Evidence for Targeting Low-Molecular-Weight Proteins in Hemodialysis and Hemodiafiltration

Background: With the identification of β 2 -microglobulin (β 2 MG) as an active participant in dialysis-related amyloid fibril formation, low-molecular-weight proteins (LMWPs) are now recognized as a distinct class of uremic toxins, and numerous compounds in this category have been identified. The class of LMWPs, although not precisely defined, has a molecular weight range of approximately 1,000-50,000 Da. With this in mind, dialysis prescriptions have been modified to increase the efficiency of uremic solute removal. Many studies have characterized the dialytic removal of β 2 MG and it is therefore regarded as a surrogate for LMWPs. Summary: In Japan, dialysis membranes that can efficiently remove β 2 MG are recommended. Recently, researchers have reported that β 2 MG is not only a uremic toxin that should be removed, but also a predictor of the prognosis of dialysis patients. In Japan, hemodiafiltration (HDF), especially on-line HDF, and protein-permeable hemodialysis (HD) is being actively carried out, and it is often reported that prognosis is improved by decreasing the concentrations of substances larger than β 2 MG. It is important, then, that dialysis prescriptions achieve effective clearance of such substances. Key Messages: Over 2,000 uremic substances have been identified that form or accumulate because of renal failure and cause various symptoms and complications. Focusing on these facts, HD or HDF therapy, which is associated with albumin loss, was implemented targeting the LMWPs. Here, we report the effects of albumin-losing blood purification (HD/HDF) for the purpose of removing LMWPs.