Role of taurine in the vasculature: an overview of experimental and human studies

Abstract

Taurine is a sulfur-containing amino acid-like endogenous compound found in substantial amounts in mammalian tissues. It exerts a diverse array of biological effects, including cardiovascular regulation, antioxidation, modulation of ion transport, membrane stabilization, osmoregulation, modulation of neurotransmission, bile acid conjugation, hypolipidemia, antiplatelet activity and modulation of fetal development. This brief review summarizes the role of taurine in the vasculature and modulation of blood pressure, based on experimental and human studies. Oral supplementation of taurine induces antihypertensive effects in various animal models of hypertension. These effects of taurine have been shown to be both centrally and peripherally mediated. Consistent with this, taurine produces endothelium-dependent and independent relaxant effects in isolated vascular tissue preparations. Oral administration of taurine also ameliorates impairment of vascular reactivity, intimal thickening, arteriosclerosis, endothelial apoptosis, oxidative stress and inflammation, associated primarily with diabetes and, to a lesser extent with obesity, hypertension and nicotine-induced vascular adverse events. In rat aortic vascular smooth muscle cells (VSMCs), taurine acts as an antiproliferative and antioxidant agent. In endothelial cells, taurine inhibits apoptosis, inflammation, oxidative stress and cell death while increasing NO generation. Oral taurine in hypertensive human patients alleviates the symptoms of hypertension and also reverses arterial stiffness and brachial artery reactivity in type 1 diabetic patients. However, despite these favorable findings, there is a need to further establish certain aspects of the reported results and also consider addressing unresolved related issues. In addition, the molecular mechanism (s) involved in the vascular effects of taurine is largely unknown and requires further investigations. Elucidation of the mechanisms through which taurine affects the vasculature could facilitate the development of therapeutic and/or diet-based strategies to reduce the burdens of vascular diseases.

Keywords: Taurine; VSMCs (vascular smooth muscle cells); atherosclerosis; diabetes; endothelial cells; hypertension; isolated vascular tissue preparations; taurine deficiency; vasorelaxation.

Figure 1

Possible sites of action of taurine as a hypotensive agent (refer to text for details).

Figure 2

Vascular effects of taurine based on experimental observations (refer to text for details).

Figure 3

Proposed mechanisms for direct vasorelaxant effects of taurine. Taurine is proposed to act as a vasorelaxant by different mechanisms as described below (refer to text for further details): (a) and (b) acting as an osmoregulator on endothelial and vascular smooth muscle cells with consequential effects on osmosensitive signaling pathways;(c) preserving and enhancing the production of NO by acting as an antioxidant and increasing eNOS expression; (d) activating K+ channels in vascular smooth muscle cells resulting in a reduction in Ca2+I; (e) reducing vascular smooth muscle cell Ca2+I by other potential mechanisms; (f) activating K+ channels in endothelial cells thereby reinforcing Ca2+entry via ROC. Abbreviation: EDHF, endothelial derived hyperpolarizing factor; NO, nitric oxide; eNOS, endothelial nitric oxide synthase; ROC, receptor-operated channel; VOC, voltage-operated channel.