N -(carboxymethyl)lysine, N -(carboxyethyl)lysine and vascular cell adhesion molecule-1 (VCAM-1) in relation to peritoneal glucose prescription and residual renal function; a study in peritoneal dialysis patients

Abstract

Background. Advanced glycation end products (AGEs) may contribute to peritoneal and cardiovascular damage in peritoneal dialysis (PD) patients, possibly in part by over-expression of vascular cell adhesion molecule-1 (VCAM-1). It has been suggested that peritoneal glucose load, oxidative stress, as well as the uraemic state itself may lead to an increased formation of AGEs. Aims of the present study were first to investigate the relation between residual glomerular filtration rate (rGFR), malondialdehyde (MDA) as a marker of lipid peroxidation, and peritoneal glucose prescription and absorption with serum levels of VCAM-1 and with the well characterized AGEs N^ϵ-(carboxymethyl)lysine (CML) and N^ϵ-(carboxyethyl)lysine (CEL), as well as with CML and CEL in peritoneal effluent. Methods. CML and CEL were measured by tandem mass spectroscopy, MDA by HPLC, and VCAM-1 by ELISA in 37 stable PD patients (age 54 ± 12 years; time on PD 25 ± 18 months). CML and CEL were also measured after a 4-month interval. Results. rGFR was independently related to CML both in serum (r = –0.66; Pr = –0.62; Pr = 0.49; Pr = 0.44; Pr = 0.37; Pr = –0.40; Pr = 0.37; Pr = 0.38; PConclusion. Peritoneal glucose prescription and absorption, as well as rGFR are related to serum and effluent levels of CML and to VCAM-1 expression in serum, whereas peritoneal glucose absorption was related to serum levels of CEL. Still, the effect of rGFR, which does not appear to be mediated through lipid peroxidation pathways, on effluent levels of CML appears to outweigh the effect of the PD treatment. Even small differences in residual renal function in patients already on dialysis therapy are related to large variations of CML in serum and the peritoneal cavity.