Statins in the management of dyslipidemia associated with chronic kidney disease

The prevalence of dyslipidemia in patients on hemodialysis: a cross-sectional study from Syria

Dyslipidemia is an established risk factor for cardiovascular disease (CVD), which is the main cause of mortality among haemodialysis (HD) patients. We investigate the prevalence and characteristics of dyslipidemia in HD patients. Also, we aimed to study the prediction scores; Framingham risk score (FRS), and the atherosclerotic cardiovascular disease risk score; among this population.

METHODS

One hundred fifty-three HD patients were enroled in this retrospective cross-sectional study from two HD centres in Syria, from March 2021 to March 2022. Dyslipidemia is considered as follows; hyper-total cholesterol (TC) (≥200 mg/dl), hyper-triglycerides (TG), (≥150 mg/dl), hyper-low-density lipoprotein (LDL) (≥100 mg/dl), hypo-high-density lipoprotein (HDL) (<40 mg/dl), hyper-Non-HDL (≥130 mg/dl).

RESULTS

The most prevalent dyslipidemic parameter was low HDL (72.50%) followed by increased TGs (37.30%). TC, LDL, HDL, and Non-HDL showed differences between males and females (P=0.001, 0.015, 0.024, and 0.025; respectively). These parameters were higher in females. History of CVD showed associations with TC, LDL, HDL, and non-HDL (P=0.003, 0.007, 0.004, and 0.004; respectively). Additionally, statins showed effects on TC, LDL, and non-HDL (P=0.003, 0.0002, and 0.002; respectively); however, no relation with TG and HDL (P=0.9 and 0.4). HDL level showed differences in low (7.5%) and intermediate (10%) FRS (P=0.01 and 0.028; respectively); however, it did not show a difference in high (20%) FRS (P=0.68). The lipids profile did not show differences in different thresholds of atherosclerotic cardiovascular disease scores.

CONCLUSION

The prevalence of dyslipidemia was high in HD patients in Syria. All lipid parameters except TG showed differences between males and females. Comparisons of lipid parameters with CVD risk stratifications support the need for further studies to prove the benefits of these scores in CVD prediction among the dialysis population.

Head-to-Head Comparison of Oxidative Stress Biomarkers for All-Cause Mortality in Hemodialysis Patients

Oxidative stress (OS) presents even in the early chronic kidney disease (CKD) stage and is exacerbated in patients with end-stage renal disease (ESRD) undergoing maintenance hemodialysis (MHD). There is still a debate over the association between oxidative stress and mortality. Our study aims to compare head-to-head the prognostic value of different oxidative markers for all-cause mortality in hemodialysis (HD) patients. We thus enrolled 347 patients on HD in this prospective study. Four OS biomarkers were measured (carbonyl proteins, myeloperoxidase (MPO), advanced oxidation protein products (AOPPs), and oxidized low-density lipoprotein (ox-LDL)). During the 60-month follow-up period, 9 patients have been lost to follow-up and 168 (48.4%) patients died. Concerning the oxidative stress (ox-stress) byproducts, carbonyl proteins were lower in survivors (105.40 ng/mL (IQR 81.30−147.85) versus 129.65 ng/mL (IQR 93.20−180.33); p < 0.001), with similar results for male patients (103.70 ng/mL (IQR 76.90−153.33) versus 134.55 ng/mL (IQR 93.95−178.68); p = 0.0014). However, there are no significant differences in MPO, AOPP, and ox-LDL between the two groups. Kaplan−Meier survival analysis indicated that patients in the higher carbonyl proteins concentration (>117.85 ng/mL group) had a significantly lower survival rate (log-rank test, p < 0.001). Univariate Cox regression analysis showed a positive correlation between carbonyl proteins and all-cause mortality in the higher and lower halves. Even after adjustment for conventional risk factors, it remained a statistically significant predictor of an increased risk of death in MHD. Univariate Cox regression analysis of MPO showed that continuous MPO and Log MPO were significantly associated with all-cause mortality, except for binary MPO (divided according to the median of MPO). Multivariate Cox analysis for MPO showed that the mortality prediction remains significant after adjusting for multiple factors. In conclusion, not all ox-stress biomarkers predict all-cause mortality in HD patients to a similar extent. In the present study, carbonyl proteins and MPO are independent predictors of all-cause mortality in HD patients, whereas AOPPs and oxLDL are clearly not associated with all-cause mortality in HD patients.

Signaling pathways of chronic kidney diseases, implications for therapeutics

Chronic kidney disease (CKD) is a chronic renal dysfunction syndrome that is characterized by nephron loss, inflammation, myofibroblasts activation, and extracellular matrix (ECM) deposition. Lipotoxicity and oxidative stress are the driving force for the loss of nephron including tubules, glomerulus, and endothelium. NLRP3 inflammasome signaling, MAPK signaling, PI3K/Akt signaling, and RAAS signaling involves in lipotoxicity. The upregulated Nox expression and the decreased Nrf2 expression result in oxidative stress directly. The injured renal resident cells release proinflammatory cytokines and chemokines to recruit immune cells such as macrophages from bone marrow. NF-κB signaling, NLRP3 inflammasome signaling, JAK-STAT signaling, Toll-like receptor signaling, and cGAS-STING signaling are major signaling pathways that mediate inflammation in inflammatory cells including immune cells and injured renal resident cells. The inflammatory cells produce and secret a great number of profibrotic cytokines such as TGF-β1, Wnt ligands, and angiotensin II. TGF-β signaling, Wnt signaling, RAAS signaling, and Notch signaling evoke the activation of myofibroblasts and promote the generation of ECM. The potential therapies targeted to these signaling pathways are also introduced here. In this review, we update the key signaling pathways of lipotoxicity, oxidative stress, inflammation, and myofibroblasts activation in kidneys with chronic injury, and the targeted drugs based on the latest studies. Unifying these pathways and the targeted therapies will be instrumental to advance further basic and clinical investigation in CKD.

HDL and Kidney Diseases

Serum lipid profiles, as well as HDL can be altered in patients with kidney diseases. There are various types of kidney diseases, including nephrotic syndrome and chronic kidney disease. In patients with nephrotic syndrome, plasma levels of HDL cholesterol and ApoA-I were within or below the normal limits. The HDL cholesterol: total cholesterol ratio decreased compared to healthy individuals. In patients with chronic kidney disease (CKD), reverse cholesterol transport function of HDL is impaired, and CKD also affects the composition and function of HDL. Cardiovascular disease (CVD) is the severe complication of CKD. Furthermore, HDL might also be a potential target for the prevention of cardiovascular complications associated 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.

The intersection of Mineralocorticoid Receptor (MR) activation and the FGF23 - Klotho cascade. A Duopoly that promotes renal and cardiovascular injury

The nexus of CKD and cardiovascular disease (CVD) amplifies the morbidity and mortality of CKD, emphasizing the need for defining and establishing therapeutic initiatives to modify and abrogate the progression of CKD and concomitant CV risks. In addition to the traditional CV risk factors, disturbances of mineral metabolism are specific risk factors that contribute to the excessive CV mortality in patients with CKD. These risk factors include dysregulations of circulating factors that modulate phosphate metabolism including fibroblast growth factor 23 (FGF23) and soluble Klotho. Reduced circulating levels and suppressed renal klotho expression may be associated with adverse outcomes in CKD patients. While elevated circulating concentrations or locally produced FGF23 in the strained heart exert pro-hypertrophic mechanisms on the myocardium, Klotho attenuates tissue fibrosis, progression of CKD, cardiomyopathy, endothelial dysfunction, vascular stiffness, and vascular calcification. Mineralocorticoid receptor (MR) activation in non-classical targets, mediated by aldosterone and other ligands, amplifies CVD in CKD. In concert, we detail how the interplay of elevated FGF23, activation of the MR, and concomitant reductions of circulating Klotho in CKD, may potentiate each other's deleterious effects on kidney and the heart, thereby contributing to the initiation and progression of kidney and cardiac functional deterioration, acting through multipronged albeit complementary mechanistic pathways.

Statin initiation and all-cause mortality in incident statin-naïve dialysis patients

BACKGROUND AND AIMS

Cardiovascular disease is the main cause of death in end-stage kidney disease (ESKD) patients. We aimed to explore the association between statin initiation after starting dialysis and all-cause mortality in statin-naïve ESKD patients.

METHODS

We analyzed nationwide claims data of incident dialysis patients from 2010 to 2017 in South Korea. Patients who had previous cardiovascular events or were administered statins before dialysis were excluded. The study group included dialysis patients receiving statins within 1 year after dialysis initiation. The control group was organized after propensity-score matching with age, sex, time of dialysis initiation, and underlying diabetes mellitus and hypertension. The main outcomes were all-cause mortality and major cardiovascular events.

RESULTS

We included 1596 patients who started statin treatment and 1:1 matched statin-nonusers. During the 9438 person-year follow-up, 468 deaths and 264 major adverse cardiovascular events (MACEs) occurred. Statin initiation was associated with a reduced risk of all-cause mortality (adjusted hazard ratio (aHR) 0.72, 95% confidence interval (CI) 0.60-0.87, p = 0.001), but not with MACE incidence (aHR 1.06, 95% CI 0.83-1.36, p = 0.62). In particular, patients prescribed the recommended dosage of statins according to the Kidney Disease Improving Global Outcomes guidelines showed the lowest mortality risk (aHR 0.55, 95% CI 0.40-0.75, p < 0.001).

CONCLUSIONS

Statin initiation was associated with lower risk of all-cause mortality in statin-naïve ESKD patients. As indication bias may be present in observational study setting, further prospective studies are warranted to validate the association of statin initiation with mortality in incident dialysis cases.

Podocyte Lipotoxicity in CKD

CKD represents the ninth most common cause of death in the United States but, despite this large health burden, treatment options for affected patients remain limited. To remedy this, several relevant pathways have been identified that may lead to novel therapeutic options. Among them, altered renal lipid metabolism, first described in 1982, has been recognized as a common pathway in clinical and experimental CKD of both metabolic and nonmetabolic origin. This observation has led many researchers to investigate the cause of this renal parenchyma lipid accumulation and its downstream effect on renal structure and function. Among key cellular components of the kidney parenchyma, podocytes are terminally differentiated cells that cannot be easily replaced when lost. Clinical and experimental evidence supports a role of reduced podocyte number in the progression of CKD. Given the importance of the podocytes in the maintenance of the glomerular filtration barrier and the accumulation of TG and cholesterol-rich lipid droplets in the podocyte and glomerulus in kidney diseases that cause CKD, understanding the upstream cause and downstream consequences of lipid accumulation in podocytes may lead to novel therapeutic opportunities. In this review, we hope to consolidate our understanding of the causes and consequences of dysregulated renal lipid metabolism in CKD development and progression, with a major focus on podocytes.

Kidney-secreted erythropoietin lowers lipidemia via activating JAK2-STAT5 signaling in adipose tissue

Background

Dyslipidemia is commonly observed in various kidney diseases, renal specific secreted erythropoietin (EPO) may participate in this process. However, how this process is regulated remains elusive.

Method

Dyslipidemia was evaluated in chronic kidney disease and ischemia kidney injury animal model. Primary cultured adipocytes were harvested to investigate the lipid metabolic effect of EPO. Lipidemia was evaluated in EPO treated animals. Blood samples from cardiac surgery-induced kidney injury patient were collected to assess correlationship between EPO and lipidemia.

Findings

We found a decrease in secreted EPO and hypertriglyceridemia in chronic kidney disease (CKD) mice. In contrast, in renal ischemia animal model, increased EPO triggered by hypoxia signaling activation, was accompanied by decreased triglyceride (TG) in serum. Mechanistically, circulating EPO modulated JAK2-STAT5 signaling, which in turn enhanced lipid catabolism in peripheral adipose tissue and contributed to dysregulated lipidemia. Delivering of recombinant EPO into both wild type and CKD mice suppressed TG in serum by accelerating lipid catabolism in adipose tissue. In a cohort of patients diagnosed with acute kidney injury after cardiopulmonary bypass surgery, the decreased TG and cholesterol negatively correlated with increased EPO in serum.

Interpretation

This study depicted a new mechanism by which renal secreted EPO controlled lipidemia in kidney diseases including chronic kidney disease. Circulating EPO stimulated lipid catabolism by targeting JAK2-STATA5 signaling in peripheral adipose tissue, providing new therapeutic target for dyslipidemia treatment.

Funding

This work was supported by grants from the National Natural Science Foundation of China (Nos. 81700640 and 81970608).

Lipid management in patients with chronic kidney disease

An increased risk of cardiovascular disease, independent of conventional risk factors, is present even at minor levels of renal impairment and is highest in patients with end-stage renal disease (ESRD) requiring dialysis. Renal dysfunction changes the level, composition and quality of blood lipids in favour of a more atherogenic profile. Patients with advanced chronic kidney disease (CKD) or ESRD have a characteristic lipid pattern of hypertriglyceridaemia and low HDL cholesterol levels but normal LDL cholesterol levels. In the general population, a clear relationship exists between LDL cholesterol and major atherosclerotic events. However, in patients with ESRD, LDL cholesterol shows a negative association with these outcomes at below average LDL cholesterol levels and a flat or weakly positive association with mortality at higher LDL cholesterol levels. Overall, the available data suggest that lowering of LDL cholesterol is beneficial for prevention of major atherosclerotic events in patients with CKD and in kidney transplant recipients but is not beneficial in patients requiring dialysis. The 2013 Kidney Disease: Improving Global Outcomes (KDIGO) Clinical Practice Guideline for Lipid Management in CKD provides simple recommendations for the management of dyslipidaemia in patients with CKD and ESRD. However, emerging data and novel lipid-lowering therapies warrant some reappraisal of these recommendations.

Elevated Triglycerides (≥150 mg/dL) and High Triglycerides (200–499 mg/dL) Are Significant Predictors of Hospitalization for New-Onset Kidney Disease: A Real-World Analysis of High-Risk Statin-Treated Patients

Background: Dyslipidemia in kidney disease (KD) involves increased levels of triglycerides (TG) and TG-rich lipoproteins, with only minor changes in low-density lipoprotein cholesterol. The increasing prevalence of diabetic KD and the shared atherogenic lipid profile between KD and diabetes underscore the importance of understanding dyslipidemia in these patients. Previous studies suggest an association between elevated TG and new-onset KD. Additional data are needed to better define the relationship between hypertriglyceridemia and new-onset KD. Objective: To evaluate the real-world impact of elevated and high TG on risk of KD in high-risk statin-treated patients. Methods: This retrospective administrative claims analysis of the Optum Research Database included statin-treated patients (age ≥45 years) with diabetes and/or atherosclerotic cardiovascular disease who were followed for ≥6 months. Cohorts included patients with elevated TG (≥150 mg/dL; n = 27,471) or high TG (200–499 mg/dL; subgroup of elevated TG cohort; n = 13,411), and a comparator cohort (TG <150 mg/dL and high-density lipoprotein cholesterol >40 mg/dL; n = 32,506). The probability of hospitalization for new-onset KD was calculated post hoc from multivariate analyses controlled for patient characteristics and comorbidities using a Cox proportional hazards model. Results: The rate of hospitalization for new-onset KD was 31% higher in the elevated-TG cohort (hazard ratio [HR], 1.311; 95% confidence interval [CI], 1.228–1.401; p < 0.001) and 45% higher in the high-TG cohort (HR, 1.451; 95% CI, 1.339–1.572; p < 0.001) compared with the respective comparator cohorts. Conclusions: In a real-world analysis of statin-treated patients with high cardiovascular risk, both elevated TG (≥150 mg/dL) and high TG (200–499 mg/dL) were significant predictors of hospitalization for new-onset KD, identifying hypertriglyceridemia as a potential KD risk factor.

Icosapent ethyl reduces atherogenic markers in high-risk statin-treated patients with stage 3 chronic kidney disease and high triglycerides

Objective: Patients with chronic kidney disease (CKD) have increased cardiovascular disease (CVD) risk, likely driven by atherogenic and inflammatory markers beyond low-density lipoprotein cholesterol (LDL-C). The objective of this hypothesis-generating post hoc subgroup analysis was to explore the effects of icosapent ethyl at 2 or 4 g/day (prescription pure ethyl ester of the omega-3 fatty acid eicosapentaenoic acid [EPA]) on atherogenic lipid, apolipoprotein, inflammatory parameters (high-sensitivity C-reactive protein [hsCRP], lipoprotein-associated phospholipase A₂ [Lp-PLA₂]), and oxidative parameters (oxidized-LDL [ox-LDL]) in statin-treated patients from ANCHOR with stage 3 CKD.Methods: The 12-week ANCHOR study evaluated icosapent ethyl in 702 statin-treated patients at increased CVD risk with triglycerides (TG) 200-499 mg/dL despite controlled LDL-C (40-99 mg/dL). This post-hoc analysis included patients from ANCHOR with stage 3 CKD (estimated glomerular filtration rate [eGFR] ≤60 mL/min/1.73 m² for ≥3 months) randomized to icosapent ethyl 4 g/day (n = 19), 2 g/day (n = 30), or placebo (n = 36).Results: At the prescription dose of 4 g/day, icosapent ethyl significantly reduced TG (-16.9%; P = 0.0074) and other potentially atherogenic lipids/lipoproteins, ox-LDL, hsCRP, and Lp-PLA₂, and increased plasma and red blood cell EPA levels (+879% and +579%, respectively; both P < 0.0001) versus placebo. Icosapent ethyl did not significantly alter eGFR or serum creatinine. Safety and tolerability were similar to placebo.Conclusions: In patients with stage 3 CKD at high CVD risk with persistent high TG despite statins, icosapent ethyl 4 g/day reduced potentially atherogenic and other cardiovascular risk factors without raising LDL-C, with safety similar to placebo. These findings suggest prospective investigation may be warranted.

Eicosapentaenoic Acid as a Potential Therapeutic Approach to Reduce Cardiovascular Risk in Patients with End-Stage Renal Disease on Hemodialysis: A Review

Background

Patients with end-stage renal disease on hemodialysis have excess cardiovascular disease (CVD) burden with substantially increased CV event rates compared with the general population.

Summary

Traditional interventions that, according to standard clinical guidelines, reduce CV risk such as antihypertensive therapy, diet, exercise, and statins are not similarly effective in the hemodialysis population. This raises the question of whether additional risk factors, such as enhanced inflammation and oxidative stress, may drive the increased CVD burden in hemodialysis patients. Eicosapentaenoic acid (EPA), an omega-3 polyunsaturated fatty acid, is incorporated into the atherosclerotic plaque as well as membrane phospholipid bilayers and produces beneficial effects on inflammatory and oxidative mechanisms involved in atherosclerotic plaque formation and progression. EPA levels and the ratio of EPA to the omega-6 polyunsaturated fatty acid arachidonic acid (AA) are reduced in hemodialysis patients. Serum EPA levels have been inversely correlated with proinflammatory cytokines, and the EPA/AA ratio has been inversely associated with CV events in hemodialysis cohorts. Three recent studies involving over 800 hemodialysis patients and follow-up of 2-3 years suggest that EPA therapy may improve clinical outcomes in this patient population as evidenced by significant reductions in cardiovascular mortality, all-cause mortality, and/or CV events.

Key Messages

Further studies with high-purity EPA are warranted in patients on hemodialysis, especially given the fact that other interventions including antihypertensives, diet, exercise, and statins have not provided meaningful benefit.

Disorders of lipid metabolism in nephrotic syndrome: mechanisms and consequences

Nephrotic syndrome results in hyperlipidemia and profound alterations in lipid and lipoprotein metabolism. Serum cholesterol, triglycerides, apolipoprotein B (apoB)-containing lipoproteins (very low-density lipoprotein [VLDL], immediate-density lipoprotein [IDL], and low-density lipoprotein [LDL]), lipoprotein(a) (Lp[a]), and the total cholesterol/high-density lipoprotein (HDL) cholesterol ratio are increased in nephrotic syndrome. This is accompanied by significant changes in the composition of various lipoproteins including their cholesterol-to-triglyceride, free cholesterol-to-cholesterol ester, and phospholipid-to-protein ratios. These abnormalities are mediated by changes in the expression and activities of the key proteins involved in the biosynthesis, transport, remodeling, and catabolism of lipids and lipoproteins including apoproteins A, B, C, and E; 3-hydroxy-3-methylglutaryl-coenzyme A reductase; fatty acid synthase; LDL receptor; lecithin cholesteryl ester acyltransferase; acyl coenzyme A cholesterol acyltransferase; HDL docking receptor (scavenger receptor class B, type 1 [SR-B1]); HDL endocytic receptor; lipoprotein lipase; and hepatic lipase, among others. The disorders of lipid and lipoprotein metabolism in nephrotic syndrome contribute to the development and progression of cardiovascular and kidney disease. In addition, by limiting delivery of lipid fuel to the muscles for generation of energy and to the adipose tissues for storage of energy, changes in lipid metabolism contribute to the reduction of body mass and impaired exercise capacity. This article provides an overview of the mechanisms, consequences, and treatment of lipid disorders in nephrotic syndrome.

D25V apolipoprotein C-III variant causes dominant hereditary systemic amyloidosis and confers cardiovascular protective lipoprotein profile

Apolipoprotein C-III deficiency provides cardiovascular protection, but apolipoprotein C-III is not known to be associated with human amyloidosis. Here we report a form of amyloidosis characterized by renal insufficiency caused by a new apolipoprotein C-III variant, D25V. Despite their uremic state, the D25V-carriers exhibit low triglyceride (TG) and apolipoprotein C-III levels, and low very-low-density lipoprotein (VLDL)/high high-density lipoprotein (HDL) profile. Amyloid fibrils comprise the D25V-variant only, showing that wild-type apolipoprotein C-III does not contribute to amyloid deposition in vivo. The mutation profoundly impacts helical structure stability of D25V-variant, which is remarkably fibrillogenic under physiological conditions in vitro producing typical amyloid fibrils in its lipid-free form. D25V apolipoprotein C-III is a new human amyloidogenic protein and the first conferring cardioprotection even in the unfavourable context of renal failure, extending the evidence for an important cardiovascular protective role of apolipoprotein C-III deficiency. Thus, fibrate therapy, which reduces hepatic APOC3 transcription, may delay amyloid deposition in affected patients.

Reduction of cardiovascular risk in chronic kidney disease by mineralocorticoid receptor antagonism

Cardiovascular disease is the leading cause of death and morbidity in people with chronic kidney disease, but there are few evidence-based treatments for reducing cardiovascular events in these patients. The failure of novel drug candidates to delay progression to end-stage renal disease and limit or abrogate cardiovascular morbidity and mortality has led to increased interest in a mineralocorticoid receptor (MR) antagonist-based treatment model to reduce cardiovascular risk in patients with chronic kidney disease and end-stage renal disease. Aldosterone concentrations and MR signalling are associated with an enhanced risk of cardiovascular injury and the incidence of sudden death, and MR blockade decreases the risk of cardiovascular events and sudden death in patients with reduced glomerular filtration rate. Since evidence from clinical trials shows that treatment with MR antagonists confers a morbidity and mortality advantage for patients with cardiovascular disorders, similar benefits might also accrue in patients with chronic kidney disease. Large prospective trials are urgently needed to answer this question. In this Review, I argue that despite differences in the pathophysiology and clinical features of cardiovascular disease in patients with and without chronic kidney disease, MR antagonists could provide cardiovascular benefit in patients with chronic kidney disease.

HDL abnormalities in nephrotic syndrome and chronic kidney disease

Normal HDL activity confers cardiovascular and overall protection by mediating reverse cholesterol transport and through its potent anti-inflammatory, antioxidant, and antithrombotic functions. Serum lipid profile, as well as various aspects of HDL metabolism, structure, and function can be profoundly altered in patients with nephrotic range proteinuria or chronic kidney disease (CKD). These abnormalities can, in turn, contribute to the progression of cardiovascular complications and various other comorbidities, such as foam cell formation, atherosclerosis, and/or glomerulosclerosis, in affected patients. The presence and severity of proteinuria and renal insufficiency, as well as dietary and drug regimens, pre-existing genetic disorders of lipid metabolism, and renal replacement therapies (including haemodialysis, peritoneal dialysis, and renal transplantation) determine the natural history of lipid disorders in patients with kidney disease. Despite the adverse effects associated with dysregulated reverse cholesterol transport and advances in our understanding of the underlying mechanisms, safe and effective therapeutic interventions are currently lacking. This Review provides an overview of HDL metabolism under normal conditions, and discusses the features, mechanisms, and consequences of HDL abnormalities in patients with nephrotic syndrome or advanced CKD.

The Effect of n-3 Fatty Acids on Small Dense Low-Density Lipoproteins in Patients With End-Stage Renal Disease: A Randomized Placebo-Controlled Intervention Study

OBJECTIVE

Patients with end-stage renal disease (ESRD) have a high risk of cardiovascular disease. Small dense low-density lipoprotein (sdLDL) particles are particularly atherogenic. Marine n-3 polyunsaturated fatty acids (PUFA) may have a beneficial effect on numbers of sdLDL particles, and the aim of this study was to investigate the effect of n-3 PUFA on plasma levels of sdLDL in patients with ESRD.

METHODS

ESRD patients with cardiovascular disease (n = 161) on chronic hemodialysis were randomized to treatment with 1.7 g of n-3 PUFA (n = 81) or 2 g of placebo (olive oil; n = 80) for 3 months. The study was double-blinded. Densities of LDL and percentages of sdLDL (sdLDL%) of total LDL were measured before and after intervention. On the basis of sdLDL%, patients were classified as having lipid pattern A, I (intermediate), or B defined by a successive increase in sdLDL concentration and decrease in lipid particle size.

RESULTS

n-3 PUFAs significantly reduced triglycerides. However, LDL cholesterol remained unchanged. In the n-3 group, the LDL density did not change significantly during follow-up. Similarly, the LDL density remained unchanged in the placebo group. In the n-3 group, the sdLDL% was 34% at baseline and unchanged at follow-up. At baseline 71% had LDL pattern A, 9% had pattern I, and 20% had pattern B, and none of these patterns were significantly changed by n-3 PUFA supplementation.

CONCLUSION

Dietary supplementation with 1.7 g of n-3 PUFA had no effect on LDL density or sdLDL levels in patients with ESRD.

Lipid abnormalities in kidney disease and management strategies

Patients with kidney diseases continue to experience significant cardiovascular disease (CVD) morbidity and mortality. Although there are many important risk factors playing a role in the pathogenesis of CVD in chronic kidney disease (CKD) patients, dyslipidemia (elevated triglycerides, elevated oxidized low-density lipoprotein and low/dysfunctional low high-density) represents one of the modifiable risk factors. Renal failure patients have unique lipid abnormalities which not only have complex role in pathogenesis of CVD but also cause relative resistance to usual interventions. Most of the randomized trials have been in hemodialysis population and data from CKD non-dialysis, peritoneal dialysis and renal transplant populations is extremely limited. Compared to general population, evidence of mortality benefit of lipid lowering medications in CKD population is scarce. Future research should be directed towards establishing long term benefits and side effects of lipid lowering medications, through randomized trials, in CKD population.

The serum lipids levels may be underestimated in patients on hemodialysis

OBJECTIVE

Although lipid disorders are a well-known risk factor for cardiovascular disease (CVD) in the general population, the optimal management with lipid-lowering therapy to reduce CVD risks and mortality in hemodialysis (HD) patients remains controversial. In the clinical setting, dyslipidemia can be diagnosed based on the detection of elevated lipid concentrations at the beginning of HD. This study investigated changes in the levels of serum lipids during a single HD session.

METHODS

The serum total cholesterol, triglyceride and high-density lipoprotein (HDL) cholesterol levels were measured in 31 HD patients at zero, two and four hours after the beginning of a single HD session. The data were analyzed using the Wilcoxon signed-rank test, a linear mixed model and Spearman's rank correlation analysis.

RESULTS

The serum total cholesterol, HDL cholesterol and non-HDL cholesterol levels increased significantly during the HD session. Even after the lipid parameters were corrected for changes in the total protein level, the total cholesterol and HDL cholesterol levels increased, whereas the non-HDL cholesterol levels did not change significantly. The percentage change in the serum levels of these lipid fractions correlated strongly with the percentage change in the ultrafiltration volume per body weight. In contrast, the serum triglyceride levels were decreased significantly at two hours compared with the levels noted at the beginning of HD and gradually increased at four hours.

CONCLUSION

The serum lipid levels are influenced significantly by HD treatment and ultrafiltration. Evaluating the degree of dyslipidemia at the beginning of a HD session may therefore underestimate the levels of serum lipids in HD patients with a large amount of weight gain, thus resulting in the use of insufficient lipid-lowering therapy.

Post-transcriptional nature of uremia-induced downregulation of hepatic apolipoprotein A-I production

Chronic kidney disease is associated with premature death from cardiovascular disease, which is, in part, driven by high density lipoprotein deficiency and dysfunction. One of the main causes of high density lipoprotein deficiency in chronic kidney disease is diminished plasma apolipoprotein (Apo)A-I level. Plasma ApoA-I is reduced in dialysis patients and hepatic ApoA-I messenger RNA (mRNA) is decreased in the uremic rats. This study explored the mechanism of uremia-induced downregulation of ApoA-I. Human hepatoma derived cells were incubated in media containing whole plasma or plasma subfractionation from normal subjects and patients with end stage renal disease pre- and posthemodialysis. Cells and culture media were isolated to measure ApoA-I protein and mRNA. ApoA-I promoter activity was measured using transfection with a luciferase promoter construct containing the -2096 to +293 segment of ApoA-I gene. Finally, effect of uremic and control plasma was assessed on ApoA-I RNA stability. Exposure to uremic plasma significantly reduced ApoA-I mRNA expression and ApoA-I protein production. These effects were reversed by replacing uremic plasma with normal plasma. Although no difference in ApoA-I promoter activity was found between cells exposed to uremic and normal plasma, uremic plasma significantly reduced ApoA-I RNA stability. Experiments using plasma subfractions revealed that the inhibitory effect of uremic plasma on ApoA-I mRNA expression resides in fractions containing molecules larger but not smaller than 30 kd. The pre- and postdialysis plasma exerted an equally potent inhibitory effect on ApoA-I mRNA abundance. Uremia lowers ApoA-I production by reducing its RNA stability. The inhibitory effect of uremic milieu on ApoA-I mRNA expression is mediated by non-dialyzable molecule(s) larger than 30 kd.

Vascular Access versus the Effect of Statins on Inflammation and Fibrinolysis in Renal Dialysis Patients

Purpose

The aim of this work was to assess the effect of statin therapy on inflammatory and fibrinolytic/endothelial (dys)function markers in end-stage renal disease (ESRD) patients under hemodialysis (HD), according to the type of vascular access.

Methods

This transversal study includes 191 ESRD patients under regular HD, divided into four groups according to vascular access and statin therapy: 87 patients with arteriovenous fistula (AVF) and no statins (AVF-NS), 61 with AVF and statins (AVF-S), 27 with central venous dialysis catheter (CVC) and no statins (CVC-NS) and 16 with CVC and statins (CVC-S). The basic lipid profile and fibrinolytic/endothelial cell function markers were assessed.

Results

Patients with CVC presented significantly higher levels of D-dimers compared with AVF groups. CVC-NS patients also presented the highest IL-6 values, which were significantly higher than those presented by CVC-S patients. AVF-S patients presented significantly higher t-PA and PAI-1 values and lower adiponectin levels compared with AVF-NS.

Conclusions

Our results demonstrate that patients with CVC, particularly those not under statin therapy, present a higher production and turnover of fibrin. We also found that statin therapy decreases inflammation in CVC patients but is associated with a reduction of adiponectin and increased endothelial function marker levels in AVF patients.

High-density lipoprotein in uremic patients: metabolism, impairment, and therapy

Several studies have shown that HDL has altered antioxidant and anti-inflammatory effects in chronic uremia, either by the reduction in its antioxidant enzymes or by the impairment of their activity. Systemic oxidative stress, which is highly prevalent in chronic kidney disease (CKD) patients, has been shown to decrease antioxidant and anti-inflammatory effects of HDL and even transform it into a pro-oxidant and pro-inflammatory agent. For this reason, we believe that the propensity for accelerated cardiovascular disease in CKD is facilitated by a few key features of this disease, namely, oxidative stress, inflammation, hypertension, and disorders of lipid metabolism. In a nutshell, oxidative stress and inflammation enhance atherosclerosis leading to increased cardiovascular mortality and morbidity in this population. In this detailed review, we highlight the current knowledge on HDL dysfunction and impairment in chronic kidney disease as well as the available therapy.

Reasons for the lack of salutary effects of cholesterol-lowering interventions in end-stage renal disease populations

Cardiovascular disease (CVD) is the main cause of premature death in patients with chronic kidney disease (CKD). The underlying mechanisms of CVD in patients with mild to moderate CKD are different from those with end-stage renal disease (ESRD). While serum cholesterol is frequently elevated and contributes to atherosclerosis in many CKD patients, particularly those with nephrotic proteinuria, it is usually normal, even subnormal, in most ESRD patients receiving hemodialysis. CVD in the ESRD population is primarily driven by oxidative stress, inflammation, accumulation of the oxidation-prone intermediate-density lipoproteins, chylomicron remnants and small dense low-density lipoprotein particles as well as high-density lipoprotein deficiency and dysfunction, hypertension, vascular calcification, and arrhythmias. Only a minority of hemodialysis patients have hypercholesterolemia which is most likely due to genetic or unrelated factors. In addition, due to peritoneal losses of proteins which simulate nephrotic syndrome, peritoneal dialysis patients often exhibit hypercholesterolemia. Clearly when present, hypercholesterolemia contributes to CVD in the CKD and ESRD population and justifies cholesterol-lowering therapy. However, the majority of ESRD patients and a subpopulation of CKD patients with minimal proteinuria have normal or subnormal serum cholesterol levels and do not benefit from and can be potentially harmed by statin therapy. In fact the lack of efficacy of statins in hemodialysis patients has been demonstrated in several randomized clinical trials. This review is intended to provide an overview of the mechanisms responsible for the failure of statins to reduce cardiovascular morbidity and mortality in most ESRD patients and to advocate the adoption of individualized care principles in the management of dyslipidemia in this population.

Treatment of chronic hemodialysis patients with low-dose fenofibrate effectively reduces plasma lipids and affects plasma redox status

Dyslipidemia is common in chronic hemodialysis patients and its underlying mechanism is complex. Hemodialysis causes an imbalance between antioxidants and production of reactive oxygen species, which induces the oxidative stress and thereby may lead to accelerated atherosclerosis. Statins have been found to be little effective in end-stage kidney disease and other lipid-lowering therapies have been only scarcely studied. The study aimed to assess the effect of low-dose fenofibrate therapy on plasma lipids and redox status in long-term hemodialysis patients with mild hypertriglyceridemia.

Twenty seven chronic hemodialysis patients without any lipid-lowering therapy were included in a double-blind crossover, placebo-controlled study. The patients were randomized into two groups and were given a sequence of either 100 mg of fenofibrate per each hemodialysis day for 4 weeks or placebo with a week-long wash-out period between treatment periods. Plasma lipids, high sensitive C-reactive protein (CRP), urea, creatinine, electrolytes, phosphocreatine kinase (CK), GOT, GPT and plasma thiols (total and free glutathione, homocysteine, cysteine and cysteinylglycine) were measured at baseline and after each of the study periods. Plasma aminothiols were measured by reversed phase HPLC with thiol derivatization with 2-chloro-1-methylquinolinium tetrafluoroborate.

Fenofibrate therapy caused a significant decrease of total serum cholesterol, LDL cholesterol and triglycerides and an increase of HDL cholesterol. The treatment was well tolerated with no side-effects but there was a small but significant increase of CK not exceeding the upper limit of normal range. There were no changes of serum CRP, potassium, urea, and creatinine and liver enzymes during the treatment. Neither total nor total free cysteinylglycine and cysteine changed during the study but both total and free glutathione increased during the therapy with fenofibrate and the same was observed in case of plasma homocysteine.

The study shows that a treatment with reduced fenofibrate dose is safe and effective in reducing serum triglycerides and cholesterol in chronic dialysis patients and may shift plasma aminothiol balance towards a more antioxidative pattern.