Lipoprotein alterations in hemodialysis: differences between diabetic and nondiabetic patients

Omega-3 Fatty Acids Reduce Remnant-like Lipoprotein Cholesterol and Improve the Ankle-Brachial Index of Hemodialysis Patients with Dyslipidemia: A Pilot Study

Background and Objectives: Omega-3 fatty acids have potent lipid-lowering and antiplatelet effects; however, randomized controlled trials have yet to examine the effect of high-dose omega-3 fatty acid administration on peripheral artery disease (PAD) in hemodialysis patients with dyslipidemia. Therefore, this study aimed to evaluate the effects of eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) on the ankle-brachial index (ABI) and remnant-like lipoprotein cholesterol (RLP-C) levels, which are indicators of PAD severity. Materials and Methods: Thirty-eight participants (mean age: 73.6 ± 12.7 years) were randomly assigned using stratified block randomization to either conventional therapy alone or conventional therapy supplemented with high-dose EPA/DHA (EPA: 1860 mg; DHA: 1500 mg) for a three-month intervention period. Patients in the conventional therapy alone group who opted to continue were provided with a low-dose EPA/DHA regimen (EPA: 930 mg; DHA: 750 mg) for an additional three months. The baseline and 3-month values for RLP-C, an atherogenic lipid parameter, and the ABI were recorded. Results: The results of the 3-month assessments revealed that the mean RLP-C changes were -3.25 ± 3.15 mg/dL and 0.44 ± 2.53 mg/dL in the EPA/DHA and control groups, respectively (p < 0.001), whereas the changes in the mean ABI values were 0.07 ± 0.11 and -0.02 ± 0.09 in the EPA/DHA and control groups, respectively (p = 0.007). In the EPA/DHA group, a significant negative correlation was found between the changes in RLP-C levels and the ABI (r = -0.475, p = 0.04). Additionally, the change in the RLP-C levels independently influenced the change in the ABI in the EPA/DHA group, even after adjusting for age, sex, and statin use (p = 0.042). Conclusions: Add-on EPA/DHA treatment improved the effectiveness of conventional therapy (such as statin treatment) for improving the ABI in hemodialysis patients with dyslipidemia by lowering RLP-C levels. Therefore, clinicians involved in dialysis should focus on RLP-C when considering residual cardiovascular disease risk in hemodialysis patients and should consider screening patients with elevated levels.

Serum LDL Levels are a Major Prognostic Factor for Arteriovenous Fistula Thrombosis (AVFT) in Hemodialysis Patients

Introduction

Arteriovenous fistula thrombosis (AVFT) is still a common cause of morbidity in patients undergoing regular hemodialysis (HD). Many factors have been found to induce AVFT. Some of those factors are local and others are systemic ones. In this study, we evaluated some local and systemic factors simultaneously, to predict the most potent risk factor for AVFT in HD patients.

Patients and methods

One hundred and eighteen patients aged 20–80 yrs with end-stage renal disease (ESRD) were evaluated prospectively for a period of 14 months. First, anticardiolipin antibodies (ACLA), TG, cholesterol, low density lipoprotein (LDL) and high density lipoprotein (HDL) were analyzed by conventional methods. Other basic data were accessed from patients' medical records. All fistulas were evaluated clinically as patent at the start of this study. Patients were followed-up for any evidence of AVFT within 14 months. Finally, all factors (diabetes, hypertension, presence of ACLA, ultrafiltration ≥3 L, age, gender, weight, hypotension during dialysis, fistula site, epoetin alpha usage, TG, HDL, LDL and total cholesterol) were analyzed in a stepwise regression analysis.

Results

Eighteen episodes of AVFT documented with Doppler sonography occurred in 17 patients (15.3%). Regression analysis showed only LDL values were the AVFT predictor in our patients (p=0.002, β-coefficient=0.3). Kaplan-Meier analysis showed a significantly lower AVF patency time in patients with LDL >130 mg/dl than those with LDL <130 mg/dl (log rank=0.0014).

Discussion

LDL value is a major prognostic factor for AVFT in HD patients and lowering it to <130 mg/dl could improve fistula patency.

High-sensitivity C-reactive protein, apolipoproteins, and residual diuresis in chronic kidney disease patients undergoing hemodialysis

BACKGROUND

Residual diuresis (RD) is the simplest method for measuring renal residual function in patients with chronic kidney disease (CKD). A reduction in RD is associated with intensification of the inflammatory process caused by uremia. However, little is known regarding the relation between RD and inflammatory markers in these patients. We verify possible associations among the hs-CRP, atherogenic factors, and RD, in patients with CKD undergoing hemodialysis.

METHODS

This study enrolled 80 patients with CKD undergoing hemodialysis. Patients were stratified according to RD in anuric (RD-) group (n = 47) and non-anuric (RD+) group (n = 33). Urine volumes were collected in a 24 h period during the interdialytic period. Serum high-sensitivity C-reactive protein (hs-CRP), and apolipoprotein (Apo) A1 and B levels were measured after fasting for 12 h.

RESULTS

Serum hs-CRP levels were higher in the RD- group than in the RD+ group (P = 0.015). In the total group, hs-CRP was significantly correlated with RD (r = - 0.25, P = 0.025) and Apo AI (r = - 0.25, P = 0.024). A greater proportion of patients had reduced plasma concentrations of Apo AI in the RD- group (31.9 %) compared with the RD+ group (9.1 %) (P = 0.014).

CONCLUSION

This study shows a relationship between RD and the hs-CRP in patients undergoing hemodialysis. Although the inflammatory state was verified in a large part of the CKD population, patients without RD had more elevated hs-CRP serum levels than those with RD.

High-Density Lipoprotein Subfractions and Their Oxidized Subfraction Particles in Patients with Chronic Kidney Disease

AIM

Chronic kidney disease (CKD) may lead to reduced concentrations of high-density lipoprotein (HDL) and its subfractions (HDL2 and HDL3), and damage them via inflammation and oxidative stress. The present study aimed to determine the contribution of such changes to cardiovascular disease (CVD) in patients with CKD.

METHODS

The levels of total cholesterol, low-density lipoprotein cholesterol, HDL-C, HDL2, HDL3, apolipoproteins, malondialdehyde-modified LDL (MDA-LDL), oxidized (ox) HDL, oxHDL2, and oxHDL3 were measured in blood samples from patients with CKD (stages 2-5, n=86) who were not on dialysis and from patients undergoing hemodialysis (CKD stage 5D, n=25). The patients were followed up for 28±9 months after baseline examinations and CVD events were recorded.

RESULT

The levels of HDL3 and ApoA1 in HDL3 fraction decreased according to CKD severity, whereas those of HDL2 and ApoA1 in HDL2 fraction did not differ. The levels of oxHDL were similar across CKD stages. The levels of oxHDL3 and MDA-LDL were decreased, whereas those of oxHDL2 increased according to CKD severity. Multivariate analyses using the Cox proportional hazards model selected high levels of oxHDL and its subfractions, and those adjusted with HDL-C and HDL subfractions or ApoA1 in HDL fractions respectively, compared with HDL-C and HDL subfractions or ApoA1 in HDL fractions alone as independent risk factors for CVD events.

CONCLUSION

The levels of HDL subfractions and their oxidized subfraction particles differed among patients with CKD. The increasing levels of oxHDL subfractions might cause a high frequency of CVD events in such patients.

Endothelial Lipase Activity Predicts High-Density Lipoprotein Catabolism in Hemodialysis

Objective—

A novel phospholipase assay was used to measure for the first time the behavior of endothelial and hepatic phospholipase activities in postheparin human plasma of hemodialyzed patients and its relationship with atherogenic and antiatherogenic lipoprotein levels.

Methods and Results—

Endothelial and hepatic phospholipase activity was assessed in a total SN1-specific phospholipase assay, using (1-decanoylthio-1-deoxy-2-decanoyl-sn-glycero-3-phosphoryl) ethylene glycol as the substrate. Hemodialyzed patients presented lower values of total and hepatic phospholipase activity than controls: 4.4 (1.9–9.0) versus 7.5 (3.6–18.0) and 2.6 (0.7–6.2) versus 6.6 (1.3–15.2) μmol of fatty acid released per milliliter of postheparin plasma per hour, respectively ( P <0.001); however, endothelial lipase (EL) phospholipase activity was increased in patients: 1.7 (0.8–3.0) versus 1.1 (0.1–2.7) μmol of fatty acid released per milliliter of postheparin plasma per hour ( P =0.008). EL was negatively associated with high-density lipoprotein (HDL)-cholesterol ( r =–0.427; P =0.001), and apolipoprotein A-I levels, total phospholipase, and hepatic lipase activity were directly associated with low-density lipoprotein-cholesterol and apolipoprotein B. The association of EL and HDL-cholesterol remained significant when adjusting for waist circumference (β=–0.26; P =0.05), and the effect of hepatic lipase on low-density lipoprotein-cholesterol continued after adjusting for age (β=0.46; P = 0.001).

Conclusion—

Our results support the hypothesis that EL is the predominant enzyme responsible for lipolytic catabolism of HDLs in hemodialyzed patients and resolve the apparent paradox observed between low hepatic lipase activity and decreased HDL-cholesterol levels observed in these patients. In addition, the ability to assess total hepatic lipase and EL phospholipase activity in plasma will increase our knowledge of the mechanisms involved in controlling HDL levels and cardiovascular risk in hemodialyzed patients, as well as other populations with low levels of HDL-cholesterol.

HDL-associated enzymes and proteins in hemodialysis patients

OBJECTIVES

To evaluate HDL-associated proteins and enzymes and their relation with lipoprotein profile and inflammatory markers in chronic renal patients on hemodialysis.

DESIGN AND METHODS

We studied 53 patients under hemodialysis and 32 healthy subjects as controls. We compared plasma lipids, Apoprotein-AI and hs-CRP, as a marker of chronic inflammation. We evaluated proteins and enzymes associated to HDL, involved in several points of lipoprotein metabolism: CETP, paraoxonase and LpPLA2 activities. Hepatic lipase was measured in postheparin plasma.

RESULTS

Patients showed higher triglycerides and lower LDL-, HDL- and total-cholesterol than controls (p<0.05). Also, in comparison with controls, Apoprotein-AI, paraoxonase and hepatic lipase were lower, while CETP was higher (p<0.03). LpPLA2 did not show changes between groups.

CONCLUSION

Beyond plasma lipid-lipoprotein profile, other factors could contribute to induce a pro-oxidative and pro-inflammatory status. The protective role of HDL does not only depend on its concentration, but also on its functionality.

Disorders of lipid metabolism and chronic kidney disease in the elderly

The growing population of elderly with chronic kidney disease (CKD) is at greater risk for cardiovascular disease given an independent risk of CKD, as well as from added dyslipidemia of aging and renal dysfunction. Changes in lipid metabolism with more isodense and high-dense, triglyceride-rich particles, low high-density lipoprotein cholesterol, and increased triglyceride levels occur with CKD and aging, which are noted to have significant atherogenic potential. In addition, lipid abnormalities may lead to the progression of CKD. Cardiovascular mortality in the end-stage renal disease population is more than 10 times higher than the general population. Treatment of dyslipidemia in the general population suggests important benefits both in reducing cardiovascular risk and in the prevention of cardiovascular disease. Secondary analyses of elderly subgroups of various large prospective studies with statins suggest treatment benefit with statin use in the elderly. Similarly limited data from secondary analyses of CKD subgroups of larger prospective trials using statins also suggest a possible benefit in cardiovascular outcomes and the progression of kidney disease. However, randomized trials have yet to confirm similar benefits and targets of treatment for dyslipidemia in the elderly with CKD and end-stage renal disease. Treatment in the elderly with CKD should be individualized and outweigh risks of side effects and drug-drug interactions. There is a need for further specific investigation of dyslipidemia of CKD in the aging population in relation to renal disease progression and cardiovascular outcome.

Iron status and cardiovascular risk factors in patients with haemodialysis versus patients with ischaemic heart disease

AIM

The study aimed to investigate whether imbalanced iron status in patients with haemodialysis coexisted with abnormal lipid profile, higher inflammatory status and altered growth hormone-insulin-like growth factor (GH-IGF)-I axis and to compare these biochemical markers with patients with ischaemic heart disease.

METHODS

Serum samples for biochemical and immunological analyses were collected from 74 normal subjects, 138 patients with ischaemic heart disease (IHD) and 115 patients on haemodialysis (HD).

RESULTS

Compared with normal subjects, lower serum iron, lower total iron-binding capacity (TIBC) and higher ferritin in HD patients coexisted with decreases in high-density lipoprotein cholesterol and total bilirubin as well as increases in lactate dehydrogenase (LDH), interleukin (IL)-6, C-reactive protein (CRP) and IL-10. Decreased IGF-I and increased GH were found in HD patients whereas unchanged GH-IGF axis were found in IHD patients. Compared with IHD, much higher ferritin, lower TIBC, lower bilirubin and higher LDH levels were found in HD patients.

CONCLUSION

Imbalanced iron status in patients on HD coexisted with abnormal lipid profiles, increased anaerobic activity and higher inflammatory status, which suggests that imbalanced iron status in HD patients may play a deleterious role in cardiovascular pathophysiology. Altered GH-IGF axis found in HD patients was more obvious than in IHD patients. This may imply that the GH-IGF axis system is modulated or adapted by HD.

Chronic renal failure in diabetic patients increases lipid risk factors for atherosclerosis

Diabetic patients are at high risk of cardiovascular disease and the risk is amplified in the presence of nephropathy, which may be partially attributed to modifications in lipoproteins. Moreover, lipoprotein profile may be affected by incipient nephropathy, glomerulopathy, and mild or severe renal failure. The aim of our study was to evaluate whether chronic renal failure (CRF) changes lipoprotein profile and apo A-I urinary excretion in diabetic subjects with glomerulopathy in comparison with non-diabetic subjects with glomerulopathy and CRF. Diabetic (n=25) and non-diabetic (n=10) patients with glomerulopathy and CRF showed significantly higher LDL-cholesterol, non-HDL-cholesterol and HDL-triglyceride levels than diabetic individuals without CRF (n=10). Arylesterase and paraoxonase activities did not show any difference between groups. Apo A-I could not be detected in urine samples from diabetic patients without CRF. All diabetic subjects with glomerulopathy and CRF who presented proteinuria above 6.5 g/24 h showed detectable urinary apo A-I (range=13.1-61.0 mg/24 h). Similarly, all non-diabetic patients with glomerulopathy and CRF who had proteinuria above 8.0 g/24 h also evidenced detectable apo A-I in urine (range=25.6-557.3 mg/24 h). Urinary apo A-I showed positive and significant correlations with urea (r=0.73, p<0.05) and proteinuria (r=0.97, p<0.0001), and a negative correlation with albumin plasma levels (r=-0.68, p<0.05). In conclusion, the presence of CRF in diabetic patients was associated with a more atherogenic lipoprotein profile.

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.

A rapid methodology for the isolation of intermediate-density lipoprotein: characterization of lipid composition and apoprotein content

BACKGROUND

Intermediate-density lipoprotein (IDL) is a structurally related precursor of low-density lipoprotein (LDL). Although found in significantly lower levels, extensive evidence suggests that IDL shares LDL's capacity to promote atherosclerosis. To assist further investigation into IDL's composition and physiological relevance, we have established a rapid method to extract IDL from plasma.

METHODS

IDL was isolated from plasma by sequential floatation ultracentrifugation in 3 h, a significantly shorter isolation time than previously published methods. Apoproteins (apo) B100, CIII, and E, together with the level of albumin contamination, were quantified using single radial immunodiffusion. The lipid composition of IDL was measured using automated enzyme assays.

RESULTS

The percent recovery of lipid from all lipoprotein fractions (VLDL+IDL+LDL+HDL) was 97.0+/-4.9% when compared to total plasma lipid. IDL had a reduced concentration of apo CIII, apo E, triglyceride, and free cholesterol, and had a higher concentration of apo B100, cholesterol ester, and phospholipid when compared to VLDL. Pure IDL migrated in advance of LDL during agarose electrophoresis.

CONCLUSIONS

This rapid technique minimizes damage to the integrity of IDL and yields sufficient quantities to allow accurate assessment of composition and susceptibility to in vitro oxidation, and thus facilitates further investigation of IDL in the development of atherosclerosis.

Utility of non-high-density lipoprotein cholesterol in hemodialyzed patients

Non-high-density lipoprotein-cholesterol (HDL-C) is proposed as a strong predictor of cardiovascular disease (CVD). Measuring non-HDL-C, as total cholesterol minus HDL-C, is convenient for routine practice because, among other advantages, fasting is not required. There are limited data of non-HDL-C in end-stage renal disease patients. We applied non-HDL-C calculation to 50 chronic renal patients receiving maintenance hemodialysis (HD) and 20 healthy subjects, apart from measurement of low-density lipoprotein (LDL), very-low-density lipoprotein (VLDL) HDL, intermediate-density lipoprotein-cholesterol (IDL-C), apoprotein (apo) B, and triglycerides. HD patients presented higher plasma triglycerides and IDL-C and lower HDL-C than the control group, even after adjustment for age (P < .05). VLDL-C increased in HD patients (P < .001) while differences in non-HDL-C did not reach significance (P = .08). To detect which parameter constitutes a better marker of CVD risk among HD patients, a receiver-operating characteristic (ROC) analysis was performed considering HD patients in the highest risk group for CVD. In the ROC graphic, the plots of VLDL and IDL-C exhibited the greater observed accuracy and the best performance, while non-HDL-C showed a curve close to the 45 degrees line indicating that this parameter is a poor discriminator for evaluating CVD risk among HD patients. Non-HDL-C calculation, expressing all apo B-containing lipoproteins, may miss the significant contribution of each atherogenic lipoprotein, such as increase in IDL. This observation would not be in agreement with the currently proposed application of non-HDL-C a useful tool for risk assessment among HD patients.

Improvement in Lipid Profile by Nocturnal Hemodialysis in Patients with End-Stage Renal Disease

Dyslipidemia is associated with uremia and an increased risk of cardiovascular disease. The uremic dyslipidemia syndrome is characterized by an abnormal lipoprotein profile that results in (1) an elevation of triglyceride (TG) rich lipoproteins, very low density lipoprotein (VLDL), and intermediate density lipoprotein (IDL); (2) a reduction in high density lipoprotein (HDL) levels; and (3) a higher fraction of atherogenic, small dense low density lipoprotein (LDL). Nocturnal hemodialysis (NHD) is a home based renal replacement therapy that provides better control of uremia than conventional hemodialysis (CHD) and that may improve dyslipidemia. To test this hypothesis, we conducted a prospective cohort study of 11 patients with end-stage renal disease (ESRD) (age 38+/-3 years [mean+/-SEMI) before and after conversion from CHD to NHD. Weight, blood pressure (BP), serum hemoglobin (Hb), phosphate (PO4), and albumin (Alb) were assessed at baseline and at 3 months after conversion to NHD. Dialysis dose on CHD and NHD was assessed using equilibrated Kt/V (eKt/V). A 12 hour fasting lipid profile (total cholesterol [TC], TG, HDL, LDL, HDL/TC) was obtained once while on CHD and at 3 months after conversion to NHD. After conversion from CHD to NHD, eKt/V per session increased significantly (from 1.13+/-0.05 to 2.10+/-0.07; p < 0.05). TG level decreased significantly (from 2.05+/-0.30 to 1.01+/-0.14 mmol/L; p < 0.001), and HDL level increased significantly (from 1.17+/-0.13 to 1.65+/-0.14 mmol/L; p < 0.001). HDL/TC also increased significantly (from 0.26+/-0.03 to 0.35+/-0.02; p < 0.001). TC and LDL levels were unchanged. HDL levels increased and TG levels decreased in all patients. There was no difference in weight, Hb, and Alb. Systolic BP and PO4 were significantly lower, and there was a trend toward a reduction in cardiovascular medications. The mechanism for the improvement in lipid profile requires further study.

Post-dialysis retention of blood lipoproteins and apolipoproteins in patients with end-stage renal disease on maintenance haemodialysis in Kuwait

BACKGROUND

The commonest cause of death in patients with end-stage renal disease (ESRD) on maintenance haemodialysis (MHD) is coronary heart disease (CHD). It has been suggested that dyslipidaemia, an important CHD risk factor, may be worsened by dialysis. This study evaluated changes in blood lipoproteins and apolipoproteins after dialysis in ESRD patients on MHD.

METHODS

The subjects were 57 (20 M, 37 F; 24 diabetic, 33 nondiabetic) patients with ESRD, aged 21-73 years, undergoing MHD at a major Dialysis Unit in Kuwait. Pre- and post-dialysis non-fasting blood samples were collected from each subject on the same day, and analyzed for plasma glucose, urate, triglycerides (TG), total cholesterol (TC), HDL, LDL and apolipoprotein (apo) A1 and B. Pre- and post-dialysis levels for each of the analytes were compared for the diabetic and non-diabetic subgroups of patients and linear correlations sought between Delta values (corresponding to differences between pre- and post-dialysis levels) of the lipoproteins and apolipoproteins.

RESULTS

There was a general trend towards significant increases in post-dialysis TC, HDL, LDL, and non-HDL levels in both sub-groups, and additionally for the non-diabetic, TG, apo A1 and apo B. The pre- to post-dialysis increases were essentially similar for the diabetic and non-diabetic groups-Diabetic: TC 14%, HDL 25%, LDL 19%, non-HDL 16%, apo A1 14%, apo B 10%; Non-diabetic: TC 20%, TG 29%, HDL 25%, LDL 26%, non-HDL 21%, apo A1 14%, apo B 14%. Generally, there were significant correlations between Delta values for the lipoproteins and apolipoproteins (r, 0.50-0.92) in both groups.

CONCLUSION

Levels of atherogenic lipoproteins increase post-dialysis in diabetic and non-diabetic patients with ESRD and the changing levels of these lipoproteins correlate significantly with corresponding changes in levels of apolipoproteins. The increase in lipid levels is therefore related to retention of apo A1 and B with each dialysis. We speculate that, with repeated dialysis, dyslipidaemia may get progressively worse and further accentuate CHD risk.