HDL in CKD-The Devil Is in the Detail

Analyzing Longitudinal Health Screening Data with Feature Ensemble and Machine Learning Techniques: Investigating Diagnostic Risk Factors of Metabolic Syndrome for Chronic Kidney Disease Stages 3a to 3b

Longitudinal data, while often limited, contain valuable insights into features impacting clinical outcomes. To predict the progression of chronic kidney disease (CKD) in patients with metabolic syndrome, particularly those transitioning from stage 3a to 3b, where data are scarce, utilizing feature ensemble techniques can be advantageous. It can effectively identify crucial risk factors, influencing CKD progression, thereby enhancing model performance. Machine learning (ML) methods have gained popularity due to their ability to perform feature selection and handle complex feature interactions more effectively than traditional approaches. However, different ML methods yield varying feature importance information. This study proposes a multiphase hybrid risk factor evaluation scheme to consider the diverse feature information generated by ML methods. The scheme incorporates variable ensemble rules (VERs) to combine feature importance information, thereby aiding in the identification of important features influencing CKD progression and supporting clinical decision making. In the proposed scheme, we employ six ML models-Lasso, RF, MARS, LightGBM, XGBoost, and CatBoost-each renowned for its distinct feature selection mechanisms and widespread usage in clinical studies. By implementing our proposed scheme, thirteen features affecting CKD progression are identified, and a promising AUC score of 0.883 can be achieved when constructing a model with them.

Association between sarcopenia and new-onset chronic kidney disease among middle-aged and elder adults: findings from the China Health and Retirement Longitudinal Study

BACKGROUND

Sarcopenia is a senile syndrome of age-related muscle loss. It is thought to affect the development of chronic kidney disease and has a serious impact on the quality of life of the elder adults. Little is known about the association between sarcopenia and new-onset chronic kidney disease in middle-aged and elder adults. Using nationally representative data from the China Health and Retirement Longitudinal Study (CHARLS), we conducted a longitudinal analysis to investigate the association between sarcopenia status and new-onset chronic kidney disease in middle-aged and elder adults in China.

METHODS

The study population consisted of 3676 participants aged 45 or older selected from 2011 CHARLS database who had no history of chronic kidney disease at the baseline and completed the follow-up in 2015. A multivariate cox regression model was employed to examine the association between sarcopenia and the incidence of new-onset chronic kidney disease.

RESULTS

Followed up for 4 years, a total of 873 (22.5%) new cases of chronic kidney disease occurred. Among them, participants diagnosed with sarcopenia (HR1.45; 95% CI 1.15-1.83) were more likely to develop new-onset chronic kidney disease than those without sarcopenia. Similarly, patients with sarcopenia were more likely to develop new-onset chronic kidney disease than those with possible sarcopenia (HR 1.27; 95%CI 1.00-1.60). Subgroup analysis revealed that elder adults aged between 60 and 75 years old (HR 1.666; 95%CI 1.20-22.28), with hypertension (HR 1.57; 95%CI 1.02-2.40), people with sarcopenia had a significantly higher risk of developing new-onset chronic kidney disease than those without sarcopenia (all P < 0.05).

CONCLUSION

Middle-aged and elder adults diagnosed with sarcopenia have a higher risk of developing new-onset chronic kidney disease.

High-density lipoprotein protects vascular endothelial cells from indoxyl sulfate insults through its antioxidant ability

Chronic kidney disease (CKD) patients have a high risk of cardiovascular disease. Indoxyl sulfate (IS) is a uremic toxin that has been shown to inhibit nitric oxide production and cause cell senescence by inducing oxidative stress. High-density lipoprotein (HDL) has a protective effect on the cardiovascular system; however, its impacts on IS-damaged endothelial cells are still unknown. This study aimed to explore the effects of exogenous supplement of HDL on vascular endothelial cells in a uremia-mimic environment. Tube formation, migration, adhesion, and senescence assays were used to evaluate the cell function of human aortic endothelial cells (HAECs). Reactive oxygen species generation was measured by using Amplex red assay. L-NAME and MCI186 were used as a nitric oxide synthase inhibitor and a free radical scavenger, respectively. HDL exerted anti-inflammatory and antioxidant effects via HIF-1α/HO-1 activation and IL-1β/TNF-α/IL-6 inhibition in IS-stimulated HAECs. HDL improved angiogenesis ability through upregulating Akt/eNOS/VEGF/SDF-1 in IS-stimulated HAECs. HDL decreased endothelial adhesiveness via downregulating VCAM-1 and ICAM-1 in IS-stimulated HAECs. Furthermore, HDL reduced cellular senescence via upregulating SIRT1 and downregulating p53 in IS-stimulated HAECs. Importantly, the above beneficial effects of HDL were mainly due to its antioxidant ability. In conclusion, HDL exerted a comprehensive protective effect on vascular endothelial cells against damage from IS through its antioxidant ability. The results of this study might provide a theoretical basis for potential HDL supplementation in CKD patients with endothelial damage.

Dyslipidemia in Patients with Chronic Kidney Disease: An Updated Overview

Dyslipidemia is a potentially modifiable cardiovascular risk factor. Whereas the recommendations for the treatment target of dyslipidemia in the general population are being more and more rigorous, the 2013 Kidney Disease: Improving Global Outcomes clinical practice guideline for lipid management in chronic kidney disease (CKD) presented a relatively conservative approach with respect to the indication of lipid lowering therapy and therapeutic monitoring among the patients with CKD. This may be largely attributed to the lack of high-quality evidence derived from CKD population, among whom the overall feature of dyslipidemia is considerably distinctive to that of general population. In this review article, we cover the characteristic features of dyslipidemia and impact of dyslipidemia on cardiovascular outcomes in patients with CKD. We also review the current evidence on lipid lowering therapy to modify the risk of cardiovascular events in this population. We finally discuss the association between dyslipidemia and CKD progression and the potential strategy to delay the progression of CKD in relation to lipid lowering therapy.

CKD Progression Prediction in a Diverse US Population: A Machine-Learning Model

Rationale & Objective

Chronic kidney disease (CKD) is a major cause of morbidity and mortality. To date, there are no widely used machine-learning models that can predict progressive CKD across the entire disease spectrum, including the earliest stages. The objective of this study was to use readily available demographic and laboratory data from Sonic Healthcare USA laboratories to train and test the performance of machine learning-based predictive risk models for CKD progression.

Study Design

Retrospective observational study.

Setting & Participants

The study population was composed of deidentified laboratory information services data procured from a large US outpatient laboratory network. The retrospective data set included 110,264 adult patients over a 5-year period with initial estimated glomerular filtration rate (eGFR) values between 15-89 mL/min/1.73 m2.

Predictors

Patient demographic and laboratory characteristics.

Outcomes

Accelerated (ie, >30%) eGFR decline associated with CKD progression within 5 years.

Analytical Approach

Machine-learning models were developed using random forest survival methods, with laboratory-based risk factors analyzed as potential predictors of significant eGFR decline.

Results

The 7-variable risk classifier model accurately predicted an eGFR decline of >30% within 5 years and achieved an area under the curve receiver-operator characteristic of 0.85. The most important predictor of progressive decline in kidney function was the eGFR slope. Other key contributors to the model included initial eGFR, urine albumin-creatinine ratio, serum albumin (initial and slope), age, and sex.

Limitations

The cohort study did not evaluate the role of clinical variables (eg, blood pressure) on the performance of the model.

Conclusions

Our progressive CKD classifier accurately predicts significant eGFR decline in patients with early, mid, and advanced disease using readily obtainable laboratory data. Although prospective studies are warranted, our results support the clinical utility of the model to improve timely recognition and optimal management for patients at risk for CKD progression.

Plain-Language Summary

Defined by a significant decrease in estimated glomerular filtration rate (eGFR), chronic kidney disease (CKD) progression is strongly associated with kidney failure. However, to date, there are no broadly used resources that can predict this clinically significant event. Using machine-learning techniques on a diverse US population, this cohort study aimed to address this deficiency and found that a 5-year risk prediction model for CKD progression was accurate. The most important predictor of progressive decline in kidney function was the eGFR slope, followed by the urine albumin-creatinine ratio and serum albumin slope. Although further study is warranted, the results showed that a machine-learning model using readily obtainable laboratory information accurately predicts CKD progression, which may inform clinical diagnosis and management for this at-risk population.

Design and fabrication of intracellular therapeutic cargo delivery systems based on nanomaterials: current status and future perspectives

Intracellular cargo delivery, the introduction of small molecules, proteins, and nucleic acids into a specific targeted site in a biological system, is an important strategy for deciphering cell function, directing cell fate, and reprogramming cell behavior. With the advancement of nanotechnology, many researchers use nanoparticles (NPs) to break through biological barriers to achieving efficient targeted delivery in biological systems, bringing a new way to realize efficient targeted drug delivery in biological systems. With a similar size to many biomolecules, NPs possess excellent physical and chemical properties and a certain targeting ability after functional modification on the surface of NPs. Currently, intracellular cargo delivery based on NPs has emerged as an important strategy for genome editing regimens and cell therapy. Although researchers can successfully deliver NPs into biological systems, many of them are delivered very inefficiently and are not specifically targeted. Hence, the development of efficient, target-capable, and safe nanoscale drug delivery systems to deliver therapeutic substances to cells or organs is a major challenge today. In this review, on the basis of describing the research overview and classification of NPs, we focused on the current research status of intracellular cargo delivery based on NPs in biological systems, and discuss the current problems and challenges in the delivery process of NPs in biological systems.

HDL and chronic kidney disease

Low HDL-cholesterol (HDL-C) concentrations are a typical trait of the dyslipidemia associated with chronic kidney disease (CKD). In this condition, plasma HDLs are characterized by alterations in structure and function, and these particles can lose their atheroprotective functions, e.g., the ability to promote cholesterol efflux from peripheral cells, anti-oxidant and anti-inflammatory proprieties and they can even become dysfunctional, i.e., exactly damaging. The reduction in plasma HDL-C levels appears to be the only lipid alteration clearly linked to the progression of renal disease in CKD patients. The association between the HDL system and CKD development and progression is also supported by the presence of genetic kidney alterations linked to HDL metabolism, including mutations in the APOA1, APOE, APOL and LCAT genes. Among these, renal disease associated with LCAT deficiency is well characterized and lipid abnormalities detected in LCAT deficiency carriers mirror the ones observed in CKD patients, being present also in acquired LCAT deficiency. This review summarizes the major alterations in HDL structure and function in CKD and how genetic alterations in HDL metabolism can be linked to kidney dysfunction. Finally, the possibility of targeting the HDL system as possible strategy to slow CKD progression is reviewed.

KLKB1 and CLSTN2 are associated with HDL-mediated cholesterol efflux capacity in a genome-wide association study

BACKGROUND AND AIMS

HDL-mediated cholesterol efflux capacity (CEC) may protect from cardiovascular disease. Thus, we aimed to identify its genetic and non-genetic determinants.

METHODS

We measured CEC to 2% apolipoprotein B-depleted serum using BODIPY-cholesterol and cAMP-stimulated J774A.1 macrophages using serum samples from 4,981 participants in the German Chronic Kidney Disease (GCKD) study. Variance of CEC explained by clinical and biochemical parameters in a multivariable linear regression model was calculated by proportional marginal variance decomposition. A genome-wide association study with 7,746,917 variants was performed based on an additive genetic model. The main model was adjusted for age, sex and principal components 1-10. Further models were selected for sensitivity analysis and to reduce residual variance by known CEC pathways.

RESULTS

Variables that explained 1% and more of the variance of CEC were concentrations of triglycerides (12.9%), HDL-cholesterol (11.8%), LDL-cholesterol (3.0%), apolipoprotein A-IV (2.8%), PCSK9 (1.0%), and eGFR (1.0%). The KLKB1 (chr4) and APOE/C1 (chr19) loci were genome-wide significantly (p < 5x10-8) associated with CEC in our main model (p = 8.8x10-10 and p = 3.3x10-10, respectively). KLKB1 remained significantly associated after additional adjustment for either kidney parameters, HDL-cholesterol, triglycerides or apolipoprotein A-IV concentrations, while the APOE/C1 locus was not significantly associated anymore after adjustment for triglycerides. Adjustment for triglycerides also revealed an association with the CLSTN2 locus (chr3; p = 6.0x10-9).

CONCLUSIONS

We identified HDL-cholesterol and triglycerides as the main determinants of CEC. Furthermore, we newly found a significant association of CEC with the KLKB1 and the CLSTN2 locus and confirmed the association with the APOE/C1 locus, likely mediated by triglycerides.

Effect of high density lipoprotein cholesterol (HDL-C) on renal outcome in patients with nephrotic syndrome complicated with steroid-induced diabetes mellitus(SIDM)

OBJECTIVE

We aimed to investigate the renal prognosis of patients with idiopathic nephrotic syndrome (INS) complicated with steroid-induced diabetes mellitus (SIDM), the association of high-density lipoprotein cholesterol (HDL-C) before glucocorticoid treatment with renal prognosis, and the risk for persistent diabetes among patients with INS who had withdrawn from steroid therapy.

MATERIALS AND METHODS

We retrospectively analyzed 239 patients with INS complicated with SIDM at the National Clinical Research Center of Kidney Diseases, Jinling Hospital, from January 2008 to December 2019. The primary endpoint was the composite renal outcome defined as the development of end-stage renal disease (ESRD) or a 50% decrease in estimated glomerular filtration rate (eGFR) for more than 24 months after glucocorticoid withdrawal. The secondary endpoint was persistent diabetes, defined as fulfilling the criteria for diagnosing diabetes or using antidiabetic medications for at least 24 months after glucocorticoid withdrawal.

RESULTS

After glucocorticoid withdrawal for over 24 months, 35 (14.6%) patients reached the composite renal endpoint: end-stage renal disease (n = 14) or a 50% decrease in eGFR (n = 21). Before glucocorticoid therapy, a level of HDL-C greater than 1.45 mmol/L worsened renal survival in patients with INS complicated with SIDM. The log₁₀ the level of HDL-C before glucocorticoid treatment was an independent risk factor for the renal outcome. A prediction model was generated: Hazard ratio (renal outcome) = 0.94 * hypertension before glucocorticoid therapy + 2.29 * log₁₀ level of HDL-C before glucocorticoid treatment + 0.90 * the grade of interstitial tubule injury (AUROC, 0.75; 95% CI, 0.63 to 0.87; P < 0.01). Meanwhile, a level of fasting plasma glucose (FPG) before glucocorticoid treatment greater than 5.2 mmol/L enhanced the likelihood of persistent diabetes for at least 24 months after glucocorticoid withdrawal.

CONCLUSIONS

Increased level of HDL-C before glucocorticoid therapy was independently associated with a higher risk for renal outcome and thus may be useful in the renal prognosis of patients with INS complicated with SIDM.

Chronic Kidney Disease and Its Clinical Correlates in a Rural Community in Southwestern Nigeria

Chronic kidney disease (CKD) is a burgeoning problem globally, and more than a billion adults were affected as of 2016, with 1.2 million people dying from renal failure in 2017. To arrest the seemingly relentless progression of CKD to renal failure, there is a need to detect CKD early in the community. A community-based study was carried out to look at the prevalence and risk factors of CKD. Anthropometric and other clinical variables were measured. Blood samples were taken for determining creatinine, uric acid, urea, and lipids. CKD was defined as an estimated glomerular filtration rate of ≤60 mL/min/1.73 m2. Electrocardiograms and renal ultrasound scans were performed. In total, 201 people were recruited. Those with CKD had a male:female ratio of 1:3.9 and were older. The prevalence of autosomal-dominant polycystic kidney disease and CKD was 531.9 persons/100,000 population and 46.3%, respectively. Systolic blood pressure, pulse pressure, total cholesterol, triglycerides, high-density lipoprotein (HDL), uric acid, QTc interval, and electrocardiographic left ventricular hypertrophy were higher in those with CKD. Age, female sex, and HDL were independently associated with CKD. There was a steep rise in CKD at the community level. Increased awareness of CKD and prompt interventions are therefore imperative.

Kidney and lipids: novel potential therapeutic targets for dyslipidemia in kidney disease?

INTRODUCTION

Altered lipid distribution and metabolism may lead to the development and/or progression of chronic kidney disease (CKD). Dyslipidemia is a major risk factor for CKD and increases the risk of cardiovascular events and mortality. Therefore, lipid-lowering treatments may decrease cardiovascular risk and prevent death.

AREAS COVERED

Key players involved in regulating lipid accumulation in the kidney; contribution of lipids to CKD progression, lipotoxicity, and mitochondrial dysfunction in kidney disease; recent therapeutic approaches for dyslipidemia.

EXPERT OPINION

The precise mechanisms for regulating lipid metabolism, particularly in kidney disease, are poorly understood. Guidelines for lipid-lowering therapy for CKD are controversial. Several hypolipemic therapies are available, but compared to others, statin therapy is the most common. No clinical trial has evaluated the efficacy of proprotein convertase subtilisin/kexin type 9 inhibitors (PCSK9i) in preventing cardiovascular events or improving kidney function among patients with CKD or kidney transplant recipients. Attractive alternatives, such as PCSK9-small interfering RNA (siRNA) molecules or evinacumab are available. Additionally, several promising agents, such as cyclodextrins and the FXR/TGR5 dual agonist, INT-767, can improve renal lipid metabolism disorders and delay CKD progression. Drugs targeting mitochondrial dysfunction could be an option for the treatment of dyslipidemia and lipotoxicity, particularly in renal diseases.

Factors associated with renal function state transitions: A population-based community survey in Taiwan

Background

Understanding renal function state transition risk and associated factors in community residences is vital for appropriate preventive and care actions. We aim to investigate factors affecting renal function state transitions through 10-year longitudinal community screening surveys.

Methods

The prospective cohort study included participants who attended the screening program ≥2 times from 2001 to 2009 and were divided into two cohorts: those with baseline estimated glomerular filtration rate (eGFR) ≥60 (n = 46,278) and those with eGFR 59-30 mL/min/1.73 m² (n = 4,656). We applied the illness-death model to identify associated factors with eGFR <60 and death for the cohort with baseline eGFR ≥60 and eGFR <30 and death for that with baseline eGFR ≥59-30.

Results

Among the followed-up participants, 3,018 (6.5%) in the cohort of baseline eGFR ≥60 mL/min/1.73 m² and 322 (6.9%) in the cohort of eGFR 59-30 mL/min/1.73 m² experienced renal function state transition during a median over 7-year follow-up. Besides eGFR and grade of proteinuria, diabetes mellitus (adding nearly 50% hazard rate) is the main factor associated with both state transitions. Other early-phase eGFR state transition risk factors were metabolic syndrome score, triglyceride, uric acid, fasting blood sugar, and high-density lipoprotein cholesterol. Males, poor hemoglobin, high triglyceride, and high low-density lipoprotein cholesterol were all linked with the late-phase eGFR state transition hazard rate.

Conclusion

The study developed the state transition functions for community participants with varying renal function levels. Further actions to develop precision screening plans and services that incorporate personal risk factors and state transition risks are necessary.

Association of neutrophil-to-lymphocyte ratio with renal impairment among patients with acute gouty arthritis

OBJECTIVE

Gouty arthritis (GA) is an inflammatory disease, and renal impairment may occur to varying degrees with the progress of disease. The neutrophil-to-lymphocyte ratio (NLR) is an inflammatory marker. In this study, we aimed to explore the association between NLR and renal impairment in GA.

MATERIALS AND METHODS

The subjects comprised 499 patients with gouty arthritis (GA) (473 men, 26 women; age range, 39-61 years old) from our hospital. They were divided into a chronic kidney disease (CKD) group (n = 206) and non-CKD group (n = 293) according to the glomerular filtration rate. Blood samples were collected during the gout flares. The differences in NLR, general data, and laboratory indexes of patients with GA between the two groups were compared, such as serum uric acid (SUA), serum creatinine (SCREA), erythrocyte sedimentation rate (ESR), C-reactive protein (CRP), high-density lipoprotein (HDL), and low-density lipoprotein (LDL).

RESULTS

NLR (3.38 vs. 2.38 (p < 0.001)) was higher in the CKD group, compared to the non-CKD group. Similarly, both SUA (527 vs. 507 (p < 0.05)) and SCREA (122 vs. 87 (p < 0.001)) were higher in the CKD group than in the non-CKD group. Multivariate logistic regression analysis showed that NLR (OR = 1.122, p < 0.05), age, hypertension, and SUA were risk factors for CKD in patients with GA, although HDL and HGB were protective factors. The receiver operating characteristic (ROC) curve analysis indicated that the area under the curve of NLR for predicting CKD in patients with GA was 0.646 (95% CI 0.597-0.694).

CONCLUSION

Our data showed that NLR might be an important potential factor for evaluating renal impairment in GA during flares.

PCSK9 and Cardiovascular Disease in Individuals with Moderately Decreased Kidney Function

Background and objectives: Proprotein convertase subtilisin/kexin type 9 (PCSK9) is a key regulator of lipid homeostasis. Studies investigating the association between PCSK9 and cardiovascular disease in large cohorts of CKD patients are limited. Design, setting, participants, and measurements: The association of PCSK9 concentrations with prevalent and incident cardiovascular disease was investigated in 5,138 Caucasians of the German Chronic Kidney Disease study with a median follow-up of 6.5 years. Inclusion criteria were eGFR of 30-60 mL/min/1.73 m² or an eGFR>60 mL/min/1.73m² in the presence of overt proteinuria (urine albumin-creatinine ratio >300mg/g or equivalent). Prevalent cardiovascular disease was defined as history of non-fatal myocardial infarction, coronary artery bypass grafting, percutaneous transluminal coronary angioplasty, carotid arteries interventions and stroke. Incident major adverse cardiovascular disease events included death from cardiovascular causes, acute non-fatal myocardial infarction and non-fatal stroke. Results: Median PCSK9 concentration in the cohort was 285 ng/mL (interquartile range 231-346 ng/mL). There was no association between PCSK9 concentrations and baseline eGFR and albuminuria. With each 100 ng/ml increment of PCSK9, the odds for prevalent cardiovascular disease (n=1,284) was 1.22-fold (95%CI 1.12-1.34, p<0.001) higher in a model with extended adjustment for major confounders. This association was stronger in non-statin than statin-users (p-value for interaction=0.009). During follow-up 474 individuals experienced a major adverse cardiovascular disease event and participants in PCSK9 quartiles 2 to 4 had a 32%-47% higher risk compared to quartile 1 (p<0.05). Subgroup analysis revealed this association was restricted to those participants who already had cardiovascular disease at baseline (all HR>1.75, p<0.05). In addition, PCSK9 showed a valuable gain in classification accuracy both for prevalent cardiovascular disease (NRI=0.27, 95%CI:0.20-0.33) and incident major adverse cardiovascular disease events during follow-up (NRI=0.10, 95%CI:0.008-0.21) when added to an extended adjustment model. Conclusions: Our findings reveal no relation of PCSK9 with baseline eGFR and albuminuria, but a significant association between higher PCSK9 concentrations and risk of cardiovascular disease independent of traditional risk factors including LDL-cholesterol levels.

The metabolic signature of cardiovascular disease and arterial calcification in patients with chronic kidney disease

BACKGROUND AND AIMS

The relationship between chronic kidney disease (CKD) and cardiovascular events is well-established. Clinically recognised risk factors of cardiovascular disease cannot fully explain this association. The objective of the present cross-sectional study was to investigate associations between serum metabolites and prevalent cardiovascular disease, as well as subclinical cardiovascular disease measured as coronary artery calcium score (CACS) in patients with CKD.

METHODS

More than 200 preselected metabolites were quantified using nuclear magnetic resonance spectroscopy in 725 patients and 174 controls from the Copenhagen CKD Cohort. CACS was determined by computed tomography.

RESULTS

Mean age of patients was 57.8 years, and 444 (61.3%) were men. Most of patients had hypercholesterolemia, and 133 (18.3%) had type 2 diabetes. Overall, 85 metabolites were significantly associated with prevalent cardiovascular disease in a model adjusted for eGFR, age, and sex, as well as Bonferroni correction for multiple testing (p < 0.001). After further adjusting for diabetes, BMI, smoking, and cholesterol-lowering medication, the significance was lost for all but six metabolites (concentration of ApoA-1, cholesterol in total HDL and HDL2, total lipids and phospholipids in large HDL particles, and the ratio of phospholipids to total lipids in smaller VLDL particles). Of the 85 metabolites associated with prevalent cardiovascular disease, 71 were also associated with CACS in a similar pattern. Yet, in the model adjusted for all seven cardiovascular risk factors, only serum glucose levels and the ratio of triglycerides to total lipids in larger LDL particles remained significant.

CONCLUSIONS

In patients with CKD, associations with prevalent cardiovascular disease were mainly found for HDL-related metabolites, while CACS was associated with glucose levels and increased triglycerides to total lipids ratio in LDL particles.

Using Machine Learning to Evaluate the Role of Microinflammation in Cardiovascular Events in Patients With Chronic Kidney Disease

Background

Lipid metabolism disorder, as one major complication in patients with chronic kidney disease (CKD), is tied to an increased risk for cardiovascular disease (CVD). Traditional lipid-lowering statins have been found to have limited benefit for the final CVD outcome of CKD patients. Therefore, the purpose of this study was to investigate the effect of microinflammation on CVD in statin-treated CKD patients.

Methods

We retrospectively analysed statin-treated CKD patients from January 2013 to September 2020. Machine learning algorithms were employed to develop models of low-density lipoprotein (LDL) levels and CVD indices. A fivefold cross-validation method was employed against the problem of overfitting. The accuracy and area under the receiver operating characteristic (ROC) curve (AUC) were acquired for evaluation. The Gini impurity index of the predictors for the random forest (RF) model was ranked to perform an analysis of importance.

Results

The RF algorithm performed best for both the LDL and CVD models, with accuracies of 82.27% and 74.15%, respectively, and is therefore the most suitable method for clinical data processing. The Gini impurity ranking of the LDL model revealed that hypersensitive C-reactive protein (hs-CRP) was highly relevant, whereas statin use and sex had the least important effects on the outcomes of both the LDL and CVD models. hs-CRP was the strongest predictor of CVD events.

Conclusion

Microinflammation is closely associated with potential CVD events in CKD patients, suggesting that therapeutic strategies against microinflammation should be implemented to prevent CVD events in CKD patients treated by statin.

APOL1 Risk Variants Associated with Serum Albumin in a Population-Based Cohort Study

INTRODUCTION

The association of apolipoprotein L1 (APOL1) nephropathy risk variants (APOL1), unique to African-ancestry (African-American [AA]) populations, with systemic inflammation, a contributor to chronic kidney disease (CKD) and end-stage kidney disease (ESKD) is ill-defined. This study aimed to describe the role of inflammatory markers in the relationship between APOL1 and incident kidney outcomes using a prospective cohort study.

METHODS

APOL1 high-risk status under a recessive genetic model was studied in 10,605 AA adults aged ≥45 years from the Reasons for Geographic and Racial Differences in Stroke study. The primary variables of interest were inflammatory markers: C-reactive protein (mg/dL), white blood cell count (cells/mm3), and serum albumin (sALB) (mg/dL). High inflammation status was defined if at least one of these inflammatory markers exceeded clinical threshold. The association between APOL1 and biomarkers were assessed using regression models adjusting for age, sex, ancestry, hypertension, lipid medications, albumin-to-creatinine ratio, and estimated glomerular filtration rate (eGFR). Models were stratified by diabetes status. We identified incident ESKD using USRDS linkage, and we defined incident CKD as an eGFR <60 mL/min/1.73 m2 and ≥25% decline in the eGFR and normal baseline eGFR and tested for mediation of APOL1 and outcomes by biomarkers using the causal inference approach.

RESULTS

Among 7,151 participants with data available on all inflammation markers, 4,479 participants had ≥1 marker meeting the clinical threshold. APOL1 high-risk status was associated with lower adjusted odds of reduced sALB {odds ratio (OR) (95% confidence interval [CI]): 0.59 [0.36, 0.96])}, and this association was significant in people with diabetes (OR [95% CI]: 0.40 [0.18, 0.89]) but not in those without diabetes. There was no association of APOL1 high-risk status with other markers or high inflammation status. APOL1 was independently associated with ESKD (OR [95% CI] = 1.78 [1.28, 2.48]) and CKD (OR [95% CI] = 1.38 [1.00, 1.91]). On mediation analysis, the direct effect between APOL1 and ESKD strengthened after accounting for sALB, but the estimated mediated effect was not statistically significant (OR [95% CI]: 0.98 [0.92, 1.05], p = 0.58).

CONCLUSION

APOL1 high-risk variants were associated with sALB. However, sALB did not statistically mediate the association between APOL1 and incident ESKD.

Altered vitamin K biodistribution and metabolism in experimental and human chronic kidney disease

Chronic kidney disease (CKD) is accompanied with extensive cardiovascular calcification, in part correlating with functional vitamin K deficiency. Here, we sought to determine causes for vitamin K deficiency beyond reduced dietary intake. Initially, vitamin K uptake and distribution into circulating lipoproteins after a single administration of vitamin K1 plus K2 (menaquinone 4 and menaquinone 7, respectively) was determined in patients on dialysis therapy and healthy individuals. The patients incorporated very little menaquinone 7 but more menaquinone 4 into high density lipoprotein (HDL) and low-density lipoprotein particles than did healthy individuals. In contrast to healthy persons, HDL particles from the patients could not be spiked with menaquinone 7 in vitro and HDL uptake was diminished in osteoblasts. A reduced carboxylation activity (low vitamin K activity) of uremic HDL particles spiked with menaquinone 7 vs. that of controls was confirmed in a bioassay using human primary vascular smooth muscle cells. Kidney menaquinone 4 tissue levels were reduced in 5/6-nephrectomized versus sham-operated C57BL/6 mice after four weeks of a vitamin K rich diet. From the analyzed enzymes involved in vitamin K metabolism, kidney HMG-CoA reductase protein was reduced in both rats and patients with CKD. In a trial on the efficacy and safety of atorvastatin in 1051 patients with type 2 diabetes receiving dialysis therapy, no pronounced vitamin K deficiency was noted. However, the highest levels of PIVKA-II (biomarker of subclinical vitamin K deficiency) were noted when a statin was combined with a proton pump inhibitor. Thus, profound disturbances in lipoprotein mediated vitamin K transport and metabolism in uremia suggest that menaquinone 7 supplementation to patients on dialysis therapy has reduced efficacy.

Supportive Effects of Online Hemodiafiltration Therapy on the Nutritional State and Lipid Profile in Very Elderly Dialysis Patients

INTRODUCTION

Online hemodiafiltration (HDF) therapy has been recognized as one of the potential dialysis modalities. However, the long-term effects of online HDF therapy on very elderly dialysis patients older than 75 years have yet to be fully elucidated.

METHODS

Seventy-four very elderly patients older than 75 years undergoing maintenance dialysis therapy were studied retrospectively. Twenty-four (mean ± SE, 81.5 ± 1.0 years) were treated by predilution online HDF, and fifty (81.2 ± 0.6 years) were treated by conventional hemodialysis (HD) for 3 years. Laboratory data related to the nutritional state and lipid profile were collected. Body composition was measured by a bioelectrical impedance method.

RESULTS

Dry weight and body mass index decreased in HD patients (2.9%, p = 0.003 and 3.1%, p = 0.001, respectively), while no significant changes were found in online HDF patients. Serum albumin levels reduced in both HD and online HDF groups (3.5%, p = 0.003 and 2.9%, p = 0.026, respectively). The geriatric nutritional risk index decreased in HD patients (3.0%, p < 0.001), while no significant change was shown in online HDF patients. Body composition analysis demonstrated a significant decrease in intracellular water and increases in extracellular water and edema ratio in both groups. Fat mass and %fat showed significant decreases in HD patients (8.1%, p = 0.003 and 7.3%, p = 0.003, respectively), but no significant changes in online HDF patients. Among laboratory data, serum high-density lipoprotein cholesterol levels did not change in HD patients. However, the levels elevated significantly (10.6%, p = 0.03) in online HDF patients.

DISCUSSION/CONCLUSION

These results indicated that the time-dependent deterioration of the nutritional state in very elderly dialysis patients was inevitable; however, such deterioration was not prominent in online HDF patients. Moreover, the lipid profile showed unique changes in online HDF patients. In order to treat very elderly dialysis patients, online HDF should preferentially be taken into consideration because the maintenance of general condition seems to be a practical goal against the natural time-dependent deterioration.

Metabolic Syndrome, and Not Obesity, Is Associated with Chronic Kidney Disease

INTRODUCTION

Obese (OB) patients are at increased risk of chronic kidney disease, but it is still unclear whether this can be attributed to obesity per se or to the associated metabolic derangements. The aim of this study was to evaluate the relative impact of obesity and metabolic syndrome (MS) on kidney disease.

METHODS

This is a cross-sectional study based on data obtained in the 2005-2016 cycles of the National Health and Nutrition Examination Survey. We included all adult participants with available data on body mass index, estimated glomerular filtration rate (eGFR), urine albumin to creatinine ratio (UACR), and each of the MS components. Primary outcomes were eGFR <60 mL/min, UACR ≥30 mg/g, or a combination of the two.

RESULTS

The studied population comprised 12,335 participants. OB participants without MS (OB+ MS-) were younger and more commonly female. After adjustment for potential confounders, compared with OB- MS- participants, an increased prevalence of albuminuria and reduced eGFR were present in both OB- MS+ groups and the OB+ MS+ groups, but not in the OB+ MS- groups. When each of the MS components was evaluated separately, elevated blood pressure and low high-density lipoprotein cholesterol were associated with both UACR and reduced eGFR, while elevated blood glucose and triglycerides were only associated with UACR. Waist circumference was not associated with any of the renal outcomes.

DISCUSSION/CONCLUSION

This large cross-sectional study suggests that MS and not obesity is associated with kidney damage and that the OB+ MS- phenotype does not seem to carry an increased risk of kidney disease.

Lysis reagents, cell numbers, and calculation method influence high-throughput measurement of HDL-mediated cholesterol efflux capacity

HDL-mediated cholesterol efflux capacity (CEC) may protect against cardiovascular disease. However, CEC assays are not standardized, hampering their application in large cohorts and comparison between studies. To improve standardization, we systematically investigated technical differences between existing protocols that influence assay performance that have not been previously addressed. CEC was measured in 96-well plates using J774A.1 macrophages labeled with BODIPY-cholesterol and incubated for 4 h with 2% apolipoprotein B-depleted human serum. The time zero method, which calculates CEC using control wells, and the per-well method, which calculates CEC based on the actual content of BODIPY-cholesterol in each well, were compared in 506 samples. We showed that the per-well method had a considerably lower sample rejection rate (4.74% vs. 13.44%) and intra-assay (4.48% vs. 5.28%) and interassay coefficients of variation (two controls: 7.85%, 9.86% vs. 13.58%, 15.29%) compared with the time zero method. Correction for plate-to-plate differences using four controls on each plate also improved assay performance of both methods. In addition, we observed that the lysis reagent used had a significant effect. Compared with cholic acid, lysis with sodium hydroxide results in higher (P = 0.0082) and Triton X-100 in lower (P = 0.0028) CEC values. Furthermore, large cell seeding errors (30% variation) greatly biased CEC for both referencing methods (P < 0.0001) as measured by a resazurin assay. In conclusion, lysis reagents, cell numbers, and assay setup greatly impact the quality and reliability of CEC quantification and should be considered when this method is newly established in a laboratory.

Dietary Lipids and Dyslipidemia in Chronic Kidney Disease

The progression of chronic kidney disease (CKD) leads to altered lipid metabolism. CKD patients exhibit high blood triglyceride (TG) levels, reduced concentrations and functionality of high-density lipoproteins (HDL), and elevated levels of atherogenic small, dense, low-density lipoproteins (sdLDL). Disorders of lipid metabolism and other metabolic disturbances place CKD patients at high risk for cardiovascular disease (CVD). Extensive evidence supports the cardioprotective effects of unsaturated fatty acids, including their beneficial effect on serum cholesterol and TG levels. Dietary lipids might therefore be especially important in the nutritional management of CKD. We review current dietary recommendations for fat intake by CKD patients and suggest potential nutritional interventions by emphasizing dietary lipids that might improve the blood lipid profile and reduce cardiovascular risk in CKD.

Potential role of anti-inflammatory HDL subclasses in metabolic unhealth/obesity

High-density lipoprotein (HDL) particles comprising heterogeneous subclasses of different functions exert anti-inflammatory effects by interacting with immune-response cells. However, the relationship of HDL subclasses with immune-response cells in metabolic unhealth/obesity has not been defined clearly. The purpose of this study was to delineate the relational changes of HDL subclasses with immune cells and inflammatory markers in metabolic unhealth/obesity to understand the role of anti-inflammatory HDL subclasses. A total of 316 participants were classified by metabolic health. HDL subclasses were detected by microfluidic chip electrophoresis. White blood cell (WBC) counts and lymphocytes were assessed using automatic haematology analyser. Levels of high-sensitivity C-reactive protein (hs-CRP) and interleukin 6 (IL-6) were measured. In our study, not only the distribution of HDL subclasses, but also HDL-related structural proteins changed with the deterioration of metabolic disease. Moreover, lymphocytes and inflammation factors significantly gradually increased. The level of HDL2b was negatively associated with WBC, lymphocytes and hs-CRP in multivariable linear regression analysis. In multinomial logistic regression analysis, high levels of HDL3 and low levels of HDL2b increased the probability of having an unfavourable metabolic unhealth/obesity status. We supposed that HDL2b particles may play anti-inflammation by negatively regulating lymphocytes activation. HDL2b may be a therapeutic target for future metabolic disease due to the anti-inflammatory effects.

High-Density Lipoproteins in Kidney Disease

Decades of epidemiological studies have established the strong inverse relationship between high-density lipoprotein (HDL)-cholesterol concentration and cardiovascular disease. Recent evidence suggests that HDL particle functions, including anti-inflammatory and antioxidant functions, and cholesterol efflux capacity may be more strongly associated with cardiovascular disease protection than HDL cholesterol concentration. These HDL functions are also relevant in non-cardiovascular diseases, including acute and chronic kidney disease. This review examines our current understanding of the kidneys’ role in HDL metabolism and homeostasis, and the effect of kidney disease on HDL composition and functionality. Additionally, the roles of HDL particles, proteins, and small RNA cargo on kidney cell function and on the development and progression of both acute and chronic kidney disease are examined. The effect of HDL protein modification by reactive dicarbonyls, including malondialdehyde and isolevuglandin, which form adducts with apolipoprotein A-I and impair proper HDL function in kidney disease, is also explored. Finally, the potential to develop targeted therapies that increase HDL concentration or functionality to improve acute or chronic kidney disease outcomes is discussed.

HDL in Atherosclerotic Cardiovascular Disease: In Search of a Role

For a long time, high-density lipoprotein cholesterol (HDL-C) has been regarded as a cardiovascular disease (CVD) protective factor. Recently, several epidemiological studies, while confirming low plasma levels of HDL-C as an established predictive biomarker for atherosclerotic CVD, indicated that not only people at the lowest levels but also those with high HDL-C levels are at increased risk of cardiovascular (CV) mortality. This “U-shaped” association has further fueled the discussion on the pathophysiological role of HDL in CVD. In fact, genetic studies, Mendelian randomization approaches, and clinical trials have challenged the notion of HDL-C levels being causally linked to CVD protection, independent of the cholesterol content in low-density lipoproteins (LDL-C). These findings have prompted a reconsideration of the biological functions of HDL that can be summarized with the word “HDL functionality”, a term that embraces the many reported biological activities beyond the so-called reverse cholesterol transport, to explain this lack of correlation between HDL levels and CVD. All these aspects are summarized and critically discussed in this review, in an attempt to provide a background scenario for the “HDL story”, a lipoprotein still in search of a role.

Lipoproteins in chronic kidney disease: from bench to bedside

Chronic kidney disease (CKD) is associated with high cardiovascular risk. CKD patients exhibit a specific lipoprotein pattern termed 'uraemic dyslipidaemia', which is characterized by rather normal low-density lipoprotein cholesterol, low high-density lipoprotein cholesterol, and high triglyceride plasma levels. All three lipoprotein classes are involved in the pathogenesis of CKD-associated cardiovascular diseases (CVDs). Uraemia leads to several modifications of the structure of lipoproteins such as changes of the proteome and the lipidome, post-translational protein modifications (e.g. carbamylation) and accumulation of small-molecular substances within the lipoprotein moieties, which affect their functionality. Lipoproteins from CKD patients interfere with lipid transport and promote inflammation, oxidative stress, endothelial dysfunction as well as other features of atherogenesis, thus contributing to the development of CKD-associated CVD. While, lipid-modifying therapies play an important role in the management of CKD patients, their efficacy is modulated by kidney function. Novel therapeutic agents to prevent the adverse remodelling of lipoproteins in CKD and to improve their functional properties are highly desirable and partially under development.

Kidney injury-mediated disruption of intestinal lymphatics involves dicarbonyl-modified lipoproteins

Kidney disease affects intestinal structure and function. Although intestinal lymphatics are central in absorption and remodeling of dietary and synthesized lipids/lipoproteins, little is known about how kidney injury impacts the intestinal lymphatic network, or lipoproteins transported therein. To study this, we used puromycin aminoglycoside-treated rats and NEP25 transgenic mice to show that proteinuric injury expanded the intestinal lymphatic network, activated lymphatic endothelial cells and increased mesenteric lymph flow. The lymph was found to contain increased levels of cytokines, immune cells, and isolevuglandin (a highly reactive dicarbonyl) and to have a greater output of apolipoprotein AI. Plasma levels of cytokines and isolevuglandin were not changed. However, isolevuglandin was also increased in the ileum of proteinuric animals, and intestinal epithelial cells exposed to myeloperoxidase produced more isolevuglandin. Apolipoprotein AI modified by isolevuglandin directly increased lymphatic vessel contractions, activated lymphatic endothelial cells, and enhanced the secretion of the lymphangiogenic promoter vascular endothelial growth factor-C by macrophages. Inhibition of isolevuglandin synthesis by a carbonyl scavenger reduced intestinal isolevuglandin adduct level and lymphangiogenesis. Thus, our data reveal a novel mediator, isolevuglandin modified apolipoprotein AI, and uncover intestinal lymphatic network structure and activity as a new pathway in the crosstalk between kidney and intestine that may contribute to the adverse impact of kidney disease on other organs.

Factors predicting decline in renal function and kidney volume growth in autosomal dominant polycystic kidney disease: a prospective cohort study (Japanese Polycystic Kidney Disease registry: J-PKD)

BACKGROUND

Factors affecting decline in renal function and cyst growth in patients with autosomal polycystic kidney disease (ADPKD) are not fully described, particularly in Japan.

METHODS

This was the first multi-facility, prospective, observational cohort study conducted in ADPKD patients at 14 centers in Japan. Patients in the J-PKD registry were assessed from December 2009 to June 2012 (follow-up until June 2017). Patients' data including estimated glomerular filtration rate (eGFR) and total kidney volume (TKV) were assessed initially and a maximum of five times annually. Contributing factors to eGFR decline and TKV growth were identified using multiple linear regression analysis.

RESULTS

Of the 340 patients in the J-PKD registry, data analysis was performed for 192 patients in whom serial changes for both eGFR and TKV were obtained. eGFR slope, eGFR change, and TKV change values were as follows: - 2.7 (- 4.2 to - 1.5) (ml/min/1.73 m²/year), - 5.0 (- 9.6 to - 2.3) (%/year), and 4.78 (0.86-8.22) (%/year), respectively. Lower high-density lipoprotein (HDL) cholesterol was an independent predictor of eGFR decline, using both eGFR slope and change (P = 0.04, P = 0.02, respectively), whereas lower hemoglobin and higher uric acid were significantly associated with greater eGFR change only (P = 0.02, P = 0.002, respectively). Younger age and higher fasting blood sugar were independent predictors of greater TKV change (P = 0.01, P = 0.02, respectively).

CONCLUSIONS

This real-world study in Japan identified risk factors for renal function decline in ADPKD patients. These included lower HDL cholesterol, lower hemoglobin and higher uric acid for eGFR decline, and youth and higher blood sugar levels for TKV growth.

Impaired High-Density Lipoprotein Function in Patients With Heart Failure

Background

We recently showed that, in patients with heart failure, lower high‐density lipoprotein (HDL) cholesterol concentration was a strong predictor of death or hospitalization for heart failure. In a follow‐up study, we suggested that this association could be partly explained by HDL proteome composition. However, whether the emerging concept of HDL function contributes to the prognosis of patients with heart failure has not been addressed.

Methods and Results

We measured 3 key protective HDL function metrics, namely, cholesterol efflux, antioxidative capacity, and anti‐inflammatory capacity, at baseline and after 9 months in 446 randomly selected patients with heart failure from BIOSTAT‐CHF (A Systems Biology Study to Tailored Treatment in Chronic Heart Failure). Additionally, the relationship between HDL functionality and HDL proteome composition was determined in 86 patients with heart failure. From baseline to 9 months, HDL cholesterol concentrations were unchanged, but HDL cholesterol efflux and anti‐inflammatory capacity declined (both P<0.001). In contrast, antioxidative capacity increased (P<0.001). Higher HDL cholesterol efflux was associated with lower mortality after adjusting for BIOSTAT‐CHF risk models and log HDL cholesterol (hazard ratio, 0.81; 95% CI, 0.71–0.92; P=0.001). Other functionality measures were not associated with outcome. Several HDL proteins correlated with HDL functionality, mainly with cholesterol efflux. Apolipoprotein A1 emerged as the main protein associated with all 3 HDL functionality measures.

Conclusions

Better HDL cholesterol efflux at baseline was associated with lower mortality during follow‐up, independent of HDL cholesterol. HDL cholesterol efflux and anti‐inflammatory capacity declined during follow‐up in patients with heart failure. Measures of HDL function may provide clinical information in addition to HDL cholesterol concentration in patients with heart failure.

Lipoprotein Abnormalities in Chronic Kidney Disease and Renal Transplantation

Chronic kidney disease (CKD) is one of the most important risk factors for cardiovascular disease (CVD). Despite the kidney having no direct implications for lipoproteins metabolism, advanced CKD dyslipidemia is usually present in patients with CKD, and the frequent lipid and lipoprotein alterations occurring in these patients play a role of primary importance in the development of CVD. Although hypertriglyceridemia is the main disorder, a number of lipoprotein abnormalities occur in these patients. Different enzymes pathways and proteins involved in lipoprotein metabolism are impaired in CKD. In addition, treatment of uremia may modify the expression of lipoprotein pattern as well as determine acute changes. In renal transplantation recipients, the main lipid alteration is hypercholesterolemia, while hypertriglyceridemia is less pronounced. In this review we have analyzed lipid and lipoprotein disturbances in CKD and also their relationship with progression of renal disease. Hypolipidemic treatments may also change the natural history of CVD in CKD patients and may represent important strategies in the management of CKD patients.

High-Density Lipoproteins and the Kidney

Dyslipidemia is a typical trait of patients with chronic kidney disease (CKD) and it is typically characterized by reduced high-density lipoprotein (HDL)-cholesterol(c) levels. The low HDL-c concentration is the only lipid alteration associated with the progression of renal disease in mild-to-moderate CKD patients. Plasma HDL levels are not only reduced but also characterized by alterations in composition and structure, which are responsible for the loss of atheroprotective functions, like the ability to promote cholesterol efflux from peripheral cells and antioxidant and anti-inflammatory proprieties. The interconnection between HDL and renal function is confirmed by the fact that genetic HDL defects can lead to kidney disease; in fact, mutations in apoA-I, apoE, apoL, and lecithin–cholesterol acyltransferase (LCAT) are associated with the development of renal damage. Genetic LCAT deficiency is the most emblematic case and represents a unique tool to evaluate the impact of alterations in the HDL system on the progression of renal disease. Lipid abnormalities detected in LCAT-deficient carriers mirror the ones observed in CKD patients, which indeed present an acquired LCAT deficiency. In this context, circulating LCAT levels predict CKD progression in individuals at early stages of renal dysfunction and in the general population. This review summarizes the main alterations of HDL in CKD, focusing on the latest update of acquired and genetic LCAT defects associated with the progression of renal disease.

The minor C-allele of the rs2014355 variant in ACADS gene is associated with exercise-induced increase in HDL cholesterol levels in Taiwanese adults

We investigated the association between high-density lipoprotein cholesterol (HDL-C) and rs2014355 variant in the gene, short-chain acyl-coenzyme A dehydrogenase (ACADS) based on exercise habits.Data collected between 2008 and 2015 for individuals aged 30 to 70 years were available in the Taiwan Biobank (TWB) database. Backward stepwise linear regression was used to evaluate the associations of rs2014355 and exercise with HDL-C levels.We analyzed data of 5515 physically active and 4169 inactive biobank participants. The HDL-C concentrations were higher in the exercise compared to no exercise group (beta value, β = 1.79856; P < .0001). We observed that the test for interaction was significant for the ACADS rs2014355 variant and exercise (P for interaction =.0412). Multivariate analyses showed significant association between TC+CC genotype and HDL-C in the exercise (β = 1.09785; P value = .0146) compared to the no-exercise group (β = -0.03754, P = .9154).In summary, the association between HDL-C and exercise differed significantly with respect to ACADS rs2014355 genotypes. Compared to the TT genotype, the TC+CC genotype together with exercise was associated with higher levels of HDL-C.

Predictive value of triglyceride/high-density lipoprotein cholesterol for major clinical outcomes in advanced chronic kidney disease: a nationwide population-based study

Background

Dyslipidemia is an essential parameter in the prediction of cardiovascular disease (CVD). We aimed to explore whether lipid profiles could predict major outcomes in patients with advanced chronic kidney disease (CKD).

Methods

We retrospectively reviewed the National Health Insurance Service database for people who received nationwide health screening in 2009. All subjects exposed to a lipid-lowering agent before screening were excluded. The population was divided into control, early [estimated glomerular filtration rate (eGFR) 45-59 mL/min/1.73 m²] and advanced (eGFR <45 mL/min/1.73 m²) CKD groups. The hazard ratios (HRs) of outcomes were calculated using multivariate Cox regression models.

Results

A total of 3 634 873 participants were included in this study, with 404 298 (11.1%) and 66 805 (1.8%) having early and advanced CKD, respectively. For all populations, levels of triglyceride/high-density lipoprotein cholesterol (TG/HDL-C) showed a linear association with major cardiovascular and cerebrovascular events (MACCEs) and all-cause mortality, while low-density lipoprotein cholesterol (LDL-C) showed a different pattern of association with MACCEs (linear association) from all-cause mortality (U-shaped association). The significance between the levels of LDL-C and outcomes was attenuated in the advanced CKD group. For TG/HDL-C, although the significance was decreased, the linear patterns with both MACCEs and all-cause mortality were maintained in the advanced CKD group.

Conclusions

The pattern and significance of lipid profiles were different according to the grade of kidney function. TG/HDL-C should be additionally considered as a predictive marker for CVD and mortality along with LDL-C in patients with CKD.

Current Understanding of the Relationship of HDL Composition, Structure and Function to Their Cardioprotective Properties in Chronic Kidney Disease

In the general population, the ability of high-density lipoproteins (HDLs) to promote cholesterol efflux is a predictor of cardiovascular events, independently of HDL cholesterol levels. Although patients with chronic kidney disease (CKD) have a high burden of cardiovascular morbidity and mortality, neither serum levels of HDL cholesterol, nor cholesterol efflux capacity associate with cardiovascular events. Important for the following discussion on the role of HDL in CKD is the notion that traditional atherosclerotic cardiovascular risk factors only partially account for this increased incidence of cardiovascular disease in CKD. As a potential explanation, across the spectrum of cardiovascular disease, the relative contribution of atherosclerotic cardiovascular disease becomes less important with advanced CKD. Impaired renal function directly affects the metabolism, composition and functionality of HDL particles. HDLs themselves are a heterogeneous population of particles with distinct sizes and protein composition, all of them affecting the functionality of HDL. Therefore, a more specific approach investigating the functional and compositional features of HDL subclasses might be a valuable strategy to decipher the potential link between HDL, cardiovascular disease and CKD. This review summarizes the current understanding of the relationship of HDL composition, metabolism and function to their cardio-protective properties in CKD, with a focus on CKD-induced changes in the HDL proteome and reverse cholesterol transport capacity. We also will highlight the gaps in the current knowledge regarding important aspects of HDL biology.

Enrichment of apolipoprotein A-IV and apolipoprotein D in the HDL proteome is associated with HDL functions in diabetic kidney disease without dialysis

Background and aims

Diabetic kidney disease (DKD) is associated with lipid derangements that worsen kidney function and enhance cardiovascular (CVD) risk. The management of dyslipidemia, hypertension and other traditional risk factors does not completely prevent CVD complications, bringing up the participation of nontraditional risk factors such as advanced glycation end products (AGEs), carbamoylation and changes in the HDL proteome and functionality. The HDL composition, proteome, chemical modification and functionality were analyzed in nondialysis subjects with DKD categorized according to the estimated glomerular filtration rate (eGFR) and urinary albumin excretion rate (AER).

Methods

Individuals with DKD were divided into eGFR> 60 mL/min/1.73 m² plus AER stages A1 and A2 (n = 10) and eGFR< 60 plus A3 (n = 25) and matched by age with control subjects (eGFR> 60; n = 8).

Results

Targeted proteomic analyses quantified 28 proteins associated with HDL in all groups, although only 2 were more highly expressed in the eGFR< 60 + A3 group than in the controls: apolipoprotein D (apoD) and apoA-IV. HDL from the eGFR< 60 + A3 group presented higher levels of total AGEs (20%), pentosidine (6.3%) and carbamoylation (4.2 x) and a reduced ability to remove ¹⁴C-cholesterol from macrophages (33%) in comparison to HDL from controls. The antioxidant role of HDL (lag time for LDL oxidation) was similar among groups, but HDL from the eGFR< 60 + A3 group presented a greater ability to inhibit the secretion of IL-6 and TNF-alpha (95%) in LPS-elicited macrophages in comparison to the control group.

Conclusion

The increase in apoD and apoA-IV could contribute to counteracting the HDL chemical modification by AGEs and carbamoylation, which contributes to HDL loss of function in well-established DKD.

Dyslipidemia in Kidney Disorders: Perspectives on Mitochondria Homeostasis and Therapeutic Opportunities

To excrete body nitrogen waste and regulate electrolyte and fluid balance, the kidney has developed into an energy factory with only second to the heart in mitochondrial content in the body to meet the high-energy demand and regulate homeostasis. Energy supply from the renal mitochondria majorly depends on lipid metabolism, with programed enzyme systems in fatty acid β-oxidation and Krebs cycle. Renal mitochondria integrate several metabolic pathways, including AMPK/PGC-1α, PPARs, and CD36 signaling to maintain energy homeostasis for dynamic and static requirements. The pathobiology of several kidney disorders, including diabetic nephropathy, acute and chronic kidney injuries, has been primarily linked to impaired mitochondrial bioenergetics. Such homeostatic disruption in turn stimulates a pathological adaptation, with mitochondrial enzyme system reprograming possibly leading to dyslipidemia. However, this alteration, while rescuing oncotic pressure deficit secondary to albuminuria and dissipating edematous disorder, also imposes an ominous lipotoxic consequence. Reprograming of lipid metabolism in kidney injury is essential to preserve the integrity of kidney mitochondria, thereby preventing massive collateral damage including excessive autophagy and chronic inflammation. Here, we review dyslipidemia in kidney disorders and the most recent advances on targeting mitochondrial energy metabolism as a therapeutic strategy to restrict renal lipotoxicity, achieve salutary anti-edematous effects, and restore mitochondrial homeostasis.

Association Between Serum High-Density Lipoprotein Cholesterol Levels and Progression of Chronic Kidney Disease: Results From the KNOW-CKD

Background High-density lipoprotein cholesterol ( HDL -C) levels are generally decreased in patients with chronic kidney disease ( CKD ). However, studies on the relationship between HDL -C and CKD progression are scarce. Methods and Results We studied the association between serum HDL -C levels and the risk of CKD progression in 2168 participants of the KNOW - CKD (Korean Cohort Study for Outcome in Patients With Chronic Kidney Disease). The primary outcome was the composite of a 50% decline in estimated glomerular filtration rate from baseline or end-stage renal disease. The secondary outcome was the onset of end-stage renal disease. During a median follow-up of 3.1 (interquartile range, 1.6-4.5) years, the primary outcome occurred in 335 patients (15.5%). In a fully adjusted Cox model, the lowest category with HDL -C of <30 mg/dL (hazard ratio, 2.21; 95% CI, 1.30-3.77) and the highest category with HDL -C of ≥60 mg/dL (hazard ratio, 2.05; 95% CI , 1.35-3.10) were associated with a significantly higher risk of the composite renal outcome, compared with the reference category with HDL -C of 50 to 59 mg/dL. This association remained unaltered in a time-varying Cox analysis. In addition, a fully adjusted cubic spline model with HDL -C being treated as a continuous variable yielded similar results. Furthermore, consistent findings were obtained in a secondary outcome analysis for the development of end-stage renal disease. Conclusions A U-shaped association was observed between serum HDL -C levels and adverse renal outcomes in this large cohort of patients with CKD . Our findings suggest that both low and high serum HDL -C levels may be detrimental to patients with nondialysis CKD .

Lipid profiles and risk of major adverse cardiovascular events in CKD and diabetes: A nationwide population-based study

The association of lipid parameters with cardiovascular outcomes and the impact of kidney function on this association have not been thoroughly evaluated in chronic kidney disease (CKD) patients with diabetes. We reviewed the National Health Insurance Database of Korea, containing the data of 10,505,818 subjects who received routine check-ups in 2009. We analyzed the association of lipid profile parameters with major adverse cardiovascular events (MACEs) risk and all-cause mortality in a nationally representative cohort of 51,757 lipid-lowering medication-naïve patients who had CKD and diabetes. Advanced CKD patients with eGFR <30 mL/min/1.73 m² (n = 10,775) had lower serum total cholesterol (TC), low-density lipoprotein cholesterol (LDL-c), and high-density lipoprotein cholesterol (HDL-c) but higher non-HDL-c levels and triglyceride (TG) to HDL-c ratios. There was a positive linear association between serum LDL-c and MACE risk in both early and advanced CKD patients (P <0.001 for trend), except for the category of LDL-c 30–49 mg/dL in extremely low LDL-c subgroup analyses. A U-shaped relationship was observed between serum LDL-c and all-cause mortality (the 4^th and 8^th octile groups; lowest hazard ratio [HR] 0.96, 95% confidence interval [CI] 0.87–1.05 and highest HR 1.14, 95% CI 1.04–1.26, respectively). A similar pattern remained in both early and advanced CKD patients. The TG/HDL-c ratio categories showed a positive linear association for MACE risk in early CKD (P <0.001 for trend), but this correlation disappeared in advanced CKD patients. There was no correlation between the serum TG/HDL-c ratio and all-cause mortality in the study patients. The LDL-c level predicted the risk for MACEs and all-cause mortality in both early and advanced CKD patients with diabetes, although the patterns of the association differed from each other. However, the TG/HDL-c ratio categories could not predict the risk for either MACEs or all-cause mortality in advanced CKD patients with diabetes, except that the TG/HDL-c ratio predicted MACE risk in early CKD patients with diabetes.

Effects of exercise on residual renal function in patients undergoing peritoneal dialysis: A post-hoc analysis of a randomized controlled trial

We aimed to investigate the effects of exercise on renal outcomes in patients undergoing peritoneal dialysis (PD). In a post-hoc analysis of a randomized controlled trial of a 12-week home-based exercise program involving 47 patients undergoing PD, we excluded 18 patients with anuria and analyzed 13 and 16 patients in the usual care and exercise groups, respectively. The primary outcomes were weekly renal creatinine clearance (CCr) and urinary biomarkers: liver-type fatty acid-binding protein (L-FABP) and the microalbumin-to-creatinine ratio (ACR). Although the maintenance of weekly renal CCr in the exercise group was not significantly different compared with that in the usual care group (P = .09), urinary L-FABP levels (P = .02) and ACR (P = .04) were significantly decreased in the exercise group. To the best of our knowledge, this is the first study to demonstrate the beneficial effects of exercise on renal outcomes in patients undergoing PD.

The Role and Function of HDL in Patients with Chronic Kidney Disease and the Risk of Cardiovascular Disease

Chronic kidney disease (CKD) is a worldwide health problem with steadily increasing occurrence. Significantly elevated cardiovascular morbidity and mortality have been observed in CKD. Cardiovascular diseases are the most important and frequent cause of death of CKD patients globally. The presence of CKD is related to disturbances in lipoprotein metabolism whose consequences are dyslipidemia and the accumulation of atherogenic particles. CKD not only fuels the reduction of high-density lipoprotein (HDL) cholesterol concentration, but also it modifies the composition of this lipoprotein. The key role of HDL is the participation in reverse cholesterol transport from peripheral tissues to the liver. Moreover, HDL prevents the oxidation of low-density lipoprotein (LDL) cholesterol by reactive oxygen species (ROS) and protects against the adverse effects of oxidized LDL (ox-LDL) on the endothelium. Numerous studies have demonstrated the ability of HDL to promote the production of nitric oxide (NO) by endothelial cells (ECs) and to exert antiapoptotic and anti-inflammatory effects. Increasing evidence suggests that in patients with chronic inflammatory disorders, HDLs may lose important antiatherosclerotic properties and become dysfunctional. So far, no therapeutic strategy to raise HDL, or alter the ratio of HDL subfractions, has been successful in slowing the progression of CKD or reducing cardiovascular disease in patients either with or without CKD.

Lipid-modifying therapy in chronic kidney disease: Pathophysiological and clinical considerations

Chronic kidney disease (CKD), which affects >10% of the population worldwide, is associated with a dramatically increased rate of cardiovascular disease (CVD). More people with CKD will die from CVD than develop end-stage renal disease with dialysis-dependency. However, the contribution of classical atherosclerotic cardiovascular risk factors is less evident than in the general population. Particularly, the relationship between dyslipidemia and CVD morbidity and mortality in CKD patients is not as evident as in the general population. While LDL cholesterol-lowering drugs such as statins significantly reduce the rate of cardiovascular events in the general population, their role in patients with end-stage renal disease has been questioned. This could be caused by a shift from atherosclerotic to non-atherosclerotic CVD in patients with advanced CKD, which cannot be effectively prevented by lipid-lowering drugs. In addition, many lines of evidence suggest that impaired renal function directly affects the metabolism, composition and functionality of lipoproteins, which may affect their responsiveness to pharmacological interventions. In this review, we highlight the challenges for the therapeutic application of lipid-lowering treatment strategies in CKD and discuss why treatment strategies used in the general population cannot be applied uncritically to CKD patients.

Association of High-Density Lipoprotein Particles and High-Density Lipoprotein Apolipoprotein C-III Content With Cardiovascular Disease Risk According to Kidney Function: The Multi-Ethnic Study of Atherosclerosis

Background

Chronic kidney disease is associated with structural and compositional abnormalities in high‐density lipoprotein particles (HDLp). We examined associations of HDLp size, particle subfractions, and apolipoprotein C‐III content with incident cardiovascular disease (CVD) events across categories of estimated glomerular filtration rate (eGFR).

Methods and Results

Analyses included 6699 participants in MESA (Multi‐Ethnic Study of Atherosclerosis) with measurements of HDLp and 5723 participants with measurements of HDL apolipoprotein C‐III. Cox‐regression methods were used to evaluate associations between HDLp and apolipoproteins with CVD events. Larger HDLp size was associated with lower CVD risk in participants with lower eGFR: hazard ratio (95% CI) per SD higher mean HDL size was 1.00 (0.90–1.11) in eGFR ≥60 mL/min per 1.73 m², 0.65 (0.48–0.86) in eGFR 45 to 59 mL/min per 1.73 m², and 0.48 (0.25–0.93) in eGFR <45 mL/min per 1.73 m² (P for interaction=0.05). Associations of HDLp subfractions with CVD varied significantly by eGFR (P for interaction=0.04), with significant inverse associations between higher concentrations of large HDLp and CVD events across categories of kidney function, but nonsignificant results for small HDLp. Only HDLp without apolipoprotein C‐III was associated with lower risk of CVD events, with seemingly (albeit not statistically significant) stronger associations among participants with lower eGFR (P for interaction=0.19).

Conclusions

HDL particles of larger size and higher concentrations of large HDL and of HDL without apolipoprotein C‐III were associated with lower CVD risk, with risk estimates seemingly stronger among participants with lower eGFR. Future larger studies are needed to corroborate these findings.

Impaired Delivery of Cholesterol Effluxed From Macrophages to Hepatocytes by Serum From CKD Patients May Underlie Increased Cardiovascular Disease Risk

Introduction

Although chronic kidney disease (CKD) is associated with increased risk for coronary artery disease (CAD), the underlying mechanisms are not completely defined. In the present study, we tested the hypothesis that flux of cholesterol from macrophage foam cells to liver is impaired in subjects with CKD.

Methods

Consecutive healthy patients, patients with at least 1 CAD risk factor, patients with established CAD, and patients with CKD stages G3 to G5 (n ≥ 15/group) were recruited prospectively. The ability of total patient serum without any modifications to (i) facilitate efflux of cholesterol from human THP1-macrophage foam cells under physiological conditions (cholesterol efflux capacity [CEC]) and (ii) to deliver this effluxed cholesterol to primary hepatocytes with physiological expression of high-density lipoprotein (HDL) receptor SR-BI (capacity to deliver cholesterol to hepatocytes [CDCH]) was evaluated.

Results

Although healthy patients, patients with at least 1 CAD risk factor, and patients with established CAD all showed similar CEC, patients with CKD showed significantly higher CEC. CDCH was significantly lower in all groups compared with the healthy patients; however, when corrected for higher CEC, CDCH in patients with CKD was significantly lower than in patients with CAD. CDCH correlated with age, body mass index, metabolic parameters, inflammatory markers, and kidney function markers (estimated glomerular filtration rate [eGFR], serum creatinine, and serum cystatin C).

Conclusions

These results suggest that aberrations in delivery of cholesterol effluxed from macrophage foam cells to liver for final elimination or the last step of reverse cholesterol transport, may underlie the increased risk of CAD in patients with CKD.

Association of Serum Paraoxonase/Arylesterase Activity With All-Cause Mortality in Maintenance Hemodialysis Patients

CONTEXT

In end-stage renal disease (ESRD), serum high-density lipoprotein cholesterol (HDL-C) level is not an accurate predictor of mortality, partly because it does not necessarily correlate with indices of HDL function. Paraoxonase (PON) is a major enzyme constituent of HDL and a key component of HDL antioxidant activity. Apolipoprotein A-I (Apo A-1) is the core HDL structural protein that plays a major role in various aspects of HDL function.

OBJECTIVE

We sought to examine PON activity and Apo A-I levels in patients with ESRD vs healthy controls.

DESIGN AND SETTING

PON/arylesterase activity was measured in 499 patients with maintenance hemodialysis (MHD) and 24 healthy controls with similar distributions of age, sex, and race/ethnicity. Serum acrolein-modified Apo A-I was measured in 30 patients with MHD and 10 healthy controls.

MAIN OUTCOME MEASURES

Multilevel Cox models were used to assess associations among PON activity, Apo A-I, and HDL-C levels with 12-month all-cause mortality.

RESULTS

PON activity was significantly lower in patients with MHD vs controls. Furthermore, acrolein-modified Apo A-I levels were higher in patients with MHD vs controls. In fully adjusted models, high PON activity was associated with lower 12-month mortality, whereas no difference of mortality risk was observed across HDL-C levels. The combination of high PON and low Apo A-I compared with low PON and low Apo A-I was associated with lower mortality risk.

CONCLUSIONS

In patients with MHD, PON activity had a stronger association with 12-month mortality than HDL-C. Future studies are needed to examine the role of these markers as potential diagnostic and therapeutic tools in ESRD.

Kidney as modulator and target of "good/bad" HDL

The strong inverse relationship between low levels of high-density lipoproteins (HDLs) and atherosclerotic cardiovascular disease (CVD) led to the designation of HDL as the "good" cholesterol. The atheroprotection is thought to reflect HDL's capacity to efflux cholesterol from macrophages, followed by interaction with other lipoproteins in the plasma, processing by the liver and excretion into bile. However, pharmacologic increases in HDL-C levels have not led to expected clinical benefits, giving rise to the concept of dysfunctional HDL, in which increases in serum HDL-C are not beneficial due to lost or altered HDL functions and transition to "bad" HDL. It is now understood that the cholesterol in HDL, measured by HDL-C, is neither a marker nor the mediator of HDL function, including cholesterol efflux capacity. It is also understood that besides cholesterol efflux, HDL functionality encompasses many other potentially beneficial functions, including antioxidant, anti-inflammatory, antithrombotic, anti-apoptotic, and vascular protective effects that may be critical protective pathways for various cells, including those in the kidney parenchyma. This review highlights advances in our understanding of the role kidneys play in HDL metabolism, including the effects on levels, composition, and functionality of HDL particles, particularly the main HDL protein, apolipoprotein AI (apoAI). We suggest that normal apoAI/HDL in the glomerular filtrate provides beneficial effects, including lymphangiogenesis, that promote resorption of renal interstitial fluid and biological particles. In contrast, dysfunctional apoAI/HDL activates detrimental pathways in tubular epithelial cells and lymphatics that lead to interstitial accumulation of fluid and harmful particles that promote progressive kidney damage.

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.

Differential Expression of Urinary Exosomal MicroRNAs miR-21-5p and miR-30b-5p in Individuals with Diabetic Kidney Disease

Biomarkers for the identification of diabetic kidney disease (DKD) are needed as current tests lack sensitivity for detecting early kidney damage. MicroRNAs (miRNAs) are short, non-coding regulatory ribonucleic acid (RNA) molecules commonly found in urinary exosomes differentially expressed as renal function declines. We evaluated urinary exosomal miRNA expression in persons with type 2 diabetes mellitus and DKD (T2DKD). 87 human urinary exosomal miRNAs were profiled in a discovery cohort of patients with T2DKD (n = 14) and age and gender matched controls with type 2 diabetes mellitus and normal renal function (T2DNRF; n = 15). Independent validation of differentially expressed target miRNAs was performed in a second cohort with T2DKD (n = 22) and two control groups: T2DNRF (n = 15) and controls with chronic kidney disease (CCKD) and poor renal function without diabetes (n = 18). In the discovery cohort, urinary miR-21-5p, let-7e-5p and miR-23b-3p were significantly upregulated in T2DKD compared to T2DNRF (p < 0.05). Conversely, miR-30b-5p and miR-125b-5p expression was significantly lower in T2DKD (p < 0.05). Independent validation confirmed up-regulation of miR-21-5p in the replication cohort in T2DKD (2.13-fold, p = 0.006) and in CCKD (1.73-fold, p = 0.024). In contrast, miR-30b-5p was downregulated in T2DKD (0.82-fold, p = 0.006) and in CCKD (0.66-fold, p < 0.002). This study identified differential expression of miR-21-5p and miR-30b-5p in individuals with diabetic kidney disease and poor renal function. These miRNAs represent potential biomarkers associated with the pathogenesis of renal dysfunction.