Multicenter study of lipoprotein(a) and apolipoprotein(a) phenotypes in patients with end-stage renal disease treated by hemodialysis or continuous ambulatory peritoneal dialysis

Characterization of the plasma proteomic profile of Fabry disease: Potential sex- and clinical phenotype-specific biomarkers

Fabry disease (FD) is a X-linked rare lysosomal storage disorder caused by deficient α-galactosidase A (α-GalA) activity. Early diagnosis and the prediction of disease course are complicated by the clinical heterogeneity of FD, as well as by the frequently inconclusive biochemical and genetic test results that do not correlate with clinical course. We sought to identify potential biomarkers of FD to better understand the underlying pathophysiology and clinical phenotypes. We compared the plasma proteomes of 50 FD patients and 50 matched healthy controls using DDA and SWATH-MS. The >30 proteins that were differentially expressed between the 2 groups included proteins implicated in processes such as inflammation, heme and haemoglobin metabolism, oxidative stress, coagulation, complement cascade, glucose and lipid metabolism, and glycocalyx formation. Stratification by sex revealed that certain proteins were differentially expressed in a sex-dependent manner. Apolipoprotein A-IV was upregulated in FD patients with complications, especially those with chronic kidney disease, and apolipoprotein C-III and fetuin-A were identified as possible markers of FD with left ventricular hypertrophy. All these proteins had a greater capacity to identify the presence of complications in FD patients than lyso-GB3, with apolipoprotein A-IV standing out as being more sensitive and effective in differentiating the presence and absence of chronic kidney disease in FD patients than renal markers such as creatinine, glomerular filtration rate and microalbuminuria. Identification of these potential biomarkers can help further our understanding of the pathophysiological processes that underlie the heterogeneous clinical manifestations associated with FD.

Comparative analysis of hemodialysis and peritoneal dialysis on the risk of new onset diabetes mellitus

BACKGROUND

Diabetes mellitus is a significant risk factor for cardiovascular events and mortality in dialysis patients. The impact of different dialysis modalities on the risk of new onset diabetes mellitus (NODM) remains a subject of debate. Previous studies did not adequately account for critical confounding factors such as pre-dialysis glycemic status, medication use, and nutritional status, which may influence the association between dialysis modality and NODM risk.

METHODS

We conducted a retrospective cohort study of 1426 non-diabetic end-stage renal disease (ESRD) patients who underwent either hemodialysis (HD) or peritoneal dialysis (PD) at a single medical center. We used different statistical methods, adjusting for potential confounding factors, and accounted for competing risk of death.

RESULTS

Over 12 years, 331 patients (23 %) developed NODM. After adjusting for potential confounding factors and mortality, PD patients had a significantly higher risk of NODM compared to HD patients (adjusted HR 1.52, p = 0.001). A propensity-matched cohort sensitivity analysis yielded similar results. Among patients with prediabetes, those receiving PD had a 2.93 times higher risk of developing NODM than those receiving HD (p for interaction <0.001), whereas no significant difference was observed among euglycemic patients. NODM was also associated with a 1.78 times increased risk of major cardiovascular events.

CONCLUSION

Our study provides evidence that PD treatment may increase the risk of NODM in ESRD patients, particularly among those with preexisting prediabetes. These findings highlight the importance of personalized treatment approaches, and nephrologists should consider prediabetes when choosing the dialysis modality for their patients.

Apolipoprotein A-IV concentrations and cancer in a large cohort of chronic kidney disease patients: results from the GCKD study

BACKGROUND

Chronic kidney disease (CKD) is highly connected to inflammation and oxidative stress. Both favour the development of cancer in CKD patients. Serum apolipoprotein A-IV (apoA-IV) concentrations are influenced by kidney function and are an early marker of kidney impairment. Besides others, it has antioxidant and anti-inflammatory properties. Proteomic studies and small case-control studies identified low apoA-IV as a biomarker for various forms of cancer; however, prospective studies are lacking. We therefore investigated whether serum apoA-IV is associated with cancer in the German Chronic Kidney Disease (GCKD) study.

METHODS

These analyses include 5039 Caucasian patients from the prospective GCKD cohort study followed for 6.5 years. Main inclusion criteria were an eGFR of 30-60 mL/min/1.73m2 or an eGFR > 60 mL/min/1.73m2 in the presence of overt proteinuria.

RESULTS

Mean apoA-IV concentrations of the entire cohort were 28.9 ± 9.8 mg/dL (median 27.6 mg/dL). 615 patients had a history of cancer before the enrolment into the study. ApoA-IV concentrations above the median were associated with a lower odds for a history of cancer (OR = 0.79, p = 0.02 when adjusted age, sex, smoking, diabetes, BMI, albuminuria, statin intake, and eGFRcreatinine). During follow-up 368 patients developed an incident cancer event and those with apoA-IV above the median had a lower risk (HR = 0.72, 95%CI 0.57-0.90, P = 0.004). Finally, 62 patients died from such an incident cancer event and each 10 mg/dL higher apoA-IV concentrations were associated with a lower risk for fatal cancer (HR = 0.62, 95%CI 0.44-0.88, P = 0.007).

CONCLUSIONS

Our data indicate an association of high apoA-IV concentrations with reduced frequencies of a history of cancer as well as incident fatal and non-fatal cancer events in a large cohort of patients with CKD.

The Clinical Significance of LDL-Cholesterol on the Outcomes of Hemodialysis Patients with Acute Coronary Syndrome

Background and objectives: Dyslipidemia is one of the most important modifiable risk factors in the pathogenesis of cardiovascular disease in the general population, but its importance in the hemodialysis (HD) population is uncertain. Materials and Methods: This retrospective cohort study includes HD patients hospitalized due to acute coronary syndrome (ACS) in the period 2015-2020 with lipid profile data during ACS. A control group with preserved kidney function was matched. Risk factors for 30-day and 1-year mortality were assessed. Results: Among 349 patients included in the analysis, 246 were HD-dependent ("HD group"). HD group patients had higher prevalence of diabetes, hypertension, and heart disease than the control group. At ACS hospitalization, lipid profile and chronic statin treatment were comparable between groups. Odds ratios for 30-day mortality in HD vs. control group was 5.2 (95% CI 1.8-15; p = 0.002) and for 1-year, 3.4 (95% CI 1.9-6.1; p <0.001). LDL and LDL < 70 did not change 30-day and 1-year mortality rates in the HD group (p = 0.995, 0.823, respectively). However, survival after ACS in HD patients correlated positively with nutritional parameters such as serum albumin (r = 0.368, p < 0.001) and total cholesterol (r = 0.185, p < 0.001), and inversely with the inflammatory markers C-reactive protein (CRP; r = -0.348, p < 0.001) and neutrophils-to-lymphocytes ratio (NLR; r = -0.181, p = 0.019). Multivariate analysis demonstrated that heart failure was the only significant predictor of 1-year mortality (OR 2.8, p = 0.002). LDL < 70 mg/dL at ACS hospitalization did not predict 1-year mortality in the HD group. Conclusions: Despite comparable lipid profiles and statin treatment before and after ACS hospitalization, mortality rates were significantly higher among HD group. While malnutrition-inflammation markers were associated with survival of dialysis patients after ACS, LDL cholesterol was not. Thus, our study results emphasize that better nutritional status and less inflammation are associated with improved survival among HD patients.

Lipoprotein(a) in atherosclerotic cardiovascular disease and aortic stenosis: a European Atherosclerosis Society consensus statement

This 2022 European Atherosclerosis Society lipoprotein(a) [Lp(a)] consensus statement updates evidence for the role of Lp(a) in atherosclerotic cardiovascular disease (ASCVD) and aortic valve stenosis, provides clinical guidance for testing and treating elevated Lp(a) levels, and considers its inclusion in global risk estimation. Epidemiologic and genetic studies involving hundreds of thousands of individuals strongly support a causal and continuous association between Lp(a) concentration and cardiovascular outcomes in different ethnicities; elevated Lp(a) is a risk factor even at very low levels of low-density lipoprotein cholesterol. High Lp(a) is associated with both microcalcification and macrocalcification of the aortic valve. Current findings do not support Lp(a) as a risk factor for venous thrombotic events and impaired fibrinolysis. Very low Lp(a) levels may associate with increased risk of diabetes mellitus meriting further study. Lp(a) has pro-inflammatory and pro-atherosclerotic properties, which may partly relate to the oxidized phospholipids carried by Lp(a). This panel recommends testing Lp(a) concentration at least once in adults; cascade testing has potential value in familial hypercholesterolaemia, or with family or personal history of (very) high Lp(a) or premature ASCVD. Without specific Lp(a)-lowering therapies, early intensive risk factor management is recommended, targeted according to global cardiovascular risk and Lp(a) level. Lipoprotein apheresis is an option for very high Lp(a) with progressive cardiovascular disease despite optimal management of risk factors. In conclusion, this statement reinforces evidence for Lp(a) as a causal risk factor for cardiovascular outcomes. Trials of specific Lp(a)-lowering treatments are critical to confirm clinical benefit for cardiovascular disease and aortic valve stenosis.

Non-genetic influences on lipoprotein(a) concentrations

An elevated level of lipoprotein(a) [Lp(a)] is a genetically regulated, independent, causal risk factor for cardiovascular disease. However, the extensive variability in Lp(a) levels between individuals and population groups cannot be fully explained by genetic factors, emphasizing a potential role for non-genetic factors. In this review, we provide an overview of current evidence on non-genetic factors influencing Lp(a) levels with a particular focus on diet, physical activity, hormones and certain pathological conditions. Findings from randomized controlled clinical trials show that diets lower in saturated fats modestly influence Lp(a) levels and often in the opposing direction to LDL cholesterol. Results from studies on physical activity/exercise have been inconsistent, ranging from no to minimal or moderate change in Lp(a) levels, potentially modulated by age and the type, intensity, and duration of exercise modality. Hormone replacement therapy (HRT) in postmenopausal women lowers Lp(a) levels with oral being more effective than transdermal estradiol; the type of HRT, dose of estrogen and addition of progestogen do not modify the Lp(a)-lowering effect of HRT. Kidney diseases result in marked elevations in Lp(a) levels, albeit dependent on disease stages, dialysis modalities and apolipoprotein(a) phenotypes. In contrast, Lp(a) levels are reduced in liver diseases in parallel with the disease progression, although population studies have yielded conflicting results on the associations between Lp(a) levels and nonalcoholic fatty liver disease. Overall, current evidence supports a role for diet, hormones and related conditions, and liver and kidney diseases in modifying Lp(a) levels.

Apolipoprotein A-IV concentrations and clinical outcomes in a large chronic kidney disease cohort: Results from the GCKD study

BACKGROUND

Chronic kidney disease (CKD) represents a chronic proinflammatory state and is associated with very high cardiovascular risk. Apolipoprotein A-IV (apoA-IV) has antiatherogenic, antioxidative, anti-inflammatory and antithrombotic properties and levels increase significantly during the course of CKD.

OBJECTIVES

We aimed to investigate the association between apoA-IV and all-cause mortality and cardiovascular outcomes in the German Chronic Kidney Disease study.

METHODS

This was a prospective cohort study including 5141 Caucasian patients with available apoA-IV measurements and CKD. The majority of the patients had an estimated glomerular filtration rate (eGFR) of 30-60 ml/min/1.73m² or an eGFR >60 ml/min/1.73m² in the presence of overt proteinuria. Median follow-up was 6.5 years. The association of apoA-IV with comorbidities at baseline and endpoints during follow-up was modelled adjusting for major confounders.

RESULTS

Mean apoA-IV concentrations of the entire cohort were 28.9 ± 9.8 mg/dl. Patients in the highest apoA-IV quartile had the lowest high-sensitivity C-reactive protein values despite the highest prevalence of diabetes, albuminuria and the lowest eGFR. Each 10 mg/dl higher apoA-IV translated into lower odds of prevalent cardiovascular disease (1289 cases, odds ratio = 0.80, 95% confidence interval [CI] 0.72-0.86, p = 0.0000003). During follow-up, each 10 mg/dl higher apoA-IV was significantly associated with a lower risk for all-cause mortality (600 cases, hazard ratio [HR] = 0.81, 95% CI 0.73-0.89, p = 0.00004), incident major adverse cardiovascular events (506 cases, HR = 0.88, 95% CI 0.79-0.99, p = 0.03) and death or hospitalizations due to heart failure (346 cases, HR = 0.84, 95% CI 0.73-0.96, p = 0.01).

CONCLUSIONS

These data support a link between elevated apoA-IV concentrations and reduced inflammation in moderate CKD. ApoA-IV appears to be an independent risk marker for reduced all-cause mortality, cardiovascular events and heart failure in a large cohort of patients with CKD.

Cholesterol Metabolism in Chronic Kidney Disease: Physiology, Pathologic Mechanisms, and Treatment

High plasma levels of lipids and/or lipoproteins are risk factors for atherosclerosis, nonalcoholic fatty liver disease (NAFLD), obesity, and diabetes. These four conditions have also been identified as risk factors leading to the development of chronic kidney disease (CKD). Although many pathways that generate high plasma levels of these factors have been identified, most clinical and physiologic dysfunction results from aberrant assembly and secretion of lipoproteins. The results of several published studies suggest that elevated levels of low-density lipoprotein (LDL)-cholesterol are a risk factor for atherosclerosis, myocardial infarction, coronary artery calcification associated with type 2 diabetes, and NAFLD. Cholesterol metabolism has also been identified as an important pathway contributing to the development of CKD; clinical treatments designed to alter various steps of the cholesterol synthesis and metabolism pathway are currently under study. Cholesterol synthesis and catabolism contribute to a multistep process with pathways that are regulated at the cellular level in renal tissue. Cholesterol metabolism may also be regulated by the balance between the influx and efflux of cholesterol molecules that are capable of crossing the membrane of renal proximal tubular epithelial cells and podocytes. Cellular accumulation of cholesterol can result in lipotoxicity and ultimately kidney dysfunction and failure. Thus, further research focused on cholesterol metabolism pathways will be necessary to improve our understanding of the impact of cholesterol restriction, which is currently a primary intervention recommended for patients with dyslipidemia.

Beyond Lipoprotein(a) plasma measurements: Lipoprotein(a) and inflammation

Genome wide association, epidemiological, and clinical studies have established high lipoprotein(a) [Lp(a)] as a causal risk factor for atherosclerotic cardiovascular disease (ASCVD). Lp(a) is an apoB100 containing lipoprotein covalently bound to apolipoprotein(a) [apo(a)], a glycoprotein. Plasma Lp(a) levels are to a large extent determined by genetics. Its link to cardiovascular disease (CVD) may be driven by its pro-inflammatory effects, of which its association with oxidized phospholipids (oxPL) bound to Lp(a) is the most studied. Various inflammatory conditions, such as rheumatoid arthritis (RA), systemic lupus erythematosus, acquired immunodeficiency syndrome, and chronic renal failure are associated with high Lp(a) levels. In cases of RA, high Lp(a) levels are reversed by interleukin-6 receptor (IL-6R) blockade by tocilizumab, suggesting a potential role for IL-6 in regulating Lp(a) plasma levels. Elevated levels of IL-6 and IL-6R polymorphisms are associated with CVD. Therapies aimed at lowering apo(a) and thereby reducing plasma Lp(a) levels are in clinical trials. Their results will determine if reductions in apo(a) and Lp(a) decrease cardiovascular outcomes. As we enter this new arena of available treatments, there is a need to improve our understanding of mechanisms. This review will focus on the role of Lp(a) in inflammation and CVD.

Hyperlipidemia and mortality associated with diabetes mellitus co-existence in Chinese peritoneal dialysis patients

Background

To evaluate associations between diabetes mellitus (DM) coexisting with hyperlipidemia and mortality in peritoneal dialysis (PD) patients.

Methods

This was a retrospective cohort study with 2939 incident PD patients in China from January 2005 to December 2018. Associations between the DM coexisting with hyperlipidemia and mortality were evaluated using the Cox regression.

Results

Of 2939 patients, with a median age of 50.0 years, 519 (17.7%) died during the median of 35.1 months. DM coexisting with hyperlipidemia, DM, and hyperlipidemia were associated with 1.93 (95% CI 1.45 to 2.56), 1.86 (95% CI 1.49 to 2.32), and 0.90 (95% CI 0.66 to 1.24)-time higher risk of all-cause mortality, compared with without DM and hyperlipidemia, respectively (P for trend < 0.001). Subgroup analyses showed a similar pattern. Among DM patients, hyperlipidemia was as a high risk of mortality as non-hyperlipidemia (hazard ratio 1.02, 95%CI 0.73 to 1.43) during the overall follow-up period, but from 48-month follow-up onwards, hyperlipidemia patients had 3.60 (95%CI 1.62 to 8.01)-fold higher risk of all-cause mortality than those non-hyperlipidemia (P interaction = 1.000).

Conclusions

PD patients with DM coexisting with hyperlipidemia were at the highest risk of all-cause mortality, followed by DM patients and hyperlipidemia patients, and hyperlipidemia may have an adverse effect on long-term survival in DM patients.

Serum lipoprotein (a) associates with a higher risk of reduced renal function: a prospective investigation

Lipoprotein (a) [Lp(a)] is a well-known risk factor for cardiovascular disease, but analysis on Lp(a) and renal dysfunction is scarce. We aimed to investigate prospectively the association of serum Lp(a) with the risk of reduced renal function, and further investigated whether diabetic or hypertensive status modified such association. Six thousand two hundred and fifty-seven Chinese adults aged ≤40 years and free of reduced renal function at baseline were included in the study. Reduced renal function was defined as estimated glomerular filtration rate <60 ml/min/1.73 m². During a mean follow-up of 4.4 years, 158 participants developed reduced renal function. Each one-unit increase in log₁₀-Lp(a) (milligrams per deciliter) was associated with a 1.99-fold (95% CI 1.15–3.43) increased risk of incident reduced renal function; the multivariable-adjusted odds ratio (OR) for the highest tertile of Lp(a) was 1.61 (95% CI 1.03–2.52) compared with the lowest tertile (P for trend = 0.03). The stratified analysis showed the association of serum Lp(a) and incident reduced renal function was more prominent in participants with prevalent diabetes [OR 4.04, 95% CI (1.42–11.54)] or hypertension [OR 2.18, 95% CI (1.22–3.89)]. A stronger association was observed in the group with diabetes and high Lp(a) (>25 mg/dl), indicating a combined effect of diabetes and high Lp(a) on the reduced renal function risk. An elevated Lp(a) level was independently associated with risk of incident reduced renal function, especially in diabetic or hypertensive patients.

The Role of Peritoneal Dialysis as the First-Line Renal Replacement Modality

Twenty years after its introduction, peritoneal dialysis (PD) is a well-established alternative to hemodialysis (HD) as a modality of renal replacement therapy. Much debate and research is apparent in the literature, comparing hemodialysis and PD as “opposite” modalities and trying to ascertain which modality should be more optimal.

In our opinion, HD and PD are two distinct modalities, each with its own advantages and disadvantages. In addition, it is clear that for both HD and PD, rates of technique failure are high, causing patients to transfer between modalities. The question is thus not which modality is best, but rather, which flow-chart of modalities makes best use of the advantages of each modality, while avoiding its disadvantages. In this respect, HD and PD appear to be complementary modalities.

The better preservation of residual renal function, lower risk of infection with hepatitis B and C, better outcome after transplantation, preservation of vascular access, and lower costs are arguments to promote PD as a good initial treatment. When PD-related problems arise (adequacy, ultrafiltration, peritonitis, patient burnout), a timely transfer to HD has to be planned.

This editorial tries to review arguments supporting the complementary nature of both modalities, and especially the role of PD as the first-line renal replacement therapy.

Major and Minor Risk Factors for Cardiovascular Disease in Continuous Ambulatory Peritoneal Dialysis Patients

Uremia in general and peritoneal dialysis in particular bring with them risk factors for the development of cardiovascular disease. These factors include multiple lipid abnormalities, hyperhomocysteinemia, abdominal obesity, chronic inflammation, hypoalbuminemia, oxidative stress, and AGE formation. When these are combined with conventional risk factors, one can appreciate why the incidence of cardiovascular disease is so high in peritoneal dialysis patients. Treatment strategies should address each of these risks appropriately.

Peritoneal Dialysis: Better than, Equal to, or Worse than Hemodialysis? Data Worth Knowing before Choosing a Dialysis Modality

Technological advances such as those that allow the delivery of an adequate dialysis dose to a larger percentage of patients, minimization of peritoneal membrane damage with more biocompatible solutions, and lower peritonitis rates will undoubtedly improve retention of patients on peritoneal dialysis (PD) for longer periods. Currently, only 15% of the world dialysis population is managed by PD. Peritoneal dialysis has many advantages over hemodialysis, and if end-stage renal disease (ESRD) patients are fully informed about them, the proportion of patients who would prefer this treatment would rise to 25% – 30%. An integrated approach to the treatment of ESRD could start with PD in a large percentage of patients, especially those who will receive a kidney transplant within 2 – 3 years. With the present epidemic of ESRD, this approach could lead to a significant saving, relieve the pressure on dialysis units, and allow a larger number of ESRD patients to be treated.

Statins for Treatment of Dyslipidemia in Chronic Kidney Disease

Dyslipidemia is a potent cardiovascular (CV) risk factor in the general population. Elevated low-density lipoprotein cholesterol (LDL-C) and/or low high-density lipoprotein (HDL-C) are well-established CV risk factors, but more precise determinants of risk include increased apoprotein B (ApoB), lipoprotein(a) [Lp(a)], intermediate and very low-density lipoprotein (IDL-C, VLDL-C; “remnant particles”), and small dense LDL particles. Lipoprotein metabolism is altered in association with declining glomerular filtration rate such that patients with non dialysis-dependent chronic kidney disease (CKD) have lower levels of HDL-C, higher triglyceride, ApoB, remnant IDL-C, remnant VLDL-C, and Lp(a), and a greater proportion of oxidized LDL-C. Similar abnormalities are prevalent in hemodialysis (HD) patients, who often manifest proatherogenic changes in LDL-C in the absence of increased levels. Patients treated with peritoneal dialysis (PD) have a similar but more severe dyslipidemia compared to HD patients due to stimulation of hepatic lipoprotein synthesis by glucose absorption from dialysate, increased insulin levels, and selective protein loss in the dialysate analogous to the nephrotic syndrome. In the dialysis-dependent CKD population, total cholesterol is directly associated with increased mortality after controlling for the presence of malnutrition–inflammation.

Treatment with statins reduces CV mortality in the general population by approximately one third, irrespective of baseline LDL-C or prior CV events. Statins have similar, if not greater, efficacy in altering the lipid profile in patients with dialysis-dependent CKD (HD and PD) compared to those with normal renal function, and are well tolerated in CKD patients at moderate doses (≤ 20 mg/day atorvastatin or simvastatin). Statins reduce C-reactive protein as well as lipid moieties such as ApoB, remnants IDL and VLDL-C, and oxidized and small dense LDL-C fraction. Large observational studies demonstrate that statin treatment is independently associated with a 30% – 50% mortality reduction in patients with dialysis-dependent CKD (similar between HD- and PD-treated patients). One recent randomized controlled trial evaluated the ability of statin treatment to reduce mortality in type II diabetics treated with HD (“4D”); the primary end point of death from cardiac cause, myocardial infarction, and stroke was not significantly reduced. However, results of this trial may not apply to other end-stage renal disease populations. Two ongoing randomized controlled trials (SHARP and AURORA) are underway evaluating the effect of statins on CV events and death in patients with CKD (including patients treated with HD and PD). Recruitment to future trials should be given a high priority by nephrologists and, until more data are available, consideration should be given to following published guidelines for the treatment of dyslipidemia in CKD. Additional consideration could be given to treating all dialysis patients felt to be at risk of CV disease (irrespective of cholesterol level), given the safety and potential efficacy of statins. This is especially relevant in patients treated with PD, given their more atherogenic lipid profile and the lack of randomized controlled trials in this population.

Lipoprotein(a) and Risk of Ischemic Stroke in the REGARDS Study

Objective- Increased Lp(a) [lipoprotein(a)] is associated with coronary heart disease risk, but links with stroke are less consistent. Blacks have higher Lp(a) levels and stroke incidence than whites but have been underrepresented in studies. We hypothesized that Lp(a) is a risk factor for ischemic stroke and that risk differs by race. Approach and Results- REGARDS (Reasons for Geographic and Racial Differences in Stroke) recruited 30 239 black and white US adults aged ≥45 in 2003-2007 to study regional and racial differences in stroke mortality. We measured baseline Lp(a) by immunonephelometric assay in 572 cases of incident ischemic stroke and a 967-person cohort random sample. The hazard ratio of stroke by baseline Lp(a) was calculated using Cox proportional hazards models, stratified by race. Lp(a) was modeled in sex- and race-specific quartiles, given known differences in distributions by race and sex. Interactions were tested by including interaction terms in the proportional hazards models, with P<0.10 considered statistically significant. After adjustment for age, sex, and stroke risk factors, being in the fourth versus the first Lp(a) quartile was weakly associated with ischemic stroke overall, hazard ratio, 1.45 (95% CI, 0.96-2.19). In blacks, the hazard ratio was 1.96 (95% CI, 1.10-3.46), whereas in whites HR was 1.14 (95% CI, 0.64-2.04); P interaction=0.12. Lp(a) was lower in men than women, but associations with stroke in men and women were similar. Conclusions- We confirm that Lp(a) is a risk factor for ischemic stroke. Further research is needed to confirm the role of racial differences of the Lp(a) risk multiplier in ischemic stroke.

Albumin handling in different hemodialysis modalities

Hypoalbuminemia is a major risk factor for morbidity and mortality in dialysis patients. With increasing interest in highly permeable membranes and convective therapies to improve removal of middle molecules, transmembrane albumin loss increases accordingly. Currently, the acceptable upper limit of albumin loss for extracorporeal renal replacement therapies is unknown. In theory, any additional albumin loss should be minimized because it may contribute to hypoalbuminemia and adversely affect the patient's prognosis. However, hypoalbuminemia-associated mortality may be a consequence of inflammation and malnutrition, rather than low albumin levels per se. The purpose of this review is to give an overview of albumin handling with different extracorporeal renal replacement strategies. We conclude that the acceptable upper limit of dialysis-related albumin loss remains unknown. Whether enhanced middle molecule removal outweighs the potential adverse effects of increased albumin loss with novel highly permeable membranes and convective therapies is yet to be determined.

The role of lipoprotein (a) in chronic kidney disease

Lipoprotein (a) [Lp(a)] and its measurement, structure and function, the impact of ethnicity and environmental factors, epidemiological and genetic associations with vascular disease, and new prospects in drug development have been extensively examined throughout this Thematic Review Series on Lp(a). Studies suggest that the kidney has a role in Lp(a) catabolism, and that Lp(a) levels are increased in association with kidney disease only for people with large apo(a) isoforms. By contrast, in those patients with large protein losses, as in the nephrotic syndrome and continuous ambulatory peritoneal dialysis, Lp(a) is increased irrespective of apo(a) isoform size. Such acquired abnormalities can be reversed by kidney transplantation or remission of nephrosis. In this Thematic Review, we focus on the relationship between Lp(a), chronic kidney disease, and risk of cardiovascular events.

HDL in CKD-The Devil Is in the Detail

The picture of HDL cholesterol (HDL-C) as the "good" cholesterol has eroded. This is even more surprising because there exists strong evidence that HDL-C is associated with cardiovascular disease (CVD) in the general population as well as in patients with impairment of kidney function and/or progression of CKD. However, drugs that dramatically increase HDL-C have mostly failed to decrease CVD events. Furthermore, genetic studies took the same line, as genetic variants that have a pronounced influence on HDL-C concentrations did not show an association with cardiovascular risk. For many, this was not surprising, given that an HDL particle is highly complex and carries >80 proteins and several hundred lipid species. Simply measuring cholesterol might not reflect the variety of biologic effects of heterogeneous HDL particles. Therefore, functional studies and the involvement of HDL components in the reverse cholesterol transport, including the cholesterol efflux capacity, have become a further focus of study during recent years. As also observed for other aspects, CKD populations behave differently compared with non-CKD populations. Although clear disturbances have been observed for the "functionality" of HDL particles in patients with CKD, this did not necessarily translate into clear-cut associations with outcomes.

Hemodialysis Vascular Access Thrombosis and Lipoprotein(A)

Background

Vascular access remains the Achilles's heel of successful hemodialysis and thrombosis is the leading cause of vascular access failure. Elevated lipoprotein(a) (Lp(a)) levels in hemodialysis patients were reported, and in some studies were also associated with hemodialysis vascular access thrombosis.

Patients and Methods

In our study 84 hemodialysis patients with native arteriovenous fistula were included. Two groups of patients were defined: group A including 61 patients with their vascular access either never or only once thrombosed, and group B including 23 patients with two or more thromboses of their vascular access. We determined serum concentrations of Lp(a) in all our patients.

Results

Average serum Lp(a) concentration for all the patients included in the study was 0.273 ± 0.31 g/l. No relationship was found between serum Lp(a) concentrations and age, gender and duration of dialysis treatment. Serum Lp(a) concentrations were higher in group A than in group B patients (0.301 g/l versus 0.198 g/l), but the difference was not statistically significant. There was also no statistically significant difference between group A and group B regarding age, gender and duration of hemodialysis treatment. The use of a cut-off value for Lp(a) of 0.3 g/l and 0.57 g/l also failed to provide a significant difference between group A and B patients.

Conclusion

We found no significant differences in Lp(a) concentrations between group A (thrombosis-non-prone) and group B (thrombosis-prone) patients. Our results suggest that Lp(a) is not an independent risk factor for vascular access occlusion in hemodialysis patients.

Lipoprotein(a) in clinical practice: New perspectives from basic and translational science

Elevated plasma concentrations of lipoprotein(a) (Lp(a)) are a causal risk factor for coronary heart disease (CHD) and calcific aortic valve stenosis (CAVS). Genetic, epidemiological and in vitro data provide strong evidence for a pathogenic role for Lp(a) in the progression of atherothrombotic disease. Despite these advancements and a race to develop new Lp(a) lowering therapies, there are still many unanswered and emerging questions about the metabolism and pathophysiology of Lp(a). New studies have drawn attention to Lp(a) as a contributor to novel pathogenic processes, yet the mechanisms underlying the contribution of Lp(a) to CVD remain enigmatic. New therapeutics show promise in lowering plasma Lp(a) levels, although the complete mechanisms of Lp(a) lowering are not fully understood. Specific agents targeted to apolipoprotein(a) (apo(a)), namely antisense oligonucleotide therapy, demonstrate potential to decrease Lp(a) to levels below the 30-50 mg/dL (75-150 nmol/L) CVD risk threshold. This therapeutic approach should aid in assessing the benefit of lowering Lp(a) in a clinical setting.

The pattern of choosing dialysis modality and related mortality outcomes in Korea: a national population-based study

BACKGROUND/AIMS

Since comorbidities are major determinants of modality choice, and also interact with dialysis modality on mortality outcomes, we examined the pattern of modality choice according to comorbidities and then evaluated how such choices affected mortality in incident dialysis patients.

METHODS

We analyzed 32,280 incident dialysis patients in Korea. Patterns in initial dialysis choice were assessed by multivariate logistic regression analyses. Multivariate Poisson regression analyses were performed to evaluate the effects of interactions between comorbidities and dialysis modality on mortality and to quantify these interactions using the synergy factor.

RESULTS

Prior histories of myocardial infarction (p = 0.031), diabetes (p = 0.001), and congestive heart failure (p = 0.003) were independent factors favoring the initiation with peritoneal dialysis (PD), but were associated with increased mortality with PD. In contrast, a history of cerebrovascular disease and 1-year increase in age favored initiation with hemodialysis (HD) and were related to a survival benefit with HD (p < 0.001, both). While favoring initiation with HD, having Medical Aid (p = 0.001) and male gender (p = 0.047) were related to increased mortality with HD. Furthermore, although the severity of comorbidities did not inf luence dialysis modality choice, mortality in incident PD patients was significantly higher compared to that in HD patients as the severity of comorbidities increased (p for trend < 0.001).

CONCLUSIONS

Some comorbidities exerted independent effects on initial choice of dialysis modality, but this choice did not always lead to the best results. Further analyses of the pattern of choosing dialysis modality according to baseline comorbid conditions and related consequent mortality outcomes are needed.

Association of serum lipid levels over time with survival in incident peritoneal dialysis patients

BACKGROUND

The association of dyslipidemia with mortality has not been fully evaluated in patients on peritoneal dialysis (PD). Moreover, changes in lipids levels over time and associated death risk have not yet been studied in this population.

OBJECTIVE

We studied the association of time-updated serum lipid concentrations with all-cause and cardiovascular (CV) mortalities in a 10-year cohort of 749 incident PD patients.

METHODS

Association was assessed using time-varying Cox proportional hazard regression models with adjustment for multiple variables including statin therapy.

RESULTS

During a median follow-up of 36 (interquartile range, 21-61) months, 273 all-cause and 107 CV deaths occurred. Compared with those with total cholesterol (TC) of 180 to <210 or low-density lipoprotein cholesterol (LDL-C) of 100 to <130 mg/dL, hazard ratios (95% confidence interval) of the lowest TC (<150 mg/dL) and LDL-C (<70 mg/dL) were 2.32 (1.61-3.35) and 2.02 (1.45-2.83) for all-cause mortality and 1.87 (1.04-3.37) and 1.92 (1.13-3.26) for CV mortality, respectively. Lower triglyceride (<100 mg/dL) and high-density lipoprotein cholesterol (<30 mg/dL) levels were associated with higher all-cause mortality (1.66 [1.11-2.47] and 1.57 [1.08-2.29]) but not with CV mortality.

CONCLUSIONS

Contrary to the general population, lower TC and LDL-C levels over time were significantly associated with both worse survival and increased CV mortality in incident PD patients. Although lower triglyceride and high-density lipoprotein cholesterol concentrations were associated with significantly higher all-cause mortality, they failed to show any clear association with CV mortality. The underlying mechanisms responsible for this apparent paradox await further investigations.

Apolipoprotein L1 and apolipoprotein A-IV and their association with kidney function

PURPOSE OF REVIEW

Chronic kidney disease (CKD) is a common disease with an estimated prevalence of 10-12%. There are pronounced differences between ethnicities with a 3-fold to 4-fold higher lifetime risk for end-stage kidney disease in African Americans compared to European Americans. The purpose of this review was to discuss recent findings on two apolipoproteins (apolipoprotein L1 and A-IV) in the context of kidney disease and kidney function.

RECENT FINDINGS

The observation that certain apolipoprotein L1 risk genotypes that are only present in African Americans might explain a major fraction of the ethnic differences for nondiabetic CKD has set the stage for this otherwise under-researched apolipoprotein. These risk genotypes on the one hand protect African Americans against African sleeping sickness but cause on the other hand several types of nondiabetic CKD. We are currently beginning to understand the mechanisms how apolipoprotein L1 is involved in the modification of lysosomal and cytoplasmic membranes. The second protein, apolipoprotein A-IV (apoA-IV), turned out to be an early marker of kidney impairment not only in patients with primary CKD but also in individuals from the general population. Genetic studies provided strong support of a causal effect of kidney function on apoA-IV concentrations.

SUMMARY

These two apolipoproteins have very distinct properties. Apolipoprotein L1 is causally involved in the development of nondiabetic CKD in African Americans. In contrast, apoA-IV is an early marker for kidney impairment.

Modified Lipids and Lipoproteins in Chronic Kidney Disease: A New Class of Uremic Toxins

Chronic kidney disease (CKD) is associated with an enhanced oxidative stress and deep modifications in lipid and lipoprotein metabolism. First, many oxidized lipids accumulate in CKD and were shown to exert toxic effects on cells and tissues. These lipids are known to interfere with many cell functions and to be pro-apoptotic and pro-inflammatory, especially in the cardiovascular system. Some, like F2-isoprostanes, are directly correlated with CKD progression. Their accumulation, added to their noxious effects, rendered their nomination as uremic toxins credible. Similarly, lipoproteins are deeply altered by CKD modifications, either in their metabolism or composition. These impairments lead to impaired effects of HDL on their normal effectors and may strongly participate in accelerated atherosclerosis and failure of statins in end-stage renal disease patients. This review describes the impact of oxidized lipids and other modifications in the natural history of CKD and its complications. Moreover, this review focuses on the modifications of lipoproteins and their impact on the emergence of cardiovascular diseases in CKD as well as the appropriateness of considering them as actual mediators of uremic toxicity.

Human Genetics and the Causal Role of Lipoprotein(a) for Various Diseases

Lipoprotein(a) [Lp(a)] is a highly atherogenic lipoprotein that is under strong genetic control by the LPA gene locus. Genetic variants including a highly polymorphic copy number variation of the so called kringle IV repeats at this locus have a pronounced influence on Lp(a) concentrations. High concentrations of Lp(a) as well as genetic variants which are associated with high Lp(a) concentrations are both associated with cardiovascular disease which very strongly supports causality between Lp(a) concetrations and cardiovascular disease. This method of using a genetic variant that has a pronounced influence on a biomarker to support causality with an outcome is called Mendelian randomization approach and was applied for the first time two decades ago with data from Lp(a) and cardiovascular disease. This approach was also used to demonstrate a causal association between high Lp(a) concentrations and aortic valve stenosis, between low concentrations and type-2 diabetes mellitus and to exclude a causal association between Lp(a) concentrations and venous thrombosis. Considering the high frequency of these genetic variants in the population makes Lp(a) the strongest genetic risk factor for cardiovascular disease identified so far. Promising drugs that lower Lp(a) are on the horizon but their efficacy in terms of reducing clinical outcomes still has to be shown.

Effects of Atorvastatin on Lp(a) and Lipoprotein Profiles in Hemodialysis Patients

Background:

Dialysis patients have many underlying traditional and nontraditional risk factors that may predispose them to a high prevalence of cardiovascular disease. The effects of statins (eg, atorvastatin) on altering nontraditional lipoprotein measures in dialysis patients have not been extensively investigated.

Objective:

To evaluate the efficacy of atorvastatin compared with a control group in inducing changes in lipoprotein(a) [Lp(a)], apolipoprotein (Apo) A-1, Apo-B, and fibrinogen levels, as well as the conventional lipoprotein profile, in hemodialysis patients over 36 weeks; secondary objectives were to assess changes in C-reactive protein, albumin, and safety measures.

Methods:

Forty-five hemodialysis patients with low-density lipoprotein cholesterol (LDL-C) levels greater than 100 mg/dL were randomized to parallel groups: atorvastatin (n = 19) or no treatment (n = 26). The atorvastatin dose was titrated from 10 mg to achieve an LDL-C goal of 100 mg/dL or less and therapy was continued for 36 weeks. Biochemical and lipoprotein laboratory tests for efficacy outcomes were obtained at baseline, 12 weeks, and 36 weeks.

Results:

The atorvastatin group exhibited clinically significant reductions (mean ± SD) compared with controls in total cholesterol (–21.7 ± 41.7 vs –3.2 ± 40.0 mg/dL, respectively; p = 0.017) and LDL-C (–13.1 ± 32.0 vs –1.1 ± 38.4 mg/dL. respectively; p = 0.056) levels, as well as Lp(a) (–10.6 ± 27 vs 3.5 ± 17.8 mg/dL, respectively; p = 0.046). Statistical analyses included analysis of variance on ranked measures for multivariable modeling and paired t-test to determine changes in efficacy measures between baseline and 36 weeks within groups.

Conclusions:

Atorvastatin was safe and effective in reducing Lp(a), total cholesterol, and LDL-C levels. Given the prevalence of atherosclerosis in hemodialysis patients, therapy aimed at reducing traditional and nontraditional risk factors may be beneficial.

New Insight into Atherosclerosis in Hemodialysis Patients: Overexpression of Scavenger Receptor and Macrophage Colony-Stimulating Factor Genes

BACKGROUND

Scavenger receptors (SRs) play a pivotal role in atherogenesis. The mechanism of atherosclerosis, which is specific to hemodialysis (HD) patients, was studied on the basis of SR gene expressions.

METHODS

The gene expressions of SR type A (SR-A) and CD36 were studied in peripheral monocytes by real-time reverse transcription polymerase chain reaction. Data were compared between HD (n = 30) and age-matched control subjects (n = 10). Serum levels of macrophage colony-stimulating factor (M-CSF) were measured with enzyme-linked immunosorbent assay to test its role in SR expression. The statistical differences and associations between two continuous variables were assessed using the Mann-Whitney U test and Pearson's correlation coefficient, respectively.

RESULTS

The relative quantities of SR mRNAs were significantly greater in HD patients than in controls [median (interquartile range): SR-A, 1.67 (0.96-2.76) vs. 0.90 (0.60-1.04), p = 0.0060; CD36, 1.09 (0.88-1.74) vs. 0.74 (0.64-0.99), p = 0.0255]. The serum concentration of M-CSF was significantly higher in HD patients than in controls [1, 121 (999-1,342) vs. 176 (155-202) pg/ml, p < 0.0001]. In addition, the relative quantity of M-CSF mRNA was significantly greater in HD patients than in controls [0.79 (0.42-1.53) vs. 0.42 (0.28-0.66), p = 0.0392]. The serum M-CSF levels were positively correlated with both the relative quantity of SR-A mRNA (r² = 0.1681, p = 0.0086) and that of CD36 mRNA (r² = 0.1202, p = 0.0284) in all subjects (n = 40).

CONCLUSION

HD patients are predisposed to atherosclerosis as a consequence of their enhanced monocyte SR expressions. SRs and M-CSF are potential therapeutic targets for atherosclerosis in this high-risk population.

A genome-wide association meta-analysis on apolipoprotein A-IV concentrations

Apolipoprotein A-IV (apoA-IV) is a major component of HDL and chylomicron particles and is involved in reverse cholesterol transport. It is an early marker of impaired renal function. We aimed to identify genetic loci associated with apoA-IV concentrations and to investigate relationships with known susceptibility loci for kidney function and lipids. A genome-wide association meta-analysis on apoA-IV concentrations was conducted in five population-based cohorts (n = 13,813) followed by two additional replication studies (n = 2,267) including approximately 10 M SNPs. Three independent SNPs from two genomic regions were significantly associated with apoA-IV concentrations: rs1729407 near APOA4 (P = 6.77 × 10 ^{-  44}), rs5104 in APOA4 (P = 1.79 × 10^-24) and rs4241819 in KLKB1 (P = 5.6 × 10^-14). Additionally, a look-up of the replicated SNPs in downloadable GWAS meta-analysis results was performed on kidney function (defined by eGFR), HDL-cholesterol and triglycerides. From these three SNPs mentioned above, only rs1729407 showed an association with HDL-cholesterol (P = 7.1 × 10 ^{-  07}). Moreover, weighted SNP-scores were built involving known susceptibility loci for the aforementioned traits (53, 70 and 38 SNPs, respectively) and were associated with apoA-IV concentrations. This analysis revealed a significant and an inverse association for kidney function with apoA-IV concentrations (P = 5.5 × 10^-05). Furthermore, an increase of triglyceride-increasing alleles was found to decrease apoA-IV concentrations (P = 0.0078). In summary, we identified two independent SNPs located in or next the APOA4 gene and one SNP in KLKB1 The association of KLKB1 with apoA-IV suggests an involvement of apoA-IV in renal metabolism and/or an interaction within HDL particles. Analyses of SNP-scores indicate potential causal effects of kidney function and by lesser extent triglycerides on apoA-IV concentrations.

Lipoprotein (a): impact by ethnicity and environmental and medical conditions

Levels of lipoprotein (a) [Lp(a)], a complex between an LDL-like lipid moiety containing one copy of apoB, and apo(a), a plasminogen-derived carbohydrate-rich hydrophilic protein, are primarily genetically regulated. Although stable intra-individually, Lp(a) levels have a skewed distribution inter-individually and are strongly impacted by a size polymorphism of the LPA gene, resulting in a variable number of kringle IV (KIV) units, a key motif of apo(a). The variation in KIV units is a strong predictor of plasma Lp(a) levels resulting in stable plasma levels across the lifespan. Studies have demonstrated pronounced differences across ethnicities with regard to Lp(a) levels and some of this difference, but not all of it, can be explained by genetic variations across ethnic groups. Increasing evidence suggests that age, sex, and hormonal impact may have a modest modulatory influence on Lp(a) levels. Among clinical conditions, Lp(a) levels are reported to be affected by kidney and liver diseases.

Etiology and management of dyslipidemia in children with chronic kidney disease and end-stage renal disease

Lipids are essential components of cell membranes, contributing to cell fuel, myelin formation, subcellular organelle function, and steroid hormone synthesis. Children with chronic kidney disease (CKD) and end-stage renal disease (ESRD) exhibit various co-morbidities, including dyslipidemia. The prevalence of dyslipidemias in children with CKD and ESRD is high, being present in 39-65% of patients. Elevated lipid levels in children without renal disease are a risk factor for cardiovascular disease (CVD), while the risk for CVD in pediatric CKD/ESRD is unclear. The pathogenesis of dyslipidemia in CKD features various factors, including increased levels of triglycerides, triglyceride-rich lipoproteins, apolipoprotein C3 (ApoC-III), decreased levels of cholesterylester transfer protein and high-density lipoproteins, and aberrations in serum very low-density and intermediate-density lipoproteins. If initial risk assessment indicates that a child with advanced CKD has 2 or more co-morbidities for CVD, first-line treatment should consist of non-pharmacologic management such as therapeutic lifestyle changes and dietary counseling. Pharmacologic treatment of dyslipidemia may reduce the incidence of CVD in children with CKD/ESRD, but randomized trials are lacking. Statins are the only class of lipid-lowering drugs currently approved by the U.S. Food and Drug Administration (FDA) for use in the pediatric population. FDA-approved pediatric labeling for these drugs is based on results from placebo-controlled trial results, showing 30-50% reductions in baseline low-density lipoprotein cholesterol. Although statins are generally well tolerated in adults, a spectrum of adverse events has been reported with their use in both the clinical trial and post-marketing settings.

Association between apolipoprotein A-IV concentrations and chronic kidney disease in two large population-based cohorts: results from the KORA studies

BACKGROUND

Apolipoprotein A-IV (apoA-IV) is an anti-atherogenic and antioxidative glycoprotein. Plasma apoA-IV levels are elevated in patients with primary chronic kidney disease (CKD) or renal failure. The association between apoA-IV and kidney function has not been investigated in the general population; therefore, we analysed this relationship in two large population-based cohorts.

METHODS

Plasma apoA-IV concentrations were measured in the Cooperative Health Research in the Region of Augsburg (KORA) F3 (n = 3159) and KORA F4 (n = 3061) studies. CKD was defined by the serum creatinine-estimated glomerular filtration rate (eGFR) and/or urine albumin-to-creatinine ratio.

RESULTS

Mean (±SD) apoA-IV concentration was 17.3 ± 4.7 mg dL(-1) in KORA F3 and 15.3 ± 4.3 mg dL(-1) in KORA F4. Fully adjusted linear mixed models revealed a significant association between apoA-IV concentration and lower eGFR in the third and fourth versus the first quartile of apoA-IV (β = -1.78 mL min(-1) /1.73 m², P = 0.0003 and β = -5.09 mL min(-1) /1.73 m², P = 2.83 × 10(-23) , respectively). ApoA-IV was significantly associated with an eGFR of <60 mL min(-1) /1.73 m², which was observed in 601 of the 6220 study participants [odds ratio (OR) 1.46, P = 0.03 and OR 3.47, P = 6.84 × 10(-15) for the third and fourth vs. the first quartile of apoA-IV, respectively]. Adding apoA-IV (fourth vs. first quartile) to the fully adjusted model significantly improved discrimination of eGFR <60 mL min(-1) /1.73 m² in KORA F3 [integrated discrimination improvement (IDI) 0.03, P = 1.30 × 10(-7) ] and KORA F4 (IDI 0.04, P = 1.32 × 10(-9) ) beyond classical risk factors for CKD.

CONCLUSION

The present analysis in two population-based cohorts revealed that high plasma apoA-IV concentrations are strongly associated with low kidney function defined by eGFR independent of major CKD risk factors. ApoA-IV appears to be an early marker of impaired kidney function.

IL-6 blockade by monoclonal antibodies inhibits apolipoprotein (a) expression and lipoprotein (a) synthesis in humans

Lipoprotein (a) [Lp(a)] is a highly atherogenic lipid particle. Although earlier reports suggested that Lp(a) levels are mostly determined by genetic factors, several recent studies have revealed that Lp(a) induction is also caused by chronic inflammation. Therefore, we aimed to examine whether cytokine blockade by monoclonal antibodies may inhibit Lp(a) metabolism. We found that interleukin 6 (IL-6) blockade by tocilizumab (TCZ) reduced Lp(a) while TNF-α-inhibition by adalimumab in humans had no effect. The specificity of IL-6 in regulating Lp(a) was further demonstrated by serological measurements of human subjects (n = 1,153) revealing that Lp(a) levels are increased in individuals with elevated serum IL-6. Transcriptomic analysis of human liver biopsies (n = 57) revealed typical IL-6 response genes being correlated with the LPA gene expression in vivo. On a molecular level, we found that TCZ inhibited IL-6-induced LPA mRNA and protein expression in human hepatocytes. Furthermore, examination of IL-6-responsive signal transducer and activator of transcription 3 binding sites within the LPA promoter by reporter gene assays, promoter deletion experiments, and electrophoretic mobility shift assay analysis showed that the Lp(a)-lowering effect of TCZ is specifically mediated via a responsive element at -46 to -40. Therefore, IL-6 blockade might be a potential therapeutic option to treat elevated Lp(a) serum concentrations in humans and might be a noninvasive alternative to lipid apheresis in the future.

The lipid story in chronic kidney disease: a long story with a happy end?

Cardiovascular (CV) morbidity and mortality increase with the severity of kidney disease, reaching 30 times higher mortality rates in dialysis patients compared with the general population. Although dyslipidemia is a well-established CV risk factor in the general population, the relationship between lipid disorders and CV risk in patients with chronic kidney disease (CKD) is less clear. Despite the clear evidence that statins reduce the risk of atherosclerotic events and death from cardiac causes in individuals without CKD, the use of statins in patients with kidney disease is significantly less frequent. For a long time, one of the explanations was the lack of a prospective, randomized, controlled study designed specifically to CKD patients. After recent publication of the data from Study of Heart and Renal Protection trial, given the safety and potential efficacy of statins, this lipid-lowering treatment should be administered more frequently to individuals with CKD stage 1–4, as well as those undergoing dialysis.

Causes and consequences of lipoprotein(a) abnormalities in kidney disease

Lipoprotein(a) is one of the strongest genetically determined risk factors for cardiovascular disease, and patients with chronic kidney disease have major disturbances in lipoprotein(a) metabolism. Concentrations are increased and are influenced by glomerular filtration rate (GFR) and the amount of proteinuria. The reason for this elevation can be increased synthesis, as is the case for patients with nephrotic syndrome or those treated by peritoneal dialysis. In hemodialysis patients, a catabolic block is the reason for this elevation. The elevated concentrations might contribute to the tremendous cardiovascular risk in this particular population. In particular, the genetically determined small apolipoprotein(a) isoforms are associated with an increased risk for cardiovascular events and total mortality.

Lipoprotein kinetics in male hemodialysis patients treated with atorvastatin

BACKGROUND AND OBJECTIVES

In vivo metabolism of atherogenic apolipoprotein B (apoB)-containing lipoproteins is severely impaired in patients undergoing hemodialysis (HD), resulting in markedly prolonged residence times of these particles. It is unclear whether treatment with statins improves LDL kinetics in HD patients as is known for the general population. Therefore, this kinetic study assessed apoB-containing lipoproteins in these patients.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

Kinetic measures were analyzed with stable-isotope technology in six men undergoing HD before and after 3 months of daily administration of 10 mg of atorvastatin. Patients were 18-65 years of age, had LDL cholesterol levels between 90 and 200 mg/dl, and had been treated with HD for >6 months. They consumed a standardized isocaloric diet for 3 days before analysis. Fractional catabolic rates (FCRs) and production rates of very-low-density lipoprotein (VLDL)-apoB, intermediate-density lipoprotein-apoB, and LDL-apoB were determined using multicompartment modeling after plasma lipoprotein separation, precipitation of apoB, and determination of tracer-to-tracee ratios using mass spectrometry.

RESULTS

Plasma concentrations of VLDL- and LDL-apoB were significantly lower (mean ± SD, 7.77±2.62 versus 11.27±6.15 mg/dl, P<0.05; 56.9±23.9 versus 84.0±21.1 mg/dl, P=0.03) and their FCRs were significantly higher (7.20±3.08 versus 5.20±2.98 days(-1), P<0.05; 0.851±0.772 versus 0.446±0.232 days(-1), P<0.05) after 3 months of atorvastatin treatment. Accordingly, the residence times in plasma of VLDL- and LDL-apoB were significantly lower after treatment (0.14 versus 0.19 day and 1.2 versus 2.2 days, respectively).

CONCLUSION

Lower plasma concentrations and improved kinetics of atherogenic lipoproteins were observed in HD patients after administration of low-dose atorvastatin.

Lipoprotein(a): resurrected by genetics

Plasma lipoprotein(a) [Lp(a)] is a quantitative genetic trait with a very broad and skewed distribution, which is largely controlled by genetic variants at the LPA locus on chromosome 6q27. Based on genetic evidence provided by studies conducted over the last two decades, Lp(a) is currently considered to be the strongest genetic risk factor for coronary heart disease (CHD). The copy number variation of kringle IV in the LPA gene has been strongly associated with both Lp(a) levels in plasma and risk of CHD, thereby fulfilling the main criterion for causality in a Mendelian randomization approach. Alleles with a low kringle IV copy number that together have a population frequency of 25-35% are associated with a doubling of the relative risk for outcomes, which is exceptional in the field of complex genetic phenotypes. The recently identified binding of oxidized phospholipids to Lp(a) is considered as one of the possible mechanisms that may explain the pathogenicity of Lp(a). Drugs that have been shown to lower Lp(a) have pleiotropic effects on other CHD risk factors, and an improvement of cardiovascular endpoints is up to now lacking. However, it has been established in a proof of principle study that lowering of very high Lp(a) by apheresis in high-risk patients with already maximally reduced low-density lipoprotein cholesterol levels can dramatically reduce major coronary events.

Apolipoprotein A-IV concentrations and clinical outcomes in haemodialysis patients with type 2 diabetes mellitus--a post hoc analysis of the 4D Study

BACKGROUND

Apolipoprotein A-IV (apoA-IV) is an anti-atherogenic and anti-oxidative plasma glycoprotein involved in reverse cholesterol transport. The aim of this study was to examine the association between apoA-IV and all-cause mortality, cardiovascular endpoints and parameters of protein-energy wasting and nutrition in haemodialysis patients.

METHODS

This post hoc analysis was performed in the German Diabetes Dialysis Study (4D Study) evaluating atorvastatin in 1255 haemodialysis patients with type 2 diabetes mellitus, followed for a median of 4 years. The association between apoA-IV and relevant outcomes was analysed using Cox proportional hazards regression analyses. Body mass index (BMI) was used as a marker of protein-energy wasting. In addition, a definition of extended wasting was applied, combining median values of BMI, serum albumin, creatinine and sensitive C-reactive protein, to classify patients.

RESULTS

Mean (±SD) apoA-IV concentration was 49.8 ± 14.2 mg dL(-1). Age- and gender-adjusted apoA-IV concentrations were strongly associated with the presence of congestive heart failure at baseline [odds ratio = 0.81, 95% confidence interval (CI) 0.74-0.88 per 10 mg dL(-1) increase; P < 0.001). During the prospective follow-up, the strongest association was found for all-cause mortality [hazard ratio (HR) = 0.89, 95% CI 0.85-0.95, P = 0.001), which was mainly because of patients with BMI > 23 kg m(-2) (HR = 0.87, 95% CI 0.82-0.94, P < 0.001) and those in the nonwasting group according to the extended definition (HR = 0.89, 95% CI 0.84-0.96, P = 0.001). This association remained significant after additionally adjusting for parameters associated with apoA-IV at baseline. Further associations were observed for sudden cardiac death. ApoA-IV was less strongly associated with atherogenic events such as myocardial infarction.

CONCLUSIONS

Low apoA-IV levels seem to be a risk predictor of all-cause mortality and sudden cardiac death. This association might be modified by nutritional status.

Biomarkers in chronic kidney disease: a review

Chronic kidney disease (CKD) is a major public health problem. The classification of CKD by KDOQI and KDIGO and the routine eGFR reporting have resulted in increased identification of CKD. It is important to be able to identify those at high risk of CKD progression and its associated cardiovascular disease (CVD). Proteinuria is the most sensitive marker of CKD progression in clinical practice, especially when combined with eGFR, but these have limitations. Hence, early, more sensitive, biomarkers are required. Recently, promising biomarkers have been identified for CKD progression and its associated CVD morbidity and mortality. These may be more sensitive biomarkers of kidney function, the underlying pathophysiological processes, and/or cardiovascular risk. Although there are some common pathways to CKD progression, there are many primary causes, each with its own specific pathophysiological mechanism. Hence, a panel measuring multiple biomarkers including disease-specific biomarkers may be required. Large, longitudinal observational studies are needed to validate candidate biomarkers in a broad range of populations prior to implementation into routine CKD management. Recent renal biomarkers discovered include neutrophil gelatinase-associated lipocalin, kidney injury molecule-1, and liver-type fatty acid-binding protein. Although none are ready for use in clinical practice, it is timely to review the role of such biomarkers in predicting CKD progression and/or CVD risk in CKD.