Date Published: August 3, 2017
Publisher: Public Library of Science
Author(s): Kazufumi Nakamura, Daiji Miura, Yukihiro Saito, Kei Yunoki, Yasushi Koyama, Minoru Satoh, Megumi Kondo, Kazuhiro Osawa, Omer F. Hatipoglu, Toru Miyoshi, Masashi Yoshida, Hiroshi Morita, Hiroshi Ito, David Jourd’heuil.
The klotho gene was identified as an “aging-suppressor” gene that accelerates arterial calcification when disrupted. Serum and vascular klotho levels are reduced in patients with chronic kidney disease, and the reduced levels are associated with arterial calcification. Intake of eicosapentaenoic acid (EPA), an n-3 fatty acid, reduces the risk of fatal coronary artery disease. However, the effects of EPA on arterial calcification have not been fully elucidated. The aim of this study was to determine the effect of EPA on arterial calcification in klotho mutant mice.
Four-week-old klotho mutant mice and wild-type (WT) mice were given a diet containing 5% EPA (EPA food, klotho and WT: n = 12, each) or not containing EPA (control food, klotho and WT: n = 12, each) for 4 weeks. Calcium volume scores of thoracic and abdominal aortas assessed by computed tomography were significantly elevated in klotho mice after 4 weeks of control food, but they were not elevated in klotho mice after EPA food or in WT mice. Serum levels of EPA and resolvin E1, an active metabolite of EPA, in EPA food-fed mice were significantly increased compared to those in control food-fed mice. An oxidative stress PCR array followed by quantitative PCR revealed that NADPH oxidase-4 (NOX4), an enzyme that generates superoxide, gene expression was up-regulated in arterial smooth muscle cells (SMCs) of klotho mice. Activity of NOX was also significantly higher in SMCs of klotho mice than in those of WT mice. EPA decreased expression levels of the NOX4 gene and NOX activity. GPR120, a receptor of n-3 fatty acids, gene knockdown by siRNA canceled effects of EPA on NOX4 gene expression and NOX activity in arterial SMCs of klotho mice.
EPA prevents arterial calcification together with reduction of NOX gene expression and activity via GPR120 in klotho mutant mice.
Vascular calcification increases with aging and is highly prevalent in patients with atherosclerosis, diabetes mellitus and chronic kidney disease (CKD) . Coronary artery calcium assessed by computed tomography (CT) provides independent incremental information in addition to traditional risk factors for the prediction of coronary heart disease and all-cause mortality [2, 3].
Two major findings were obtained in the present study. First, EPA intake prevented arterial calcification in klotho mutant mice. Second, NOX gene expression and activity were elevated in arterial SMCs of klotho mutant mice and EPA reduced them via GPR120.