Relationship of TMAO levels with vascular function in patients with hypertension

Increased trimethylamine-N-oxide (TMAO) level is a known risk factor for hypertension. Hypertension is associated with vascular dysfunction. Recently, it has been shown that endothelial function is impaired in relation to an increase in TMAO level. However, there is no information on the relationship between TMAO levels and vascular function in patients with hypertension. The purpose of this study was to evaluate the independent variables for circulating TMAO levels and to evaluate the relationships of circulating TMAO levels with vascular function assessed by flow-mediated vasodilation (FMD) and nitroglycerine-induced vasodilation (NID) in patients with hypertension. This study was a cross-sectional study. A total of 333 subjects with hypertension were enrolled in this study. Log TMAO levels were significantly correlated with age (r = 0.24, p < 0.01), low-density lipoprotein cholesterol (r = -0.15, p < 0.01), creatinine (r = 0.28, p < 0.01), estimated glomerular filtration rate (eGFR) (r = -0.28, p < 0.01), and uric acid (r = 0.13, p = 0.02). Multiple linear regression analysis revealed that age (β = 0.17, p = 0.03), eGFR (β = -0.22, p < 0.01) and receiving three or more kinds of antihypertensive drugs (β = 0.15, p = 0.02) were independent predictors of log TMAO levels. FMD (r = -0.11, p = 0.04) and NID (r = -0.11, p = 0.04) were significantly correlated with log TMAO levels. After adjustment for confounding factors for vascular function, log TMAO level was not an independent predictor of FMD and NID. These findings suggest that circulating TMAO levels are associated with age, eGFR, and receiving three or more kinds of antihypertensive drugs but not with vascular function in patients with hypertension. Clinical Trial Registry Information: http://www.umin.ac.jp (UMIN000003409).