Effective dosing of L-carnitine in the secondary prevention of cardiovascular disease: a systematic review and meta-analysis

Simultaneous determination of semi-essential nutrients taurine, l-carnitine and choline in infant formulas and adult/pediatric nutritional formulas by hydrophilic interaction liquid chromatography-electrospray ionization-tandem mass spectrometry

BACKGROUND

The nutritional intake of formula-fed newborns is often limited to a single source, so it must be supplemented with essential nutrients for the growth and proper development of infants. Taurine, l-carnitine, and choline are considered conditionally essential nutrients especially in newborns and infants.

RESULTS

In this work, a simple routine hydrophilic interaction liquid chromatography-electrospray ionization-tandem mass spectrometry (HILIC-ESI-MS/MS) method was developed and validated for the simultaneous determination of these semi-essential nutrients in infant and adult/pediatric milk formulas. The extraction recoveries were between 90% and 114%. Precision of the method offered relative standard deviation below 5% and 7% for intra-day and inter-day precision, respectively. The proposed method was successfully applied to quantification of taurine, l-carnitine, and choline in milk formula. The contents found were in good agreement with those provided on the product label for almost all samples.

CONCLUSION

In view of these results, it can be concluded that the developed method can be a useful approach for the simultaneous determination of taurine, l-carnitine and choline in powdered milk samples, so it can be useful in the routine quality control of this kind of samples. © 2024 The Author(s). Journal of The Science of Food and Agriculture published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

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.

Toxicological Analysis in Tissues Following Exhumation More Than Two Years after Death (948 Days): A Forensic Perspective in a Fatal Case

Exhumations are performed in accordance with a court order and are crucial instruments in the investigation of death allegations. When a death is thought to be the result of drug misuse, pharmaceutical overdose, or pesticide poisoning, this process may be used on human remains. However, after a protracted postmortem interval (PMI), it might be difficult to detect the cause of death by looking at an exhumed corpse. The following case report reveals problems associated with postmortem drug concentration changes following exhumation more than two years after death. A 31-year-old man was found dead in a prison cell. Onan inspection of the place, two blister packs, one with a tablet and the other empty, were taken and kept by the police officers. The evening before, the deceased would have taken cetirizine and food supplements consisting of carnitine-creatine tablets. No relevant autopsy findings have been observed. The toxicological analysis was performed by gas chromatography coupled to mass spectrometry and was negative for substances of abuse. Proteomic analysis was positive for creatine detection and negative for other drugs (clarithromycin, fenofibrate, and cetirizine). The presented case shows the methods, the findings, and the limitations of toxicological analysis in an exhumation case with a long postmortem interval (PMI).

Biomedical role of L-carnitine in several organ systems, cellular tissues, and COVID-19

Carnitine is a conditionally necessary vitamin that aids in energy creation and fatty acid metabolism. Its bioavailability is higher in vegetarians than in meat-eaters. Deficits in carnitine transporters occur because of genetic mutations or in conjunction with other illnesses. Carnitine shortage can arise in health issues and diseases-including hypoglycaemia, heart disease, starvation, cirrhosis, and ageing-because of abnormalities in carnitine control. The physiologically active form of L-carnitine supports immunological function in diabetic patients. Carnitine has been demonstrated to be effective in the treatment of Alzheimer's disease, several painful neuropathies, and other conditions. It has been used as a dietary supplement for the treatment of heart disease, and it also aids in the treatment of obesity and reduces blood glucose levels. Therefore, L-carnitine shows the potential to eliminate the influences of fatigue in COVID-19, and its consumption is recommended in future clinical trials to estimate its efficacy and safety. This review focused on carnitine and its effect on tissues, covering the biosynthesis, metabolism, bioavailability, biological actions, and its effects on various body systems and COVID-19.

Dietary precursors and cardiovascular disease: A Mendelian randomization study

Background

The Dietary precursor has been identified as a contributor in the development of cardiovascular disease. However, it is inconsistent if dietary precursors could affect the process of cardiovascular disease.

Methods

Here we performed Mendelian randomization (MR) analysis of the data from genome-wide association study of European ancestry to evaluate the independent effects of three dietary precursors on cardiovascular disease (CVD), myocardial infarction (MI), heart failure (HF), atrial fibrillation (AF), and valvular disease (VHD). Inverse variance weighting method was used for the MR estimation. Sensitivity was determined by MR-PRESSO analysis, weighted median analysis, MR-Egger analysis, and Leave-one-out analysis.

Results

We found that elevated choline level had a causal relationship with VHD [odds ratio (OR) = 1.087, 95% confidence interval (CI), 1.003-1.178, P = 0.041] and MI (OR = 1.250, 95% CI, 1.041-1.501, P = 0.017) by single-variable MR analysis. Furthermore, elevated carnitine level was associated with MI (OR = 5.007, 95% CI, 1.693-14.808, P = 0.004) and HF (OR = 2.176, 95% CI, 1.252-3.780, P = 0.006) risk. In addition, elevated phosphatidylcholine level can increase the risk of MI (OR = 1.197, 95% CI, 1.026-1.397, P = 0.022).

Conclusion

Our data show that choline increases VHD or MI risk, carnitine increases the risk of MI or HF, and phosphatidylcholine increases HF risk. These findings suggest the possibility that decrease in choline level in circulation may be able to reduce overall VHD or MI risk, reduce in carnitine level could be decrease MI and HF risks as well as decrease in phosphatidylcholine could reduce MI risk.

Gut microbiota production of trimethyl-5-aminovaleric acid reduces fatty acid oxidation and accelerates cardiac hypertrophy

Numerous studies found intestinal microbiota alterations which are thought to affect the development of various diseases through the production of gut-derived metabolites. However, the specific metabolites and their pathophysiological contribution to cardiac hypertrophy or heart failure progression still remain unclear. N,N,N-trimethyl-5-aminovaleric acid (TMAVA), derived from trimethyllysine through the gut microbiota, was elevated with gradually increased risk of cardiac mortality and transplantation in a prospective heart failure cohort (n = 1647). TMAVA treatment aggravated cardiac hypertrophy and dysfunction in high-fat diet-fed mice. Decreased fatty acid oxidation (FAO) is a hallmark of metabolic reprogramming in the diseased heart and contributes to impaired myocardial energetics and contractile dysfunction. Proteomics uncovered that TMAVA disturbed cardiac energy metabolism, leading to inhibition of FAO and myocardial lipid accumulation. TMAVA treatment altered mitochondrial ultrastructure, respiration and FAO and inhibited carnitine metabolism. Mice with γ-butyrobetaine hydroxylase (BBOX) deficiency displayed a similar cardiac hypertrophy phenotype, indicating that TMAVA functions through BBOX. Finally, exogenous carnitine supplementation reversed TMAVA induced cardiac hypertrophy. These data suggest that the gut microbiota-derived TMAVA is a key determinant for the development of cardiac hypertrophy through inhibition of carnitine synthesis and subsequent FAO.

Intestinal microbiota alterations may affect heart function through the production of gut-derived metabolites. Here the authors found that gut microbiota-derived TMAVA is a key determinant for the development of cardiac hypertrophy through inhibition of carnitine synthesis and subsequent fatty acid oxidation.

Carnitine deficiency among hospitalized pediatric patients: A retrospective study of critically ill patients receiving extracorporeal membrane oxygenation therapy

Background

The metabolic demands associated with critical illness place patients at risk for nutrition deficits. Carnitine is a small molecule essential for fatty acid oxidation and gluconeogenesis. Secondary carnitine deficiency can have clinically significant complications and has been observed anecdotally in patients receiving extracorporeal membrane oxygenation (ECMO) therapy at our institution. Guidelines for monitoring and supplementing carnitine are lacking. This retrospective study determined whether critically ill pediatric patients receiving ECMO have an increased risk of carnitine deficiency.

Methods

Acylcarnitine analysis was performed on residual specimens from patients who received ECMO therapy. The control data were a convenience sample gathered by chart review of patients who had been tested for carnitine during a hospitalization.

Results

Acylcarnitines were measured in 217 non‐ECMO patients and 81 ECMO patients. Carnitine deficiency, based on age‐specific reference ranges, was observed in 41% of ECMO cases compared with 21% of non‐ECMO cases. Multivariable analysis of age‐matched patients identified that the odds of carnitine deficiency were significantly lower among patients on the floor compared with ECMO patients (odds ratio, 0.21; 95% CI, 0.10–0.44). Age‐specific frequency of qualitative carnitine deficiency ranged from 15% (patients >5 years old) to 56% (patients 1 week to 1 month old) in ECMO patients and 15% (patients >5 years old) to 34% (patients 1–5 years old) in non‐ECMO patients.

Conclusion

In this study, ECMO patients were carnitine deficient more frequently compared with other inpatients, with the highest rates of deficiency among ECMO patients between 1 week and 1 month old.

Assessing the antioxidant and metabolic effect of an alpha-lipoic acid and acetyl-L-carnitine nutraceutical

Personalized nutrition (PN) is seen as a potentially effective and affordable strategy for the prevention of non-communicable diseases (NCDs). In this study we aimed to evaluate the antioxidant and metabolic effect of a dietary supplement based on alpha-lipoic acid (ALA) and acetyl-L-carnitine (ALC) in order to include this product in a novel PN service. The antioxidant properties of the commercial nutraceutical were investigated at physiological conditions (through in vitro digestion) and at mitochondrial conditions. The metabolic activity was assessed in a human pilot study using a Gas Chromatography-Mass Spectrometry (GC-MS) methodology in dried urine samples. The nutraceutical exerted an elevated antiradical activity and reducing capacity, especially at mitochondrial conditions, after in vitro digestion. This increase in mitochondrial activity was also evidenced in vivo by a significant increase in the urinary phosphate concentration (p ​= ​0.004). As pro-oxidant effect was reached with the concentration of 4 capsules, 2 capsules at the same time could be a reasonable dose. No adverse effects were recorded in vivo with this dose. Thus, although its metabolic effect was not so conclusive, ALA ​+ ​ALC combination might be beneficial as a dietary supplement for the prevention of the oxidative stress and an interesting dietary supplement to consider in large scale studies.

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The nutritional supplement showed a high in vitro antioxidant-reducing capacity.

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The antioxidant capacity increase after digestion in contrast to other antioxidants.

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A pro-oxidant effect was reached with the concentration of 4 capsules.

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2 capsules at the same time are safe in humans and may exert some metabolic changes.

Gut microbiota and cardiovascular diseases axis: a review

Gut microbiota, a term that includes microorganisms present in the gastrointestinal tract, has become very attractive lately due to its propensity to act as a virtual organ with endocrine functions, generating various bio-active metabolites, while playing an important role in human health and diseases, including cardiovascular diseases (CVDs). Focusing on the latter field, gastrointestinal dysbiosis, that is the imbalance in the gut microbiota composition, has been linked to various pathologies such as hypertension, atherosclerosis, myocardial infarction and heart failure. Several pathways were demonstrated to play a role in the complex and intertwined association between the gut microbiota and host, including metabolic endotoxemia, alteration of pattern recognition receptors and short-chain fatty acids, uremic toxins, bile acids and trimethylamine-N-oxide levels, leading to CVDs. Understanding these pathways can allow to identifying metabolites that could be useful predictors for detecting incipient CVDs stages and potential therapeutic targets. In this review, we summarize the pathways associating the gut microbiota with CVDs.

Nutraceutical, Dietary, and Lifestyle Options for Prevention and Treatment of Ventricular Hypertrophy and Heart Failure

Although well documented drug therapies are available for the management of ventricular hypertrophy (VH) and heart failure (HF), most patients nonetheless experience a downhill course, and further therapeutic measures are needed. Nutraceutical, dietary, and lifestyle measures may have particular merit in this regard, as they are currently available, relatively safe and inexpensive, and can lend themselves to primary prevention as well. A consideration of the pathogenic mechanisms underlying the VH/HF syndrome suggests that measures which control oxidative and endoplasmic reticulum (ER) stress, that support effective nitric oxide and hydrogen sulfide bioactivity, that prevent a reduction in cardiomyocyte pH, and that boost the production of protective hormones, such as fibroblast growth factor 21 (FGF21), while suppressing fibroblast growth factor 23 (FGF23) and marinobufagenin, may have utility for preventing and controlling this syndrome. Agents considered in this essay include phycocyanobilin, N-acetylcysteine, lipoic acid, ferulic acid, zinc, selenium, ubiquinol, astaxanthin, melatonin, tauroursodeoxycholic acid, berberine, citrulline, high-dose folate, cocoa flavanols, hawthorn extract, dietary nitrate, high-dose biotin, soy isoflavones, taurine, carnitine, magnesium orotate, EPA-rich fish oil, glycine, and copper. The potential advantages of whole-food plant-based diets, moderation in salt intake, avoidance of phosphate additives, and regular exercise training and sauna sessions are also discussed. There should be considerable scope for the development of functional foods and supplements which make it more convenient and affordable for patients to consume complementary combinations of the agents discussed here. Research Strategy: Key word searching of PubMed was employed to locate the research papers whose findings are cited in this essay.

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.

Characterization of TMAO productivity from carnitine challenge facilitates personalized nutrition and microbiome signatures discovery

The capability of gut microbiota in degrading foods and drugs administered orally can result in diversified efficacies and toxicity interpersonally and cause significant impact on human health. Production of atherogenic trimethylamine N-oxide (TMAO) from carnitine is a gut microbiota-directed pathway and varies widely among individuals. Here, we demonstrated a personalized TMAO formation and carnitine bioavailability from carnitine supplements by differentiating individual TMAO productivities with a recently developed oral carnitine challenge test (OCCT). By exploring gut microbiome in subjects characterized by TMAO producer phenotypes, we identified 39 operational taxonomy units that were highly correlated to TMAO productivity, including Emergencia timonensis, which has been recently discovered to convert γ-butyrobetaine to TMA in vitro. A microbiome-based random forest classifier was therefore constructed to predict the TMAO producer phenotype (AUROC = 0.81) which was then validated with an external cohort (AUROC = 0.80). A novel bacterium called Ihubacter massiliensis was also discovered to be a key microbe for TMA/TMAO production by using an OCCT-based humanized gnotobiotic mice model. Simply combining the presence of E. timonensis and I. massiliensis could account for 43% of high TMAO producers with 97% specificity. Collectively, this human gut microbiota phenotype-directed approach offers potential for developing precision medicine and provides insights into translational research. Video Abstract.

L-carnitine exerts a nutrigenomic effect via direct modulation of nuclear receptor signaling in adipocytes, hepatocytes and SKMC, demonstrating its nutritional impact

L-carnitine is an indispensable metabolite facilitating the transport of fatty acids into the mitochondrial matrix and has been previously postulated to exert a nutrigenomic effect. However, the underlying molecular mechanisms remain mostly unclear. We hypothesized that L-carnitine interacts with nuclear receptors involved in metabolic regulation, thereby modulating downstream targets of cellular metabolism. Therefore, we investigated the effect of L-carnitine supplementation on protein activity, mRNA expression, and binding affinities of nuclear receptors as well as mRNA expression of downstream targets in skeletal muscle cells, hepatocytes, and differentiated adipocytes. L-carnitine supplementation to hepatocytes increased the protein activity of multiple nuclear receptors (RAR, RXR, VDR, PPAR, HNF4, ER, LXR). Diverging effects on the mRNA expression of PPAR-α, PPAR-δ, PPAR-γ, RAR-β, LXR-α, and RXR-α were observed in adipocytes, hepatocytes, and skeletal muscle cells. mRNA levels of PPAR-α, a key regulator of lipolysis and β-oxidation, were significantly upregulated, emphasizing a role of L-carnitine as a promoter of lipid catabolism. L-carnitine administration to hepatocytes modulated the transcription of key nuclear receptor target genes, including ALDH1A1, a promoter of adipogenesis, and OGT, a contributor to insulin resistance. Electrophoretic mobility shift assays proved L-carnitine to increase binding affinities of nuclear receptors to their promoter target sequences, suggesting a molecular mechanism for the observed transcriptional modulation. Overall, these findings indicate that L-carnitine modulates the activity and expression of nuclear receptors, thereby promoting lipolytic gene expression and decreasing transcription of target genes linked to adipogenesis and insulin resistance.

Effect of L-carnitine on health-related quality of life in patients with liver cirrhosis

L-carnitine (4-N-trimethylammonium-3-hydroxybutyric acid) is the physiologically active form of carnitine and is a natural compound that has been shown to exhibit antioxidant activity. L-carnitine is used as a supplementary treatment in patients with cirrhosis with hepatic encephalopathy, hyperammonemia or muscle cramps. In the present study, the effect of L-carnitine supplementation on health-related quality of life in 30 patients with cirrhosis was prospectively examined. L-carnitine (1,800 mg/day) was administered orally for 6 months. To assess the effects of L-carnitine on chronic fatigue, patients filled out a self-report questionnaire regarding their physical and mental health. The levels of total and free carnitine, and acylcarnitine were found to be significantly higher 1, 3 and 6 months after therapy initiation compared with before treatment. Serum albumin levels were significantly increased 3 and 6 months after initiation of therapy. L-carnitine supplementation significantly increased the BAP/d-ROM ratio, a marker of antioxidant status in patients with cirrhosis. Changes in serum carnitine concentrations were positively correlated with changes in serum albumin levels (R²=0.369; P=0.012), but not with changes in serum ammonia levels (R²= 0.005; P=0.78). Total and mental health scores improved significantly, and physical scores improved marginally 3 and 6 months after initiation of L-carnitine. These findings may be attributed to the enhanced serum albumin levels and oxidative stress rather than the reduced serum ammonia levels. Based on these results, it is suggested that L-carnitine can potentially alleviate chronic fatigue, along with the increased BAP/d-ROM ratio, which were involved in increased oxidative stress in patients with cirrhosis. The specific mechanisms by which L-carnitine ameliorates chronic fatigue is not fully understood and requires further investigation.

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

Background

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

Methods

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

Results

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

Conclusion

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

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.

Scientific Papers and Patents on Substances with Unproven Effects

It is evident from reviewing scientific literature that the quality of argumentation in some areas of medical research has deteriorated during the last decades. Publication of a series of questionable reliability has continued without making references to the published criticism; examples are discussed in this review. Another tendency is that drugs without proven efficiency are advertised, corresponding products patented and marketed as evidence-based medications. Professional publications are required to register drugs and dietary supplements to obtain permissions for the practical use; and such papers appeared, sometimes being of questionable reliability. Several examples are discussed in this review when substances without proven effects were patented and introduced into practice being supported by publications of questionable reliability. Some of the topics are not entirely clear; and the arguments provided here can induce a constructive discussion.

Anti-Inflammatory and Antioxidant Effects of Acetyl-L-Carnitine on Atherosclerotic Rats

Background

The purpose of the present study was to evaluate the regulatory effects of acetyl-L-carnitine (ALCAR) on atherosclerosis in Wister rats and to explore its anti-atherosclerotic mechanism.

Material/Methods

We randomly divided 32 Wister rats into 4 groups: a normal diet group (control group, n=8), a normal diet+ALCAR group (ALCAR group, n=8), an atherosclerosis group (AS group, n=8), and an atherosclerosis+ALCAR group (AS+ALCAR group, n=8). The serum lipid distribution, oxidative stress, inflammatory factors and adiponectin (APN) in the blood, and heart and aortic tissues were determined using the standard assay kits, xanthine oxidase method, and ELISA, respectively. HE staining was performed to observe aortic pathology structure change, and the level of angiotensin II (AngII) in the aorta was assessed using radioimmunoassay. In addition, real-time quantitative PCR and Western blot analysis were applied to detect the expression of iNOS, IL-1β, TNF-α, and CRP in the aortic and heart tissues.

Results

Compared with the AS group, the levels of serum TC, TG, LDL, and VLDL in rats decreased significantly, while HDL level significantly increased in the AS+ALCAR group. ALCAR administration enhanced the SOD and GSH-Px activities and decreased MDA activity. APN level was significantly elevated in the AS group, but ALCAR had no significant effect on APN. Further, ALCAR reduced the expressions of inflammation factors TNF-α, IL-1β, iNOS, and CRP, and the concentration of AngII in serum, aortic, and heart tissues.

Conclusions

ALCAR can inhibit the expressions of inflammatory factors and antioxidation to suppress the development of atherosclerosis by adjusting blood lipid in the myocardium of AS rats.

Efficacy of l-carnitine supplementation for management of blood lipids: A systematic review and dose-response meta-analysis of randomized controlled trials

BACKGROUND AND AIM

l-carnitine has an important role in fatty acid metabolism and could therefore act as an adjuvant agent in the improvement of dyslipidemia. The purpose of present systematic review and meta-analysis was to critically assess the efficacy of l-carnitine supplementation on lipid profiles.

METHODS AND RESULTS

We performed a systematic search of all available randomized controlled trials (RCTs) in the following databases: Scopus, PubMed, ISI Web of Science, The Cochrane Library. Mean difference (MD) of any effect was calculated using a random-effects model. In total, there were 55 eligible RCTs included with 58 arms, and meta-analysis revealed that l-carnitine supplementation significantly reduced total cholesterol (TC) (56 arms-MD: -8.53 mg/dl, 95% CI: -13.46, -3.6, I²: 93%), low-density lipoprotein-cholesterol (LDL-C) (47 arms-MD: -5.48 mg/dl, 95% CI: -8.49, -2.47, I²: 94.5) and triglyceride (TG) (56 arms-MD: -9.44 mg/dl, 95% CI: -16.02, -2.87, I²: 91.8). It also increased high density lipoprotein-cholesterol (HDL-C) (51 arms-MD:1.64 mg/dl, 95% CI:0.54, 2.75, I²: 92.2). l-carnitine supplementation reduced TC in non-linear fashion based on dosage (r = 21.11). Meta-regression analysis indicated a linear relationship between dose of l-carnitine and absolute change in TC (p = 0.029) and LDL-C (p = 0.013). Subgroup analyses showed that l-carnitine supplementation did not change TC, LDL-C and TG in patients under hemodialysis treatment. Intravenous l-carnitine and lower doses (>2 g/day) had no effect on TC, LDL-C and triglycerides.

CONCLUSION

l-carnitine supplementation at doses above 2 g/d has favorable effects on patients' lipid profiles, but is modulated on participant health and route of administration.

Amelioration of TMAO through probiotics and its potential role in atherosclerosis

Atherosclerosis is a major cause of mortalities and morbidities worldwide. It is associated with hyperlipidemia and inflammation, and become chronic by triggering metabolites in different metabolic pathways. Disturbance in the human gut microbiota is now considered a critical factor in the atherosclerosis. Trimethylamine-N-oxide (TMAO) attracts attention and is regarded as a vital contributor in the development of atherosclerosis. TMAO is generated from its dietary precursors choline, carnitine, and phosphatidylcholine by gut microbiota into an intermediate compound known as trimethylamine (TMA), which is then oxidized into TMAO by hepatic flavin monooxygenases. The present review focus on advances in TMAO preventing strategies through probiotics, including, modulation of gut microbiome, metabolomics profile, miRNA, or probiotic antagonistic abilities. Furthermore, possible recommendations based on relevant literature have been presented, which could be applied in probiotics and atherosclerosis-preventing strategies.

UPLC-QTOF/MS-based metabolomics analysis of plasma reveals an effect of Xue-Fu-Zhu-Yu capsules on blood-stasis syndrome in CHD rats

ETHNOPHARMACOLOGICAL RELEVANCE

Blood-stasis syndrome (BSS) is a specific ZHENG type of coronary heart disease (CHD) in traditional Chinese medicine (TCM). The Xue-Fu-Zhu-Yu (XFZY) decoction is a common herbal formula that has been used for several centuries to treat BSS, but its mechanism has not been thoroughly elucidated to date.

AIM OF THE STUDY

In this study, serum lipid, blood haemorheology and metabolomics analyses were performed to depict a complete profile of XFZY capsules for the treatment of CHD with BSS and to reveal the potential mechanism of the XFZY capsules.

MATERIALS AND METHODS

A rat model of CHD with BSS was generated by combining a high-fat diet (HFD) with a left anterior descending coronary artery (LAD) ligation. After four weeks of treatment with XFZY capsules or simvastatin pills, an echocardiography was performed for a therapeutic evaluation. Blood samples and heart tissues were then collected for further analyses. A UPLC-QTOF/MS-based metabolomics analysis of the plasma was performed, and all metabolic features were fit by PCA and OPLS-DA pattern for the biomarker screen. The identified biomarkers were later implemented into a metabolic pathway analysis. Furthermore, we used qRT-PCR and Western blot analyses to verify the treatment effects of the XFZY capsules.

RESULTS

A total of 49 metabolites (VIP>1.0, p < 0.05, RSD%<20%) were identified in the Model rats, and 27 metabolites (VIP>1.0, p < 0.05, RSD%<20%) were identified in the XFZY-H rats. The results of the pathway analysis indicated that the XFZY capsules treated CHD primarily by regulating cardiac energy, phospholipid, polyunsaturated fatty acid (PUFA) and amino acid metabolism. In addition, blood viscosity and serum lipid assays suggested that XFZY capsules could decrease serum triglycerides, total cholesterol, low-density lipoprotein cholesterol and whole blood viscosity at a low shear rate.

CONCLUSION

This study demonstrated that the XFZY capsule effectively decreases serum lipids and whole blood viscosity in CHD with BSS. The underlying metabolic mechanism mainly included improving cardiac energy supply, reducing phospholipid peroxide, maintaining the PUFA metabolic balance and regulating amino acid metabolism.

Does L-carnitine supplementation affect serum levels of enzymes mainly produced by liver? A systematic review and meta-analysis of randomized controlled clinical trials

BACKGROUND AND AIMS

L-carnitine supplementation is proposed to reduce liver enzymes levels; however, previous findings were equivocal. The current systematic review and meta-analysis of randomized controlled clinical trials (RCTs) were performed to assess the effect of L-carnitine supplementation on serum levels of enzymes mainly produced by liver [alanine aminotransferase (ALT), aspartate aminotransferase (AST), and gamma-glutamyl transpeptidase (GGTP)].

METHODS

Online databases as well as the reference lists of relevant studies were searched from inception up to June 2019. The risk of bias in individual studies was assessed using Cochrane Collaboration's tool. Data were pooled using the random-effects model and expressed as mean differences (MDs) with 95% confidence intervals (CIs).

RESULTS

In total, 18 RCTs (1161 participants) met the eligibility criteria. L-carnitine supplementation dose ranged from 500 to 4000 mg/day. L-carnitine supplementation significantly reduced serum ALT (MD = - 8.65 IU/L, 95% CI - 13.40, - 3.90), AST (MD = - 8.52 IU/L, 95% CI - 12.16, - 4.89), and GGTP (MD = - 8.80 IU/L, 95% CI - 13.67, - 3.92) levels. The subgroup analysis showed that L-carnitine might be more effective in reducing the enzymes when supplemented in higher doses (≥ 2000 mg/day), for longer durations (> 12 weeks), and among patients with liver diseases. The meta-evidence was graded as "moderate" for ALT and AST, and "low" for GGTP according to NutriGrade scoring system.

CONCLUSION

L-carnitine supplementation significantly improves circulating ALT, AST and GGTP levels; therefore, it might positively affect liver function, especially among patients with liver diseases. Further high-quality RCTs are recommended to confirm our results.

The Potential Use of Metabolic Cofactors in Treatment of NAFLD

Non-alcoholic fatty liver disease (NAFLD) is caused by the imbalance between lipid deposition and lipid removal from the liver, and its global prevalence continues to increase dramatically. NAFLD encompasses a spectrum of pathological conditions including simple steatosis and non-alcoholic steatohepatitis (NASH), which can progress to cirrhosis and liver cancer. Even though there is a multi-disciplinary effort for development of a treatment strategy for NAFLD, there is not an approved effective medication available. Single or combined metabolic cofactors can be supplemented to boost the metabolic processes altered in NAFLD. Here, we review the dosage and usage of metabolic cofactors including l-carnitine, Nicotinamide riboside (NR), l-serine, and N-acetyl-l-cysteine (NAC) in human clinical studies to improve the altered biological functions associated with different human diseases. We also discuss the potential use of these substances in treatment of NAFLD and other metabolic diseases including neurodegenerative and cardiovascular diseases of which pathogenesis is linked to mitochondrial dysfunction.

Plasma Trimethylamine-N-oxide following Cessation of L-carnitine Supplementation in Healthy Aged Women

L-carnitine supplementation elevates plasma trimethylamine-N-oxide (TMAO), which may participate in atherosclerosis development by affecting cholesterol metabolism. The aim of the current study was to determine the effect of increased plasma TMAO on biochemical markers in the blood following cessation of L-carnitine supplementation. The follow-up measurements were performed on subjects who completed 24 weeks of L-carnitine or placebo supplementation protocol. Blood samples were taken after finishing the supplementation and then 4 and 12 months following the supplementation withdrawal. Four months after cessation of L-carnitine supplementation, plasma TMAO concentration reached a normal level which was stable for the following eight months. During this period, no modifications in serum lipid profile and circulating leukocyte count were noted. TMAO implications in health and disease is widely discussed. The results of this study demonstrate no adverse effects of elevated plasma TMAO, induced by L-carnitine, on the measured parameters at 4 and 12 months after withdrawal of supplementation.

The effect of l-carnitine supplementation on lipid profile and glycaemic control in adults with cardiovascular risk factors: A systematic review and meta-analysis of randomized controlled clinical trials

BACKGROUND & AIMS

Several randomized clinical trials (RCTs) have investigated the effect of l-carnitine supplementation on lipid profile and glycaemic control in adults with cardiovascular risk factors; however, the results were conflicting. Therefore, a meta-analysis was performed to assess the effect of l-carnitine on lipid profile and glycaemic control in adults with cardiovascular risk factors.

METHODS

We searched PubMed, Scopus, Cochrane Databases, Google Scholar, ProQuest, Web of Science and Embase for randomized, placebo-controlled human trials that investigated the effect of l-carnitine supplementation on lipid profile and glycaemic control up to April 2017. From the eligible trials, 24 articles were selected for the meta-analysis. The meta-analysis was performed in a random-effects model. Heterogeneity was determined by I² statistics and Cochrane Q test.

RESULTS

The result showed significant effect of l-carnitine on TC (WMD: -13.73 [95% CI: -22.28, -5.17] mg/dL; P < 0.001), LDL-C (WMD = - 7.70 [95% CI: - 11.80, -3.61]mg/dL; p < 0.001), HDL-C (WMD = 0.82 [95% CI: 0.44, 1.21] mg/dL; P > 0.001), Lp(a) (WMD = - 7.13 [95% CI: -9.82,- 4.43]mg/dL; P < 0.001), FPG (WMD = -6.25 [95% CI: -10.35, -2.16] mg/dL; P < 0.001), HbA1C (WMD (%) = - 0.35 [95% CI: -0.65,- 0.05]; p = 0.02) and HOMA-IR (WMD (%) = - 0.94 [95% CI: -1.89, -0.00]; P = 0.05). No effect of l-carnitine was detected in TG, Apo A-I and Apo B 100 on pooled effect size. Additionally, sensitivity analysis showed l-carnitine supplementation could improve glycaemic control, particularly along with hypocaloric diet.

CONCLUSION

This meta-analysis showed that l-carnitine supplementation could improve lipid profile levels, particularly in doses more than 1500 mg/day. More RCTs with large sample sizes, focusing on gut microbiome profiles and dietary patterns are needed to better understand the effect of l-carnitine on patients with cardiovascular risk factors.

Ciliary neurotrophic factor stimulates cardioprotection and the proliferative activity in the adult zebrafish heart

Unlike mammals, adult zebrafish can regenerate their hearts after injury via proliferation of cardiomyocytes. The cell-cycle entry of zebrafish cardiac cells can also be stimulated through preconditioning by thoracotomy, a chest incision without myocardial damage. To identify effector genes of heart preconditioning, we performed transcriptome analysis of ventricles from thoracotomized zebrafish. This intervention led to enrichment of cardioprotective factors, epithelial-to-mesenchymal transition genes, matrix proteins and components of LIFR/gp130 signaling. We identified that inhibition of the downstream signal transducer of the LIFR/gp130 pathway through treatment with Ruxolitinib, a specific JAK1/2 antagonist, suppressed the cellular effects of preconditioning. Activation of LIFR/gp130 signaling by a single injection of the ligand Cilliary Neurotrophic Factor, CNTF, was sufficient to trigger cardiomyocyte proliferation in the intact heart. In addition, CNTF induced other pro-regenerative processes, including expression of cardioprotective genes, activation of the epicardium, enhanced intramyocardial Collagen XII deposition and leucocyte recruitment. These effects were abrogated by the concomitant inhibition of the JAK/STAT activity. Mutation of the cntf gene suppressed the proliferative response of cardiomyocytes after thoracotomy. In the regenerating zebrafish heart, CNTF injection prior to ventricular cryoinjury improved the initiation of regeneration via reduced cell apoptosis and boosted cardiomyocyte proliferation. Our findings reveal the molecular effectors of preconditioning and demonstrate that exogenous CNTF exerts beneficial regenerative effects by rendering the heart more resilient to injury and efficient in activation of the proliferative programs.

A pilot study investigating circulating trimethylamine N-oxide and its precursors in dogs with degenerative mitral valve disease with or without congestive heart failure

BACKGROUND

Pathophysiologic mechanisms for the development and progression of degenerative mitral valve disease (DMVD) remain elusive. Increased concentrations of circulating trimethylamine N-oxide (TMAO) and its precursors choline and l-carnitine are associated with the presence and severity of heart disease in people.

OBJECTIVES

To determine if differences exist in plasma concentrations of TMAO, choline, or l-carnitine among dogs with DMVD and congestive heart failure (CHF), dogs with asymptomatic DMVD, and healthy control dogs.

ANIMALS

Thirty client-owned dogs: 10 dogs with CHF secondary to DMVD, 10 dogs with asymptomatic DMVD, and 10 healthy control dogs.

METHODS

A pilot cross-sectional study in which echocardiography was performed and fasting plasma concentrations of TMAO, choline, and l-carnitine (total and fractions) were measured.

RESULTS

TMAO (P = .03), total l-carnitine (P = .03), carnitine esters (P = .05), and carnitine esters to free carnitine ratio (E/F ratio; P = .05) were significantly higher in dogs with CHF compared to those with asymptomatic DMVD. TMAO (P = .02), choline (P = .01), total l-carnitine (P = .01), carnitine esters (P = .02), free carnitine (P = .02), and E/F ratio (P = .009) were significantly higher in dogs with CHF compared to healthy controls.

CONCLUSIONS AND CLINICAL IMPORTANCE

Dogs with CHF secondary to DMVD had higher concentrations of TMAO compared to both asymptomatic DMVD dogs and healthy controls. Larger prospective studies are warranted to determine if TMAO plays a role in the development or progression of DMVD or CHF.

Five potential therapeutic agents as antidepressants: a brief review and future directions

Despite the availability of numerous antidepressants, many patients with depression do not show adequate response. The therapeutic lag between drug administration and onset of clinical improvement observed with conventional antidepressants has led to a need for antidepressants with a novel mechanism of action. Recently, five such agents, including acetyl-L-carnitine, scopolamine, ω-3 polyunsaturated fatty acids, ketamine, and selective 5-HT7 serotonin receptor antagonists, have gained interest as potential antidepressants with enhanced symptom control, improved tolerability, and faster onset of action compared to conventional antidepressants. This review provides an update and critical examination of these five novel therapeutic agents as potential antidepressants.

The Effect of Different l-Carnitine Administration Routes on the Development of Atherosclerosis in ApoE Knockout Mice

SCOPE

l-Carnitine (LC) is abundant in red meat and is widely added to health supplements and food. This study focuses on the adverse effects of oral supplementation of 1.3% LC in ApoE^-/- mice and whether the parenteral administration of LC (subcutaneously, sub) has any impact on the development of atherosclerosis.

METHODS AND RESULTS

Mice are randomly divided into three groups (n = 15). All mice are fed a high-fat diet (HFD). The number of Ly6C^hi monocytes; degree of atherosclerosis; plasma LC, γ-butyrobetaine (γBB), and trimethylamine-N-oxide (TMAO) levels; and microbial community composition are analyzed. Compared with the HFD and HFD ± LC (sub) groups, the number of Ly6C^hi monocytes, atherosclerotic plaque area, and plasma γBB and TMAO levels are increased in the HFD ± LC (oral) group (p < 0.001). Plasma LC levels in the HFD ± LC (sub) group are higher than those in other groups. The levels of γBB, TMAO, and Ly6C^hi monocytes are positively correlated with atherosclerotic plaque area (p < 0.01), and TMAO is positively correlated with Bacteroidetes and negatively correlated with Firmicutes at the phylum level.

CONCLUSION

In contrast with oral LC administration, subcutaneous LC administration, which bypasses its conversion to TMAO in the liver, does not have a detrimental effect on the development of atherosclerosis in male ApoE^-/- mice. Taking LC parenterally may be preferable among patients who require LC supplementation.

Efficacy and Safety of L-Carnitine Treatment for Chronic Heart Failure: A Meta-Analysis of Randomized Controlled Trials

Background. Whether additional benefit can be achieved with the use of L-carnitine (L-C) in patients with chronic heart failure (CHF) remains controversial. We therefore performed a meta-analysis of randomized controlled trials (RCTs) to evaluate the effects of L-C treatment in CHF patients. Methods. Pubmed, Ovid Embase, Web of Science, and Cochrane Library databases, Chinese National Knowledge Infrastructure (CNKI) database, Wanfang database, Chinese Biomedical (CBM) database, and Chinese Science and Technology Periodicals database (VIP) until September 30, 2016, were identified. Studies that met the inclusion criteria were systematically evaluated by two reviewers independently. Results. 17 RCTs with 1625 CHF patients were included in this analysis. L-C treatment in CHF was associated with considerable improvement in overall efficacy (OR = 3.47, P < 0.01), left ventricular ejection fraction (LVEF) (WMD: 4.14%, P = 0.01), strike volume (SV) (WMD: 8.21 ml, P = 0.01), cardiac output (CO) (WMD: 0.88 L/min, P < 0.01), and E/A (WMD: 0.23, P < 0.01). Moreover, treatment with L-C also resulted in significant decrease in serum levels of BNP (WMD: −124.60 pg/ml, P = 0.01), serum levels of NT-proBNP (WMD: −510.36 pg/ml, P < 0.01), LVESD (WMD: −4.06 mm, P < 0.01), LVEDD (WMD: −4.79 mm, P < 0.01), and LVESV (WMD: −20.16 ml, 95% CI: −35.65 to −4.67, P < 0.01). However, there were no significant differences in all-cause mortality, 6-minute walk, and adverse events between L-C and control groups. Conclusions. L-C treatment is effective for CHF patients in improving clinical symptoms and cardiac functions, decreasing serum levels of BNP and NT-proBNP. And it has a good tolerance.

L-carnitine for cognitive enhancement in people without cognitive impairment

BACKGROUND

Safe interventions to enhance cognitive function in cognitively healthy people would be very valuable for several reasons, including a better quality of life and professional success. While L-carnitine has been reported to enhance cognitive function in some conditions, its efficacy is disputed. The evidence of its efficacy for cognitively healthy people has not previously been systematically reviewed.

OBJECTIVES

To assess the efficacy and safety of L-carnitine for the enhancement of cognitive function in people without cognitive impairment.

SEARCH METHODS

We searched ALOIS, the Cochrane Dementia and Cognitive Improvement Group's Specialized Register, on 4 November 2016. We used the search terms 'L-carnitine' or 'acetyl-L-carnitine' or 'propionyl-L-carnitine' or 'ALC' or 'PLC' or 'ALCAR' or 'ALPAR'. We ran additional separate searches in several other sources to ensure that we retrieved the most up-to-date results. We also reviewed the bibliographies of the randomised controlled trials identified and contacted the authors and known experts in the field and pharmaceutical companies to identify additional published or unpublished data.

SELECTION CRITERIA

Eligible trials were randomised controlled trials (RCTs) or quasi-RCTs, parallel-group or cross-over, that compared L-carnitine or its derivatives, acetyl-L-carnitine or propionyl-L-carnitine, at any dose and for any length of treatment, with placebo or no treatment in cognitively healthy people of any age and either gender.

DATA COLLECTION AND ANALYSIS

We used standard methodological procedures expected by Cochrane. Two review authors independently selected trials and evaluated the methodological quality, then extracted and analysed data from the included trials.

MAIN RESULTS

Only two RCTs were eligible. One was a cross-over trial with 18 participants. The other randomised 400 participants to one of four treatments, of which two (L-carnitine and placebo) were relevant to this review, but the exact numbers of participants in these two treatment groups was not reported. All participants were young adults. Methodological details were poorly reported, and we considered the risk of bias in both studies to be unclear. The trials assessed different cognitive outcomes. We could extract cognitive data on approximately 200 participants from one trial. We found no evidence that L-carnitine has any effect on reaction time, vigilance, immediate memory, or delayed recall after three days of treatment. This trial report stated that there was a small number of adverse effects, none of which were serious. The small cross-over trial also reported no effect of L-carnitine on cognition, but did not provide data; no information was provided on adverse effects. We considered the available evidence to be of very low quality for all reported outcomes.

AUTHORS' CONCLUSIONS

Due to the limited number of included trials, short-term treatment, and inadequate reporting, we were unable to draw any conclusions about the efficacy or safety of L-carnitine for cognitive enhancement in healthy adults. Well-designed, randomised, placebo-controlled trials of L-carnitine for cognition enhancement in cognitively healthy people, with large samples and relatively long-term follow-up, are still needed.

The effect of (L-)carnitine on weight loss in adults: a systematic review and meta-analysis of randomized controlled trials

This study provides a systematic review and meta-analysis of randomized controlled trials, which have examined the effect of the carnitine on adult weight loss. Relevant studies were identified by systematic search of PubMed, Embase, Cochrane Central Register of Controlled Trials and reference lists of relevant marker studies. Nine studies (total n = 911) of adequate methodological quality were included in the review. Trials with mean difference (MD) of 95% confidence interval (CI) were pooled using random effect model. Results from meta-analysis of eligible trials revealed that subjects who received carnitine lost significantly more weight (MD: -1.33 kg; 95% CI: -2.09 to -0.57) and showed a decrease in body mass index (MD: -0.47 kg m(-2) ; 95% CI: -0.88 to -0.05) compared with the control group. The results of meta-regression analysis of duration of consumption revealed that the magnitude of weight loss resulted by carnitine supplementation significantly decreased over time (p = 0.002). We conclude that receiving the carnitine resulted in weight loss. Using multiple-treatments meta-analysis of the drugs and non-pharmacotherapy options seem to be insightful areas for research. © 2016 World Obesity.

Human risk of diseases associated with red meat intake: Analysis of current theories and proposed role for metabolic incorporation of a non-human sialic acid

One of the most consistent epidemiological associations between diet and human disease risk is the impact of red meat consumption (beef, pork, and lamb, particularly in processed forms). While risk estimates vary, associations are reported with all-cause mortality, colorectal and other carcinomas, atherosclerotic cardiovascular disease, type II diabetes, and possibly other inflammatory processes. There are many proposed explanations for these associations, some long discussed in the literature. Attempts to explain the effects of red meat consumption have invoked various red meat-associated agents, including saturated fat, high salt intake, Trimethylamine-N-oxide (TMAO) generation by microbiota, and environmental pollutants contaminating red meat, none of which are specific for red meat. Even the frequently mentioned polycyclic aromatic carcinogens arising from high temperature cooking methods are not red meat specific, as these are also generated by grilling poultry or fish, as well as by other forms of cooking. The traditional explanations that appear to be more red meat specific invoke the impact of N-nitroso compounds, heme iron, and the potential of heme to catalyze endogenous nitrosation. However, heme can be denatured by cooking, high levels of plasma hemopexin will block its tissue delivery, and much higher amounts of heme likely originate from red blood cell breakdown in vivo. Therefore, red meat-derived heme could only contribute to colorectal carcinoma risk, via direct local effects. Also, none of these mechanisms explain the apparent human propensity i.e., other carnivores have not been reported at high risk for all these diseases. A more recently proposed hypothesis involves infectious agents in beef from specific dairy cattle as agents of colorectal cancer. We have also described another mechanistic explanation for the human propensity for risk of red-meat associated diseases that is consistent with most observations: metabolic incorporation of a non-human sialic acid N-glycolylneuraminic acid (Neu5Gc) into the tissues of red meat consumers and the subsequent interaction with inflammation-provoking antibodies against this "xenoautoantigen". Overall, we conclude that while multiple mechanisms are likely operative, many proposed theories to date are not specific for red meat, and that the viral and xenoautoantigen theories deserve further consideration. Importantly, there are potential non-toxic dietary antidotes, if the xenoautoantigen theory is indeed correct.

Impact of L-carnitine on plasma lipoprotein(a) concentrations: A systematic review and meta-analysis of randomized controlled trials

We aimed to assess the impact of L-carnitine on plasma Lp(a) concentrations through systematic review and meta-analysis of available RCTs. The literature search included selected databases up to 31^st January 2015. Meta-analysis was performed using fixed-effects or random-effect model according to I² statistic. Effect sizes were expressed as weighted mean difference (WMD) and 95% confidence interval (CI). The meta-analysis showed a significant reduction of Lp(a) levels following L-carnitine supplementation (WMD: −8.82 mg/dL, 95% CI: −10.09, −7.55, p < 0.001). When the studies were categorized according to the route of administration, a significant reduction in plasma Lp(a) concentration was observed with oral (WMD: −9.00 mg/dL, 95% CI: −10.29, −7.72, p < 0.001) but not intravenous L-carnitine (WMD: −2.91 mg/dL, 95% CI: −10.22, 4.41, p = 0.436). The results of the meta-regression analysis showed that the pooled estimate is independent of L-carnitine dose (slope: −0.30; 95% CI: −4.19, 3.59; p = 0.878) and duration of therapy (slope: 0.18; 95% CI: −0.22, 0.59; p = 0.374). In conclusion, the meta-analysis suggests a significant Lp(a) lowering by oral L-carnitine supplementation. Taking into account the limited number of available Lp(a)-targeted drugs, L-carnitine might be an effective alternative to effectively reduce Lp(a). Prospective outcome trials will be required to fully elucidate the clinical value and safety of oral L-carnitine supplementation.

Effect of levocarnitine on TIMP-1, ICAM-1 expression of rats with coronary heart disease and its myocardial protection effect

OBJECTIVE

To study the effect of levocarnitine (L-CN) on tissue inhibitor of metalloproteinase-1 (TIMP-1) and intercellular adhesion molecule-1 (ICAM-1) expression of rats with coronary heart disease and evaluate the protective effect of L-CN on myocardial cells.

METHODS

High-fat diet feeding and intraperitoneal injection of pituitrin was performed on rats in model group and CHD Model of rats was built. Rats with successful model-building were selected and divided into L-CN group and Ctrl group randomly. Rats in L-CN group were given L-CN treatment, with intraperitoneal injection of 200 mg·kg(-1)·d(-1) and successive administration for 3 d. Rats in Ctrl group were given equal volumes of normal saline. Blood was collected from carotid artery at different time and expression quantity of creatine kinase-MB (CK-MB) and Troponin Ⅰ (TnⅠ) in serum was detected. Rats in each group were put to death and were separated to obtain the myocardial tissue. Real-time PCR and Western Blotting hybridization were performed to detect the TIMP-1, ICAM-1 expression in myocardial tissue in each group. Statistical analysis was employed to explore the expression changes of TIMP-1 and ICAM-1, and ELISA test was used to analyze the expression changes of myocardial necrosis marker-CK-MB and TnⅠto learn the effect of L-CN and its myocardial protective effect.

RESULTS

The total cholesterol, triglyceride and blood glucose levels of rats in model group were significantly higher than that in control group, which indicated that due to high-fat diet feeding, blood lipid of rats in model group was obviously higher than that in control group. In myocardial tissue of rats in model group, TIMP-1 level significantly reduced and ICAM-1 level significantly increased (P < 0.01). In model group, after L-CN treatment, TIMP-1 level had double increase, while ICAM-1 level had 43% of decrease in L-CN group compared with Ctrl group. After L-CN intervention treatment, CK-MB and TnⅠ content in L-CN group relatively reduced compared with Ctrl group. The difference among groups was obvious (P < 0.01).

CONCLUSIONS

L-CN could increase the TIMP-1 expression level and inhibit the ICAM-1 expression level. L-CN has a certain myocardial protective effect.

The gut microbiome, diet, and links to cardiometabolic and chronic disorders

Cardiometabolic diseases (CMDs) have been associated with changes in the composition of the gut microbiota, with links between the host environment and microbiota identified in preclinical models. High-throughput sequencing technology has facilitated in-depth studies of the gut microbiota, bacterial-derived metabolites, and their association with CMDs. Such strategies have shown that patients with CMDs frequently exhibit enrichment or depletion of certain bacterial groups in their resident microbiota compared to healthy individuals. Furthermore, the ability to transfer resident gut microbiota from mice or humans into germ-free mouse models, or between human patients, has enabled researchers to characterize the causative role of the gut microbiota in CMDs. These approaches have helped identify that dietary intake of choline, which is metabolized by the gut microbiota, is associated with cardiovascular outcomes in mice and humans. Trimethylamine N-oxide (TMAO) - a metabolite derived from the gut microbiota - is also associated with poor cardiovascular outcomes in patients with cardiovascular disease and is elevated in patients with chronic kidney disease (CKD). TMAO might represent a biomarker that links the environment and microbiota with CKD. This Review summarizes data suggesting a link between the gut microbiota and derived metabolites with food intake patterns, metabolic alterations, and chronic CMDs.

A Phospholipid-Protein Complex from Antarctic Krill Reduced Plasma Homocysteine Levels and Increased Plasma Trimethylamine-N-Oxide (TMAO) and Carnitine Levels in Male Wistar Rats

Seafood is assumed to be beneficial for cardiovascular health, mainly based on plasma lipid lowering and anti-inflammatory effects of n-3 polyunsaturated fatty acids. However, other plasma risk factors linked to cardiovascular disease are less studied. This study aimed to penetrate the effect of a phospholipid-protein complex (PPC) from Antarctic krill on one-carbon metabolism and production of trimethylamine-N-oxide (TMAO) in rats. Male Wistar rats were fed isoenergetic control, 6%, or 11% PPC diets for four weeks. Rats fed PPC had reduced total homocysteine plasma level and increased levels of choline, dimethylglycine and cysteine, whereas the plasma level of methionine was unchanged compared to control. PPC feeding increased the plasma level of TMAO, carnitine, its precursors trimethyllysine and γ-butyrobetaine. There was a close correlation between plasma TMAO and carnitine, trimethyllysine, and γ-butyrobetaine, but not between TMAO and choline. The present data suggest that PPC has a homocysteine lowering effect and is associated with altered plasma concentrations of metabolites related to one-carbon metabolism and B-vitamin status in rats. Moreover, the present study reveals a non-obligatory role of gut microbiota in the increased plasma TMAO level as it can be explained by the PPC's content of TMAO. The increased level of carnitine and carnitine precursors is interpreted to reflect increased carnitine biosynthesis.

Listening to Our Gut: Contribution of Gut Microbiota and Cardiovascular Risk in Diabetes Pathogenesis

What we understand about diabetes from decades of genetics research is now being supplemented with exciting new evidence based on a better understanding of how one of the biggest "environmental" factors the body is exposed to is influencing the pathogenesis of disease. The recent discovery that certain dietary nutrients possessing a trimethylamine (TMA) moiety (namely choline/phosphatidylcholine and L-carnitine) participate in the development of atherosclerotic heart disease has renewed attention towards the contributions of gut microbiota in the development of cardiovascular diseases. Collectively, animal and human studies reveal that conversion of these nutrient precursors to trimethylamine N-oxide (TMAO) depends on both microbial composition and host factors, and can be induced by dietary exposures. In addition, circulating TMAO levels are strongly linked to cardiovascular disease risks and various adverse cardio-renal consequences. Our group and others have further demonstrated that circulating TMAO levels are elevated in patients with type 2 diabetes mellitus compared to healthy controls and gut microbiota-dependent phosphatidylcholine metabolism has been implicated in metabolic dysregulation and insulin resistance in animal models. Therefore, preventive strategies to minimize adverse consequences associated with TMAO generation in the diabetic population are warranted.

L-Carnitine Supplementation Reduces Short-Term Neutrophil-Lymphocyte Ratio in Patients Undergoing Coronary Artery Bypass Grafting

This study aims to investigate whether preoperative L-carnitine supplementation affects the neutrophil-to-lymphocyte ratio (NLR) in patients undergoing coronary artery bypass grafting surgery. The neutrophil-to-lymphocyte ratio is an inflammatory marker that has proven usefulness for predicting postoperative complications in coronary artery bypass surgery. A lot of studies concerning the role of L-carnitine in the immune system have been performed, contradictory results have been reported on its effects on absolute numbers of WBC subtypes. This randomized, double-blinded, placebo-controlled study was conducted among patients scheduled for coronary artery bypass grafting surgery between June 2012 and December 2013 in our cardiovascular surgery clinic. A total of 60 consecutive patients were randomized and divided into 2 groups. The first group received 2 g of L-carnitine in 1000 mL of 0.9% saline solution infused over 24 hours for each of the 3 preoperative days (L-carnitine group, n = 30), or only 1000 mL of 0.9% saline solution for the same time period (placebo group, n = 30). The basal values of leukocyte, neutrophil, lymphocyte counts, and neutrophil to lymphocyte ratio were similar in the 2 groups. After L-carnitine supplementation (just before surgery), leukocyte and neutrophil counts of the L-carnitine group were significantly lower than those of the placebo group (7.7 ± 1.5 versus 9.7 ± 2.6, P < 0.001 and 4.6 ± 1.3 versus 6.5 ± 2.2, P < 0.001). On postoperative day 1, lymphocyte counts were significantly higher in the L-carnitine group (1.1 ± 0.6 versus 0.8 ± 0.9, P < 0.001). Moreover, the increase in NLR was significantly lower in the L-carnitine group at postoperative day 1 (20.7 ± 13.8 versus 10.8 ± 4.1, P < 0.001). Preoperative L-carnitine supplementation may reduce neutrophil-lymphocyte ratio during the early postoperative period of coronary artery bypass grafting surgery.