Characterization of insulin adsorption behavior of dialyzer membranes used in hemodialysis

Although it has been reported that plasma insulin is removed by hemodialysis (HD), the mechanism for this has not been elucidated. We investigated the mechanism of insulin removal during HD treatment and the characteristics of insulin removal with three high-flux membranes. In our in vivo study, 20 stable diabetic patients on HD were randomly selected for three HD sessions with three different membranes: polysulfone (PS), cellulose triacetate (CTA), and polyester polymer alloy (PEPA). Blood samples were obtained from the blood tubing at the arterial (A) site at the beginning and end of the sixth HD session to investigate insulin reduction in patients. At 1 h after the initiation of dialysis, blood samples were obtained from both the A and venous sites of the dialyzer to investigate the insulin clearance with the different membranes. There was a significant reduction in patients' plasma insulin at each time point with each of the three membranes. The insulin clearance with the PS membrane was significantly higher than that with the CTA and PEPA membranes. Although no difference was observed in the plasma insulin reduction rate between the three membranes in the total subject group, there was a significantly higher reduction rate with the PS membrane in insulin-dependent diabetes mellitus subjects. The clearance of insulin in in vitro tests was significantly higher with the PS and PEPA membranes than with the CTA membrane in both new and clinically used dialyzers. Insulin was not detected in the dialysate or ultrafiltration fluids in either the in vivo or in vitro studies. The mechanism of plasma insulin clearance by HD is mainly by adsorption, and the amount of insulin adsorbed differed depending on the dialyzer membrane used.