Background: Despite improvements in kidney transplantation, complications, including cardiovascular morbidity and graft loss, contribute to reduced graft and patient survival. The amino acid homoarginine exerts a variety of beneficial effects that may be relevant for cardiovascular and graft outcomes, which is investigated in the present study.
Methods: Homoarginine was measured in 829 renal transplant recipients participating in the placebo group of the Assessment of Lescol in Renal Transplantation study. Mean follow-up was 6.7 years. By Cox regression analyses, we determined hazard ratios (HRs) to reach prespecified, adjudicated endpoints according to baseline homoarginine levels: major adverse cardiovascular events (n = 103), cerebrovascular events (n = 53), graft failure or doubling of serum creatinine (n = 140), noncardiovascular mortality (n = 51), and all-cause mortality (n = 107).
Results: Patients mean age was 50 ± 11 years, homoarginine concentration was 1.96 ± 0.76 μmol/L, and 65% were men. Patients in the lowest homoarginine quartile (<1.40 μmol/L) had an adjusted 2.6-fold higher risk of cerebrovascular events compared to those in the highest quartile (>2.34 μmol/L) (HR, 2.56; 95% confidence interval [95% CI], 1.13-5.82). Similarly, the renal endpoint occurred at a significantly increased rate in the lowest homoarginine quartile (HR, 2.34; 95% CI, 1.36-4.02). For noncardiovascular and all-cause mortality, there was also increased risk associated with the lowest levels of homoarginine, with HRs of 4.34 (95% CI, 1.63-10.69) and 2.50 (95% CI, 1.38-4.55), respectively.
Conclusions: Low homoarginine is strongly associated with cerebrovascular events, graft loss and progression of kidney failure and mortality in renal transplant recipients. Whether interventions with homoarginine supplementation improve clinical outcomes requires further evaluation.