High-Density Lipoprotein Cholesterol Concentration and Acute Kidney Injury After Cardiac Surgery

Impact of remnant cholesterol on short-term and long-term prognosis in patients with prediabetes or diabetes undergoing coronary artery bypass grafting: a large-scale cohort study

BACKGROUND

Remnant cholesterol (remnant-C) contributes to atherosclerotic cardiovascular disease (ASCVD), particularly in individuals with impaired glucose metabolism. Patients with impaired glucose metabolism and ASCVD remain at significant residual risk after coronary artery bypass grafting (CABG). However, the role of remnant-C in this population has not yet been investigated.

METHODS

Adult patients with prediabetes or diabetes undergoing isolated CABG were consecutively enrolled in a longitudinal cohort between 2013 and 2018. The impact of remnant-C on short-term and long-term outcomes after CABG was evaluated. The short-term outcomes included major perioperative complications. The long-term outcomes were major adverse cardiovascular and cerebrovascular events (MACCEs). Remnant-C was analyzed as both a categorical and continuous variable. Logistic regression, Cox regression, and restricted cubic spline analyses were performed with multivariate adjustments.

RESULTS

In terms of perioperative outcomes, patients with elevated remnant-C had a higher incidence of acute kidney injury (AKI) stage 2/3 (high vs. low remnant-C: 3.2% vs. 2.4%; OR: 1.404, 95% CI 1.080-1.824). Each 1-standard deviation (SD) increase in remnant-C was associated with a 16.6% higher risk of AKI stage 2/3 (OR: 1.160, 95% CI 1.067-1.260). Long-term outcomes were assessed after a median follow-up of 3.2 years, during which 1,251 patients (9.3%) experienced MACCEs. Each 1-SD increase in remnant-C was associated with a 6.6% higher risk of MACCEs (HR: 1.066, 95% CI 1.012-1.124), a 7.1% higher risk of all-cause death (HR: 1.071, 95% CI 1.008-1.209), and an 11.2% higher risk of myocardial infarction (HR: 1.112, 95% CI 1.011-1.222). These associations remained consistent when remnant-C was treated as a categorical variable. Importantly, the association between remnant-C and MACCEs was independent of LDL-C levels; higher remnant-C levels were associated with increased MACCE risk regardless of whether LDL-C was ≤ 2.6 mmol/L or > 2.6 mmol/L. Subgroup analysis indicated that this risk was more pronounced in insulin-treated patients.

CONCLUSIONS

Remnant-C is associated with AKI and MACCEs in patients with diabetes or prediabetes undergoing CABG. The MACCE risk associated with remnant-C is independent of LDL-C and is more pronounced in insulin-treated patients.

High-Density Lipoprotein Anti-Inflammatory Capacity and Acute Kidney Injury After Cardiac and Vascular Surgery: A Prospective Observational Study

OBJECTIVES

Acute kidney injury (AKI) predicts death after cardiac and vascular surgery. Higher preoperative high-density lipoprotein (HDL) concentrations are associated with less postoperative AKI. In animals, HDL's anti-inflammatory capacity to suppress endothelial cell adhesion molecule expression reduces kidney damage due to ischemia and hemorrhagic shock. The objective of this study is to evaluate the statistical relationship between HDL anti-inflammatory capacity and AKI after major cardiac and vascular surgery.

DESIGN

Prospective observational study.

SETTING

Quaternary medical center.

PATIENTS

One hundred adults with chronic kidney disease on long-term statin therapy undergoing major elective cardiac and vascular surgery.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

Apolipoprotein B-depleted serum collected at anesthetic induction was incubated with tumor necrosis factor alpha stimulated human endothelial cells. Reverse transcriptase-polymerase chain reaction was used to measure intercellular adhesion molecule-1 (ICAM-1) messenger RNA. Enzyme-linked immunosorbent assay assays were used to measure apolipoprotein A-I and postoperative soluble ICAM-1 concentrations in patient plasma. HDL concentration did not correlate with HDL ICAM-1 suppression capacity (Spearman R = 0.05; p = 0.64). Twelve patients (12%) were found to have dysfunctional, pro-inflammatory HDL. Patients with pro-inflammatory HDL had a higher rate of postoperative AKI than patients with anti-inflammatory HDL ( p = 0.046). After adjustment for AKI risk factors, a higher preoperative HDL capacity to suppress endothelial ICAM-1 was independently associated with lower odds of AKI (odds ratio, 0.88; 95% CI, 0.80-0.98; p = 0.016). The association between HDL anti-inflammatory capacity and postoperative AKI was independent of HDL concentration ( p = 0.018). Further, a higher long-term statin dose was associated with higher HDL capacity to suppress endothelial ICAM-1 ( p = 0.045).

CONCLUSIONS

Patients with chronic kidney disease undergoing cardiac and vascular surgery who have dysfunctional, pro-inflammatory HDL have a higher risk of postoperative AKI compared with patients with anti-inflammatory HDL. Conversely, a higher HDL anti-inflammatory capacity is associated with a lower risk of postoperative AKI, independent of HDL concentration. Higher long-term statin dose is associated with higher HDL anti-inflammatory capacity.

Association between inflammatory biomarkers and postoperative acute kidney injury after cardiac surgery in patients with preoperative renal dysfunction: a retrospective pilot analysis

BACKGROUND

Acute kidney injury (AKI) represents a significant post-cardiac surgery complication, particularly prevalent among individuals with pre-existing renal dysfunction. Chronic kidney disease (CKD) is frequently accompanied by persistent, low-grade inflammation, which is known to exacerbate systemic stress responses during surgical procedures. This study hypothesizes that these inflammatory responses might influence the incidence and severity of postoperative acute kidney injury (AKI), potentially serving as a protective mechanism by preconditioning the kidney to stress.

METHODS

This retrospective study enrolled patients with preoperative renal dysfunction (eGFR between 15 and 60 ml/min/1.73 m²) who underwent cardiac surgery between January 2020 and December 2022. Preoperative inflammatory biomarkers were evaluated. The primary outcome was the incidence of postoperative AKI, as defined by the Kidney Disease: Improving Global Outcomes (KDIGO) criteria. Multivariate regression models and sensitivity analyses were conducted to ascertain the relationship between inflammatory biomarkers and AKI. Restricted cubic spines (RCS) was conducted to explore nonlinear associations between inflammatory biomarkers and AKI.

RESULTS

AKI occurred in 53.4% (392/734) of patients, accompanied by significant mortality and length of hospital stay increases in cases of AKI (P < 0.005). After full adjustment of confounders, neutrophil percentage-to-albumin ratio (OR = 0.28), systemic inflammation response index (OR = 0.70), systemic immune inflammation index (OR = 0.69), neutrophil-to-lymphocyte ratio (OR = 0.70), monocyte/high-density lipoprotein cholesterol ratio (OR = 0.53), neutrophil/high-density lipoprotein cholesterol ratio (OR = 0.43) demonstrated an inverse association with AKI. Sensitivity analyses revealed that patients in the highest quartile of these biomarkers exhibited a significantly lower prevalence of AKI compared to those in the lowest quartile (p for trend < 0.05). The RCS analysis suggested an "Inverted U-shaped" association of both LnNPAR and LnSIRI with AKI.

CONCLUSIONS

This study identified an inverse association between preoperative inflammatory biomarkers and postoperative AKI in patients with preoperative renal dysfunction. The findings implied that preoperative inflammation may play a protective role against postoperative AKI in this patient population undergoing cardiac surgery.

Prognostic significance of preoperative nutritional status for postoperative acute kidney injury in older patients undergoing major abdominal surgery: a retrospective cohort study

BACKGROUND

The association between malnutrition and postoperative acute kidney injury (AKI) has not been well studied. In this study, the authors examined the association between preoperative nutritional status and postoperative AKI in older patients who underwent major abdominal surgery, as well as the predictive value of malnutrition for AKI.

MATERIALS AND METHODS

The authors retrospectively included patients aged 65 or older who underwent major elective abdominal surgery. The nutritional status of the patient was evaluated using three objective nutritional indices, such as the geriatric nutritional risk index (GNRI), the prognostic nutritional index (PNI), and the controlling nutritional status (CONUT). AKI was determined using the KDIGO criteria. The authors performed logistic regression analysis to investigate the association between preoperative nutritional status and postoperative AKI, as well as the predictive value of nutritional scores for postoperative AKI.

RESULTS

A total of 2775 patients were included in the study, of which 707 (25.5%), 291 (10.5%), and 517 (18.6%) had moderate to severe malnutrition according to GNRI, PNI, and CONUT calculations. After surgery, 144 (5.2%) patients developed AKI, 86.1% at stage 1, 11.1% at stage 2, and 2.8% at stage 3 as determined by KDIGO criteria. After adjustment for traditional risk factors, worse nutritional scores were associated with a higher AKI risk. In addition to traditional risk factors, these nutritional indices improved the predictive ability of AKI prediction models, as demonstrated by significant improvements in integrated discrimination and net reclassification.

CONCLUSIONS

Poor preoperative nutritional status, as assessed by GNRI, PNI, and CONUT scores, was associated with an increased risk of postoperative AKI. Incorporating these scores into AKI prediction models improved their performance. These findings emphasize the need for screening surgical patients for malnutrition risk. Further research is needed to determine whether preoperative malnutrition assessment and intervention can reduce postoperative AKI incidence.

Association of Malnutrition with Risk of Acute Kidney Injury: A Systematic Review and Meta-Analysis

Background

Acute kidney injury (AKI) is a complex clinical syndrome of hospitalization that may be affected by undernutrition and metabolic changes. The aim of this meta-analysis was to systematically assess the association between malnutrition and the risk of prevalent AKI.

Materials and Methods

We searched PubMed, Embase, Ovid MEDLINE, Web of Science, and Chinese databases (WANFANG, VIP, and CKI) from database inception until May 1, 2023, for studies evaluating the association of malnutrition with the risk of AKI. Summary odds ratios (ORs) were estimated using a random-effects model.

Results

We identified 17 observational studies, which included 273,315 individuals. Compared with patients with normal nutritional status, those with malnutrition had a 125% increased risk of prevalent AKI (pooled ORs, 2.25; 95% confidence interval, 1.80-2.82). Malnutrition was also significantly associated with prevalent AKI across all subgroups when subgroup analyses were performed on covariates such as region, study design, age, sample size, malnutrition assessment method, patient characteristics, covariate adjustment degree, and risk of bias. Meta-regression models demonstrated no significant differences in AKI risk between patients with malnutrition and without malnutrition.

Conclusions

Our results suggest that malnutrition may be a potential target for AKI prevention. However, well-designed studies with ethnically or geographically diverse populations are needed to evaluate strategies and interventions to prevent or slow the development and progression of AKI in malnourished individuals.

Effect of body mass index on clinical outcomes after robotic cardiac surgery: is there an obesity paradox?

BACKGROUND

To investigate the effect of body mass index (BMI) on clinical outcomes after robotic cardiac surgery, and to explore the postoperative obesity paradox.

METHODS

The data of 146 patients who underwent robotic cardiac surgery under cardiopulmonary bypass (CPB) from July 2016 to June 2022 in Daping Hospital of Army Medical University were retrospectively analyzed, and their demographic data and related clinical data were statistically analyzed. The mean age was (42.88 ± 13.01) years, 55 (37.67%) were male and 91 (62.33%) were female. Patients were divided into 3 groups according to preoperative BMI: lean group (BMI < 18.5 kg/m²; n = 17; 11.64%), normal group (BMI 18.5 kg/m² to 23.9 kg/m²; n = 81; 55.48%), and overweight and obese group (BMI ≥ 24 kg/m²; n = 48; 32.88%). Multivariate analysis was performed to compare clinical outcomes across BMI groups.

RESULTS

Preoperative data in different BMI groups showed that there were statistically significant differences in age, height, weight, body surface area (BSA), diabetes, left atrial anteroposterior diameter (LAD), triglyceride (TG), and high-density lipoprotein (HDL) (all P < 0.05). Postoperative clinical outcomes showed that there was no statistical difference between the lean group and the normal group; the intensive care unit stay and postoperative hospital stay in the overweight and obese group were significantly higher than those in the normal group (P < 0.05), and the risk of postoperative cardiac surgery-related acute kidney injury (CSA-AKI) was significantly increased (P = 0.021); further Multiple Binary Logistic Regression Analysis suggested that preoperative TG (OR = 1.772, 95% CI 1.068-2.942, P = 0.027) and operation time ≥ 300 min (OR = 3.823, 95% CI 1.098-13.308, P = 0.035) were independent risk factors for postoperative CSA-AKI.

CONCLUSIONS

Overweight and obese patients had significantly prolonged intensive care unit stay and postoperative hospital stay after robotic cardiac surgery, and significantly increased incidence of postoperative CSA-AKI, which did not support the obesity paradox; preoperative TG and operation time ≥ 300 min were independent risk factors for postoperative CSA-AKI.

Effect of lipid-lowering medications in patients with coronary artery bypass grafting surgery outcomes

BACKGROUND

Increased life expectancy and improved medical technology allow increasing numbers of elderly patients to undergo cardiac surgery. Elderly patients may be at greater risk of postoperative morbidity and mortality. Complications can lead to worsened quality of life, shortened life expectancy and higher healthcare costs. Reducing perioperative complications, especially severe adverse events, is key to improving outcomes in patients undergoing cardiac surgery. The objective of this study is to determine whether perioperative lipid-lowering medication use is associated with a reduced risk of complications and mortality after coronary artery bypass grafting (CABG) with cardiopulmonary bypass (CPB).

METHODS

After IRB approval, we reviewed charts of 9,518 patients who underwent cardiac surgery with CPB at three medical centers between July 2001 and June 2015. The relationship between perioperative lipid-lowering treatment and postoperative outcome was investigated. 3,988 patients who underwent CABG met inclusion criteria and were analyzed. Patients were divided into lipid-lowering or non-lipid-lowering treatment groups.

RESULTS

A total of 3,988 patients were included in the final analysis. Compared to the patients without lipid-lowering medications, the patients with lipid-lowering medications had lower postoperative neurologic complications and overall mortality (P < 0.05). Propensity weighted risk-adjustment showed that lipid-lowering medication reduced in-hospital total complications (odds ratio (OR) = 0.856; 95% CI 0.781-0.938; P < 0.001); all neurologic complications (OR = 0.572; 95% CI 0.441-0.739; P < 0.001) including stroke (OR = 0.481; 95% CI 0.349-0.654; P < 0.001); in-hospital mortality (OR = 0.616; 95% CI 0.432-0.869; P = 0.006; P < 0.001); and overall mortality (OR = 0.723; 95% CI 0.634-0.824; P < 0.001). In addition, the results indicated postoperative lipid-lowering medication use was associated with improved long-term survival in this patient population.

CONCLUSIONS

Perioperative lipid-lowering medication use was associated with significantly reduced postoperative adverse events and improved overall outcome in elderly patients undergoing CABG surgery with CPB.

Prediction of acute kidney injury after cardiac surgery: model development using a Chinese electronic health record dataset

Background

Acute kidney injury (AKI) is a major complication following cardiac surgery that substantially increases morbidity and mortality. Current diagnostic guidelines based on elevated serum creatinine and/or the presence of oliguria potentially delay its diagnosis. We presented a series of models for predicting AKI after cardiac surgery based on electronic health record data.

Methods

We enrolled 1457 adult patients who underwent cardiac surgery at Nanjing First Hospital from January 2017 to June 2019. 193 clinical features, including demographic characteristics, comorbidities and hospital evaluation, laboratory test, medication, and surgical information, were available for each patient. The number of important variables was determined using the sliding windows sequential forward feature selection technique (SWSFS). The following model development methods were introduced: extreme gradient boosting (XGBoost), random forest (RF), deep forest (DF), and logistic regression. Model performance was accessed using the area under the receiver operating characteristic curve (AUROC). We additionally applied SHapley Additive exPlanation (SHAP) values to explain the RF model. AKI was defined according to Kidney Disease Improving Global Outcomes guidelines.

Results

In the discovery set, SWSFS identified 16 important variables. The top 5 variables in the RF importance matrix plot were central venous pressure, intraoperative urine output, hemoglobin, serum potassium, and lactic dehydrogenase. In the validation set, the DF model exhibited the highest AUROC (0.881, 95% confidence interval [CI] 0.831–0.930), followed by RF (0.872, 95% CI 0.820–0.923) and XGBoost (0.857, 95% CI 0.802–0.912). A nomogram model was constructed based on intraoperative longitudinal features, achieving an AUROC of 0.824 (95% CI 0.763–0.885) in the validation set. The SHAP values successfully illustrated the positive or negative contribution of the 16 variables attributed to the output of the RF model and the individual variable’s effect on model prediction.

Conclusions

Our study identified 16 important predictors and provided a series of prediction models to enhance risk stratification of AKI after cardiac surgery. These novel predictors might aid in choosing proper preventive and therapeutic strategies in the perioperative management of AKI patients.

Contrast-Associated Acute Kidney Injury: Advances and Challenges

A decrease in renal function that follows intravascular administration of contrast medium (CM) within a few days is reported as contrast-induced acute kidney injury (CI-AKI). In clinical practice, the imaging procedure is frequently deferred when clinicians consider that the renal risks caused by CM outweigh the benefits of enhanced imaging. However, with an in-depth understanding of AKI and contrast medium, scholars have realized that the decrease in renal function after CM is caused by contrast medium factors and noncontrast medium factors (such as anemia and hemodynamic instability). Therefore, acute kidney injury caused by CM has been overestimated in the past. The term “contrast-associated acute kidney injury (CA-AKI)” has been increasingly used to indicate AKI after intravascular administration of contrast medium compared with CI-AKI. CA-AKI can increase the risk of death and chronic kidney disease. However, its pathophysiological mechanism has not been fully elucidated, and the effectiveness of various preventive and therapeutic measures have been questioned. These present challenges for us. In this article, we will review the diagnostic criteria, epidemiology, risk factors, pathophysiological mechanisms and treatment of CA-AKI to provide optimized imaging procedures in clinical practice.

Increased Phospholipid Transfer Protein Activity Is Associated With Markers of Enhanced Lipopolysaccharide Clearance in Human During Cardiopulmonary Bypass

Introduction: Lipopolysaccharide (LPS) is a component of gram-negative bacteria, known for its ability to trigger inflammation. The main pathway of LPS clearance is the reverse lipopolysaccharide transport (RLT), with phospholipid transfer protein (PLTP) and lipoproteins playing central roles in this process in experimental animal models. To date, the relevance of this pathway has never been studied in humans. Cardiac surgery with cardiopulmonary bypass is known to favor LPS digestive translocation. Our objective was to determine whether pre-operative PLTP activity and triglyceride or cholesterol-rich lipoprotein concentrations were associated to LPS concentrations in patients undergoing cardiac surgery with cardiopulmonary bypass. Methods: A post-hoc analysis was conducted on plasma samples obtained from patients recruited in a randomized controlled trial.Total cholesterol, high density lipoprotein cholesterol (HDLc), low density lipoprotein cholesterol (LDLc), triglyceride and PLTP activity were measured before surgery. LPS concentration was measured by mass spectrometry before surgery, at the end of cardiopulmonary bypass and 24 h after admission to the intensive care unit. Results: High PLTP activity was associated with lower LPS concentration but not with inflammation nor post-operative complications. HDLc, LDLc and total cholesterol were not associated with LPS concentration but were lower in patients developing post-operative adverse events. HDLc was negatively associated with inflammation biomarkers (CRP, PCT). Triglyceride concentrations were positively correlated with LPS concentration, PCT and were higher in patients with post-operative complications. Conclusion: Our study supports the role of PLTP in LPS elimination and the relevance of RLT in human. PLTP activity, and not cholesterol rich lipoproteins pool size seemed to be the limiting factor for RLT. PLTP activity was not directly related to post-operative inflammation and adverse events, suggesting that LPS clearance is not the main driver of inflammation in our patients. However, HDLc was associated with lower inflammation and was associated with favorable outcomes, suggesting that HDL beneficial anti-inflammatory effects could be, at least in part independent of LPS clearance.

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.

Association Between Preoperative Statin Exposure and Acute Kidney Injury in Adult Patients Undergoing Cardiac Surgery

OBJECTIVES

The existing literature has shown conflicting results regarding the association between preoperative statin exposure and the risk of postoperative cardiac surgery-associated acute kidney injury (CSA-AKI).

DESIGN

A single-center retrospective observational study.

SETTING

A single, large, tertiary care center.

PARTICIPANTS

Adult patients undergoing open cardiac surgery between January 1, 2012 and January 1, 2019.

INTERVENTIONS

AKI was defined using the Kidney Disease: Improving Global Outcomes criteria. A multivariate logistic regression analysis and propensity score-matched analysis were used to study the association.

MEASUREMENTS AND MAIN RESULTS

A total of 58,399 patient charts were retrospectively reviewed. The preoperative statin exposure cohort had a lower prevalence of all stages of CSA-AKI (30.7% v 36.3%, p < 0.001) and stage 3 CSA-AKI (0.9% v 2.1%, p < 0.001). After adjusting for confounding factors, preoperative statin exposure was a protective factor against all stages of postoperative CSA-AKI (odds ratio [OR], 0.885, 95% confidence interval [CI], 0.852-0.920, p < 0.001) and stage 3 CSA-AKI in adults (OR, 0.671, 95% CI, 0.567-0.795, p < 0.001). A propensity score-matched analysis showed that the preoperative statin exposure cohort had a lower risk of all stages of postoperative CSA-AKI (30.7% v 35.3%, p < 0.001) and stage 3 CSA-AKI (0.9% v 2.2%, p < 0.001) than the control cohort.

CONCLUSIONS

Preoperative statin exposure was associated with all stages of postoperative CSA-AKI and stage 3 CSA-AKI.

Proteomics reveals urine apolipoprotein A-I as a potential biomarker of acute kidney injury following percutaneous coronary intervention in elderly patients

The aim of the present study was to investigate how changes in the lipid composition are involved in early stages of acute kidney injury (AKI) following percutaneous coronary intervention (PCI-AKI) in elderly patients. A prospective nested case-control study was performed. Alterations in the urine protein accumulation were investigated in patients with and without PCI-AKI using isobaric tags for relative and absolute quantitation (iTRAQ). In addition, differentially expressed proteins (DEPs) related to lipids were confirmed using parallel reaction monitoring (PRM)-based targeted proteomics. From the cohort of elderly patients (>60 years of age), 14 (12.28%) developed AKI within 48 h after PCI. No significant differences were detected between the AKI and control (CON) groups for serum creatinine at 24 h following treatment (P=0.27). Among the DEPs that overlapped in both the AKI-24 h/AKI-Pre (AKI group at 24 h post-PCI vs. pre-PCI) and AKI-24 h/CON-24 h groups (AKI group vs. CON group at 24 h post-PCI), only apolipoprotein A-I (apoA-I) was related to lipids, which displayed a significant upregulation in expression levels. The protein expression levels of apoA-I displayed a 5.98-fold increase at 24 h after PCI from the baseline and a 2.09-fold increase compared with the control group as determined using PRM, which exhibited a similar trend to the iTRAQ results. Using protein-protein interaction analyses, apoA-I was determined to be functionally linked to the complement and coagulation cascades, the renin-angiotensin system and the hypoxia-inducible factor-1 signaling pathway. Using the pathway analysis tool from the Kyoto Encyclopedia of Genes and Genomes, several pathways were identified to be associated with apoA-I, including fat digestion and absorption, vitamin digestion and absorption, as well as the peroxisome proliferator activated receptor signaling pathway. In conclusion, apoA-I may be a promising biomarker for the early diagnosis of PCI-AKI in elderly patients. The role of apoA-I in the pathobiology of PCI-AKI requires further exploration.

High-Density Lipoproteins and Acute Kidney Injury

High-density lipoprotein (HDL) particles, best known for their anti-atherosclerotic effects, also may play a beneficial role during acute renal stress. HDL from healthy human beings also shows anti-inflammatory and anti-oxidant capacities, promotes endothelial function and repair, and serves as a systemic signaling mechanism facilitating rapid interorgan communication during times of physiologic stress. Higher concentrations of HDL are associated with less acute kidney injury after sepsis, cardiac and vascular surgery, and contrast-exposure during percutaneous coronary interventions. A better understanding of the interplay between HDL and the kidney both under homeostatic conditions and under acute physiologic stress could lead to the identification of novel risk factors and therapeutic targets for acute kidney injury prevention and treatment in the future.

Apolipoprotein L1 (APOL1) Coding Variants Are Associated With Creatinine Rise After Cardiac Surgery

OBJECTIVE

Acute kidney injury (AKI) is a complication of cardiac surgery that is considerably more common in African Americans (1.5-fold). Although homozygous status for apolipoprotein L1 (APOL1) risk alleles is associated with chronic kidney disease in individuals of African ancestry, whether these coding variants confer AKI risk is unknown. The present study examined whether APOL1 homozygous risk allele status was associated with AKI in African Americans after cardiac surgery.

DESIGN

Retrospective analysis of a cohort.

SETTING

Single-center university hospital.

PARTICIPANTS

African American patients from the CATHeterization GENetics study cohort who underwent cardiac surgery with cardiopulmonary bypass.

INTERVENTIONS

Genotyping of APOL1 alleles.

MEASUREMENTS AND MAIN RESULTS

Data from 125 African American patients included 12 APOL1 risk (ie, homozygous for risk alleles) patients and 113 APOL1 control (ie, wildtype or heterozygous for risk alleles) patients. The primary outcome to reflect AKI was peak serum creatinine rise after surgery relative to the preoperative creatinine (%ΔCr). The secondary outcome was Kidney Disease: Improving Global Outcomes (KDIGO) AKI criteria. In the primary analysis, peak creatinine rise was higher in risk compared with control patients in both univariate (%ΔCr 69.1 v 29.6%; p = 0.005) and multivariate regression (%ΔCr 88.5 v 43.7%; p = 0.006) analyses. For the secondary outcome, a trend toward KDIGO AKI development was noted in APOL1 risk patients, but this was not statistically significant.

CONCLUSIONS

African American cardiac surgery patients homozygous for APOL1 chronic kidney disease risk variants averaged a more than 2-fold higher postoperative creatinine rise even after adjustment for other risk factors, suggesting these alleles also are independent risk factors for AKI.

High-density lipoprotein cholesterol concentration and acute kidney injury after noncardiac surgery

Background

Abnormal High-density Lipoprotein Cholesterol Concentration is closely related to postoperative acute kidney injury (AKI) after cardiac surgeries. The purpose of this study was to analyze the relationship between High-density Lipoprotein Cholesterol Concentration and acute kidney injury after non-cardiac surgeries.

Method

This was a single-center cohort study for elective non-cardiac non-kidney surgery from January 1, 2012, to December 31, 2017. The endpoint was the occurrence of acute kidney injury (AKI) 7 days postoperatively in the hospital. Preoperative serum High-density Lipoprotein Cholesterol Concentration was examined by multivariate logistic regression models before and after propensity score weighting analysis.

Results

Of the 74,284 surgeries, 4.4% (3159 cases) suffered acute kidney injury. The odds ratio for HDL (0.96–1.14 as reference, < 0.96, 1.14–1.35, > 1.35) was 1.28 (1.14–1.41), P < 0.001; 0.91 (0.80–1.03), P = 0.150; 0.75 (0.64–0.85), P < 0.001, respectively. Using a dichotomized cutoff point for propensity analysis, Preoperative serum HDL <  1.03 mmol/L (> 1.03 as reference) was associated with increased risk of postoperative AKI, with odds ratio 1.40 (1.27 ~ 1.52), P < 0.001 before propensity score weighting, and 1.32 (1.21–1.46), P < 0.001 after propensity score weighting. Sensitivity analysis with other cut values of HDL showed similar results.

Conclusions

Using multivariate regression analyses before and after propensity score weighting, in addition to multiple sensitivity analysis methods, this study found that following non-cardiac surgery, low HDL cholesterol levels were independent risk factors for AKI.

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.

Acute kidney injury in hospitalized patients who underwent percutaneous kidney biopsy for histological diagnosis of their renal disease

BACKGROUND

Performing a kidney biopsy is necessary to accurately diagnose diseases such as glomerulonephritis and tubulointerstitial nephritis, among other such conditions. These conditions predispose patients to chronic kidney disease, as well as acute kidney injury (AKI). Notably, most epidemiological studies describing AKI have not investigated this patient population.

METHODS

Included patients admitted to the nephrology ward of a tertiary hospital who underwent percutaneous kidney biopsy. AKI was diagnosed based on the Kidney Disease: Improving Global Outcomes criteria.

RESULTS

Of the 223 patients investigated, 140 (62.8%) showed AKI. Of these, 91 (65%), 19 (13.6%), and 30 (21.4%) presented with AKI classified as stages 1, 2, and 3, respectively. The primary indication for performing biopsy was nephrotic syndrome or nephrotic proteinuria (73 [52.1%] in the AKI vs. 51 [61.4%] in the non-AKI group, p = 0.048). Focal segmental glomerulosclerosis was the most prevalent primary disease (24 [17.1%] in the AKI vs. 15 [18.0%] in the non-AKI group, p = 0.150). Multivariate analysis of risk factors associated with AKI showed hemoglobin levels (odds ratio [OR] 0.805, 95% confidence interval [CI] 0.681-0.951, p = 0.011), serum high-density lipoprotein cholesterol levels (HDL-c, OR 0.970, 95% CI 0.949-0.992, p = 0.008), and baseline serum creatinine levels (OR 2.703, 95% CI 1.471-4.968, p = 0.001) were significantly associated with AKI.

CONCLUSIONS

We observed a high prevalence of AKI in hospitalized patients who underwent kidney biopsy to investigate their renal disease, particularly glomerulonephritis. Higher levels of hemoglobin and serum HDL-c were associated with a lower risk of AKI.