Rate of Synthetic Oligosaccharide Degradation as a Novel Measure of Amylase Activity in Peritoneal Dialysis Patients

Abstract

BackgroundPlasma α–amylase activity is elevated in uremic patients but lower in peritoneal dialysis (PD) patients using icodextrin in comparison to healthy controls. We studied the rate by which an exogenous oligosaccharide (maltoheptaose; G7) is degraded ex vivo by amylase in plasma from PD patients treated with glucose or icodextrin PD solutions.MethodsPlasma amylase (pancreatic and total) activity and concentration were measured in 11 controls and in PD patients treated with glucose ( n = 11) and icodextrin ( n = 19). The plasma was spiked with G7 and/or synthetic amylase and the metabolites formed were measured by HPLC following incubation at 37°C for 4 hours.ResultsThe relationship between amylase activity and amylase concentration was similar in all patients and controls. The G7 degradation rate was slower in plasma from icodextrin patients but it was also reduced in patients using glucose compared with the controls, in spite of the higher amylase activity in the glucose group. Normalization (by spiking) of patient plasma with porcine amylase increased but did not normalize the speed of G7 degradation. At a given endogenous amylase activity level, the efficiency of G7 degradation was similar for both patient groups.ConclusionsAn ex vivo model to study the relationship between amylase activity and the actual rate of carbohydrate (represented by G7) breakdown was developed and showed that PD patients using glucose and icodextrin degrade G7 at a slower speed than controls. This suggests that amylase-mediated carbohydrate metabolism is reduced in PD patients. Further clinical studies are needed to confirm if these findings hold true also in other groups of uremic patients with varying degrees of kidney failure, as well as in patients undergoing hemodialysis.