Lipoprotein(a) in patients treated by continuous ambulatory peritoneal dialysis

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.

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.

Is Atherosclerosis Accelerated by Capd?

Cardiovascular complications in renal replacement therapy remain prevalent today. The question, “Is atherosclerosis accelerated in peritoneal dialysis (PD) patients,” has not been resolved. Many cross-sectional studies have revealed that there are more atherogenic lipid profiles in continuous ambulatory peritoneal dialysis (CAPD) than in other dialytic modalities. However, it is not certain that CAPD per se may contribute to lipid abnormalities in continuing PD for a long time. Therefore, we tried to assess whether CAPD itself may change lipid profiles in the long-term period on CAPD.

We measured conventional lipid profiles in 16 stable CAPD patients in whom total cholesterol (T. chol.) levels remained under 240 mg/dL at the time of starting observation. Diabetic end-stage renal disease (DMESRD) patients were excluded from this study. Blood sampling was performed under strict conditions indicating overnight fasting with 10 hours dwell of 2 L of 1.5% Dianeal. Plasma levels of T. chol., triglyceride, high-density lipoprotein (HDL), low-density lipoprotein (LDL), and atherogenic lipoprotein (apo B/A-I) did not show significant changes by serial measurements from the sixth month to the thirtieth month following the commencement of CAPD as their initial dialysis treatment.

Recently it is reported that high plasma levels of Lp(a) lipoprotein are an independent risk factor in cardiovascular events in renal replacement therapy because Lp(a) has a close relation to intravascular thrombosis and acceleration of atherosclerosis. We found that the incidence of vascular accidents was five episodes among 33 patients with higher (>31 mg/dL) Lp(a) levels, while there was only one episode in 45 patients with lower «30 mg/dL) Lp(a) levels (p < 0.05, odds ratio: 7.9). However, severity of aortic calcification and incidence of positive treadmill test showed no difference in these two groups. No significant correlation was observed between duration on CAPD and plasma Lp(a) levels. From the fact mentioned above, we speculate that CAPD does not essentially affect lipid profiles if determined under the strict condition of blood sampling.

In order to evaluate atherosclerosis noninvasively, we have measured aortic pulse wave velocity (AoPWV) in 33 stable CAPD patients excluding those with DMESRD by two years’ interval. Fifteen cases (46%) increased in AoPWV, however, lipid profiles did not differ from those of nonadvanced patients.

Calcification of arteries is further evidence of acceleration in atherosclerotic change. Therefore, we have graded severity of abdominal aortic calcification into three categories: grade I denoted nil calcification, grade II denoted patchy calcification, and grade III denoted calcification along the entire abdominal wall, having a lead-pipe shape by lateral view of plain abdominal x-ray film. There were significant differences in the duration of CAPD (grade I: 41 months, grade II: 60 months, grade III: 68 months). AoPWV showed least in the grade I group, faster in grade II, and fastest in grade III, while lipid profiles did not show significant difference in three categories.

From the analysis of serial changes of lipid profiles, AoPWV and aortic calcification, CAPD may present some risk of accelerating atherosclerosis, at least in some patients on long-term treatment. Risk factors contributing to acceleration of atherosclerosis result not from lipid abnormalities, but from other factors which remained to be seen, for example, abnormalities in calcium metabolism.

ApoA- and apoB-containing lipoproteins and Lp(a) concentration in non-dialyzed patients with chronic renal failure

BACKGROUND

End-Stage renal disease is associated with accelerated atherosclerosis and a high incidence of cardiovascular disease.

METHODS

The serum levels of lipids and apolipoproteins and Lp(a) were determined in 51 patients with chronic renal failure (CRF) with various advancement, without interference of factors which might disturb Lp(a) metabolism and with proteinuria less than 0.5 g/24 h. The patients studied were divided into two groups: patients with moderate renal failure (CRF-M) and creatinine levels of 2-6mg/dL n = 27; and predialysis patients with end stage renal disease (ESRD) and creatinine levels higher than 8.5 mg/dL n=24.

RESULTS

In both studied groups serum concentrations of triglycerides (TG), total apoCIII, apoCIIInonB, apoB:CIII were statistically increased, (except total cholestrol (TC) and LDL-cholestrol (LDL-C), apoB, total apoE, apoEnonB, apoB:E), while the levels of HDL-cholestrol (HDL-C) and apoAl significantly decreased. Lipid and lipoprotein ratios as risk factors of atherosclerosis were similar in both groups. The TC/HDL-C ratio increased, while that of HDL-C/ apoAI and apoAI/apoCIII decreased. Serum Lp(a) concentrations were significantly increased in both studied groups. The medians and ranges of Lp(a) concentration were similar in both groups. Serum Lp(a) levels correlated with total cholesterol (r=0.295; p < 0.05), LDL-C (r = 0.312; p < 0.05) and apoB (r = 0.215; p < 0.05). In addition, no correlation was found between Lp(a) levels and albumin concentrations (r = 0.126; p = 0.421).

CONCLUSION

Our results may indicate that the reduced levels of apoA-containing lipoproteins and increased TG-rich apoB-containing lipoproteins and Lp(a) indicated a clear atherogenic pattern in early renal disease. Increased Lp(a) concentration may result in nonspecific synthesis or catabolism disturbances. Measurement and monitoring of lipoprotein family profiles offers a new means for selecting appropriate therapies targeted for normalizing dyslipidemia in non-dialyzed patients.

Atherothrombogenicity of lipoprotein(a): the debate

Although lipoprotein(a) (Lp[a]) has been recognized as an atherothrombogenic factor, the underlying mechanisms for this pathogenicity have not been clearly defined. Plasma levels have received most of the attention in this regard; however, discrepancies among population studies have surfaced. Particularly limited is the information on the fate of Lp(a) that enters the arterial wall, in terms of mechanisms of endothelial transport and interactions with cells and macromolecules of the extracellular matrix. A typical Lp(a) represents a low-density lipoprotein (LDL)-like particle having as a protein moiety apo B-100 linked by a single interchain disulfide bond to a unique multikringle glycoprotein, called apolipoprotein(a) (apo[a]). In vitro studies have shown that Lp(a) can be dissected into its constituents, LDL and apo(a). In turn, the latter can be cleaved by enzymes of the elastase and metalloproteinase families into fragments that exhibit a differential behavior in terms of binding to macromolecules of the extracellular matrix: fibrinogen, fibronectin, and proteoglycans. By immunochemical criteria, apo(a) predominantly localizes in areas of human arteries affected by the atherosclerotic process, where elastase and metalloproteinase enzymes operate and where apo(a) fragments are potentially generated. The accumulation of these fragments in the vessel wall is likely to depend on their affinity for the constituents of the extracellular matrix. Thus, factors that modulate inflammation and inflammation-mediated fragmentation of Lp(a)/apo(a) may play an important role in the cardiovascular pathogenicity of Lp(a). This pathogenicity may be attenuated by measures directed at preventing the activation of those vascular cells that secrete enzymes with a proteolytic potential for Lp(a)/apo(a), namely, leukocytes, macrophages, and T cells.

Chimpanzee lipoprotein(A): Relationship between apolipoprotein(A) isoform size and the density profile of lipoprotein(A) in animals with different heterozygous apo(A) phenotypes

In a previous study [C. Doucet et al., J. Lipid Res 35:263-270, 1994], we have shown that plasma lipoprotein (a) [Lp(a)] levels were significantly elevated in a population of unrelated chimpanzees as compared to those in normolipidemic human subjects. Nonetheless, the inverse correlation between Lp(a) levels and apolipoprotein (a) [apo(a)] isoforms typical of man was maintained in the chimpanzee. In the present study, we describe the density profiles of apo B- and apo A1-containing lipoproteins and of Lp(a) in chimpanzee plasmas heterozygous for apo(a) isoforms after fractionation by single spin ultracentrifugation in an isopycnic gradient. The distribution of apo(a) isoforms in the density gradient was also examined by SDS-agarose gel electrophoresis and immunoblotting using chemiluminescence detection. In all double-band phenotypes examined, the smallest isoform was present along the entire length of the density gradient. The density distribution of the second isoform varied according to the size difference between the respective isoforms. Two isoforms close in size (difference in apparent molecular mass = 60 kDa) were present together in every gradient subfraction. On the contrary, when the two isoforms displayed distinct molecular mass (maximal difference in apparent molecular mass = 340 kDa), then the largest was principally present in the densest fractions of the gradient (d > 1.1 mg/ml). These observations suggest that Lp(a) particles with small apo(a) isoforms are more susceptible to interact with other lipoproteins than are Lp(a) particles with large isoforms.

Cardiac disease in chronic uremia: clinical outcome and risk factors

Cardiac disease is common and is the major killer in end-stage renal disease (ESRD). Cardiac failure is a highly malignant condition in ESRD patients. Cardiac failure mediates most of the adverse prognostic impact of ischemic heart disease. Left ventricular (LV) abnormalities are already present at initiation of dialysis therapy in approximately 80% of patients. These abnormalities (ie, systolic dysfunction in approximately 15%, LV dilatation with preserved systolic function in 30%, concentric LV hypertrophy [LVH] in 40%) independently predict ischemic heart disease and cardiac failure, and are the largest baseline predictor of mortality after 2 years on dialysis therapy. The associations between classical risk factors (eg, hyperlipidemia, smoking, hypertension) and cardiac outcomes in ESRD are inconsistent. "Uremic" risk factors represent a nascent, but potentially important field. In our prospective 10-year study of 433 patients starting renal replacement therapy, we identified the following as major independent risk factors for cardiac disease: (1) hypertension (concentric LVH, LV dilatation, ischemic heart disease, cardiac failure, inverse relationship with mortality); (2) anemia (LV dilatation, cardiac failure, death); and (3) hypoalbuminemia (ischemic heart disease, cardiac failure, death). Transplantation dramatically improved LV abnormalities, suggesting that a uremic environment is cardiotoxic. Multiple risk factors act in concert to produce cardiac disease in ESRD; many of these are avoidable, suggesting that the enormous burden of disease can be reduced considerably.

Decrease in lipoprotein(a) after renal transplantation is related to the glucocorticoid dose

Serum lipoprotein(a) [Lp(a)] concentrations and apolipoprotein(a) phenotypes were determined in 46 patients with end-stage renal disease both before as well as 1 week and 1, 3 and 6 months after renal transplantation. Immunosuppressive therapy consisted of cyclosporin A, prednisone and azathioprine. Before transplantation median Lp(a) levels did not differ between the patients and a healthy control group. A highly significant decrease (P < 0.001) in Lp(a) levels was observed in both male and female patients 1 week after transplantation. This marked reduction in Lp(a) occurred at a time when patients were receiving the highest doses of corticosteroids. As steroid doses were gradually tapered, Lp(a) concentrations subsequently increased, although at 6 months levels were still significantly reduced (P < 0.01) in women. No significant correlation was observed between Lp(a) and whole-blood cyclosporin levels, nor was there any correlation with the azathioprine dose. The reduction in Lp(a) concentrations was seen for all apo(a) phenotypes observed in the study.

Factors influencing plasma lipid profiles including lipoprotein (a) concentrations in renal transplant recipients

Fasting plasma cholesterol, triglycerides, high-density lipoprotein (HDL) and apoprotein (apo) B were elevated in 214 nondiabetic renal transplant recipients when compared to a reference group. Apo (a) was slightly but not significantly lower in transplant recipients (median 118 mg/dl, range 16-1680 vs 130 mg/dl, 10-1176) and this difference could be predicted from Lp (a) isoform analysis. Cholesterol, triglyceride, apo B and apo (a) concentrations correlated negatively with creatinine clearance but none of these parameters showed a significant association with proteinuria. Patients treated with steroids had higher plasma HDL concentrations than those receiving cyclosporin monotherapy (P < 0.01). The use of diuretics was associated with raised triglycerides (P < 0.001) and cholesterol (P < 0.01) and with reduced HDL (P < 0.01) whilst patients receiving beta-blockers had significantly higher triglycerides (P < 0.01) and lower HDL levels (P < 0.02). In multiple regression analysis, age (P < 0.01), creatinine clearance (P < 0.05) and diuretic therapy (P < 0.005) were independent risk factors for increased cholesterol whilst apo (a) levels correlated negatively with creatinine clearance (P < 0.005). These results suggest that impaired renal function, steroids and non-immunosuppressive drugs contribute to lipid abnormalites in renal transplant recipients.

Levels of lipoprotein(a), apolipoprotein B, and lipoprotein cholesterol distribution in IDDM. Results from follow-up in the Diabetes Control and Complications Trial

Levels of lipoprotein(a) [Lp(a)], apolipoprotein (apo) B, and lipoprotein cholesterol distribution using density-gradient ultracentrifugation were measured as part of a cross-sectional study at the final follow-up examination (mean 6.2 years) in the Diabetes Control and Complications Trial. Compared with the subjects in the conventionally treated group (n = 680), those subjects receiving intensive diabetes therapy (n = 667) had a lower level of Lp(a) (Caucasian subjects only, median 10.7 vs 12.5 mg/dl, respectively; P = 0.03), lower apo B (mean 83 vs. 86 mg/dl, respectively; P = 0.01), and a more favorable distribution of cholesterol in the lipoprotein fractions as measured by density-gradient ultracentrifugation with less cholesterol in the very-low-density lipoprotein and the dense low-density lipoprotein fractions and greater cholesterol content of the more buoyant low-density lipoprotein. Compared with a nondiabetic Caucasian control group (n = 2,158), Lp(a) levels were not different in the intensive treatment group (median 9.6 vs. 10.7 mg/dl, respectively; NS) and higher in the conventional treatment group (9.6 vs. 12.5 mg/dl, respectively; P < 0.01). No effect of renal dysfunction as measured by increasing albuminuria or reduced creatinine clearance on Lp(a) levels could be demonstrated in the diabetic subjects. Prospective follow-up of these subjects will determine whether these favorable lipoprotein differences in the intensive treatment group persist and whether they influence the onset of atherosclerosis in insulin-dependent diabetes.

Association of elevated lipoprotein(a) levels and coronary heart disease in NIDDM patients. Relationship with apolipoprotein(a) phenotypes

Non-insulin-dependent diabetes mellitus (NIDDM) is a strong and independent risk factor for coronary heart disease. We assessed the potential relationship between plasma Lp(a) levels, apo(a) phenotypes and coronary heart disease in a population of NIDDM patients. Seventy-one patients with coronary heart disease, who previously have had transmural myocardial infarction, or significant stenosis on coronary angiography, or positive myocardial thallium scintigraphy, or in combination, were compared with 67 patients without coronary heart disease, who tested negatively upon either coronary angiography, myocardial thallium scintigraphy or a maximal exercise test. The prevalence of plasma Lp(a) levels elevated above the threshold for increased cardiovascular risk (> 0.30 g/l) was significantly higher (p = 0.005) in patients with coronary heart disease (33.8%) compared to the control group (13.4%). The relative risk (odds ratio) of coronary heart disease among patients with high Lp(a) concentrations was 3.1 (95% confidence interval, 1.31-7.34; p = 0.01). The overall frequency distribution of apo(a) phenotypes differed significantly between the two groups (p = 0.043). However, the frequency of apo(a) isoforms of low apparent molecular mass (< or = 700 kDa) was of borderline significance (p = 0.067) between patients with or without coronary heart disease (29.6% and 16.4%, respectively). In this Caucasian population of NIDDM patients, elevated Lp(a) levels were associated with coronary heart disease, an association which was partially accounted for by the higher frequency of apo(a) isoforms of small size. In multivariate analyses, elevated levels of Lp(a) were independently associated with coronary heart disease (odds ratio 3.48, p = 0.0233).

Lipid parameters including Lp(a) in hemodialysis patients

Chronic hemodialysis (CHD) patients have a high incidence and prevalence of atherosclerotic disease which may be related to numerous atherosclerotic risk factors. Among them dyslipidemia plays a significant role. Elevated Lp(a) levels, which are strongly associated with atherosclerosis, have been reported recently in uremic patients. The aim of our study was the determination of the levels of lipid parameters including Lp(a) in 151 CHD patients (76 male) aged 57 (12-81) years, who were on hemodialysis for a mean of 44.3 (range 1 to 189) months. Eighty-four normal individuals age and sex matched were used as controls. The median serum Lp(a) concentration in hemodialysis patients was 13 mg/dL compared with 6.5 mg/dL in healthy controls, p < 0.001 by distribution-free Mann-Whitney test. The prevalence of subjects with Lp(a) levels above 25 mg/dL was significantly higher in CHD patients compared to normal subjects (30% vs. 8%, p < 0.001). Even if CHD patients were matched for fasting lipid levels, they showed Lp(a) levels significantly higher than controls. No significant correlation was found between Lp(a) levels and either the age of the patients or the duration of hemodialysis. The etiology of primary renal disease did not influence the Lp(a) levels.

Low-density lipoprotein immunofluorescence at the site of renal injury in glomerulosclerosis: a potential pathogenetic role for lipids in renal disease

The role of lipids in the genesis of renal disease has received increased attention. We describe the presence of anti-low-density lipoprotein immunofluorescence at the site of renal injury found by light microscopy. This may offer immunohistologic evidence for a potential role of this atherogenic lipid in the genesis of renal disease and glomerulosclerosis. Furthermore, we describe the contribution of cholesterol in early renal disease and markers for malnutrition in the dialytic management of end-stage renal disease. Interventional strategies, including vasoactive agents present and future, are presented.