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.