A circulating beta 2-microglobulin intermediate in hemodialysis patients.

BACKGROUND/AIMS: A misfolded beta(2)-microglobulin (beta(2)m) is a principle component in dialysis-related amyloidosis. However, no such conformational variant of beta(2)m has yet been reported in a clinical setting. Capillary electrophoresis is a tool that can identify the conformational variant of beta(2)m.

METHODS: Capillary electrophoresis was used to measure a transitional intermediate from native beta(2)m (N-beta(2)m) to the amyloid beta(2)m. This technique was utilized to assay for intermediate beta(2)m (I-beta(2)m) in serum from 31 hemodialysis (HD) patients before and after HD, 5 patients with non-dialysis chronic renal failure (CRF), and 5 healthy persons.

RESULTS: The predialysis values of serum I-beta(2)m and N-beta(2)m were 2.7 +/- 1.4 and 29.4 +/- 6.8 mg/l, respectively, in the HD patients. The presence of serum I-beta(2)m correlated weakly with the total serum beta(2)m concentration in all HD patients. The serum N-beta(2)m concentration decreased significantly during two types of dialysis treatment: by 32.8% on HD using a polymethylmethacrylate (PMMA) membrane and by 71.2% on online hemodiafiltration (HDF) with a polysulfone (PS) membrane. On the other hand, a dialysis-associated change in serum I-beta(2)m varied from -36.4 to +203.5% in HD patients using PMMA and from -70.8 to +62.5% in online HDF patients using PS. Moreover, a rebound beta(2)m profile suggested that I-beta(2)m might be immobilized in the extracellular space.

CONCLUSION: This study demonstrated that two or three conformational isomers of beta(2)m were probably ubiquitously recognized in human serum. Though no progressive increase in serum I-beta(2)m concentration could be found along with HD, this study shows a significantly poor removal of I-beta(2)m in comparison to N-beta(2)m in patients receiving ongoing dialysis treatment, even with online HDF.