APOL1 High-risk Genotype Research Articles

Identification of genetic causes for sporadic steroid-resistant nephrotic syndrome in adults

Monogenic forms of Steroid-Resistant Nephrotic Syndrome (SRNS) have been widely characterized, but genetic screening paradigms preferentially address congenital, infantile onset, and familial cases. Our aim was to characterize the distribution of disease-causing gene mutations in adults with sporadic SRNS or focal segmental glomerulosclerosis (FSGS). We selected adult patients with non-syndromic, biopsy-proven FSGS or SRNS in the absence of known family history. Strict clinical criteria included lack of response to glucocorticoids and cyclosporine, and no recurrence after kidney transplantation. Mutations in SRNS genes were detected using a targeted gene panel. Sixteen of 135 tested participants (11.8%) carried pathogenic mutations in monogenic SRNS genes, and 14 others (10.4%) carried two APOL1 high-risk alleles. Autosomal recessive disease was diagnosed in 5 participants, autosomal dominant disease in 9, and X-linked disease in 2. Four participants carried a de novo heterozygous mutation. Among the 16 participants with identified mutations in monogenic SNRS genes, 7 (43.7%) had type IV collagen mutations. Mutations in monogenic SNRS genes were identified primarily in participants with proteinuria onset before 25 years of age, while the age at disease onset was variable in those with APOL1 high-risk genotype. Mean age at diagnosis was lower and renal survival was worse in participants with identified mutations in SNRS genes than in those without mutations. We found a significant rate of pathogenic mutations in adults with SRNS, with Type IV collagen mutations being the most frequent. These findings may have immediate impact on clinical practice.

Donor APOL1 high-risk genotypes are associated with increased risk and inferior prognosis of de novo collapsing glomerulopathy in renal allografts

Collapsing focal segmental glomerulosclerosis (cFSGS) in the native kidney is associated with heavy proteinuria and accelerated renal failure. However, cFSGS in the renal allograft is less well characterized. Here we report clinico-pathologic features and APOL1 donor risk genotypes in 38 patients with de novo post-kidney transplant cFSGS. Recipients were 34% female and 26% African American. Concurrent viral infections and acute vaso-occlusion (including thrombotic microangiopathy, cortical necrosis, atheroembolization, and cardiac arrest with contralateral graft thrombosis) were present in 13% and 29% of recipients, respectively. Notably, 61% of patients had concurrent acute rejection and 47% received grafts from African American donors, of which 53% carried APOL1 high-risk genotypes. These frequencies of acute rejection and grafts from African American donors were significantly higher than in our general transplant population (35% and 16%, respectively). Patients had a median serum creatinine of 5.4 mg/dl, urine protein/creatinine 3.5 g/g, and 18% had nephrotic syndrome. Graft failure occurred in 63% of patients at an average of eighteen months post-index biopsy. By univariate analysis, donor APOL1 high-risk genotypes, post-transplant time, nephrotic syndrome, and chronic histologic changes were associated with inferior graft survival while acute vaso-occlusion was associated with superior graft survival. Donor APOL1 high-risk genotypes independently predicted poor outcome. Compared to native kidney cFSGS, post-transplant cFSGS had more acute vaso-occlusion but less proteinuria. Thus, de novo cFSGS is associated with variable proteinuria and poor prognosis with potential predisposing factors of African American donor, acute rejection, viral infection and acute vaso-occlusion. Additionally, donor APOL1 high-risk genotypes are associated with higher incidence and worse graft survival.

Highlights From the Circulation Family of Journals

Highlights From the <i>Circulation</i> Family of Journals

Diabetes and Trajectories of Estimated Glomerular Filtration Rate: A Prospective Cohort Analysis of the Atherosclerosis Risk in Communities Study.

OBJECTIVETo characterize long-term kidney disease trajectories in persons with and without diabetes in a general population.RESEARCH DESIGN AND METHODSWe classified 15,517 participants in the community-based Atherosclerosis Risk in Communities (ARIC) study by diabetes status at baseline (1987–1989; no diabetes, undiagnosed diabetes, and diagnosed diabetes). We used linear mixed models with random intercepts and slopes to quantify estimated glomerular filtration rate (eGFR) trajectories at four visits over 26 years.RESULTSAdjusted mean eGFR decline over the full study period among participants without diabetes was −1.4 mL/min/1.73 m2/year (95% CI −1.5 to −1.4), with undiagnosed diabetes was −1.8 mL/min/1.73 m2/year (95% CI −2.0 to −1.7) (difference vs. no diabetes, P < 0.001), and with diagnosed diabetes was −2.5 mL/min/1.73 m2/year (95% CI −2.6 to −2.4) (difference vs. no diabetes, P < 0.001). Among participants with diagnosed diabetes, risk factors for steeper eGFR decline included African American race, APOL1 high-risk genotype, systolic blood pressure ≥140 mmHg, insulin use, and higher HbA1c.CONCLUSIONSDiabetes is an important risk factor for kidney function decline. Those with diagnosed diabetes declined almost twice as rapidly as those without diabetes. Among people with diagnosed diabetes, steeper declines were seen in those with modifiable risk factors, including hypertension and glycemic control, suggesting areas for continued targeting in kidney disease prevention.

“Biomarking” the transition from genetic risk to kidney disease

Only some individuals carrying the high-risk APOL1 genotype go on to develop kidney disease phenotypes. In this issue of Kidney International, Nadkarni and colleagues report the associations of several biomarkers with renal outcomes in individuals with high-risk APOL1 genotypes. In the era of precision medicine, these findings should translate into improved longitudinal risk assessment for this high-risk population and might also provide additional insights regarding sites and mechanisms of APOL1 nephropathy.

UBD modifies APOL1-induced kidney disease risk

People of recent African ancestry develop kidney disease at much higher rates than most other groups. Two specific coding variants in the Apolipoprotein-L1 gene APOL1 termed G1 and G2 are the causal drivers of much of this difference in risk, following a recessive pattern of inheritance. However, most individuals with a high-risk APOL1 genotype do not develop overt kidney disease, prompting interest in identifying those factors that interact with APOL1 We performed an admixture mapping study to identify genetic modifiers of APOL1-associated kidney disease. Individuals with two APOL1 risk alleles and focal segmental glomerulosclerosis (FSGS) have significantly increased African ancestry at the UBD (also known as FAT10) locus. UBD is a ubiquitin-like protein modifier that targets proteins for proteasomal degradation. African ancestry at the UBD locus correlates with lower levels of UBD expression. In cell-based experiments, the disease-associated APOL1 alleles (known as G1 and G2) lead to increased abundance of UBD mRNA but to decreased levels of UBD protein. UBD gene expression inversely correlates with G1 and G2 APOL1-mediated cell toxicity, as well as with levels of G1 and G2 APOL1 protein in cells. These studies support a model whereby inflammatory stimuli up-regulate both UBD and APOL1, which interact in a functionally important manner. UBD appears to mitigate APOL1-mediated toxicity by targeting it for destruction. Thus, genetically encoded differences in UBD and UBD expression appear to modify the APOL1-associated kidney phenotype.

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.

Sickle Cell Trait and the Risk of ESRD in Blacks.

Blacks, compared with whites, have an increased risk of progression to end-stage renal disease (ESRD). Emerging evidence suggests that, in addition to APOL1 high-risk genotypes, hemoglobin variants, including sickle cell trait (SCT) and hemoglobin C trait, have a role in kidney disease in blacks. However, the association between these hemoglobin traits and ESRD remains unknown. In a large population-based cohort, the REasons for Geographic and Racial Differences in Stroke (REGARDS) study, we evaluated 9909 self-reported blacks (739 with SCT and 243 with hemoglobin C trait). Incident ESRD occurred in 40 of 739 (5.4%) individuals with SCT, six of 243 (2.5%) individuals with hemoglobin C trait, and 234 of 8927 (2.6%) noncarriers. The incidence rate for ESRD was 8.5 per 1000 person-years for participants with SCT and 4.0 per 1000 person-years for noncarriers. Compared with individuals without SCT, individuals with SCT had a hazard ratio for ESRD of 2.03 (95% confidence interval, 1.44 to 2.84). Hemoglobin C trait did not associate with prevalent CKD or ESRD. The incidence rate for ESRD among participants with APOL1 high-risk genotypes was 6.6 per 1000 person-years, with a hazard ratio for ESRD of 1.77 (95% confidence interval, 1.31 to 2.38) for participants with, compared with those without, APOL1 high-risk genotypes. In this cohort, SCT strongly associated with risk of progression to ESRD in blacks, and this degree of risk for ESRD was similar to that conferred by APOL1 high-risk genotypes. These results may have important public policy implications for genetic counseling of SCT carriers.

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 mmHg or less) versus usual blood pressure control (MAP 102-107 mmHg) 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.

Renal and Cardiovascular Morbidities Associated with APOL1 Status among African-American and Non-African-American Children with Focal Segmental Glomerulosclerosis.

African-American (AA) children with focal segmental glomerulosclerosis (FSGS) have later onset disease that progresses more rapidly than in non-AA children. It is unclear how APOL1 genotypes contribute to kidney disease risk, progression, and cardiovascular morbidity in children. We examined the prevalence of APOL1 genotypes and associated cardiovascular phenotypes among children with FSGS in the Chronic Kidney Disease in Children (CKiD) study; an ongoing multicenter prospective cohort study of children aged 1-16 years with mild to moderate kidney disease. A total of 140 AA children in the CKiD study were genotyped. High risk (HR) APOL1 genotypes were present in 24% of AA children (33/140) and were associated with FSGS, p < 0.001. FSGS was the most common cause of glomerular disease in children with HR APOL1 (89%; 25/28). Of 32 AA children with FSGS, 25 (78%) had HR APOL1. Compared to children with low risk APOL1 and FSGS (comprising 36 non-AA and 7 AA), children with HR APOL1 developed FSGS at a later age, 12.0 (IQR: 9.5, 12.5) vs. 5.5 (2.5, 11.5) years, p = 0.004, had a higher prevalence of uncontrolled hypertension (52 vs. 33%, p = 0.13), left ventricular hypertrophy (LVH) (53 vs. 12%, p < 0.01), C-reactive protein > 3 mg/l (33 vs. 15%, p = 0.12), and obesity (48 vs. 19%, p = 0.01). There were no differences in glomerular filtration rate, hemoglobin, iPTH, or calcium-phosphate product. AA children with HR APOL1 genotype and FSGS have increase prevalence of obesity and LVH despite a later age of FSGS onset, while adjusting for socioeconomic status. Treatment of obesity may be an important component of chronic kidney disease and LVH management in this population.

Patterns of Kidney Function Decline Associated with APOL1 Genotypes: Results from AASK.

Trajectories of eGFR in patients with CKD are highly variable. Only a subset of patients with CKD experiences a steady decline in eGFR. The objective of our study was to investigate whether eGFR trajectory patterns differ by APOL1 risk status. Our study was a longitudinal observational study of 622 participants in the African American Study of Kidney Disease and Hypertension with APOL1 genotyping and sufficient follow-up for estimating GFR trajectories. The predictor was APOL1 high-risk status (having two copies of the G1 or G2 risk alleles) versus low-risk status (zero or one copy of the risk alleles), and the outcome was four eGFR trajectory patterns on the basis of the joint probabilities of linearity and progression: steady decline, unsteady decline, steady stable, and unsteady stable. Over a median follow-up of 9 years, 24.0% of participants experienced steady eGFR decline, 25.9% had an unsteady decline, 25.6% were steady and stable, and 24.6% were unsteady but stable. Those experiencing steady decline had lower eGFR and higher urine protein-to-creatinine ratio at baseline than participants with the other eGFR trajectory patterns. The APOL1 high-risk group was associated with a greater odds for the steady decline pattern than the APOL1 low-risk group (unadjusted odds ratio, 2.45; 95% confidence interval, 1.62 to 3.69). This association remained significant after adjusting for demographic factors, baseline eGFR, urine protein-to-creatinine ratio, treatment assignment, and follow-up time (adjusted odds ratio, 1.59; 95% confidence interval, 1.00 to 2.52). Among patients with CKD attributed to hypertension, those with the APOL1 high-risk genotype were more likely to experience a steady decline trajectory in eGFR than those without the APOL1 high-risk genotype. These findings suggest a persistent underlying pathophysiologic process in those patients with the APOL1 high-risk genotype.

Brief Report: APOL1 Renal Risk Variants Are Associated With Chronic Kidney Disease in Children and Youth With Perinatal HIV Infection.

APOL1 renal risk alleles are associated with chronic kidney disease (CKD) in adults, with the strongest effect being for HIV-associated nephropathy. Their role in youth with perinatal HIV-1 infection (PHIV) has not been studied. In a nested case-control study of 451 PHIV participants in the Pediatric HIV/AIDS Cohort Study, we found a 3.5-fold increased odds of CKD in those carrying high-risk APOL1 genotypes using a recessive model [95% confidence interval (CI): 1.2 to 10.0]. We report an unadjusted incidence of 1.2 CKD cases/100 person-years (95% CI: 0.5 to 2.5) in PHIV youth carrying APOL1 high-risk genotypes, with important implications for sub-Saharan Africa.

Race, APOL1 Risk, and eGFR Decline in the General Population.

The APOL1 high-risk genotype, present in approximately 13% of blacks in the United States, is a risk factor for kidney function decline in populations with CKD. It is unknown whether genetic screening is indicated in the general population. We evaluated the prognosis of APOL1 high-risk status in participants in the population-based Atherosclerosis Risk in Communities (ARIC) study, including associations with eGFR decline, variability in eGFR decline, and related adverse health events (AKI, ESRD, hypertension, diabetes, cardiovascular disease, pre-ESRD and total hospitalization rate, and mortality). Among 15,140 ARIC participants followed from 1987-1989 (baseline) to 2011-2013, 75.3% were white, 21.5% were black/APOL1 low-risk, and 3.2% were black/APOL1 high-risk. In a demographic-adjusted analysis, blacks had a higher risk for all assessed adverse health events; however, in analyses adjusted for comorbid conditions and socioeconomic status, blacks had a higher risk for hypertension, diabetes, and ESRD only. Among blacks, the APOL1 high-risk genotype associated only with higher risk of ESRD in a fully adjusted analysis. Black race and APOL1 high-risk status were associated with faster eGFR decline (P<0.001 for each). However, we detected substantial overlap among the groups: median (10th-90th percentile) unadjusted eGFR decline was 1.5 (1.0-2.2)ml/min per 1.73m(2) per year for whites, 2.1 (1.4-3.1)ml/min per 1.73m(2) per year for blacks with APOL1 low-risk status, and 2.3 (1.5-3.5)ml/min per 1.73m(2) per year for blacks with APOL1 high-risk status. The high variability in eGFR decline among blacks with and without the APOL1 high-risk genotype suggests that population-based screening is not yet justified.

APOL1 Genotype and Kidney Transplantation Outcomes From Deceased African American Donors.

Two apolipoprotein L1 gene (APOL1) renal-risk variants in donors and African American (AA) recipient race are associated with worse allograft survival in deceased-donor kidney transplantation (DDKT) from AA donors. To detect other factors impacting allograft survival from deceased AA kidney donors, APOL1 renal-risk variants were genotyped in additional AA kidney donors. The APOL1 genotypes were linked to outcomes in 478 newly analyzed DDKTs in the Scientific Registry of Transplant Recipients. Multivariate analyses accounting for recipient age, sex, race, panel-reactive antibody level, HLA match, cold ischemia time, donor age, and expanded criteria donation were performed. These 478 transplantations and 675 DDKTs from a prior report were jointly analyzed. Fully adjusted analyses limited to the new 478 DDKTs replicated shorter renal allograft survival in recipients of APOL1 2-renal-risk-variant kidneys (hazard ratio [HR], 2.00; P = 0.03). Combined analysis of 1153 DDKTs from AA donors revealed donor APOL1 high-risk genotype (HR, 2.05; P = 3 × 10), older donor age (HR, 1.18; P = 0.05), and younger recipient age (HR, 0.70; P = 0.001) adversely impacted allograft survival. Although prolonged allograft survival was seen in many recipients of APOL1 2-renal-risk-variant kidneys, follow-up serum creatinine concentrations were higher than that in recipients of 0/1 APOL1 renal-risk-variant kidneys. A competing risk analysis revealed that APOL1 impacted renal allograft survival, but not recipient survival. Interactions between donor age and APOL1 genotype on renal allograft survival were nonsignificant. Shorter renal allograft survival is reproducibly observed after DDKT from APOL1 2-renal-risk-variant donors. Younger recipient age and older donor age have independent adverse effects on renal allograft survival.

Association of APOL1 Genotype with Renal Histology among Black HIV-Positive Patients Undergoing Kidney Biopsy.

Prior studies have shown that the APOL1 risk alleles are associated with a greater risk of HIV-associated nephropathy and FSGS among blacks who are HIV positive. We sought to determine whether the APOL1 high-risk genotype incrementally improved the prediction of these underlying lesions beyond conventional clinical factors. In a cross-sectional study, we analyzed data from 203 blacks who are HIV positive, underwent kidney biopsies between 1996 and 2011, and were genotyped for the APOL1 G1 and G2 alleles. Predictive logistic regression models with conventional clinical factors were compared with those that also included APOL1 genotype using receiver-operating curves and bootstrapping analyses with crossvalidation. The addition of APOL1 genotype to HIV-related risk factors for kidney disease in a predictive model improved the prediction of non-HIV-associated nephropathy FSGS, specifically, increasing the c statistic from 0.65 to 0.74 (P=0.04). Although two risk alleles were significantly associated with higher odds of HIV-associated nephropathy, APOL1 genotype did not add incrementally to the prediction of this specific histopathology. APOL1 genotype may provide additional diagnostic information to traditional clinical variables in predicting underlying FSGS spectrum lesions in blacks who are HIV positive. In contrast, although APOL1 risk genotype predicts HIV-associated nephropathy, it lacked a high c statistic sufficient for discrimination to eliminate the role of kidney biopsy in the clinical care of blacks who are HIV positive with nephrotic proteinuria or unexplained kidney disease.

Association of Hemoglobin S and C Traits with Kidney Disease in African Americans in the Reasons for Geographic and Racial Differences in Stroke (REGARDS) Study

Background: Sickle cell trait (SCT) and hemoglobin C trait are two of the most common inherited hemoglobin mutations in the world due to their malarial protective effects. APOL1 renal risk variants, which confer resistance to trypanosomal infection, are prevalent in African-ancestry populations and are associated with chronic kidney disease (CKD) and end-stage renal disease (ESRD). While an increased risk of CKD in SCT carriers has been demonstrated; there are conflicting data on SCT and the risk of ESRD, and the association between hemoglobin C trait and kidney disease remains unknown. Furthermore, whether co-inheritance of hemoglobin S or C and APOL1 gene risk variants contributes to the risk of CKD has not been established.Methods: The Reasons for Geographic and Racial Differences in Stroke (REGARDS) cohort enrolled 12,514 African-Americans age ≥ 45 years from the contiguous United States between 2003-2007. All participants consenting to genetic research were genotyped for hemoglobin S and hemoglobin C traits. Individuals with hemoglobin SS, SC, or CC genotypes were excluded from analysis. APOL1 high-risk genotypes were defined as the presence of two renal risk variants, G1/G1, G2/G2, or G1/G2. Prevalent CKD was defined as a baseline eGFR < 60mL/min/1.73 m2 and/or the presence of albuminuria ≥ 30mg/g based on spot urine albumin/creatinine ratio (ACR) measurements. Logistic regression was used to calculate odds ratios (OR) of prevalent CKD for hemoglobin S/C, and Cox regression was used to estimate risk of incident ESRD. All analyses were adjusted for age, sex, smoking, hypertension, diabetes, APOL1 high-risk genotype status, and baseline eGFR (for incident ESRD). A genetic interaction analysis of hemoglobin S/C variants and APOL1 high-risk genotypes on prevalent CKD was also performed.Results: A total of 10,481 African American participants, 7.5% with SCT and 2.5% with hemoglobin C trait, had available genetic data for analysis. As shown in table 1, prevalent CKD was significantly more common in SCT carriers than non-carriers, with an OR for CKD of 1.86 [95% CI 1.57-2.20]). In addition, individuals with SCT had a 1.5-fold increased hazard of incident ESRD compared to non-carriers, although this was not statistically significant. Hemoglobin C trait was not associated with prevalent CKD or incident ESRD, but the numbers were small. On genetic interaction analysis, co-inheritance of hemoglobin C and APOL1 high-risk genotypes significantly increased the risk of prevalent CKD (p-interaction=0.003), while co-inheritance of SCT and APOL1 high-risk genotypes did not appear to interact to increase CKD risk.Conclusions: In this large cohort of over 10,000 African Americans, SCT was associated with an increased risk of prevalent CKD and demonstrated a trend of association with incident ESRD. Hemoglobin C trait was not associated with prevalent CKD but may interact with APOL1 high-risk genotypes to potentiate the risk of CKD. Future studies are needed to further examine these gene-gene interactions and to establish the relationship between hemoglobin S/C traits and ESRD.Table 1Association of Hemoglobin S and C Traits with Prevalent CKD and Incident ESRDOutcomeNon-carriersHeterozygous Hgb S (Hgb AS)Heterozygous Hgb C (Hgb AC)Prevalent CKDN (%)2212 (24.5)266 (35.7)63 (25.7)Adjusted OR (95% CI)1.00 (ref)1.86 (1.57-2.20)0.98 (0.72-1.33)Incident ESRDN (%)110 (1.17)18 (2.30)5 (1.95)Incidence rate (N/1000 person-years)2.956.045.06Adjusted HR (95% CI)1.00 (ref)1.52 (0.91-2.52)2.30 (0.93-5.65) DisclosuresNo relevant conflicts of interest to declare.

Integrative Genomics Identifies Novel Associations with APOL1 Risk Genotypes in Black NEPTUNE Subjects.

APOL1 variants have been associated with renal phenotypes in blacks. To refine clinical outcomes and discover mechanisms of APOL1-associated kidney injury, we analyzed clinical and genomic datasets derived from 90 black subjects in the Nephrotic Syndrome Study Network (NEPTUNE), stratified by APOL1 risk genotype. Ninety subjects with proteinuria ≥0.5 g/d were enrolled at first biopsy for primary nephrotic syndrome and followed. Clinical outcomes were determined, and renal histomorphometry and sequencing of Mendelian nephrotic syndrome genes were performed. APOL1 variants were genotyped, and glomerular and tubulointerstitial transcriptomes from protocol renal biopsy cores were analyzed for differential and correlative gene expression. Analyses were performed under the recessive model (high-risk genotype defined by two risk alleles). APOL1 high-risk genotype was significantly associated with a 17 ml/min per 1.73 m(2) lower eGFR and a 69% reduction in the probability of complete remission at any time, independent of histologic diagnosis. Neither APOL1 risk group was enriched for Mendelian mutations. On renal biopsy, high-risk genotype was associated with increased fractional interstitial area, interstitial fibrosis, and tubular atrophy. Risk genotype was not associated with intrarenal APOL1 mRNA expression levels. Differential expression analysis demonstrated an increased steady-state level of five genes associated with the high-risk genotype (CXCL9, CXCL11, and UBD in glomerulus; SNOR14B and MUC13 in tubulointerstitium). APOL1 tubulointerstitial coexpression analysis showed coexpression of APOL1 mRNA levels with a group of intrarenal transcripts that together were associated with increased interstitial fibrosis and tubular atrophy. These data indicate the high-risk APOL1 genotype confers renal risk across histopathologic diagnoses.

The association between APOL1 risk alleles and longitudinal kidney function differs by HIV viral suppression status.

Existing data suggest that human immunodeficiency virus (HIV)-infected African Americans carrying 2 copies of the APOL1 risk alleles have greater risk of kidney disease than noncarriers. We sought to determine whether HIV RNA suppression mitigates APOL1-related kidney function decline among African Americans enrolled in the Multicenter AIDS Cohort Study. We genotyped HIV-infected men for the G1 and G2 risk alleles and ancestry informative markers. Mixed-effects models were used to estimate the annual rate of estimated glomerular filtration rate (eGFR) decline, comparing men carrying 2 (high-risk) vs 0-1 risk allele (low-risk). Effect modification by HIV suppression status (defined as HIV type 1 RNA level <400 copies/mL for >90% of follow-up time) was evaluated using interaction terms and stratified analyses. Of the 333 African American men included in this study, 54 (16%) carried the APOL1 high-risk genotype. Among HIV-infected men with unsuppressed viral loads, those with the high-risk genotype had a 2.42 mL/minute/1.73 m(2) (95% confidence interval [CI], -3.52 to -1.32) faster annual eGFR decline than men with the low-risk genotype. This association was independent of age, comorbid conditions, baseline eGFR, ancestry, and HIV-related factors. In contrast, the rate of decline was similar by APOL1 genotype among men with sustained viral suppression (-0.16 mL/minute/1.73 m(2)/year; 95% CI, -.59 to .27; P for interaction <.001). Unsuppressed HIV-infected African Americans with the APOL1 high-risk genotype experience an accelerated rate of kidney function decline; HIV suppression with antiretroviral therapy may reduce these deleterious renal effects.