Kinetics of peritoneal protein loss during CAPD: II. Lipoprotein leakage and its impact on plasma lipid levels

Intra-Abdominal Lipopolysaccharide Clearance and Inactivation in Peritonitis: Key Roles for Lipoproteins and the Phospholipid Transfer Protein

Introduction

During peritonitis, lipopolysaccharides (LPS) cross the peritoneum and pass through the liver before reaching the central compartment. The aim of the present study was to investigate the role of lipoproteins and phospholipid transfer protein (PLTP) in the early stages of LPS detoxification.

Material and Methods

Peritonitis was induced by intra-peritoneal injection of LPS in mice. We analyzed peritoneal fluid, portal and central blood. Lipoprotein fractions were obtained by ultracentrifugation and fast protein liquid chromatography. LPS concentration and activity were measured by liquid chromatography coupled with mass spectrometry and limulus amoebocyte lysate. Wild-type mice were compared to mice knocked out for PLTP.

Results

In mice expressing PLTP, LPS was able to bind to HDL in the peritoneal compartment, and this was maintained in plasma from portal and central blood. A hepatic first-pass effect of HDL-bound LPS was observed in wild-type mice. LPS binding to HDL resulted in an early arrival of inactive LPS in the central blood of wild-type mice.

Conclusion

PLTP promotes LPS peritoneal clearance and neutralization in a model of peritonitis. This mechanism involves the early binding of LPS to lipoproteins inside the peritoneal cavity, which promotes LPS translocation through the peritoneum and its uptake by the liver.

Residual Renal Function Affects Lipid Profile in Patients Undergoing Continuous Ambulatory Peritoneal Dialysis

Objective

To determine whether lipoprotein abnormalities associated with continuous ambulatory peritoneal dialysis (CAPD) are influenced by residual renal function (RRF).

Design

Open, non randomized prospective and com -parative study.

Setting

Single university teaching hospital dialysis unit and outpatient clinic.

Patients

Twenty adult patients on standard CAPD (1 -38 months) were divided into two groups: group A (RRF ≤ 0.8 mL/min, n = 10) and group B (RRF ≥ 1.1 mL/ min, n = 10). Patients in the two groups were matched for age, time on dialysis, body weight, body mass index, serum urea and albumin levels, peritoneal and urinary albumin losses, and peritoneal transport characteristics such as overnight 8hour peritoneal creatinine and β2-microglobulin clearances and overnight 8-hour effluent glucose concentrations.

Results

The degree of uremia in patients with preserved RRF (group B) was obviously lower than in patients with negligible RRF (group A), that is, patients in group B had significantly lower serum creatinine and β2-microglobulin levels and significantly higher weekly KTN than group A patients. Despite the prevalence of allele 4 of apolipoprotein E genotype in group A patients, their levels of serum total cholesterol, low-density lipoprotein cholesterol, lipoprotein (a) [Lp(a)], apolipoprotein B (ApoB), and apolipoprotein A1 (ApoA1) were significantly lower than those of patients with preserved RRF (group B). The two groups did not differ significantly in the serum levels of triglyceride or high-density lipoprotein cholesterol. Serum concentrations of Lp(a) and ApoA1, as well as ratios of ApoA1 to ApoB, were correlated significantly with RRF (r = 0.63, r = 0.51, and r = 0.61, respectively).

Conclusions

The findings suggest that RRF affects the lipid profile of CAPD patients, especially serum levels of cholesterol-rich lipoproteins.

The Effect of Insulin Delivery Route on Lipoproteins in Type I Diabetic Patients on CAPD

Objective

To evaluate the influence of subcutaneous and intraperitoneal (IP) insulin on plasma lipoproteins in type I diabetic (IDDM) patients with end-stage renal failure (ESRD) treated with continuous ambulatory peritoneal dialysis (CAPD).

Design

A before–after trial.

Setting

University hospital outpatient care.

Participants

Eleven IDDM patients with stabilized peritoneal dialysis, age 42.9 ± 2.9 (SEM) years and duration of diabetes 31.4 ± 3.4 years.

Intervention

Two treatment periods during stabilized CAPD. All patients were first treated with subcutaneous and then with IP insulin. The studies were performed after a median time of 3 months on each treatment.

Main Outcome Measures

Plasma lipids; apoproteins (Apo) A-I, A-II, and B; high-density lipoprotein (HDL) subfractions; glycemic status; and uremic status.

Results

After changing from subcutaneous insulin to IP insulin, plasma HDL cholesterol decreased (from 1.29 ± 0.13 mmol/L to 0.96 ± 0.06 mmol/L, p < 0.05), and the low density to high density lipoprotein (LDL/HDL) cholesterol ratio increased ( p < 0.05). The HDL cholesterol decreased in both HDL2 and HDL3 fractions, but significantly so only in HDL3 ( p < 0.01). ApoA-I ( p < 0.05) decreased while the ApoB/ApoA-I ratio ( p < 0.01) and the ApoA-I/HDL-cholesterol ratio ( p < 0.01) increased during IP insulin therapy. Intraperitoneal insulin resulted in significantly better glycemic control than subcutaneous insulin ( p < 0.01).

Conclusions

In diabetic patients on CAPD therapy, IP insulin, although inducing better glycemic control than subcutaneous insulin, was associated with lowered plasma HDL cholesterol and ApoA-I levels. The atherogenic potential is probably less than expected as the relative particle size of HDL remained unchanged.

Cardiovascular Disease and Risk Factors in Patients Treated by Continuous Ambulatory Peritoneal Dialysis

The opinions and assertions contained herein are private and are not to be construed as official or representing those of the Uniformed Services University of the Health Sciences or the Department of Defense, U.S.A.

Dyslipidemia in Peritoneal Dialysis — Relation to Dialytic Variables

Objective

To investigate whether the specific lipoprotein (LP) abnormalities of peritoneal dialysis (PD) are associated with functional variables of this mode of dialysis.

Design

A survey of the LP profile in relation to peritoneal dialysis capacity (PDC) variables. The LP profile was compared to that of a group of age- and sex-matched controls.

Setting

The Peritoneal Dialysis Unit at Sahlgrenska University Hospital in Gothenburg, Sweden.

Patients

Twenty-two nondiabetic PD patients (5 women, 17 men) who had been on PD for at least 6 months.

Main Outcome Measures

The LP profile included plasma lipids, apolipoproteins (Apo), and individual ApoA- and ApoB-containing LP. The PDC measurement determined peritoneal glucose uptake, protein losses, effective peritoneal surface area, and total weekly creatinine clearance.

Results

The patients had been on PD for 6 to 48 months (mean 15.3 months) and had a total weekly creatinine clearance of 69.7 ± 13.3 L/1.73m2body surface area, an average peritoneal glucose uptake corresponding to 446 ± 162 kcal/24 hour, and a protein loss of 8.1 ± 2.5 g/24 hr. The patients had significantly higher total cholesterol (7.1 mmol/L), VLDL-cholesterol (1.0 mmol/L), LDL-cholesterol (4.7 mmol/L), and triglyceride levels (2.5 mmol/L); whereas the HDL-cholesterol level (1.2 mmol/L) was significantly lower than in controls. The PD patients had increased levels of ApoB-containing LPs, both of the cholesterol-rich LP-B and of the triglyceride-rich LP-B complex, reflected in higher plasma concentrations of ApoB, ApoC-III, and ApoE. Furthermore, they had significantly lower levels of LP-A-I:A-II, as well as of ApoA-I and ApoA-II. The LP-A-I:A-II and ApoA-II levels correlated inversely with the duration of PD treatment ( r = 0.54, p < 0.01 and r = 0.52, p < 0.05, respectively). The ApoA-II level was inversely correlated with the peritoneal surface area ( r = 0.53, p < 0.05). There were no other correlations between LP variables and PDC variables, nor did any of the LP variables correlate with peritoneal glucose uptake or protein losses.

Conclusion

The proatherogenic lipoprotein profile of patients on PD is characterized by increased concentrations of cholesterol-rich and triglyceride-rich ApoB-containing LPs. While the duration of treatment appears to have some influence on the development of this type of dyslipidemia, the pathophysiological links to the dialysis mode must be further explored.

Lipid Parameters Including Lipoprotein (A) in Patients Undergoing CAPD and Hemodialysis

Objective

Oyslipidemia possibly contributes to the vascular complications commonly afflicting uremic patients. Lipoprotein (a) [Lp(a)] has been identified as an independent risk factor for atherosclerotic vascular dis ease. The aim of our study was to compare lipidparameters, including Lp(a), between hemodialysis (HO) and continuous ambulatory peritoneal dialysis (CAPO) patients.

Design

A cross-sectional study.

Setting

University Medical Center.

Participants

Forty CAPO and 40 HO patients carefully matched for age, sex, body mass index (BMI), smoking habits, and duration of dialysis were studied. A group of 40 healthy individuals matched for age, sex, BMI, and smoking habits was used as control.

Interventions

None.

Main Outcome Measures

Serum lipid parameters and atherogenic risk ratios were the main outcome measures.

Results

Both groups of dialysis patients had increased serum triglycerides and decreased levels of Apo AI and HOL cholesterol compared to controls. Moreover, the risk ratios total cholesterol/HOL cholesterol and LOL cholesterol/HOL cholesterol were significantly higher, and the ratio ApoA1/ApoB was significantly lower in both groups of patients in comparison to the normal subjects. Both groups of dialysis patients exhibited decreased ratios of LOL cholesterol/ApoB and HOL cholesterol/ApoAI, suggesting the presence of compositional lipoprotein changes. CAPO patients had a more atherogenic lipid profile compared to HO patients, since they exhibited higher levels of total and LOL cholesterol, of ApoB as well as of the ratios total cholesterol/HOL cholesterol and LOL cholesterol/ HOL cholesterol, and lower levels of the ratio ApoA1/ApoB compared to HO patients. Both groups of dialysis patients had increased serum Lp(a) levels. Even though CAPO patients had higher serum Lp(a) levels than HO patients, the differences between these two groups were only marginally statistically significant (p = 0.056 by Mann-Whitney U-test). Uremic dyslipidemia was positively correlated with serum albumin levels in both groups of patients.

Conclusion

CAPO patients exhibit a more atherogenic lipid profile than that of HO patients. The marked disturbances in Lp(a) levels may further increase the vascular risk in both groups of patients.

Intraperitoneal Insulin Reduces Plasma Leptin Concentration in Diabetic Patients on CAPD

Objective

To determine the effects of subcutaneous (SC) and intraperitoneal (IP) insulin on serum leptin concentration in type I diabetic patients with end-stage renal failure treated with continuous ambulatory peritoneal dialysis (CAPD).

Design

Prospective, open, before–after study.

Setting

Tertiary-care university hospital.

Participants

Twelve type I diabetic patients with stabilized CAPD, age 43.9 ± 2.8 years, and duration of diabetes 30.4 ± 3.5 years.

Intervention

After stabilized CAPD therapy, all patients were treated first with SC insulin for a median of 3 months, and thereafter with IP insulin for another 3 months.

Main Outcome Measures

Plasma leptin, insulin sensitivity with euglycemic clamp, and glycemic and uremic status after both treatment periods.

Results

During SC insulin therapy, plasma leptin concentration was significantly higher than during IP insulin (19.8 ± 5.9 ng/mL and 12.8 ± 6.2 ng/mL, respectively; p < 0.001). Leptin concentration was higher in CAPD patients and was related to body mass index in both genders. No correlation was detected between plasma leptin and fasting insulin, glycemic control, glucose disposal rate, or serum lipids.

Conclusion

Plasma leptin concentration is lower during IP insulin therapy compared to SC insulin. Insulin has probably a direct effect on both peritoneal leptin clearance and adipose tissue leptin production. The significance of leptin in regulating appetite and anorexia in uremia remains unclear.

Lipoprotein (a) Levels in Patients Undergoing Continuous Ambulatory Peritoneal Dialysis

Most researchers have found increases of lipoprotein (a) [Lp(a)] in uremic patients, as well as in those undergo ng hemodialysis (HD) or continuous ambulatory peritoneal dialysis (CAPD). The mechanisms for this increase remain unclear. We studied 71 patients undergoing CAPD, 48 me n and 23 women. According to the time spent on CAPD, the patients were divided into three groups: group 0: 29 patients at the starting off point of dialysis treatment; group I: 22 patients with an average stay of 15.2 months; group II: 20 patients with an average stay of 69.3 months on CAPD. We have only observed significant increases of Lp(a) levels in those patients initiating the dialysis, but no significant differences are found in the other groups undergoing CAPD for longer periods when compared to the control group. We found no significant relation between Lp(a) levels and peritoneal protein loss, and not with absorption of glucose from the dialysate either. We have found a positive and significant correlation between Lp(a) levels and urinary protein loss (r = 0.41; p < 0.001). It is possible that an element associated with proteinuria might have an effect on the metabolism of Lp(a) in CAPD patients.

Statins for Treatment of Dyslipidemia in Chronic Kidney Disease

Dyslipidemia is a potent cardiovascular (CV) risk factor in the general population. Elevated low-density lipoprotein cholesterol (LDL-C) and/or low high-density lipoprotein (HDL-C) are well-established CV risk factors, but more precise determinants of risk include increased apoprotein B (ApoB), lipoprotein(a) [Lp(a)], intermediate and very low-density lipoprotein (IDL-C, VLDL-C; “remnant particles”), and small dense LDL particles. Lipoprotein metabolism is altered in association with declining glomerular filtration rate such that patients with non dialysis-dependent chronic kidney disease (CKD) have lower levels of HDL-C, higher triglyceride, ApoB, remnant IDL-C, remnant VLDL-C, and Lp(a), and a greater proportion of oxidized LDL-C. Similar abnormalities are prevalent in hemodialysis (HD) patients, who often manifest proatherogenic changes in LDL-C in the absence of increased levels. Patients treated with peritoneal dialysis (PD) have a similar but more severe dyslipidemia compared to HD patients due to stimulation of hepatic lipoprotein synthesis by glucose absorption from dialysate, increased insulin levels, and selective protein loss in the dialysate analogous to the nephrotic syndrome. In the dialysis-dependent CKD population, total cholesterol is directly associated with increased mortality after controlling for the presence of malnutrition–inflammation.

Treatment with statins reduces CV mortality in the general population by approximately one third, irrespective of baseline LDL-C or prior CV events. Statins have similar, if not greater, efficacy in altering the lipid profile in patients with dialysis-dependent CKD (HD and PD) compared to those with normal renal function, and are well tolerated in CKD patients at moderate doses (≤ 20 mg/day atorvastatin or simvastatin). Statins reduce C-reactive protein as well as lipid moieties such as ApoB, remnants IDL and VLDL-C, and oxidized and small dense LDL-C fraction. Large observational studies demonstrate that statin treatment is independently associated with a 30% – 50% mortality reduction in patients with dialysis-dependent CKD (similar between HD- and PD-treated patients). One recent randomized controlled trial evaluated the ability of statin treatment to reduce mortality in type II diabetics treated with HD (“4D”); the primary end point of death from cardiac cause, myocardial infarction, and stroke was not significantly reduced. However, results of this trial may not apply to other end-stage renal disease populations. Two ongoing randomized controlled trials (SHARP and AURORA) are underway evaluating the effect of statins on CV events and death in patients with CKD (including patients treated with HD and PD). Recruitment to future trials should be given a high priority by nephrologists and, until more data are available, consideration should be given to following published guidelines for the treatment of dyslipidemia in CKD. Additional consideration could be given to treating all dialysis patients felt to be at risk of CV disease (irrespective of cholesterol level), given the safety and potential efficacy of statins. This is especially relevant in patients treated with PD, given their more atherogenic lipid profile and the lack of randomized controlled trials in this population.

Elevated Plasma Lipoprotein(a) Levels and Hypoalbuminemia in Peritoneal Dialysis Patients

Plasma lipoprotein(a), Lp(a), is strongly and independently associated with atherosclerosis, and levels are elevated in hemodialysis (HD) patients and in some studies of those on peritoneal dialysis (PD). We hypothesized that protein losses and hypoalbuminemia could stimulate hepatic Lp(a) synthesis, and this effect would be accentuated in PD patients with malnutrition. The PD subjects (n=24) had higher plasma Lp(a) levels than those (n=10) on HD (median 34.4 vs 21.0 mg/dl, p<0.05), and values exceed normal in 62.5% vs 20% of the subjects (p<0.03), respectively. The serum albumin levels inversely correlated with concentrations of Lp(a) and apolipoprotein B, as well as the apolipoprotein B/AI ratio. In conclusion, plasma Lp(a) concentrations are frequently elevated in PD as well as HD patients. Measuring Lp(a) levels is useful in identifying patients at increased atherogenic risk, which may not be reflected in routine lipid profiles. The negative correlation between plasma Lp(a) and albumin levels suggests that the latter may be linked pathophysiologically to hepatic Lp(a) production. The association of hypoalbuminemia with higher Lp(a) values is of particular concern because malnutrition frequently occurs in PD patients.

Higher serum triglyceride to high-density lipoprotein cholesterol ratio was associated with increased cardiovascular mortality in female patients on peritoneal dialysis

BACKGROUND AND AIMS

High serum triglyceride to high-density lipoprotein cholesterol (TG/HDL-C) ratio has been found to be an independent predictor for cardiovascular events in the general population. We aimed to evaluate whether a high TG/HDL-C ratio was associated with an increased risk of mortality in patients on continuous ambulatory peritoneal dialysis (CAPD).

METHODS AND RESULTS

In this single-center retrospective cohort study, 1170 incident patients on peritoneal dialysis (PD) from 1 January 2007 to 31 December 2011 were recruited and followed up until 31 December 31 2013. The mean age was 47.4 ± 15.2 years, and 24.7% were diabetic. During a median of the 34.5-month follow-up period, 213 (18.2%) deaths occurred, 121 of which (56.8%) were caused by cardiovascular disease (CVD). The serum median TG/HDL-C ratio at baseline was 2.57 (range: 0.06-39.39). On multivariate Cox regression analysis, the highest quartile of the TG/HDL-C ratio (≥4.19) was associated with increased risk of all-cause mortality (hazard ratio (HR) 1.98, 95% confidence interval (CI), 1.17-3.36; P = 0.011) and CVD mortality (HR 2.28, 95% CI, 1.16-4.47; P = 0.017). For female patients, each one-unit higher baseline TG/HDL-C was associated with 13% (95% CI 1.06-1.22; P = 0.001) increased risk of CVD mortality, whereas such an association was not observed for male patients, (HR 1.00, 95% CI 0.92-1.08; P = 0.977).

CONCLUSIONS

A higher serum TG/HDL-C ratio was associated with an increased risk of all-cause and CVD mortality in PD patients. Moreover, the increased risk of CVD mortality was significantly higher in female than male PD patients.

Dyslipidemia in patients with chronic and end-stage kidney disease

In this review, we discuss the physiology, diagnosis and treatment of dyslipidemia in patients with chronic and end-stage renal disease. The recent important clinical trials in patients with chronic kidney disease and dyslipidemia are reviewed. Because of the lack of evidence in treating lipid abnormalities in this specific patient population, we propose that future studies should focus on the pathophysiological mechanisms and treatment of dyslipidemia in this special patient population.

Dyslipidemia associated with chronic kidney disease

Cardiovascular disease is a major cause of morbidity and mortality in patients with impaired renal function. Dyslipidemia has been established as a well-known traditional risk factor for cardiovascular disease (CVD) in the general population and it is well known that patients with chronic kidney disease (CKD) exhibit significant alterations in lipoprotein metabolism. In this review, the pathogenesis and treatment of CKD-induced dyslipidemia are discussed. Studies on lipid abnormalities in predialysis, hemodialysis and peritoneal dialysis patients are analyzed. In addition, the results of the studies that tested the effects of the hypolipidemic drugs on cardiovascular morbidity and mortality in patients with CKD are reported.

Effect of Dialysis Type on Serum Lipids, Apolipoproteins, and Lipoproteins

AIM

Dyslipidemia is common among patients with end-stage renal disease, whether treated by hemodialysis (HD) or peritoneal dialysis (PD). However, there are not enough data about the effect of dialysis type on serum lipoprotein (a) [Lp(a)], apolipoprotein (a) [Apo(a)], apolipoprotein (b) [Apo(b)], and lipid levels. The aim of this study was to determine the effect of dialysis type on serum lipid levels.

MATERIALS AND METHODS

This study enrolled 40 HD patients (20 men and 20 women, aged 48.1 +/- 17.6 years) and 69 PD patients (35 men and 34 women, aged 45.2 +/- 16.3 years). Serum lipid profile including total cholesterol (TC), low-density lipoprotein (LDL-C), high-density lipoprotein (HDL-C), triglyceride (TG), Apo(a), Apo(b), and Lp(a) were determined in HD and PD patients. Patients who have used statins within the last six months were not included in the study.

RESULTS

No significant differences in TC, LDL-C, HDL-C, TG, Apo(a), Apo(b), or Lp(a) serum levels were found between HD and PD patients. Serum TC, LDL-C, HDL-C, TG, Apo(a), Apo(b), and Lp(a) in HD and PD patients were 172.2 +/- 42.7 (mg/dL) vs. 181.0 +/- 53.0 (mg/dL), 97.2 +/- 36.2 (mg/dL) vs. 101.4 +/- 33.6 (mg/dL), 45.3 +/- 11.9 (mg/dL) vs. 41.4 +/- 11.1 (mg/dL), 144.7 +/- 71.8 (mg/dL) vs. 173.0 +/- 76.8 (mg/dL), 1.2 +/- 0.5 (g/L) vs. 1.0 +/- 0.2 (g/L), 0.9 +/- 0.3 (g/L) vs. 1.2 +/- 0.3 (g/L), and 43.1 +/- 40.6 (mg/dL) vs. 46.0 +/- 42.7 (mg/dL), respectively.

CONCLUSION

The results of this study show that the maintenance CAPD treatment is associated with more pronounced alterations of the lipoproteins and lipid metabolism than those observed during HD treatment.

The Variability in Ultrafiltration Achieved with Icodextrin, Possibly Explained

Background

A recent study by Jeloka et al. (Perit Dial Int 2006; 26:336–40) highlighted the high variability in maximum ultrafiltered volume (UFmax) and the corresponding dwell time (tmax) obtained using 7.5% icodextrin solution. We aimed to pinpoint the possible sources of this phenomenon by simulating the icodextrin ultrafiltration (UF) profiles according to the three-pore model of peritoneal transport.

Method

The individual UF time courses observed in the study by Jeloka et al. ( n = 29) were first characterized by linear and quadratic regression. We were then able to identify four main patterns. These were then adapted to UF profiles generated by the three-pore model by systematically altering the values of some model parameters, namely, the mass transfer area coefficient (MTAC or PS) for icodextrin/glucose, the peritoneal UF coefficient (LpS), the plasma colloid osmotic pressure gradient (ΔΠ), and the macromolecular clearance out of the peritoneal cavity (ClLF).

Results

Modifications in the PS values caused only marginal variations in UFmax and tmax, while more significant changes were produced by altering LpS and ClLF. However, far more evident was the importance of changes in ΔΠ In fact, lowering ΔΠ to 14 mmHg caused a steady increase in UF with 10 – 14 hour dwells. On the contrary, the UF profiles became nearly “flat” when ΔΠ was increased to 30 mmHg. The parallel shifts induced by altering icodextrin metabolite concentrations did not markedly influence UFmax or tmax.

Conclusion

The UF pattern in icodextrin dwells seem to be mainly determined by the plasma colloid osmotic pressure, while only moderate changes can be seen with alterations in LpS and ClLF. The result is not completely unexpected considering that icodextrin acts by inducing a strong colloid osmotic gradient. A number of clinical studies would be needed, however, in order to prove this hypothesis.

Rapid Solute Transport in the Peritoneum: Physiologic and Clinical Consequences

This review focuses on the physiologic and clinical consequences of rapid solute transport in the peritoneum. The concept, the current understanding of related factors, and the possible causes implicated in rapid solute transport are discussed first. Then, the consequences, with particular emphasis on mortality, are highlighted. Finally, based on recent advances and clinical studies, some strategies for the treatment of fast peritoneal transport are reviewed.

Endocrinology and Dialysis Jean L. HolleySeries Editor: Lipid Abnormalities Associated with End-Stage Renal Disease

Patients undergoing chronic renal replacement therapy have a high incidence of dyslipidemia. In general, there are increased concentrations of triglyceride-rich apolipoprotein B-containing particles. These elevations lead to increased levels of non-high-density lipoprotein (HDL) levels. This pattern is further modified by the method of dialysis (peritoneal versus hemodialysis) and comorbidities such as diabetes. End-stage renal disease patients also demonstrate increased levels of lipoprotein(a) (Lp(a)) and oxidized low-density lipoprotein (LDL)both of which are highly atherogenic. This review focuses on the pathogenesis of these lipid abnormalities and their role in the atherosclerotic process.

Dialysis modalities and dyslipidemia

Progressive renal failure is accompanied by dyslipidemia, which is reflected in an abnormal apolipoprotein profile. It is characterized by increased concentrations of intact and partially metabolized triglyceride-rich apoB-containing lipoproteins. They occur preferentially in very-low density lipoprotein (VLDL) and low-density lipoprotein (LDL) as a result of impaired metabolism and clearance. Hemodialysis can moderately attenuate the renal dyslipidemia. In contrast, peritoneal dialysis is associated with further aggravation, including an increase of cholesterol-rich apoB-containing lipoproteins.

Serum prealbumin is higher in peritoneal dialysis than in hemodialysis: a meta-analysis

BACKGROUND

Although not widely appreciated, the reported concentration of serum prealbumin, like that of serum cholesterol, tends to be higher in patients on peritoneal dialysis (PD) than on hemodialysis (HD), despite the substantial loss of protein during PD.

METHODS

The mean difference in serum prealbumin was quantified by meta-analysis of the mean differences found in six cohorts with both PD and HD patients (set 1; N = 639) using a fixed-effects model, and meta-analysis of the mean prealbumin values reported in 23 cohorts of unselected dialysis patients on a single modality (set 2; 9 PD cohorts, 14 HD cohorts; N = 12,256) using a mixed model. For comparison, the mean difference in serum albumin concentration between PD and HD also was estimated in sets 1 and 2 using the same methods.

RESULTS

In set 1, the mean prealbumin difference (PD-HD) in the individual cohorts ranged from 3.6 to 14.7 mg/dL (P < 0.05 in five cohorts), and the weighted mean difference was 5.4 mg/dL (95% CI, 3.8 to 7.0 mg/dL). In set 2, weighted mean prealbumin was 8.1 mg/dL (95% CI, 5.2 to 10.9 mg/dL) higher in PD than in HD in the entire data set, and 6.9 mg/dL (95% CI, 5.2 to 8.6 mg/dL) higher in a sensitivity analysis that excluded two outlying HD studies. By contrast, weighted mean serum albumin concentration was significantly lower in PD than in HD in both sets 1 and 2; the mean difference was 0.25 g/dL (95% CI, 0.14 to 0.36 g/dL) in set 1 and 0.28 g/dL (95% CI, 0.14 to 0.42 g/dL) in set 2.

CONCLUSIONS

Serum prealbumin level is approximately 6 mg/dL higher in PD than HD, perhaps due to the stimulation of hepatic synthesis by PD albumin loss, while serum albumin is approximately 0.3 g/dL lower in PD. Different reference ranges and clinical targets (such as, K/DOQI guidelines) are needed for PD and for HD.

Pathogenic effects of a high peritoneal transport rate

Recent studies have shown that patients with high peritoneal transport characteristics have substantially increased morbidity and mortality. This finding is counter-intuitive, since HTs will a priori achieve higher clearances. There are many possible causes: increased protein losses with consequent hypoalbuminemia; poor ultrafiltration capacity causing fluid retention, ventricular hypertrophy and hypertension; increased glucose absorption leading to anorexia, hyperinsulinism, and local AGE formation; and the development of an atherogenic lipid profile. While common pathogenic causes of high peritoneal transport and atherosclerosis have been hypothesized, it is more likely that CAPD as currently practiced is unsuitable for HTs, who should be switched to HD or NIPD. Renal and peritoneal clearances have different clinical effects and should be assessed separately. Current measures of dialysis adequacy, such as total Kt/V, do not therefore describe the patient's clinical situation accurately and are insufficient.

Lipoprotein(a) plasma concentrations after renal transplantation: a prospective evaluation after 4 years of follow-up

The highly atherogenic lipoprotein(a) [Lp(a)] is significantly elevated in patients with renal disease. It is discussed controversially whether Lp(a) concentrations decrease after renal transplantation and whether the mode of immunosuppressive therapy influences the Lp(a) concentrations. In a prospective study the Lp(a) concentrations before and on average 48 months after renal transplantation were measured in 145 patients. The determinants of the relative changes of Lp(a) concentrations were investigated in a multivariate analysis. Patients treated by CAPD showed a larger decrease of Lp(a) than hemodialysis patients, reflecting their markedly higher Lp(a) levels before transplantation. The relative decrease of Lp(a) was higher with increasing Lp(a) concentrations before transplantation in combination with an increasing molecular weight of apolipoprotein(a) [apo(a)]. That means that the relative decrease of Lp(a) is related to the Lp(a) concentration and the apo(a) size polymorphism. With increasing proteinuria and decreasing glomerular filtration rate, the relative decrease of Lp(a) became less pronounced. Neither prednisolone nor cyclosporine (CsA) had a significant impact on the Lp(a) concentration changes. Azathioprine (Aza) was the only immunosuppressive drug which had a dose-dependent influence on the relative decrease of Lp(a) levels. These data clearly demonstrate a decrease of Lp(a) following renal transplantation which is caused by the restoration of kidney function. The relative decrease is influenced by Aza but not by CsA or prednisolone.

Apolipoprotein B-containing lipoproteins in renal failure: the relation to mode of dialysis

BACKGROUND

The aim of this study was to establish whether there is a differential effect of mode of dialysis, hemodialysis (HD), or continuous ambulatory peritoneal dialysis (CAPD) on the dyslipidemia of renal failure.

METHODS

The lipoprotein profile was determined in 61 non-diabetic patients on chronic HD (N = 30) and CAPD treatment (N = 31), and in a control group of 27 healthy subjects. The analysis included the measurement of individual apolipoprotein (apo) A- and apo B-containing lipoproteins (LPs) separated by sequential immunoaffinity chromatography. Apo A-containing lipoproteins include lipoprotein A-I with apo A-I and lipoprotein A-I:A-II with apo A-I and apo A-II as the main protein constituents, whereas apo B-containing lipoproteins comprise simple cholesterol-rich lipoprotein B (LP-B), with apo B as the only protein moiety and complex triglyceride (TG)-rich lipoprotein B complex (LP-Bc) particles with apo B, apo A-II, apo C, and/or apo E as the protein constituents.

RESULTS

CAPD patients had significantly higher concentrations of total cholesterol (6.8 vs. 5.1 mmol/liter), low-density lipoprotein (LDL) cholesterol (4.6 vs. 3.2 mmol/liter), TG (2.3 vs. 1.5 mmol/liter), apo B (155.3 vs. 105.7 mg/dl), LP-B (136.0 vs. 91.9 mg/dl), and LP-Bc (19.3 vs. 13.8 mg/dl) than HD patients. Both HD and CAPD patients had significantly higher TG, VLDL cholesterol, apo C-III, and apo E and significantly lower high-density lipoprotein cholesterol, apo A-II, and lipoprotein A-I:A-II levels than control subjects. The distribution of apo C-III in high-density lipoprotein and VLDL-LDL was altered in CAPD patients in comparison with control subjects. This suggests that the removal of TG-rich lipoproteins is less efficient in patients on CAPD. Normotriglyceridemic (NTG; TG < or = 1.7 mmol/liter, 150 mg/dl) CAPD patients had significantly higher levels of TC, LDL cholesterol, apo B, and LP-B than NTG-HD patients. There was little difference in the LP-Bc levels between NTG-CAPD, NTG-HD, and controls. Similarly, hypertriglyceridemic (HTG) CAPD patients had significantly higher TC, LDL cholesterol, apo B, and LP-B levels than HTG-HD patients. The LP-Bc levels were significantly increased in HTG-HD and HTG-CAPD patients compared with controls, but the slightly higher levels in the CAPD patients did not differ significantly from the HD group.

CONCLUSION

CAPD and HD patients have a lipoprotein profile characteristic of renal failure. Patients on long-term CAPD have higher levels of cholesterol-rich apo B-containing lipoproteins unrelated to TG levels. Many patients on CAPD also have a substantial elevation of the plasma concentrations of TG-rich LPs. The clinical significance of increased levels of potentially atherogenic LP-B during CAPD remains to be investigated.

Lipid transfer inhibitor protein activity deficiency in normolipidemic uremic patients on continuous ambulatory peritoneal dialysis

We previously demonstrated that lipid transfer inhibitor protein (LTIP) is a potent modifier of lipid transfer protein (LTP) function in vitro. Based on these studies, we proposed that LTIP activity is an important determinant of lipoprotein size and composition, which leads to a stimulation of reverse cholesterol transport. To further evaluate this hypothesis, we have studied a normolipidemic, uremic patient population undergoing continuous ambulatory peritoneal dialysis (CAPD) that is deficient in LTIP activity (< 18% of control). LDL from CAPD plasma was triglyceride enriched; the diameters of both CAPD LDL and HDL were increased and CAPD HDL was dominated by the largest subfraction, HDL2b. In CAPD patients, the plasma cholesterol esterification rate was only 61% of control; this decrease was due mainly to the poor reactivity of CAPD lipoproteins. CAPD lipoprotein-deficient plasma promoted twofold greater transfer of radiolabeled cholesteryl ester (CE) between standard lipoproteins than control, although LTP itself was increased only 39%. This twofold increase was not equally expressed among individual lipoprotein classes; CE transfers involving LDL were increased 2.4-fold, whereas those not involving LDL were increased only 50%. In whole plasma, CE net mass transfer to VLDL was slightly increased in CAPD plasma; relative to their CE content, control HDL contributed twofold more CE mass to VLDL than control LDL, but in CAPD plasma this preferential transfer of CE from HDL was absent. Collectively, the aberrations in CAPD lipoprotein composition and metabolism are consistent with the hypothesized role of LTIP. The data further support the role of LTIP in modulating the participation of HDL in CE mass transfers to VLDL. This is the first report of LTIP activity deficiency in humans.

The relationship between plasma and dialysate lipoproteins and apoproteins in patients treated by continuous ambulatory peritoneal dialysis

End-stage renal disease is frequently associated with lipoprotein abnormalities, manifested primarily by elevated very low-density lipoprotein levels combined with a decrease in high-density lipoprotein levels. These lipoprotein disturbances are further exacerbated in continuous ambulatory peritoneal dialysis. We examined the lipoprotein and apolipoprotein profiles in the blood and dialysate effluents of eight normolipidemic and five hypertriglyceridemic patients with end-stage renal failure treated with continuous ambulatory peritoneal dialysis. The normolipidemic patients were found to have significantly greater losses, as expressed by the fractional catabolic rates through the dialysate, for protein, total cholesterol, and very low-density lipoprotein cholesterol. These results suggest that the hypertriglyceridemia associated with continuous ambulatory peritoneal dialysis may be mitigated in some patients by the excessive loss of very low-density lipoprotein, or some other plasma constituent, into the dialysate effluent.

The uremic dyslipidemia: a cross-sectional and longitudinal study

Patients on maintenance hemodialysis (HD) and continuous ambulatory peritoneal dialysis (CAPD) exhibit numerous disturbances of serum lipids and apoproteins that may contribute to their high cardiovascular mortality. Cross-sectional studies have found that lipid levels are inversely related to time on dialysis. However, it is not known whether this association is the result of the attrition of hyperlipidemic patients or a decrease in lipid levels over time in all patients. Additionally, few studies have investigated the effect of dialysis modality on the lipoprotein disturbances of uremia adjusting for the confounding influences of demographics, or nutritional and endocrine status. To address these issues, we undertook a cross-sectional and longitudinal study of lipids, apoproteins, and atherogenic risk ratios in patients maintained on HD and CAPD. Patients were enrolled in annual cohorts from 1987 to 1990 and monitored until 1991. A total of 196 HD and 77 CAPD patients were studied. Total cholesterol (TC), high-density lipoprotein cholesterol (HDL-C), apoprotein (apo) A-I, and apo B were measured on enrollment and remeasured annually in survivors through 1990. Using multivariate methods, we examined the relationship of the lipids, apoproteins, their respective ratios, and their changes over time, to a broad range of clinical factors and to mortality. Compared with HD patients, CAPD patients had significantly higher TC, apo A-I, and apo B, and a significantly lower apo A-I/apo B ratio. Serum albumin correlated directly with TC and apo B and inversely with apo A-I/apo B. For patients with normal serum albumin (> or = 3.5 g/dL [35 g/L]), CAPD patients had a significantly higher TC/HDL-C than HD patients; otherwise the ratios were similar for CAPD and HD. Independent influences on lipoprotein levels in HD and CAPD patients were also demonstrated for race, gender, and diabetes, but not for parathyroid hormone (PTH) levels. For both dialysis modalities, patients who died had significantly lower TC and apo B, and significantly higher apo A-I/apo B throughout their entire courses compared with survivors. In the subset of patients followed longitudinally for 2 or more years, apo B tended to decrease with time, but TC, HDL-C, and apo A-I were stable. The longitudinal changes in lipoproteins did not correlate with outcome or other factors. In conclusion, CAPD patients have more atherogenic lipoprotein profiles than HD patients. Improved visceral protein nutritional status, as defined by serum albumin level, is associated with hyperlipidemia and, especially vor CAPD, worsened atherogenic risk ratios.(ABSTRACT TRUNCATED AT 400 WORDS)

Increased serum apolipoprotein(a) in patients with chronic renal failure treated with continuous ambulatory peritoneal dialysis

Patients with end-stage renal failure (ESRF) on renal replacement therapy are at significantly increased risk of cardiovascular disease. To determine whether altered concentrations of apolipoprotein(a) (apo(a)), the plasminogen-like protein moiety of the atherogenic particle lipoprotein(a), contributed to this increased risk, apo(a) concentrations were measured in 48 non-diabetic patients with ESRF treated by continuous ambulatory peritoneal dialysis (CAPD) therapy and compared with 65 controls. Apo(a) concentration was increased in CAPD patients compared to controls (geometric mean 419 units/l versus 137 units/l; ratio of means 3.06 (95% CI 1.95-4.80). We conclude that CAPD patients have increased apo(a) concentrations which may contribute to their increased risk of cardiovascular disease.