Comparison between orlistat plus l-carnitine and orlistat alone on inflammation parameters in obese diabetic patients

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

AIMS

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

The Effects of L-Carnitine Supplementation on Weight Loss, Glycemic Control, and Cardiovascular Risk Factors in Patients With Type 2 Diabetes: A Systematic Review and Dose-response Meta-Analysis of Randomized Controlled Trials

PURPOSE

L-carnitine supplementation has been recommended to improve cardiometabolic health markers in diabetic patients. Our purpose was to assess the dose-dependent effects of l-carnitine supplementation on cardiometabolic risk factors in patients with type 2 diabetes.

METHODS

PubMed/Medline, Scopus, and Web of Science were searched until May 2022 for randomized controlled trials that examined the impact of l-carnitine supplementation on cardiometabolic risk factors in adults with type 2 diabetes. The mean difference (MD) and its 95% confidence interval (CI) were estimated utilizing a random-effects model. Nonlinear dose-response associations were modeled with restricted cubic splines. The certainty of evidence was rated using the GRADE approach.

FINDINGS

Twenty-one randomized trials with 2041 patients with type 2 diabetes were included. We found that every 1 g/d supplementation with l-carnitine significantly reduced body mass index (MD: -0.37 kg/m2, 95% CI: -0.59, -0.15; I2 =93%, n=13, GRADE=low), HbA1c (MD: -0.16%, 95% CI: -0.32, -0.01; I2 = 94%, n = 18, GRADE = moderate), and low-density lipoprotein cholesterol (MD: -0.11 mmol/L, 95% CI: -0.16, -0.05; I2 = 91%, n = 11, GRADE = high). There were also reductions in serum triglycerides (MD: 0.07 mmol/L), total cholesterol (MD: -0.13 mmol/L), and fasting plasma glucose (MD: -0.17 mmol/L). A U-shaped effect was demonstrated for body mass index, with the largest reduction at 2 g/d. A linear reduction was seen for serum triglycerides, total cholesterol, and fasting plasma glucose up to l-carnitine supplementation of 4 g/d.

IMPLICATIONS

L-carnitine supplementation resulted in a small reduction in serum lipids and plasma glucose in patients with type 2 diabetes. However, due to high statistical heterogeneity, the results should be interpreted very cautiously.

The effects of L-carnitine supplementation on inflammation, oxidative stress, and clinical outcomes in critically Ill patients with sepsis: a randomized, double-blind, controlled trial

BACKGROUND

Sepsis, a life-threatening organ dysfunction caused by a host's dysregulated response to infection with an inflammatory process, becomes a real challenge for the healthcare systems. L-carnitine (LC) has antioxidant and anti-inflammatory properties as in previous studies. Thus, we aimed to determine the effects of LC on inflammation, oxidative stress, and clinical parameters in critically ill septic patients.

METHODS

A randomized double-blinded controlled trial was conducted. A total of 60 patients were randomized to receive LC (3 g/day, n = 30) or placebo (n = 30) for 7 days. Inflammatory and oxidative stress parameters (C-reactive protein (CRP), erythrocyte sedimentation rate (ESR), superoxide dismutase (SOD), malondialdehyde (MDA), total antioxidant capacity (TAC), 28-day mortality rate, and some monitoring variables were evaluated.

RESULTS

There was no statistically significant difference between study arms in baseline characteristics and disease severity scores. CRP (p < 0.001) and ESR (p: 0.004) significantly reduced, and SOD (p < 0.001) and TAC (p < 0.001) significantly improved in the LC group after 7 days. Between-group analysis revealed a significant reduction in CRP (p: 0.001) and serum chloride (p: 0.032), an increase in serum albumin (p: 0.036) and platelet (p: 0.004) significantly, and an increase in SOD marginally (p: 0.073). The 28-day mortality rate was also lower in the LC group compared with placebo (7 persons vs. 15 persons) significantly (odds ratio: 0.233, p: 0.010).

CONCLUSIONS

L-carnitine ameliorated inflammation, enhanced antioxidant defense, reduced mortality, and improved some clinical outcomes in critically ill patients with sepsis.

TRIAL REGISTRATION

IRCT20201129049534N1; May 2021.

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

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

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 and synbiotic co-supplementation: beneficial effects on metabolic-endotoxemia, meta-inflammation, and oxidative-stress biomarkers in obese patients: a double blind, randomized, controlled clinical trial

Obesity, a chronic pandemic disease, is characterized by low-grade chronic inflammation, accompanied by over-expression of pro-inflammatory cytokines, thereby contributing to metabolic disorders pathogenesis. Oxidative-stress, an adverse cellular response to adipocyte hypertrophy, promotes inflammation. Furthermore, gut-microbiota dysbiosis may induce oxidative-stress, low-grade inflammation, and metabolic-endotoxemia as major drivers of obesity. Functional-foods/nutraceuticals have attracted extensive attention due to their plausible anti-inflammatory/anti-oxidative properties; evidence supports the superiority of the nutraceutical combined-supplementation approach versus conventional mono-therapies. Current data suggest the anti-oxidative/anti-inflammatory properties of either L-carnitine or pre/pro/synbiotics. This trial compared the effects of co-supplementing L-carnitine and multi-species/multi-strain synbiotic versusL-carnitine mono-therapy on inflammatory/anti-inflammatory, oxidative-stress, and metabolic-endotoxemia biomarkers in 46 female obese patients, receiving either co-supplementation (L-carnitine-tartrate (2 × 500 mg d^-1) + multi-species/multi-strain synbiotic (1 capsule per day)) or mono-therapy (L-carnitine-tartrate (2 × 500 mg d^-1) + maltodextrin (1 capsule per day)) for eight weeks. L-Carnitine + synbiotic co-supplementation significantly decreased interleukin-6 (IL-6, -33.98%), high-sensitivity-C-reactive-protein (hs-CRP, -10%), tumor-necrosis-factor-alpha (TNF-α, -18.73%), malondialdehyde (MDA, -21.73%), and lipopolysaccharide (LPS, -10.14%), whereas the increase in interleukin-10 (IL-10, 7.69%) and total-antioxidant-capacity (TAC, 4.13%) levels was not significant. No significant changes were observed for the above-mentioned parameters in the L-carnitine + placebo group, except for a significant reduction in IL-10 (-17.59%) and TNF-α (-14.78%); however, between-group differences did not reach the significant threshold. Co-supplementing L-carnitine + multi-strain synbiotic led to significant amelioration of inflammatory, oxidative, and metabolic-endotoxemia responses in female obese patients; nevertheless, no improving effects were observed in patients receiving single-supplementation, suggesting that L-carnitine + synbiotic co-supplementation might represent an adjuvant approach to improve oxidative-stress/pro-inflammatory indicators in women with obesity, possibly through beneficial effects of the synbiotic alone. Further longer duration studies with higher doses of L-carnitine in a three-group setting are warranted to elucidate the possibility of synergistic or complementary mechanisms.

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.

An Exploratory Critical Review on TNF-α as a Potential Inflammatory Biomarker Responsive to Dietary Intervention with Bioactive Foods and Derived Products

This review collects and critically examines data on the levels of tumour necrosis factor-alpha (TNF-α) in lean, overweight and obese subjects, and the effects of intervention with different foods and food products containing bioactive constituents in overweight/obese individuals. We additionally explore the influence of different single nucleotide polymorphisms (SNPs) on TNF-α levels and compare the response to food products with that to some anti-obesity drugs. Our aim was to provide an overview of the variability, consistency, and magnitude of the reported effects of dietary factors on TNF-α, and to envisage the reliability of measuring changes in the levels of this cytokine as a biomarker responsive to food intervention in association with the reduction in body weight. Regarding the circulating levels of TNF-α, we report: (i) a large intra-group variability, with most coefficients of variation (CV%) values being ≥30% and, in many cases, >100%; (ii) a large between-studies variability, with baseline TNF-α values ranging from <1.0 up to several hundred pg/mL; (iii) highly variable effects of the different dietary approaches with both statistically significant and not significant decreases or increases of the protein, and the absolute effect size varying from <0.1 pg/mL up to ≈50 pg/mL. Within this scenario of variability, it was not possible to discern clear differentiating limits in TNF-α between lean, overweight, and obese individuals or a distinct downregulatory effect on this cytokine by any of the different dietary approaches reviewed, i.e., polyunsaturated fatty acids (PUFAs), Vitamin-D (VitD), mixed (micro)nutrients, (poly)phenols or other phytochemicals. Further, there was not a clear relationship between the TNF-α responses and body weight changes. We found similarities between dietary and pharmacological treatments in terms of variability and limited evidence of the TNF-α response. Different factors that contribute to this variability are discussed and some specific recommendations are proposed to reinforce the need to improve future studies looking at this cytokine as a potential biomarker of response to dietary approaches.

The Effects of L-Carnitine, Acetyl-L-Carnitine, and Propionyl-L-Carnitine on Body Mass in Type 2 Diabetes Mellitus Patients

Purpose: The study aimed to explore the effects of l-carnitine, acetyl-l-carnitine, and propionyl-l-carnitine on Body Mass in type 2 diabetes mellitus (T2DM) patients.

Methods: Randomized controlled trial (RCT) studies of l-carnitine, acetyl-l-carnitine, and propionyl-l-carnitine in T2DM patients were searched. The change rates of Body Mass index (BMI) from baseline values were used as an evaluation indicator. The maximal effect (E_max) model by non-linear mixed-effect modeling (NONMEM) was used as the evaluation method.

Results: A total of 10 RCT studies, 1239 T2DM patients were included for analysis, including eight studies of l-carnitine, one study of acetyl-l-carnitine, and one study of propionyl-l-carnitine. The study found that l-carnitine could reduce the Body Mass of T2DM patients. Based on only one study each for acetyl-l-carnitine and propionyl-l-carnitine, no significant effects were found in acetyl-l-carnitine or propionyl-l-carnitine. In addition, in order to achieve a plateau of efficacy (80% E_max), 2 g/day l-carnitine was required for at least 2 weeks.

Conclusions: Two g/day l-carnitine was required for at least 2 weeks to affect Body Mass in T2DM patients, and no significant effects were found in acetyl-l-carnitine or propionyl-l-carnitine.

Quantitative efficacy of L-carnitine supplementation on glycemic control in type 2 diabetes mellitus patients

OBJECTIVES

This study aimed to explore the quantitative efficacy of L-carnitine supplementation on glycemic control in type 2 diabetes mellitus patients using model-based meta-analysis (MBMA).

METHODS

Literatures were retrieved from the public database and data from these trials were extracted. The quantitative efficacy of L-carnitine on fasting plasma glucose (FPG) and glycated hemoglobin (HbA1c) in type 2 diabetes mellitus patients were evaluated by maximal effect (E_max) models with nonlinear mixed effects modeling (NONMEM).

RESULTS

In the model of FPG, E_max and _treatment duration to reach half of the maximal effects (ET₅₀) were -9.8% and 36.1 weeks, respectively. In the model of HbA1c, E_max and ET₅₀ were -19.6% and 106 weeks, respectively. In addition, the durations for achieving 25%, 50%, 75%, 80%, and 90% E_max of L-carnitine on FPG were 13, 36.1, 118, 160, and 390 weeks, respectively. The durations for achieving 25%, 50%, 75%, 80%, and 90% E_max of L-carnitine on HbA1c were 38, 106, 334, 449, and 1058 weeks, respectively.

CONCLUSIONS

It was the first time to provide valuable quantitative information for efficacy of L-carnitine supplementation on glycemic control in type 2 diabetes mellitus patients.

The effects of L-carnitine supplementation on indicators of inflammation and oxidative stress: a systematic review and meta-analysis of randomized controlled trials

Objective

Several trials investigated the efficacy of L-carnitine administration on markers of inflammation and indicators of oxidative stress; however, their findings are controversial. The aim of this study was to conduct a comprehensive meta-analysis and a critical review, which would analyze all randomized controlled trials (RCTs) in order to determine the effects of L-carnitine supplementation on inflammatory markers and oxidative stress.

Methods

An electronic search was performed using Scopus, Cochrane Library, PubMed, Google scholar and Web of Science databases on publications from 1990 up to May 2020. Human RCTs conducted in healthy subjects or participants with certain disorders which investigating the efficacy of L-carnitine supplementation compared to control (placebo, usual treatment or no intervention) on inflammation and oxidative markers were included. Data were pooled applying a random-effects model and as the overall effect size, weighted mean difference (WMD) was presented. Between heterogeneity among studies was computed using Cochran's Q test and I-square (I²). Quality of studies assessed using the Jadad scale. Dose-response analysis was measured using meta-regression. The funnel plot, as well as the Egger's regression test was applied to determine the publication bias.

Results

44 trials (reported 49 effect sizes for different outcomes of interest) met the inclusion criteria for this meta-analysis. According to the findings, L-carnitine supplementation resulted in a significant reduction in C-reactive protein (CRP) (WMD: -0.10; 95% CI: -0.14, -0.06), interleukin 6 (IL-6) (WMD: -1.87; 95% CI: -2.80, -0.95), tumor necrosis factor-α (TNF-α) levels (WMD: -1.43; 95% CI: -2.03, -0.84), and malondialdehyde (MDA) (WMD: -0.47; 95% CI: -0.76, -0.18) levels, while there was a significant increase in superoxide dismutase (SOD) (WMD: 2.14; 95% CI: 1.02, 3.25). However, no significant effects of L-carnitine on glutathione peroxidase (GPx) (WMD: 0.02; 95% CI: -0.01, 0.05) and total antioxidant capacity (TAC) (WMD: 0.14; 95% CI: -0.05, 0.33) were found.

Conclusions

L-carnitine supplementation was associated with lowering of CRP, IL-6, TNF-α, and MDA, and increasing SOD levels, but did not affect other inflammatory and oxidative stress biomarkers.

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.

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

BACKGROUND AND AIM

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

METHODS AND RESULTS

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

CONCLUSION

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

Preliminary evidence for reduced adipose tissue inflammation in vegetarians compared with omnivores

Background

There are links between obesity and inflammation that may relate activation of pro-inflammatory pathways by dietary factors. Because dietary fat intake of vegetarians is thought to be more beneficial than that of omnivores, we hypothesized that obese vegetarians would have less adipose tissue inflammation and lower intramyocellular ceramide concentrations than equally obese omnivores.

Methods

Eight obese vegetarian (1 male) and 8 obese omnivore volunteers (1 male) completed a Food Frequency Questionnaire, underwent body composition measures, subcutaneous adipose tissue and muscle biopsies. We used immunohistochemistry to measure adipose macrophage (ATM) and senescent cells. Plasma free fatty acid (FFA), adipose FA and muscle ceramide profiles were measured using liquid chromatography/mass spectrometry. Student t tests were used for the comparison of primary outcomes; univariate regression analysis was used to test for associations between dietary patterns and ATMs (secondary analysis).

Results

There were no differences in age (38 ± 8 vs. 39 ± 8 years), BMI (32.2 ± 2.6 vs. 33.3 ± 1.9 kg/m²) or percent body fat (44 ± 8 vs. 45 ± 4) between the vegetarians and omnivores. Vegetarians consumed 42% (P = 0.02) less saturated fat and 50% (P = 0.04) less cholesterol than the omnivores. Plasma FFA of vegetarians had lesser proportions of palmitic acid (24 ± 3 vs. 29 ± 4%, P = 0.02) and vegetarians had fewer femoral pro-inflammatory ATMs than omnivores (3.6 ± 2.8 vs. 7.9 ± 4.4 per 100 adipocytes, respectively; P = 0.02). Omnivores had 50% greater (P = 0.01) expression of TNF mRNA in abdominal fat. We found no significant between group differences in muscle ceramide concentrations.

Conclusions

Although the sample size is small, these results may indicate that dietary patterns play a role in adipose tissue inflammation, as reflected by reduced number of femoral ATMs in obese vegetarians than obese omnivores.

The effect of L-carnitine on inflammatory mediators: a systematic review and meta-analysis of randomized clinical trials

AIM AND BACKGROUND

Reducing inflammation by nutritional supplements may help to reduce the risk of many chronic diseases. Our aim in this meta-analysis was to determine the effect of L-carnitine on inflammatory mediators including C-reactive protein (CRP), tumor necrosis factor-α (TNF-α), and interleukin-6 (IL-6).

METHODS

Our systematic search to find relevant randomized clinical trials (RCTs) was performed up to October 2018 using ISI Web of Science, Google Scholar, PubMed/Medline, and SCOPUS. In this meta-analysis, the weighted mean differences (WMD) with standard errors (SE) were used to pool the data. WMD was calculated by subtracting change-from-baseline mean values in the control group from change-from-baseline mean values in the intervention group in each study. To identify heterogeneity among studies, the I² statistic was employed. The protocol was registered with PROSPERO (No. CRD42019116695).

RESULTS

Thirteen articles were included in our systematic review and meta-analysis. The results of the meta-analysis indicated that L-carnitine supplementation was significantly associated with lower levels of CRP in comparison to controls (WMD = -1.23 mg/L; 95% CI: -1.73, -0.72 mg/dL; P < 0.0001). Also, a slight but statistically significant decrease was observed in IL-6 and TNF-α levels (WMD = -0.85 pg/dL; 95% CI: -1.38, -0.32 pg/dL; P = 0.002 and WMD = -0.37 pg/dL; 95% CI: -0.68, -0.06 pg/dL; P = 0.018, respectively).

CONCLUSION

Our results indicate that L-carnitine reduced inflammatory mediators, especially in studies with a duration of more than 12 weeks. Further studies with different doses and intervention durations and separately in men and women are necessary.

Cancer and comorbidity: The role of leptin in breast cancer and associated pathologies

Obesity is an important risk factor for postmenopausal breast cancer and also a poor prognostic factor among cancer patients. Moreover, obesity is associated with a number of health disorders such as insulin resistance/type-2 diabetes mellitus, hypertension, and other cardiovascular diseases. Frequently, these health disorders exhibit as components/complications of the metabolic syndrome. Nevertheless, obesity-related diseases may coexist with postmenopausal breast cancer; and these comorbid conditions could be substantial. Therefore, it may be assumed that different diseases including breast cancer could originate from a common pathological background in excessive adipose tissue. Adipocyte-released hormone-like cytokine (or adipokine) leptin behaves differently in a normal healthy state and obesity. A growing body of evidence suggests an important role of leptin in our major obesity-related health issues such as insulin resistance, hypertension, and neoplasia. In this context, this review describes the relationships of the abovementioned pathologies with leptin.

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.

Assessing the Levels of L-Carnitine and Total Antioxidant Capacity in Adults With Newly Diagnosed and Long-Standing Type 2 Diabetes

OBJECTIVES

This study is essentially a correlative study that examines the potential of reduced levels of L-carnitine (LC) when combined with the pathophysiology of type 2 diabetes. The aim of the study was to assess the levels of LC, total antioxidant capacity (TAOC), fasting blood sugar (FBS), triglycerides and cholesterol in people with newly diagnosed and long-standing type 2 diabetes and in healthy controls.

METHODS

The study was done in 90 adult subjects, including 30 with newly diagnosed diabetes, 30 with long-standing type 2 diabetes and 30 healthy controls. Plasma samples were used to assay the biochemical parameters.

RESULTS

In this study, both groups (newly diagnosed and long-standing type 2 diabetes) were significantly different in baseline characteristics, such as age, height, weight, body mass index, FBS, cholesterol and triglycerides, compared to the healthy controls. Plasma LC levels in patients with newly diagnosed and long-standing type 2 diabetes were significantly lower than in healthy controls (p<0.001). Also, the mean plasma TAOC level in the patients with newly diagnosed and long-standing type 2 diabetes was slightly lower than in the healthy controls. Nevertheless, TAOC levels were not significantly different across all the groups (p=0.87). The plasma LC levels were significantly positive when compared to the plasma TAOC levels (r=0.516), which means that an increase in LC levels is associated with an increase in TAOC levels. However, a negative correlation was observed between LC levels and FBS (r=-0.387), triglycerides (-0.159) and body mass indexes (r=-0.068). This means that a decrease in LC levels is associated with increases in FBS, triglyceride and body mass index levels.

CONCLUSIONS

According to the effects of reduced LC levels on the metabolic profiles of patients with long-standing type 2 diabetes, setting the LC content value to prevent diabetes through the use of effective drugs or nutrition containing LC can be useful in managing diabetes.

l-Carnitine Supplementation in Older Women. A Pilot Study on Aging Skeletal Muscle Mass and Function

Skeletal muscle wasting, associated with aging, may be regulated by the inflammatory cytokines as well as by insulin-like growth factor 1 (IGF-1). l-carnitine possesses anti-inflammatory properties and increases plasma IGF-1 concentration, leading to the regulation of the genes responsible for protein catabolism and anabolism. The purpose of the present study was to evaluate the effect of a 24-week l-carnitine supplementation on serum inflammatory markers, IGF-1, body composition and skeletal muscle strength in healthy human subjects over 65 years of age. Women between 65 and 70 years of age were supplemented for 24 weeks with either 1500 mg l-carnitine-l-tartrate or an isonitrogenous placebo per day in a double-blind fashion. Before and after the supplementation protocol, body mass and composition, as well as knee extensor and flexor muscle strength were determined. In the blood samples, free carnitine, interleukin-6, tumor necrosis factor-α, C-reactive protein and IGF-1 were determined. A marked increase in free plasma carnitine concentration was observed due to l-carnitine supplementation. No substantial changes in other parameters were noted. In the current study, supplementation for 24 weeks affected neither the skeletal muscle strength nor circulating markers in healthy women over 65 years of age. Positive and negative aspects of l-carnitine supplementation need to be clarified.

Leptin Induces Oxidative Stress Through Activation of NADPH Oxidase in Renal Tubular Cells: Antioxidant Effect of L-Carnitine

Leptin is a protein involved in the regulation of food intake and in the immune and inflammatory responses, among other functions. Evidences demonstrate that obesity is directly associated with high levels of leptin, suggesting that leptin may directly link obesity with the elevated cardiovascular and renal risk associated with increased body weight. Adverse effects of leptin include oxidative stress mediated by activation of NADPH oxidase. The aim of this study was to evaluate the effect of L-carnitine (LC) in rat renal epithelial cells (NRK-52E) exposed to leptin in order to generate a state of oxidative stress characteristic of obesity. Leptin increased superoxide anion (O2 (•) -) generation from NADPH oxidase (via PI3 K/Akt pathway), NOX2 expression and nitrotyrosine levels. On the other hand, NOX4 expression and hydrogen peroxide (H2 O2 ) levels diminished after leptin treatment. Furthermore, the expression of antioxidant enzymes, catalase, and superoxide dismutase, was altered by leptin, and an increase in the mRNA expression of pro-inflammatory factors was also found in leptin-treated cells. LC restored all changes induced by leptin to those levels found in untreated cells. In conclusion, stimulation of NRK-52E cells with leptin induced a state of oxidative stress and inflammation that could be reversed by preincubation with LC. Interestingly, LC induced an upregulation of NOX4 and restored the release of its product, hydrogen peroxide, which suggests a protective role of NOX4 against leptin-induced renal damage. J. Cell. Biochem. 117: 2281-2288, 2016. © 2016 Wiley Periodicals, Inc.

Improvement of plasma adiponectin, leptin and C-reactive protein concentrations by orlistat: a systematic review and meta-analysis

AIMS

To conduct a systematic review and meta-analysis of relevant randomized clinical trials (RCTs) to ascertain the effect size of orlistat in modulating plasma levels of adipokines, ghrelin and C-reactive protein (CRP).

METHODS

Medline, SCOPUS, Web of Science and Google Scholar databases were searched. A random-effects model and the generic inverse variance method were used for quantitative data synthesis. Heterogeneity was quantitatively assessed using I(2) index. Sensitivity analyses were conducted using the one-study remove approach. Random-effects meta-regression was performed using unrestricted maximum likelihood method to evaluate the impact of duration of treatment, percentage change in body mass index (BMI) and baseline BMI values as potential confounders of the estimated effect size.

RESULTS

Meta-analysis suggested a significant increase in plasma levels of adiponectin [weighted mean difference (WMD): 19.18%, 95% confidence interval (CI): 5.80, 32.57, p = 0.005] and significant reductions in plasma levels of leptin (WMD: -13.24%, 95% CI: -20.69, -5.78, p = 0.001) and CRP (WMD: -11.52%, 95% CI: -16.55, -6.49, p < 0.001) following treatment with orlistat. In meta-regression, changes in plasma concentrations of adiponectin, leptin and CRP were associated with duration of treatment, but not with either change in BMI or baseline BMI values.

CONCLUSION

Orlistat is effective in increasing plasma concentrations of adiponectin and decreasing those of leptin and CRP.

Effects of l-Carnitine Supplementation on Serum Inflammatory Factors and Matrix Metalloproteinase Enzymes in Females with Knee Osteoarthritis: A Randomized, Double-Blind, Placebo-Controlled Pilot Study

OBJECTIVE

Considering the importance of inflammation in the pathogenesis of osteoarthritis (OA) and induction of pain, this study was aimed to investigate the effect of L-carnitine supplementation on serum inflammatory mediators and OA-associated pain in females with knee OA.

METHODS

In this clinical trial, 72 females with mild to moderate knee osteoarthritis started the study, divided into 2 groups to receive 750 mg/day L-carnitine (n = 36) or placebo (n = 36) for 8 weeks. Serum levels of Interleukine-1β (IL-1β), high-sensitivity C-reactive protein (hs-CRP), matrix metalloproteinases (MMPs)-1 and -13, and visual analog scale (VAS) for pain were assessed before and after supplementation. Data were analyzed by t test, Wilcoxon signed rank test, Mann-Whitney U test, and analysis of covariance.

RESULTS

Only 69 patients (33 in the L-carnitine group and 36 in the placebo group) completed the study. L-Carnitine supplementation decreased serum IL-1β and MMP-1 levels significantly (p = 0.001 and p = 0.021, respectively); however, serum hs-CRP and MMP-13 levels did not change significantly (p > 0.05). In the placebo group, serum IL-1β levels increased significantly (p = 0.011), whereas other studied biomarkers did not change significantly. The mean VAS score decreased significantly in the L-carnitine and placebo groups by 52.67% and 21.82%, respectively (p < 0.001). Significant differences were only observed between the 2 groups in serum IL-1β (p < 0.001) and MMP-1 (p = 0.006) levels and mean VAS score (p = 0.002) after adjusting for baseline values and covariates.

CONCLUSION

Despite observed beneficial effects of short-term supplementation of L-carnitine in decreasing serum inflammatory mediators and improving pain in knee OA patients, further studies are needed to achieve concise conclusions.

Nutraceuticals for the treatment of metabolic diseases: evidence from clinical practice

The aim of this review is to describe some types of supplements that have been shown to be good co-adjuvants along with diet and drug treatment in improving insulin resistance and dyslipidemia. We can conclude that some nutraceuticals, such as l-carnitine, berberine, omega-3 polyunsaturated fatty acids, krill oil and red yeast rice, can be helpful in reducing hypercholesterolemia or insulin resistance, as reported in clinical trials. Nutraceuticals can be associated with conventional pharmacological treatments to achieve an improved lipid profile without increasing statin dosage. Similarly, although nutraceuticals cannot replace conventional antidiabetic treatments, they may be useful as an adjuvant to standard therapy, improving insulin resistance. However, not all nutraceuticals are the same and their natural origin does not mean that everyone can take them or that they cannot be dangerous; nutraceuticals should be used only under medical prescription and should be combined with a well-balanced diet.

How effective are antioxidant supplements in obesity and diabetes?

Obesity is a central health issue due to its epidemic prevalence and its association with type 2 diabetes and other comorbidities. Obesity is not just being overweight. It is a metabolic disorder due to the accumulation of excess dietary calories into visceral fat and the release of high concentrations of free fatty acids into various organs. It represents a state of chronic oxidative stress and low-grade inflammation whose intermediary molecules may include leptin, adiponectin and cytokines. It may progress to hyperglycemia, leading to type 2 diabetes. Whether or not dietary antioxidant supplements are useful in the management of obesity and type 2 diabetes is discussed in this review. Only the benefits for obesity and diabetes are examined here. Other health benefits of antioxidants are not considered. There are difficulties in comparing studies in this field because they differ in the time frame, participants' ethnicity, administration of antioxidant supplements, and even in how obesity was measured. However, the literature presents reasonable evidence for marginal benefits of supplementation with zinc, lipoic acid, carnitine, cinnamon, green tea, and possibly vitamin C plus E, although the evidence is much weaker for omega-3 polyunsaturated fatty acids, coenzyme Q10, green coffee, resveratrol, or lycopene. Overall, antioxidant supplements are not a panacea to compensate for a fast-food and video-game way of living, but antioxidant-rich foods are recommended as part of the lifestyle. Such antioxidant foods are commonly available.

Dietary and nutraceutical approach to type 2 diabetes

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

Effects of berberine on lipid profile in subjects with low cardiovascular risk

OBJECTIVE

To evaluate the efficacy as antihypercholesterolemic agent of berberine in patients with low cardiovascular risk.

RESEARCH DESIGN AND METHODS

144 Caucasian subjects were enrolled. After a 6-month run-in period following diet and practicing physical activity, patients were randomized to take placebo or berberine 500 mg twice a day, for 3 months, in a double-blind, placebo-controlled design. Berberine and placebo were then interrupted for 2 months (washout period), and all patients continued with only diet and physical activity. At the end of the washout period, patients restarted berberine or placebo twice a day for further 3 months. Anthropometric and metabolic parameters were assessed during the run-in period, at randomization, before and after the washout period.

RESULTS

A decrease of body weight and BMI was observed after the run-in period. Berberine reduced total cholesterol, triglycerides and LDL cholesterol and increased HDL cholesterol after 3 months from randomization and compared with placebo. After the washout period, lipid profile worsened; afterward, when berberine was reintroduced, lipid profile improved again both compared with the washout period, and with placebo.

CONCLUSIONS

Berberine is effective and safe to mildly improve lipid profile in subjects with low risk for cardiovascular disease.

Anti-obesity drugs: a review about their effects and their safety

INTRODUCTION

Amphetamines, rimonabant and sibutramine licenses as anti-obesity drugs have been withdrawn because of their adverse effects. In fact, orlistat is the only available long-term treatment for obesity.

AREAS COVERED

The efficacy and safety of long-term drug therapy is very important in the management obesity; for this reason, the authors decided to conduct a review on the efficacy and safety of current, past and future pharmacotherapies for weight loss.

EXPERT OPINION

Orlistat is a good choice for the treatment of obesity, because of its safety on cardiovascular events and its positive effects on diabetic control, even if it is not as effective as rimonabant or sibutramine in reducing body weight. Regarding emerging anti-obesity therapies in diabetic people, we currently have drugs that have already been marketed including the glucagon-like peptide-1 (GLP-1) receptor agonists exenatide and liraglutide; other than improving glycemic control, they also suppress appetite reducing body weight. Moreover, some other drugs are currently in study such as tesofensine, phentermine + topiramate, bupropion + naltrexone and bupropion + zonisamide. Furthermore, several additional gut hormone-based treatments for obesity are under investigation in Phase II and III clinical trials, with particular focus on ghrelin, peptide YY, pancreatic polypeptide, amylin and oxyntomodulin.