The effects of carnitine supplementation on clinical characteristics of patients with non-alcoholic fatty liver disease: A systematic review and meta-analysis of randomized controlled trials

The effects of L-carnitine supplementation on cardiovascular risk factors in participants with impaired glucose tolerance and diabetes: a systematic review and dose-response meta-analysis

AIMS

L-carnitine plays a role related to cardiometabolic factors, but its effectiveness and safety in CVD are still unknown. We aim to assess the effect of L-carnitine supplementation on CVD risk factors.

METHODS

A systematic literature search was conducted in PubMed, Web of Science, and Scopus until October 2022. The main outcomes were lipid profiles, anthropometric parameters, insulin resistance, serum glucose levels, leptin, blood pressure, and inflammatory markers. The pooled weighted mean difference (WMD) was calculated using a random-effects model.

RESULTS

We included the 21 RCTs (n = 2900) with 21 effect sizes in this study. L-carnitine supplementation had a significant effect on TG (WMD = - 13.50 mg/dl, p = 0.039), LDL (WMD = - 12.66 mg/dl, p < 0.001), FBG (WMD = - 6.24 mg/dl, p = 0.001), HbA1c (WMD = -0.37%, p = 0.013) HOMA-IR (WMD = -0.72, p = 0.038 (, CRP (WMD = - 0.07 mg/dl, P = 0.037), TNF-α (WMD = - 1.39 pg/ml, p = 0.033), weight (WMD = - 1.58 kg, p = 0.001 (, BMI (WMD = - 0.28 kg/m2, p = 0.017(, BFP (WMD = - 1.83, p < 0.001) and leptin (WMD = - 2.21 ng/ml, p = 0.003 (in intervention, compared to the placebo group, in the pooled analysis.

CONCLUSIONS

This meta-analysis demonstrated that administration of L-carnitine in diabetic and glucose intolerance patients can significantly reduce TG, LDL-C, FBG, HbA1c, HOMA-IR, CRP, TNF-α, weight, BMI, BFP, and leptin levels. PROSPERO registration code: CRD42022366992.

Serum Metabolomics Uncovers the Mechanisms of Inulin in Preventing Non-Alcoholic Fatty Liver Disease

Inulin may be a promising therapeutic molecule for treating non-alcoholic fatty liver disease (NAFLD). However, the underlying mechanisms of its therapeutic activity remain unclear. To address this issue, a high-fat-diet-induced NAFLD mouse model was developed and treated with inulin. The NAFLD phenotype was evaluated via histopathological analysis and biochemical parameters, including serum levels of alanine aminotransferase, aspartate aminotransferase, liver triglycerides, etc. A serum metabolomics study was conducted using ultra-performance liquid chromatography coupled with tandem mass spectrometry. The results revealed that inulin mitigated NAFLD symptoms such as histopathological changes and liver cholesterol levels. Through the serum metabolomics study, 347 differential metabolites were identified between the model and control groups, and 139 differential metabolites were identified between the inulin and model groups. Additionally, 48 differential metabolites (such as phosphatidylserine, dihomo-γ-linolenic acid, L-carnitine, and 13-HODE) were identified as candidate targets of inulin and subjected to pathway enrichment analysis. The results revealed that these 48 differential metabolites were enriched in several metabolic pathways such as fatty acid biosynthesis and cardiolipin biosynthesis. Taken together, our results suggest that inulin might attenuate NAFLD partially by modulating 48 differential metabolites and their correlated metabolic pathways, constituting information that might help us find novel therapies for NAFLD.

Emerging drugs for the treatment of sarcopenia in cirrhosis of the liver

INTRODUCTION

Malnutrition and sarcopenia are common and impact the prognosis in patients with liver cirrhosis. The etiology is multifactorial and includes periods of reduced caloric intake, increased catabolism and direct molecular mechanisms that inhibit muscle synthesis. Although these conditions are widely acknowledged, and there is a growing interest in their diagnosis, robust evidence regarding the treatment and reversibility of these conditions is still lacking.

AREAS COVERED

We have explored the current evidence on the pharmacological treatment of sarcopenia in patients with cirrhosis. Additionally, we have searched for drugs already in use and ongoing trials for other chronic diseases.

EXPERT OPINION

The current guidelines recommend the use of a protein-adequate diet and moderate physical activity for treating sarcopenia in patients with cirrhosis. Currently, robust evidence is derived only from the supplementation of Branched-Chain Amino Acids, capable of increasing muscle mass and function. There are many drugs targeting various pathways that contribute to sarcopenia. However, evidence is sporadic and insufficient to suggest their use in clinical practice.Novel drugs specifically designed to enhance muscle mass and function should be developed. Finally, gender significantly influences the type of muscle alteration and therapeutic mechanisms; therefore, future studies should be designed taking gender differences into consideration.

The effects of L-carnitine supplementation on inflammatory and anti-inflammatory markers in adults: a systematic review and dose-response meta-analysis

L-carnitine supplementation may be beneficial in improving inflammatory conditions and reducing the level of inflammatory cytokines. Therefore, according to the finding of randomized controlled trials (RCTs), the systematic review and meta-analysis aimed to investigate the effect of L-carnitine supplementation on inflammation in adults. To obtain acceptable articles up to October 2022, a thorough search was conducted in databases including PubMed, ISI Web of Science, the Cochrane Library, and Scopus. A random-effects model was used to estimate the weighted mean difference (WMD). We included the 48 RCTs (n = 3255) with 51 effect sizes in this study. L-carnitine supplementation had a significant effect on C-reactive protein (CRP) (p < 0.001), interleukin-6 (IL-6) (p = 0.001), tumor necrosis factor-α (TNF-α) (p = 0.002), malondialdehyde (MDA) (p = 0.001), total antioxidant capacity (TAC) (p = 0.029), alanine transaminase (ALT) (p < 0.001), and aspartate transaminase (AST) (p < 0.001) in intervention, compared to the placebo group. Subgroup analyses showed that L-carnitine supplementation had a lowering effect on CRP and TNF-α in trial duration ≥ 12 weeks in type 2 diabetes and BMI ≥ 25 kg/m2. L-carnitine supplementation reduced ALT levels in overweight and normal BMI subjects at any trial dose and trial duration ≥ 12 weeks and reduced AST levels in overweight subjects and trial dose ≥ 2 g/day. This meta-analysis revealed that L-carnitine supplementation effectively reduces the inflammatory state by increasing the level of TAC and decreasing the levels of CRP, IL-6, TNF-α and MDA in the serum.

The efficacy of L-carnitine in patients with nonalcoholic steatohepatitis and concomitant obesity

BACKGROUND

In light of the high prevalence of nonalcoholic fatty liver disease and obesity, treatment options for nonalcoholic steatohepatitis are of particular interest. The purpose of the study is to assess the efficacy of L-carnitine and its effects on the functional state of the liver, as well as on lipid and carbohydrate metabolism in patients with nonalcoholic steatohepatitis and concomitant obesity.

METHODS

People in the control group followed a hypocaloric diet and received 1 tablet of simvastatin 20 mg once a day and 2 capsules of essential phospholipids 600 mg three times a day for 90 days. People in the experimental group followed a hypocaloric diet and received 1 tablet of simvastatin 20 mg once a day and L-carnitine 10 mL orally two times a day for 90 days.

RESULTS

L-carnitine normalized the blood lipid profile of subjects, as demonstrated by a significant decrease in the blood levels of total cholesterol, triglycerides, low-density lipoproteins, atherogenic index, and insulin resistance. The use of L-carnitine in patients with nonalcoholic steatohepatitis and concomitant obesity contributes to the steady reduction of the main clinical and biochemical symptoms of nonalcoholic steatohepatitis.

CONCLUSIONS

L-carnitine produces positive effects on the blood lipid profile and carbohydrate metabolism.

Efficacy and safety of carnitine supplementation on NAFLD: a systematic review and meta-analysis

BACKGROUND AND OBJECTIVE

The efficacy and safety of L-carnitine supplementation on non-alcoholic fatty liver disease (NAFLD) are unclear. This systematic review and meta-analysis aimed to assess the efficacy and safety of L-carnitine supplementation on NAFLD.

METHODS

We searched in four databases (PubMed, Embase, Cochrane Library, and Web of Science) from inception to 1 November 2022 (updated on March 20, 2023) for potentially relevant records without language restrictions. We collected information on the first author, publication year, country, setting, study design, population characteristics, duration of follow-up, outcome variables of interest, and sources of funding. We used a modified Cochrane risk of bias tool to assess the risk of bias, used GRADE to assess the certainty of evidence, and used the Credibility of Effect Modification Analyses (ICEMAN) tool to assess the credibility of any apparent subgroup effect.

RESULTS

This systematic review and meta-analysis included eight eligible randomized controlled trials (RCTs). Compared to placebo, low certainty evidence show that L-carnitine supplementation significantly changes (reduced) more in AST levels and ALT levels (MD: - 26.38, 95%CI: - 45.46 to - 7.30), and moderate certainty evidence show that L-carnitine supplementation significantly changes (reduced) more in HDL cholesterol levels (MD: 1.14, 95%CI: 0.21 to 2.07) and triglyceride levels (MD: - 6.92, 95%CI: - 13.82 to - 0.03). Moderate credibility of ICEMAN results shows that L-carnitine supplementation has no difference in changes of AST and ALT levels in younger ones (MD: 0.5, 95%CI: - 0.70 to 1.70) but has significant changes (reduced) in adults (MD: - 20.3, 95%CI: - 28.62 to - 12.28) compared to placebo.

CONCLUSION

L-carnitine supplementation may improve liver function and regulate triglyceride metabolism in patients with NAFLD, and with no significant adverse effects.

Mitochondrial carnitine palmitoyltransferase-II dysfunction: A possible novel mechanism for nonalcoholic fatty liver disease in hepatocarcinogenesis

Nonalcoholic fatty liver disease (NAFLD) or metabolic-associated fatty liver disease has been characterized by the lipid accumulation with injury of hepatocytes and has become one of the most common chronic liver diseases in the world. The complex mechanisms of NAFLD formation are still under identification. Carnitine palmitoyltransferase-II (CPT-II) on inner mitochondrial membrane (IMM) regulates long chain fatty acid β-oxidation, and its abnormality has had more and more attention paid to it by basic and clinical research in NAFLD. The sequences of its peptide chain and DNA nucleotides have been identified, and the catalytic activity of CPT-II is affected on its gene mutations, deficiency, enzymatic thermal instability, circulating carnitine level and so on. Recently, the CPT-II dysfunction has been discovered in models of liver lipid accumulation. Meanwhile, the malignant transformation of hepatocyte-related CD44⁺ stem T cell activation, high levels of tumor-related biomarkers (AFP, GPC3) and abnormal activation of Wnt3a expression as a key signal molecule of the Wnt/β-catenin pathway run parallel to the alterations of hepatocyte pathology. This review focuses on some of the progress of CPT-II inactivity on IMM with liver fatty accumulation as a possible novel pathogenesis for NAFLD in hepatocarcinogenesis.

Liver Lipidomics Analysis Revealed the Novel Ameliorative Mechanisms of L-Carnitine on High-Fat Diet-Induced NAFLD Mice

The beneficial effects of L-carnitine on non-alcoholic fatty liver disease (NAFLD) were revealed in previous reports. However, the underlying mechanisms remain unclear. In this study, we established a high fat diet (HFD)-induced NAFLD mice model and systematically explored the effects and mechanisms of dietary L-carnitine supplementation (0.2% to 4%) on NAFLD. A lipidomics approach was conducted to identify specific lipid species involved in the ameliorative roles of L-carnitine in NAFLD. Compared with a normal control group, the body weight, liver weight, concentrations of TG in the liver and serum AST and ALT levels were dramatically increased by HFD feeding (p < 0.05), accompanied with obvious liver damage and the activation of the hepatic TLR4/NF-κB/NLRP3 inflammatory pathway. L-carnitine treatment significantly improved these phenomena and exhibited a clear dose–response relationship. The results of a liver lipidomics analysis showed that a total of 12 classes and 145 lipid species were identified in the livers. Serious disorders in lipid profiles were noticed in the livers of the HFD-fed mice, such as an increased relative abundance of TG and a decreased relative abundance of PC, PE, PI, LPC, LPE, Cer and SM (p < 0.05). The relative contents of PC and PI were significantly increased and that of DG were decreased after the 4% L-carnitine intervention (p < 0.05). Moreover, we identified 47 important differential lipid species that notably separated the experimental groups based on VIP ≥ 1 and p < 0.05. The results of a pathway analysis showed that L-carnitine inhibited the glycerolipid metabolism pathway and activated the pathways of alpha-linolenic acid metabolism, glycerophospholipid metabolism, sphingolipid metabolism and Glycosylphosphatidylinositol (GPI)-anchor biosynthesis. This study provides novel insights into the mechanisms of L-carnitine in attenuating NAFLD.

Effects of L-carnitine supplementation on glucolipid metabolism: a systematic review and meta-analysis

Background: L-carnitine supplementation has been utilized against glucolipid metabolism disruption. However, to the best of our knowledge, no meta-analysis process has analyzed the effects of L-carnitine supplementation on insulin resistance, fasting blood glucose, lipid metabolism, and liver enzyme levels in adults. Methods: Through the analysis and screening of 12 221 studies, 15 studies were selected from eligible trials for meta-analysis. Meta-analysis was performed in a random effect model with heterogeneity determined by I², and subgroup analyses were used to further identify the source of heterogeneity. Result: The results showed significant effects of L-carnitine on FBG (MD = -4.94 mg dL^-1, 95% CI: -7.07 to -2.82), insulin (MD = -0.99 μU mL^-1, 95% CI: -1.41 to -0.56), HOMA-IR (MD = -0.58, 95% CI: -0.77 to -0.38), TG (MD = -11.22 mg dL^-1, 95% CI: -19.21 to -3.22), TC (MD = -6.45 mg dL^-1, 95% CI: -9.95 to -2.95, LDLc (MD = -8.28 mg dL^-1, 95% CI: -11.08 to -5.47), and ALT (MD = -19.71 IU L^-1, 95% CI: -36.45 to -2.96). However, no significant effect of L-carnitine supplementation was observed in HDLc (MD = -0.77 mg dL^-1, 95% CI: -0.10 to -1.63) or AST (MD = -11.05 IU L^-1, 95% CI: -23.08 to 0.99). The duration of carnitine supplementation was negatively associated with mean differences in FBG, as assessed by meta-regression. Conclusion: The current meta-analysis revealed that L-carnitine may have favorable effects on glucolipid profile, especially insulin, FBG, HOMA-IR, TG, TC, LDLc, and ALT levels.

The Role of l-Carnitine in Mitochondria, Prevention of Metabolic Inflexibility and Disease Initiation

Mitochondria control cellular fate by various mechanisms and are key drivers of cellular metabolism. Although the main function of mitochondria is energy production, they are also involved in cellular detoxification, cellular stabilization, as well as control of ketogenesis and glucogenesis. Conditions like neurodegenerative disease, insulin resistance, endocrine imbalances, liver and kidney disease are intimately linked to metabolic disorders or inflexibility and to mitochondrial dysfunction. Mitochondrial dysfunction due to a relative lack of micronutrients and substrates is implicated in the development of many chronic diseases. l-carnitine is one of the key nutrients for proper mitochondrial function and is notable for its role in fatty acid oxidation. l-carnitine also plays a major part in protecting cellular membranes, preventing fatty acid accumulation, modulating ketogenesis and glucogenesis and in the elimination of toxic metabolites. l-carnitine deficiency has been observed in many diseases including organic acidurias, inborn errors of metabolism, endocrine imbalances, liver and kidney disease. The protective effects of micronutrients targeting mitochondria hold considerable promise for the management of age and metabolic related diseases. Preventing nutrient deficiencies like l-carnitine can be beneficial in maintaining metabolic flexibility via the optimization of mitochondrial function. This paper reviews the critical role of l-carnitine in mitochondrial function, metabolic flexibility and in other pathophysiological cellular mechanisms.

A Specifically Tailored Multistrain Probiotic and Micronutrient Mixture Affects Nonalcoholic Fatty Liver Disease-Related Markers in Patients with Obesity after Mini Gastric Bypass Surgery

BACKGROUND

Nonalcoholic fatty liver disease (NAFLD) is frequent among patients undergoing bariatric surgery. Beyond weight reduction, dietary supplements like micronutrients or probiotics that modify insulin resistance and lipotoxicity can be used to prevent or delay the progression of liver disease.

OBJECTIVES

We evaluated the effect of a dietary approach with a specifically tailored multistrain probiotic and micronutrient mixture compared with a basic care micronutrient supplement on serum alanine aminotransferase (ALAT) in obese patients after mini gastric bypass (MGB) surgery.

METHODS

This randomized, double-blind, controlled trial included 60 obese patients (age: 40 ± 10 y; BMI: 44 ± 3 kg/m²). Patients received a combination of specifically tailored multistrain probiotic powder and a specific micronutrient mixture (Pro+SM) or a control treatment consisting of a placebo and a basic care micronutrient mixture (Con+BM), with some micronutrients in lower doses than SM, for 12 wk after hospital discharge. Primary (serum ALAT) and secondary outcomes [serum aspartate aminotransferase (ASAT), fatty liver index, NAFLD fibrosis score, glucose metabolism, blood pressure (BP), heart rate] were assessed at week 0 and week 12. Data were analyzed using unpaired Student's t-tests or Mann-Whitney U tests to compare the changes due to each treatment to one another.

RESULTS

A total of 48 patients were included in the analyses. Changes in serum ALAT concentrations did not differ between groups. Compared with Con+BM, Pro+SM improved serum ASAT (difference: -8.0 U/L, 95% CI: -17.0, -4.0; P = 0.043), NAFLD fibrosis score (difference: -0.39; 95% CI: -0.78, 0; P = 0.048), serum triglycerides (difference: -22.8 mg/dL; 95% CI: -45.6, -0.1; P = 0.049) and the visceral adiposity index (difference: -0.70; 95% CI: -1.31, -0.08; P = 0.027).

CONCLUSION

Supplementation with a specifically tailored probiotic and micronutrient mixture improved NAFLD-related markers more than a basic micronutrient mixture in obese patients following MGB surgery. The trial was registered under clinicaltrials.gov as NCT03585413.

Role of Carnitine in Non-alcoholic Fatty Liver Disease and Other Related Diseases: An Update

Carnitine is an amino acid-derived substance that coordinates a wide range of biological processes. Such functions include transport of long-chain fatty acids from the cytoplasm to the mitochondrial matrix, regulation of acetyl-CoA/CoA, control of inter-organellar acyl traffic, and protection against oxidative stress. Recent studies have found that carnitine plays an important role in several diseases, including non-alcoholic fatty liver disease (NAFLD). However, its effect is still controversial, and its mechanism is not clear. Herein, this review provides current knowledge on the biological functions of carnitine, the “multiple hit” impact of carnitine on the NAFLD progression, and the downstream mechanisms. Based on the “multiple hit” hypothesis, carnitine inhibits β-oxidation, improves mitochondrial dysfunction, and reduces insulin resistance to ameliorate NAFLD. L-carnitine may have therapeutic role in liver diseases including non-alcoholic steatohepatitis, cirrhosis, hepatocellular carcinoma, alcoholic fatty liver disease, and viral hepatitis. We also discuss the prospects of L-carnitine supplementation as a therapeutic strategy in NAFLD and related diseases, and the factors limiting its widespread use.

Effect of l-carnitine supplementation on children and adolescents with nonalcoholic fatty liver disease (NAFLD): a randomized, triple-blind, placebo-controlled clinical trial

OBJECTIVES

Nonalcoholic fatty liver disease (NAFLD) is one of the most common liver diseases in the pediatric population at global level. Present study aims to assess the effect of l-carnitine supplementation on the NAFLD in children and adolescents.

METHODS

This randomized, triple-blind, placebo-controlled clinical trial was conducted in 2018-2019. Study was carried out in NAFLD participants (5-15 years). They were randomly assigned to receive either 50 mg/kg/day l-carnitine twice a day or identical placebo per day for three months. Liver enzymes and liver ultrasonography were assessed before and after the intervention. Both groups received similar consultation for lifestyle changes.

RESULTS

Overall, 55 participants completed the study, 30 patients in the l-carnitine group and 25 patients in placebo group. Mean changes of anthropometric measurements did not have significant differences between groups (p>0.05). No significant differences in the mean changes of aspartate aminotransferase (AST) (p=0.82) and alanine aminotransferase (ALT) (p=0.76) levels were documented between two groups. Based on within-group analysis, there were significant changes in AST and ALT levels before and after the intervention in both groups. The sonographic grades of fatty liver were not significantly different between two groups before (p=0.94) and after intervention (p=0.93).

CONCLUSIONS

In the present clinical trial, L-carnitine did not have significant effect on improving biochemical and sonographic markers of NAFLD in children and adolescents. Future studies are necessary to evaluate the applicability and efficacy of long-term l-carnitine supplementation to treatment of NAFLD in pediatric population.

TRIAL REGISTRATION

IRCT20170628034786N2.

Diabetes Mellitus and Cardiovascular Diseases: Nutraceutical Interventions Related to Caloric Restriction

Type 2 diabetes (T2DM) and cardiovascular disease (CVD) are closely associated and represent a key public health problem worldwide. An excess of adipose tissue, NAFLD, and gut dysbiosis establish a vicious circle that leads to chronic inflammation and oxidative stress. Caloric restriction (CR) is the most promising nutritional approach capable of improving cardiometabolic health. However, adherence to CR represents a barrier to patients and is the primary cause of therapeutic failure. To overcome this problem, many different nutraceutical strategies have been designed. Based on several data that have shown that CR action is mediated by AMPK/SIRT1 activation, several nutraceutical compounds capable of activating AMPK/SIRT1 signaling have been identified. In this review, we summarize recent data on the possible role of berberine, resveratrol, quercetin, and L-carnitine as CR-related nutrients. Additionally, we discuss the limitations related to the use of these nutrients in the management of T2DM and CVD.

Acetyl-L-Carnitine Ameliorates Metabolic and Endocrine Alterations in Women with PCOS: A Double-Blind Randomized Clinical Trial

INTRODUCTION

Polycystic ovary syndrome (PCOS) is a common endocrine-metabolic disorder and the main cause of infertility in women of reproductive age. Affected women suffer from insulin resistance and present with an intense stress response. Treatment with insulin sensitizers alone and in combination is used to ameliorate the signs and symptoms associated with the disease. This study was designed to compare the endocrine and metabolic parameters as well as subjective and objective measures of stress in women with PCOS before and after treatment with acetyl-L-carnitine (ALC) and metformin plus pioglitazone.

METHODS

A total of 147 women with PCOS were randomly assigned into two groups: the combo group (n = 72) received a combination of metformin, pioglitazone, and ALC (500 mg, 15 mg, and 1500 mg, respectively), twice daily; the Met + Pio group (n = 75) received metformin plus pioglitazone (500 mg, 15 mg, respectively) and placebo (citric acid plus calcium carbonate), twice daily for 12 weeks. Medications were discontinued when pregnancy was confirmed. The Perceived Stress Scale (PSS14) and Profile of Mood States (POMS) were employed as subjective measures of stress. The endocrine and metabolic functions of women with PCOS were assessed by measuring insulin, leutinizing hormone (LH), follicle-stimulating hormone (FSH), testosterone, and adiponectin levels in fasting blood samples. Insulin resistance was calculated by Homeostatic Model Assessment of Insulin Resistance (HOMA-IR).

RESULTS

Women at baseline had significantly elevated circulating concentration of insulin and low level of adiponectin. Treatment decreased insulin in both groups; however, the combo group showed a significant decrease (p = 0.001). Serum adiponectin level was raised significantly after treatment in both groups (p < 0.001). HOMA-IR also decreased in both groups (both p < 0.001). Testosterone, FSH, and LH significantly improved in both groups. LH also decreased in both groups; however, the change was significant only in the combo (metformin plus pioglitazone plus ALC) group (p = 0.013). Interestingly, there was a significant improvement in body circumference (p < 0.001) in the combo group. The PSS scores of the patients improved significantly (p < 0.001) in the combo group. Interestingly, regular menstrual cycles were found (97.2%) in the carnitine group, but in only 12.9% of the other group.

CONCLUSION

We conclude that addition of ALC therapy is superior to metformin plus pioglitazone in ameliorating insulin resistance, polycystic ovaries, menstrual irregularities, and hypoadiponectinemia in women with PCOS.

TRIAL REGISTRATION

Trial registration: clinicalTrial.gov NCT04113889. Registered 3 October, 2019. https://clinicaltrials.gov/ct2/show/NCT04113889 .

A Dose-Dependent Effect of Carnipure® Tartrate Supplementation on Endurance Capacity, Recovery, and Body Composition in an Exercise Rat Model

The objective of this work is to investigate the effects of Carnipure^® Tartrate (CT) supplementation with or without exercise on endurance capacity, recovery, and fatigue by assessing time to exhaustion as well as body weight and composition in rats. In addition, antioxidant capacity has been evaluated by measuring malondialdehyde (MDA) levels and antioxidant enzyme (superoxide dismutase, SOD; catalase, CAT; glutathioneperoxidase; GSHPx) activities. Fifty-six male Wistar rats were divided into eight groups including seven rats each. A control group did not receive CT nor exercise. Another control group received 200 mg/kg CT without exercise. The other six groups of rats went through an exercise regimen consisting of a 5-day training period with incremental exercise capacity, which was followed by 6 weeks of the run at 25 m/min for 45 min every day. CT was supplemented at 0, 25, 50, 100, 200, and 400 mg/kg per day during the 6 weeks. Rats submitted to exercise and supplemented with CT had a significant and dose-dependent increase in time to exhaustion and this effect seems to be independent of exercise (p < 0.05). Additionally, recovery and fatigue were improved, as shown by a significant and dose-dependent decrease in myoglobin and lactic acid plasma levels, which are two markers of muscle recovery. CT supplementation led to a dose-response decrease in body weight and visceral fat. These effects become significant at 200 and 400 mg/kg doses (p < 0.05). Additionally, the antioxidant capacity was improved, as shown by a significant and dose-dependent increase in SOD, CAT, and GSHPx. Serum MDA concentrations decreased in exercising rats with CT supplementation. CT supplementation led to a decrease in serum glucose, triglycerides, and total cholesterol concentrations with the lowest levels observed at 400 mg/kg dose (p < 0.05). These effects correlated with a significant dose-dependent increase in serum total L-carnitine, free L-carnitine, and acetyl-carnitine, which linked the observed efficacy to CT supplementation. These results demonstrate that CT supplementation during exercise provides benefits on exercise performance, recovery, and fatigue as well as improved the lipid profile and antioxidant capacity. The lowest dose leads to some of these effects seen in rats where 25 mg/kg corresponds to 250 mg/day as a human equivalent.

The Nutraceutical Value of Carnitine and Its Use in Dietary Supplements

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