Determination of high and low molecular weight molecules of icodextrin in plasma and dialysate, using gel filtration chromatography, in peritoneal dialysis patients.

OBJECTIVE: The aim of this study was to apply high performance liquid chromatography (HPLC) with modern gel filtration media to determine high molecular weight (HMW) icodextrin fractions and low molecular weight (LMW) icodextrin metabolites in dialysate and plasma in peritoneal dialysis (PD) patients on treatment with icodextrin, and to explore the potential relationships between these compounds, alpha-amylase activity, and glomerular filtration rate. DESIGN: Retrospective study of dialysate and plasma samples from PD patients. SETTING: Samples were collected at one PD center. PATIENTS: Blood and dialysate samples were obtained from PD patients who were subdivided into three groups: patients using only glucose-based peritoneal dialysis fluid (GPDF; GLU group, n = 23), patients studied after the first long dwell with icodextrin-based peritoneal dialysis fluid (IPDF; 1st ICO group, n = 24), and patients who were regular users of IPDF for the long dwells (ICO group, n = 9). METHODS: LMW icodextrin metabolites [i.e., maltose (G2), maltotriose (G3), maltotetraose (G4), maltopentaose (G5), maltohexaose (G6), and maltoheptaose (G7)] and HMW fractions were determined in plasma and dialysate using two different gel filtration HPLC methods. Enzymatic hydrolysis with amyloglucosidase to glucose yielded the total carbohydrate content and this was used to validate the HPLC results. alpha-Amylase activity was determined using a routine method. RESULTS: The results obtained by gel filtration HPLC yielded values of LMW metabolites and HMW fractions in plasma and dialysate in agreement with results obtained with enzymatic hydrolysis. HMW fractions were not detectable in plasma. Absorption of icodextrin from the peritoneal cavity during the long dwell (10 - 16 hours) was, on average, 39% of the amount instilled. During the long dwell, there was a relative decrease in the dialysate concentration of the largest HMW fractions (>21.4 kDa). Plasma concentration of the LMW icodextrin metabolites G2-G7 was highest in the ICO group (2.65+/-0.54 mg/mL) but also higher in the 1st ICO group (1.97+/-0.57 mg/mL) compared with the GLU group (0.52+/-0.23 mg/mL). Plasma alpha-amylase activity was significantly lower in the 1st ICO group and in the ICO group compared with the GLU group. CONCLUSIONS: Accurate analysis of HMW icodextrin fractions in dialysate and LMW icodextrin metabolites in plasma and dialysate in PD patients can be achieved by gel filtration HPLC with two different columns. This method can be used to study the complex pattern of changes in icodextrin and its metabolites in plasma and dialysate. The finding that HMW icodextrin fractions were not detected in plasma was unexpected, and differs from results of previous studies by other researchers.     

Intima media thickness in children undergoing dialysis

Background

Uremic vasculopathy, including vascular calcification, increases the risk for cardiovascular disease and mortality in chronic kidney disease (CKD) patients. We have investigated the prevalence and factors associated with vasculopathy in children undergoing peritoneal dialysis (PD) or hemodialysis (HD) in a single center.

Methods

Common carotid intima media thickness (cIMT) and its relation with demographics, biochemical parameters and medication was analyzed in 60 patients (mean age 12.9?±?3.4?years; 27 girls) treated with PD (n?=?31) or HD (n?=?29) for 34?±?34?months. Patients were divided into two groups: normal cIMT and increased cIMT.

Results

Mean levels of calcium, phosphate and calcium/phosphate product were in the normal range, the but parathyroid hormone level, 729?±?670?pg/mL, was higher than the National Kidney Foundation Kidney Disease Outcome Quality Iniative (K/DOQI) recommendations. Twenty-nine patients had increased cIMT, which was associated with time on dialysis of?>2?years, hypercalcemia, higher daily dose of calcitriol and HD (vs. PD). In the multivariate analysis, accounting for time on dialysis, HD persisted as a risk for increased cIMT.

Conclusions

The prevalence of increased cIMT in children on dialysis is similar to that reported in adults with CKD and increased with time on dialysis. HD was associated with increased cIMT, independently of time on dialysis; however, the results should be interpreted with caution due to the possible impact of confounding factors. These results underline the need to monitor and, if possible, prevent and treat increased cIMT in children on dialysis.     

Angiotensin II receptor blockers in pregnancy: a case report and systematic review of the literature.

OBJECTIVE: To describe the case of a woman exposed to angiotensin-II receptor blockers (ARBs) in the preconceptional period and to systematically review the literature on the safety of these drugs when used by pregnant women. METHODS: The case was identified at the Korean Motherisk Program (Seoul). For the systematic review, we searched the PubMed for case reports, case series, and post-marketing surveys. RESULTS: A hypertensive woman was exposed to irbesartan prior to conception. The embryo had delayed development of upper and lower extremities and decreased digital groove. A karyotype identified a 45,XO Turner syndrome. The patient had a spontaneous abortion. Including the case reported here, 64 published cases were identified in total; 57.8% had favorable and 42.2% had unfavorable outcomes. Duration of treatment during pregnancy among women who had adverse fetal outcomes was 26.3 +/- 10.5 weeks (mean +/- SD), compared with 17.3 +/- 11.6 weeks in those who had favorable outcomes (p = 0.04). CONCLUSIONS: Exposure to ARBs for a period longer than the first trimester of pregnancy appears to be associated with a high risk for adverse fetal outcomes.     

Icodextrin metabolism and alpha-amylase activity in nonuremic rats undergoing chronic peritoneal dialysis.

OBJECTIVE: To study the metabolism of icodextrin and alpha-amylase activity following daily exposure to dialysis solutions containing either glucose or icodextrin as osmotic agent in rats. METHODS: Male Wistar rats with implanted peritoneal catheters were infused twice daily for 3 weeks with 20 mL 7.5% icodextrin-based peritoneal dialysis fluid (IPDF; ICO group, n = 12) or 3.86% glucose-based peritoneal dialysis fluid (GLU group, n = 11). A 4-hour dwell study using 30 mL IPDF was performed on day 10 (D1) and day 21 (D2) in both the ICO and the GLU groups. Radiolabeled serum albumin (RISA) was used as a macromolecular volume marker. Dialysate samples were collected at 3, 15, 30, 60, 90, 120, and 240 minutes. Blood samples were drawn before the start and at the end of the dwell. RESULTS: During all dwell studies, the dialysate concentrations of total icodextrin decreased due to decrease in high molecular weight (MW) fractions, whereas there was a marked increase in icodextrin low MW metabolites. alpha-Amylase activity increased in dialysate and decreased in plasma. About 60% of the total icodextrin was absorbed from the peritoneal cavity during the 4-hour dwells. Low MW icodextrin metabolites were present in the dialysate already at 3 minutes, and maltose (G2), maltotriose (G3), maltotetraose (G4), and maltopentaose (G5) increased progressively, reaching maximum concentrations at 60 minutes. Maltohexaose (G6) and maltoheptaose (G7) were also detected already at 3 minutes but did not change significantly during the dwells. During the two 4-hour dwell studies (D1 and D2), the concentrations of total icodextrin and icodextrin metabolites and alpha-amylase activity in dialysate did not differ between the ICO and GLU groups, during either D1 or D2. No icodextrin metabolites were detected in plasma at the end of the dwells. alpha-Amylase activity in the dialysate increased six- to eightfold whereas plasma alpha-amylase activity decreased by 21% - 26% during the two 4-hour dwells in both the ICO and the GLU groups; there were no significant differences between the ICO and the GLU groups during either D1 or D2. alpha-Amylase activity in the dialysate correlated strongly with the disappearance rate of icodextrin from the peritoneal cavity during the 4-hour dwells, and with the concentrations of G2, G3, G6, and G7 in dialysate. CONCLUSIONS: The decline in the dialysate concentrations of high MW fractions and the increase in low MW metabolites of icodextrin suggest intraperitoneal alpha-amylase mediated the metabolism of icodextrin and the transport of predominantly the smaller icodextrin metabolites from dialysate. However, no icodextrin could be detected in plasma, suggesting that it was metabolized and excreted by the kidney in these nonuremic rats. In contrast to uremic peritoneal dialysis patients, chronic exposure to IPDF did not seem to further affect alpha-amylase activity or icodextrin metabolism. The much higher alpha-amylase activity in plasma and dialysate in rats than in humans explains the much more rapid metabolism of icodextrin in rats compared with peritoneal dialysis patients.     

Rate of synthetic oligosaccharide degradation as a novel measure of amylase activity in peritoneal dialysis patients.

BACKGROUND: Plasma alpha-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. METHODS: Plasma 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 degrees C for 4 hours. RESULTS: The 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. CONCLUSIONS: An 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.