Lipoprotein Metabolism and Lipid Management in Chronic Kidney Disease

Lipoprotein metabolism and CKD: overview

Patients with chronic kidney disease (CKD) frequently display abnormalities of plasma lipids and lipoproteins. These abnormalities include hypertriglyceridemia associated with elevated levels of very low-density lipoproteins (VLDLs) and chylomicrons. There is often also an increase in the concentration of the atherogenic, cholesterol-enriched remnants of VLDLs and chylomicrons. The concentration of low-density lipoprotein cholesterol is usually normal, but there is frequently a decrease in concentration of the cardio-protective high-density lipoproteins. There is also often an increase in the concentration of the atherogenic lipoprotein (a) particles. This article provides an overview of plasma lipoprotein transport and identifies mechanisms responsible for the abnormalities observed in patients with CKD.

Changes in serum inflammatory markers are associated with changes in apolipoprotein A1 but not B after the initiation of dialysis

BACKGROUND

Few studies have examined the changes in lipoproteins over time and how inflammation is associated with lipoprotein concentrations among patients with end-stage renal disease on dialysis. One possible explanation for the association of low LDL cholesterol concentration and adverse outcomes is that inflammation reduces selected apolipoprotein concentrations.

METHODS

Serum samples were collected from a subsample of patients enrolled into the Comprehensive Dialysis Study every 3 months for up to 1 year. We examined the relation between temporal patterns in levels of inflammatory markers and changes in apolipoproteins (apo) A1 and B and the apo B/A1 ratio using linear mixed effects modeling and adjusting for potential confounders.

RESULTS

We enrolled 266 participants from 56 dialysis facilities. The mean age was 62 years, 45% were women and 26% were black. Apo A1 was lower among patients with higher Quetelet's (body mass) index (BMI), diabetes mellitus and atherosclerosis. Apo B was lower among older patients, patients with higher serum creatinine and patients with lower BMI. Over the course of a year, apo A1 changed inversely with serum concentrations of the acute phase proteins C-reactive protein (CRP) and α1 acid glycoprotein (α1AG), while apo B did not. Changes in α1AG were more strongly associated with changes in apolipoprotein concentrations than were changes in CRP; increases in α1AG were associated with decreases in apo A1 and increases in the apo B/A1 ratio.

CONCLUSIONS

Changes in inflammatory markers were associated with changes in apo A1, but not apo B over 1 year, suggesting that reductions in high-density lipoprotein cholesterol are associated with inflammation, either of which could mediate cardiovascular risk, but not supporting a hypothesis linking increased risk of low levels of apo B containing lipoproteins to the risk associated with inflammation.

Dyslipidemia in patients with chronic and end-stage kidney disease

In this review, we discuss the physiology, diagnosis and treatment of dyslipidemia in patients with chronic and end-stage renal disease. The recent important clinical trials in patients with chronic kidney disease and dyslipidemia are reviewed. Because of the lack of evidence in treating lipid abnormalities in this specific patient population, we propose that future studies should focus on the pathophysiological mechanisms and treatment of dyslipidemia in this special patient population.

Chronic renal failure complications and management in kidney transplanted and nontransplanted patients

BACKGROUND

Our purpose was to compare the management of chronic kidney disease (CKD) according to Kidney Disease Quality Initiative (K/DOQI) recommendations in kidney transplanted patients (T) and nontransplanted ones (NT).

METHODS

Data concerning CKD complications were collected retrospectively. Patients seen in consultations in our department from May 2009 to June 2010 were selected if they had at least 6 months of follow-up, CKD stage 4 or 5, and no exclusion criteria namely hospitalization, active cancer, or infection in the 3 months before data collection.

RESULTS

Fifty-eight T were compared with 85 NT matched by CKD stage (4-5). Anemia within K/DOQI target was better controlled among NT (51.2% versus 41.3%); however, ferritin levels within K/DOQI target were higher (80% T versus 51.7% NT). Average arterial blood pressure was similar in both groups but 51.7% of T were in K/DOQI target versus 41% of NT. Dyslipidemia within cholesterol K/DOQI target was better controlled in 60% (NT) versus 35% NT with 63.5% versus 38% NT within low-density lipoprotein K/DOQI targets. Phosphorus level was better controlled among T; parathyroid was better controlled in among 65% NT versus 50% T within the target level.

CONCLUSION

Most complications of CKD were better managed among NT.

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.

Activation of renin-angiotensin system is involved in dyslipidemia-mediated renal injuries in apolipoprotein E knockout mice and HK-2 cells

Background

Dyslipidemia and activation of renin-angiotensin system (RAS) contribute to the progression of chronic kidney disease (CKD). This study investigated possible synergistic effects of intrarenal RAS activation with hyperlipidemia in renal injuries.

Methods

Apolipoprotein knockout mice were fed with normal chow diet (control) or high fat diet (HF group) for eight weeks. Human proximal tubular epithelial cell line (HK-2) was treated without (control) or with cholesterol (30 μg/ml) plus 25-hydroxycholesterol (1 μg/ml) (lipid group) for 24 hours. The plasma lipid profile and RAS components were determined by clinical biochemistry assay and radiommunoassay, respectively. Collagen deposition in kidneys was evaluated by Masson-staining. The gene and protein expressions of molecules involved in RAS components and biomarkers of epithelial mesenchymal transition (EMT) were examined by real-time PCR, immunochemical staining, and Western blot.

Results

The mice fed with high-fat diet showed significant hyperlipidemia with collagen deposition in renal tubular interstitium compared to controls. The plasma levels of renin, angiotensin I, and angiotensin II were no difference in two groups. However, the kidneys of HF group showed up-regulated RAS components, which were positively associated with increased plasma levels of triglyceride, total cholesterol, and LDL. These effects were further confirmed by in vitro studies. Lipid loading induced HK-2 cells underwent EMT, which was closely associated with the increased expressions of intracellular RAS components.

Conclusions

Local RAS activation was involved in hyperlipidemia-mediated renal injuries, suggesting that there are synergistic effects resulting from RAS activation with hyperlipidemia that accelerates the progression of CKD.

A prospective controlled study of kidney donors: baseline and 6-month follow-up

BACKGROUND

Most previous studies of living kidney donors have been retrospective and have lacked suitable healthy controls. Needed are prospective controlled studies to better understand the effects of a mild reduction in kidney function from kidney donation in otherwise healthy individuals.

STUDY DESIGN

Prospective, controlled, observational cohort study.

SETTING & PARTICIPANTS

Consecutive patients approved for donation at 8 transplant centers in the United States were asked to participate. For every donor enrolled, an equally healthy control with 2 kidneys who theoretically would have been suitable to donate a kidney also was enrolled.

PREDICTOR

Kidney donation.

MEASUREMENTS

At baseline predonation and at 6 months after donation, medical history, vital signs, measured (iohexol) glomerular filtration rate, and other measurements were collected. There were 201 donors and 198 controls who completed both baseline and 6-month visits and form the basis of this report.

RESULTS

Compared with controls, donors had 28% lower glomerular filtration rates at 6 months (94.6 ± 15.1 [SD] vs 67.6 ± 10.1 mL/min/1.73 m(2); P < 0.001), associated with 23% greater parathyroid hormone (42.8 ± 15.6 vs 52.7 ± 20.9 pg/mL; P < 0.001), 5.4% lower serum phosphate (3.5 ± 0.5 vs 3.3 ± 0.5 mg/dL; P < 0.001), 3.7% lower hemoglobin (13.6 ± 1.4 vs 13.1 ± 1.2 g/dL; P < 0.001), 8.2% greater uric acid (4.9 ± 1.2 vs 5.3 ± 1.1 mg/dL; P < 0.001), 24% greater homocysteine (1.2 ± 0.3 vs 1.5 ± 0.4 mg/L; P < 0.001), and 1.5% lower high-density lipoprotein cholesterol (54.9 ± 16.4 vs 54.1 ± 13.9 mg/dL; P = 0.03) levels. There were no differences in albumin-creatinine ratios (5.0 [IQR, 4.0-6.6] vs 5.0 [IQR, 3.3-5.4] mg/g; P = 0.5), office blood pressures, or glucose homeostasis.

LIMITATIONS

Short duration of follow-up and possible bias resulting from an inability to screen controls with kidney and vascular imaging performed in donors.

CONCLUSIONS

Kidney donors have some, but not all, abnormalities typically associated with mild chronic kidney disease 6 months after donation. Additional follow-up is warranted.

Low body mass index and dyslipidemia in dialysis patients linked to elevated plasma fibroblast growth factor 23

BACKGROUND

Fibroblast growth factor 23 (FGF23) has been associated with death in dialysis patients. Since FGF23 shares structural features with FGF19 subfamily members that exert hormonal control of fat mass, we hypothesized that high circulating FGF23 concentrations would be associated with the development of a uremic lipid profile and lower body mass index (BMI).

METHODS

This study was conducted among 654 patients receiving chronic hemodialysis. C-terminal FGF23 concentrations were measured in stored plasma samples. Linear regression was used to examine the cross-sectional associations of plasma FGF23 concentrations with BMI, total cholesterol (TC), low-density lipoprotein-cholesterol (LDL-C), high-density lipoprotein-cholesterol (HDL-C) and triglycerides. Cox proportional hazard models were used to examine the association between FGF23 concentrations and all-cause mortality.

RESULTS

Participants had a mean age of 60 ± 11 years and a median (IQR) FGF23 concentration of 4,212 (1,411-13,816) RU/ml. An increase per SD in log10 FGF23 was associated with lower BMI (β = -1.11; p = 0.008), TC (β = -6.46; p = 0.02), LDL-C (β = -4.73; p = 0.04) and HDL-C (β = -2.14; p = 0.03); after adjusting for age, gender, race, cardiovascular risk factors, serum albumin, markers of mineral metabolism, and use of lipid-lowering drugs. The association of FGF23 with death was attenuated after adjustment for HDL-C (HR of highest quartile 1.53, 95% CI 1.06-2.20 compared to lowest quartile).

CONCLUSION

These results indicate that higher plasma FGF23 levels are associated with lower BMI and dyslipidemia in dialysis patients. The association between FGF23 and death may be mediated through unexplored metabolic risk factors unrelated to mineral metabolism.

Is lipid management effective for all stages of CKD?

Patients with chronic kidney disease (CKD) suffer from high rates of cardiovascular morbidity and mortality. The general approach to traditional cardiovascular risk factor modification via dyslipidemia control has not been thoroughly tested in patients with all stages of CKD. In this article, we review the evidence for statin therapy in patients at various stages of CKD, including patients with CKD on dialysis and patients with kidney transplants.

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.

Sevelamer for hyperphosphataemia in kidney failure: controversy and perspective

The term 'chronic kidney disease-mineral and bone disorder' (CKD-MBD), coined in 2006, was introduced in a position statement by the Kidney Disease: Improving Global Outcomes (KDIGO) organization. According to the KDIGO guidelines, CKD-MBD is a systemic disorder and patients with vascular or valvular calcifications should be included in the group with the greatest cardiovascular risk. Therefore, the presence or absence of calcification is a key factor in strategy decisions for such patients. In particular, it is recommended that the use of calcium-based phosphate binders should be restricted in patients with hypercalcaemia, vascular calcification, low levels of parathyroid hormone (PTH) or adynamic bone disease. In this respect, it should be underscored that treatment with phosphate-binding agents can normalise the levels of phosphate and PTH, but the use of calcium carbonate can favour the progression of vascular calcifications. There is evidence of reduced progression of vascular calcification in patients treated with sevelamer compared with high doses of calcium-based binders, but there is as yet no strong evidence regarding hard outcomes, such as mortality or hospitalization, to support the use of one treatment over another. Nevertheless, a number of experimental and observational findings seem to suggest that sevelamer should be preferred over calcium-based binders, in as much as these can increase cardiovascular mortality when used in high doses. A threshold dose below which calcium-based binders can be used safely in CKD patients with hyperphosphatemia has yet to be established.

Dysregulation of hepatic fatty acid metabolism in chronic kidney disease

BACKGROUND

Chronic kidney disease (CKD) results in hypertriglyceridemia which is largely due to impaired clearance of triglyceride-rich lipoproteins occasioned by downregulation of lipoprotein lipase and very low-density lipoprotein (LDL) receptor in the skeletal muscle and adipose tissue and of hepatic lipase and LDL receptor-related protein in the liver. However, data on the effect of CKD on fatty acid metabolism in the liver is limited and was investigated here.

METHODS

Male Sprague-Dawley rats were randomized to undergo 5/6 nephrectomy (CRF) or sham operation (control) and observed for 12 weeks. The animals were then euthanized and their liver tissue tested for nuclear translocation (activation) of carbohydrate-responsive element binding protein (ChREBP) and sterol-responsive element binding protein-1 (SREBP-1) which independently regulate the expression of key enzyme in fatty acid synthesis, i.e. fatty acid synthase (FAS) and acyl-CoA carboxylase (ACC) as well as nuclear Peroxisome proliferator-activated receptor alpha (PPARα) which regulates the expression of enzymes involved in fatty acid oxidation and transport, i.e. L-FABP and CPT1A. In addition, the expression of ATP synthase α, ATP synthase β, glycogen synthase and diglyceride acyltransferase 1 (DGAT1) and DGAT2 were determined.

RESULTS

Compared with controls, the CKD rats exhibited hypertriglyceridemia, elevated plasma and liver tissue free fatty acids, increased nuclear ChREBP and reduced nuclear SREBP-1 and PPARα, upregulation of ACC and FAS and downregulation of L-FABP, CPT1A, ATP synthase α, glycogen synthase and DGAT in the liver tissue.

CONCLUSION

Liver in animals with advanced CKD exhibits ChREBP-mediated upregulation of enzymes involved in fatty acid synthesis, downregulation of PPARα-regulated fatty acid oxidation system and reduction of DGAT resulting in reduced fatty acid incorporation in triglyceride.

[Predilution online hemodiafiltration: which dose of anticoagulation?]

INTRODUCTION

Patients in end stage renal disease on hemodialysis are in higher risk of bleeding related to the anticoagulation used during a session, so only the lowest effective dose of anticoagulation must be used. The aim of this study was to evaluate the efficacy of predilution in hemodiafiltration with reduced dose of anticoagulation compared to hemodialysis in preventing coagulation of circuits.

PATIENTS AND METHODS

This study was conducted in stable hemodialysis patients without high bleeding risk. All patients were treated by two different treatments: (A) conventional hemodialysis, (B) predilution hemodiafiltration with the half dose of anticoagulation used during treatment (A). Other confounding parameters were kept constant during the study. The primary endpoint was the incidence of major thrombotic events judged on a subjective visual score.

RESULTS

Twenty-one patients were included (105 sessions for each treatment). Major incidents are occurring more frequently in predilution hemodiafiltration with reduced dose of anticoagulation (P=0.03). The premature discontinuation of sessions was more frequent in predilution hemodiafiltration, this difference was not significant (P=0.07). Duration of sessions was significantly shorter in predilution hemodiafiltration (P=0.03). The higher frequency of thrombotic events in predilution hemodiafiltration has no effect on net ultrafiltration volume achieved in both treatments.

CONCLUSION

Predilution hemodiafiltration with a lower dose of anticoagulation did not prevent major clotting of extracorporeal circuit manner at least equivalent to a reference method.

Statins and kidney disease: is the study of heart and renal protection at the cutting edge of evidence?

PURPOSE OF REVIEW

Dyslipidaemias are noted in all stages of chronic kidney disease (CKD). Currently most evidence for their treatment comes from secondary retrospective analyses of patient subgroups with CKD recruited into clinical trials powered of hypertensive and dyslipideamic cohorts powered for cardiovascular endpoints.These analyses suggest a number of different beneficial effects of statins (3-hydroxy-3-methylglutaryl coenzyme A reductase inhibitors) on renal, cardiovascular and mortality outcomes. However, there is disagreement on the impact of interventions at different CKD stages, and on treatment targets.

RECENT FINDINGS

The Study of Heart and Renal Protection (SHARP) trial published in June 2011 was the first trial specifically powered to investigate atherosclerotic outcomes in CKD patients. It found a 17% overall reduction in major adverse cardiac events in the statin-treated group compared with placebo, yet no effect on any renal outcomes of proteinuria and progressive decline of glomerular filtration rate. Furthermore, the Swedish Web-system for Enhancement and Development of Evidencebased care in Heart disease Evaluated According to Recommended Therapies (SWEDEHEART) investigators provided further important observational data on the beneficial effect of statins in CKD stages I-IV.

SUMMARY

The evidence that statins have a cardiovascular and mortality benefit in CKD stages I-IV has been reinforced by SHARP, which also definitively shows that there are no special safety concerns for their administration in CKD. However, the utility of the use of statins in patients on dialysis is far from clear, at least in our opinion. The effect of statins on renal outcomes is unconvincing and the evidence does not presently support their use for these indications alone.

Risk factors of cardiovascular disease among children with chronic kidney disease in Gaza strip

Background:

Chronic kidney disease (CKD) is increasingly recognized as a global public health problem. Cardiovascular disease (CVD) is a major cause of mortality in patients with mild-to-moderate CKD and end-stage renal disease. There is accumulating evidence that the increase in CVD burden is present in CKD patients prior to dialysis, due both to conventional risk factors and kidney-specific disease. Detection and initiation of treatment for CVD risk factors at early stages of CKD should be effective in reducing CVD events before as well as after the onset of kidney failure.

Materials and Methods:

The study sample consisted of a total of 112 subjects aged ≤12 years: 60 CKD patients and 52 healthy control individuals. All subjects were investigated for a group of CVD risk factors such as: Hypertension, diabetes, dyslipidemia, physical inactivity, body mass index (BMI), family history of CVD, hypoalbuminemia, albuminuria, anemia, Ca x P product, and inflammation in terms of C-reactive protein (CRP).

Results:

Patients (40 males and 20 females) were categorized into four CKD stages (2, 3, 4, and 5) where, Stage 4 had the highest frequency, followed by Stages 3, 5 and 2. Evaluation of the patients indicated that they were shorter, had lower weight and had higher systolic and diastolic blood pressure as compared with control subjects. Frequency of physical inactivity among patients was two-fold higher than controls (50% vs. 25%). The patients showed significantly higher levels of cholesterol (163.6±39.8 vs. 141.8±24.2 mg/dL, P<0.0001), triglycerides (145.5±67.1 vs. 82.9±39.8 mg/dL, P<0.0001), low-density lipoprotein (92.6±31.9 vs. 72.5±19 mg/dL, P<</i>0.0001) and albumin/creatinine ratio (1792±3183 vs. 11.1±6.6 mg/g, P<0.0001). Moreover, the patients had lower levels of high-density lipoprotein (41.9±11.0 vs. 52.7±11.7 mg/dL, P<0.0001), hemoglobin (9.8±1.4 vs. 11.9±0.8 g/dL, P<0.0001) and albumin (4.6±0.6 vs. 4.8±0.2 g/dL, P=0.012). The CRP showed higher occurrence among patients (40% were positive for CRP). Calcium and phosphorus evaluation showed significantly lower calcium and higher phosphorus among patients. However, the difference in Ca X P product was not statistically significant.

Conclusions:

The study indicates that many of the CVD risk factors are associated with the different stages of CKD in children patients prior to dialysis, and that some of these factors are exacerbated as CKD progresses.