A Pilot Study on the Effects of l-Carnitine and Trimethylamine-N-Oxide on Platelet Mitochondrial DNA Methylation and CVD Biomarkers in Aged Women

Abstract

l-carnitine supplementation has been used for cardiovascular health protection for a long time. Recently, trimethylamine-N-oxide (TMAO), which is an end product of l-carnitine metabolism via the activity of microbiota, has been identified as a cardiovascular disease (CVD) biomarker. The aim of this study was to assess the effect of 6 months of l-carnitine supplementation in a group of aged women engaged in a regular physical training. Platelet mitochondrial DNA methylation, an emerging and innovative biomarker, lipid profile and TMAO levels have been measured. TMAO increased after l-carnitine supplementation (before 344.3 ± 129.8 ng/mL vs. after 2216.8 ± 1869.0 ng/mL; n = 9; paired t-test, p = 0.02). No significant effects on TMAO were exerted by training alone (n = 9) or by l-leucine supplementation (n = 12). TMAO levels after 6 months of l-carnitine supplementation were associated with higher low-density lipoprotein-cholesterol (LDL-c) (Spearman Rho = 0.518, p = 0.003) and total cholesterol (TC) (Spearman Rho = 0.407, p = 0.026) levels. l-carnitine supplementation increased D-loop methylation in platelets (+6.63%; paired t-test, p = 0.005). D-loop methylation was not directly correlated to the TMAO augmentation observed in the supplemented group, but its increase inversely correlated with TC (Pearson coefficient = −0.529, p = 0.029) and LDL-c (Pearson coefficient = −0.439, p = 0.048). This evidence supports the hypothesis that the correlation between l-carnitine, TMAO and atherosclerosis might be more complex than already postulated, and the alteration of mitochondrial DNA (mtDNA) methylation in platelets could be involved in the pathogenesis of this multifactorial disease.

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

“…In the selected studies, participants were supplemented in a dose ranging from 1 g to 4,5 g per day for either 12 or 24 weeks, mostly by L-carnitine-L-tartrate (LCLT). In three studies, supplementations were combined with carbohydrates (CHO) [ 5 – 7 ], and in one with L-leucine [ 18 ].…”

“…In two studied groups of healthy aged woman, LC supplementation alone [ 16 , 17 ], or in combination with L-leucine [ 18 ], induced an increase of fasting plasma TMAO levels. However, higher TMAO was not associated with determined inflammatory [ 16 ] nor oxidative stress [ 17 ] markers.…”

“…However, higher TMAO was not associated with determined inflammatory [ 16 ] nor oxidative stress [ 17 ] markers. Moreover, despite elevated TMAO, LC supplementation together with resistance training induced positive changes in mitochondrial DNA methylation of platelets [ 18 ].…”

“…Similar observations were noted in later human studies [ 56 , 57 ], with the peak serum TMAO observed within hours following oral administration of the tracer [ 56 ]. Prolonged LC treatment elevates fasting plasma TMAO [ 16 – 18 , 58 , 59 ]. Three months of oral LC supplementation in healthy aged women induced ten-fold increase of fasting plasma TMAO, and this level remained elevated for the further 3 months of supplementation [ 16 ].…”

“…Although the optimal dose of LC supplementation for myocardial infarction is 3 g/day in terms of all-cause mortality [ 90 ], even lower LC intake elevates fasting plasma TMAO [ 16 – 18 , 58 , 59 ], which is ten-fold higher than control after 3 months of supplementation [ 16 , 17 ]. It is worthy to mention that Bakalov et al [ 91 ] analyzing European Medicine Agency database of suspected adverse drug reaction, noticed 143 cases regarding LC.…”