Trimethylamine-N-Oxide: A Carnitine-Derived Metabolite That Prolongs the Hypertensive Effect of Angiotensin II in Rats

doi:10.1016/j.cjca.2014.09.010

Canadian Journal of Cardiology

Volume 30, Issue 12, December 2014, Pages 1700-1705

https://doi.org/10.1016/j.cjca.2014.09.010 Get rights and content

Abstract

Background

Recent evidence suggests that an elevated plasma trimethylamine N-oxide (TMAO) level is associated with an increased risk of adverse cardiovascular events in humans; however, the mechanism is not clear. The aims of this study were to establish the plasma TMAO level in rats and to evaluate the effect of TMAO on arterial blood pressure (BP) and the hemodynamic effects of angiotensin II (Ang II).

Methods

Twelve-week-old, Sprague-Dawley rats were implanted with telemetric transmitters, and continuous recordings of heart rate, systolic BP (SBP), and diastolic BP (DBP) were made for 7 days before and 14 days during osmotic minipump-driven subcutaneous infusion of saline (controls), TMAO, low-dose Ang II, or Ang II + TMAO. Plasma TMAO concentration was evaluated using liquid chromatography coupled with triple-quadrupole mass spectrometry.

Results

The plasma TMAO concentration in controls was 0.57 μmol/L, whereas in TMAO-infused rats it was 58 μmol/L. Neither saline nor TMAO infusion affected SBP and DBP. Infusion of Ang II significantly increased SBP and DBP for the first 5 days of infusion only. In contrast, infusion of Ang II + TMAO produced a hypertensive response that lasted until the end of the experiment. TMAO infusions did not affect body weight and motor activity.

Conclusions

We showed that physiological plasma TMAO concentration in rats was approximately 10 times lower than that reported in humans. Furthermore, the new finding of the study is that TMAO does not affect BP in normotensive animals. However, it prolongs the hypertensive effect of Ang II.

Résumé

Introduction

Des données récentes suggèrent qu'un niveau élevé d'oxyde de triméthylamine (TMAO) plasmatique est associé à un risque accru d'incidents cardiovasculaires indésirables chez l'homme; toutefois, le mécanisme n'est pas clair. Les objectifs de cette étude étaient de déterminer le niveau de TMAO plasmatique chez le rat et d'évaluer l'effet du TMAO sur la pression artérielle (PA) et les effets hémodynamiques de l'angiotensine II (Ang II).

Méthodes

Des rats Sprague-Dawley âgés de douze semaines ont été implantés avec des émetteurs télémétriques et des enregistrements en continu de la fréquence cardiaque, la pression artérielle systolique (PAS) et diastolique (PAD) ont été réalisés 7 jours avant et pendant 14 jours durant la perfusion sous-cutanée par une mini-pompe osmotique de solution saline (contrôle), de TMAO, de faibles doses d’Ang II, ou d’Ang II + TMAO. La concentration plasmatique de TMAO a été évaluée par chromatographie liquide couplée à une détection par spectrométrie de masse à triple quadripôle.

Résultats

La concentration plasmatique de TMAO dans les échantillons contrôles était de 0,57 μmol/l, alors que chez les rats perfusés avec du TMAO elle était de 58 μmol/l. Ni la solution saline, ni la perfusion de TMAO n'a affecté la PAS ou la PAD. La perfusion d’Ang II a significativement augmenté la PAS et la PAD pour les 5 premiers jours de perfusion seulement. En revanche, la perfusion d'Ang II + TMAO a entraîné une réponse hypertensive qui a duré jusqu'à la fin de l'expérience. Les perfusions de TMAO n'ont pas affecté la masse corporelle ou l'activité motrice.

Conclusions

Nous avons montré que les concentrations plasmatiques physiologiques de TMAO chez le rat étaient environ 10 fois inférieures à celles rapportées chez l'homme. En outre, la nouvelle conclusion de l'étude est que le TMAO n'affecte pas la PA chez des animaux normotendus. Cependant, il prolonge l'effet hypertenseur de l'Ang II.

Section snippets

Methods

The experiments were performed according to Directive 2010/63/EU and approved by the Ethical Committee of the Medical University of Warsaw. We performed the study on 4 groups (n = 6 each) of male 12-week-old Sprague Dawley rats that were fed standard laboratory chow with a sodium content of 0.22%, (Labofeed H, Morawski, Poland). Rats were given ad libitum access to food and water and were housed in a 12/12-hour light-dark cycle.

Rats were implanted with telemetric transmitters (Data Sciences

Plasma levels of TMAO in rats

There were significant differences in plasma TMAO between the groups (F [3, 20] = 77.4; P < 0.05) (Table 1). Plasma concentration of TMAO in rats infused with saline was 0.57 μmol/L ± 0.09, whereas in rats infused with TMAO, it was 58 μmol/L ± 5.2.

Effects of chronic infusion of TMAO and Ang II on BP in rats

Baseline DBP and SBP were comparable between the groups (Table 1). Neither infusion of saline nor TMAO affected DBP or SBP (Fig. 1, A and B).

Infusion of Ang II significantly increased DBP (F [1, 14] = 5.1; P < 0.05] and SBP (F [1, 14] = 3.4; P <

Discussion

We have shown that the fasting plasma TMAO concentration in young healthy rats averages 0.57 μmol/L, which is approximately 10 times lower than that reported in humans. The study revealed that a 2-week 100-fold increase in blood TMAO level does not affect BP in normotensive animals. However, it prolongs the hypertensive effect of chronic low-dose Ang II infusion.

Elevated concentrations of plasma TMAO has been suggested to be a new marker of an increased risk of adverse cardiovascular events in

Conclusions

To our knowledge, this is the first study of hemodynamic effects of TMAO in rats. The results show that a 2-week 100-fold increase in blood TMAO levels does not affect BP in rats; however, it prolongs the hypertensive effect of chronic low-dose Ang II infusions. Whether TMAO plays the role of a mediator in the cause of cardiovascular diseases or whether its high concentration only coexists with factors hindering homeostasis of the circulatory system remains to be elucidated.

Acknowledgements

The authors thank Dr Tymoteusz Zera for his critical comments on the manuscript.

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Basic ResearchTrimethylamine-N-Oxide: A Carnitine-Derived Metabolite That Prolongs the Hypertensive Effect of Angiotensin II in Rats

Abstract

Background

Methods

Results

Conclusions

Résumé

Introduction

Méthodes

Résultats

Conclusions

Section snippets

Methods

Plasma levels of TMAO in rats

Effects of chronic infusion of TMAO and Ang II on BP in rats

Discussion

Conclusions

Acknowledgements

Metabolism

Lancet

Comp Biochem Physiol A Mol Integr Physiol

J Nutr Biochem

J Nutr

Pharmacol Rep

Neuropeptides

Gut flora metabolism of phosphatidylcholine promotes cardiovascular disease

Nature

Intestinal microbial metabolism of phosphatidylcholine and cardiovascular risk

N Engl J Med

Intestinal microbiota metabolism of L-carnitine, a nutrient in red meat, promotes atherosclerosis

Nat Med

Diet and lifestyle recommendations revision 2006: A scientific statement from the American Heart Association Nutrition Committee

Circulation

Role of angiotensin II in cardiovascular disease therapeutic implications of more than a century of research

J Renin Angiotensin Aldosterone Syst

Basic Research
Trimethylamine-N-Oxide: A Carnitine-Derived Metabolite That Prolongs the Hypertensive Effect of Angiotensin II in Rats