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

Abstract

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 (I 2 ). 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%

L-Carnitine Tartrate Downregulates the ACE2 Receptor and Limits SARS-CoV-2 Infection

“…It is known that ACE2 levels in lungs and plasma are higher under inflammatory conditions [ 34 ], thus increasing the susceptibility of cells from the population suffering from the above conditions to SARS-CoV-2 infection. L-carnitine has been reported to play a regulatory role in inflammatory processes [ 22 , 23 , 38 ], and L-carnitine supplementation has beneficial effects in populations with relatively low L-carnitine levels, such as that which occurs in the elderly and in a variety of inflammatory disease states [ 25 ].…”

“…L-carnitine’s basic role is to transport fatty acids to the mitochondrial matrix, making them available for beta-oxidation and energy generation through the Krebs cycle [ 21 ]. It is also a powerful anti-oxidant and anti-inflammatory mediator [ 22 , 23 ]. At the tissue level, L-carnitine accumulates mainly in the muscle, heart, and lung tissues [ 24 ].…”

“…The elderly and people with chronic diseases (e.g., obesity, diabetes, hypertension, and cardiovascular diseases) exhibit significantly lower levels of L-carnitine in their tissues compared to the healthy population [ 25 ]. These compromised populations are prone to having chronic inflammation, which is a condition that is shown to be mitigated by L-carnitine supplementation [ 23 ]. In addition, L-carnitine has been shown to reduce ACE1 levels in a hypertensive rodent model [ 26 ], and in the context of viral infections, it decreases hepatitis C infection through an anti-lipogenic effect.…”

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

“…Moreover, in acute conditions, such as in myocardial infarction, LC could mitigate abnormal oxidative stress condition and enhance cardiomyocytes survival. Animal studies and preliminary clinical studies seem to confirm this hypothesis [195][196][197][198]. It is important to note that these first trials suggest that LC improves antioxidative cellular defense, in particular the NRF2 pathway [198].…”

“…↓ serum inflammatory mediators ↑ superoxide dismutase level ↓ inflammatory cytokines ↑ antioxidant mitochondrial enzymes Fathizadeh et al [197] Human study Heart: ↓ NF-κB signaling pathway ↑ Nrf2 levels ↓ inflammatory cytokines ↑ antioxidant mitochondrial enzymes Li et al [198] In vivo (diabetic rats) Skeletal muscle: ↑ anti-oxidative factors ↑ insulin sensitivity index ↑ metabolic profile ↑ contractile properties Samir et al [199] In vivo (NAFLD model mice)…”