Relationships among hyperuricemia, metabolic syndrome, and endothelial function.

BACKGROUND: We evaluated the relationship of the severity of hyperuricemia and the flow-mediated vasodilatation of the brachial artery (FMD) in patients with and without the metabolic syndrome (MetS).
METHODS: In a cross-sectional study, FMD was obtained in 2,732 Japanese healthy men (49 ± 8 years) who had no cardiovascular (CV) disease and were not on any medication for CV risk factors. MetS was defined according to Japanese criteria, and serum uric acid (UA) levels in the upper half of the fifth (highest) quintile range were defined as severe hyperuricemia, whereas those in the lower half of this quintile range were defined as mild hyperuricemia.
RESULTS: Overall, the adjusted values of FMD were lower in the subjects with MetS (5.6 ± 0.1%; n = 413) than in those without MetS (6.2 ± 0.1%; n = 2,319) (P < 0.01). Among the subjects without MetS, the adjusted values of FMD were lower in both the subgroups with mild hyperuricemia and severe hyperuricemia than in the subgroup without hyperuricemia. On the contrary, among the subjects with MetS, the adjusted value of FMD was lower only in the subgroup with severe hyperuricemia (4.8 ± 0.3%) as compared with that in the group without hyperuricemia (5.7 ± 0.2%) (P < 0.05).
CONCLUSIONS: In middle-aged healthy Japanese men without MetS, not only severe, but also mild hyperuricemia may be a significant independent risk factor for endothelial dysfunction in subjects without MetS, whereas only severe hyperuricemia (but not mild hyperuricemia) appeared to exacerbate endothelial dysfunction in similar subjects with MetS.