Association of 24-Hour Urinary Oxalate Excretion with Cardiovascular Disease in Kidney Transplant Recipients

Background: Urinary oxalate has been associated with mortality in kidney transplant recipients (KTR). Whether urinary oxalate is a risk factor for cardiovascular disease (CVD) in kidney transplant recipients is unclear. Methods: We studied 54 stable KTR with a functioning allograft ≥1 year. Urinary oxalate excretion was determined from a 24-hour urine collection. Finger reactive hyperemic index (RHI) and aortic pulse wave velocity (PWV), both of which are predictors of CVD outcomes, were determined using EndoPAT (peripheral artery tonometry) and Sphygmocor, respectively. Linear regression was used to evaluate the association between urinary oxalate excretion and RHI and PWV. Results: The mean (SD) age and eGFR were 50.0 (14.8) years and 66.5 (16.8) ml/min/1.73m2. 75.9% were men and 25.9% had diabetes. Mean (SD) 24-hour urinary oxalate was 34.7 (14.5) mg/day. 24-hour urinary oxalate excretion was not significantly associated with RHI or aPWV in unadjusted or fully adjusted analyses, but there was a trend towards significance in the fully adjusted analyses (Table 1). Conclusion: 24-hour urinary oxalate excretion was not associated with intermediate markers of CVD. Whether impaired oxalate metabolism represents a novel therapeutic target for CVD in KTR needs to be determined in larger studies. Funding: NIDDK Support - Variable Unadjusted β-estimate (95% CI) Fully Adjusted* β-estimate (95% CI) RHI 0.003 (-0.002 to 0.01), p=0.24 0.01 (-0.0004 to 0.01), p=0.06 PWV -0.01 (-0.05 to 0.02), p=0.38 -0.03 (-0.05, to 0.002), p=0.07 *Adjusted for age, sex, race/ethnicity, history of diabetes and hypertension