The association of plasma fluorescent oxidation products and chronic kidney disease: A case-control study

Background/Aims: Plasma fluorescent oxidation products (FLOP) constitute a stable and easily measured biomarker of cumulative oxidative stress. However, their association with chronic kidney disease (CKD) has not been studied. Methods: We examined the association of FLOP and CKD in 201 CKD patients and 201 controls without CKD from the community. CKD was defined as an estimated glomerular filtration rate (eGFR) <60 ml/min/1.73 m² or the presence of albuminuria. Results: Adjusted median (interquartile range) FLOP levels were significantly higher in patients with CKD than in controls [FLOP1 (lipid oxidation products): 215.2 (181.3-268.7) vs. 156.6 (139.6-177.3) fluorescent intensity units/ml, p < 0.0001; FLOP2 (DNA oxidation products): 534.8 (379.3-842.4) vs. 269.9 (232.4-410.5) fluorescent intensity units/ml, p < 0.0001; FLOP3 (protein and phospholipid oxidation products): 51.4 (44.4-66.0) vs. 45.2 (38.3-51.7) fluorescent intensity units/ml, p = 0.002]. Compared with those with a FLOP level below the 75th percentile, participants with a FLOP level above the 75th percentile had increased odds of CKD after adjustment for covariables (FLOP1: odds ratio 13.1, 95% confidence interval 6.2-27.6; FLOP2: odds ratio 5.7, 95% confidence interval 2.9-11.1; FLOP3: odds ratio 2.4, 95% confidence interval 1.2-4.7). Levels of FLOP1, FLOP2 and FLOP3 were related to eGFR (p < 0.0001 for all) and log-transformed urine albumin (p < 0.005 for all) in multivariable-adjusted linear regression models. Conclusion: These data indicate that an elevated FLOP level is associated with CKD status and severity. Future studies are warranted to elucidate its role in the development and progression of CKD.