Protective role of L-carnitine on liver and heart lipid peroxidation in atherosclerotic rats

L-carnitine supplementation in conventional slow and ultra-rapid freezing media improves motility, membrane integrity, and fertilizing ability of dog epididymal sperm

This study aimed to assess the impact of L-carnitine (LC) supplementation in conventional-slow (CS) and ultra-rapid (UR) freezing media on post-thaw quality and fertilizing ability of dog epididymal spermatozoa. Sperm samples were collected from 60 epididymides obtained from 30 adult orchiectomized dogs via retrograde flushing. Twenty pooled sperm samples were then created (3 epididymal samples/pool). Four treatments were established according to the freezing method (CS and UR) and LC supplementation (5 and 0 mM [control, Co]): CS-LC5, CS-Co, UR-LC5, and UR-Co. The CS freezing involved exposing 0.25 mL straw to liquid nitrogen vapors (LN2), while UR freezing submerged 30-µL drops of sperm samples directly into LN2. Sperm kinematics, membrane integrity, and fertilizing ability (by heterologous in vitro fertilization using bovine oocytes) were evaluated for all treatments. Post-thaw results revealed that the CS freezing treatments resulted in significantly higher values (P < 0.05) of curvilinear and average-path velocities, and beat-cross frequency compared to the UR freezing treatments, regardless of LC supplementation. The CS-LC5 and UR-LC5 treatments cryoprotected the sperm by increasing (P < 0.05) the percentage of 'live-sperm/intact-acrosome' compared to their controls treatments CS-Co and UR-Co. Regarding fertilizing ability, the CS-LC5 treatment yielded a higher percentage (P < 0.05) of pronuclei formation compared to both UR treatments. The UR-LC5 treatment, however, obtained greater percentage (P < 0.05) than their control UR-Co. In conclusion, supplementation with L-carnitine in conventional-slow and ultra-rapid freezing improved sperm motility, plasma, and acrosome membranes integrity and fertilizing ability of dog epididymal spermatozoa.

Nutraceutical interventions for erectile dysfunction: a systematic review and network meta-analysis

BACKGROUND

Although nutraceutical-based treatments are often offered for erectile dysfunction (ED), their efficacy remains doubtful, and the choice of one substance over the other is challenged by the dearth of head-to-head comparative studies.

AIM

We aimed to compare the efficacy of available nutraceutical interventions, alone or in combination with phosphodiesterase type 5 inhibitors (PDE5i), in improving erectile function in men with ED through a network meta-analysis (NMA), which incorporates direct and indirect evidence into one model thus generating a hierarchy of effectiveness.

METHODS

PubMed, Scopus, Web of Sciences, and Cochrane Library databases were searched for randomized placebo-controlled trials (RCTs) assessing the effect of any nutraceutical regimen in improving erectile function when compared to each other, placebo, and/or PDE5i in men with ED. Data were included in a random-effects NMA, where efficacy of treatments was ranked by surface under the cumulative ranking curve (SUCRA). Two NMAs were also conducted separately for organic and non-organic ED. Reciprocal comparisons between all treatments were analyzed by league tables.

OUTCOMES

The main outcome was the standardized mean difference in the score of the International Index of Erectile Function (IIEF)-5 or IIEF-6.

RESULTS

Fifteen RCTs provided information on 1000 men with ED. In the overall NMA, compared to placebo, the combination propionyl L-carnitine (PLC) + acetyl L-carnitine (ALC) + Sildenafil was associated with the highest SUCRA (97%) in improving erectile function score, followed by L-Arginine + Tadalafil (84%), Sildenafil (79%), Tadalafil (72%), and L-Arginine (52%). No other treatment regimen showed efficacy with statistical significance. In patients with organic ED, the efficacy of Sildenafil and Tadalafil was significantly improved by PLC + ALC and L-Arginine, respectively. On the contrary, in non-organic ED, nutraceuticals did not improve the therapeutic performance of daily Tadalafil.

CLINICAL IMPLICATIONS

This NMA contributes valuable insights into the potential of nutraceutical interventions for ED.

STRENGTHS AND LIMITATIONS

We employed strict inclusion criteria related to study design and diagnostic tool, ensuring the assumption of transitivity and the consistency of the analysis.

CONCLUSION

Against a background of general ineffectiveness of most nutraceutical interventions, L-Arginine and the mix PLC + ALC appeared to be of some usefulness in improving erectile function, especially in combination with PDE5i in organic ED.

Analysis of evidence on nutraceutical interventions for Peyronie's disease: a guideline-based critical review

INTRODUCTION

The management of Peyronie's disease (PD) is a challenge for the clinician. Despite the lack of etiologic therapy, different nonsurgical approaches have often been empirically proposed. The most used treatment is based on nutraceutical drugs with antioxidant activity, although such an intervention remains controversial.

OBJECTIVES

We reviewed the evidence from the randomized controlled trials included in the recommendations of the American Urological Association (AUA), Canadian Urological Association (CUA), European Association of Urology, and International Society for Sexual Medicine.

METHODS

We searched PubMed, Scopus, Web of Science, and Cochrane Library for randomized controlled trials, reviews, and guidelines on nutraceutical interventions for PD.

RESULTS

Our analysis provides detailed information on potential interventions, underlying the inconsistent evidence. Acetyl esters of carnitine, although not recommended by any of the available guidelines, showed potential benefit in some selected studies. Omega-3 fatty acids are not recommended due to withdrawn study evidence. The CUA and AUA were the only societies to consider the use of coenzyme Q10. While the CUA suggested that it might be offered as a treatment option, the AUA refrained from taking a definitive stance due to insufficient evidence. Similarly, conflicting recommendations have been produced on potassium para-aminobenzoate. While the CUA considers potassium para-aminobenzoate potentially useful in slowing PD progression, the AUA deems the evidence insufficient. Conversely, both the International Society for Sexual Medicine and European Association of Urology do not recommend its use.

CONCLUSION

This critical comparative analysis of the most recent guidelines produced by the leading scientific societies highlights some inconsistencies in the recommendations on nutraceutical intervention for PD, even within a background of overall ineffectiveness of this treatment approach.

Protective effect of l-carnitine-loaded solid lipid nanoparticles against H2O2-induced genotoxicity and apoptosis

L-carnitine (LC) is a highly water-soluble compound involved in the β-oxidation of lipids and transportation of long-chain fatty acids across the membrane of mitochondria. However, the higher hydrophilicity of LC limits its free diffusion across the bilayer lipid membrane of intestinal epithelium in oral administration, decreasing oral bioavailability. Drug delivery with nanoparticles enhances cargo bioavailability and cellular uptake and improves therapeutic outcomes while decreasing unwanted side effects. Here, we proposed solid lipid nanoparticles (SLNs) as a hydrophobic carrier for LC delivery, aiming at increasing LC bioavailability and its protective role against intracellular oxidative stress damages. The LC-SLNs were prepared using the hot homogenization technique, and different physicochemical properties were investigated. The inhibition of H₂O₂-induced ROS generation in human umbilical vein endothelial cells (HUVECs) with plain LC and LC-SLNs was investigated. Moreover, various in vitro experiments were performed to assess whether LC-SLNs can protect HUVECs from H₂O₂-induced genotoxicity and apoptosis. The monodispersed and spherical blank SLNs and LC-SLNs were 104 ± 1.8 and 128 ± 1.5 nm, respectively with a drug loading (DL) of 11.49 ± 0.78 mg/mL and acceptable encapsulation efficiency (EE%) (69.09 ± 1.12) of LC-SLNs. The formulation process did not affect the antioxidant properties of LC. MTT assay and comet assay demonstrated that the LC-SLNs decreased cytotoxicity and genotoxicity of H₂O₂, respectively on HUVECs. Besides, LC-SLNs more inhibited ROS generation, along with apoptotic events in H₂O₂-treated HUVECs compared to the plain LC. Altogether, our findings affirmed the protective effects of LC-SLNs against H₂O₂-induced genotoxicity and apoptosis in HUVECs. In conclusion, LC-SLN formulation is a promising drug delivery system to overcome the bioavailability issue of hydrophilic LC, enhancing the antioxidant and biological properties of the plain LC.

Artemisinin and l-carnitine combination therapy alters the erythrocytes redox status

Hematopoiesis is a sensitive target of artemisinin (ART) and its derivatives, and hemolysis is one of their commonly reported side effects. L-carnitine (LC), an amino acid derivative involved in lipid metabolism, is beneficial for hematological parameters. Sixty adult laboratory mice were randomly divided into six groups. Group I (control) received saline and corn oil; groups II and III received therapeutic (50 mg/kg) and toxic (250 mg/kg) doses of ART, respectively; groups IV and V received 370 mg/kg LC along with the 50 and 250 mg/kg ART, respectively; and group VI received 370 mg/kg LC. Drugs were administered orally for seven consecutive days. The erythrocyte glucose 6-phosphate dehydrogenase (G6PD), catalase (CAT), and peroxidase (POX) activity, and the reduced glutathione (GSH) level were assessed by colorimetric methods. ART reduced the G6PD activity both at therapeutic and toxic doses. The therapeutic dose of ART reduced the CAT activity and the GSH level, non-significantly. The toxic dose of ART reduced the CAT activity and increased the POX activity. LC reduced the G6PD, CAT, and POX activities and increased GSH level. The therapeutic dose of ART and LC showed synergy in reducing the G6PD activity. LC and ART combination reduced POX activity and increased GSH level without any significant effect on the CAT activity. Inhibition of G6PD may be a potentially new mechanism of ART action. Co-administration of LC with ART or following treatment with ART may have protective effects on erythrocytes. This article is protected by copyright. All rights reserved.

Evaluation of unprotected and rumen-protected L-carnitine in vitro and in vivo

This study aimed to evaluate the effectiveness of unprotected and rumen-protected L-carnitine through in vitro tests, rumen degradation tests, and in vivo tests. Twelve rumen-fistulated crossbred rams with similar body weights of 55 ± 3.6 kg and ages of 3 ± 0.2 yr old were divided into three treatment groups in a 3 × 3 Latin square design, G1 (basal diet with no additives), G2 (unprotected L-carnitine), or G3 (rumen-protected L-carnitine). Ruminal fluid and blood samples were collected before morning feeding on the last day of each experimental period (21 d). The percentage of L-carnitine remaining in the simulated rumen and abomasum and rumen increased with the increase in the wall material ratio (P < 0.05). L-carnitine supplementation decreased the plasma urea nitrogen concentration in the sheep (P < 0.05). G3 resulted in higher glutathione peroxidase (GSH-Px) and superoxide dismutase (SOD) activities as well as higher total antioxidant capacity (T-AOC) and lower malondialdehyde (MDA) concentrations in plasma than G1, and the difference was significant among the groups (P < 0.01). Thus, L-carnitine in the rumen could be protected by encapsulation for a certain time. Unprotected and rumen-protected L-carnitine supplementation effectively enhanced the antioxidant capacity of sheep, and the antioxidant capacity of sheep supplemented with rumen-protected L-carnitine was higher than that of sheep supplemented with unprotected L-carnitine.

Natural and synthetic antioxidants targeting cardiac oxidative stress and redox signaling in cardiometabolic diseases

Cardiometabolic diseases (CMDs) are metabolic diseases (e.g., obesity, diabetes, atherosclerosis, rare genetic metabolic diseases, etc.) associated with cardiac pathologies. Pathophysiology of most CMDs involves increased production of reactive oxygen species and impaired antioxidant defense systems, resulting in cardiac oxidative stress (OxS). To alleviate OxS, various antioxidants have been investigated in several diseases with conflicting results. Here we review the effect of CMDs on cardiac redox homeostasis, the role of OxS in cardiac pathologies, as well as experimental and clinical data on the therapeutic potential of natural antioxidants (including resveratrol, quercetin, curcumin, vitamins A, C, and E, coenzyme Q10, etc.), synthetic antioxidants (including N-acetylcysteine, SOD mimetics, mitoTEMPO, SkQ1, etc.), and promoters of antioxidant enzymes in CMDs. As no antioxidant indicated for the prevention and/or treatment of CMDs has reached the market despite the large number of preclinical and clinical studies, a sizeable translational gap is evident in this field. Thus, we also highlight potential underlying factors that may contribute to the failure of translation of antioxidant therapies in CMDs.

The effect of vitamin E, L-carnitine, and ginger on production traits, immune response, and antioxidant status in two broiler strains exposed to chronic heat stress

The present study was designed to find the effect of natural and synthetic antioxidants on the performance of two broiler strains under high ambient temperature. A total of 320 day-old chicks of Hubbard and Cobb were reared for a period for 21 days under the same nutritional and management systems. On day 21 onward, one subgroup was kept as control while other subgroups were provided with vitamin E (250 mg/kg), ginger (2 g/kg), and L-carnitine (500 mg/kg) in basal diets. Body weight and feed conversion ratio (FCR) were significantly (P < 0.05) high in vitamin E-supplemented birds, while feed intake was significantly (P < 0.05) higher in L-carnitine supplemented birds irrespective of the strain. Antibody titer against infectious bursal disease (IBD) and paraoxonase (PON1) was significantly (P < 0.05) higher in vitamin E-supplemented birds compared to the other treatments. The number of heterophils and toal oxidant status (TOS) were significantly (P < 0.05) lower in vitamin E-supplemented birds. Blood glucose was significantly (P < 0.05) lower in vitamin E-supplemented birds, while total protein was significantly (P < 0.05) higher in vitamin E-supplemented group. In conclusion, the supplementation of vitamin E at the rate of 250 mg/kg improved the antioxidant status and immune response in the two broiler strains. Further, the two strains perform similarly in terms of performance and other health status parameters with no significant difference.

Cardioprotective effect of epigallocatechin-3-gallate against myocardial infarction in hypercholesterolemic rats

Cardiovascular diseases are closely associated with a high-cholesterol or high-fat diet. The aim of the present study was to investigate the cadioprotective effect of epigallocatechin-3-gallate (EGCG) in high-fat diet-fed rats, with special emphasis on myocardial infarction. A high-fat diet was administered to male Wistar rats for 45 days and the rats of the treatment group were administered EGCG via intraperitoneal injection for the last 15 days. The serum lipid profile, antioxidant enzyme activity, lipid peroxidation, lipid metabolic proteins and cardiac tissue markers were assessed. The myocardium and aorta were also histopathologically examined. The high-fat diet-fed rats were found to be hypercholesterolemic or exhibited abnormal values in the selected parameters. However, these abnormalities were reversed to near-normal values in the rats administered EGCG. Similarly, the enzymatic antioxidant activity and non-enzymatic antioxidant levels were improved with EGCG treatment in high-fat diet-fed rats. In addition, EGCG activated sirtuin 1, endothelial nitric oxide synthase and AMP-activated protein kinase α, which suggests that its protective effect is mediated through the stimulation of lipid metabolism. The histopathological examination further revealed that EGCG significantly prevented the development of tissue abnormalities and improved the morphology of myocardial tissue. Taken together, our results suggested that EGCG plays a significant role in the protection of the cardiovascular system against the high-fat diet. This is a preliminary study, emphasizing on the cardioprotective properties of EGCG. We are currently analyzing the molecular mechanism underlying the protective effects of EGCG.

Dietary and nutraceutical approach to type 2 diabetes

Nutritional medical treatment is the first step to achieve adequate glycemic control and prevent diabetic complications. Lifestyle changes include moderate weight loss (7%) and regular physical activity (150 min/week). The appropriate diet composition is < 30% total fat, < 10% saturated fats, > 15 g/1000 kcal fiber, half soluble, 45-60% of carbohydrates with amoderate intake of sugar (50 g/day) and protein intake of 15-20% of the total calories a day. Patients need to limit the intake of saturated fats to < 7% of the daily calorie intake. Monounsaturated fatty acids such as olive oil and other vegetable oils are recommended. L-carnitine, α-lipoic acid, berberine and ω-3 fatty acids can be useful supplements.

L-carnitine attenuates the development of kidney fibrosis in hypertensive rats by upregulating PPAR-γ

BACKGROUND

The development of renal fibrosis is a consequence of arterial hypertension. L-carnitine plays an essential role in the β-oxidation of fatty acids, and we have previously demonstrated hypotensive, antioxidant, and anti-inflammatory effects of L-carnitine in arterial hypertension. This work aims to analyze the effect of L-carnitine on renal fibrosis and to explore the participation of peroxisome-proliferator activated receptor (PPAR)-γ in this effect.

METHODS

Four groups or rats were used: control, treated with L-carnitine, treated with L-NAME, and treated with L-carnitine + L-NAME. Cultured rat kidney cells were also used to examine the role of PPAR-γ in L-carnitine effect.

RESULTS

An increase in the expression of collagen, transforming growth factor beta 1 (TGF-β1), connective tissue growth factor (CTGF), Nox2, and Nox4 was found in the kidney of L-NAME-treated rats. Hypertensive rats presented with an expansion of renal fibrotic areas, which was also accompanied by overexpression of proinflammatory cytokines, interleukin (IL)-1β, and IL-6. A reduction in the expression of PPAR-γ and in that of anti-inflammatory IL-10 was found in the kidney of these rats. Simultaneous treatment with L-carnitine attenuated the renal fibrosis (which correlated with a reduction of plasma TGF-β1 levels) and the pro-oxidative and proinflammatory status reported in L-NAME groups, with a concomitant increase in the expression of PPAR-γ. Furthermore, the antifibrotic effect of L-carnitine could be blocked by PPAR-γ inhibition.

CONCLUSIONS

This study confirms the efficacy of L-carnitine against hypertension-associated renal fibrosis from in vivo and in vitro studies and suggests that the L-carnitine effect occurs in a PPAR-γ-dependent manner.

The protective role of l-carnitine against cylindrospermopsin-induced oxidative stress in tilapia (Oreochromis niloticus)

Cylindrospermopsin (CYN) is one of the most important cyanotoxins in terms of both human health and environmental quality and is produced by several different species of cyanobacteria, including Aphanizomenon ovalisporum. The principal mechanisms of action of CYN involve inhibition of protein and glutathione synthesis. In addition, CYN-mediated genotoxicity results from DNA fragmentation. The results of both in vivo and in vitro studies suggest that oxidative stress also plays a significant role in CYN pathogenesis in fish. We investigated the protective effects of l-carnitine (LC) pre-treatment on A. ovalisporum-induced oxidative stress in cells containing CYN and deoxy-CYN, or pure standard CYN, in tilapia (Oreochromis niloticus) that had been acutely exposed via oral administration. Various oxidative stress markers, including lipid peroxidation (LPO), protein oxidation, DNA oxidation, and the ratio of reduced glutathione to oxidised glutathione (GSH/GSSG), and the activities of NADPH oxidase, superoxide dismutase (SOD), catalase (CAT), and gamma-glutamyl-cysteine synthetase (γ-GCS), were evaluated in the livers and kidneys of fish in the absence and presence of 400 or 880mgLC/kgfish/day during a 21 day period prior to CYN-intoxication. The results of our study demonstrated for the first time the beneficial antioxidant effects of LC dietary supplementation on oxidative stress status in fish. No pro-oxidant effects were detected at any of the LC doses assayed, suggesting that LC is a chemoprotectant that reduces hepatic and renal oxidative stress and may be effective when used for the prophylaxis and treatment of CYN-related intoxication in fish.

Progression of cyclophosphamide-induced acute renal metabolic damage in carnitine-depleted rat model

BACKGROUND

Little information is available regarding the mechanism of cyclophosphamide (CP)-induced renal damage. Therefore, this study examined whether carnitine deficiency constitutes a risk factor in and should be viewed as a mechanism during development of CP-induced nephrotoxicity and explored whether carnitine supplementation, using propionyl-L-carnitine (PLC), could offer protection against this toxicity.

METHODS

Experimental rats were assigned to one of six groups; the first three groups were injected intraperitoneally with normal saline, PLC (250 mg/kg/day) or D-carnitine (250 mg/kg/day) + Mildronate (200 mg/kg/day), respectively, for 10 successive days. The 4th, 5th and 6th groups received the same doses of normal saline, PLC or D-carnitine + Mildronate, respectively, for 5 successive days before and after a single dose of CP (200 mg/kg).

RESULTS

CP significantly increased serum creatinine, blood urea nitrogen (BUN), intramitochondrial acetyl-coenzyme A (CoA) and thiobarbituric acid reactive substances, significantly decreased total carnitine, intramitochondrial CoA-SH, adenosine triphosphate (ATP) and ATP/adenosine diphosphate (ADP) and reduced glutathione in kidney tissues. In carnitine-depleted rats, CP resulted in dramatic increase in serum nephrotoxicity indices and acetyl-CoA and induced progressive reduction in total carnitine, CoA-SH and ATP as well as severe histopathological lesions in kidney tissues. Interestingly, PLC completely reversed the biochemical and histopathological changes induced by CP to normal values.

CONCLUSIONS

Oxidative stress is not involved in CP-induced renal injury in this model. Carnitine deficiency and energy starvation constitute risk factors in and should be viewed as a mechanism during CP-induced nephrotoxicity. PLC prevents development of CP-induced nephrotoxicity by increasing intracellular carnitine content, intramitochondrial CoA-SH/acetyl-CoA ratio and energy production.

Systemic antioxidant properties of L-carnitine in two different models of arterial hypertension

In spite of a wide range of drugs being available in the market, treatment of arterial hypertension still remains a challenge, and new therapeutic strategies could be developed in order to improve the rate of success in controlling this disease. Since oxidative stress has gained importance in the last few years as one of the mechanisms involved in the origin and development of hypertension, and considering that L-carnitine (LC) is a useful compound in different pathologies characterized by increased oxidative status, the aim of the present study was to investigate the systemic antioxidant effect of LC and its correlation to blood pressure in two experimental models of hypertension: (1) spontaneously hypertensive rats (SHR) and (2) rats with hypertension induced by N(omega)-nitro-L-arginine methyl ester (L-NAME). Treatment with captopril was also performed in SHR in order to compare the antioxidant and antihypertensive effects of LC and captopril. The antioxidant defense capacity, in terms of antioxidant enzyme activity, glutathione system availability and plasma total antioxidant capacity, was measured in both animal models with or without an oral, chronic treatment with LC. All the antioxidant parameters studied were diminished in SHR and in L-NAME-treated animals, an alteration that was in general reversed after treatments with LC and captopril. In addition, LC produced a significant but not complete reduction of systolic and diastolic blood pressure levels in these two models of hypertension, whereas captopril was able to normalize blood pressure. Both LC and captopril prevented the reduction in nitric oxide (NO) levels observed in hypertensive animals. This suggests a decrease in the systemic oxidative stress and a higher availability of NO induced by LC in a similar way to captopril's effects, which could be relevant in the management of arterial hypertension eventually.

L-carnitine and taurine synergistically inhibit the proliferation and osteoblastic differentiation of vascular smooth muscle cells

AIM

To investigate the synergistic action of L-carnitine (LC) and taurine (TAU) on the proliferation and osteoblastic differentiation of vascular smooth muscle cells (VSMCs).

METHODS

DNA and protein synthesis of VSMCs were assessed using scintillation counting. Alkaline phosphatase (ALP) activity and calcium content were determined to investigate the effects of LC and TAU on the osteoblastic differentiation and mineralization of VSMCs. TAU uptake by VSMCs was assayed. RNA interference was used to down-regulate the expression of the TAU transporter (TAUT) in rat VSMCs.

RESULTS

LC and TAU synergistically inhibited the proliferation and beta-glycerophosphate (beta-GP)-induced osteoblastic differentiation of VSMCs as evidenced by the decreased [(3)H]thymidine incorporation, ALP activity and calcium deposition. Furthermore, LC stimulated the TAU uptake and TAUT expression in VSMCs. Suppression of TAUT with short hairpin RNA (shRNA) abolished the synergistic action of LC and TAU in VSMCs.

CONCLUSION

The synergistic inhibitory action of LC and TAU on the proliferation and osteoblastic differentiation of VSMCs is attributable to the up-regulation of TAUT expression and TAU uptake by LC.

Comparative effects of captopril and l-carnitine on blood pressure and antioxidant enzyme gene expression in the heart of spontaneously hypertensive rats

It has been shown that oxidative stress is involved in the pathogenesis of arterial hypertension. The aim of this work was to study and compare the molecular mechanisms of the antioxidant properties of l-carnitine and captopril in spontaneously hypertensive rats (SHR). Antioxidant enzyme activity/regulation (glutathione peroxidase, glutathione reductase and superoxide dismutase) was measured in the erythrocytes and hearts of SHR. The molecular expression of endothelial nitric oxide synthase (eNOS), NADPH oxidase, angiotensin converting enzyme (ACE), angiotensin II type I receptor (AT(1) receptor) and NF-kappaB/IkappaB system was also measured in the hearts of these animals. Both l-carnitine and captopril augmented the antioxidant defense capacity in SHRs. This effect was mediated by an upregulation of antioxidant enzymes, an increase in the plasma total antioxidant capacity and a reduction of lipid peroxidation and superoxide anion production in the heart. The administration of both compounds to hypertensive animals also produced an upregulation of eNOS and a normalization of ACE, angiotensin AT(1) receptor, and the NF-kappaB/IkappaB system expression. In addition, captopril reduced the arterial blood pressure and the relative heart weights back to control values, whereas l-carnitine caused only a partial reduction of blood pressure values and did not alter the cardiac hypertrophy found in SHRs. In conclusion, we have found that l-carnitine and captopril have a similar antioxidant effect in the hearts of hypertensive rats. The molecular regulation of antioxidant enzymes through an inhibition of the renin-angiotensin system and a modulation of the NF-kappaB/IkappaB system seems to be responsible for this antioxidant effect.

The role of inflammatory markers in the cardioprotective effect of L-carnitine in L-NAME-induced hypertension

BACKGROUND

The mechanism(s) underlying the effects of L-carnitine (beta-hydroxy-gamma-N-trimethylammonium-butyrate; LC) in cardiovascular diseases are not well clarified. Previous studies have demonstrated that oxidative stress and inflammation contribute to arterial hypertension, and antioxidant and/or anti-inflammatory therapies have been proposed. We hypothesized that LC might attenuate the hypertensive status through an inhibition of inflammation process.

METHODS

Heart mRNA expression and plasma levels of inflammatory markers, interleukin-1 beta (IL-1 beta), interleukin-6 (IL-6), and tumor necrosis factor-alpha (TNF-alpha), were measured in rats that were made hypertensive with N(omega)-nitro-L-arginine methyl ester (L-NAME) and subjected to a simultaneous administration of LC. To clarify the role of the renin-angiotensin system (RAS) in this effect of LC, the activity and expression of angiotensin I-converting enzyme (ACE) as well as the expression of angiotensin II type I receptor (AT1R) in the heart were also determined.

RESULTS

LC produced a significant, but not complete, reduction of blood pressure in L-NAME-treated rats. Plasma levels and heart expression of IL-1 beta, IL-6, and TNF-alpha showed an increase in the L-NAME group, which was reversed by LC treatment. The plasma ACE activity was not modified between normotensive and hypertensive rats although LC treatment produced a reduction of these values in the latter. Finally, protein and mRNA expression of ACE and AT1R was enhanced in the heart of L-NAME-treated animals, and LC reversed these values.

CONCLUSIONS

The chronic administration of LC reduces blood pressure and attenuates the inflammatory process associated with arterial hypertension. LC might produce a partial inactivation in the RAS resulting in a reduction in the production and effects of angiotensin II.

The Influence of L-Carnitine on Oxidative Modification of LDL In Vitro

Owing to their structure and function, low-density lipoproteins (LDLs) are particularly susceptible to the oxidative modifications. To prevent against oxidative modification of LDL, L-carnitine, with endogenous small water-soluble quaternary amine possessing antioxidative properties, was used. The aim of this paper was to prove the in vitro influence of L-carnitine on the degree of oxidative modification of the lipid part (estimated by conjugated dienes, lipid hydroperoxides, and malondialdehyde levels) and the protein part (estimated by dityrosine and tryptophan levels) of LDL native and oxidized by cooper ions. The level of lipophylic LDL antioxidant-alpha-tocopherol was also measured.Oxidation of LDL by Cu(2+) enhanced lipid peroxidation. That was manifested by a statistically significant increase in the content of malondialdehyde (threefold), conjugated dienes (up to about 30%), and lipid hydroperoxides (up to about 50%). Cu(2+) ions were also the cause of oxidative modifications of the protein part of LDLs. It was manifested by a significant increase in dityrosine (by about 50%), whereas the level of tryptophan was significantly decreased threefold in relation to native LDL. Incubation of LDL with Cu(2+) ions also caused a significant sixfold decrease of alpha-tocopherol content in oxidized LDL. However, L-carnitine caused a decrease in the level of conjugated dienes, lipid hydroperoxide, malondialdehyde, and dityrosine by about 20% to 30%, and a significant increase (by about 50%) in the content of tryptophan in comparison with oxidative LDL and in a smaller degree significant changes with native LDL. Additionally, L-carnitine caused a significant twofold increase in alpha-tocopherol content in oxidized LDL.The above results indicate that L-carnitine protects the lipid as well as protein part of LDL particles against oxidative modifications, and this natural antioxidant might be used to prevent against diseases of oxidative origin.

l-Carnitine increases liver α-tocopherol and lowers liver and plasma triglycerides in aging ovariectomized rats

The objective of this study was to determine whether dietary L-carnitine can influence the status of alpha-tocopherol, retinol and selected lipid parameters in aging ovariectomized rats, an animal model for the menopausal state. Fourteen Fisher-344 female rats 18 months old were acclimated for 4 weeks and ovarectomized. Seven rats per treatment were assigned to either a control group fed ad libitum AIN-93M diet or a carnitine group fed the same diet supplemented with L-carnitine. After an 8-week feeding period, blood and selected tissues were taken for analyses. No differences were noted in food intake, body weight, or organ weights due to L-carnitine. Dietary carnitine significantly increased liver alpha-tocopherol and tended to increase plasma alpha-tocopherol (P<.09). No changes in alpha-tocopherol were observed in other tissues including the brain, lungs and retroperitoneal fat. Retinol levels in plasma and tissues were not affected by supplemental L-carnitine. Significant decreases in liver and plasma triglyceride (TG) levels were noted, suggesting increased utilization of fatty acids. No differences were observed in the fatty acid profile of tissues. The results provide evidence that dietary supplementation of L-carnitine enhances the alpha-tocopherol status and improves the utilization of fat leading to lowering of the liver and plasma levels of TG in aging ovariectomized rats. Whether supplemental L-carnitine may be of benefit to postmenopausal women in lowering plasma TG and improving the antioxidant status remains to be studied.

l-Carnitine attenuates oxidative stress in hypertensive rats

The present study aimed to investigate whether l-carnitine (LC) protects the vascular endothelium and tissues against oxidative damage in hypertension. Antioxidant enzyme activities, glutathione and lipid peroxidation were measured in the liver and heart of spontaneously hypertensive rats (SHR) and Wistar-Kyoto (WKY) rats. Nitrite and nitrate levels and total antioxidant status (TAS) were evaluated in plasma, and the expression of endothelial nitric oxide synthase (eNOS) and p22phox subunit of NAD(P)H oxidase was determined in aorta. Glutathione peroxidase activity was lower in SHR than in WKY rats, and LC increased this activity in SHR up to values close to those observed in normotensive animals. Glutathione reductase and catalase activities, which were higher in SHR, tended to increase after LC treatment. No differences were found in the activity of superoxide dismutase among any animal group. The ratio between reduced and oxidized glutathione and the levels of lipid peroxidation were respectively decreased and increased in hypertensive rats, and both parameters were normalized after the treatment. Similarly, LC was able to reverse the reduced plasma nitrite and nitrate levels and TAS observed in SHR. We found no alterations in the expression of aortic eNOS among any group; however, p22phox mRNA levels showed an increase in SHR that was reversed by LC. In conclusion, chronic administration of LC leads to an increase in hepatic and cardiac antioxidant defense and a reduction in the systemic oxidative process in SHR. Therefore, LC might increase NO availability in SHR aorta by a reduction in superoxide anion production.

L-Carnitine inhibits protein glycation in vitro and in vivo: evidence for a role in diabetic management

Glycation-initiated changes in tissue proteins are suggested to play an important role in the development of diabetes-related pathological changes. The purpose of this study was to examine the anti-glycating effect of L-carnitine (CA) in vivo in the high-fructose diet-fed rat and to determine the potential of CA to inhibit in vitro glycation. Additionally the glucose-disposal efficiency of CA in the rat diaphragm was investigated. High-fructose diet (60 g/100 g diet)-fed rats were treated with CA (300 mg/kg/day i.p.) for 60 days. The effect of CA on glucose, fructose and fructosamine in plasma, methyl glyoxal and glycated haemoglobin in whole blood and skin and tail tendon collagen glycation were determined. The inhibitory effect of CA on the glycation of bovine serum albumin in vitro was compared with that of aminoguanidine (AG), a known antiglycation agent. Glucose utilisation induced by insulin in the control rat diaphragm was monitored in the presence and absence of CA. High-fructose feeding induced hyperglycaemia and glycation of haemoglobin and skin and tail tendon collagen. In CA-administered fructose-fed rats glycation was significantly reduced. In vitro glycation and accumulation of advanced glycation end products were mitigated by CA. CA was more effective than AG in inhibiting glycation in vitro. CA also enhanced the utilisation of glucose in the rat diaphragm. The findings of the study reveal that CA not only has antiglycation effect but also enhances glucose disposal in the rat diaphragm. These findings provide evidence for the therapeutic utility of CA in diabetes and associated complications.

Links between nutrition, drug abuse, and the metabolic syndrome

Nutritional deficiency in combination with drug abuse may increase risk of developing the metabolic syndrome by augmenting cell damage, excitotoxicity, reducing energy production, and lowering the antioxidant potential of the cells. We have reviewed here the following points: effects of drugs of abuse on nutrition and brain metabolism; effects of nutrition on actions of the drugs of abuse; drug abuse and probability of developing metabolic syndrome; role of genetic vulnerability in nutrition/drug abuse and brain damage; and the role of neuroprotective supplements in drug abuse. Nutrition education is an essential component of substance abuse treatment programs and can enhance substance abuse treatment outcomes. The strategies available, in particular the nutritional approach to protect the drug abusers from the metabolic syndrome and other diseases are discussed.

Effect of l-carnitine supplementation on xenobiotic-metabolizing hepatic enzymes exposed to methanol

The study aimed to evaluate the effect of L-carnitine on hepatic cytochrome P450-dependent monooxygenases exposed to methanol. Male Spraque-Dawley rats were given methanol (1/4 LD50 and 1/2 LD50) together with L-carnitine (1g/kg body weight). The parameters of microsome electron transport chains I and II and the levels of CYP2E1, CYP2B1/2 and CYP1A2 were measured 8, 12, 24, 48, 72 and 96 h after exposure. L-carnitine did not affect cytochrome P450 but it significantly increased at 72 and 96 h NADPH-cytochrome P450 reductase. It stimulated cytochrome b5 at 48 and 96 h and NADH-cytochrome b5 reductase activity at 12, 72 and 96 h. Methanol, especially the lower dose, inhibited cytochrome P450 after 48 h, but the higher methanol dose inhibited NADH-cytochrome b5 reductase activity in this time. L-carnitine, combined with the lower dose of methanol, stimulated NADPH-cytochrome P450 reductase after 48 h and cytochrome b5 and NADH-cytochrome b5 reductase over the whole period of observation. L-carnitine stimulated CYP2B1/2 but not CYP2E1 and CYP1A2. Methanol stimulated CYP2E1 at 24 h, but CYP1A2 at 96 h in the studied doses. CYP2B1/2 was induced by the lower dose of methanol at 24 h but by the higher one at 96 h. When given together, L-carnitine and methanol (1/2 LD50) significantly stimulated CYP2E1 up to 170% at 24 h and 145% at 96 h.

Mitochondrial dysfunction in NASH: causes, consequences and possible means to prevent it

Calorie-enriched diet and lack of exercise are causing a worldwide surge of obesity, insulin resistance and lipid accretion in liver (i.e. hepatic steatosis), which can lead to steatohepatitis. Steatosis and nonalcoholic steatohepatitis (NASH) can also be induced by drugs such as amiodarone, tamoxifen and some antiretroviral drugs, including stavudine and zidovudine. There is accumulating evidence that mitochondrial dysfunction (more particularly respiratory chain deficiency) plays a key role in the physiopathology of NASH whatever its initial cause. In contrast, the mitochondrial beta-oxidation of fatty acids can be either increased (as in insulin resistance-associated NASH) or decreased (as in drug-induced NASH). However, in both circumstances, generation of reactive oxygen species (ROS) by the damaged respiratory chain can be augmented. ROS generation in an environment enriched in lipids in turn induces lipid peroxidation which releases highly reactive aldehydic derivatives (e.g. malondialdehyde) that have diverse detrimental effects on hepatocytes and other hepatic cells. In hepatocytes, ROS, reactive nitrogen species and lipid peroxidation products further impair the respiratory chain, either directly or indirectly through oxidative damage to the mitochondrial genome. This consequently leads to the generation of more ROS and a vicious cycle occurs. Mitochondrial dysfunction can also lead to apoptosis or necrosis depending on the energy status of the cell. ROS and lipid peroxidation products also increase the generation of several cytokines (TNF-alpha, TGF-beta, Fas ligand) playing a key role in cell death, inflammation and fibrosis. Recent investigations have shown that some genetic polymorphisms can significantly increase the risk of steatohepatitis and that several drugs can prevent or even reverse NASH. Interestingly, most of these drugs could exert their beneficial effects by improving directly or indirectly mitochondrial function in liver. Finding a drug, which could fully prevent oxidative stress and mitochondrial dysfunction in NASH is a major challenge for the next decade.

Hsp70 accumulation and ultrastructural features of lung and liver induced by ethanol treatment with and without l-carnitine protection in rats

This study examined Hsp70 accumulation and the subcellular characteristics of liver and lung when exposed to ethanol (EtOH), with and without L-carnitine protection. Female Sprague-Dawley rats, 150-200 g body weight, were randomized into four groups: Control (CON), Alcohol (ALC), L-carnitine (CAR) and Alcohol-L-carnitine (ALC-CAR). EtOH was administered per os at a dose of 4 g/kg body weight (1 ml) daily for 4 weeks. Before alcohol intake, an oral dose of 500 mg/kg body weight of L-carnitine was also administered to the ALC-CAR group. The liver and lung samples were subjected to Hsp70 Western blot and ultrastructural analysis. The Hsp70 accumulation was higher in the liver than in the lung samples. Hepatic Hsp70 accumulation was similar for all groups in contrast to lung, where the Hsp70 accumulation depends on the group studied. The ultrastructural results showed lung but not liver alterations, evidencing a stressful condition and subsequent cellular injury for lung tissue but not for liver. The ALC-CAR group showed less lung damage than the non-protected group and resembles the general appearance of the CON and CAR groups. EtOH intoxication induced differential cellular response in liver and lung in a dose and tissue dependent manner. L-carnitine seems to reduce lung EtOH-induced subcellular damage. The promotion of heat shock or stress proteins might represent one of the mechanisms involved that need to be further investigated.

Placebo-controlled double-blind randomized trial on the use of L-carnitine, L-acetylcarnitine, or combined L-carnitine and L-acetylcarnitine in men with idiopathic asthenozoospermia

OBJECTIVE

To evaluate the effectiveness of L-carnitine (LC) or L-acetyl-carnitine (LAC) or combined LC and LAC treatment in improving semen kinetic parameters and the total oxyradical scavenging capacity in semen.

DESIGN

Placebo-controlled, double-blind, randomized trial.

SETTING

Andrology unit, Department of Internal Medicine, Polytechnic University of Marche, Italy.

PATIENT(S)

Sixty infertile men, ages 20 to 40 years, with the following baseline sperm selection criteria: concentration > 20 x 10(6)/mL, sperm forward motility < 50%, and normal sperm morphology > 30%; 59 patients completed the study.

INTERVENTION(S)

Patients underwent a double-blind therapy of LC 3 g/d, LAC 3 g/d, a combination of LC 2 g/d and LAC 1 g/d, or placebo. The study design was 1 month of run in, 6 months of therapy or placebo, and 3 months of follow-up evaluation.

MAIN OUTCOME MEASURE(S)

Variations in semen parameters used for patient selection, and variations in total oxyradical scavenging capacity of the seminal fluid.

RESULT(S)

Sperm cell motility (total and forward, including kinetic features determined by computer-assisted sperm analysis) increased in patients to whom LAC was administered both alone or in combination with LC; combined LC + LAC therapy led to a significant improvement of straight progressive velocity after 3 months. The total oxyradical scavenging capacity of the semen toward hydroxyl and peroxyl radicals also increased and was positively correlated with the improvement of kinetic features. Patients with lower baseline values of motility and total oxyradical scavenging capacity of the seminal fluid had a significantly higher probability of responding to the treatment.

CONCLUSION(S)

The administration of LC and LAC is effective in increasing sperm kinetic features in patients affected by idiopathic asthenozoospemia and improves the total oxyradical scavenging capacity of the seminal fluid in the same population.

Antioxidant activity of propionyl-L-carnitine in liver and heart of spontaneously hypertensive rats

Oxidative stress plays an important role in arterial hypertension and propionyl-L-carnitine (PLC) has been found to protect cells from toxic reactive oxygen species. In this work, we have evaluated the antioxidant capacity of chronic PLC treatment in spontaneously hypertensive rats (SHR) by measuring the activity of antioxidant enzymes and the lipid peroxidation in liver and cardiac tissues. The activity of glutathione peroxidase was decreased in liver and cardiac tissues of SHR when compared with their normotensive controls, Wistar- Kyoto (WKY) rats, this alteration being prevented by PLC treatment. Glutathione reductase activity was increased in hypertensive rats and no effect was observed after the treatment. No significant changes in superoxide dismutase activity were observed among all experimental groups. Liver of hypertensive rats showed higher catalase activity than that of normotensive rats, and PLC enhanced this activity in both rat strains. Thiobarbituric acid reactive substances, determined as a measure of lipid peroxidation, were increased in SHR compared with WKY rats, and PLC treatment decreased these values not only in hypertensive rats but also in normotensive ones. The content of carnitine in serum, liver and heart was higher in PLC-treated rats, but PLC did not prevent the hypertension development in young SHR. In addition, triglyceride levels, which were lower in SHR than WKY rats, were reduced by chronic PLC treatment in both rat strains. These results demonstrate: i) the hypotriglyceridemic effect of PLC and ii) the antioxidant capacity of PLC in SHR and its beneficial use protecting tissues from hypertension-accompanying oxidative damage.

Dietary L-carnitine enhances the lymphatic absorption of fat and alpha-tocopherol in ovariectomized rats

This study was conducted to determine whether the feeding of dietary L-carnitine (CN) improves the intestinal absorption of fat and alpha-tocopherol (alphaTOH) in ovariectomized (OX) rats. OX adult rats were weight-matched and assigned to 2 groups fed a modified AIN-93G diet containing alphaTOH-stripped soybean oil without (-CN) or with (+CN) supplemental CN at 150 mg/kg diet. At 5 wk, each rat with a lymph cannula was infused intraduodenally at 3.0 mL/h with a lipid emulsion consisting of 565 micromol triolein labeled with (14)C ((14)C-OA), 3.6 micromol alphaTOH, and 396 micromol sodium taurocholate in 24 mL PBS buffer. Lymph was collected hourly for 8 h and analyzed for lipids. The lymphatic absorption of alphaTOH for 8 h in +CN rats (899 +/- 201 nmol) was higher (P < 0.05) than in -CN rats (587 +/- 92 nmol). The absorption of (14)C-OA in +CN rats (53.5 +/- 4.0% dose/8 h) also was increased (P < 0.05) compared with -CN rats (47.6 +/- 5.0% dose/8 h). Lymph flow did not differ between the groups. When bile was diverted but with infusion of sodium taurocholate, the lymphatic absorption of lipids did not differ. The present study provides evidence that dietary CN enhances the rates and amounts of lymphatic absorption of alphaTOH and fat in OX rats. Our findings suggest that dietary CN may influence the process of lipid packaging and absorption by the enterocyte in OX rats, and may explain in part the increased status of alphaTOH in CN-fed animals.

L-carnitine alleviates alcohol-induced liver damage in rats: role of tumour necrosis factor-alpha

AIMS

Excessive alcohol intake induces hepatic fatty infiltration, which has been suggested to sensitize the liver to further damage. To test this hypothesis, L-carnitine, a constitutional lipotropic compound, was administered to rats chronically treated with ethanol by liquid diet feeding for 10 weeks.

RESULTS

Ethanol administration caused marked steatosis, mild inflammation and elevated plasma alanine aminotransferase and tumour necrosis factor alpha (TNF-alpha) concentrations. Dietary supplementation with L-carnitine significantly reduced all these parameters as well as the hepatic concentration of thiobarbituric acid reactive substances, an indicator of lipid peroxidation products. Pretreatment with L-carnitine also significantly blunted ethanol-induced stimulation of TNF-alpha release by isolated Kupffer cells.

CONCLUSIONS

This study provides direct support for the notion that steatosis sensitizes the liver to further damage and suggests an involvement of TNF-alpha in this process.

L-carnitine treatment of anemia

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