Atherogenic lipoprotein changes in the absence of hyperlipidemia in patients with chronic renal failure treated by hemodialysis

Cardiovascular disease and chronic kidney disease: insights and an update

Despite the high prevalence and significant morbidity and mortality rates of chronic kidney disease (CKD) related to cardiovascular disease, it remains vastly understudied. Most of the current practice recommendations come from small under-powered prospective studies, retrospective reviews, and assuming patients with CKD will similarly benefit from medications and treatments as patients with normal renal function. In addition, because of the previous lack of a consistent definition of CKD and how to measure renal function, definitions of the degree of renal dysfunction have varied widely and compounded the confusion of these data. Remarkably, despite patients with CKD representing the group at highest risk from cardiovascular complications, even greater than patients with diabetes mellitus, there has been a systematic exclusion of patients with CKD from therapeutic trials. This review outlines our current understanding of CKD as a cardiovascular risk factor, treatment options, and the future directions that are needed to treat cardiovascular disease in patients with CKD.

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.

Effect of diabetes on uremic dyslipidemia

Elevated intermediate-density lipoprotein (IDL), a remnant lipoprotein, is an independent risk factor for atherosclerosis in patients with end-stage renal disease (ESRD). Since the presence of diabetes mellitus further increases the risk of cardiovascular mortality in ESRD, we examined the effect of diabetes on IDL among ESRD patients. The subjects were 330 healthy control subjects and 287 patients with end-stage renal disease including 80 patients with type 2 diabetes. As compared with the healthy subjects, the nondiabetic ESRD patients had increased plasma triglyceride and IDL cholesterol. Diabetic patients with ESRD showed a further increase in plasma triglyceride and IDL cholesterol compared with the nondiabetic group. However, the difference in IDL levels between the ESRD groups was no longer significant when subjects were stratified by plasma triglyceride. Plasma triglyceride was correlated with IDL cholesterol. Increased hemoglobin A(1c) was significantly associated with IDL cholesterol in a multiple regression model including age, gender, and the presence of ESRD. Such an association was no longer significant in another model including plasma triglyceride as an additional covariate. Further analysis indicated the positive effects of diabetes and hyperglycemia on plasma triglyceride. These results indicate that increased IDL in ESRD is further deteriorated in the presence of diabetes, and that the adverse effect is accounted for at least partly by hypertriglyceridemia associated with chronic hyperglycemia.

Management of selected lipid abnormalities: hypertriglyceridemia, isolated low HDL-cholesterol, lipoprotein(a), and lipid abnormalities in renal diseases and following solid organ transplantation

Although the focus in treating lipid disorders is on reducing LDL-C levels, additional lipid-related independent risk factors, such as TG, HDL-C, and Lp(a) levels, should be used clinically to assess cardiovascular risk. Decisions to initiate drug therapy for LDL-C reduction may be influenced by levels of these other lipoprotein fractions. Data supporting intervention to modify these factors are less abundant than for LDL-C reduction, but in certain circumstances. drug therapy targeted at TGs or HDL-C may be appropriate. Patients who have nephrotic syndrome and end-stage renal disease are at particularly high risk for the development of CVD and should be treated aggressively for their lipid disorders. Finally, solid organ transplant recipients are almost always hyperlipidemic and appropriate therapy could reduce cardiovascular events.

Are HMG-CoA reductase inhibitors underutilized in dialysis patients?

Patients with end-stage renal disease (ESRD) treated with dialysis have a dramatically elevated rate of cardiovascular disease (CVD) compared to the general population. Lipid-lowering therapy with 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase inhibitors ("statins") has been shown to markedly reduce cardiovascular risk in patients without renal failure, but their effect has not been fully studied in the dialysis population. In this article we will first discuss the known benefits of statin therapy in the general population and summarize the current guidelines for such therapy. We will then examine the evidence linking dyslipidemia and cardiac disease in the dialysis population and discuss possible pathophysiologic mechanisms by which statins could prevent cardiac disease in these patients. We will also review prior clinical studies of the effects of statins in patients on dialysis, with particular attention to the safety and efficacy of these drugs in this population. Finally, we will review how statins are currently being used in the care of dialysis patients and suggest whether an expanded utilization of these drugs could help reduce the enormously high rates of cardiac disease in this patient population.

Dialysis modalities and dyslipidemia

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

Why do we need a statin trial in hemodialysis patients?

BACKGROUND

The risk of cardiovascular complications is markedly increased in patients on dialysis treatment. This includes cardiac disease, stroke, and peripheral vascular disease. The mortality in dialysis patients is markedly higher compared to a nonuremic population. There are several cardiovascular (CV) risk factors that are unique to this population, one of which is dyslipidemia. Uremic patients do not usually develop hypercholesterolemia, but rather are characterized by high levels of very low density lipoprotein (VLDL) triglycerides, low high density lipoprotein (HDL) cholesterol, and elevated levels of modified low density lipoprotein (LDL) particles, which are particularly harmful to the vascular wall. HMG-CoA reductase inhibitors (statins) have been proven to be very efficient in reducing CV events in a nonrenal population. There are several landmark trials that have demonstrated that statins reduce the mortality in cardiovascular disease (CVD) in populations with normal, or close to normal, renal function. There are some observational registry data indicating that this may also be true in hemodialysis (HD) patients, but no prospective controlled trial has been performed to date.

METHODS

We present the rationale for, and a brief outline of, a randomized placebo-controlled trial using a novel drug, rosuvastatin, in HD patients, to target cardiovascular events (the AURORA study). This study will include close to 3000 male and female HD patients, aged 50-80 years. The study is event driven and it has been estimated that it will run for a follow-up time close to four years.

CONCLUSION

There is a sound rationale for making a randomized placebo-controlled statin trial in HD patients, with the objective to demonstrate an effect on CV mortality and morbidity.

Thrombosis in end-stage renal disease

Although renal failure has classically been associated with a bleeding tendency, thrombotic events are common among patients with end-stage renal disease (ESRD). A variety of thrombosis-favoring hematologic alterations have been demonstrated in these patients. In addition, "nontraditional" risk factors for thrombosis, such as hyperhomocysteinemia, endothelial dysfunction, inflammation, and malnutrition, are present in a significant proportion of chronic dialysis patients. Hemodialysis (HD) vascular access thrombosis, ischemic heart disease, and renal allograft thrombosis are well-recognized complications in these patients. Deep venous thrombosis and pulmonary embolism are viewed as rare in chronic dialysis patients, but recent studies suggest that this perception should be reconsidered. Several ESRD treatment factors such as recombinant erythropoietin (EPO) administration, dialyzer bioincompatibility, and calcineurin inhibitor administration may have prothrombotic effects. In this article we review the pathogenesis and clinical manifestations of thrombosis in ESRD and evaluate the evidence that chronic renal failure or its management predisposes to thrombotic events.

Intima-media thickness of carotid artery predicts cardiovascular mortality in hemodialysis patients

BACKGROUND

Cardiovascular disease is the leading cause of death in patients with end-stage renal disease (ESRD). Previous studies showed that patients with ESRD had increased intima-media thickness of the carotid artery (CA-IMT). In the present study, we examined whether CA-IMT would predict cardiovascular mortality in patients with ESRD.

METHODS

The cohort consisted of 438 patients with ESRD treated with hemodialysis. CA-IMT was measured by high-resolution B-mode ultrasonography.

RESULTS

During the follow-up period of 30 months, 82 deaths, including 44 cardiovascular fatal events, occurred. Compared with those with CA-IMT less than 1.0 mm, those with moderately increased CA-IMT (1.0 to 2.0 mm) and those with severely increased CA-IMT (>or=2.0 mm) showed a significantly greater risk for death from cardiovascular causes; odds ratios were 3.17 (95% confidence interval [CI], 1.41 to 7.17; P = 0.005) and 10.20 (95% CI, 3.67 to 28.3; P < 0.0001), respectively, in a multivariate Cox analysis including age, sex, duration of hemodialysis therapy, presence of diabetes mellitus, blood pressure, body mass index, and high-density lipoprotein and non-high-density lipoprotein cholesterol levels as covariates. Conversely, CA-IMT was not significantly associated with noncardiovascular mortality.

CONCLUSION

These results indicate that increased CA-IMT is an independent predictor of cardiovascular mortality in the hemodialysis population.

Lipoprotein alterations in hemodialysis: differences between diabetic and nondiabetic patients

Both renal failure and type 2 diabetes may contribute synergistically to the dyslipemia of diabetic renal failure with the development of atherosclerosis as the possible consequence. It has not yet been conclusively evaluated whether diabetic patients with end-stage renal failure under maintenance hemodialysis (HD) show accentuated alterations in plasma lipids and lipoproteins in comparison to nondiabetics under HD. These abnormalities would involve hepatic lipase activity and the regulation of triglyceride-rich lipoprotein metabolism. The purpose of the present study was to evaluate whether type 2 diabetic patients undergoing HD exhibited a lipid-lipoprotein profile different from that of nondiabetic hemodialyzed patients. We compared plasma lipids, apoprotein (apo) A-I and B, and lipoprotein parameters among 3 groups: 25 type 2 diabetics, 25 nondiabetics, both undergoing HD, and 20 healthy control subjects. Intermediate-density lipoprotein (IDL) and low-density lipoprotein (LDL) were isolated by sequential ultracentrifugation. Hepatic lipase activity was measured in postheparin plasma. Both groups of HD patients showed higher triglyceride and IDL cholesterol (P <.001), and lower high-density lipoprotein (HDL) cholesterol (P <.01) and apo A-I (P <.001) levels compared to the control group, even after adjustment for age and body mass index (BMI). However, no differences were found in lipid, lipoprotein, and apoprotein concentrations between diabetic and nondiabetic HD patients, except for high LDL triglyceride content of diabetic HD patients (P <.01). Nondiabetics undergoing HD also presented higher LDL triglyceride levels than controls (P <.05). LDL triglyceride correlated with plasma triglycerides (r = 0.51, P <.001). A lower LDL cholesterol/apo B ratio was found in each group of HD patients in comparison to controls (P <.02). Comparing the diabetic and nondiabetic patients, hepatic lipase activity remained unchanged, but significantly lower than control subjects (P <.001). Hepatic lipase correlated with log-triglyceride (r = -0.31, P <.01), IDL cholesterol (r = -0.41, P <.001), and LDL triglyceride (r = -0.32, P <.01). In conclusion, both diabetic and nondiabetic HD patients shared unfavorable alterations in lipid-lipoprotein profile not different between them but different from a healthy control group. The only difference between the groups of HD patients was a significant LDL triglyceride enrichment, which correlated negatively with hepatic lipase activity. Lipoprotein abnormalities in HD patients would enhance their risk for the development of atherosclerosis.

Prognostic implications of abnormalities in renal function in patients with acute coronary syndromes

BACKGROUND

Outcomes in patients with mild to moderate renal function (RF) abnormalities presenting with acute coronary syndromes (ACS) are not well defined.

METHODS AND RESULTS

A convenience sample of 4 ACS trial databases including all enrolled patients was assessed to determine 30- and 180-day outcomes. The 4 trials were Global Use of Strategies to Open Occluded Coronary Arteries (GUSTO) IIb, GUSTO-III, Platelet Glycoprotein IIb/IIIa in Unstable Angina: Receptor Suppression Using Integrilin Therapy (PURSUIT), and Platelet IIb/IIIa Antagonism for the Reduction of Acute coronary syndrome events in a Global Organization Network (PARAGON-A). Patients were stratified into ST-segment elevation (STE) and non-ST-segment elevation (NSE) groups and by the presence or absence of abnormal RF (creatinine clearance <70 mL/min). In the STE group, 7670 of 18 621 patients (41%) had abnormal RF. In the NSE group, 8152 of 19 304 (42%) had abnormal RF. Patients with abnormal RF were older, more often female, and more likely to have adverse baseline characteristics. They had higher mortality and higher mortality/nonfatal myocardial infarction (MI) at both 30 and 180 days, regardless of ST-segment status. Creatinine clearance was independently associated with risk of mortality (hazard ratio 0.79 in the STE group and 0.81 in the NSE group) and with risk of mortality/MI (hazard ratio 0.93) in the NSE group at 180 days.

CONCLUSIONS

Patients presenting with ACS frequently have abnormal RF. Abnormal RF is a marker of adverse baseline clinical characteristics and is independently associated with increased risk of death and death/MI.

Impaired secretion of parathyroid hormone, but not refractoriness of osteoblast, is a major mechanism of low bone turnover in hemodialyzed patients with diabetes mellitus

Diabetic bone disease is characterized by low bone turnover resulting from either impaired secretion of parathyroid hormone (PTH) or refractoriness of osteoblasts to PTH. The present study was performed to elucidate which factor contributes more to the reduction in bone turnover by comparison between 64 hemodialyzed patients with diabetes mellitus and 106 hemodialyzed patients without diabetes mellitus. Only men were enrolled to avoid the influence of the menstrual cycle on bone metabolism. Serum intact PTH (iPTH) levels were significantly lower in hemodialyzed patients with diabetes than those without diabetes, although no significant difference existed in age, duration of hemodialysis therapy, or serum calcium or phosphate levels. Of the biochemical markers measured, serum intact osteocalcin (iOC) and deoxypyridinoline levels were significantly lower in patients with diabetes, although serum bone-specific alkaline phosphatase (BAP) and pyridinoline levels did not differ significantly between the two groups of patients. When patients were restricted to those with serum iPTH levels greater than 180 pg/mL, this parameter correlated significantly in a positive manner with both serum iOC and BAP levels and negatively with bone mineral density at distal radius 1/3. Regression slopes between iPTH levels and these parameters were not significantly different between the two groups of patients, indicating the absence of refractoriness of bone to PTH in patients with diabetes. In conclusion, our findings suggest that impaired PTH secretion, but not refractoriness of osteoblasts to PTH, may be responsible for the low bone turnover in hemodialyzed patients with diabetes.

Hypocholesterolemia is a significant predictor of death in a cohort of chronic hemodialysis patients

BACKGROUND

Although hypocholesterolemia is common in chronic hemodialysis patients, its effect on survival has not been studied in a large patients population.

METHODS

A cohort of chronic hemodialysis patients (N = 1167) was prospectively followed from January 1991 to January 2001. The survival impact of this cohort, who were divided according to different baseline levels of serum cholesterol, were calculated with the multivariate Cox proportional hazard analysis after adjusting for baseline clinical and laboratory variables.

RESULTS

During the study period, 567 (48.6%) patients died. The mean (SD) baseline level of serum cholesterol was 171.0 (40.8) mg/dL and ranged from 76 to 378 mg/dL. The five-year survival rate was highest (0.812) in the subgroup that had a serum cholesterol range of 200 to 219 mg/dL and was lowest (0.608) in the subgroup with serum cholesterol values of <140 mg/dL. The five-year survival rate was 0.735 in the subgroup with serum cholesterol of > or =220 mg/dL. Serum cholesterol was a significant predictor of death with an adjusted hazards ratio (95% confidence interval) was 0.939 (0.891 to 0.989). In a subgroup of patients with serum albumin values > or =4.5 g/dL (N = 128), the adjusted hazards ratio was even greater at 1.370 (1.105 to 1.692). Other than sex, body mass index and serum albumin were significant determinants of baseline levels of serum cholesterol.

CONCLUSIONS

Hypocholesterolemia was an independent predictor of death in patients on chronic hemodialysis. This impact of hypercholesterolemia on survival was only evident in a subgroup of patients whose serum albumin was more than 4.5 g/dL.

The impact of renal insufficiency on clinical outcomes in patients undergoing percutaneous coronary interventions

OBJECTIVES

We sought to determine the effect of varying degrees of renal insufficiency on death and cardiac events during and after a percutaneous coronary intervention (PCI).

BACKGROUND

Patients with end-stage renal disease have a high mortality from coronary artery disease. Little is known about the impact of mild and moderate renal insufficiency on clinical outcomes after PCI.

METHODS

Cardiac mortality and all-cause mortality were determined for 5,327 patients undergoing PCI from January 1, 1994, to August 31, 1999, at the Mayo Clinic, based on the estimated creatinine clearance or whether the patient was on dialysis.

RESULTS

In-hospital mortality was significantly associated with renal insufficiency (p = 0.001). Even after successful PCI, one-year mortality was 1.5% when the creatinine clearance was > or =70 ml/min (n = 2,558), 3.6% when it was 50 to 69 ml/min (n = 1,458), 7.8% when it was 30 to 49 ml/min (n = 828) and 18.3% when it was < 30 ml/min (n = 141). The 18.3% mortality rate for the group with < 30 ml/min creatinine clearance was similar to the 19.9% mortality rate in patients on dialysis (n = 46). The mortality risk was largely independent of all other factors.

CONCLUSIONS

Renal insufficiency is a strong predictor of death and subsequent cardiac events in a dose-dependent fashion during and after PCI. Patients with renal insufficiency have more baseline cardiovascular risk factors, but renal insufficiency is associated with an increased risk of death and other adverse cardiovascular events, independent of all other measured variables.

HMG-CoA reductase inhibitors are associated with reduced mortality in ESRD patients

BACKGROUND.: Patients with end-stage renal disease (ESRD) suffer from markedly higher rates of cardiovascular disease than the general population. Although therapy with 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase inhibitors ("statins") has been demonstrated to reduce the mortality from cardiovascular disease in patients without ESRD, only 10% of patients on dialysis are treated with these medications by day 60 of ESRD. We determined whether the use of statins is associated with a reduction in cardiovascular-specific death and total mortality in ESRD patients.

METHODS

Data were analyzed from the U.S. Renal Data System Dialysis Morbidity and Mortality Wave-2 study, a cohort of randomly selected patients who were initiating dialysis in 1996. Information about the use of statins as well as other baseline characteristics was abstracted from the patients' dialysis records by dialysis personnel. Cox proportional hazards models were developed to determine the association between use of statins at baseline and subsequent risk of mortality, with adjustment for known mortality risk factors.

RESULTS

Follow-up data were available for 3716 patients through July 1998. At baseline, 362 (9.7%) of patients were using statins. These patients had a mortality rate of 143/1000 person-years, compared with a rate of 202/1000 person-years for patients not using statins. Statin use was independently associated with a reduced risk of total mortality [relative risk (RR)=0.68, 95% confidence interval (CI)=0.54, 0.87] as well as cardiovascular-specific mortality (RR=0.64, 95% CI=0.45, 0.91). In contrast, the use of fibrates was not associated with reduced mortality (RR=1.29).

CONCLUSIONS

Statin use was associated with a reduction in cardiovascular-specific death and total mortality in patients on dialysis.

Atherogenic lipoproteins in end-stage renal disease

Cardiovascular mortality is substantially higher in patients with end-stage renal disease (ESRD). Lipoprotein abnormality in ESRD is one of the possible risk factors for advanced atherosclerosis. Uremic dyslipidemia is characterized by increased plasma triglycerides due to elevated very low density lipoprotein (VLDL) and decreased high-density lipoprotein (HDL). Plasma total or low-density lipoprotein (LDL) cholesterol is rarely elevated in hemodialysis patients. The "LDL" by standard assay methods consists of intermediate-density lipoprotein (IDL) and LDL devoid of IDL. Although "LDL" is not increased, IDL is markedly elevated in uremic plasma. We previously showed that aortic stiffness of hemodialysis patients was associated positively with VLDL, IDL, and LDL devoid of IDL and that IDL is the best lipoprotein predictor of aortic stiffness. The IDL level is correlated positively with plasma total cholesterol, triglyceride, and "LDL" levels. Importantly, increased IDL is found in ESRD patients with "normal" "LDL"cholesterol levels, indicating that the target "LDL" level should be lower than that for the general population. More than 40% of hemodialysis patients exceeded the upper limit (15 mg/dL, 95th percentile level) of IDL cholesterol in healthy subjects. Based on a linear relationship between IDL and "LDL," the normal range of IDL cholesterol (<15 mg/dL) corresponds to "LDL" cholesterol by the Friedewald equation below 100 mg/dL in hemodialysis patients. Statins effectively and safely reduce "LDL," including IDL in patients treated with hemodialysis or peritoneal dialysis. The effect of lipid-lowering therapy on cardiovascular mortality in ESRD, however, awaits the results of ongoing prospective trials.

Diabetes mellitus, aortic stiffness, and cardiovascular mortality in end-stage renal disease

Cardiovascular mortality is elevated in patients with end-stage renal disease (ESRD), especially in those with diabetes mellitus. Although the higher cardiovascular death rate in diabetic ESRD patients may be the result of more advanced atherosclerotic changes of the arterial wall, this has not been documented previously. Aortic stiffness was compared between ESRD patients with and without diabetes, and the impact of aortic stiffness on cardiovascular mortality was examined in a prospective, observational cohort study. The cohort consisted of 265 ESRD patients on hemodialysis, including 50 diabetic patients studied between June 1992 and December 1998. At baseline, the diabetic ESRD patients had significantly higher aortic pulse wave velocity (PWV), a noninvasive measure of aortic stiffness, than the nondiabetic patients. During a mean follow-up period of 63 mo, 81 deaths, including 36 cardiovascular deaths, were recorded. Kaplan-Meier analysis revealed higher all-cause or cardiovascular mortality rates in the diabetic as compared with the nondiabetic patients and also in those with higher aortic PWV than those with lower aortic PWV. The effect of diabetes on cardiovascular death was significant in the Cox model, including age, years on hemodialysis, gender, smoking, C-reactive protein, hematocrit, and body mass index as covariates. However, when aortic PWV was included as a covariate, the impact of diabetes was no longer significant, whereas aortic PWV was a significant predictor. In a model including 13 covariates, aortic PWV remained a significant predictor for cardiovascular and overall mortality but not for non-cardiovascular death. These results demonstrate that the increased aortic stiffness of the ESRD patients with diabetes mellitus contributed to the higher all-cause and cardiovascular mortality rates.

Femoral artery wall thickness and stiffness in evaluation of peripheral vascular disease in type 2 diabetes mellitus

Stiffening and thickening of arterial wall are two important components of atherosclerosis. The purpose of this study was to evaluate the effects of femoral artery wall stiffness on clinical manifestation of peripheral vascular disease (PVD) in type 2 diabetes mellitus. The subjects were 315 patients with type 2 diabetes. Presence of intermittent claudication and/or leg pain at rest and reduced ankle-brachial blood pressure index (ABI<0.9) were used as a subjective and an objective index of PVD, respectively. Femoral artery intima-media thickness (FA-IMT) and stiffness parameter beta (FA-stiffness beta) were measured by ultrasound methods. Symptomatic patients (N=58) showed greater values for both FA-IMT and FA-stiffness beta than those without symptom (N=257). Similarly, patients with reduced ABI (N=56) had greater FA-IMT and FA-stiffness beta than those without (N=259). However, correlation between FA-IMT and FA-stiffness beta was not impressive, especially in the symptomatic patients. To evaluate the effect of FA-stiffness beta on PVD symptoms, the subjects were divided into three subgroups according to FA-IMT, and then FA-stiffness beta was compared between those with and without PVD symptoms in each subgroup. The symptomatic patients had greater FA-stiffness beta values than the asymptomatic subjects in all the three subgroups. Multiple logistic regression analysis indicated that the presence of PVD symptoms was associated more closely with increased FA-stiffness beta than with increased FA-IMT, whereas reduced ABI was associated more closely with FA-IMT than with FA-stiffness beta. These data suggest that stiffening of arterial wall has a significant impact on PVD manifestations, particularly on the leg symptoms, in patients with type 2 diabetes.

Significant association between the progression of coronary artery calcification and dyslipidemia in patients on chronic hemodialysis

Quantification of coronary artery calcification (CAC) determined by electron-beam computed tomography (EBCT), known as the CAC score (CACS), correlates with total plaque amount and coronary risk factors and strongly associates with maximal stenosis in the epicardial arteries. However, data are limited concerning the CACS in chronic dialysis patients, although atherosclerotic vascular disease is the most frequent complication. We examined the relation between coronary risk factors, metabolic factors of calcium and other minerals, and CACS progression in 24 dialysis patients. The mean patient age was 53 +/- 14 (SD) years, and mean duration of dialysis was 64 +/- 69 months. In each patient, the CACS was measured twice, with a mean interscan period of 17 +/- 3 months. The mean CACS progressed from 449 +/- 605 to 669 +/- 894 overall, and the mean change in CACS (DeltaCACS) was 220 +/- 78. Patients were divided into two groups: slow progressors, with DeltaCACS of 7.5 +/- 31 (n = 12), and rapid progressors, with DeltaCACS of 432 +/- 458 (n = 12). Triglyceride concentrations (198 +/- 65 versus 103 +/- 50 mg/dL; P < 0.001) were high, and high-density lipoprotein cholesterol (HDL-C) concentrations (46 +/- 11 versus 60 +/- 18 mg/dL; P < 0.05) were low in rapid progressors. Rapid progression of CAC was associated with high triglyceride and low HDL-C concentrations. The clinical significance of these observations remains to be determined.

Evaluation of lipids peroxidation products vs. proinflammatory cytokines in hemodialized patients

BACKGROUND

Patients with end-stage renal failure on chronic hemodialysis often demonstrate accelerated development of atherosclerotic changes and cardiovascular complications. In those patients oxidative stress facilitates the intensity of lipid peroxidation process, expressed as increased products of lipid peroxidation (malonaldehyde and 4-hydroxyalkenals). Simultaneously, structures modified by peroxidation and glycation of autoantigenic character are formed. Additionally, increase in proinflammatory cytokines is found in their patients on hemodialysis. The aim of the study was to find out the relations between the products of lipid peroxidation and proinflammatory cytokines in patients on hemodialysis.

METHODS

Plasma concentrations of malonaldehyde and 4-hydroxyalkenals were estimated by spectrophotometric method, glutathione peroxidase as well as concentration of IL-6, its soluble receptor and TNFalpha were measured using ELISA kits.

RESULTS

Aldehyde concentrations (malonaldehyde and 4-hydroxyalkenals) were found to be five fold higher in comparison with the controls. Concentrations of proinflammatory cytokines: IL-6, TNFalpha and soluble IL-6 receptor were also higher than in the control group. Patients on hemodialysis showed positive correlation between concentrations of MDA+4HNE and IL-6 and TNFalpha.

CONCLUSION

The correlations found between the products of lipid peroxidation and proinflammatory cytokines suggest causative relation between the intensity of peroxidative processes and stimulation of immunological response in hemodialysed patients, which may increase the risk of atherosclerotic changes in those patients.

Antibodies against oxidized LDL and carotid artery intima-media thickness in a healthy population

Oxidation of LDLs plays an important role in atherosclerosis, and immune response to oxidized LDL (oxLDL) may modulate atherogenesis. Although immunization with oxLDL is shown to suppress atherogenesis in animal models, the role of the immune response to oxLDL is not well established in humans. We investigated the relationship between the titer of anti-oxLDL antibody (oxLDL Ab) and arterial wall thickness in a healthy population with no clinical signs of atherosclerosis. Intima-media thickness of the carotid arteries (CA-IMT) was measured by high-resolution B-mode ultrasonography in 446 healthy subjects. The titer of IgG-class oxLDL Ab was measured by a solid-phase ELISA. In univariate analysis, CA-IMT correlated positively with age, systolic blood pressure, total cholesterol, triglyceride, LDL cholesterol, body mass index, and waist-to-hip ratio, whereas it correlated negatively with HDL cholesterol and oxLDL Ab titer. The inverse association between oxLDL Ab titer and CA-IMT remained significant in multiple regression analysis, which took other confounding variables into account. These results indicate an independent inverse relationship between oxLDL Ab titer and CA-IMT in healthy subjects, supporting the hypothesis that immune response to oxLDL may have a protective role at an early stage of human atherosclerosis.

Management of selected lipid abnormalities. Hypertriglyceridemia, low HDL cholesterol, lipoprotein(a), in thyroid and renal diseases, and post-transplantation

Although the focus in treating lipid disorders is on reducing LDL cholesterol levels, triglycerides, HDL cholesterol, and Lp(a) are all independent risk factors that can be used clinically to assess cardiovascular risk. Decisions to initiate drug therapy for LDL cholesterol reduction may be influenced by levels of these other lipoprotein fractions. Data supporting intervention to modify these factors is less abundant than for LDL cholesterol reduction, but in certain circumstances drug therapy targeted at triglycerides or HDL cholesterol may be appropriate. Patients with nephrotic syndrome and end-stage renal disease are at particularly high risk for the development of cardiovascular disease and should be treated aggressively for lipid disorders. Finally, solid organ transplant recipients are almost always hyperlipidemic, and appropriate therapy could reduce cardiovascular events.

Homogeneous HDL-cholesterol assay versus ultracentrifugation/dextran sulfate-Mg2+ precipitation and dextran sulfate-Mg2+ precipitation in healthy population and in hemodialysis patients

OBJECTIVES

To evaluate the analytical performance of a new homogeneous HDL-cholesterol assay (Olympus Diagnostica). To investigate possibly discrepant results in chronic hemodialysis patients who commonly exhibit quantitative and qualitative lipoprotein abnormalities, responsible for atherogenic complications in these patients.

DESIGN AND METHODS

Serum samples were collected from 50 healthy subjects and 65 chronic hemodialysis patients. HDL-C levels measured by the homogeneous assay were compared with the routine dextran sulfate-Mg2+ precipitation method and the ultracentrifugation/dextran sulfate-Mg2+ precipitation as reference method.

RESULTS

The homogeneous assay was linear up to at least 220 mg/dL. The analytical precision was estimated with three different sets of commercial controls and one set of human pooled serum control. The within-day CV ranged between 1.7% and 3.8% and the between-day CV ranged between 1.0% and 2.3%. HDL-C values in both populations correlated highly with the dextran sulfate-Mg2+ precipitation method and the ultracentrifugation/dextran sulfate-Mg2+ precipitation method (r > or = 0.96, bias between -0.9 and 2.3 mg/dL). Lipemia up to triglyceride concentration of 600 mg/dL did not alter the HDL-C value.

CONCLUSIONS

The homogeneous assay for HDL-C (Olympus) uses much less sample, is accurate and convenient to handle, and allows full automation. The test should considerably facilitate the screening of individuals at an increased risk of cardiovascular disease, including hemodialysis patients.

Role of hepatic lipase in intermediate-density lipoprotein and small, dense low-density lipoprotein formation in hemodialysis patients

BACKGROUND

It has been reported that remnant lipoproteins and small, dense low-density lipoproteins (LDLs) are risk factors for cardiovascular disease. To determine whether these risk factors are present in hemodialysis (HD) patients who are suffering from a high incidence of atherosclerotic vascular disease, we measured concentrations of remnant lipoproteins and LDL particle diameter in HD patients and compared these with controls. We also measured lipoprotein lipase (LPL) and hepatic triglyceride lipase (HTGL) that play important roles in the generation of remnant lipoproteins and small, dense LDL, and we correlated these changes with plasma lipoprotein abnormalities in HD patients.

METHODS

Lipoproteins were separated by ultracentrifugation. Apoprotein B in very low-density lipoprotein (VLDL), and intermediate-density lipoprotein (IDL) fractions were measured by a sensitive enzyme-linked immunosorbent assay method. The average LDL particle diameter was measured by gradient gel electrophoresis.

RESULTS

Plasma triglyceride, total cholesterol, and high-density lipoprotein (HDL) cholesterol concentrations were comparable between HD patients and controls, whereas LDL cholesterol was significantly lower in HD patients. The average LDL particle diameter was not significantly different between HD patients and controls. LDL particle diameter was inversely related to plasma triglyceride concentrations in all of the subjects. VLDL triglyceride, VLDL cholesterol, and VLDL apoprotein B were comparable between HD patients and controls. IDL triglyceride, IDL cholesterol, and IDL apoprotein B concentrations were all significantly increased in HD patients compared with those in controls. LPL mass was not altered, but HTGL activity was significantly decreased in HD patients. The HTGL activity was inversely related to IDL concentrations.

CONCLUSIONS

These results suggest that a prominent characteristic of lipoprotein abnormalities in HD patients is a marked increase in IDL particle number. In addition, small, dense LDL is not associated with uremic dyslipidemia. Because HTGLs promote the conversion from IDL to LDL and the generation of lipid-poor LDL, a decrease in HTGL activity may contribute to the accumulation of IDL particle and may prevent small, dense LDL formation in HD patients.

Effects of lipid-lowering drugs on intermediate-density lipoprotein in uremic patients

BACKGROUND

Patients with chronic renal failure often have alterations in lipoprotein profile including elevated very-low density lipoprotein (VLDL) and intermediate density lipoprotein (IDL), and reduced high density lipoprotein (HDL) levels. Among these changes, raised IDL has been shown as an independent risk factor for atherosclerosis in hemodialysis patients. There are a limited number of studies reporting pharmacological approaches to IDL reduction in a uremic population.

METHODS

We therefore summarize the effects of lipid-lowering drugs on IDL levels in patients with chronic renal failure treated by hemodialysis (HD) or continuous ambulatory peritoneal dialysis (CAPD).

RESULTS

First, a nicotinic acid analog niceritrol was given to hemodialysis patients. The drug increased HDL-cholesterol by 11%, but the reductions in VLDL-, IDL- and LDL-cholesterol were not significant. Second, CAPD patients were treated with a fibric acid derivative clinofibrate, which was excreted mainly into bile unlike other drugs in this class. The fibrate resulted in a remarkable reduction in VLDL-triglycerides, although it did not reduce IDL-cholesterol. Finally, an HMG-CoA reductase inhibitor (statin) pravastatin was used in HD and CAPD patients. Pravastatin reduced IDL- and LDL-cholesterol to the same extent (by 31%). None of these treatments caused serious adverse effects.

CONCLUSIONS

We propose that IDL is an important target in the management of uremic dyslipidemia. To date, statins have been shown to be suitable for this purpose, although it remains to be clarified whether such an intervention reduces the risk for atherosclerotic vascular events in the uremic population.