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 Table of Contents  
ORIGINAL ARTICLE
Year : 2013  |  Volume : 1  |  Issue : 2  |  Page : 82-87

Transport Characteristics of patients on automated peritoneal dialysis may not affect their lipid profile


1 Department of Internal Medicine, College of Medicine, University of Dammam, Saudi Arabia
2 Department of Pathology, College of Medicine, University of Dammam, Saudi Arabia
3 Department of Radiology, College of Medicine, University of Dammam, Saudi Arabia

Date of Web Publication25-Dec-2013

Correspondence Address:
Abdullah K Al-Hwiesh
Department of Internal Medicine, King Fahd Hospital of the University, P.O. Box 40246, Al-Khobar 31952
Saudi Arabia
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DOI: 10.4103/1658-631X.123652

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  Abstract 

Introduction: End-stage renal disease patients undergoing peritoneal dialysis usually have significant hyperlipidemia. The peritoneal membrane permeability and residual renal function (RRF) may affect lipid profile in these patients.
Objective: To study the correlation of lipid profile with peritoneal membrane transport characteristic and RRF as well as cancer antigen (CA)-125 in patients on automated peritoneal dialysis (APD).
Materials and Methods: The present study is a retrospective analysis of forty end-stage renal disease patients on APD. Lipid profile (total cholesterol, serum triglyceride, low-density lipoprotein and high-density lipoprotein), serum albumin and CA-125 were correlated with various peritoneal membrane transporters, assessed by peritoneal equilibration test (PET). Lipid profile was also correlated with residual renal function and KT/V.
Results: The study included 21 female and 19 male patients on APD. The duration of peritoneal dialysis was 18-70 months. There was no significant difference in lipid profile at baseline and at one year in patients with different peritoneal transporter status. There was no correlation between lipid profile and residual renal function as well as CA-125.
Conclusion: The findings suggest that there is no relation of lipid profile with peritoneal membrane transporter status and residual renal function in patients maintained on automated peritoneal dialysis.

  Abstract in Arabic 

تعنى هذه الدراسة الاسترجاعية بالعلاقة بين معدلات الدهنيات في الدم والغشاء الصفاقي لدى مرضى الفشل الكلوي الخاضعين للديلزة البريتونية. وضحت نتائج الدراسة عدم وجود علاقة إحصائية دالة بين معدلات الدهنيات في الدم والغشاء الصفاقي الناقل وكذلك وظائف الكلى عند مرضى الفشل الكلوي الخاضعين للديلزة الصفاقية التلقائية.


Keywords: Automated peritoneal dialysis, CA-125, hyperlipidemia, peritoneal equilibration test


How to cite this article:
Al-Hwiesh AK, Aloadh NA, Abdul-Rahman IS, Al-Dhafery BF, Al-Amri AM, Al-Muhanna FA. Transport Characteristics of patients on automated peritoneal dialysis may not affect their lipid profile. Saudi J Med Med Sci 2013;1:82-7

How to cite this URL:
Al-Hwiesh AK, Aloadh NA, Abdul-Rahman IS, Al-Dhafery BF, Al-Amri AM, Al-Muhanna FA. Transport Characteristics of patients on automated peritoneal dialysis may not affect their lipid profile. Saudi J Med Med Sci [serial online] 2013 [cited 2020 Dec 4];1:82-7. Available from: https://www.sjmms.net/text.asp?2013/1/2/82/123652


  Introduction Top


Renal failure is associated with abnormal lipoprotein metabolism leading to an accelerated atherosclerotic state. [1],[2] Abnormalities in lipoprotein metabolism are more common in patients on peritoneal dialysis (PD) than hemodialysis (HD). [3],[4],[5] Longer duration of continuous ambulatory peritoneal dialysis (CAPD)/ automated peritoneal dialysis (APD) is associated with aggravation of dyslipoproteinemia. [4],[5],[6] Peritoneal dialysis is associated with hypertriglyceridemia, hypercholesterolemia, increased serum concentrations of low-density lipoprotein cholesterol (LDLC), lipoprotein-a (LP-a), and apolipoprotein-B (ApoB), and decreased serum levels of high-density lipoprotein cholesterol (HDL-C). [5],[6],[7] CAPD patients with high peritoneal transport are exposed to an augmented atherogenic plasma lipid profile. [5]. Peritoneal transport status and residual renal functions may influence lipid alterations and their impact on cardiovascular mortality. [8],[9],[10],[11],[12] However there are controversial reports on this issue as some investigators have failed to notice any significant impact on lipoprotein metabolism in patients on peritoneal dialysis. [7],[13] The aim of this retrospective study was to analyze lipid profile in patients on APD and find its relationship with RRF and peritoneal transport parameters.


  Materials and Methods Top


The study was carried out in Nephrology Unit of King Fahd Hospital of the University of Dammam, Saudi Arabia. There were 40 patients (21 female and 19 male) with mean age of 52.05 ± 20.55 years (range 12-95). All patients were undergoing automated peritoneal dialysis for end-stage renal disease (ESRD) and the PD duration ranged from 18 to 70 months. None of the patients had been previously treated by hemodialysis, had a kidney transplant, or was maintained on medications known to affect plasma lipids before starting peritoneal dialysis. All the patients were on night cycler with dialysis prescription of 2 bags of 2.27% Dianeal exchanged over 9 hours and last fill of 7.5% Extraneal 2 L (supplied by the Baxter Company Ltd.). Transporter status was determined at 6 weeks of starting APD by a semi-quantitative assessment, peritoneal equilibration test (PET), based on the ratio of creatinine in the dialysate to plasma after a standardized 4-h dwell (D/Pcr). [14] Patients were categorized according to PET (low 0.5-0.64, low-average <0.65, high-average 0.65-0.80 and high ≥0.81). KT/V was calculated according to the standard method, [15] where KT is the total 24 h urea clearance (peritoneal plus urinary) multiplied by 7 to obtain KT per week, and V is the urea volume obtained from the Watson formula [16] that estimates urea volume of distribution as a function of gender, height, and actual weight. Patients were divided into two groups based on presence (24 hour urine output >200 ml/day) or absence (24 hour urine output ≤200 ml/day) of residual renal function. Cancer antigen 125 (CA-125) was also estimated at fixed time intervals during the period of study.

Blood samples were drawn after an overnight fast from an antecubital vein for routine chemistry including glucose, serum albumin, blood urea nitrogen, serum creatinine and electrolytes and collected in plain tubes. Blood sample for lipid profile were collected in EDTA-containing tubes. The samples were taken without interruption of PD at baseline and every 3 months for a period of one year. The samples were analyzed at the University Hospital itself. Plasma concentrations of total cholesterol and triglycerides were measured by enzymatic procedures. [17] High-density lipoprotein (HDL-C) was measured after precipitation of ApoB-containing lipoproteins in whole plasma by heparin-manganese chloride. [18] LDL-C was determined according to the method of Friedewald. [19]

Statistical analysis

The statistical analysis was carried out using Statistical Package for Social Sciences (SPSS Inc., Chicago, IL, version 15.0 for Windows). All quantitative variables were estimated using mean or median and measures of dispersion standard deviation or IQR. Normality of data was checked by measures of skewness and Kolmogorov Smirnov tests of normality. For normally distributed data, means were compared using t-test and for skewed data comparison was done using Mann-Whitney test for two groups. Qualitative or categorical variables were described as frequencies and proportions. Proportions were compared using Chi-square or Fisher's exact test whichever was applicable. For time-related variables, MANOVA was applied. One-way ANOVA was applied for within group comparisons. All statistical tests were two-sided and performed at a significance level of α =0.05.


  Results Top


Forty ESRD patients undergoing APD with day time exchange with icodextrin were analyzed in this cross-sectional study. The study included 21 (52.5%) females and 19 (47.5%) males with mean age of 52 ± 20.55 (range 12-95 years). Cause of ESRD included diabetic nephropathy in 24 (60%) patients, hypertensive nephrosclerosis in 6 (15%), reflux nephropathy in 4 (10%), chronic glomerulonephritis in 3 (7.5%) and lupus nephritis and acute cortical necrosis in 1 (2.5%) each. There was no significant difference between the diabetic and non-diabetic patients with respect to type of membrane transport status at baseline (P value 0.541). Five patients (12.5%) had high transporter status, 31 (77.5%) had high-average, 4 (10%) had low-average and there were no patients with low transporter status.

Patients were divided into 3 groups based on their transport characteristics (high, high-average and low-average) and their mean baseline, 6 months and 1-year lipid profile, serum albumin and CA-125 were correlated as depicted in [Table 1]. There was no difference in the total cholesterol, triglyceride, and serum HDL at baseline, 6 months and 1 year among patients with different transport characteristics. Patients with high transporter had lower HDL value compared to those with high-average and low-average transport characteristic at 6 months (P < 0.05). However, this significance was lost at the end of 1 year of follow-up. The levels of serum albumin at different time periods also did not correlate with the various lipid parameters as well as the patient's transport status. As regards the KT/V status [Figure 1], the patients with high transporter status had higher KT/V compared to patients in the other two groups (P < 0.05).
Figure 1: KT/V of high, high-average and low-average transporters

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Table 1: Lipid profile and other parameters in APD patients with various transporter status

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There was no significant difference in lipid profile in patients with presence or absence of residual renal function [Table 2].
Table 2: Lipid profile and RRF correlation

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CA-125 values [Table 1] at baseline negatively correlated with the duration of PD (correlation coefficient of 0.130). Change in CA-125 over 12 months not statistically significant when seen across various membrane transport groups. None of our patients encountered peritonitis episodes during the study period.


  Discussion Top


Patients on peritoneal dialysis are at high cardiovascular (C-V) risk, and dyslipidemia, one of the major traditional C-V risk factors, and is a common complication in chronic kidney disease (CKD). [1],[2],[20] Even long-term peritoneal dialysis has been found to have direct correlation with cardiac valve calcification, which is an important predictor for all-cause mortality and cardiovascular mortality in CKD patients. [21] Initiation of PD leads to absorption of high glucose in the dialysate, and in high transporters, with their large effective peritoneal surface area and/or higher intrinsic membrane permeability, the glucose load becomes large (may be up to 400 g/day). [22] This, combined with uremic insulin resistance is associated with pronounced, potentially atherogenic alterations in the lipoprotein pattern in the patients on maintenance PD. [3],[4] Previous studies have discussed the pathogenic mechanisms of dyslipidemia and its management in peritoneal dialysis. [23],[24],[25]

The main lipid alterations seen in patients on peritoneal dialysis are elevated triglycerides, cholesterol, LDL and VLDL with decrease in HDL. A number of factors may influence the severity of these abnormalities. These include the residual renal function at the initiation of PD, the transport status of the patient, the adequacy of PD as determined by the weekly KT/V, nutritional status and the type of dialysis solutions used. In the present study we have attempted to correlate the observed lipid alterations including the total cholesterol, triglycerides, HDL and LDL in relation to some of these transport variables.

Various investigators have observed significant relationship of the residual renal functions and dyslipidemia in PD patients. However definition of RRF varied in these studies with urine output ranging between 200 and 500 ml/day and glomerular filtration rate (eGFR) ≥2 ml/min/1.73 m 2 . Chen et al. [26] had observed a significant correlation between the change in HDL-C and the decline of RRF (r =0.177, P = 0.048), in addition, the change in the former was found by the authors to be independent of PD duration or the level of the highly sensitive C-reactive protein (r =0.233, P = 0.04). Similar observation was made by Kagan et al. in an earlier study. [27] Using the definition of >200 ml/day, we did not find any significant difference in serum triglyceride and HDL concentration in patients with or without RRF similar to the conclusion of other authors. [28]

Peritoneal transport may have significant impact on the lipid abnormalities in long duration PD. It has been reported that high transporters may have a more pro-atherogenic lipid profile. [8],[29] In a study of 32 patients undergoing long-term CAPD, Kagan et al. observed that the patients with a high transport status had lower ultra-filtration capacity, higher glucose absorption rate and increased loss of plasma proteins including albumin, and HDL compared to low transporters. [8] These patients also had increased levels of plasma triglycerides and very-low-density lipoproteins. Similarly, Haraldsson et al. [30] using the transport characteristic of peritoneal dialysis capacity (PDC); a better index of membrane permeability than PET, observed that patients with high PDC had more protein loss and worse pro-atherogenic lipid profile. These studies also stressed the role of the duration of PD besides the inherent transport characteristics of the CAPD patients in the alteration of their lipid profile. High peritoneal transporter, malnutrition and inflammation atherosclerosis syndrome resemble each other in that they are both characterized by accelerated atherosclerosis, hypoalbuminemia and malnutrition. [31],[32]

Just as we failed to find any relationship of the transport status and dyslipidemia, many other studies had the same conclusions. [12],[13],[33] In a study of 153 patients on automated peritoneal dialysis (total PD patients 193) who were grouped into low-average, high-average and high transport status as we have done in our study, Yang et al. concluded that higher peritoneal transport is not a significant independent risk factor for either mortality or death-censored technique failure. [13] Similar observations were made by Chang et al., who also repowered discordance between the high transport and malnutrition and associated mortality in their patients on APD. [33] The better outcome in high transport in our study as well as these studies might be attributed to the fact that previous reports of adverse effects of inherent high peritoneal permeability were based on CAPD patients. This better outcome, just discussed, may be because patients on APD have better fluid management. [13],[33]

Most of the patients with high transport status have lower serum albumin (increased loss in peritoneal fluid) and that is responsible for malnutrition and associated morbidity. However in our study we did not find such correlation between hypoalbuminemia and higher peritoneal permeability. We also failed to demonstrate any relation of dialysis adequacy measured by KT/V with the lipid alterations in our patients. This observation is in accordance with other studies. [32],[ 33] The CKD patients having diabetes mellitus are said to have more atherosclerotic lipid profile than non-diabetics. However no such difference was noted in our patients and this may be because of the relatively small number of patients in each category.

Cancer antigen 125 (CA-125); a marker of mesothelial cell mass, and determinant of in vivo biocompatibility of (new) dialysis solutions, was initially thought to reflect peritoneal membrane permeability [34] and has not been found to correlate with peritoneal transport status. [35] We studied the CA-125 in all patients in relation to their lipid abnormalities and their transport status. We did not find any correlation between these parameters. Perhaps, more studies are needed to confirm or deny any such relationship.

Although there have been isolated studies of lipids in patients on dialysis (hemo- and peritoneal dialysis) from the Middle East, [36] ours is the first study in the region that has attempted to explore the relationship of various transport variables with the dyslipidemia. In addition, our study was solely based on patients undergoing APD as compared with earlier studies of dyslipidemia that were conducted in the CAPD patients. This might also explain why our patients did not show the expected more severe atherogenic hyperlipidemia and hypoalbuminemia in high transporters as compared with patients having high-average and low-average transport status. Similarly we could not find any relation of hyperlipidemia with RRF, KT/V or CA-125.

To conclude, patients undergoing regular APD showed abnormal lipid profile but with no correlation of hyperlipidemia with the age, underlying disease and the transport characteristics as well as CA-125. Our study has the limitations of a small sample size and only few lipid parameters were analyzed.


  Acknowledgment Top


The authors acknowledge with appreciation the staff of Peritoneal Dialysis Unit for providing excellent patient follow-up and for meticulous organization of the patients' medical records.

 
  References Top

1.Shoji T, Abe T, Matsuo H, Egusa G, Yamasaki Y, Kashihara N, et al. Committee of Renal and Peripheral Arteries, Japan Atherosclerosis Society. Chronic kidney disease, dyslipidemia, and atherosclerosis. J Atheroscler Thromb 2012;26;19:299-315.  Back to cited text no. 1
    
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4.Johansson AC, Samuelsson O, Attman PO, Haraldsson B, Moberly J, Knight-Gibson C, et al. Dyslipidemia in peritoneal dialysis-relation to dialytic variables. Perit Dial Int 2000;20:306-14.  Back to cited text no. 4
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8.Kagan A, Bar-Khayim Y, Schafer Z, Fainaru M. Heterogeneity in peritoneal transport during continuous ambulatory peritoneal dialysis and its impact on ultrafiltration, loss of macromolecules and plasma level of proteins, lipids and lipoproteins. Nephron 1993;63:32-42.  Back to cited text no. 8
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