Mitochondrial DNA copy number and trimethylamine levels in the blood: new insights on cardiovascular disease biomarkers

Abstract

Among cardiovascular disease (CVD) biomarkers, the mitochondrial DNA copy number (mtDNAcn) is a promising candidate. A growing attention has been also dedicated to trimethylamine-N-oxide (TMAO), an oxidative derivative of the gut metabolite trimethylamine (TMA). With the aim to identify biomarkers predictive of CVD, we investigated TMA, TMAO and mtDNAcn in a population of 389 coronary artery disease (CAD) patients and 151 healthy controls, in association with established risk factors for CVD (gender, age, hypertension, smoking, diabetes, glomerular filtration rate (GFR)). MtDNAcn was significantly lower in CAD patients and in hypertensive subjects; it correlates with GFR and TMA, but not with TMAO. A biomarker including mtDNAcn, gender, and hypertension (but neither TMA nor TMAO) emerged as a good predictor of CAD. Our findings support the usage of mtDNAcn as a plastic biomarker to monitor the exposure to risk factors and the efficacy of preventive interventions for a personalized CAD risk reduction.Highlights-mtDNAcn measured in whole blood is associated to the cardiovascular health status in humans;-mtDNAcn is reduced in CAD and hypertension, and inversely correlates with GFR;-mtDNA, gender and hypertension together represent a good predictive biomarker for CAD;-TMA metabolism is different in healthy and CAD subjects;-TMA and TMAO are not good predictors of CAD.

Diet, Trimethylamine Metabolism, and Mitochondrial DNA: An Observational Study

“…These findings are in line with evidence obtained to this date, which suggests that low TMA levels and high TMAO/TMA ratio may constitute a risk factor for complex multifactorial pathologies, such as cardiovascular diseases. [ 10,62 ] Since most of the previous research focused on circulating TMAO levels without measuring TMA, the results of this study support the hypothesis that the measurement of the TMAO/TMA ratio may be more informative than of TMAO alone.…”

“…Relative mtDNAcn quantification was performed by means of real‐time PCR (Biorad CFX96, USA) considering nDNA as a normalizer, according to the previously published data. [ 10,92 ] Since the amount of mtDNA amplified in each sample was normalized to the amount of nDNA, relative mtDNAcn was determined by the ΔCt method (2 –ΔCt ). All DNA samples were processed under the same conditions and using an identical DNA extraction method, since its variations might affect the evaluation of mtDNAcn.…”

“…All DNA samples were processed under the same conditions and using an identical DNA extraction method, since its variations might affect the evaluation of mtDNAcn. [ 92,93 ] The relative quantification was a commonly used method for mtDNAcn assessment, [ 10,93–99 ] which was useful to compare the mtDNAcn between different samples in the same study, but did not provide an absolute quantification of this parameter. The mitochondrial primers were validated by Fazzini et al.…”

“…[ 8,9 ] In spite of the complexity of this context, a robust body of literature associated circulating levels of mtDNAcn to metabolic and cardiovascular health. [ 10–13 ] Nevertheless, conflicting results concerning the direction of this association emerged, [ 14 ] and the reason why mtDNAcn is associated to health outcomes is still to be completely elucidated. Remarkably, it has been shown that mtDNA might also be methylated, [ 15–17 ] and the identification of the mitochondrial isoform of the DNA methyl‐transferase 1 (DNMT1) supported this hypothesis.…”

The Accumulation and Molecular Effects of Trimethylamine N-Oxide on Metabolic Tissues: It’s Not All Bad

“…Deleterious kidney mechanisms including reduced glomerular filtration rate, fibrosis, and loss of tubular function are associated with elevated serum TMAO [ 55 , 150 , 151 ]. One study on coronary artery disease patients showed a relationship between TMA levels and glomerular filtration rate [ 152 ]. In treating CKD, loop diuretics aggravate the elevated TMAO levels whereas renal transplantation dramatically reduces levels, highlighting that proper renal filtration is sufficient to limit TMAO accumulation [ 67 , 153 , 154 ].…”