Asymmetric dimethylarginine attenuates the association of melatonin secretion with night-time blood pressure and dipping in elderly individuals: The HEIJO-KYO cohort

Abstract

Background: Melatonin decreases night-time blood pressure (BP) by increasing nitric oxide (NO) in endothelial cells. Whether serum asymmetric dimethylarginine (ADMA), a major endogenous competitive inhibitor of endothelial NO synthase, attenuates the association of melatonin with night-time BP and dipping in humans is unclear. Methods and Results: In this cross-sectional study of 852 community-based elderly individuals, serum ADMA, overnight urinary 6-sulfatoxymelatonin excretion (UME), and ambulatory BP were measured. Mean ADMA was 0.46±0.06 μmol/L. In the low-ADMA group (n=451), crude OR for nocturnal hypertension (NH) and non-dipper significantly decreased with a quartile increase in UME (P=0.023 and 0.001, respectively), but these associations were not observed in the high-ADMA group (n=401). Higher UME was significantly and inversely associated with adjusted OR for NH and non-dipper in the low-ADMA group (Q1, 1.00 and 1.00; Q2, 0.92 and 0.74; Q3, 0.57 and 0.51; Q4, 0.48 and 0.40; P=0.004 and 0.002, respectively) but not in the high-ADMA group (P=0.75 and 0.12, respectively). These association trends were also observed on continuous variable analysis (low ADMA, P=0.031 and 0.003; high ADMA, P=0.52 and 0.13; respectively). Conclusions: ADMA attenuates the association of endogenous melatonin with night-time BP and dipping in the general elderly population.