other ewes (n = 8; control group) received the same protocol without LC. Ultrasonographic evaluation (including B-mode, color, and pulsed Doppler) was used to assess the morphometrical and hemodynamic parameters of ovarian structures [number, size, and blood flow of follicles (GFs) and corpora lutea (CLs)] and uterus during the estrous phase (Day 0), and on Day 8 post ovulation (luteal phase). Uterine artery blood flow (MUA) was assessed by measuring the resistive index (RI) and pulsatility index (PI) at both stages. The serum samples were collected to measure the concentrations of estradiol (E2), progesterone (P4), and total antioxidant capacity (TAC) using commercial kits. Results revealed a significant (P<0.05) increase in the colored pixel area of GFs and uterus in the LC group (392.84 ± 31.86 and 712.50 ± 46.88, respectively) compared to the control one (226.25 ± 17.74 and 322 ± 18.78, respectively) during Day 0. Circulating E2 and TAC levels were significantly (P<0.05) higher in the LC-treated ewes (31.45 ± 1.53 pg/ml and 1.80 ± 0.13 mM/L, respectively) compared to those in the control ewes (21.20 ± 1.30 pg/ml and 0.98 ± 0.09 mM/L, respectively) during Day 0. Moreover, LC improved the colored pixel area of CLs (2038.14 ± 102.94 versus 1098 ± 82.39) and uterus (256.38 ± 39.28 versus 121.75 ± 11.36) and circulating P4 (2.99 ± 0.26 ng/ml versus1.67 ± 0.15 ng/ml) on Day 8. Values of RI of MUA were significantly lower in the LC group compared to the control one on Day 0 and Day 8 (0.48 ± 0.03 versus 0.72 ± 0.03 and 0.58 ± 0.03 versus 0.78 ± 0.02, respectively). In conclusion, LC incorporation in the OvSynch protocol enhanced the morphometrical and hemodynamic parameters of the ovarian structures and the uterus concomitantly with improvements in the TAC, E2, and P4 concentrations in ewes under hot summer conditions.

L-Carnitine improves mechanical responses of cardiomyocytes and restores Ca2+ homeostasis during aging

L-Carnitine (β-hydroxy-γ-trimethylaminobutyric acid, LC) is a crucial molecule for the mitochondrial oxidation of fatty acids. It facilitates the transport of long-chain fatty acids into the mitochondrial matrix. The reduction in LC levels during the aging process has been linked to numerous cardiovascular disorders, including contractility dysfunction, and disrupted intracellular Ca2+ homeostasis. The aim of this study was to examine the effects of long-term (7 months) LC administration on cardiomyocyte contraction and intracellular Ca2+ transients ([Ca2+]i) in aging rats. Male albino Wistar rats were randomly assigned to either the control or LC-treated groups. LC (50 mg/kg body weight/day) was dissolved in distilled water and orally administered for a period of 7 months. The control group received distilled water alone. Subsequently, ventricular single cardiomyocytes were isolated, and the contractility and Ca2+ transients were recorded in aging (18 months) rats. This study demonstrates, for the first time, a novel inotropic effect of long-term LC treatment on rat ventricular cardiomyocyte contraction. LC increased cardiomyocyte cell shortening and resting sarcomere length. Furthermore, LC supplementation led to a reduction in resting [Ca2+]i level and an increase in the amplitude of [Ca2+]i transients, indicative of enhanced contraction. Consistent with these results, decay time of Ca2+ transients also decreased significantly in the LC-treated group. The long-term administration of LC may help restore the Ca2+ homeostasis altered during aging and could be used as a cardioprotective medication in cases where myocyte contractility is diminished.

L-Carnitine and Male Fertility: Is Supplementation Beneficial?

L-Carnitine, a natural antioxidant found in mammals, plays a crucial role in the transport of long-chain fatty acids across the inner mitochondrial membrane. It is used as a nutritional supplement by professional athletes, improving performance and post-exercise recovery. Additionally, its therapeutic applications, including those in male infertility, have been investigated, as it may act as a defense mechanism against the excessive production of reactive oxygen species (ROS) in the testis, a process that can lead to sperm damage. This effect is achieved by enhancing the expression and activity of enzymes with antioxidant properties. Nevertheless, the mechanisms underlying the benefits of L-Carnitine remain unknown. This review aims to consolidate the current knowledge about the potential benefits of L-Carnitine and its role in male (in)fertility. Considering in vitro studies with Sertoli cells, pre-clinical studies, and investigations involving infertile men, a comprehensive understanding of the effects of L-Carnitine has been established. In vitro studies suggest that L-Carnitine has a direct influence on somatic Sertoli cells, improving the development of germ cells. Overall, evidence supports that L-Carnitine can positively impact male fertility, even at a relatively low dose of 2 g/day. This supplementation enhances sperm parameters, regulates hormone levels, reduces ROS levels, and subsequently improves fertility rates. However, further research is needed to elucidate the underlying mechanisms and establish optimal doses. In conclusion, the role of L-Carnitine in the field of male reproductive health is highlighted, with the potential to improve sperm quality and fertility.

The effect of L-carnitine supplementation on lipid profile in adults: an umbrella meta-analysis on interventional meta-analyses

Introduction

Previous meta-analyses investigating the therapeutic effects of L-carnitine on lipid profiles have demonstrated inconsistent results. The present umbrella meta-analysis aimed to investigate the impact of efficacy of L-carnitine on lipid profiles in adults.

Methods

Databases including PubMed, Scopus, and Embase, Web of Science, and Google Scholar were searched up to June 2023. Meta-analysis was performed using a random-effects model.

Results

Our results from thirteen meta-analyses indicated that L-carnitine supplementation significantly total cholesterol (TC) (ES = -1.05 mg/dL, 95% CI: -1.71, -0.39; p = 0.002), triglycerides (TG) (ES = -2.51 mg/dL; 95% CI: -3.62, -1.39, p < 0.001), and low-density lipoprotein-cholesterol (LDL-C) (ES = -4.81 mg/dL; 95% CI: -6.04, -3.59; p < 0.001). It also increased high-density lipoprotein-cholesterol (HDL-C) (ES: 0.66 mg/dL, 95% CI: 0.20, 1.12, p = 0.005) levels.

Conclusion

The present umbrella meta-analysis suggests supplementation with L-carnitine in a dosage of more than 2 g/day can improve lipid profile. Thus, L-carnitine supplementation can be recommended as an adjuvant anti-hyperlipidemic agent.

Conjugated linoleic acid and L-carnitine combination effects on obesity-related miRNAs in diet-induced obese rats

OBJECTIVES

Obesity is a major global health issue, resulting in significant costs and increased mortality rates. Finding effective treatments for obesity is therefore essential. This study investigated the combined effects of L-Carnitine (LC) and Conjugated Linoleic Acid (CLA) on weight loss and adipose tissue microRNA levels.

SUBJECTS /METHODS

Forty male Wistar rats weighing 150-200 g and about 8 weeks old were fed either a normal fat diet (NFD) or a high-fat diet (HFD) for 8 weeks. Afterwards, the HFD group was randomly divided into four subgroups: control, LC (200 mg kg-1), CLA (500 mg kg-1), and both (n = 8 in each group). The study lasted for an additional 4 weeks. The animals' weights were recorded regularly, and after 12 weeks, miRNAs were extracted from epididymal adipose tissue and analysed using real-time PCR. The miRNA expression levels of miR-27a and miR-143 were compared between groups using Kolmogorov-Smirnov and one-way ANOVA tests in SPSS software.

RESULTS

At the end of the first 8 weeks, the HFD group weighed significantly more than the NFD group. LC significantly decreased weight gain (4.2%) compared to the control group, whereas CLA alone (3.5%) or in combination with LC (3.1%) did not significantly slow weight gain. Real-time PCR results showed that the HFD group had higher miR-143 levels and lower miR-27a levels compared to the NFD group. LC and CLA increased miR-27a expression after 4 weeks, but their combination decreased miR-27a expression. CLA alone reduced miR-143 expression, whereas LC had almost no effect. Their combination also reduced miR-143 expression.

CONCLUSION

CLA and LC, which are considered weight loss supplements, can potentially regulate metabolism and cellular pathways. However, their combination did not show a synergistic effect on weight loss, possibly due to the reduction in miR-27a expression. Further studies are needed to evaluate the effects of combined fat burners on obesity treatment.

The Synergistic Effects of the Combination of L-Carnitine and Lycopene on the Lycopene Bioavailability and Duodenal Health of Roosters

The objective of this study was to investigate the impact of Lycopene and L-Carnitine, individually or in combination, on various physiological and molecular factors related to intestinal health and absorption ability in Roosters, such as intestinal morphology, serum biochemical parameters, genes involved in Lycopene uptake, nutritional transport genes, and tight junction genes. The findings of the study revealed that the combination of L-Carnitine and Lycopene supplementation had been found to increase the serum concentration levels of TP and ALB. Interestingly, the relative mRNA expression of genes responsible for Lycopene uptakes, such as SR-BI and BCO2, was higher in the LC group compared to other groups. Additionally, the expression of specific nutritional transport genes in the duodenum was significantly affected by both CAR and LC supplementation groups. The tight junction gene OCLN showed a significant increase in expression in the combination group compared to using either Lycopene or L-Carnitine alone. This study concludes that using Lycopene and L-carnitine in combination in poultry feed can potentially improve intestinal morphology and serum biochemical parameters, increase Lycopene bioavailability, improve nutrients uptake, and enhance the integrity of duodenal tight junctions in Roosters.

L-Carnitine alleviates hepatic and renal mitochondrial-dependent apoptotic progression induced by letrozole in female rats through modulation of Nrf-2, Cyt c and CASP-3 signaling

Letrozole (LTZ) is a non-steroidal aromatase inhibitor that is commonly used in breast cancer therapy. It has several side effects that might lead to the drug's cessation and data of LTZ's potential adverse effects on the hepatorenal microenvironment was conflicting. In addition, searching for therapeutic interventions that could modulate its adverse effects will be very beneficial. So, this study aims to determine the impact of LTZ on the hepatorenal microenvironment in cyclic female rats with a proposed regulatory role of L-Carnitine (LC) supplementation giving molecular insights into its possible mechanism of action. LTZ (1 mg/kg using 0.5% carboxy methyl cellulose as a vehicle for 21 consecutive days orally) to assess its impact on hepatorenal microenvironment. After treatment with LC (100 mg/kg orally) for 14 days, hepatorenal redox state (lipid peroxides (MDA), reduced glutathione (GSH) and catalase enzyme (CAT)), as well as relative gene expression of nuclear factor erythroid 2-related factor 2 (Nrf-2), cytochrome-c (Cyt c) and caspase-3 (CASP-3) were evaluated. Histopathological examination and immunohistochemical staining of CASP-3 in both liver and kidney were done. LTZ altered hepatic and renal functions. Relative gene expression of hepatorenal Nrf-2, Cyt c and CASP-3 as well as redox state revealed significant deterioration. Also, the liver and kidney tissues showed several micromorphological changes and intense reaction to CASP-3 upon immunohistochemical staining. It can be concluded that LC alleviates LTZ induced hepatorenal oxidative stress (OS) and mitochondrial-dependent apoptotic progression through modulation of Nrf-2, Cyt c, and CASP-3 signaling in female rats.

The effects of adjunctive treatment with L-carnitine on monitoring laboratory variables in ICU patients: a double-blinded randomized controlled clinical trial

BACKGROUND

Critically ill patients must be monitored constantly in intensive care units (ICUs). Among many laboratory variables, nutritional status indicators are a key role in the prognosis of diseases. We investigated the effects of L-carnitine adjunctive therapy on monitoring variables in critical illness.

METHOD

A prospective, double-blind, randomized controlled trial was implemented in a medical ICU. Participants were 54 patients, aged > 18 years, with multiple conditions, randomly assigned to receive 3 g L-carnitine per day or placebo, along with enteral feeding, for 1 week. Primary outcomes included monitoring variables related to nutritional status.

RESULT

Of 54 patients randomly assigned, 51 completed the trial. Serum albumin (Alb) (P-value: 0.001), total protein (P-value: 0.003), and calcium (Ca) (0.044) significantly increased in the intervention vs. control group. Alanine transaminase (ALT) (0.022), lactate (<0.001), creatinine (Cr) (0.005), and international normalized ratio (INR) (0.049) decreased meaningfully in the intervention vs. control group.

CONCLUSION

L-Carnitine supplementation in critically ill patients can improve several parameters including INR, Cr, ALT, lactate, Ca, Alb, and total protein.

TRIAL REGISTRATION

Iranian Registry of Clinical Trials IRCT 20151108024938N2. This trial was approved by the Research Ethics Committee of Mashhad University of Medical Sciences (registration code: IR.MUMS.fm.REC.1396.671) (available at https://en.irct.ir/trial/30748 , May 2018).

Protective effects of L-carnitine against valproic acid-induced memory impairment and anxiety-like behavior in adult rat

This study was designed to explore the effects of valproic acid (VPA) on spatial and passive avoidance learning and memory as well as to assess the protective effects of L-Carnitine (LC) against VPA-induced memory deficit in the rat. Male Wistar rats received VPA (300 mg/kg/daily by i.p. injection), or LC (50 mg/kg/ daily by i.p. injection), or co-treatment with VPA and LC for 28 days. Following 28 days, Elevated Plus-Maze (EPM), Morris Water Maze (MWM), and Passive Avoidance Learning (PAL) tasks were used to evaluate the anxiety-like behavior and spatial and passive learning and memory, respectively. Our results showed that VPA has no effect on memory acquisition (in both MWM and PAL) but induced reference memory impairment. We demonstrated that treatment with LC partially ameliorated the impairment in the retrieval of reference memory and passive avoidance learning. Moreover, VPA increased anxiety-like behavior, which was partially reversed by the administration of LC. In conclusion, these results show that LC is effective in counteracting the anxiety-like behavior and reference memory impairment caused by VPA. Therefore, LC may serve as a possible therapeutic agent for VPA-induced memory change.

Effects of L-Carnitine Treatment on Kidney Mitochondria and Macrophages in Mice with Diabetic Nephropathy

INTRODUCTION

In diabetic nephropathy (DN), mitochondrial dysfunction and leakage of mitochondrial DNA (mtDNA) are caused by the downregulation of superoxide dismutase 2 (SOD2). mtDNA induces the activation of Toll-like receptor (TLR) 9, which is present in macrophages (Mφs), and triggers their activation.

METHODS

We orally administered L-carnitine, which exerts protective effects on the mitochondria, to obesity-induced DN (db/db) mice for 8 weeks. We then investigated the effects of L-carnitine on kidney mitochondrial reactive oxygen species (mtROS) production, circulating mtDNA content, and kidney CD11bhigh/CD11blow Mφ functions.

RESULTS

In db/db mice, mtROS production increased in proximal tubular cells and kidney CD11blow Mφs; both Mφ types showed enhanced TLR9 expression. L-Carnitine treatment suppressed mtROS production in both proximal tubular cells and CD11blow Mφs (p < 0.01), with improved SOD2 expression in the kidney (p < 0.01), decreased circulating mtDNA content, and reduced albuminuria. Moreover, it suppressed Mφ infiltration into kidneys and reduced TLR9 expression in Mφs (p < 0.01), thereby lowering tumor necrosis factor-α production in CD11bhigh Mφs (p < 0.05) and ROS production by CD11blow Mφs (p < 0.01). Collectively, these changes alleviated DN symptoms.

CONCLUSION

The positive effects of L-carnitine on DN suggest its potential as a novel therapeutic agent against obesity-linked DN.

Beneficial impact of dietary methyl methionine sulfonium chloride and/or L-carnitine supplementation on growth performance, feed efficiency, and serum biochemical parameters in broiler chicken: role of IGF-1 and MSTN genes

The purpose of this study was to examine the effect of dietary supplementation with methyl methionine sulfonium chloride (MMSC), and L-carnitine (L-CAR) alone or in combination on the growth performance of broilers through their impact on the expression of IGF-1 and MSTN genes associated with growth in broilers. One-day-old female Ross 308 broiler chicks were allocated into four groups, each of which received a broiler starter diet and water daily ad libitum. The control group (group 1) was given drinking water without any additives. Group 2 received 0.25 g L-carnitine per liter of drinking water, group 3 received 0.25 g MMSC per liter of drinking water, and group 4 received 0.25 g of both L-carnitine and MMSC per liter of drinking water. Birds were given a starter diet to 21 days after which they received a broiler grower diet to 35 days when the experiment ended. There were five replicate groups of 12 birds per treatment. Body weights and feed intake were recorded weekly. Compared to the control group of birds, supplementation with MMSC either alone or in combination with L-carnitine resulted in an increase in growth rate or feed utilization efficiency; L-carnitine by itself had no effect. MMSC supplementation, again either alone or in combination with L-carnitine, increased jejunal and ileal villi height, increased serum total proteins and globulins, downregulated myostatin (MSTN) mRNA, and upregulated insulin growth factor-1 (IGF-1) mRNA expression. Supplementation with L-carnitine alone showed none of these effects. We conclude that MMSC supplementation improved growth performance through the upregulation of IGF-1 mRNA expression and downregulation of MSTN mRNA expression.

L-Carnitine effect on induced hyperlipidemia on premature rats: fertility profile

This study was designed to investigate the effect of hypercholesterolemia on the reproductive performance of premature male rats and to evaluate the influence of L-Carnitine (CAR) in maintaining their fertility. Sixty rats were divided randomly into three groups. Control group (CG n=20 rats), cholesterol feeding group 1 (CFG1 n=20 rats) fed 1.5% cholesterol with diet for one month, and cholesterol feeding group 2 (CFG2 n=20 rats) fed 1.5% cholesterol with diet + CAR 150 mg/kg body weight (B.W.) given by water for one month. Results showed a significant increase in body weight of CFG1 compared with CG and CFG2. The lipid profile of CFG1 after one month of feeding cholesterol showed a significant increase in serum cholesterol and triglyceride compared with CG and with the group that watered by CAR and CFG2. Results of sperms parameters in CGF2 showed a significant increase in sperms count with sperms live percentage and a significant decrease in sperms abnormalities percentage compared with CGF1 and CG. The hormonal profile showed a significant decrease in serum testosterone levels in rats from CFG1 compared with CFG2 and CG. In conclusion, CAR is a powerful antioxidant that can maintain the parameters of sperms of hypercholesterolemic premature rats, which may enhance the fertilizing ability of subfertile rats that may occur due to hyperlipidemia.

Protective effects of melatonin and L-carnitine against methotrexate-induced toxicity in isolated rat hepatocytes

The present study was designed to evaluate the possible protective effects of melatonin (MEL) and/or L-carnitine (L-CAR) against methotrexate (MTX)-induced toxicity in isolated rat hepatocytes. Hepatocytes were prepared using collagenase techniques of perfusion and digestion of rat liver. Trypan blue uptake, as well as, glutathione (GSH), lipid peroxidation (LPO), nitric oxide (NO), and tumor necrosis factor-alpha (TNF-α) levels were measured. Caspase-3 activity was also assessed. Pre-incubation of hepatocytes with MEL (1 mM) and/or L-CAR (10 mM) 30 min prior to intoxication with MTX, significantly protected hepatocytes against toxicity. In addition, LPO, NO, TNF-α levels, and caspase-3 activity were decreased in comparison to the MTX-intoxicated group. Furthermore, the two drugs increased the MTX-depleted GSH level. MEL and L-CAR prevented MTX-induced hepatocytotoxicity, at least partly, by their antioxidative, antiinflammatory, and antiapoptotic effects. Further studies are recommended on the clinical pharmacologic and toxicologic effects of MEL and L-CAR in patients receiving MTX.

Ten-year changes in plasma L-carnitine levels and risk of coronary heart disease

PURPOSE

L-Carnitine is abundant in animal source foods, particularly red meat, and circulating L-carnitine may be related to the incidence of coronary heart disease (CHD). We investigated whether long-term changes in plasma L-carnitine over 10 years were associated with the CHD incidence and also examined joint associations of carnitine-rich red meat consumption and L-carnitine changes on the subsequent risk of CHD.

METHODS

This prospective nested case-control study included 772 healthy women at baseline (386 incident CHD cases and 386 healthy controls). Plasma L-carnitine levels were measured both at the first (1989-90) and second blood collections (2000-02). Incident cases of CHD were prospectively followed from the date of the second blood collection through 2016.

RESULTS

Overall, a greater increase in L-carnitine from the first to the second time point was related to a higher risk of CHD, regardless of the initial L-carnitine levels (relative risk: 1.36 (95% CI 0.999, 1.84) per 1-SD increase). The 10-year changes in L-carnitine were positively associated with red meat consumption over time, and women with higher red meat intake (≥ 36 g/day) and with greater increases in L-carnitine had a 1.86 (95% CI 1.13, 3.09) times increased risk of CHD, as compared to those with lower red meat intake and lesser increases in L-carnitine.

CONCLUSION

Long-term increases in L-carnitine levels were associated with the subsequent incidence of CHD, especially among women with higher intake of red meat. Our results suggest the importance of atherogenic L-carnitine changes and dietary intakes over time in the prevention of CHD.

The effect of L-carnitine supplementation on insulin resistance, sex hormone-binding globulin and lipid profile in overweight/obese women with polycystic ovary syndrome: a randomized clinical trial

PURPOSE

Polycystic ovary syndrome (PCOS) is a common endocrine disorder among reproductive-age women. Insulin resistance and dyslipidemia are linked to PCOS. L-Carnitine supplementation as a management strategy for women with PCOS has been proposed. The effect of L-carnitine supplementation on insulin resistance, sex hormone-binding globulin (SHBG) and lipid profile in overweight/obese women with PCOS was investigated.

METHODS

This randomized, double-blind, controlled clinical trial, was conducted on 62overweight/obese women with PCOS. Participants were randomly assigned into two groups to receive 1000 mg/day L-carnitine or placebo (1000 mg starch) for 12 weeks.

RESULTS

L-Carnitine supplementation compared to the placebo showed a significant improvement in insulin [- 0.7 (- 7.3 to 4.0) vs. 0.7 (- 3.0 to 5.2); P = 0.001], homeostatic model assessment for insulin resistance [- 0.4 (- 1.7 to 1.1) vs. 0.0 (- 0.7 to 1.3); P = 0.002], quantitative insulin sensitivity check index (+ 0.01 ± 0.02 vs. - 0.01 ± 0.01; P = 0.02) and a non-significant change toward improvement in SHBG (+ 11.5 ± 40.2 vs. - 3.2 ± 40.2; P = 0.2). However, there was no significant differences between the two groups in serum levels of fasting plasma glucose, total cholesterol, triglyceride, low density lipoprotein-cholesterol and high density lipoprotein cholesterol (P > 0.05).

CONCLUSION

12-week L-carnitine supplementation in overweight or obese women with PCOS ameliorate insulin resistance, but has no effect on SHBG and lipid profile. Studies with higher dosages and duration of L-carnitine intake are required. The trial was registered on 30 December 2019 at Iranian Registry of Clinical Trials IRCT20191016045131N1.

TRIAL REGISTRATION

Registered on 30th December 2019 at Iranian Registry of Clinical Trials (IRCT20191016045131N1).

Mechanistic perspectives on differential mitochondrial-based neuroprotective effects of several carnitine forms in Alzheimer's disease in vitro model

Mitochondrial deregulation has emerged as one of the earliest pathological events in Alzheimer's disease (AD), the most common age-related neurodegenerative disorder. Improvement of mitochondrial function in AD has been considered a relevant therapeutic approach. L-carnitine (LC), an amino acid derivative involved in the transport of long-chain fatty acids into mitochondria, was previously demonstrated to improve mitochondrial function, having beneficial effects in neurological disorders; moreover, acetyl-L-carnitine (ALC) is currently under phase 4 clinical trial for AD (ClinicalTrials.gov NCT01320527). Thus, in the present study, we investigated the impact of different forms of carnitines, namely LC, ALC and propionyl-L-carnitine (PLC) on mitochondrial toxicity induced by amyloid-beta peptide 1-42 oligomers (AβO; 1 μM) in mature rat hippocampal neurons. Our results indicate that 5 mM LC, ALC and PLC totally rescued the mitochondrial membrane potential and alleviated both the decrease in oxygen consumption rates and the increase in mitochondrial fragmentation induced by AβO. These could contribute to the prevention of neuronal death by apoptosis. Moreover, only ALC ameliorated AβO-evoked changes in mitochondrial movement by reducing the number of stationary mitochondria and promoting reversal mitochondrial movement. Data suggest that carnitines (LC, ALC and PLC) may act differentially to counteract changes in mitochondrial function and movement in neurons subjected to AβO, thus counteracting AD-related pathological phenotypes.

Additional L-Carnitine Reduced the Risk of Hospitalization in Patients with Overt Hepatic Encephalopathy on Rifaximin

BACKGROUND

Data regarding the additional effect on the recurrence of hepatic encephalopathy (HE) after oral L-carnitine administration are scarce.

OBJECTIVE

This study aimed to assess the additional effects of L-carnitine in patients who were receiving rifaximin for HE.

METHODS

This randomized study comprised a screening visit and a 12-week treatment period. Patients who fulfilled the eligibility criteria were randomized to either group A (additional rifaximin) or group B (additional L-carnitine and rifaximin). Group A received 1,200 mg/day of rifaximin. Group B received 1,500 mg/day of L-carnitine and rifaximin at 1,200 mg/day. The endpoints were the changes in the portal systemic encephalopathy (PSE) index and the admission rate from the baseline for the duration of the study in both groups.

RESULTS

Eighty-three patients were randomized to either group A (n = 42) or group B (n = 41). In group A, the PSE index decreased from 0.35 ± 0.09 at baseline to 0.27 ± 0.11 on the final evaluation day (p = 0.001). In group B, the PSE index decreased from 0.37 ± 0.09 at baseline to 0.24 ± 0.11 on the final evaluation day (p = 0.001). Although there was not a significant reduction in the PSE index in group A compared to that in group B (p = 0.202), the admission rates were 30.9% and 9.8% in groups A and B, respectively. Additional L-carnitine significantly reduced the admission rate (p = 0.028).

CONCLUSION

L-Carnitine addition reduced the risk of hospitalization for patients who received rifaximin for HE.

Effect of Nigella sativa, atorvastatin, or L-Carnitine on high fat diet-induced obesity in adult male Albino rats

Obesity is increasing rapidly across the globe. It is widely accepted that natural products with a long safety background may modulate obesity. The current work aimed to investigate the effect of Nigella sativa, atorvastatin, or L-Carnitine on high-fat diet-induced obesity in white male albino rats. A regular basal diet was fed to 7 rats, and a high-fat diet (HFD) was fed to 24 rats throughout the study for 12 weeks. The HFD group was split equally into four subgroups, each containing six rats. The first group fed on HFD with no medication, the second group received HFD+ Nigella sativa, the third group received HFD+ atorvastatin, and the fourth group received HFD+L-carnitine. At the beginning of the seventh week (the start of the treatment regimen), Nigella sativa, atorvastatin, or L-Carnitine were administered for six weeks. Glucose, body weight, serum atherogenic index (AI), ALT, and AST activities were analyzed. The pathological alterations in the hepatic tissues were examined microscopically and scored. The results revealed that the HFD diet significantly increased the final body weight, serum AI, and serum levels of liver enzymes. Treatment with L-carnitine or Nigella sativa significantly normalized the lipid profile and decreased the final body weight, serum AI, and Serum ALT. Histopathological examination of the liver of HFD received rats showed features of steatosis, which were mitigated by the administration of Nigella sativa or L-Carnitine, while atorvastatin had no significant effect on the improvement of hepatic lesions. Collectively, study findings showed that Nigella sativa or L-Carnitine has mitigated effects on metabolic and histopathological changes in the liver tissues of rats fed with HFD.

Interaction of supplementary L-carnitine and dietary energy levels on feed utilization and blood constituents in New Zealand White rabbits reared under summer conditions

In the summer season, the harmful effects of high ambient temperatures on rabbit productivity have attained global interest. Therefore, the use of new nutritional strategies to improve heat tolerance in rabbits has become highly needed. In the current experiment, the effect of the addition of L-carnitine (LC) to normal (NE) or high-energy (HE) diets of growing rabbits reared under summer conditions on their productive performance, physiological indicators, and carcass characteristics was assessed. For this purpose, a 2 × 2 factorial arrangement of treatments was used with two dietary levels of energy of 10.00 and 11.22 MJ kg^-1 diet of NE and HE, respectively, which was fortified with 0 or 50 mg of LC kg^-1 of diet (LC0 and LC50, respectively). The feeding trial was conducted using 80 male rabbits (initial body weight, 630.7 ± 1.3 g; 35-day-old), and it lasted for 56 days. Throughout the experiment, the average temperature humidity index was 35.49 reflecting very severe heat stress conditions. Rectal temperature, heart rate, and respiration rate decreased significantly in rabbits fed NE+LC50, HE+LC0, and HE+LC50 diets compared with those fed NE diets without supplementation. Simultaneously, growth indices and feed conversion ratio were enhanced significantly. Rabbits fed NE+LC50, HE+LC0, and HE+LC50 diets showed significantly higher blood hemoglobin, white blood cell counts, total protein, glucose, and red blood cell counts, compared with those fed a NE+LC0 diet. Rabbits fed NE+LC50 and HE+LC50 showed higher economic efficiency. In conclusion, growing rabbits reared under summer conditions responded positively to LC supplementation and HE diets, in terms of the highest growth performance, feed conversion, and physiological and biochemical indicators, making them potentially safe to use.

Effect of L-carnitine supplementation on renal anemia in patients on hemodialysis: a meta-analysis

BACKGROUND

L-carnitine is an amino acid derivative that is thought to be helpful for treating renal anemia in hemodialysis patients. However, the mechanism remains to be fully elucidated.

METHODS

A literature search was performed on PubMed, Embase, and Cochrane Central Register of Controlled Trials to identify randomized controlled trials (RCTs) and conduct a meta-analysis for investigating the effect of L-carnitine in the treatment of renal anemia in participants receiving hemodialysis.

RESULTS

A total of 18 eligible trials with 1090 participants were included in this study. L-carnitine can significantly increase plasma free L-carnitine levels (mean difference [MD]: 140.53, 95% confidence interval [CI] 102.22-178.85; P < 0.00001), decrease the erythropoietin responsiveness index (ERI; MD: -2.72, 95% CI -3.20 to -2.24; P < 0.00001) and the required erythropoiesis-stimulating agent (ESA) doses (MD: -1.70, 95% CI -2.04 to -1.36; P < 0.00001). However, the use of L-carnitine was not associated with a higher hemoglobin level (MD: 0.18, 95% CI -0.20 to 0.55; P = 0.35) and hematocrit level (MD: 1.07, 95% CI -0.73 to 2.87; P = 0.24). In subgroup analyses, the effects of L-carnitine supplementation on renal anemia in patients on hemodialysis were independent of the treatment duration and intervention routes.

CONCLUSION

The present meta-analysis indicated that L-carnitine therapy significantly increased plasma L-carnitine concentrations, improved the response to ESA, decreased the required ESA doses in patients receiving hemodialysis, and maintained hemoglobin and hematocrit levels. L-carnitine supplementation should be supported in hemodialysis patients. However, the relationship between L-carnitine treatment and long-term outcomes is still unclear. Further high-quality RCTs are needed to verify our findings.

L-Carnitine supplementation for the prevention of postoperative atrial fibrillation in aortic valve surgery

OBJECTIVES

L-Carnitine, a quaternary amine, improves fatty acid metabolism in the heart and has anti-inflammatory effects. Several studies have reported the efficacy of L-carnitine for the prophylaxis of arrhythmia. We assessed the clinical effectiveness of L-carnitine in preventing postoperative atrial fibrillation (POAF) in aortic valve surgery.

METHODS

Thirty patients who underwent aortic valve surgery were included. Fifteen patients had no prophylaxis other than conventional measures (control), while 15 patients received oral L-carnitine for 9 days (daily dose of 3 g). The incidence of POAF during 1 week after surgery was compared between the two groups. The multivariable logistic regression analysis for POAF was performed using the pre- and intraoperative parameters.

RESULTS

Preoperative characteristics and operative data were comparable between the groups. The POAF rate was significantly lower in the L-carnitine group than in the control (20% and 60%, respectively; P = 0.025). L-Carnitine use was an independently negative predictor for POAF (odds ratio 0.067; 95% confidence interval 0.006-0.768).

CONCLUSIONS

L-Carnitine administration may have potential for the prevention of POAF in aortic valve surgery.

Beneficial Effects of L-Carnitine Supplementation during IVM of Canine Oocytes on Their Nuclear Maturation and Development In Vitro

Simple Summary

In vitro production of canine embryos is a technique that can be used as a model to conserve endangered species and to establish efficient breeding systems for domestic dogs. However, compared with other species, the success rates of in vitro embryo production (IVEP) in dogs are low. L-Carnitine (LC) is a small water-soluble molecule; it plays an essential role in fatty acid metabolism and acts as a potent antioxidant. Various studies have reported the beneficial impacts of LC on IVEP in many mammalian species other than dogs. Therefore, these experiments investigated the effects of LC supplementation during in vitro maturation (IVM) on canine oocytes maturation, fertilization, and development in vitro. We show that the supplementation of IVM media with LC has positive impacts on oocyte maturation, fertilization, and preimplantation embryo development rates. We also demonstrate that 0.6 mg/mL LC is the most beneficial concentration to be used. It resulted in significantly higher maturation, fertilization, and embryo developmental rates than the control and other LC concentrations. These outcomes are essential for refining the IVM conditions that can advance the efficiency of assisted reproductive technologies (ARTs) in dogs.

Abstract

This study aimed to investigate the effect of L-Carnitine (LC) supplementation during in vitro maturation (IVM) of canine oocytes on nuclear maturation, fertilization status, and preimplantation development. Cumulus–oocyte complexes (COCs) collected from the ovaries of ovariohysterectomized female dogs were matured in vitro for 72 h in a TCM-199 medium supplemented with (0.1, 0.3, 0.6, 1.0, or 2.0 mg/mL) or without (0.0 mg/mL) LC. Matured oocytes were fertilized in vitro with frozen–thawed spermatozoa, and zygotes were cultured in a SOF medium for 7 days. IVM rates were higher (p ≤ 0.05) in 0.3 and 0.6 mg/mL LC supplemented groups than in the control (0.0 mg/mL LC) and other LC groups. Fertilization (18 h postinsemination (pi)) and cleavage (2–16-cell stage at day 3 pi) rates were higher (p ≤ 0.05) in the 0.6 mg/mL LC group than in the control and 0.1, 1.0, and 2 mg/mL LC supplemented groups. Interestingly, 4.5% of fertilized oocytes developed to morula (day 5 pi) in the 0.6 mg/mL LC group, which was higher (p ≤ 0.05) than those developed in the 0.3 mg/mL group (1.0%). No cleaved embryos developed to morula in other groups. In conclusion, LC supplementation at 0.6 mg/mL during IVM of canine oocytes improved their maturation, fertilization, and preimplantation embryo development rates following IVF and in vitro culture (IVC).

The effects of L-carnitine supplementation on lipid concentrations inpatients with type 2 diabetes: A systematic review and meta-analysis of randomized clinical trials

This meta-analysis was performed to assess the effect of L-carnitine supplementation on lipid profile. A systematic search were conducted in PubMed and Scopus to identify randomized clinical trials (RCTs) which evaluated the effects of L-carnitine on lipid profile. Pooled effect sizes were measured using random-effect model (Dersimonian-Laird). Meta-analysis showed that L-carnitine supplementation significantly reduced total cholesterol (TC) (weighted mean difference [WMD]: -8.17 mg/dL; 95% CI,-14.68 to -1.65, I²=52.2%, P = 0.041). Baseline level of TC was a source of heterogeneity, with a greater effect in studies with a baseline level of more than 200 mg/d (WMD: -11.93 mg/dL; 95% CI, -20.80 to-3.05). L-carnitine also significantly decreased low-density lipoprotein-cholesterol (LDL-C) (WMD:-5.22 mg/dL; 95% CI, -9.54 to -0.91, I²=66.7%, P = 0.010), and LDL-C level <100 mg/dL), trial duration,and L-carnitine dosage were potential sources of heterogeneity. L-carnitine supplementation appeared to have no significant effect on high-density lipoprotein-cholesterol (HDL-C) (WMD: -0.51 mg/dL;95% CI, -2.45 to 1.44) and triglyceride (TG) (WMD: 2.80 mg/dL; 95% CI, -8.09 to 13.69). This meta-analysisrevealed that L-carnitine may have favorable effects on lipid profile, especially LDL-C and TC. However, further RCTs are needed to confirm the veracity of these results, particularly among hyperlipidemic patients.