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

Cadmium as a male reproductive toxicant and natural and non-natural ways to tackle it: a review

Cadmium (Cd) is a naturally occurring environmental pollutant, a toxic substance that causes oxidative stress. According to epidemiological studies, the data suggested that environmental and occupational Cd exposure may be related to several diseases and severe testicular damage. However, studies are going on to explore the mechanism of Cd-induced male reproductive toxicity and its treatment strategies. Currently, researchers are focusing on naturally occurring bioactive compounds, plant extracts, and biochemical, which have better efficacy, less toxicity, and high bioavailability. This review focuses on the mechanistic effect of Cd on testicular toxicity and different categories of compounds having a beneficial impact on Cd-induced male reproductive toxicity. Some potent bioactive antioxidants are quercetin, caffeic acid phenethyl ester, cyanidin-3-O-glucoside, curcumin, and silymarin. In comparison, plant extracts are Costus afer leaf methanol extract, methanol root extract of Carpolobia lutea, red carrot methanolic extract, Panax ginseng extract, and biochemicals including melatonin, progesterone, glutamine, L-carnitine, and selenium. Advanced and more detailed studies are needed on these compounds to explore their mechanism in attenuating Cd-induced testicular toxicity and can be potential therapeutics in the future.

L-Carnitine supplementation reduces biomarkers of inflammatory and oxidative stress in patients with coronary artery disease: a randomised controlled trial

OBJECTIVE

l-Carnitine has been suggested as a potential nutrient that alleviates the oxidative and inflammatory damages of coronary artery disease (CAD), but the results of the previous studies of the importance of this supplementation remains unclear. This study attempts to evaluate the effects of l-carnitine (LC) supplementation on oxidative stress and inflammatory biomarkers in patients with CAD.

METHODS

A double-blind, randomised, placebo-trial was conducted on 75 CAD subjects. Patients were randomly assigned to receive LC (1000 mg/day) or placebo capsules over 3 months. Sera high-sensitivity C-reactive protein (hs-CRP), myeloperoxidase (MPO), nitrotyrosine (NT) and total antioxidant capacity (TAC) were assayed.

RESULTS

A significant increase in serum TAC and a significant decrease in MPO, NT, and hs-CRP levels were detected following 12 weeks of LC supplementation, compared to the placebo.

CONCLUSIONS

These results suggest that LC supplementation may exert beneficial effect on cardiovascular health through attenuate oxidative and inflammatory markers in CAD patients.

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.

Inhibition of Trimethylamine N-Oxide Attenuates Neointimal Formation Through Reduction of Inflammasome and Oxidative Stress in a Mouse Model of Carotid Artery Ligation

Aims: Trimethylamine-N-oxide (TMAO) is a metabolite generated from dietary choline, betaine, and l-carnitine, after their oxidization in the liver. TMAO has been identified as a novel independent risk factor for atherosclerosis through the induction of vascular inflammation. However, the effect of TMAO on neointimal formation in response to vascular injury remains unclear. Results: This study was conducted using a murine model of acutely disturbed flow-induced atherosclerosis induced by partial carotid artery ligation. 3,3-Dimethyl-1-butanol (DMB) was used to reduce TMAO concentrations. Wild-type mice were divided into four groups [regular diet, high-TMAO diet, high-choline diet, and high-choline diet+DMB] to investigate the effects of TMAO elevation and its inhibition by DMB. Mice fed high-TMAO and high-choline diets had significantly enhanced neointimal hyperplasia and advanced plaques, elevated arterial elastin fragmentation, increased macrophage infiltration and inflammatory cytokine secretion, and enhanced activation of nuclear factor (NF)-κB, the NLRP3 inflammasome, and endoplasmic reticulum (ER) stress relative to the control group. Mice fed high-choline diets with DMB treatment exhibited attenuated flow-induced atherosclerosis, inflammasome expression, ER stress, and reactive oxygen species expression. Human aortic smooth muscle cells (HASMCs) were used to investigate the mechanism of TMAO-induced injury. The HASMCs were treated with TMAO with or without an ER stress inhibitor to determine whether inhibition of ER stress modulates the TMAO-induced inflammatory response. Innovation: This study demonstrates that TMAO regulates vascular remodeling via ER stress. Conclusion: Our findings demonstrate that TMAO elevation promotes disturbed flow-induced atherosclerosis and that DMB administration mitigates vascular remodeling, suggesting a rationale for a TMAO-targeted strategy for the treatment of atherosclerosis. Antioxid. Redox Signal. 38, 215-233.

Effects of L-carnitine supplementation for women with polycystic ovary syndrome: a systematic review and meta-analysis

Background

Polycystic ovary syndrome (PCOS) is a disorder in reproductive age women and is characterized by hyperandrogenic anovulation and oligo-amenorrhea, which leads to infertility. Anovulation in PCOS is associated with low follicle-stimulating hormone levels and the arrest of antral follicle development in the final stages of maturation. L-carnitine (LC) plays a role in fatty acid metabolism, which is found to be lacking in PCOS patients. This systematic review and meta-analysis aimed to determine the effectiveness of LC supplementation for patients with PCOS.

Methods

We searched the Cochrane Central Register of Controlled Trials (CENTRAL), MEDLINE, Embase, Cumulative Index to Nursing and Allied Health Literature (CINAHL), Psychological Information Database (PsycINFO), and the World Health Organization International Clinical Trials Registry Platform for all randomized control trials, comparing LC alone or in combination with other standard treatments for the treatment of PCOS from inception till June 2021. We independently screened titles and abstracts to identify available trials, and complete texts of the trials were checked for eligibility. Data on the methods, interventions, outcomes, and risk of bias from the included trials were independently extracted by the authors. The estimation of risk ratios and mean differences with a 95 percent confidence interval (CI) was performed using a random-effects model.

Results

Nine studies with 995 participants were included in this review. Five comparison groups were involved. In one comparison group, LC reduced the fasting plasma glucose (FPG) (mean differences (MD) -5.10, 95% CI [-6.25 to -3.95]; P = 0.00001), serum low-density lipoprotein (LDL) (MD -25.00, 95% CI [-27.93 to -22.07]; P = 0.00001), serum total cholesterol (MD -21.00, 95% CI [-24.14 to -17.86]; P = 0.00001), and serum triglyceride (TG) (MD -9.00, 95% CI [-11.46 to -6.54]; P = 0.00001) with moderate certainty of evidence. Another comparison group demonstrated that LC lowers the LDL (MD -12.00, 95% CI [-15.80 to -8.20]; P = 0.00001), serum total cholesterol (MD -24.00, 95% CI [-27.61 to -20.39]; P = 0.00001), and serum TG (MD -19.00, 95% CI [-22.79 to -15.21]; P = 0.00001) with moderate certainty of evidence.

Conclusion

There was low to moderate certainty of evidence that LC improves Body Mass Index (BMI) and serum LDL, TG, and total cholesterol levels in women with PCOS.

L-carnitine, a friend or foe for cardiovascular disease? A Mendelian randomization study

BACKGROUND

L-carnitine is emerging as an item of interest for cardiovascular disease (CVD) prevention and treatment, but controversy exists. To examine the effectiveness and safety of L-carnitine, we assessed how genetically different levels of L-carnitine are associated with CVD risk and its risk factors. Given higher CVD incidence and L-carnitine in men, we also examined sex-specific associations.

METHODS

We used Mendelian randomization to obtain unconfounded estimates. Specifically, we used genetic variants to predict L-carnitine, and obtained their associations with coronary artery disease (CAD), ischemic stroke, heart failure, and atrial fibrillation, as well as CVD risk factors (type 2 diabetes, glucose, HbA1c, insulin, lipid profile, blood pressure and body mass index) in large consortia and established cohorts, as well as sex-specific association in the UK Biobank. We obtained the Wald estimates (genetic association with CVD and its risk factors divided by the genetic association with L-carnitine) and combined them using inverse variance weighting. In sensitivity analysis, we used different analysis methods robust to pleiotropy and replicated using an L-carnitine isoform, acetyl-carnitine.

RESULTS

Genetically predicted L-carnitine was nominally associated with higher risk of CAD overall (OR 1.07 per standard deviation (SD) increase in L-carnitine, 95% CI 1.02 to 1.11) and in men (OR 1.09, 95% CI 1.02 to 1.16) but had a null association in women (OR 1.00, 95% CI 0.92 to 1.09). These associations were also robust to different methods and evident for acetyl-carnitine.

CONCLUSIONS

Our findings do not support a beneficial association of L-carnitine with CVD and its risk factors but suggest potential harm. L-carnitine may also exert a sex-specific role in CAD. Consideration of the possible sex disparity and exploration of the underlying pathways would be worthwhile.

Progression of atherosclerosis with carnitine supplementation: a randomized controlled trial in the metabolic syndrome

Background

L-carnitine (L-C), a ubiquitous nutritional supplement, has been investigated as a potential therapy for cardiovascular disease, but its effects on human atherosclerosis are unknown. Clinical studies suggest improvement of some cardiovascular risk factors, whereas others show increased plasma levels of pro-atherogenic trimethylamine N-oxide. The primary aim was to determine whether L-C therapy led to progression or regression of carotid total plaque volume (TPV) in participants with metabolic syndrome (MetS).

Methods

This was a phase 2, prospective, double blinded, randomized, placebo-controlled, two-center trial. MetS was defined as ≥ 3/5 cardiac risk factors: elevated waist circumference; elevated triglycerides; reduced HDL-cholesterol; elevated blood pressure; elevated glucose or HbA1c; or on treatment. Participants with a baseline TPV ≥ 50 mm³ were randomized to placebo or 2 g L-C daily for 6 months.

Results

The primary outcome was the percent change in TPV over 6 months. In 157 participants (L-C N = 76, placebo N = 81), no difference in TPV change between arms was found. The L-C group had a greater increase in carotid atherosclerotic stenosis of 9.3% (p = 0.02) than the placebo group. There was a greater increase in total cholesterol and LDL-C levels in the L-C arm.

Conclusions

Though total carotid plaque volume did not change in MetS participants taking L-C over 6-months, there was a concerning progression of carotid plaque stenosis. The potential harm of L-C in MetS and its association with pro-atherogenic metabolites raises concerns for its further use as a potential therapy and its widespread availability as a nutritional supplement.

Trial registration: ClinicalTrials.gov, NCT02117661, Registered April 21, 2014, https://clinicaltrials.gov/ct2/show/NCT02117661.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12986-022-00661-9.

The synthesis of N-(4-aryl-thiazol-2-yl)-N1-(4,5,6,7-tetrahydro-3H-azepin-2-yl)-hydrazine hydrobromides and the cardioprotective activity of (41-methoxyphenyl-thiazol-2-yl) derivative

A novel series of N-(4-aryl-thiazol-2-yl)-N1-(4,5,6,7-tetrahydro-3Н-azepin-2-yl)-hydrazine derivatives were synthesized by interaction of equimolar quantities of substituted α-bromacetophenones with thiosemicarbazide and characterized on the basis of their elemental analyses and spectral data. Study of cardioprotective activity of the all new products in comparison to levocarnitine and its synthetic analogue mildronate were carried out. Thus, specified results indicate, N-[(41-methoxyphenyl)-thiazol-2-yl)]-N1-(4,5,6,7-tetrahydro-3Н-azepin-2-yl)-hydrazine hydrobromide was influenced deceleration of contractive response of smooth muscles to hypoxia 13.2% more effective than levocarnitine and 6.85% more effective than mildronate and were shown pronounced cardioprotective properties. Obtained data justifies further study of N-(4-aryl-thiazol-2-yl)-N1-(4,5,6,7-tetrahydro-3Н-azepin-yl)-hydrazine derivatives as new potential cardioprotective drugs for treatment of various cardiac diseases.

Selenium and L-Carnitine Ameliorate Reproductive Toxicity Induced by Cadmium in Male Mice

Cadmium (Cd) has been reported to reduce male fertility, impair reproductive capacity, and play a major role in the pathogenesis of infertility. This study was conducted to investigate the possible protective role of Selenium (Se) and L-carnitine (LC) against the adverse effects induced by Cd on the male reproductive system in mice. Animals were randomly divided into seven groups (n = 10); control group and six treated groups, as follows: Cd (0.35 mg/kg), Se (0.87 mg/kg), LC (10 mg/kg), and a combination of either Se or LC and then a combination of both with Cd, and all animals were injected for a period of 30 days. Exposure of Cd showed a significant decrease in enzymatic antioxidant activities, deficiency in reproductive performance, decrease serum testosterone level, severe changes in the histopathological architecture, and higher degree of damages and appearance of unblemished DNA strands. Treatment with Se and LC has the highly synergistic and ameliorates the damaging effect of Cd on the testis through the elevation of the enzymatic antioxidant and diminish histopathological abnormalities and DNA damage.

Coronary heart disease and intestinal microbiota

Changes in human body systems influence metabolism and may cause disease. The intestinal microbiota influence health and is itself influenced by factors including diet and drugs. Investigation of the relationship of the intestinal microbiota and chronic conditions like coronary heart disease (CHD) has been facilitated by advances in sequencing technology. Some studies have identified changes in the composition and the metabolism of intestinal microbiota in patients with CHD, including increases in phyla Bacteroidetes and Proteobacteria and decreases in phyla Firmicutes and Fusobacteria. The ratio of two metabolites of intestinal bacteria, trimethylamine and trimethylamine N-oxide, has been found to be related to CHD. This review summarizes recent research to provide ideas for further research on the relationships between intestinal microbiota and CHD and on the preventive measures for CHD.

Mutual Interactions among Exercise, Sport Supplements and Microbiota

The adult gut microbiota contains trillions of microorganisms of thousands of different species. Only one third of gut microbiota are common to most people; the rest are specific and contribute to enhancing genetic variation. Gut microorganisms significantly affect host nutrition, metabolic function, immune system, and redox levels, and may be modulated by several environmental conditions, including physical activity and exercise. Microbiota also act like an endocrine organ and is sensitive to the homeostatic and physiological changes associated with training; in turn, exercise has been demonstrated to increase microbiota diversity, consequently improving the metabolic profile and immunological responses. On the other side, adaptation to exercise might be influenced by the individual gut microbiota that regulates the energetic balance and participates to the control of inflammatory, redox, and hydration status. Intense endurance exercise causes physiological and biochemical demands, and requires adequate measures to counteract oxidative stress, intestinal permeability, electrolyte imbalance, glycogen depletion, frequent upper respiratory tract infections, systemic inflammation and immune responses. Microbiota could be an important tool to improve overall general health, performance, and energy availability while controlling inflammation and redox levels in endurance athletes. The relationship among gut microbiota, general health, training adaptation and performance, along with a focus on sport supplements which are known to exert some influence on the microbiota, will be discussed.

Nutraceutical targeting of TLR4 signaling has potential for prevention of cancer cachexia

The mechanisms underlying cancer cachexia - the proximate cause of at least 20% of cancer-related deaths - have until recently remained rather obscure. New research, however, clarifies that cancers evoking cachexia release microvesicles rich in heat shock proteins 70 and 90, and that these extracellular heat shock proteins induce cachexia by serving as agonists for toll-like receptor 4 (TLR4) in skeletal muscle, macrophages, and adipocytes. Hence, safe nutraceutical measures which can down-regulate TLR4 signaling can be expected to aid prevention and control of cancer cachexia. There is reason to suspect that phycocyanobilin, ferulic acid, glycine, long-chain omega-3s, green tea catechins, β-hydroxy-β-methylbutyrate, carnitine, and high-dose biotin may have some utility in this regard.

Exploratory metabolomics of metabolic syndrome: A status report

Metabolic syndrome (MetS) is as a cluster of cardio-metabolic factors that greatly increase the risk of chronic diseases such as type II diabetes mellitus and atherosclerotic cardiovascular disease. In the United States, obesity, physical inactivity, aging, and genetics (to a minor extent) have arisen as risk factors for developing MetS. Although 35% of American adults suffer from MetS, its pathogenesis largely remains unknown. Worse, there is a lack of screening and optimum therapy for this disease. Researchers have consequently turned towards metabolomics to identify biomarkers to better understand MetS. The purpose of this review is to characterize various metabolites and their potential connections to MetS. Numerous studies have also characterized MetS as a disease of increased inflammation, and therefore this review also explores how metabolites play a role in various inflammatory pathways. Our review explores a broad range of metabolites including biogenic amines, branched chain amino acids, aromatic amines, phosphatidylcholines, as well as a variety of other molecules. We will explore their biochemical pathways and their potential role in serving as biomarkers.

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.

Decompensated Chronic Heart Failure Reduces Plasma L-carnitine

The heart has an intense aerobic metabolism and is among the most metabolically active organs in the body. Its tissue stores fatty acid, the main energetic substrate, and requires high concentrations of plasma L-carnitine. This nutrient is essential in the transport of fatty acids to the mitochondria to generate energy and maintain the proper concentration of coenzyme A free. In decompensated chronic heart failure metabolic changes, associated with inflammation, alter the metabolism of L-carnitine and compromise cardiac energy metabolism. The aim of this study was to evaluate plasma L-carnitine in chronic heart failure patients during cardiac decompensation. A cross-sectional study was conducted with 109 volunteers with chronic heart failure. Participants were stratified in the compensated (HF compensated) and decompensated (decompensated HF) groups. Plasma L-carnitine was evaluated by the spectrophotometric enzymatic method. Low plasma L-carnitine was found in the decompensated HF group (p = 0.0001). In this group it was also observed that 29.1% of the participants presented plasma L-carnitine below the reference range (<20 mmol). Reduced plasma L-carnitine in patients with decompensated chronic systolic heart failure was founded. These findings suggest that plasma L-carnitine assessment may be helpful in clinical practice for the treatment of patients with cardiac decompensation.

Implication of Trimethylamine N-Oxide (TMAO) in Disease: Potential Biomarker or New Therapeutic Target

Trimethylamine N-oxide (TMAO) is a molecule generated from choline, betaine, and carnitine via gut microbial metabolism. The plasma level of TMAO is determined by several factors including diet, gut microbial flora, drug administration and liver flavin monooxygenase activity. In humans, recent clinical studies evidence a positive correlation between elevated plasma levels of TMAO and an increased risk for major adverse cardiovascular events. A direct correlation between increased TMAO levels and neurological disorders has been also hypothesized. Several therapeutic strategies are being explored to reduce TMAO levels, including use of oral broad spectrum antibiotics, promoting the growth of bacteria that use TMAO as substrate and the development of target-specific molecules. Despite the accumulating evidence, it is questioned whether TMAO is the mediator of a bystander in the disease process. Thus, it is important to undertake studies to establish the role of TMAO in human health and disease. In this article, we reviewed dietary sources and metabolic pathways of TMAO, as well as screened the studies suggesting possible involvement of TMAO in the etiology of cardiovascular and neurological disorders, underlying the importance of TMAO mediating inflammatory processes. Finally, the potential utility of TMAO as therapeutic target is also analyzed.

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

PURPOSE

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

METHODS

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

RESULTS

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

CONCLUSION

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

Changes to trimethylamine-N-oxide and its precursors in nascent metabolic syndrome

Background Metabolic syndrome (MetS), a cardio-metabolic cluster afflicting 35% of American adults, increases cardiovascular disease (CVD) and type-2 diabetes (T2DM) risk. Increased levels of trimethylamine N-oxide (TMAO), a metabolite derived from choline and L-carnitine, correlates with CVD and T2DM. However, the precise role of TMAO and its precursors in MetS remains unclear. We tested the hypothesis that choline, L-carnitine and TMAO in MetS patients without CVD or T2DM would be altered and correlate with inflammatory markers. Materials and methods This was an exploratory study of 30 patients with nascent MetS (without CVD or T2DM) and 20 matched controls. MetS was defined by the Adult Treatment Panel III criteria. TMAO and its precursors were evaluated from each patient's frozen early morning urine samples and quantified using liquid chromatography/mass spectrometry (LC-MS). These amines were correlated with a detailed repertoire of biomarkers of inflammation and adipokines. Results L-carnitine was significantly increased (p = 0.0002) compared to controls. There was a trend for a significant increase in TMAO levels (p = 0.08). Choline was not significantly altered in MetS. L-carnitine correlated significantly with soluble tumor necrosis factor 1 (sTNFR1) and leptin, and inversely to adiponectin. TMAO correlated with IL-6, endotoxin and chemerin. Neither choline, nor L-carnitine significantly correlated with TMAO. Conclusion L-carnitine is directly correlated with markers of inflammation in nascent MetS. Cellular L-carnitine could be a biomediator or marker of inflammation in the pathogenesis of MetS, and the sequelae of CVD and T2DM.

Serum Carnitine Metabolites and Incident Type 2 Diabetes Mellitus in Patients With Suspected Stable Angina Pectoris

CONTEXT

Carnitine and its metabolites are centrally involved in fatty acid metabolism. Although elevated circulating concentrations have been observed in obesity and insulin resistance, prospective studies examining whether these metabolites are associated with incident type 2 diabetes mellitus (T2D) are sparse.

OBJECTIVE

We performed a comprehensive evaluation of metabolites along the carnitine pathway relative to incident T2D.

DESIGN

A total of 2519 patients (73.1% men) with coronary artery disease, but without T2D, were followed for median 7.7 years until the end of 2009, during which 173 (6.9%) new cases of T2D were identified. Serum levels of free carnitine, its precursors trimethyllysine (TML) and γ-butyrobetaine, and the esters acetyl-, propionyl-, (iso)valeryl-, octanoyl-, and palmitoylcarnitine were measured by liquid chromatography/tandem mass spectrometry. Risk associations were explored by logistic regression and reported per (log-transformed) standard deviation increment.

RESULTS

Median age at inclusion was 62 years and median body mass index (BMI) 26.0 kg/m2. In models adjusted for age, sex, fasting status, BMI, estimated glomerular filtration rate, glycated hemoglobin A1c, triglyceride and high-density lipoprotein cholesterol levels, and study center, serum levels of TML and palmitoylcarnitine associated positively [odds ratio (95% confidence interval), 1.22 (1.04 to 1.43) and 1.24 (1.04 to 1.49), respectively], whereas γ-butyrobetaine associated negatively [odds ratio (95% confidence interval) 0.81 (0.66 to 0.98)] with T2D risk.

CONCLUSION

Serum levels of TML, γ-butyrobetaine, and the long-chained palmitoylcarnitine predict long-term risk of T2D independently of traditional risk factors, possibly reflecting dysfunctional fatty acid metabolism in patients susceptible to T2D development.

Effects of L-carnitine supplementation on biomarkers of oxidative stress, antioxidant capacity and lipid profile, in patients with pemphigus vulgaris: a randomized, double-blind, placebo-controlled trial

BACKGROUND/OBJECTIVES

Pemphigus vulgaris (PV), as an autoimmune disease including mucosa and the skin, is associated with several complications and comorbidities. The present study planned to determine the effect of L-carnitine (LC) supplementation on biomarkers of oxidative stress (OS), antioxidant capacity and lipid profile in PV patients.Subjects/MethodsFifty two control and patients with PV, participated in the current randomized, double-blind, placebo-controlled clinical trial. The patients were allocated randomly to receive 2 g per day LC tartrate subdivided into two equal doses of 1 g before breakfast and dinner (n=26) or placebo (n=26) for 8 weeks. Anthropometric, lipid profile and OS values were determined at baseline and end of intervention period.

RESULTS

LC intake significantly reduced serum levels of triglycerides, total-, LDL- cholesterol and oxidative stress index (OSI; P<0.05). In addition, supplementation with LC resulted to a meaningful increase in levels of total antioxidant capacity (TAC) (P=0.05) and serum carnitine (P<0.001). LC intake revealed non-significant change in serum total oxidant capacity (P=0.15) and HDL- cholesterol (P=0.06) in comparison to the placebo.

CONCLUSIONS

LC consumption may have favorable results on TAC, OSI and lipid profiles in patients with PV. The results were in line with the idea that LC supplementation can be associated with positive effects on metabolic status and OS of patients with PV.European Journal of Clinical Nutrition advance online publication, 23 August 2017; doi:10.1038/ejcn.2017.131.

Serum Acylcarnitines and Risk of Cardiovascular Death and Acute Myocardial Infarction in Patients With Stable Angina Pectoris

Background

Excess levels of serum acylcarnitines, which are intermediate products in metabolism, have been observed in metabolic diseases such as type 2 diabetes mellitus. However, it is not known whether acylcarnitines may prospectively predict risk of cardiovascular death or acute myocardial infarction in patients with stable angina pectoris.

Methods and Results

This study included 4164 patients (median age, 62 years; 72% men). Baseline serum acetyl‐, octanoyl‐, palmitoyl‐, propionyl‐, and (iso)valerylcarnitine were measured using liquid chromatography/tandem mass spectrometry. Hazard ratios (HRs) and 95% CIs for quartile 4 versus quartile 1 are reported. The multivariable model included age, sex, body mass index, fasting status, current smoking, diabetes mellitus, apolipoprotein A1, apolipoprotein B, creatinine, left ventricular ejection fraction, extent of coronary artery disease, study center, and intervention with folic acid or vitamin B6. During median 10.2 years of follow‐up, 10.0% of the patients died of cardiovascular disease and 12.8% suffered a fatal or nonfatal acute myocardial infarction. Higher levels of the even‐chained acetyl‐, octanoyl‐, and palmitoyl‐carnitines were significantly associated with elevated risk of cardiovascular death, also after multivariable adjustments (HR [95% CI]: 1.52 [1.12, 2.06]; P=0.007; 1.73 [1.23, 2.44]; P=0.002; and 1.61 [1.18, 2.21]; P=0.003, respectively), whereas their associations with acute myocardial infarction were less consistent.

Conclusions

Among patients with suspected stable angina pectoris, elevated serum even‐chained acylcarnitines were associated with increased risk of cardiovascular death and, to a lesser degree with acute myocardial infarction, independent of traditional risk factors.

Clinical Trial Registration

URL: http://www.clinicaltrials.gov. Unique identifier: NCT00354081.

Metabolic Effects of a 24-Week Energy-Restricted Intervention Combined with Low or High Dairy Intake in Overweight Women: An NMR-Based Metabolomics Investigation

We investigated the effect of a 24-week energy-restricted intervention with low or high dairy intake (LD or HD) on the metabolic profiles of urine, blood and feces in overweight/obese women by NMR spectroscopy combined with ANOVA-simultaneous component analysis (ASCA). A significant effect of dairy intake was found on the urine metabolome. HD intake increased urinary citrate, creatinine and urea excretion, and decreased urinary excretion of trimethylamine-N-oxide (TMAO) and hippurate relative to the LD intake, suggesting that HD intake was associated with alterations in protein catabolism, energy metabolism and gut microbial activity. In addition, a significant time effect on the blood metabolome was attributed to a decrease in blood lipid and lipoprotein levels due to the energy restriction. For the fecal metabolome, a trend for a diet effect was found and a series of metabolites, such as acetate, butyrate, propionate, malonate, cholesterol and glycerol tended to be affected. Overall, even though these effects were not accompanied by a higher weight loss, the present metabolomics data reveal that a high dairy intake is associated with endogenous metabolic effects and effects on gut microbial activity that potentially impact body weight regulation and health. Moreover, ASCA has a great potential for exploring the effect of intervention factors and identifying altered metabolites in a multi-factorial metabolomic study.

Short-term beef consumption promotes systemic oxidative stress, TMAO formation and inflammation in rats, and dietary fat content modulates these effects

High beef consumption induces oxidative stress in gastrointestinal mucosae and extra-gastrointestinal organs such as the heart and kidneys.

Effect of renal impairment on atherosclerosis: only partially mediated by homocysteine

BACKGROUND

Cardiovascular risk and plasma total homocysteine (tHcy) are high in patients with renal failure. High tHcy may account for a substantial part of the increased risk. We assessed mediation by tHcy of the association of estimated glomerular filtration rate (eGFR CKD/EPI) with carotid total plaque area (TPA) and carotid stenosis.

METHODS

TPA and carotid stenosis were measured by ultrasound. Multiple linear regression was used to assess the effects of eGFR and/or tHcy after adjustment for age, sex, systolic blood pressure (SBP), smoking, LDL, HDL and weight.

RESULTS

Complete data were available for 1967 patients. eGFR decreased, and TPA and total stenosis increased linearly with age. After adjustment [age, sex, SBP, smoking (in pack years), low-density lipoprotein (LDL), high-density lipoprotein (HDL) and weight], eGFR and tHcy were independently associated with TPA (P < 0.01), but when both were added to the model, their significance was attenuated (P = 0.06 for eGFR, 0.03 for tHcy). Mediation analysis showed that tHcy seems to contribute to a significant mediation of the association of eGFR with TPA but not stenosis; after adjustment for the set of risk factors listed above, tHcy still demonstrated significant mediation on TPA (P = 0.03), but not on stenosis (P = 0.16).

CONCLUSIONS

tHcy accounts for a significant part, but not all of the effect of renal impairment on atherosclerosis. Other uremic toxins including metabolic products of the intestinal microbiome may explain residual effects of renal failure on atherosclerosis. Therapeutic approaches arising from that hypothesis are discussed.

Nature and nurture in atherosclerosis: The roles of acylcarnitine and cell membrane-fatty acid intermediates

Macrophages recycle components of dead cells, including cell membranes. When quantities of lipids from cell membranes of dead cells exceed processing capacity, phospholipid and cholesterol debris accumulate as atheromas. Plasma lipid profiles, particularly HDL and LDL cholesterol, are important tools to monitor atherosclerosis risk. Membrane lipids are exported, as triglycerides or phospholipids, or as cholesterol or cholesterol esters, via lipoproteins for disposal, for re-use in cell membranes, or for fat storage. Alternative assays evaluate other aspects of lipid pathology. A key process underlying atherosclerosis is backup of macrophage fatty acid catabolism. This can be quantified by accumulation of acylcarnitine intermediates in extracellular fluid, a direct assay of adequacy of β-oxidation to deal with membrane fatty acid recycling. Further, membranes of somatic cells, such as red blood cells (RBC), incorporate fatty acids that reflect dietary intake. Changes in RBC lipid composition occur within days of ingesting modified fats. Since diets with high saturated fat content or artificial trans-fatty acids promote atherosclerosis, RBC lipid content shifts occur with atherosclerosis, and can show cellular adaptation to pathologically stiff membranes by increased long-chain doubly unsaturated fatty acid production. Additional metabolic changes with atherosclerosis of potential utility include inflammatory cytokine production, modified macrophage signaling pathways, and altered lipid-handling enzymes. Even after atherosclerotic lesions appear, approaches to minimize macrophage overload by reducing rate of fat metabolism are promising. These include preventive measures, and drugs including statins and the newer PCSK9 inhibitors. New cell-based biochemical and cytokine assays provide data to prevent or monitor atherosclerosis progression.

Oxidative stress: New insights on the association of non-alcoholic fatty liver disease and atherosclerosis

Non-alcoholic fatty liver disease (NAFLD) represents the most common and emerging chronic liver disease worldwide. It includes a wide spectrum of liver diseases ranging from simple fatty liver to non-alcoholic steatohepatitis (NASH), which may progress to fibrosis and more severe liver complications such as cirrhosis, hepatocellular carcinoma and liver mortality. NAFLD is strongly associated with obesity, insulin resistance, hypertension, and dyslipidaemia, and is now regarded as the liver manifestation of the metabolic syndrome. The increased mortality of patients with NAFLD is primarily a result of cardiovascular disease and, to a lesser extent, to liver related diseases. Increased oxidative stress has been reported in both patients with NAFLD and patient with cardiovascular risk factors. Thus, oxidative stress represents a shared pathophysiological disorder between the two conditions. Several therapeutic strategies targeting oxidative stress reduction in patients with NAFLD have been proposed, with conflicting results. In particular, vitamin E supplementation has been suggested for the treatment of non-diabetic, non-cirrhotic adults with active NASH, although this recommendation is based only on the results of a single randomized controlled trial. Other antioxidant treatments suggested are resveratrol, silybin, L-carnitine and pentoxiphylline. No trial so far, has evaluated the cardiovascular effects of antioxidant treatment in patients with NAFLD. New, large-scale studies including as end-point also the assessment of the atherosclerosis markers are needed.

Carnitine in bacterial physiology and metabolism

Carnitine is a quaternary amine compound found at high concentration in animal tissues, particularly muscle, and is most well studied for its contribution to fatty acid transport into mitochondria. In bacteria, carnitine is an important osmoprotectant, and can also enhance thermotolerance, cryotolerance and barotolerance. Carnitine can be transported into the cell or acquired from metabolic precursors, where it can serve directly as a compatible solute for stress protection or be metabolized through one of a few distinct pathways as a nutrient source. In this review, we summarize what is known about carnitine physiology and metabolism in bacteria. In particular, recent advances in the aerobic and anaerobic metabolic pathways as well as the use of carnitine as an electron acceptor have addressed some long-standing questions in the field.

New aspects on the metabolic role of intestinal microbiota in the development of atherosclerosis

Gut microbiota remains a very interesting, yet largely unexplored ecosystem inside the human organism. The importance of this ecosystem for the physiology and the pathophysiology of the organism is being slowly unraveled. Recent studies reveal a connection between intestinal microbiota and atherosclerosis development. It seems that alterations in the function and composition of this bacterial population lead through complex mechanisms to a high risk for atherosclerosis. Although these mechanisms remain largely unknown, published studies show that microbiota can lead to atherosclerosis either by augmenting known risk factors or via other, more "direct" mechanisms. This review article summarizes the available literature regarding this matter.

Effects of L-carnitine supplementation on oxidative stress and antioxidant enzymes activities in patients with coronary artery disease: a randomized, placebo-controlled trial

BACKGROUND

Cardiovascular disease is the leading cause of death worldwide. Higher oxidative stress may contribute to the pathogenesis of coronary artery disease (CAD). The purpose of this study was to investigate the effect of L-carnitine (LC, 1000 mg/d) on the markers of oxidative stress and antioxidant enzymes activities in CAD patients.

METHODS

We enrolled 47 CAD patients in the study. The CAD patients were identified by cardiac catheterization as having at least 50% stenosis of one major coronary artery. The subjects were randomly assigned to the placebo (n = 24) and LC (n = 23) groups. The intervention was administered for 12 weeks. The levels of serum LC, plasma malondialdehyde (MDA), and erythrocyte antioxidant enzymes activities [catalase (CAT), superoxide dismutase (SOD), glutathione peroxidase (GPx)] were measured before and after intervention.

RESULTS

Thirty-nine subjects completed the study (placebo, n = 19; LC, n = 20). After 12 weeks of LC supplementation, the level of MDA was significantly reduced (2.0 ± 0.3 to 1.8 ± 0.3 μmol/L, P = 0.02) and the level of LC (33.6 ± 13.6 to 40.0 ± 12.0 μmol/L, P = 0.04) and antioxidant enzymes activities [CAT (12.7 ± 5.5 to 13.1 ± 5.8 U/mg of protein, P = 0.02), SOD (14.8 ± 2.9 to 20.7 ± 5.8 U/mg of protein, P < 0.01), and GPx (20.3 ± 3.4 to 23.0 ± 3.1 U/mg of protein, P = 0.01)] were significantly increased. The level of LC was significantly positively correlated with the antioxidant enzymes activities (CAT, β = 0.87, P = 0.02; SOD, β = 0.72, P < 0.01).

CONCLUSION

LC supplementation at a dose of 1000 mg/d was associated with a significant reduction in oxidative stress and an increase in antioxidant enzymes activities in CAD patients. CAD patients might benefit from using LC supplements to increase their anti-oxidation capacity.

TRIAL REGISTRATION

Clinical Trials.gov Identifier: NCT01819701.