Role of carnitine in the regulation of glucose homeostasis and insulin sensitivity: evidence from in vivo and in vitro studies with carnitine supplementation and carnitine deficiency

Adding L-carnitine to antagonist ovarian stimulation doesn't improve the outcomes of IVF/ ICSI cycle in patients with polycystic ovarian syndrome: a double-blind randomized clinical trial

OBJECTIVE

To investigate the effect of L-carnitine supplementation during the controlled ovarian stimulation (COS) cycle with antagonist protocol in patients with polycystic ovary syndrome (PCOS) diagnosis undergoing IVF/ICSI treatment.

METHODS AND MATERIALS

This was a double-blind clinical trial study including 110 patients with PCOS attended to Royan Institute between March 2020 and February 2023. At the beginning of the COS cycle, the eligible patients were allocated into two groups randomly according to the coding list of the drugs prepared by the statistical consultant. In the experimental group, patients received 3 tablets daily (L-carnitine 1000 mg) from the second day of menstruation of the previous cycle until the puncture day in the cases of freeze-all embryos (6 weeks) or until the day of the pregnancy test (8 weeks) in fresh embryo transfer cycle. In the control group, patients received 3 placebo tablets for the same period of time. Weight assessment and fasting blood sugar and insulin tests, as well as serum lipid profile were also measured at the baseline and ovum pick-up day. The results of the COS cycle as well as the implantation and pregnancy rates were compared between groups.

RESULTS

Finally, 45 cases in L-carnitine group versus 47 cases in the placebo group were completed study per protocol. Data analysis showed that the two groups were homogeneous in terms of demographic characteristics and baseline laboratory tests and severity of PCOS. There is no statistically significant difference in terms of the oocyte recovery ratio and oocyte maturity rate, and the number and quality of embryos, as well as the rates of the fertilization, chemical and clinical pregnancy between groups. However, the means of weight (P < 0.001) and serum levels of fasting blood sugar (P = 0.021), fasting insulin (P = 0.004), triglyceride (P < 0.001) and cholesterol (P < 0.001), LDL (P < 0.001) have significantly decreased in women after consuming L-carnitine supplementation.

CONCLUSION

The oral intake of L-carnitine during COS in PCOS women for 6 weeks had no effect on COS and pregnancy outcomes. However, taking this supplement for 6 weeks has been associated with weight loss and improved lipid profile and serum glucose.

TRIAL REGISTRATION

The study was registered in the Clinicaltrials.gov site on December 17, 2020 (NCT04672720).

Ameliorating effects of L-carnitine and synbiotic co-supplementation on anthropometric measures and cardiometabolic traits in women with obesity: a randomized controlled clinical trial

Background

Obesity, a multifactorial disorder with pandemic dimensions, is conceded a major culprit of morbidity and mortality worldwide, necessitating efficient therapeutic strategies. Nutraceuticals and functional foods are considered promising adjuvant/complementary approaches for weight management in individuals with obesity who have low adherence to conventional treatments. Current literature supports the weight-reducing efficacy of pro/pre/synbiotics or L-carnitine; however, the superiority of the nutraceutical joint supplementation approach over common single therapies to counter obesity and accompanying comorbidities is well documented. This study was designed to assess the effects of L-carnitine single therapy compared with L-carnitine and multistrain/multispecies synbiotic co-supplementation on anthropometric and cardiometabolic indicators in women with obesity.

Methods

The current placebo-controlled double-blind randomized clinical trial was performed on 46 women with obesity, randomly allocated to either concomitant supplementation [L-carnitine tartrate (2 × 500 mg/day) + multistrain/multispecies synbiotic (1 capsule/day)] or monotherapy [L-carnitine tartrate (2 × 500 mg/day) + maltodextrin (1 capsule/day)] groups for 8 weeks. Participants in both groups received healthy eating dietary advice.

Results

Anthropometric, lipid, and glycemic indices significantly improved in both intervention groups; however, L-carnitine + synbiotic co-administration elicited a greater reduction in the anthropometric measures including body mass index (BMI), body weight, and neck, waist, and hip circumferences (p < 0.001, <0.001, <0.001, = 0.012, and =0.030, respectively) after adjusting for probable confounders. Moreover, L-carnitine + synbiotic joint supplementation resulted in a greater reduction in fasting blood sugar (FBS), insulin (though marginal), and homeostatic model assessment of insulin resistance (HOMA-IR) and more increment in quantitative insulin sensitivity check index (QUICKI; p = 0.014, 0.051, 0.024, and 0.019, respectively) compared with the L-carnitine + placebo monosupplementation. No significant intergroup changes were found for the lipid profile biomarkers, except for a greater increase in high-density lipoprotein-cholesterol concentrations (HDL-C) in the L-carnitine + synbiotic group (p = 0.009).

Conclusion

L-carnitine + synbiotic co-supplementation was more beneficial in ameliorating anthropometric indices as well as some cardiometabolic parameters compared with L-carnitine single therapy, suggesting that it is a promising adjuvant approach to ameliorate obesity or associated metabolic complications through potential synergistic or complementary mechanisms. Further longer duration clinical trials in a three-group design are demanded to verify the complementary or synergistic mechanisms.

Clinical trial registration

www.irct.ir, Iranian Registry of Clinical Trials IRCT20080904001197N13.

Molecular pathways and nutrigenomic review of insulin resistance development in gestational diabetes mellitus

Gestational diabetes mellitus is a condition marked by raised blood sugar levels and insulin resistance that usually occurs during the second or third trimester of pregnancy. According to the World Health Organization, hyperglycemia affects 16.9% of pregnancies worldwide. Dietary changes are the primarily alternative treatment for gestational diabetes mellitus. This paper aims to perform an exhaustive overview of the interaction between diet, gene expression, and the metabolic pathways related to insulin resistance. The intake of foods rich in carbohydrates can influence the gene expression of glycolysis, as well as foods rich in fat, can disrupt the beta-oxidation and ketogenesis pathways. Furthermore, vitamins and minerals are related to inflammatory processes regulated by the TLR4/NF-κB and one carbon metabolic pathways. We indicate that diet regulated gene expression of PPARα, NOS, CREB3L3, IRS, and CPT I, altering cellular physiological mechanisms and thus increasing or decreasing the risk of gestational diabetes. The alteration of gene expression can cause inflammation, inhibition of fatty acid transport, or on the contrary help in the modulation of ketogenesis, improve insulin sensitivity, attenuate the effects of glucotoxicity, and others. Therefore, it is critical to comprehend the metabolic changes of pregnant women with gestational diabetes mellitus, to determine nutrients that help in the prevention and treatment of insulin resistance and its long-term consequences.

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

Introduction

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

Methods

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

Results

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

Conclusion

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

Effect of exogenous l-carnitine on aortic stiffness in dyslipidemic adolescents: Design of a quadruple-blind, randomized, controlled interventional trial

Background

Atherosclerotic cardiovascular disease (ASCVD) risk factors including vascular remodeling leading to hypertension and dyslipidemia are prevalent among children and adolescents. Conflicting observational and Mendelian randomization data suggest endogenous carnitine may affect arterial stiffness and lipid traits. Because of this, we developed a study to evaluate the causal role for carnitine in arterial stiffness at a point when the lifecourse trajectory to hypertension can be modified.

Methods

This study is a mechanistic, double-blinded, randomized control trial (RCT) in 166 adolescents with dyslipidemia for the effect of 6 months of maximum dose 3 g daily oral l-carnitine supplementation (CS+) versus placebo (CS-) on aortic stiffness measured as carotid-femoral pulse wave velocity (CFPWV) and pulse pressure (PP); lipid concentrations (total cholesterol, HDL-C, triglycerides, and LDL-C) and serum fatty acid oxidation biomarkers by metabolomic analysis.

Conclusions

The simultaneous evaluation of endogenous carnitine genetic effects and exogenous l-carnitine supplementation may facilitate future therapies for youth with cardiometabolic derangement to arrest atherosclerotic changes.

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

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

l-carnitine: Nutrition, pathology, and health benefits

Carnitine is a medically needful nutrient that contributes in the production of energy and the metabolism of fatty acids. Bioavailability is higher in vegetarians than in people who eat meat. Deficits in carnitine transporters occur as a result of genetic mutations or in combination with other illnesses such like hepatic or renal disease. Carnitine deficit can arise in diseases such endocrine maladies, cardiomyopathy, diabetes, malnutrition, aging, sepsis, and cirrhosis due to abnormalities in carnitine regulation. The exogenously provided molecule is obviously useful in people with primary carnitine deficits, which can be life-threatening, and also some secondary deficiencies, including such organic acidurias: by eradicating hypotonia, muscle weakness, motor skills, and wasting are all improved l-carnitine (LC) have reported to improve myocardial functionality and metabolism in ischemic heart disease patients, as well as athletic performance in individuals with angina pectoris. Furthermore, although some intriguing data indicates that LC could be useful in a variety of conditions, including carnitine deficiency caused by long-term total parenteral supplementation or chronic hemodialysis, hyperlipidemias, and the prevention of anthracyclines and valproate-induced toxicity, such findings must be viewed with caution.

Associated long-term effects of decabromodiphenyl ethane on the gut microbial profiles and metabolic homeostasis in Sprague-Dawley rat offspring

Decabromodiphenyl ethane (DBDPE) as a widely used brominated flame retardant is harmful to human health due to its toxicity, including cardiovascular toxicity, reproductive toxicity, and hepatotoxicity. However, the knowledge of the long-term effects and structural and metabolic function influence on gut microbiota from DBDPE exposure remains limited. This study was mainly aimed at the gut microbiome and fecal metabolome of female rats and their offspring exposed to DBDPE in early life. 16S rRNA gene sequencing demonstrated that maternal DBDPE exposure could increase the α-diversity of gut microbiota in immature offspring while decreasing the abundance of Bifidobacterium, Clostridium, Muribaculum, Escherichia, and Lactobacillus in adult offspring. The nonmetric multidimensional scaling showed a consistency in the alternation of β-diversity between pregnant rats and their adult offspring. Furthermore, the short-chain fatty acids produced by gut microbiota dramatically increased in adult offspring after maternal DBDPE exposure, revealing that DBDPE treatment disrupted the gut microbial compositions and altered the gut community's metabolic functions. Untargeted metabolomics identified 41 differential metabolites and seven metabolic pathways between adult offspring from various groups. Targeted metabolomic showed that maternal high dose DBDPE exposure obviously decreased the level of glutathione, taurine, and l-carnitine in their adult offspring, which verified the correlation between weight loss and amino acid metabolites. An interesting link between some gut bacteria (especially the Firmicutes) and fecal metabolites demonstrated the shifts in gut microbiota may drive the metabolic process of fecal metabolites. The current findings provide new insight into long-term effects on human health.

The effects of L-carnitine supplementation on glycemic markers in adults: A systematic review and dose-response meta-analysis

Background and aims

Hyperglycemia and insulin resistance are concerns today worldwide. Recently, L-carnitine supplementation has been suggested as an effective adjunctive therapy in glycemic control. Therefore, it seems important to investigate its effect on glycemic markers.

Methods

PubMed, Scopus, Web of Science, and the Cochrane databases were searched in October 2022 for prospective studies on the effects of L-carnitine supplementation on glycemic markers. Inclusion criteria included adult participants and taking oral L-carnitine supplements for at least seven days. The pooled weighted mean difference (WMD) was calculated using a random-effects model.

Results

We included the 41 randomized controlled trials (RCTs) (n = 2900) with 44 effect sizes in this study. In the pooled analysis; L-carnitine supplementation had a significant effect on fasting blood glucose (FBG) (mg/dl) [WMD = -3.22 mg/dl; 95% CI, -5.21 to -1.23; p = 0.002; I ² = 88.6%, p < 0.001], hemoglobin A1c (HbA1c) (%) [WMD = -0.27%; 95% CI, -0.47 to -0.07; p = 0.007; I ² = 90.1%, p < 0.001] and homeostasis model assessment-estimate insulin resistance (HOMA-IR) [WMD = -0.73; 95% CI, -1.21 to -0.25; p = 0.003; I ² = 98.2%, p < 0.001] in the intervention compared to the control group. L-carnitine supplementation had a reducing effect on baseline FBG ≥100 mg/dl, trial duration ≥12 weeks, intervention dose ≥2 g/day, participants with overweight and obesity (baseline BMI 25-29.9 and >30 kg/m²), and diabetic patients. Also, L-carnitine significantly affected insulin (pmol/l), HOMA-IR (%), and HbA1c (%) in trial duration ≥12 weeks, intervention dose ≥2 g/day, and participants with obesity (baseline BMI >30 kg/m²). It also had a reducing effect on HOMA-IR in diabetic patients, non-diabetic patients, and just diabetic patients for insulin, and HbA1c. There was a significant nonlinear relationship between the duration of intervention and changes in FBG, HbA1c, and HOMA-IR. In addition, there was a significant nonlinear relationship between dose (≥2 g/day) and changes in insulin, as well as a significant linear relationship between the duration (weeks) (coefficients = -16.45, p = 0.004) of intervention and changes in HbA1C.

Conclusions

L-carnitine could reduce the levels of FBG, HbA1c, and HOMA-IR.

Systematic review registration

https://www.crd.york.ac.uk/prospero/, identifier: CRD42022358692.

Prolonged Use of Carnitine-Orotate Complex (Godex®) Is Associated with Improved Mortality: A Nationwide Cohort Study

Despite its hepatoprotective effects and favorable metabolic effects, the association between carnitine-orotate complex (Godex®) intake and mortality has never been investigated. We enrolled 13,413 adults who underwent national health examination and were prescribed the carnitine-orotate complex. Subjects were classified into three groups based on duration of using carnitine-orotate complex: <30, 30−180, and ≥180 days and were followed-up until 2019. Hazard ratios (HRs) and 95% confidence intervals (CIs) for all-cause mortality were estimated using Cox proportional hazards regression. During the follow-up period, 708 deaths were documented. Adjusted HR of mortality was 0.69 (95% CI 0.51−0.92) in those who used carnitine-orotate complex for ≥180 days compared to those who used it for <30 days. Use of carnitine-orotate complex for ≥180 days was associated with significantly reduced mortality in individuals with metabolic risk factors such as obesity, metabolic syndrome, dyslipidemia, and fatty liver than the shorter period of use. A significant interaction was observed in individuals with type 2 diabetes (HR 0.43, 95% CI 0.29−0.63, p-value 0.001). In this nationwide study, longer use of carnitine-orotate complex was associated with improved mortality compared to a shorter period of use, and the risk reductions were prominent in individuals with metabolic risk factors.

Association of Systemic Trimethyllysine With Heart Failure With Preserved Ejection Fraction and Cardiovascular Events

CONTEXT

Carnitine has been associated with cardiac energy metabolism and heart failure, but the association between its precursors-trimethyllysine (TML) and γ-butyrobetaine (GBB)-and heart failure with preserved ejection fraction (HFpEF) remains unclear.

OBJECTIVE

To evaluate the relationship between TML-related metabolites and HFpEF in an Asian population.

METHODS

The cross-sectional component of this study examined the association between plasma TML-related metabolites and HFpEF, while a prospective cohort design was applied to examine the association with incident cardiovascular events in HFpEF. Included in the study were 1000 individuals who did not have heart failure (non-HF) and 1413 patients with HFpEF. Liquid chromatography mass spectrometry was used to assess plasma carnitine, GBB, TML and trimethylamine-N-oxide (TMAO) concentrations.

RESULTS

Plasma GBB and TML were both elevated in patients with HFpEF. After adjusting for traditional risk factors and renal function, TML, but not GBB, was significantly associated with HFpEF. The odds ratio (OR) for the fourth vs first quartile of TML was 1.57 (95% CI 1.09-2.27; P-trend < .01). The OR for each SD increment of log-TML was 1.26 (95% CI 1.08-1.47). Plasma TMAO (P-interaction = 0.024) and estimated glomerular filtration rate (P-interaction = 0.024) modified the TML-HFpEF association. The addition of TML improved the diagnostic value under the multivariable model. In the prospective study of patients with HFpEF, higher plasma TML was associated with increased risk of cardiovascular events.

CONCLUSION

Plasma TML concentrations are positively associated with HFpEF, and higher plasma TML indicates increased risk of cardiovascular events.

A Study of the Metabolic Pathways Affected by Gestational Diabetes Mellitus: Comparison with Type 2 Diabetes

BACKGROUND

Gestational diabetes mellitus (GDM) remains incompletely understood and increases the risk of developing Diabetes mellitus type 2 (DM2). Metabolomics provides insights etiology and pathogenesis of disease and discovery biomarkers for accurate detection. Nuclear magnetic resonance (NMR) spectroscopy is a key platform defining metabolic signatures in intact serum/plasma. In the present study, we used NMR-based analysis of macromolecules free-serum to accurately characterize the altered metabolic pathways of GDM and assessing their similarities to DM2. Our findings could contribute to the understanding of the pathophysiology of GDM and help in the identification of metabolomic markers of the disease.

METHODS

Sixty-two women with GDM matched with seventy-seven women without GDM (control group). ¹H NMR serum spectra were acquired on an 11.7 T Bruker Avance DRX NMR spectrometer.

RESULTS

We identified 55 metabolites in both groups, 25 of which were significantly altered in the GDM group. GDM group showed elevated levels of ketone bodies, 2-hydroxybutyrate and of some metabolic intermediates of branched-chain amino acids (BCAAs) and significantly lower levels of metabolites of one-carbon metabolism, energy production, purine metabolism, certain amino acids, 3-methyl-2-oxovalerate, ornithine, 2-aminobutyrate, taurine and trimethylamine N-oxide.

CONCLUSION

Metabolic pathways affected in GDM were beta-oxidation, ketone bodies metabolism, one-carbon metabolism, arginine and ornithine metabolism likewise in DM2, whereas BCAAs catabolism and aromatic amino acids metabolism were affected, but otherwise than in DM2.

Gut and obesity/metabolic disease: Focus on microbiota metabolites

Obesity is often associated with the risk of chronic inflammation and other metabolic diseases, such as diabetes, cardiovascular disease, and cancer. The composition and activity of the gut microbiota play an important role in this process, affecting a range of physiological processes, such as nutrient absorption and energy metabolism. The active gut microbiota can produce a large number of physiologically active substances during the process of intestinal metabolism and reproduction, including short‐chain/long‐chain fatty acids, secondary bile acids, and tryptophan metabolites with beneficial effects on metabolism, as well as negative metabolites, including trimethylamine N‐oxide, delta‐valerobetaine, and imidazole propionate. How gut microbiota specifically affect and participate in metabolic and immune activities, especially the metabolites directly produced by gut microbiota, has attracted extensive attention. So far, some animal and human studies have shown that gut microbiota metabolites are correlated with host obesity, energy metabolism, and inflammation. Some pathways and mechanisms are slowly being discovered. Here, we will focus on the important metabolites of gut microbiota (beneficial and negative), and review their roles and mechanisms in obesity and related metabolic diseases, hoping to provide a new perspective for the treatment and remission of obesity and other metabolic diseases from the perspective of metabolites.

Metabolic signatures of insulin resistance in non-diabetic individuals

BACKGROUND

Insulin resistance (IR) evolved from excessive energy intake and poor energy expenditure, affecting the patient's quality of life. Amino acid and acylcarnitine metabolomic profiles have identified consistent patterns associated with metabolic disease and insulin sensitivity. Here, we have measured a wide array of metabolites (30 acylcarnitines and 20 amino acids) with the MS/MS and investigated the association of metabolic profile with insulin resistance.

METHODS

The study population (n = 403) was randomly chosen from non-diabetic participants of the Surveillance of Risk Factors of NCDs in Iran Study (STEPS 2016). STEPS 2016 is a population-based cross-sectional study conducted periodically on adults aged 18-75 years in 30 provinces of Iran. Participants were divided into two groups according to the optimal cut-off point determined by the Youden index of HOMA-IR for the diagnosis of metabolic syndrome. Associations were investigated using regression models adjusted for age, sex, and body mass index (BMI).

RESULTS

People with high IR were significantly younger, and had higher education level, BMI, waist circumference, FPG, HbA1c, ALT, triglyceride, cholesterol, non-HDL cholesterol, uric acid, and a lower HDL-C level. We observed a strong positive association of serum BCAA (valine and leucine), AAA (tyrosine, tryptophan, and phenylalanine), alanine, and C0 (free carnitine) with IR (HOMA-IR); while C18:1 (oleoyl L-carnitine) was inversely correlated with IR.

CONCLUSIONS

In the present study, we identified specific metabolites linked to HOMA-IR that improved IR prediction. In summary, our study adds more evidence that a particular metabolomic profile perturbation is associated with metabolic disease and reemphasizes the significance of understanding the biochemistry and physiology which lead to these associations.

Measures of insulin sensitivity, leptin, and adiponectin concentrations in cats in diabetic remission compared to healthy control cats

Objectives

Firstly, to compare differences in insulin, adiponectin, leptin, and measures of insulin sensitivity between diabetic cats in remission and healthy control cats, and determine whether these are predictors of diabetic relapse. Secondly, to determine if these hormones are associated with serum metabolites known to differ between groups. Thirdly, if any of the hormonal or identified metabolites are associated with measures of insulin sensitivity.

Animals

Twenty cats in diabetic remission for a median of 101 days, and 21 healthy matched control cats.

Methods

A casual blood glucose measured on admission to the clinic. Following a 24 h fast, a fasted blood glucose was measured, and blood sample taken for hormone (i.e., insulin, leptin, and adiponectin) and untargeted metabolomic (GC-MS and LC-MS) analysis. A simplified IVGGT (1 g glucose/kg) was performed 3 h later. Cats were monitored for diabetes relapse for at least 9 months (270 days).

Results

Cats in diabetic remission had significantly higher serum glucose and insulin concentrations, and decreased insulin sensitivity as indicated by an increase in HOMA and decrease in QUICKI and Bennett indices. Leptin was significantly increased, but there was no difference in adiponectin (or body condition score). Several significant correlations were found between insulin sensitivity indices, leptin, and serum metabolites identified as significantly different between remission and control cats. No metabolites were significantly correlated with adiponectin. No predictors of relapse were identified in this study.

Conclusion and clinical importance

Insulin resistance, an underlying factor in diabetic cats, persists in diabetic remission. Cats in remission should be managed to avoid further exacerbating insulin resistance.

Serum L-Carnitine Levels Are Associated With First Stroke in Chinese Adults With Hypertension

BACKGROUND

This study aimed to evaluate the association of serum L-carnitine with first stroke and explore potential effect modifiers.

METHODS

This is a nested, case-control study drawn from the China Stroke Primary Prevention Trial among rural Chinese adults with hypertension, including 557 first stroke cases and 557 age-matched, sex-matched, treatment group-matched, and residence-matched controls. Serum L-carnitine was measured by liquid chromatography with tandem quadrupole mass spectrometry. Multiple conditional logistic regression models were used to evaluate the association between L-carnitine and first stroke.

RESULTS

The mean level of serum L-carnitine in the stroke population was 4.7 μg/mL, which was significantly lower than that of the control group (5.7 μg/mL). When L-carnitine was assessed as quintiles, compared with the reference group (quintile 1, <3.3 μg/mL), the odds of stroke were 0.62 (95% CI, 0.39-1.00) in quintile 2, 0.66 (95% CI, 0.40-1.10) in quintile 3, 0.47 (95% CI, 0.28-0.81) in quintile 4, and 0.50 (95% CI, 0.30-0.84) in quintile 5. The trend test was significant (P=0.01). When quintiles 2 to 5 were combined, the adjusted odds ratio of first stroke was 0.58 (95% CI, 0.38-0.87) compared with quintile 1. Similar associations were found for ischemic stroke and hemorrhagic stroke. In subgroup analysis, a significant L-carnitine-stroke association was only observed in the normal folate group (P interaction, 0.039) and in the MTHFR CC genotype group (P interaction, 0.047).

CONCLUSIONS

In this study of rural Chinese adults with hypertension, serum L-carnitine had an inverse but nonlinear association with first stroke. Folate status and the MTHFR C677T variant were significant effect modifiers of the association.

Impact of l-Carnitine Supplementation on Liver Enzyme Normalization in Patients with Chronic Liver Disease: A Meta-Analysis of Randomized Trials

The effectiveness of l-carnitine in chronic liver disease remains controversial. We conducted this meta-analysis to assess the efficacy of various forms of l-carnitine in the treatment of chronic liver disease. Methods: We searched the Cochrane Library, EMBASE, KMBASE, and Medline databases for all relevant studies published until April 2022 that examined the ability of l-carnitine or its derivatives to normalize liver enzymes in patients with chronic liver disease. We performed meta-analyses of the proportion of patients with alanine aminotransferase (ALT) normalization and post-treatment serum aspartate aminotransferase (AST) and ALT levels. A random effects model was used for meta-analyses. Results: Fourteen randomized controlled trials (1217 patients) were included in this meta-analysis. The proportion of patients in whom ALT normalized was higher in the carnitine-orotate treatment group than in the control group (pooled odds ratio (OR), 95% confidence interval (CI) = 4.61 (1.48–14.39)). The proportion of patients in whom ALT normalized was also higher among those who received the carnitine-orotate complex, a combination of carnitine-orotate, biphenyl dimethyl dicarboxylate, and other minor supplementary compounds than in those who did not without significant heterogeneity (pooled OR (95% CI) = 18.88 (7.70–46.27); df = 1; p = 0.51; I² = 0%). l-carnitine supplementation effectively lowered serum ALT levels compared to controls (pooled mean difference (95% CI) = −11.99 (−22.48 to −1.49)). Conclusions: l-carnitine supplementation significantly lowered ALT and AST levels and normalized ALT levels in patients with chronic liver disease.

Carnitines as Mitochondrial Modulators of Oocyte and Embryo Bioenergetics

Recently, the importance of bioenergetics in the reproductive process has emerged. For its energetic demand, the oocyte relies on numerous mitochondria, whose activity increases during embryo development under a fine regulation to limit ROS production. Healthy oocyte mitochondria require a balance of pyruvate and fatty acid oxidation. Transport of activated fatty acids into mitochondria requires carnitine. In this regard, the interest in the role of carnitines as mitochondrial modulators in oocyte and embryos is increasing. Carnitine pool includes the un-esterified l-carnitine (LC) and carnitine esters, such as acetyl-l-carnitine (ALC) and propionyl-l-carnitine (PLC). In this review, carnitine medium supplementation for counteracting energetic and redox unbalance during in vitro culture and cryopreservation is reported. Although most studies have focused on LC, there is new evidence that the addition of ALC and/or PLC may boost LC effects. Pathways activated by carnitines include antiapoptotic, antiglycative, antioxidant, and antiinflammatory signaling. Nevertheless, the potential of carnitine to improve energetic metabolism and oocyte and embryo competence remains poorly investigated. The importance of carnitine as a mitochondrial modulator may suggest that this molecule may exert a beneficial role in ovarian disfunctions associated with metabolic and mitochondrial alterations, including PCOS and reproductive aging.

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

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

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

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

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

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

L-carnitine supplementation ameliorates insulin resistance in critically ill acute stroke patients: a randomized, double-blinded, placebo-controlled clinical trial

Background and purpose

Insulin resistance (IR) can negatively affect clinical outcomes in acute ischemic stroke (IS) patients. Safe and cost-saving interventions are still needed to improve glycemic indices in this population. The primary objective was to evaluate L-carnitine (LC) effects in acute IS patients' homeostatic model assessment of IR (HOMA-IR).

Experimental approach

In this randomized, double-blind placebo-controlled clinical trial, critically ill IS patients were allocated to receive daily oral L-carnitine (1.5 g) or a placebo for six days. Fasting serum levels of glucose, insulin, C-reactive protein, LC, and HOMA-IR were measured on days 1 and 7. Mechanical ventilation duration, ICU/hospital duration, illness severity score, sepsis, and death events were assessed.

Findings/Results

Forty-eight patients were allocated to the research groups, 24 patients in each group, and all were included in the final analysis. LC administration showed a decrease in mean difference of HOMA-IR and insulin levels at day 7 compared to placebo, -0.94 ± 1.92 vs 0.87 ± 2.24 (P = 0.01) and -2.26 ± 6.81 vs 0.88 ± 4.95 (P = 0.03), respectively. However, LC administration did not result in significant improvement in clinical outcomes compared to placebo. The short duration of intervention and low sample size limited our results.

Conclusion and implication

Supplementation of L-carnitine improved HOMA-IR index in acute IS patients admitted to the critical care unit. Supplementation of LC would be a potential option to help to control IR in critically ill acute IS patients.

Effect of l-carnitine supplementation on liver fat content and cardiometabolic indices in overweight/obese women with polycystic ovary syndrome: A randomized controlled trial

BACKGROUND

Polycystic ovary syndrome (PCOS) is a common endocrine disorder among reproductive-age women, and is associated with cardiovascular diseases as well as non-alcoholic fatty liver disease. The recent evidence suggested the beneficial effects of l-carnitine in women with PCOS.

OBJECTIVE

The present study aimed to investigate the effect of l-carnitine supplementation on liver fat content and cardiometabolic outcomes in overweight/obese women with PCOS.

METHODS

The present study was designed as a 12-week double-blind, randomized controlled clinical trial. Sixty-two overweight/obese women with PCOS were assigned into the treatment (received 1000 mg/d l-carnitine capsule) and the control (received placebo capsule) groups. The outcomes included lipid accumulation product (LAP), atherogenic index of plasma (AIP), atherogenic coefficient (AC) and Castelli II indices.

RESULTS

At the end of the trial, there was no significant difference between the treatment and the control groups in terms of LAP (-1.1 vs. -4.0; P = 0.45), AIP (0.0 vs. -0.09; P = 0.14), AC (-0.2 vs. -0.8; P = 0.06) and Castelli II index (-0.2 vs. -0.6; P = 0.07) after controlling the mean change of waist circumference.

CONCLUSION

l-carnitine supplementation for 12 weeks has no beneficial effect on liver fat content and cardiometabolic outcomes in overweight or obese women with PCOS.

TRIAL REGISTRATION

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

Causal Inference of Carnitine on Blood Pressure and potential mediation by uric acid: A mendelian randomization analysis

Background

Dietary change alters blood pressure (BP) but the specific causal dietary elements are unclear. Given previous observational data suggesting serum carnitine or uric acid affect BP, we investigated the role of serum carnitine and serum uric acid concentrations on BP, and considered mediation by lipids and insulin resistance using two-sample bi-directional Mendelian randomization (MR) analysis.

Methods

We performed MR to characterize bi-directional causal relationships of carnitine or uric acid on cardiometabolic traits. We performed two-sample MR using genome-wide association summary data from separate large-scale genomic analyses of carnitine, uric acid, BP, lipids, and glycemic traits. We used inverse variance weighted (IVW) meta-analysis and MR Egger regression to test for causal relations in the absence and presence of pleiotropy, respectively, and performed sensitivity analyses to identify confounders and intermediates.

Results

In our analysis, carnitine was directly, causally associated with systolic BP (IVW effect = 0.2, causal p-value = 0.03) but not diastolic BP (IVW causal p = 0.1). Our findings additionally support direct and indirect relationships of carnitine on TG and on uric acid. No causal associations of carnitine were found with glycemic traits. Uric acid was not associated with BP, nor TG.

Conclusion

Two-sample bi-directional MR demonstrated an unconfounded causal effect of carnitine, but not uric acid, on systolic but not diastolic BP, suggesting a role of carnitine in arterial stiffness. Carnitine, but not uric acid, also has direct and indirect effects on TG but are independent of the causal effect of carnitine on systolic BP.

Microbial metabolite delta-valerobetaine is a diet-dependent obesogen

Obesity and obesity-related metabolic disorders are linked to the intestinal microbiome. However, the causality of changes in the microbiome-host interaction affecting energy metabolism remains controversial. Here, we show the microbiome-derived metabolite δ-valerobetaine (VB) is a diet-dependent obesogen that is increased with phenotypic obesity and is correlated with visceral adipose tissue mass in humans. VB is absent in germ-free mice and their mitochondria but present in ex-germ-free conventionalized mice and their mitochondria. Mechanistic studies in vivo and in vitro show VB is produced by diverse bacterial species and inhibits mitochondrial fatty acid oxidation through decreasing cellular carnitine and mitochondrial long-chain acyl-coenzyme As. VB administration to germ-free and conventional mice increases visceral fat mass and exacerbates hepatic steatosis with a western diet but not control diet. Thus, VB provides a molecular target to understand and potentially manage microbiome-host symbiosis or dysbiosis in diet-dependent obesity.

Nutritional Supplements and Complementary Therapies in Polycystic Ovary Syndrome

Polycystic ovary syndrome (PCOS) affects 1 in 5 women of reproductive age, and is characterized by menstrual irregularities, clinical or biochemical hyperandrogenism, and the presence of polycystic ovary morphology. One of the recommended treatment strategies in the international evidence-based guidelines is lifestyle modification, which includes diet and exercise, with the aim of improving a range of health outcomes. The incurable nature of PCOS reinforces the importance of developing novel and innovative symptomatic relief strategies, which are currently the only available approaches for improving quality of life for these women. Women with PCOS tend to be nutrient deficient in many common vitamins and minerals, thought to be associated with the psychological (depression, anxiety, etc.) and physiological (insulin resistance, diabetes, infertility, etc.) sequelae of the condition. Nutrient supplementation and the integration of complementary medicine as adjuncts to traditional lifestyle-based therapies in PCOS could therefore provide additional benefits to these women. In this review, we synthesize the evidence regarding nutrient supplementation and complementary therapies in PCOS, predominantly from randomized controlled trials, systematic reviews, and meta-analyses, to provide an overview of the state of knowledge in this field. The evidence to date suggests that specific vitamins (B-12, inositols, folate, vitamins D, E, and K), vitamin-like nutrients (bioflavonoids and α-lipoic acid), minerals (calcium, zinc, selenium, and chromium picolinate), and other formulations (melatonin, ω-3 fatty acids, probiotics, and cinnamon), as well as some complementary approaches such as acupuncture and yoga may be beneficial in PCOS. However, there remain areas of uncertainty and key limitations in the literature that must be overcome before these therapies can be integrated into routine clinical practice.

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

PURPOSE

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

METHODS

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

RESULTS

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

CONCLUSION

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

TRIAL REGISTRATION

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

Carnitine Orotate Complex Ameliorates Insulin Resistance and Hepatic Steatosis Through Carnitine Acetyltransferase Pathway

BACKGROUND

Carnitine orotate complex (Godex) has been shown to decrease glycated hemoglobin levels and improve steatosis in patients with type 2 diabetes mellitus with non-alcoholic fatty liver disease. However, the mechanisms of Godex in glucose metabolism remain unclear.

METHODS

Male C57BL/6J mice were divided into four groups: normal-fat diet, high-fat diet, a high-fat diet supplemented with intraperitoneal injection of (500 mg or 2,000 mg/kg/day) Godex for 8 weeks. Computed tomography, indirect calorimetry, and histological analyses including electron microscopy of the liver were performed, and biochemical profiles and oral glucose tolerance test and insulin tolerance test were undertaken. Expressions of genes in the lipid and glucose metabolism, activities of oxidative phosphorylation enzymes, carnitine acetyltransferase, pyruvate dehydrogenase, and acetyl-coenzyme A (CoA)/CoA ratio were evaluated.

RESULTS

Godex improved insulin sensitivity and significantly decreased fasting plasma glucose, homeostatic model assessment for insulin resistance, steatosis, and gluconeogenesis, with a marked increase in fatty acid oxidation as well as better use of glucose in high-fat diet-fed mice. It preserved mitochondrial function and ultrastructure, restored oxidative phosphorylation enzyme activities, decreased acetyl-CoA/CoA ratio, and increased carnitine acetyltransferase content and pyruvate dehydrogenase activity. Carnitine acetyltransferase knockdown partially reversed the effects of Godex in liver and in vitro.

CONCLUSION

Godex improved insulin resistance and steatosis by regulating carnitine acetyltransferase in liver in high-fat diet-fed mice.

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

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

Limited Impact of Pivalate-Induced Secondary Carnitine Deficiency on Hepatic Transcriptome and Hepatic and Plasma Metabolome in Nursery Pigs

Administration of pivalate has been demonstrated to be suitable for the induction of secondary carnitine deficiency (CD) in pigs, as model objects for humans. In order to comprehensively characterize the metabolic effects of secondary CD in the liver of pigs, the present study aimed to carry out comparative analysis of the hepatic transcriptome and hepatic and plasma metabolome of a total of 12 male 5-week-old pigs administered either pivalate (group PIV, n = 6) or vehicle (group CON, n = 6) for 28 days. Pigs of group PIV had approximately 40-60% lower concentrations of free carnitine and acetylcarnitine in plasma, liver and different skeletal muscles than pigs of group CON (p < 0.05). Transcript profiling of the liver revealed 140 differentially expressed genes (DEGs) between group PIV and group CON (fold change > 1.2 or <-1.2, p-value < 0.05). Biological process terms dealing with the innate immune response were found to be enriched with the DEGs (p < 0.05). Using a targeted metabolomics approach for the simultaneous quantification of 630 metabolites, 9 liver metabolites and 18 plasma metabolites were identified to be different between group PIV and group CON (p < 0.05). Considering the limited alterations of the hepatic transcriptome and of the liver and plasma metabolome, it can be concluded that pivalate-induced secondary CD is not associated with significant hepatic metabolism changes in pigs.

Comparative study of the efficacy of captopril, simvastatin, and L-carnitine as cardioprotective drugs in children with type 1 diabetes mellitus: a randomised controlled trial

OBJECTIVES

To assess the efficacy and safety of captopril, simvastatin, and L-carnitine as cardioprotective drugs in children with type 1 diabetes mellitus on different echocardiographic parameters, electrocardiographic parameter, lipid profile, and carotid intima-media thickness.

METHODS

This randomised controlled trial was conducted on 100 children with type 1 diabetes mellitus for more than 3 years during the period from September 2018 to June 2020. Fifty healthy children of matched age and sex served as a control group. The patients were randomly assigned into four groups (25 children each): no-treatment group who received no cardioprotective drug, simvastatin group who received simvastatin (10-20 mg/day), captopril group who received captopril (0.2 mg/kg/day), and L-carnitine group who received L-carnitine (50 mg/kg/day) for 4 months. Lipid profile, serum troponin I, carotid intima-media thickness, and echocardiographic examinations were performed on all included children before and after the treatment.

RESULTS

Total cholesterol and low-density lipoprotein were significantly decreased in children who received simvastatin or L-carnitine. Triglycerides significantly decreased only in children who received simvastatin. High-density lipoprotein significantly increased in simvastatin and L-carnitine groups only. Serum troponin I decreased significantly in all the three treatment groups. Carotid intima-media thickness showed no significant change in all treatment groups. Echocardiographic parameters significantly improved in simvastatin, L-carnitine, and captopril groups.

CONCLUSION

Captopril, simvastatin, and L-carnitine have a significant beneficial effect on cardiac functions in children with type 1 diabetes mellitus. However, only simvastatin and L-carnitine have a beneficial effect on the lipid profile. The drugs were safe and well tolerated.Clinical trial registration: The clinical trial was registered at www.clinicaltrial.gov (NCT03660293).

Sargassum fusiforme fucoidan modifies gut microbiota and intestinal metabolites during alleviation of hyperglycemia in type 2 diabetic mice

Type 2 diabetic mellitus (T2DM) is a complicated metabolic disorder that is now considered as a major global public health problem. Fucoidan exhibits diverse biological activities, especially prevention of metabolic diseases. In this regard, we herein aimed to reveal the beneficial effect of Sargassum fusiforme fucoidan (SFF) on high-fat diet (HFD) and streptozotocin (STZ) induced T2DM mice. We noted that on the one hand, SFF significantly decreased fasting blood glucose, diet and water intake, and hyperlipidemia, while on the other hand, it improved glucose tolerance. Furthermore, SFF reduced epididymal fat deposition, attenuated the pathological changes in heart and liver tissues, and decreased oxidative stress in diabetic mice. To explore the underlying mechanisms of these ameliorative effects, the gut microbiota was analyzed. Notably, SFF highly enriched benign microbes including Bacteroides, Faecalibacterium and Blautia, as well as increased levels of (R)-carnitine and choline in the colon of diabetic mice. This may be a potential mechanism for alleviating T2DM, thus implying the benefits of SFF as an adjuvant agent for T2DM treatment. Taken together, this study demonstrated a promising application of fucoidan as one of the adjuvant agents for the management of T2DM in the future.

The Association Between Serum Carnitine Level, Glucose Regulation, Body Fat and Nutrient Intake in Diabetic Individuals

Carnitine (β-hydroxy-γ-trimethyl amino butyrate) is, a vitamin-like substance carrying long-chain fatty acids into the mitochondrial matrix. Due to its effect in energy metabolism, carnitine plays an important role in controlling diabetes and its complications. Studies on this topic have often focused on carnitine supplementation. This study was planned to investigate the relationship between serum carnitine level, glucose regulation and body fat in diabetic patients. A total of 64 people between the ages of 30-5, 32 patients with type 2 diabetes and 32 healthy subjects, were included in the study. Individual lipid profiles, glucose, insulin and serum carnitine levels were analyzed, anthropometric measurements were taken and 24-hour recall food consumption was recorded. As a result, blood glucose, insulin, triglyceride, VLDL-C, HDL-C and HOMA-IR were found to be higher in diabetic individuals than healthy group (p<0,05). Serum carnitine levels were found to be significantly lower in diabetic male (50,6±20,83 nmol/mL) than in healthy male (59,5±17,25 nmol/mL)(p<0,05). This difference was not statistically significant among female (p>0,05). It has been observed that intake of energy and macronutrients of diabetic individuals is generally lower than that of healthy individuals. Serum carnitine level was positively associated with polyunsaturated fatty acids and omega-6 fatty acid intake in male in the healthy group showed a negative correlation with fiber intake in female in the healthy group (p<0,05). There were negative correlations between serum carnitine level with body weight, body mass index and body fat mass in female in the healthy group (p<0,05). Individuals with diabetes are predisposed to dyslipidemia and insulin resistance. As a result; food consumption, and body fat affect individuals’ serum carnitine levels in type-2 diabetes. Since there is not enough study evaluating the relationship between anthropometric measurements of individuals and serum carnitine levels, it is thought that this result will guide future studies.

Triangulating evidence from longitudinal and Mendelian randomization studies of metabolomic biomarkers for type 2 diabetes

The number of people affected by Type 2 diabetes mellitus (T2DM) is close to half a billion and is on a sharp rise, representing a major and growing public health burden. Given its mild initial symptoms, T2DM is often diagnosed several years after its onset, leaving half of diabetic individuals undiagnosed. While several classical clinical and genetic biomarkers have been identified, improving early diagnosis by exploring other kinds of omics data remains crucial. In this study, we have combined longitudinal data from two population-based cohorts CoLaus and DESIR (comprising in total 493 incident cases vs. 1360 controls) to identify new or confirm previously implicated metabolomic biomarkers predicting T2DM incidence more than 5 years ahead of clinical diagnosis. Our longitudinal data have shown robust evidence for valine, leucine, carnitine and glutamic acid being predictive of future conversion to T2DM. We confirmed the causality of such association for leucine by 2-sample Mendelian randomisation (MR) based on independent data. Our MR approach further identified new metabolites potentially playing a causal role on T2D, including betaine, lysine and mannose. Interestingly, for valine and leucine a strong reverse causal effect was detected, indicating that the genetic predisposition to T2DM may trigger early changes of these metabolites, which appear well-before any clinical symptoms. In addition, our study revealed a reverse causal effect of metabolites such as glutamic acid and alanine. Collectively, these findings indicate that molecular traits linked to the genetic basis of T2DM may be particularly promising early biomarkers.

The Safety and Efficacy in Horses of Certain Nutraceuticals that Claim to Have Health Benefits

Equine nutraceuticals are promoted as useful therapies to help optimize health and athletic performance, often without the benefit of independent research to support product efficacy and safety. This review focuses on 4 main categories of equine supplements that are frequently used as nutraceuticals: (i) supplements to support metabolic health, (ii) gastric support products, (iii) common ingredients that are included in supplements designed to support hoof health, and (iv) supplements to support joint health.

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.

Carnitine promotes recovery from oxidative stress and extends lifespan in C. elegans

Carnitine is required for transporting fatty acids into the mitochondria for β-oxidation. Carnitine has been used as an energy supplement but the roles in improving health and delaying aging remain unclear. Here we show in C. elegans that L-carnitine improves recovery from oxidative stress and extends lifespan. L-carnitine promotes recovery from oxidative stress induced by paraquat or juglone and improves mobility and survival in response to H₂O₂ and human amyloid (Aβ) toxicity. L-carnitine also alleviates the oxidative stress during aging, resulting in moderate but significant lifespan extension, which was dependent on SKN-1 and DAF-16. Long-lived worms with germline loss (glp-1) or reduced insulin receptor activity (daf-2) recover from aging-associated oxidative stress faster than wild-type controls and their long lifespans were not further increased by L-carnitine. A new gene, T08B1.1, aligned to a known carnitine transporter OCTN1 in humans, is required for L-carnitine uptake in C. elegans. T08B1.1 expression is elevated in daf-2 and glp-1 mutants and its knockdown prevents L-carnitine from improving oxidative stress recovery and prolonging lifespan. Together, our study suggests an important role of L-carnitine in oxidative stress recovery that might be important for healthy aging in humans.

Loss of Muscle Carnitine Palmitoyltransferase 2 Prevents Diet-Induced Obesity and Insulin Resistance despite Long-Chain Acylcarnitine Accumulation

To assess the effects of acylcarnitine accumulation on muscle insulin sensitivity, a model of muscle acylcarnitine accumulation was generated by deleting carnitine palmitoyltransferase 2 (CPT2) specifically from skeletal muscle (Cpt2^Sk-/- mice). CPT2 is an irreplaceable enzyme for mitochondrial long-chain fatty acid oxidation, converting matrix acylcarnitines to acyl-CoAs. Compared with controls, Cpt2^Sk-/- muscles do not accumulate anabolic lipids but do accumulate ∼22-fold more long-chain acylcarnitines. High-fat-fed Cpt2^Sk-/- mice resist weight gain, adiposity, glucose intolerance, insulin resistance, and impairments in insulin-induced Akt phosphorylation. Obesity resistance of Cpt2^Sk-/- mice could be attributed to increases in lipid excretion via feces, GFD15 production, and energy expenditure. L-carnitine supplement intervention lowers acylcarnitines and improves insulin sensitivity independent of muscle mitochondrial fatty acid oxidative capacity. The loss of muscle CPT2 results in a high degree of long-chain acylcarnitine accumulation, simultaneously protecting against diet-induced obesity 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.

L-carnitine infusion does not alleviate lipid-induced insulin resistance and metabolic inflexibility

BACKGROUND

Low carnitine status may underlie the development of insulin resistance and metabolic inflexibility. Intravenous lipid infusion elevates plasma free fatty acid (FFA) concentration and is a model for simulating insulin resistance and metabolic inflexibility in healthy, insulin sensitive volunteers. Here, we hypothesized that co-infusion of L-carnitine may alleviate lipid-induced insulin resistance and metabolic inflexibility.

METHODS

In a randomized crossover trial, eight young healthy volunteers underwent hyperinsulinemic-euglycemic clamps (40mU/m2/min) with simultaneous infusion of saline (CON), Intralipid (20%, 90mL/h) (LIPID), or Intralipid (20%, 90mL/h) combined with L-carnitine infusion (28mg/kg) (LIPID+CAR). Ten volunteers were randomized for the intervention arms (CON, LIPID and LIPID+CAR), but two dropped-out during the study. Therefore, eight volunteers participated in all three intervention arms and were included for analysis.

RESULTS

L-carnitine infusion elevated plasma free carnitine availability and resulted in a more pronounced increase in plasma acetylcarnitine, short-, medium-, and long-chain acylcarnitines compared to lipid infusion, however no differences in skeletal muscle free carnitine or acetylcarnitine were found. Peripheral insulin sensitivity and metabolic flexibility were blunted upon lipid infusion compared to CON but L-carnitine infusion did not alleviate this.

CONCLUSION

Acute L-carnitine infusion could not alleviated lipid-induced insulin resistance and metabolic inflexibility and did not alter skeletal muscle carnitine availability. Possibly, lipid-induced insulin resistance may also have affected carnitine uptake and may have blunted the insulin-induced carnitine storage in muscle. Future studies are needed to investigate this.

L-Carnitine's Effect on the Biomarkers of Metabolic Syndrome: A Systematic Review and Meta-Analysis of Randomized Controlled Trials

A systematic review and meta-analysis of randomized controlled trials (RCTs) was carried out to assess L-carnitine supplements’ influence on the biomarkers of metabolic syndrome (MetSyn). PubMed, EMBASE, Cochrane library, and CINAHL were used to collect RCT studies published prior to February 2020. RCT studies were included if they had at least one of the following biomarker outcome measurements: waist circumference (WC), blood pressure (BP), fasting blood sugar (FBS), triglyceride (TG), or high density lipoprotein-cholesterol (HDLc). Nine of twenty studies with adequate methodological quality were included in this meta-analysis. The dose of L-carnitine supplementation administered varied between 0.75 and 3 g/day for durations of 8–24 weeks. L-carnitine supplementation significantly reduced WC and systolic BP (SBP), with no significant effects on FBS, TG, and HDLc. We found that L-carnitine supplementation at a dose of more than 1 g/d significantly reduced FBS and TG and increased HDLc. In conclusion, L-carnitine supplementation is correlated with a significant reduction of WC and BP. A dose of 1–3 g/d could improve the biomarkers of MetSyn by reducing FBS and TG and increasing HDLc.

Network pharmacology and metabolomics study on the intervention of traditional Chinese medicine Huanglian Decoction in rats with type 2 diabetes mellitus

ETHNOPHARMACOLOGICAL RELEVANCE

Type 2 diabetes mellitus (T2DM) is currently one of the most prominent and global chronic conditions. Huanglian Decoction (HLD) is a traditional Chinese medicine (TCM) preparation that has been used to treat T2DM for thousands of years in China. However, its mechanism of action at the metabolic level is still unclear. The purpose of this work is to study the mechanism of HLD in treating T2DM based on metabolomics and network pharmacology.

MATERIALS AND METHODS

In this study, metabolomics combined with network pharmacology was used to elucidate the therapeutic mechanism of HLD in T2DM. Serum samples were collected from rats with T2DM, induced by a high-sugar and high-fat diet combined with streptozotocin (STZ), to measure the levels of biochemical markers. Urinary metabolomics-based analysis using high-performance liquid chromatography coupled with mass spectrometry (HPLC-MS) was conducted to evaluate the differential metabolites from multiple metabolic pathways.

RESULTS

After treatment with HLD for 4 weeks, biochemical indicators, including fasting blood glucose (FBG), blood lipid, fasting insulin (FINS), insulin sensitivity index (ISI), and homeostasis model assessment of insulin resistance (HOMA-IR), were significantly improved. Metabolomics results revealed that HLD regulated the biomarkers, such as cytosine, L-carnitine, betaine, phenylalanine, glucose, citrate, phenylpyruvate, and hippuric acid in glyoxylate and dicarboxylate metabolism, phenylalanine metabolism, and tricarboxylic acid (TCA) cycle. The combination of network pharmacology, metabolomics, western blot, and PCR showed that HLD can treat T2DM by enhancing the gene and protein expression levels of glucose transporter 4 (GLUT4), insulin receptor (INSR), and mitogen-activated protein kinase 1 (MAPK1) to interfere with glyoxylate and dicarboxylate metabolism.

CONCLUSIONS

The study based on metabolomics and network pharmacology indicated that HLD can improve T2DM through multiple targets and pathways, and it may be a useful alternative therapy for the treatment of T2DM.

Effects of acetyl L-carnitine on zebrafish embryos: Phenotypic and gene expression studies

Acetyl L-carnitine (ALCAR), a dietary supplement and an antioxidant, plays a vital role in the bioenergetic process that produces ATP. Although there are reports on antioxidant toxicity, there is no information on the potential toxicity of ALCAR. Here, using zebrafish embryos, we explored whether ALCAR modulated ATP synthesis, generation of reactive oxygen species (ROS) and expression of specific genes related to major signaling pathways that control metabolism, growth, differentiation, apoptosis and oxidative stress. First, we show that ALCAR elicits a physiologic response, as ATP levels increased after ALCAR treatment. Simultaneously, an increase in the expression of ROS, a by-product of ATP synthesis, was observed in the ALCAR-treated embryos. Consistent with higher ROS expression, the level of cysteine, a precursor of glutathione, was significantly reduced. ALCAR did not have any drastic effect on overall development and heart rate. Polymerase chain reaction-based gene expression array analyses showed no significant change in the expression of 83 genes related to 10 major signaling pathways including: the transforming growth factor β (TGFβ), Wingless and Int-1 (Wnt), nuclear factor κ-light-chain-enhancer of activated B cells (NF-κB), Janus kinase/signal transducers and activators of transcription (JAK/STAT), p53, Notch, Hedgehog, Peroxisome proliferator-activated receptor (PPAR), oxidative stress, and hypoxia pathways. Our results show that the expression of 83 genes related to these major signaling pathways did not change significantly.

Skeletal muscle volume loss among liver cirrhosis patients receiving levocarnitine predicts poor prognosis

Sarcopenia has a negative impact on the prognosis of patients with liver cirrhosis (LC). We investigated the significance of skeletal muscle volume and its changes in LC patients taking levocarnitine (L-carnitine).We retrospectively analyzed 51 LC patients taking L-carnitine from December 2012 to March 2019. Skeletal mass index was calculated as the left-right sum of the major × minor axis of psoas muscle at the third lumbar vertebra, divided by height squared (psoas muscle index [PMI]). Patients were classified into 2 groups (low and normal PMI) depending on PMI < 6.0 and < 3.4 cm/m for men and women, respectively. Changes in PMI per month during L-carnitine administration (ΔPMI/m) were calculated, and we classified the patients into 2 groups (severe and mild muscle atrophy) depending on ΔPMI/m below the lower quartile. We assessed overall survival (OS).At the start of L-carnitine administration, there were no significant differences in OS between groups with low and normal PMI. Multivariate analysis showed that ΔPMI/m (hazard ratio [HR], 0.007; P = .005) and L-carnitine administration period (HR, 0.956; P = .021) were significantly associated with OS. Patients with severe muscle atrophy had a significantly lower OS than those with mild muscle atrophy. There was the positive correlation relationship between ΔPMI/m and L-carnitine administration period.Among LC patients taking L-carnitine, progressive muscle volume loss was a predictor of poor prognosis. L-carnitine administration for longer may be able to prevent muscle volume loss and lead to a better prognosis in LC patients.

Metabolic Profiling of Diabetic Cats in Remission

Background: The majority of diabetic cats in remission have abnormal glucose tolerance, and approximately one third relapse within 1 year. Greater understanding of the metabolic characteristics of diabetic cats in remission, and predictors of relapse is required to effectively monitor and manage these cats.

Objectives: To identify and compare differences in plasma metabolites between diabetic cats in remission and healthy control cats using a metabolomics approach. Secondly, to assess whether identified metabolites are predictors of diabetic relapse.

Animals: Twenty cats in diabetic remission for a median of 101 days, and 22 healthy matched control cats.

Methods: Cats were admitted to a clinic, and casual blood glucose was recorded. After a 24 h fast, blood glucose concentration was measured, then a blood sample was taken for metabolomic (GCMS and LCMS) analyses. Three hours later, a simplified intravenous glucose tolerance test (1 g glucose/kg) was performed. Cats were monitored for diabetes relapse for at least 9 months (270 days) after baseline testing.

Results: Most cats in remission continued to display impaired glucose tolerance. Concentrations of 16 identified metabolites differed (P ≤ 0.05) between remission and control cats: 10 amino acids and stearic acid (all lower in remission cats), and glucose, glycine, xylitol, urea and carnitine (all higher in remission cats). Moderately close correlations were found between these 16 metabolites and variables assessing glycaemic responses (most |r| = 0.31 to 0.69). Five cats in remission relapsed during the study period. No metabolite was identified as a predictor of relapse.

Conclusion and clinical importance: This study shows that cats in diabetic remission have abnormal metabolism.

Effects of Chromium and Carnitine Co-supplementation on Body Weight and Metabolic Profiles in Overweight and Obese Women with Polycystic Ovary Syndrome: a Randomized, Double-Blind, Placebo-Controlled Trial

The primary aim of our study was to determine the influence of taking chromium plus carnitine on insulin resistance, with a secondary objective of evaluating the influences on lipid profiles and weight loss in overweight subjects with polycystic ovary syndrome (PCOS). In a 12-week randomized, double-blind, placebo-controlled clinical trial, 54 overweight women were randomly assigned to receive either supplements (200 μg/day chromium picolinate plus 1000 mg/day carnitine) or placebo (27/each group). Chromium and carnitine co-supplementation decreased weight (- 3.6 ± 1.8 vs. - 1.0 ± 0.7 kg, P < 0.001), BMI (- 1.3 ± 0.7 vs. - 0.3 ± 0.3 kg/m², P < 0.001), fasting plasma glucose (FPG) (- 5.1 ± 6.0 vs. - 1.1 ± 4.9 mg/dL, P = 0.01), insulin (- 2.0 ± 1.4 vs. - 0.2 ± 1.2 μIU/mL, P < 0.001), insulin resistance (- 0.5 ± 0.4 vs. - 0.04 ± 0.3, P < 0.001), triglycerides (- 18.0 ± 25.2 vs. + 5.5 ± 14.4 mg/dL, P < 0.001), total (- 17.0 ± 20.3 vs. + 3.6 ± 12.0 mg/dL, P < 0.001), and LDL cholesterol (- 13.3 ± 19.2 vs. + 1.4 ± 13.3 mg/dL, P = 0.002), and elevated insulin sensitivity (+ 0.007 ± 0.005 vs. + 0.002 ± 0.005, P < 0.001). In addition, co-supplementation upregulated peroxisome proliferator-activated receptor gamma (P = 0.02) and low-density lipoprotein receptor expression (P = 0.02). Overall, chromium and carnitine co-supplementation for 12 weeks to overweight women with PCOS had beneficial effects on body weight, glycemic control, lipid profiles except HDL cholesterol levels, and gene expression of PPAR-γ and LDLR. Clinical trial registration number: http://www.irct.ir: IRCT20170513033941N38.

Carnitine supplementation improves metabolic flexibility and skeletal muscle acetylcarnitine formation in volunteers with impaired glucose tolerance: A randomised controlled trial

BACKGROUND

Type 2 diabetes patients and individuals at risk of developing diabetes are characterized by metabolic inflexibility and disturbed glucose homeostasis. Low carnitine availability may contribute to metabolic inflexibility and impaired glucose tolerance. Here, we investigated whether carnitine supplementation improves metabolic flexibility and insulin sensitivity in impaired glucose tolerant (IGT) volunteers.

METHODS

Eleven IGT- volunteers followed a 36-day placebo- and L-carnitine treatment (2 g/day) in a randomised, placebo-controlled, double blind crossover design. A hyperinsulinemic-euglycemic clamp (40 mU/m2/min), combined with indirect calorimetry (ventilated hood) was performed to determine insulin sensitivity and metabolic flexibility. Furthermore, metabolic flexibility was assessed in response to a high-energy meal. Skeletal muscle acetylcarnitine concentrations were measured in vivo using long echo time proton magnetic resonance spectroscopy (1H-MRS, TE=500 ms) in the resting state (7:00AM and 5:00PM) and after a 30-min cycling exercise. Twelve normal glucose tolerant (NGT) volunteers were included without any intervention as control group.

RESULTS

Metabolic flexibility of IGT-subjects completely restored towards NGT control values upon carnitine supplementation, measured during a hyperinsulinemic-euglycemic clamp and meal test. In muscle, carnitine supplementation enhanced the increase in resting acetylcarnitine concentrations over the day (delta 7:00 AM versus 5:00 PM) in IGT-subjects. Furthermore, carnitine supplementation increased post-exercise acetylcarnitine concentrations and reduced long-chain acylcarnitine species in IGT-subjects, suggesting the stimulation of a more complete fat oxidation in muscle. Whole-body insulin sensitivity was not affected.

CONCLUSION

Carnitine supplementation improves acetylcarnitine formation and rescues metabolic flexibility in IGT-subjects. Future research should investigate the potential of carnitine in prevention/treatment of type 2 diabetes.