Associations of Parameters of the Tryptophan–Kynurenine Pathway with Cardiovascular Risk Factors in Hypertensive Patients

Abstract

Accumulating evidence suggests an association of the tryptophan–kynurenine (TRP-KYN) pathway with atherosclerosis and cardiovascular risk factors. In this cross-sectional analysis we investigated whether TRP-KYN pathway parameters are associated with 24 h blood pressure (BP) and other risk factors in patients with arterial hypertension from a tertiary care centre. In 490 participants, we found no significant and independent association of 24 h systolic and diastolic BP with parameters of the TRP-KYN pathway. However, linear regression analyses of HDL as dependent and TRP, KYN and quinolinic acid (QUIN) as explanatory variables adjusted for BMI and sex showed significant associations. These were found for KYN, BMI and sex (unstandardised beta coefficient −0.182, standard error 0.052, p < 0.001; −0.313 (0.078), p < 0.001; −0.180 (0.024), p < 0.001, respectively) as well as for QUIN, BMI and sex (−0.157 (0.038), p < 0.001; −0.321 (0.079), p < 0.001; −0.193 (0.024), p < 0.001, respectively). Smokers had significantly lower levels of KYN (2.36 µmol/L, IQR 2.01–2.98, versus 2.71 µmol/L, IQR 2.31–3.27, p < 0.001), QUIN (384 nmol/L, IQR 303–448, versus 451 nmol/L, IQR 369–575, p < 0.001) and KYN/TRP ratio (38.2, IQR 33.7–43.2, versus 43.1, IQR 37.5–50.9, p < 0.001) compared to non-smokers. We demonstrated that TRP/KYN pathway metabolites are associated with some cardiovascular risk factors, warranting further studies to elucidate the diagnostic and therapeutic potential of the TRP-KYN pathway for cardiovascular diseases.