Protein-bound uraemic toxins, dicarbonyl stress and advanced glycation end products in conventional and extended haemodialysis and haemodiafiltration

BACKGROUND: Protein-bound uraemic toxins (PBUT), dicarbonyl stress and advanced glycation end products (AGEs) associate with cardiovascular disease in dialysis. Intensive haemodialysis (HD) may have significant clinical benefits. The aim of this study was to evaluate the acute effects of conventional and extended HD and haemodiafiltration (HDF) on reduction ratio (RR) and total solute removal (TSR) of PBUT, dicarbonyl stress compounds and AGEs. METHODS: Thirteen stable conventional HD patients randomly completed a single study of 4-h HD (HD4), 4-h HDF (HDF4), 8-h HD (HD8) and 8-h HDF (HDF8) with a 2-week interval between the study sessions. RR and TSR of PBUT [indoxyl sulphate (IS), p-cresyl sulphate (PCS), p-cresyl glucuronide, 3-carboxyl-4-methyl-5-propyl-2-furanpropionic acid (CMPF), indole-3-acetic acid (IAA) and hippuric acid] of free and protein-bound AGEs [Nepsilon-(carboxymethyl)lysine (CML), Nepsilon-(carboxyethyl)lysine (CEL), Ndelta-(5-hydro-5-methyl-4-imidazolon-2-yl)-ornithine, pentosidine], as well as of dicarbonyl compounds [glyoxal, methylglyoxal, 3-deoxyglucosone], were determined. RESULTS: Compared with HD4, HDF4 resulted in increased RR of total and/or free fractions of IAA and IS as well as increased RR of free CML and CEL. HD8 and HDF8 showed a further increase in TSR and RR of PBUT (except CMPF), as well as of dicarbonyl stress and free AGEs compared with HD4 and HDF4. Compared with HD8, HDF8 only significantly increased RR of total and free IAA and free PCS, as well as RR of free CEL. CONCLUSIONS: Dialysis time extension (HD8 and HDF8) optimized TSR and RR of PBUT, dicarbonyl stress and AGEs, whereas HDF8 was superior to HD8 for only a few compounds.