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J Am Soc Nephrol 14:732-738, 2003
© 2003 American Society of Nephrology

LCAT-Dependent Conversion of Pre{beta}1-HDL into {alpha}-Migrating HDL is Severely Delayed in Hemodialysis Patients

Takashi Miida*, Osamu Miyazaki{dagger}, Osamu Hanyu{ddagger}, Yuichi Nakamura§, Satoshi Hirayama{ddagger}, Ichiei Narita, Fumitake Gejyo, Isei Ei||, Kazuyuki Tasaki#, Yutaka Kohda[], Takashi Ohta@, Syogo Yata@, Isamu Fukamachi{dagger} and Masahiko Okada*

*Division of Clinical Preventive Medicine, Department of Community Preventive Medicine, Niigata University, Graduate School of Medical and Dental Sciences, Niigata, Japan; {dagger}Daiichi Pure Chemicals, Diagnostics Research Laboratories, Tokai Research Group, Tokai, Ibaraki, Japan; {ddagger}Division of Endocrinology and Metabolism, Department of Homeostatic Regulation and Development, Niigata University, Graduate School of Medical and Dental Sciences, Niigata, Japan; §Division of Cardiology, Department of Cardiovascular and Vital Control, Niigata University, Graduate School of Medical and Dental Sciences, Niigata, Japan; Division of Clinical Nephrology and Rheumatology, Department of Homeostatic Regulation and Developments, Niigata University, Graduate School of Medical and Dental Sciences, Niigata, Japan; ||Santo Daini Iin, Niigata, Japan; #Division of Nephrology, Saiseikai Niigata Daini Hospital, Niigata, Japan; []Division of Nephrology, Shinraku-en Hospital, , Niigata, Japan; and @Division of Nephrology, Kido Hospital,, Niigata, Japan.

Correspondence to Dr. Takashi Miida, Division of Clinical Preventive Medicine, Department of Community Preventive Medicine, Niigata University, Graduate School of Medical and Dental Sciences, Asahimachi 1-754, Niigata, Niigata 951-8510, Japan. Phone: +81-25-227-2333; Fax: +81-25-223-0996;


   Abstract
Top
 Abstract
Introduction
 Materials and Methods
 Results
 Discussion
 References
 
ABSTRACT. Pre{beta}1-HDL is a minor HDL subfraction that acts as an efficient initial acceptor of cell-derived free cholesterol. During 37°C incubation, plasma pre{beta}1-HDL decreases over time due to its conversion to {alpha}-migrating HDL by lecithin:cholesterol acyltransferase (LCAT). This conversion may be delayed in hemodialysis patients who have decreased LCAT activity. To clarify whether LCAT-dependent conversion of pre{beta}1-HDL to {alpha}-migrating HDL is delayed in hemodialysis patients, pre{beta}1-HDL concentrations were determined in 45 hemodialysis patients and 45 gender-matched control subjects before and after 37°C incubation with and without the LCAT inhibitor. It was found that the baseline pre{beta}1-HDL concentration in hemodialysis patients was more than twice that in the controls (44.9 ± 21.4 versus 19.8 ± 6.7 mg/L apoAI; P < 0.001). After 2-h incubation, the LCAT-dependent decrease in pre{beta}1-HDL in hemodialysis patients was about one-third of that in the controls (30 ± 27 versus 97 ± 17% of baseline; P < 0.01). The LCAT-dependent rate of decrease in pre{beta}1-HDL levels (DRpre{beta}1) was the same for samples from hemodialysis patients exhibiting normal (>=1.03 mmol/L) and low HDL-cholesterol levels (32 ± 32 versus 28 ± 23% of baseline; NS). DRpre{beta}1 was positively correlated with LCAT activity (r = 0.617; P < 0.001). In conclusion, the LCAT-dependent conversion of pre{beta}1-HDL to {alpha}-migrating HDL is severely delayed in hemodialysis patients. The impaired catabolism of pre{beta}1-HDL may accelerate atherosclerosis in hemodialysis patients. E-mail: miida@med.niigata-u.ac.jp


   Introduction
Top
 Abstract
 Introduction
Materials and Methods
 Results
 Discussion
 References
 
Despite advances in the prevention and treatment of cardiovascular disease (CVD), patients undergoing hemodialysis (HD) suffer from markedly higher rates of CVD than the general population (1,2). Although hypercholesterolemia is a major risk factor for CVD in the general population, it is not common in HD patients (3–6). Rather, their lipoprotein profiles are characterized by reduced HDL-cholesterol (HDL-C) and elevated triglyceride (TG)-rich lipoprotein concentrations (3–6). In addition, the enzymes and transfer proteins involved in lipoprotein metabolism tend to exhibit lowered activity in HD patients (4,5,7–10). These abnormalities may contribute significantly to the high frequency of CVD occurrence in HD patients.

Pre{beta}1-HDL, a specific HDL subfraction, stimulates cholesterol efflux from cell membranes in cell culture systems (11,12). The main components of pre{beta}1-HDL are apolipoprotein AI (apoAI) and phospholipid (11). Because phospholipid is easily dissociated from apoAI of pre{beta}1-HDL (13), pre{beta}1-HDL is probably similar to "free apoAI" in earlier studies (14,15). In normal plasma, lecithin:cholesterol acyltransferase (LCAT) converts pre{beta}1-HDL to {alpha}-migrating HDL (16,17), which transports esterified cellular cholesterol to the liver for further processing (18,19). Conversion of pre{beta}1-HDL to {alpha}-migrating HDL in vitro is blocked by inhibitors of LCAT activity (16), suggesting that LCAT plays a crucial role in the maturation of lipid-poor HDL to lipid-rich spherical HDL (19). LCAT activity has been previously demonstrated to be significantly lower in HD patients than in control subjects (8,9). "Free apoAI" is higher in the former than in the latter (14,15). Therefore, it is of great interest to investigate pre{beta}1-HDL metabolism in these patients. In this study, we determined whether LCAT-dependent conversion of pre{beta}1-HDL to {alpha}-migrating HDL is delayed in HD patients. We quantitated pre{beta}1-HDL concentrations using a sandwich enzyme immunoassay in conjunction with a monoclonal antibody specific for pre{beta}1-HDL (20).


   Materials and Methods
Top
 Abstract
 Introduction
 Materials and Methods
Results
 Discussion
 References
 
Study Population
The study population consisted of 45 patients (24 men and 21 women aged 23 to 77 yr) who had undergone HD for 4 to 5 h three times a week for more than 1 yr (the HD group). The duration of HD was 1 to 26 yr (median, 3 yr). In general, low-flux cellulose dialysis membranes had been used until 1985, and high-flux membranes, such as polymethylmethacrylate, polyacrylonitrile, polysulfone, and triacetate had been used thereafter. The causes of renal failure were chronic glomerulonephritis (n = 25), diabetic nephropathy (n = 13), chronic pyelonephritis (n = 3), nephrosclerosis (n = 2), and polycystic kidney disease (n = 2). We excluded patients who were taking lipid-lowering drugs or who suffered from overt infections or malnutrition. Of the 45 patients in the study population, nine had a history of cardiovascular events (cerebral infarction, n = 5; cerebral hemorrhage, n = 1; old myocardial infarction, n = 2; arteriosclerosis obliterans, n = 1), but they had been in stable condition for more than 6 mo. We also enrolled 45 healthy gender-matched volunteers (aged 22 to 76 yr) as the control group. In the subanalysis, we divided the HD patients into two subgroups: those with normal HDL (HDL-C >= 1.03 mmol/L) and those with low HDL (HDL-C < 1.03 mmol/L) (21).

Informed consent was obtained from each subject upon entry into the study population. This study was approved by the ethics committees of the individual participating institutions.

Samples
After a fast of at least 12 h, venous blood was withdrawn from each subject. Intravenous heparin injection significantly increases plasma pre{beta}1-HDL concentrations in normolipidemic subjects (T. Miida et al., unpublished data); therefore, blood samples for the HD group were taken just before HD. For assays of pre{beta}1-HDL or HDL subfractions, which were performed as described below, the blood was mixed with K2-EDTA at 1 g/L in a pre-chilled glass tube (22–26). To prevent the conversion of pre{beta}1-HDL to {alpha}-migrating HDL before assaying, the blood was centrifuged at 0°C to separate the plasma, which was kept on ice water until use (22).

For other assays, blood was withdrawn into a glass tube and allowed to coagulate at room temperature. Serum was then obtained by centrifugation. Most assays were performed with fresh samples, but cholesterol ester transfer protein (CETP) assays were performed with samples frozen at -80°C.

Laboratory Examinations
Total cholesterol (TC) and TG concentrations were measured enzymatically. HDL-C was measured by a commercial, homogenous assay (Determiner L HDL-C; Kyowa Medex, Tokyo, Japan). Apolipoprotein concentrations were measured by immunoturbitometry with kits from Daiichi Pure Chemicals (Tokyo, Japan), using a Hitachi-7170 autoanalyzer.

LCAT and CETP Assays
LCAT activity was determined by the method of Manabe and Itakura (Anasorb LCAT, Daiichi Pure Chemicals). In this method, liposomes composed of cholesterol and lecithin are used as an exogenous substrate; activity is calculated from the rate of decrease of free cholesterol during 37°C incubation. For some samples, the amount of LCAT was also measured by a sandwich enzyme immunoassay, using a monoclonal antibody against LCAT (27).

The amount of CETP was measured by enzyme immunoassay (CETP ELISA; Daiichi Pure Chemicals) (28). The intra- and inter-assay CV were 2 to 4%, and 5 to 7%, respectively.

Incubation Experiments
Plasma aliquots from some patients were placed in microcentrifuge tubes with or without 5,5'-dithio-bis(2-nitrobenzoic acid) (DTNB), an LCAT inhibitor. In preliminary experiments, 2.0 mM DTNB sufficiently blocked the conversion of pre{beta}1-HDL to {alpha}-migrating HDL (data not shown). The samples were incubated at 37°C, and the conversion reactions were stopped at various intervals by placing the sample tubes into ice water. Pre{beta}1-HDL concentrations were measured by an enzyme immunoassay, as described below. The LCAT-dependent rate of decrease of pre{beta}1-HDL (DRpre{beta}1) was calculated by the equation: Go


(1)

Where [pre{beta}1]120 min(DTNB) and [pre{beta}1]120 min are pre{beta}1-HDL concentrations at 120 min with and without DTNB, respectively, and [pre{beta}1]0 min is the pre{beta}1-HDL concentration at baseline (0 min).

Assay for pre{beta}1-HDL Concentration
The absolute concentration of pre{beta}1-HDL was measured by a sandwich enzyme immunoassay using the monoclonal antibody Mab 55201 (Daiichi Pure Chemicals). This antibody recognizes pre{beta}1-HDL but not any other HDL subfraction (20). In the incubation experiments, all samples from one subject were processed in the same analytical run. The intra-assay CV was 3 to 5% in the range of pre{beta}1-HDL concentrations found for the HD and control groups.

Assay for HDL Subfraction Concentration
The relative concentration of the HDL subfraction was determined by nondenaturing two-dimensional (2-D) gel electrophoresis as described previously (22–26). Pre{beta}1-HDL and {alpha}-migrating HDL were separated on a 0.75%-agarose gel in 50 mM barbital buffer (pH 8.6). Without prior equilibration, agarose gel pieces were directly applied to a 2 to 15% polyacrylamide slab gel in Tris-glycine buffer (pH 8.3). The separated HDL subfractions were electroblotted onto a nitrocellulose membrane in Tris-glycine buffer containing 20% (vol/vol) methanol. All procedures were carried out at 0°C.

A 125I-labeled polyclonal antibody (29) against human apolipoprotein AI (apoAI) was used for immunodetection. Using the resulting autoradiogram as a guide, each HDL subfraction was excised from the membrane, and its radioactivity was determined with a {gamma}-counter. The concentration of the HDL subfraction was expressed as the percentage of total plasma apoAI composed of the HDL apoAI subfraction (%AI). The precision of this method has been repeatedly verified (22–26).

Statistical Analyses
The comparative significance of variables between the different groups was assessed with an unpaired t test or Welch’s t test, whereas the significance of variables between the same groups was assessed using a paired t test or Wilcoxon signed-ranks test. The P-value indicating statistical significance was set at 0.05. All values are presented as the mean ± SD, unless otherwise stated.


   Results
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 Abstract
 Introduction
 Materials and Methods
 Results
Discussion
 References
 
Lipoproteins, LCAT, and CETP
HD patients exhibited abnormally low levels of HDL-related markers upon lipoprotein analysis. All constituents of HDL (HDL-C, apoAI, and apoAII) were significantly lower in the HD group than in the control group (Table 1). Twenty-one HD patients (46.7%) were classified as belonging to the low-HDL subgroup. On the other hand, constituents of TG-rich lipoproteins (TG, apoCIII, and apoE) were at significantly higher levels in the HD group than in the control group. TC, LDL-C, and apoB levels were similar for the two groups.


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  		Table 1. Lipoprotein profiles and HDL regulating factors, by patient group
 
As expected, LCAT activity was 35% lower in the HD group than in the control group (Table 1). In fact, LCAT activity was lower in the normal-HDL HD subgroup than in the control group (358 ± 87 {Delta}FC µmol/L per hour; P < 0.05), although it was higher than in the low-HDL HD subgroup (300 ± 95 {Delta}FC µmol/L per hour; P < 0.001). The amount of CETP was 14% lower in the HD group than in the control group.

Pre{beta}1-HDL Concentration
The mean pre{beta}1-HDL concentration in the HD samples was more than double that in the control samples (Figure 1, filled and open bars). This elevation in pre{beta}1-HDL levels was evident not only for the low-HDL HD subgroup but also for the normal-HDL HD subgroup (Figure 1, crosshatched bars).



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  		Figure 1. Baseline pre{beta}1-HDL concentrations. Fasting plasma was obtained from 45 hemodialysis patients (HD, closed bar) or 45 gender-matched healthy volunteers (Control, open bar). According to HDL-cholesterol concentration, HD patients were further divided into two groups (crosshatched bars); L-HDL (HDL-cholesterol <1.03 mmol/L), and N-HDL (HDL-cholesterol >=1.03 mmol/L). Pre{beta}1-HDL concentrations were measured by immunoassay using Mab 55201, a monoclonal antibody specific for pre{beta}1-HDL.

 
HDL Subfraction
We confirmed that pre{beta}1-HDL levels were increased in HD patients using native 2-D gel electrophoresis. The relative concentration of pre{beta}1-HDL was 2.6-fold greater in the HD group than in the control group (Figure 2). The pre{beta}2-HDL concentration was also increased in the HD group, although the increase was only 32% of the baseline level. HDL3 was the only subfraction of {alpha}-migrating HDL that exhibited a significant decrease in relative concentration for the HD group (Figure 2). The low-HDL and normal-HDL HD subgroups did not differ in the mean relative concentration of any HDL subfraction (data not shown), although the mean apoA l level was 28% lower in the former than in the latter (905 ± 129 versus 1265 ± 122 mg/L; P < 0.001).



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  		Figure 2. Distribution of apoAI among HDL subfractions. Fasting plasma was obtained from the HD (closed bars) and control groups (open bars). Nondenaturing 2-D polyacrylamide gel electrophoresis was performed as described in Materials and Methods. ApoAI-containing lipoproteins transferred to nitrocellulose membranes were visualized by immunoblotting using 125I-labeled polyclonal antibodies. The relative concentrations of the HDL subfractions were determined based on the radioactivity of each spot.

 
Incubation Experiments
Pre{beta}1-HDL catabolism during incubation at 37°C was severely impaired in the HD group. The intensities of pre{beta}1-HDL spots on 2-D gels for samples from the HD group did not decrease after incubation, and were not affected by DTNB (Figure 3, upper panels). For the control samples, however, the intensities of pre{beta}1-HDL spots decreased markedly after incubation. This decrease in pre{beta}1-HDL was completely inhibited by addition of DTNB (Figure 3, lower panels).



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  		Figure 3. Changes in 2-D gel electrophoresis patterns during incubation of plasma at 37°C. Fresh plasma from an HD patient (HD, upper panels) or a healthy volunteer (control, lower panels) was stored at 0°C or incubated at 37°C for 120 min in the absence or presence of 2 mM 5,5'-dithio-bis(2-nitrobenzoic acid) (DTNB) and subjected to 2-D gel electrophoresis. HDL subfractions were visualized by immunoblotting with 125I-labeled polyclonal antibodies against human apoAI. The autoradiograms shown are representative of five independent experiments.

 
We used immunoassays to follow the time course of changes in pre{beta}1-HDL concentrations during 37°C incubation. In the HD samples, pre{beta}1-HDL did not decrease, and levels were independent of the presence of DTNB (Figure 4, left panel). However, in the absence of DTNB, pre{beta}1-HDL decreased as a function of time for the control samples. When LCAT activity was blocked by DTNB, pre{beta}1-HDL did not decrease after 2 h (Figure 4, right panel). DRpre{beta}1was 68% lower for the HD group than for the control group (Figure 5, closed and open bars) and was reduced in the normal-HDL and low-HDL HD subgroups to similar extents (Figure 5, hatched bars). In all the subjects, DRpre{beta}1 had significant positive correlation with LCAT activity (Figure 6), whereas the baseline pre{beta}1-HDL level did not have significant correlation with LCAT activity (r = 0.06).



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  		Figure 4. Changes in plasma pre{beta}1-HDL concentrations during incubation at 37°C. Fresh plasma from the HD (left panel) and control groups (right panel) was incubated at 37°C for 120 min in the absence (filled circles) or presence (filled triangles) of 2 mM DTNB. Pre{beta}1-HDL concentrations were measured at five different points by immunoassay using a monoclonal antibody-specific for pre{beta}1-HDL.

 


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  		Figure 5. Comparisons of DRpre{beta}1. Fasting plasma was obtained from the HD (filled bar) and control (open bar) groups. HD patients were further divided into two subgroups (crosshatched bars); L-HDL (HDL-cholesterol < 1.03 mmol/L) and N-HDL (HDL-cholesterol >= 1.03 mmol/L). The plasma samples were incubated at 37°C for 120 min in the absence or presence of 2 mM DTNB, and the concentration of pre{beta}1-HDL in each sample was determined by immunoassay. The lecithin:cholesterol acyltransferase (LCAT)–dependent rate of decrease in pre{beta}1-HDL (DRpre{beta}1) was calculated as described in Materials and Methods.

 


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  		Figure 6. Correlation between DRpre{beta}1 and LCAT activity. Fasting plasma was obtained from the HD (filled circles) and control (open circles) groups. The plasma samples were incubated at 37°C for 120 min in the absence or presence of 2 mM DTNB, and the concentration of pre{beta}1-HDL in each sample was determined by immunoassay. The LCAT-dependent rate of decrease in pre{beta}1-HDL (DRpre{beta}1) was calculated as described in Materials and Methods. LCAT activity was measured by an exogenous substrate method.

 

   Discussion
Top
 Abstract
 Introduction
 Materials and Methods
 Results
 Discussion
References
 
The experiments presented here clearly show that LCAT-dependent conversion of pre{beta}1-HDL to {alpha}-migrating HDL is severely delayed in HD patients. The average pre{beta}1-HDL concentration was 127% higher for HD patients than for control subjects, and pre{beta}1-HDL levels did not decrease during 37°C incubation as a consequence of LCAT activity (Figures 3 to 5). In addition, DRpre{beta}1 correlated positively with LCAT activity (Figure 6). These findings are consistent with the earlier observations that "free apoAI" (14,15) increased in HD patients (14,15).

In HD patients, turnover of pre{beta}1-HDL is probably reduced by alterations in several metabolic steps. The first step is maturation of pre{beta}1-HDL into {alpha}-migrating HDL by LCAT. LCAT activity was reduced not only in the low-HDL subgroup (HD patients with low HDL-C levels) but also in the normal-HDL subgroup (HD patients with normal HDL-C levels), which constituted about half of the HD patients. In agreement with these findings, DRpre{beta}1 (the relative LCAT-dependent decrease in pre{beta}1-HDL after 37°C incubation) was significantly lower for both the low-HDL and normal-HDL HD subgroups than for the control group (Figure 5). The positive correlation between DRpre{beta}1 and LCAT activity confirms the importance of LCAT in reverse cholesterol transport (Figure 6).

It should be noted that the reduction in DRpre{beta}1 is apparently greater than the reduction in LCAT activity. The reductions in DRpre{beta}1 were about 70% for the low-HDL and normal-HDL HD subgroups (Figure 5), whereas the reductions in LCAT activity were only 41 and 30%, respectively. In an affinity chromatography study, the proportion of LCAT in apoAI-free plasma was found to be higher in patients with renal failure than in normolipidemic subjects (30). Because apoAI activates LCAT activity, such abnormal distribution of LCAT may partially explain the discrepancy in our results (Table 1; Figure 5). In a previous study, pre{beta}1-HDL concentrations were shown to be 38% higher in patients with angiographically proven coronary artery disease (CAD) than in control subjects (22). In the CAD patients, the increase in pre{beta}1-HDL was more evident in the low-LCAT activity subgroup than in the high-LCAT activity subgroup (22). These data strongly suggest that pre{beta}1-HDL levels may increase in some patients due to the delayed conversion of pre{beta}1-HDL to {alpha}-migrating HDL.

The second step is the excretion of pre{beta}1-HDL into urine at the kidneys. HD patients are usually unable to produce urine; thus glomerular filtration of pre{beta}1-HDL may be disabled in these patients. In experiments using rabbits, kidneys were shown to be responsible for 70% of apoAI and HDL catabolism (31). Pre{beta}1-HDL has an estimated mass of 60 to 70 kD (11,26), has small lipids in its core (cholesteryl ester and TG) (11), and has a smaller surface charge than {alpha}-migrating HDL (11,22–26). Theoretically, particles of 80 to 100 kD can pass through the glomerular filtration barrier (32). The discoid form and smaller surface charge of reconstituted apoAI-containing particles increase the clearance rate from plasma (33). Therefore, it is likely that pre{beta}1-HDL is preferably filtered in the glomeruli. According to a recent hypothesis, the filtered apoAI-containing particles may be taken up from the urine by cubilin (a high-affinity receptor for lipid-poor apoAI) on renal epithelial cells (34). The lack of access to this pathway in the HD patients probably increases pre{beta}1-HDL levels in plasma.

The third step is the hepatic lipase-mediated conversion of {alpha}-migrating HDL to pre{beta}1-HDL that is promoted by CETP. When HDL2 was perfused through a rat liver, pre{beta}1-HDL was newly generated in the perfusate at the expense of {alpha}-migrating HDL2 (35). This effect was enhanced when TG-enriched HDL2 was used. When hepatic lipase was depleted in the perfused liver, on the other hand, no pre{beta}1-HDL was newly generated from HDL2. In vitro, either partially purified hepatic lipase or bacterial TG lipase can generate pre{beta}1-HDL from HDL2 (26,35). CETP promotes a net mass transfer of cholesteryl ester from spherical HDL to TG-rich lipoproteins, and that of TG in the reverse direction. Cholesteryl ester transferred to TG-rich lipoproteins is finally transported to the liver. In transgenic mice expressing human apoAI and CETP, pre{beta}1-HDL levels increased significantly (36), probably because their HDL particles are more susceptible to hepatic lipase than those in control mice. In our previous study, high CETP amounts were associated with high pre{beta}1-HDL concentrations (24,25). These findings strongly suggest that pre{beta}1-HDL dissociates from {alpha}-migrating HDL during hydrolysis by hepatic lipase. In Japan, HD patients were found to have low levels and activity of hepatic lipase (4,5). In addition, CETP was significantly lower in HD patients than in control subjects (Table 1) (10). Thus, these abnormalities in HD patients delay the transport of cellular cholesterol to the liver.

In the present study, there is another marked difference in pre{beta}1-HDL metabolism between HD patients and control subjects. During 37°C incubation, pre{beta}1-HDL in HD patients increased steadily regardless of the presence of DTNB (Figure 4). Recent research suggests that such increase in pre{beta}-HDL is closely related to phospholipid transfer protein (PLTP) activity (37). In vitro, PLTP produces larger HDL2-like particles and pre{beta}1-HDL from smaller HDL3 (38,39). In HD group, the relative concentrations of the larger {alpha}-migrating HDL (HDL2b and HDL2a) did not decrease, whereas that of the smaller {alpha}-migrating HDL (HDL3) decreased significantly (Figure 2). These findings might imply that high PLTP activity compensates for low LCAT activity to maintain larger {alpha}-migrating HDL particles. Our incubation system did not have cell membranes; therefore the newly generated pre{beta}1-HDL could not derive from cellular cholesterol. The further studies are needed to elucidate the role of PLTP on pre{beta}1-HDL metabolism in HD patients.

Taken together, these results suggest that conversion between pre{beta}1-HDL and {alpha}-migrating HDL is likely to be impaired in both directions in HD patients, thus hampering reverse cholesterol transport. Other investigators showed that atherosclerosis in HD patients is not necessarily correlated with HDL-C but with other lipoproteins or regulators for HDL metabolism (6,40,41). These previous observations, combined with the present data, may indicate that HDL metabolism is more important than HDL-C concentration in end-stage renal disease. In conclusion, LCAT-dependent conversion of pre{beta}1-HDL is severely delayed in HD patients. We speculate that abnormal metabolism of pre{beta}1-HDL may partially explain the predisposition of HD patients to CVD.


   Acknowledgments
 
This study was supported by a Grant-in-Aid for Science Research from the Ministry of Education, Science, and Culture of Japan (No. 12671102, 2000–2002). We are deeply indebted to Takako Igarashi, Yoko Honda, and Utako Seino for their excellent technical assistance.


   References
Top
 Abstract
 Introduction
 Materials and Methods
 Results
 Discussion
 References
 

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Received for publication August 30, 2002. Accepted for publication October 22, 2002.




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