D-Asparagine is an Ideal Endogenous Molecule for Measuring the Glomerular Filtration Rate
Ayumu Taniguchi, Masataka Kawamura, Shinsuke Sakai, Shihoko Kimura‐Ohba, Yôko Tanaka, Shota Fukae, Ryo Tanaka, Shigeaki Nakazawa, Kazuaki Yamanaka, Masaru Horio, Shiro Takahara, Norio Nonomura, Yoshitaka Isaka, Ryoichi Imamura, Tomonori Kimura
Abstract
Introduction: An ideal endogenous molecule for measuring glomerular filtration rate (GFR) is still unknown. However, a rare enantiomer of serine, d-serine, is useful in GFR measurement. This study explored the potential of other d-amino acids for kidney function assessment. Methods: This was a cross-sectional observational study of 207 living kidney transplant donors and recipients, for whom GFR was measured using clearance of inulin (C-in). Associations between levels of d-amino acids and GFR were analyzed using multivariate factor analysis. Fractional excretion (FE), a ratio of the clearance of a substance to C-in as a standard molecule, was calculated to monitor the excretion ratio after glomerular filtration. Dissociation from an ideal FE of 100% was assessed as a bias. Proportional bias against C-in was calculated using Deming regression. Results: < 0.001). A proportional bias of C-d-Asn to C-in was -7.8% (95% CI, -14.5 to -0.6%), which was minor compared to those of clearance of creatinine (-34.5% [-37.9 to -31.0%]) and d-serine (21.2% [13.9-28.9]). Conclusion: D-Asparagine acts similar to inulin in the kidney. Therefore, d-asparagine is an ideal endogenous molecule that can be used for GFR measurement.