Low-molecular but not high-molecular advanced glycation end products (AGES) are removed by high-flux dialysis

Background: Patients with end-stage renal disease (ESRD) display very high levels of advanced glycation end products (AGEs). These compounds are suspected to play a pathophysiological role in diabetic nephropathy and late diabetic cardiovascular complications. We investigated to what extent AGE levels can be reduced by high-flux dialysis. Patients and methods: Ten ESRD patients were treated three times each with DIAPES and HF60, two different synthetic, high-flux hemodialysis membranes. The kinetics of AGE removal was studied by fluorescence spectroscopy (excitation 370 nm/emission 440 nm) and by ELISA of serum samples and the removal of [32-m was studied by immunonephelometry of plasma samples. Samples were taken during dialysis sessions m t = 0, 30 and 180 min. In addition, molecular weight distribution of AGE products in serum of three patients was analyzed by gel filtration and fluorescence detection. Results: A significant difference could be found when AGE levels in serum of controls (n = 10) were compared with serum AGE levels of ESRD patients (p < 0.01/fluorescence; p < 0.0001/ELISA). After 3 h of dialysis AGE-related fluorescence in serum decreased by 25.5 ± 68% for HF60 (p < 0.0001) and 24.3 ± 6.9% for DIAPES (p < 0.0001). The corresponding decline measured by ELISA was 23.3 ± 8.9% for HF60 (p < 0.0001) and 26.1 ± 7.0% for DIAPES (p < 0.0001). Both methods showed no significant differences for both types of dialysis membranes. Gel filtration revealed that the decrease of fluorescence can be attributed to the removal of AGE peptides Mth a molecular mass < 12 kDa, only. In the high molecular range (> 12 kDa) no removal but hemoconcentration was observed independent of the dialyzer type used. The reduction of 132-m during 3 hours ofdialysis was 61.8 ± 6.9% for HF60 (p < 0.000l) and 161.7 ± 7.0% for DIAPES (p < 0.0001). Conclusion: Both high-flux dialyzers were equally effective to remove low-molecular AGE products, while AGE-modified proteins of higher molecular weight were only marginally affected. On the basis of our data we suggest the study of molecular mass-dependent uremic toxicity of AGEs and the examination of the influence of other treatment modalities on the level of high-molecular AGEs.