APOL1 renal-risk genotypes associate with longer hemodialysis survival in prevalent nondiabetic African American patients with end-stage renal disease

The kidney evaluation of living kidney donor candidates: US practices in 2017

We surveyed US transplant programs to assess practices used to assess kidney health in living kidney donor candidates in 2017; the response rate was 31%. In this report, we focus on the kidney; a companion piece focuses on the metabolic and cardiovascular aspects of candidate evaluation. Compared to 2005, programs have become more stringent in accepting younger candidates and less stringent in accepting older candidates. The 24-hour creatinine clearance remains the mainstay for kidney function assessment, with 74% continuing to use a value below 80 mL/min/1.73 m² for exclusion and 22% using age-based criteria. ApoL1 genotyping is obtained routinely or selectively by 45%, half of which use the high-risk genotype as an absolute exclusion criterion. For history of symptomatic stones, 49% accept if there is no current radiographic evidence of stones and urine profile is low risk, 80%-95% consider candidates with unilateral asymptomatic stones, but only 33%-48% consider if stones are bilateral. In addition, 14% use the risk assessment tool developed by Grams et al routinely for decision-making, and 42% use it sometimes. Also, 57% reported not having yet determined a risk threshold for acceptable postdonation risk above which candidates are excluded. Contemporary practice variation underscores the need for better evidence to guide the donor selection process.

APOL1 Risk Variants and Subclinical Cardiovascular Disease in Incident Hemodialysis Patients

Introduction

To better understand the impact of APOL1 risk variants in end-stage renal disease (ESRD) we evaluated associations of APOL1 risk variants with subclinical cardiovascular disease (CVD) and mortality among African Americans initiating hemodialysis and enrolled in the Predictors of Arrhythmic and Cardiovascular Risk in ESRD cohort study.

Methods

We modeled associations of APOL1 risk status (high = 2; low = 0/1 risk alleles) with baseline subclinical CVD (left ventricular [LV] hypertrophy; LV mass; ejection fraction; coronary artery calcification [CAC]; pulse wave velocity [PWV]) using logistic and linear regression and all-cause or cardiovascular mortality using Cox models, adjusting for age, sex, and ancestry. In sensitivity analyses, we further adjusted for systolic blood pressure and Charlson Comorbidity Index.

Results

Of 267 African American participants successfully genotyped for APOL1, 27% were high-risk carriers, 41% were women, and mean age was 53 years. At baseline, APOL1 high- versus low-risk status was independently associated with 50% and 53% lower odds of LV hypertrophy and CAC, respectively, and 10.7% lower LV mass. These associations were robust to further adjustment for comorbidities but not systolic blood pressure. APOL1 risk status was not associated with all-cause or cardiovascular mortality (mean follow-up 2.5 years).

Conclusion

Among African American patients with incident hemodialysis, APOL1 high-risk status was associated with better subclinical measures of CVD but not mortality.

Kidney Disease-Associated APOL1 Variants Have Dose-Dependent, Dominant Toxic Gain-of-Function

BACKGROUND

Two coding renal risk variants (RRVs) of the APOL1 gene (G1 and G2) are associated with large increases in CKD rates among populations of recent African descent, but the underlying molecular mechanisms are unknown. Mammalian cell culture models are widely used to study cytotoxicity of RRVs, but results have been contradictory. It remains unclear whether cytotoxicity is RRV-dependent or driven solely by variant-independent overexpression. It is also unknown whether expression of the reference APOL1 allele, the wild-type G0, could prevent cytotoxicity of RRVs.

METHODS

We generated tetracycline-inducible APOL1 expression in human embryonic kidney HEK293 cells and examined the effects of increased expression of APOL1 (G0, G1, G2, G0G0, G0G1, or G0G2) on known cytotoxicity phenotypes, including reduced viability, increased swelling, potassium loss, aberrant protein phosphorylation, and dysregulated energy metabolism. Furthermore, whole-genome transcriptome analysis examined deregulated canonical pathways.

RESULTS

At moderate expression, RRVs but not G0 caused cytotoxicity in a dose-dependent manner that coexpression of G0 did not reduce. RRVs also have dominant effects on canonical pathways relevant for the cellular stress response.

CONCLUSIONS

In HEK293 cells, RRVs exhibit a dominant toxic gain-of-function phenotype that worsens with increasing expression. These observations suggest that high steady-state levels of RRVs may underlie cellular injury in APOL1 nephropathy, and that interventions that reduce RRV expression in kidney compartments may mitigate APOL1 nephropathy.

Risk of Cardiovascular Disease and Mortality in Young Adults With End-stage Renal Disease: An Analysis of the US Renal Data System

Importance

Cardiovascular disease (CVD) is a leading cause of death among patients with end-stage renal disease (ESRD). Young adult (ages 22-29 years) have risks for ESRD-associated CVD that may vary from other ages.

Objective

To test the hypothesis that young adult-onset ESRD is associated with higher cardiovascular (CV) hospitalizations and mortality with different characteristics than childhood-onset disease.

Design, Setting, and Participants

This population-based cohort study used the US Renal Data System to categorize patients who initiated ESRD care between 2003 and 2013 by age at ESRD onset (1-11, 12-21, and 22-29 years). Cardiovascular hospitalizations were identified via International Classification of Diseases, Ninth Revision discharge codes and CV mortality from the Centers for Medicare & Medicaid ESRD Death Notification Form. Patients were censored at death from non-CVD events, loss to follow-up, recovery, or survival to December 31, 2014. Adjusted proportional hazard models (95% CI) were fit to determine risk of CV hospitalization and mortality by age group. Data analysis occurred from May 2016 and December 2017.

Exposures

Onset of ESRD.

Main Outcomes and Measures

Cardiovascular mortality and hospitalization.

Results

A total of 33 156 patients aged 1 to 29 years were included in the study population. Young adults (aged 22-29 years) had a 1-year CV hospitalization rate of 138 (95% CI, 121-159) per 1000 patient-years. Young adults had a higher risk for CV hospitalization than children (aged 1-11 years; hazard ratio [HR], 0.41 [95% CI, 0.26-0.64]) and adolescents (aged 12-21 years; HR, 0.86 [95% CI, 0.77-0.97]). Of 4038 deaths in young adults, 1577 (39.1%) were owing to CVD. Five-year cumulative incidence of mortality in this group (7.3%) was higher than in younger patients (adolescents, 4.0%; children, 1.7%). Adjusted HRs for CV mortality were higher for young adults with all causes of ESRD than children (cystic, hereditary, and congenital conditions: HR, 0.22 [95% CI, 0.11-0.46]; P < .001; glomerulonephritis: HR, 0.21 [95% CI, 0.10-0.44]; P < .001; other conditions: HR, 0.33 [95% CI, 0.23-0.49]; P < .001). Adolescents had a lower risk for CV mortality than young adults for all causes of ESRD except glomerulonephritis (cystic, hereditary, and congenital conditions: HR, 0.45 [95% CI, 0.27-0.74]; glomerulonephritis: HR, 0.99 [95% CI, 0.76-1.11]; other: HR, 0.47 [95% CI, 0.40-0.57]). Higher risks for CV hospitalization and mortality were associated with lack of preemptive transplant compared with hemodialysis (hospital: HR, 14.24 [95% CI, 5.92-34.28]; mortality: HR, 13.64 [95% CI, 8.79-21.14]) and peritoneal dialysis [hospital: HR, 8.47 [95% CI, 3.50-20.53]; mortality: HR, 7.86 [95% CI, 4.96-12.45]). Nephrology care before ESRD was associated with lower risk for CV mortality (HR, 0.77 [95% CI, 0.70-0.85]).

Conclusions and Relevance

Cardiovascular disease accounted for nearly 40% of deaths in young adults with incident ESRD in this cohort. Identified risk factors may inform development of age-appropriate ESRD strategies to improve the CV health of this population.

APOL1 Nephropathy Risk Alleles and Mortality in African American Adults: A Cohort Study

RATIONALE & OBJECTIVE

APOL1 nephropathy risk alleles are associated with the development of chronic kidney disease (CKD) in African Americans. Although CKD is an established risk factor for mortality, associations of APOL1 risk alleles with mortality are uncertain.

STUDY DESIGN

Prospective cohort.

SETTINGS & PARTICIPANTS

10,380 African American and 17,485 white American participants in the Reasons for Geographic and Racial Differences in Stroke (REGARDS) Study.

EXPOSURES

APOL1 nephropathy risk alleles.

OUTCOMES

All-cause and cause-specific mortality.

ANALYTICAL APPROACH

Cox proportional hazards models were used to examine the association of APOL1 high-risk genotypes (2 risk alleles) versus APOL1 low-risk genotypes (0/1 risk allele) with all-cause and cause-specific mortality in African Americans and examine the risk for all-cause mortality in African Americans with high-risk genotypes versus African Americans with low-risk genotypes and white Americans.

RESULTS

APOL1 high-risk participants were younger and had a higher prevalence of albuminuria than low-risk participants. There was no statistically significant association of APOL1 high- versus low-risk genotypes with all-cause mortality in models adjusted for sociodemographic variables, comorbid conditions, and kidney function (HR, 0.88; 95% CI, 0.77-1.01). After further adjustment for genetic ancestry in a subset with available data, a statistically significant association emerged (HR, 0.81; 95% CI, 0.69-0.96). Associations differed by CKD status (Pinteraction=0.04), with African Americans with high-risk genotypes having lower risk for mortality than those with low-risk genotypes in fully adjusted models (HR, 0.78; 95% CI, 0.62-0.99) among those with CKD, but not those without CKD (HR, 0.84; 95% CI, 0.66-1.05). Compared with white Americans, African Americans with high-risk genotypes had a similar rate of mortality, whereas African Americans with low-risk genotypes had a higher rate of mortality (HR, 1.07; 95% CI, 1.00-1.14) in fully adjusted models.

LIMITATIONS

Lack of follow-up measures of kidney function.

CONCLUSIONS

African Americans with high-risk APOL1 genotypes had lower mortality than those with low-risk genotypes in multivariable-adjusted models including genetic ancestry.

Hypertensive APOL1 risk allele carriers demonstrate greater blood pressure reduction with angiotensin receptor blockade compared to low risk carriers

Background

Hypertension (HTN) disproportionately affects African Americans (AAs), who respond better to thiazide diuretics than other antihypertensives. Variants of the APOL1 gene found in AAs are associated with a higher rate of kidney disease and play a complex role in cardiovascular disease.

Methods

AA subjects from four HTN trials (n = 961) (GERA1, GERA2, PEAR1, and PEAR2) were evaluated for blood pressure (BP) response based on APOL1 genotype after 4–9 weeks of monotherapy with thiazides, beta blockers, or candesartan. APOL1 G1 and G2 variants were determined by direct sequencing or imputation.

Results

Baseline systolic BP (SBP) and diastolic BP (DBP) levels did not differ based on APOL1 genotype. Subjects with 1–2 APOL1 risk alleles had a greater SBP response to candesartan (-12.2 +/- 1.2 vs -7.5 +/- 1.8 mmHg, p = 0.03; GERA2), and a greater decline in albuminuria with candesartan (-8.3 +/- 3.1 vs +3.7 +/- 4.3 mg/day, p = 0.02). APOL1 genotype did not associate with BP response to thiazides or beta blockers. GWAS was performed to determine associations with BP response to candesartan depending on APOL1 genotype. While no SNPs reached genome wide significance, SNP rs10113352, intronic in CSMD1, predicted greater office SBP response to candesartan (p = 3.7 x 10⁻⁷) in those with 1–2 risk alleles, while SNP rs286856, intronic in DPP6, predicted greater office SBP response (p = 3.2 x 10⁻⁷) in those with 0 risk alleles.

Conclusions

Hypertensive AAs without overt kidney disease who carry 1 or more APOL1 risk variants have a greater BP and albuminuria reduction in response to candesartan therapy. BP response to thiazides or beta blockers did not differ by APOL1 genotype. Future studies confirming this initial finding in an independent cohort are required.

APOL1 Nephropathy Risk Variants and Incident Cardiovascular Disease Events in Community-Dwelling Black Adults

BACKGROUND

APOL1 renal risk variants are strongly associated with chronic kidney disease in Black adults, but reported associations with cardiovascular disease (CVD) have been conflicting.

METHODS

We examined associations of APOL1 with incident coronary heart disease (n=323), ischemic stroke (n=331), and the composite CVD outcome (n=500) in 10 605 Black participants of the REGARDS study (Reasons for Geographic and Racial Differences in Stroke). Primary analyses compared individuals with APOL1 high-risk genotypes to APOL1 low-risk genotypes in Cox proportional hazards models adjusted for CVD risk factors and African ancestry.

RESULTS

APOL1 high-risk participants were younger and more likely to have albuminuria at baseline than APOL1 low-risk participants. The risk of incident stroke, coronary heart disease, or composite CVD end point did not significantly differ by APOL1 genotype status in multivariable models. The association of APOL1 genotype with incident composite CVD differed by diabetes mellitus status (P_interaction=0.004). In those without diabetes mellitus, APOL1 high-risk genotypes associated with greater risk of incident composite CVD (hazard ratio, 1.67; 95% confidence interval, 1.12-2.47) compared with those with APOL1 low-risk genotypes in multivariable adjusted models. This latter association was driven by ischemic strokes (hazard ratio, 2.32; 95% confidence interval, 1.33-4.07), in particular, those related to small vessel disease (hazard ratio, 5.10; 95% confidence interval, 1.55-16.56). There was no statistically significant association of APOL1 genotypes with incident CVD in subjects with diabetes mellitus. The APOL1 high-risk genotype was associated with higher stroke risk in individuals without but not those with chronic kidney disease in fully adjusted models.

CONCLUSIONS

APOL1 high-risk status is associated with CVD events in community-dwelling Black adults without diabetes mellitus.

Survival Advantage of African American Dialysis Patients with End-Stage Renal Disease Causes Related to APOL1

BACKGROUND

Observational studies show that African American (AA) dialysis patients have longer survival than European Americans. We hypothesized that apolipoprotein L1 (APOL1) genetic variation, associated with nephropathy in AAs, contributes to the survival advantage in AA dialysis patients.

METHODS

We examined the association between race and mortality among 37,097 adult dialysis patients, including 54% AAs and 46% European Americans from a large dialysis organization (entry period from July 2001 to June 2006, follow-up through June 2007), within each cause of end-stage renal disease (ESRD) category associated with APOL1 renal risk variants using Cox proportional hazard models.

RESULTS

AA dialysis patients had numerically lower mortality than their European American counterparts for all causes of ESRD. The mortality reduction among AAs compared to European Americans was statistically significant in patients with ESRD attributed to diabetes mellitus, hypertension, and APOL1-enriched glomerulonephritis (GN) (HR [95% CI]: 0.69 [0.66-0.72], 0.73 [0.68-0.79], and 0.89 [0.79-0.99], respectively); these are conditions in which APOL1 variants promote kidney disease. By contrast, the significant survival advantage of AA dialysis patients was not observed in patients with ESRD attributed to other kidney disease (including polycystic kidney disease, interstitial nephritis, and pyelonephritis) and other GN, which are not associated with APOL1 variants.

CONCLUSIONS

These data suggest the hypothesis that the relative survival advantage of AA dialysis patients may be related to APOL1 variation. Further large population-based genetic studies are required to test this hypothesis.

Genetics, Genomics, and Precision Medicine in End-Stage Kidney Disease

Recent advances in genetics of renal disease have deepened our understanding of progressive kidney disease. Here, we review genetic variants that are of particular importance to progressive glomerular disease that result in end-stage kidney disease (ESKD). Some of the most striking findings relate to APOL1 genetic variants, seen exclusively in individuals of sub-Saharan African descent, that create a predisposition to particular renal disorders, including focal segmental glomerulosclerosis and arterionephrosclerosis. We also review the genetics of cardiovascular disease in ESKD and note that little work has been published on the genetics of other ESKD complications, including anemia, bone disease, and infections. Deeper understanding of the genetics of ESKD and its complications may lead to new therapies that are tailored to an individual patient's genetic profile or are discovered based on genetic approaches that identify novel pathways of renal cell injury and repair.

Biomarkers in Solid Organ Transplantation

After more than 6 decades of clinical practice, the transplant community continues to research noninvasive biomarkers of solid organ injury to help improve patient care. In this review, we discuss the clinical usefulness of selective biomarkers and how they are processed at the laboratory. In addition, we organize these biomarkers based on specific aims and introduce innovative markers currently under investigation.

APOL1 risk variants and kidney disease: what we know so far

There are striking differences in chronic kidney disease between Caucasians and African descendants. It was widely accepted that this occurred due to socioeconomic factors, but recent studies show that apolipoprotein L-1 (APOL1) gene variants are strongly associated with focal segmental glomerulosclerosis, HIV-associated nephropathy, hypertensive nephrosclerosis, and lupus nephritis in the African American population. These variants made their way to South America trough intercontinental slave traffic and conferred an evolutionary advantage to the carries by protecting against forms of trypanosomiasis, but at the expense of an increased risk of kidney disease. The effect of the variants does not seem to be related to their serum concentration, but rather to local action on the podocytes. Risk variants are also important in renal transplantation, since grafts from donors with risk variants present worse survival.

APOL1 Nephropathy: A Population Genetics and Evolutionary Medicine Detective Story

Common DNA sequence variants rarely have a high-risk association with a common disease. When such associations do occur, evolutionary forces must be sought, such as in the association of apolipoprotein L1 (APOL1) gene risk variants with nondiabetic kidney diseases in populations of African ancestry. The variants originated in West Africa and provided pathogenic resistance in the heterozygous state that led to high allele frequencies owing to an adaptive evolutionary selective sweep. However, the homozygous state is disadvantageous and is associated with a markedly increased risk of a spectrum of kidney diseases encompassing hypertension-attributed kidney disease, focal segmental glomerulosclerosis, human immunodeficiency virus nephropathy, sickle cell nephropathy, and progressive lupus nephritis. This scientific success story emerged with the help of the tools developed over the past 2 decades in human genome sequencing and population genomic databases. In this introductory article to a timely issue dedicated to illuminating progress in this area, we describe this unique population genetics and evolutionary medicine detective story. We emphasize the paradox of the inheritance mode, the missing heritability, and unresolved associations, including cardiovascular risk and diabetic nephropathy. We also highlight how genetic epidemiology elucidates mechanisms and how the principles of evolution can be used to unravel conserved pathways affected by APOL1 that may lead to novel therapies. The APOL1 gene provides a compelling example of a common variant association with common forms of nondiabetic kidney disease occurring in a continental population isolate with subsequent global admixture. Scientific collaboration using multiple experimental model systems and approaches should further clarify pathomechanisms further, leading to novel therapies.

The Expanding Role of APOL1 Risk in Chronic Kidney Disease and Cardiovascular Disease

Variants of the APOL1 gene, found primarily in individuals of African descent, are associated with various forms of kidney disease and kidney disease progression. Recent studies evaluating the association of APOL1 with cardiovascular disease have yielded conflicting results, and the potential role in cardiovascular disease remains unclear. In this review, we summarize the observational studies linking the APOL1 risk variants with chronic kidney and cardiovascular disease among persons of African descent.

APOL1 nephropathy risk variants do not associate with subclinical atherosclerosis or left ventricular mass in middle-aged black adults

Prior studies reported associations of APOL1 nephropathy risk variants with subclinical atherosclerosis. However, these findings were limited to older individuals with high comorbidities. To evaluate this in younger individuals, we calculated associations of APOL1 risk variants (high risk [2 risk variants] vs. low risk [0-1 risk variant]) with prevalent, incident, or progressive coronary artery calcification, a carotid intima media thickness over the 90th percentile, and left ventricular hypertrophy in 1315 black participants of the Coronary Artery Risk Development in Young Adults (CARDIA) study. The mean age of this cohort was 44.6 years and their mean estimated glomerular filtration rate was 102.5 ml/min/1.73m2. High-risk participants were found to be younger and have a higher prevalence of albuminuria than low-risk participants. In Poisson regression models adjusted for comorbidities and kidney function, the risk of prevalent coronary artery calcification (relative risk [95% confidence interval] 1.12 [0.72,1.71]), the incident coronary artery calcification (1.50 [0.87,2.59]), and the progression of coronary artery calcification (1.40 [0.88,2.23]) did not significantly differ in high vs. low-risk participants. Furthermore, the risk of carotid intima media thickness over the 90th percentile (1.28 [0.78,2.10]) and left ventricular hypertrophy (1.02[0.73,1.43]) did not significantly differ in high vs. low-risk participants in fully-adjusted models. Thus, APOL1 risk variants did not associate with subclinical markers of atherosclerosis or left ventricular hypertrophy in middle-aged black adults with preserved kidney function.

APOL1 Genotype and Renal Function of Black Living Donors

Black living kidney donors are at higher risk of developing kidney disease than white donors. We examined the effect of the APOL1 high-risk genotype on postdonation renal function in black living kidney donors and evaluated whether this genotype alters the association between donation and donor outcome. We grouped 136 black living kidney donors as APOL1 high-risk (two risk alleles; n=19; 14%) or low-risk (one or zero risk alleles; n=117; 86%) genotype. Predonation characteristics were similar between groups, except for lower mean±SD baseline eGFR (CKD-EPI equation) in donors with the APOL1 high-risk genotype (98±17 versus 108±20 ml/min per 1.73 m²; P=0.04). At a median of 12 years after donation, donors with the APOL1 high-risk genotype had lower eGFR (57±18 versus 67±15 ml/min per 1.73 m²; P=0.02) and faster decline in eGFR after adjusting for predonation eGFR (1.19; 95% confidence interval, 0 to 2.3 versus 0.4; 95% confidence interval, 0.1 to 0.7 ml/min per 1.73 m² per year, P=0.02). Two donors developed ESRD; both carried the APOL1 high-risk genotype. In a subgroup of 115 donors matched to 115 nondonors by APOL1 genotype, we did not find a difference between groups in the rate of eGFR decline (P=0.39) or any statistical interaction by APOL1 status (P=0.92). In conclusion, APOL1 high-risk genotype in black living kidney donors associated with greater decline in postdonation kidney function. Trajectory of renal function was similar between donors and nondonors. The association between APOL1 high-risk genotype and poor renal outcomes in kidney donors requires validation in a larger study.

APOL1 risk variants and death among African American hemodialysis patients: survival of the fittest?

Recent studies have focused on associations of the APOL1 risk variants with outcomes beyond kidney disease, including cardiovascular disease and mortality. Ma and colleagues now expand on this growing but contradicting body of work. Their analysis of a prevalent cohort of African American hemodialysis patients shows that the risk variants are associated with a survival benefit among nondiabetics. Whether this simply reflects a healthier status at hemodialysis initiation among those carrying 2 risk variants or whether these variants truly confer a survival advantage is unclear.

APOL1 Gene Kidney Risk Variants and Cardiovascular Disease: Getting to the Heart of the Matter

Apolipoprotein L1 gene (APOL1) renal risk variants exhibit strong genetic associations with a spectrum of nondiabetic kidney diseases in individuals with recent African ancestry. Relationships between APOL1 kidney risk variants and cardiovascular disease (CVD) susceptibility and CVD-related death remain controversial. Some studies detected an increased risk for CVD, whereas others support protection from death and subclinical CVD and cerebrovascular disease. Because treatments for nondiabetic kidney disease may target this gene and its protein products, it remains critical to clarify the potential extrarenal effects of APOL1 kidney risk variants. This review addresses the current literature on APOL1 associations with CVD, cerebrovascular disease, and death. Potential causes of disparate results between studies are discussed.

APOL1 Risk Variants and Cardiovascular Disease: Results From the AASK (African American Study of Kidney Disease and Hypertension)

OBJECTIVE

Among African Americans, the apolipoprotein L1 (APOL1) risk variants have been associated with various types of kidney disease and chronic kidney disease progression. We aimed to determine whether these same risk variants also confer an increased risk for cardiovascular disease.

APPROACH AND RESULTS

In a cohort of African Americans with hypertension-attributed chronic kidney disease followed for up to 12 years, we used Cox proportional hazards models to estimate the relative hazard of a composite cardiovascular disease outcome (cardiovascular death or hospitalization for myocardial infarction, cardiac revascularization procedure, heart failure, or stroke) for the APOL1 high- (2 risk variants) versus low-risk (0-1 risk variant) genotypes. We adjusted for age, sex, ancestry, smoking, heart disease history, body mass index, cholesterol, randomized treatment groups, and baseline and longitudinal estimated glomerular filtration rate, systolic blood pressure, and proteinuria. Among 693 participants with APOL1 genotyping available (23% high risk), the high-risk group had lower mean estimated glomerular filtration rate (44.7 versus 50.1 mL/min per 1.73 m²) and greater proteinuria (median 0.19 versus 0.06) compared with the low-risk group at baseline. There was no significant association between APOL1 genotypes and the composite cardiovascular disease outcome in both unadjusted (hazard ratio=1.23; 95% confidence interval: 0.83-1.81) and fully adjusted (hazard ratio=1.16; 95% confidence interval: 0.77-1.76) models; however, in using an additive model, APOL1 high-risk variants were associated with increased cardiovascular mortality.

CONCLUSIONS

Among African Americans with hypertension-attributed chronic kidney disease, APOL1 risk variants were not associated with an overall risk for cardiovascular disease although some signals for cardiovascular mortality were noted.

APOL1 renal-risk variants do not associate with incident cardiovascular disease or mortality in the Systolic Blood Pressure Intervention Trial

Introduction

Relationships between apolipoprotein L1 gene (APOL1) renal-risk variants (RRVs) and cardiovascular disease (CVD) remain controversial. To clarify associations between APOL1 and CVD, a total of 2568 African American Systolic Blood Pressure Intervention Trial (SPRINT) participants were assessed for the incidence of CVD events (primary composite including nonfatal myocardial infarction, acute coronary syndrome not resulting in myocardial infarction, nonfatal stroke, nonfatal acute decompensated heart failure, and CVD death), renal outcomes, and all-cause mortality.

Methods

Cox proportional hazards regression models were used, adjusting for age, sex, African ancestry proportion, and treatment group (systolic blood pressure target of <120 mm Hg vs. <140 mm Hg).

Results

Of the participants, 14% had 2 APOL1 RRVs; these individuals also had lower baseline estimated GFR and higher levels of albuminuria and BMI. After a median follow-up of 39 months, no significant association was observed between APOL1 RRVs and the primary composite CVD outcome, any of its components, or all-cause mortality (recessive or additive genetic models). APOL1 demonstrated a trend toward association with sustained 30% reduction in estimated GFR to <60 ml/min/1.73 m² in those with normal kidney function at baseline (hazard ratio 1.64; 95% confidence interval = 0.85−2.93; P = 0.114, recessive model).

Discussion

APOL1 RRVs were not associated with incident CVD in high-risk hypertensive, nondiabetic African American participants in SPRINT.

Strict blood pressure control associates with decreased mortality risk by APOL1 genotype

Although APOL1 high-risk genotype partially accounts for the increased susceptibility of blacks to chronic kidney disease (CKD), whether APOL1 associates differentially with mortality risk remains controversial. Here we evaluate the association between APOL1 genotype and risk of death and determine whether APOL1 status modifies the association between strict versus usual blood pressure control and mortality risk. We performed a retrospective analysis of the African American Study of Kidney Disease and Hypertension trial that randomized black participants with CKD to strict versus usual blood pressure control from 1995 to 2001. This included 682 participants with known APOL1 genotype (157 with high-risk genotype) previously assigned to either strict (mean arterial pressure [MAP] 92 mm Hg or less) versus usual blood pressure control (MAP 102-107 mm Hg) during the trial. During a median follow-up of 14.5 years, risk of death did not differ between individuals with high- versus low-risk APOL1 genotypes (unadjusted hazard ratio 1.00 [95% confidence interval 0.76-1.33]). However, a significant interaction was detected between the APOL1 risk group and blood pressure control strategy. In the APOL1 high-risk group, the risk of death was 42% lower comparing strict versus usual blood pressure control (0.58 [0.35-0.97]). In the APOL1 low-risk group, the risk of death comparing strict versus usual blood pressure control was not significantly different (1.09 [0.84-1.43]). Thus, strict blood pressure control during CKD associates with a lower risk of death in blacks with the high-risk CKD APOL1 genotype. Knowledge of APOL1 status could inform selection of blood pressure treatment targets in black CKD patients.