Consumption of polyphenol-rich juar tea increases endothelium-bound extracellular superoxide dismutase levels in men with metabolic syndrome: link with LDL oxidizability

Abstract

Endothelium-bound extracellular superoxide dismutase (eEC-SOD), a major antioxidative enzyme in the vasculature, is involved in anti-atherogenesis by inhibiting low-density lipoprotein (LDL) oxidation. The objective was to investigate whether the polyphenol-rich juar tea had beneficial effects on LDL oxidation and eEC-SOD levels in patients with metabolic syndrome (MetS). A total of 20 men with MetS participated in a randomized cross-over trial, comparing consumption of five cups/day of juar tea with that of a polyphenol-poor tea, barley tea, for 4 weeks. Although there was no change in LDL oxidizability after consumption of either tea, juar tea significantly increased eEC-SOD levels by 16% (p < 0.05), whereas barley tea significantly decreased levels by 15% (p < 0.05). It is noteworthy that the changes in eEC-SOD were positively associated with those in LDL oxidizability after tea consumption (r ² = 0.11, p < 0.05). Tea polyphenols may provide anti-atherosclerotic effects by inhibiting LDL oxidation through EC-SOD bound to the endothelium.

Keywords::

• tea polyphenol
• endothelium-bound EC-SOD
• LDL oxidizability
• metabolic syndrome

Acknowledgements

The authors wish to thank Ken Ohtsuki, Mayumi Saito and Kazuhisa Inai of the Maizuru Medical Service Unit, Japan Maritime Self Defense Force, and Keiko Higuchi, Takayuki Tanaka, and Yasuyuki Ikeda of the Japan Self Defense Force Maizuru Hospital for their technical assistance.

Declaration of interest The authors report no conflicts of interest. The authors alone are responsible for the content and writing of the paper.