APOL1-Associated Nephropathy: A Key Contributor to Racial Disparities in CKD

A focus on the association of Apol1 with kidney disease in children

Individuals of African origin have an increased risk of developing various progressive chronic kidney diseases (CKD). This risk has been attributed to genetic variants (G1, G2) in apolipoprotein-L1 (APOL1) gene. In the pediatric population, especially in children affected by sickle cell disease (SCD), by human immunodeficiency virus (HIV), or with various glomerular diseases, APOL1 risk variants have been associated with the development of hypertension, albuminuria, and more rapid decline of kidney function. The present review focuses on existing APOL1-related epidemiological data in children with CKD. It also includes data from studies addressing racial disparities in CKD, the APOL1-related innate immunity, and the relationship between APOL1 and CKD and pathogenic pathways mediating APOL1-related kidney injury.

APOL1 at 10 years: progress and next steps

APOL1 kidney risk variants (RVs) were identified in 2010 as major drivers of glomerular, tubulointerstitial, and renal microvascular disease in individuals with sub-Saharan African ancestry. In December 2020, the "APOL1 at Ten" conference summarized the first decade of progress and discussed controversies and uncertainties that remain to be addressed. Topics included trypanosome infection and its role in the evolution of APOL1 kidney RVs, clinical phenotypes in APOL1-associated nephropathy, relationships between APOL1 RVs and background haplotypes on cell injury and molecular mechanisms initiating disease, the role of clinical APOL1 genotyping, and development of novel therapies for kidney disease. Future goals were defined, including improved characterization of various APOL1 RV phenotypes in patients and experimental preclinical models; further dissection of APOL1-mediated pathways to cellular injury and dysfunction in kidney (and other) cells; clarification of gene-gene and gene-environment interactions; and evaluation of the role for existing and novel therapies.

APOL1 Nephropathy: From Genetics to Clinical Applications

Rates of many types of severe kidney disease are much higher in Black individuals than most other ethnic groups. Much of this disparity can now be attributed to genetic variants in the apoL1 (APOL1) gene found only in individuals with recent African ancestry. These variants greatly increase rates of hypertension-associated ESKD, FSGS, HIV-associated nephropathy, and other forms of nondiabetic kidney disease. We discuss the population genetics of APOL1 risk variants and the clinical spectrum of APOL1 nephropathy. We then consider clinical issues that arise for the practicing nephrologist caring for the patient who may have APOL1 kidney disease.

No support for the hereditarian hypothesis of the Black-White achievement gap using polygenic scores and tests for divergent selection

OBJECTIVES

Debate about the cause of IQ score gaps between Black and White populations has persisted within genetics, anthropology, and psychology. Recently, authors claimed polygenic scores provide evidence that a significant portion of differences in cognitive performance between Black and White populations are caused by genetic differences due to natural selection, the "hereditarian hypothesis." This study aims to show conceptual and methodological flaws of past studies supporting the hereditarian hypothesis.

MATERIALS AND METHODS

Polygenic scores for educational attainment were constructed for African and European samples of the 1000 Genomes Project. Evidence for selection was evaluated using an excess variance test. Education associated variants were further evaluated for signals of selection by testing for excess genetic differentiation (F_st ). Expected mean difference in IQ for populations was calculated under a neutral evolutionary scenario and contrasted to hereditarian claims.

RESULTS

Tests for selection using polygenic scores failed to find evidence of natural selection when the less biased within-family GWAS effect sizes were used. Tests for selection using F_st values did not find evidence of natural selection. Expected mean difference in IQ was substantially smaller than postulated by hereditarians, even under unrealistic assumptions that overestimate genetic contribution.

CONCLUSION

Given these results, hereditarian claims are not supported in the least. Cognitive performance does not appear to have been under diversifying selection in Europeans and Africans. In the absence of diversifying selection, the best case estimate for genetic contributions to group differences in cognitive performance is substantially smaller than hereditarians claim and is consistent with genetic differences contributing little to the Black-White gap.

Examining the Potential Impact of Race Multiplier Utilization in Estimated Glomerular Filtration Rate Calculation on African-American Care Outcomes

BACKGROUND

Advancing health equity entails reducing disparities in care. African-American patients with chronic kidney disease (CKD) have poorer outcomes, including dialysis access placement and transplantation. Estimated glomerular filtration rate (eGFR) equations, which assign higher eGFR values to African-American patients, may be a mechanism for inequitable outcomes. Electronic health record-based registries enable population-based examination of care across racial groups.

OBJECTIVE

To examine the impact of the race multiplier for African-Americans in the CKD-EPI eGFR equation on CKD classification and care delivery.

DESIGN

Cross-sectional study SETTING: Two large academic medical centers and affiliated community primary care and specialty practices.

PARTICIPANTS

A total of 56,845 patients in the Partners HealthCare System CKD registry in June 2019, among whom 2225 (3.9%) were African-American.

MEASUREMENTS

Exposures included race, age, sex, comorbidities, and eGFR. Outcomes were transplant referral and dialysis access placement.

RESULTS

Of 2225 African-American patients, 743 (33.4%) would hypothetically be reclassified to a more severe CKD stage if the race multiplier were removed from the CKD-EPI equation. Similarly, 167 of 687 (24.3%) would be reclassified from stage 3B to stage 4. Finally, 64 of 2069 patients (3.1%) would be reassigned from eGFR > 20 ml/min/1.73 m2 to eGFR ≤ 20 ml/min/1.73 m2, meeting the criterion for accumulating kidney transplant priority. Zero of 64 African-American patients with an eGFR ≤ 20 ml/min/1.73 m2 after the race multiplier was removed were referred, evaluated, or waitlisted for kidney transplant, compared to 19.2% of African-American patients with eGFR ≤ 20 ml/min/1.73 m2 with the default CKD-EPI equation.

LIMITATIONS

Single healthcare system in the Northeastern United States and relatively small African-American patient cohort may limit generalizability.

CONCLUSIONS

Our study reveals a meaningful impact of race-adjusted eGFR on the care provided to the African-American CKD patient population.

APOL1 risk variants affect podocyte lipid homeostasis and energy production in focal segmental glomerulosclerosis

Lipotoxicity was recently reported in several forms of kidney disease, including focal segmental glomerulosclerosis (FSGS). Susceptibility to FSGS in African Americans is associated with the presence of genetic variants of the Apolipoprotein L1 gene (APOL1) named G1 and G2. If and how endogenous APOL1 may alter mitochondrial function by the modifying cellular lipid metabolism is unknown. Using transgenic mice expressing the APOL1 variants (G0, G1 or G2) under endogenous promoter, we show that APOL1 risk variant expression in transgenic mice does not impair kidney function at baseline. However, APOL1 G1 expression worsens proteinuria and kidney function in mice characterized by the podocyte inducible expression of nuclear factor of activated T-cells (NFAT), which we have found to cause FSGS. APOL1 G1 expression in this FSGS-model also results in increased triglyceride and cholesterol ester contents in kidney cortices, where lipid accumulation correlated with loss of renal function. In vitro, we show that the expression of endogenous APOL1 G1/G2 in human urinary podocytes is associated with increased cellular triglyceride content and is accompanied by mitochondrial dysfunction in the presence of compensatory oxidative phosphorylation (OXPHOS) complexes elevation. Our findings indicate that APOL1 risk variant expression increases the susceptibility to lipid-dependent podocyte injury, ultimately leading to mitochondrial dysfunction.

Chromogranin A pathway: from pathogenic molecule to renal disease

BACKGROUND

Chromogranin A (CHGA) is an index granin protein critical for biogenesis and exocytotic release of catecholamine storage granules. It is elevated in plasma of patients with sympathetic over-activity and kidney dysfunction. Several CHGA polymorphisms are associated with hypertensive kidney disease. Previously, we unraveled the molecular mechanism by which CHGA expression is regulated in African Americans carrying a genetic variation associated with hypertensive chronic kidney disease (CKD).

METHOD

Experimental CKD mouse model were created by 5/6th nephrectomy (Npx) using wild-type and Chga-/- knockout mouse strains to delineate the role of CHGA in CKD.

RESULT

Wild-type-Npx mice expressing Chga developed exacerbated azotemia and fibrosis as compared with their knockout-Npx counterparts. Gene expression profiling revealed downregulation of mitochondrial respiratory complexes genes consistent with maladaptive mitochondria in wild-type-Npx mice, contrasted to knockout-Npx. In healthy individuals, an inverse relationship between circulating CHGA levels and glomerular function was observed. In vitro, mesangial cells treated with CHGA-triggered nitric oxide release by a signaling mechanism involving scavenger receptor SR-A. The CHGA-treated and untreated mesangial cells displayed differential expression of cytokine, chemokine, complement, acute phase inflammatory and apoptotic pathway genes. Thus, build-up of plasma CHGA because of kidney injury served as an insult to the mesangial cells resulting in expression of genes promoting inflammation, fibrosis, and progression of CKD.

CONCLUSION

These findings improve understanding of the role of elevated CHGA in the progression of CKD and reveal novel pathways that could be exploited for therapeutic strategies in hypertensive kidney disease.

Evolutionary genetics and acclimatization in nephrology

Evolutionary processes, including mutation, migration and natural selection, have influenced the prevalence and distribution of various disorders in humans. However, despite a few well-known examples, such as the APOL1 variants - which have undergone positive genetic selection for their ability to confer resistance to Trypanosoma brucei infection but confer a higher risk of chronic kidney disease - little is known about the effects of evolutionary processes that have shaped genetic variation on kidney disease. An understanding of basic concepts in evolutionary genetics provides an opportunity to consider how findings from ancient and archaic genomes could inform our knowledge of evolution and provide insights into how population migration and genetic admixture have shaped the current distribution and landscape of human kidney-associated diseases. Differences in exposures to infectious agents, environmental toxins, dietary components and climate also have the potential to influence the evolutionary genetics of kidneys. Of note, selective pressure on loci associated with kidney disease is often from non-kidney diseases, and thus it is important to understand how the link between genome-wide selected loci and kidney disease occurs in relation to secondary nephropathies.

Focal Segmental Glomerulosclerosis, Risk Factors for End Stage Kidney Disease, and Response to Immunosuppression

Background

FSGS is a heterogeneic glomerular disease. Risk factors for kidney disease ESKD and the effect of immunosuppression treatment (IST) has varied in previously published cohorts. These cohorts were limited by relatively small case numbers, short follow-up, lack of racial/ethnic diversity, a mix of adult and pediatric patients, lack of renin-angiotensin-aldosterone system (RAAS) inhibition, or lack of subgroup analysis of IST.

Methods

We compared demographics, clinical characteristics, histopathology, and IST to long-term renal survival in a large, ethnically diverse, adult cohort of 338 patients with biopsy-proven FSGS with long-term follow-up in the era of RAAS inhibition using data from the US Department of Defense health care network.

Results

Multivariate analysis showed that nephrotic-range proteinuria (NRP), eGFR <60 ml/min per 1.73 m², hypoalbuminemia, interstitial fibrosis and tubular atrophy, and interstitial inflammation at diagnosis and the absence of remission were all associated with worse long-term renal survival. IgM, C3, and a combination of IgM/C3 immunofluorescence staining were not associated with reduced renal survival. IST was not associated with improved renal survival in the whole cohort, or in a subgroup with NRP. However, IST was associated with better renal survival in a subgroup of patients with FSGS with both NRP and hypoalbuminemia and hypoalbuminemia alone.

Conclusions

Our study suggests that IST should be reserved for patients with FSGS and nephrotic syndrome. It also introduces interstitial inflammation as a potential risk factor for ESKD and does not support the proposed pathogenicity of IgM and complement activation.

Integration of genetic and histopathology data in interpretation of kidney disease

For many years renal biopsy has been the gold standard for diagnosis in many forms of kidney disease. It provides rapid, accurate and clinically useful information in most individuals with kidney disease. However, in recent years, other diagnostic modalities have become available that may provide more detailed and specific diagnostic information in addition to, or instead of, renal biopsy. Genomics is one of these modalities. Previously prohibitively expensive and time consuming, it is now increasingly available and practical in a clinical setting for the diagnosis of inherited kidney disease. Inherited kidney disease is a significant cause of kidney disease, in both the adult and paediatric populations. While individual inherited kidney diseases are rare, together they represent a significant burden of disease. Because of the heterogenicity of inherited kidney disease, diagnosis and management can be a challenge and often multiple diagnostic modalities are needed to arrive at a diagnosis. We present updates in genomic medicine for renal disease, how genetic testing integrates with our knowledge of renal histopathology and how the two modalities may interact to enhance patient care.

Preterm birth and neonatal acute kidney injury: implications on adolescent and adult outcomes

As a result of preterm birth, immature kidneys are exposed to interventions in the NICU that promote survival, but are nephrotoxic. Furthermore, the duration of renal development may be truncated in these vulnerable neonates. Immaturity and nephrotoxic exposures predispose preterm newborns to acute kidney injury (AKI), particularly in the low birth weight and extremely preterm gestational age groups. Several studies have associated preterm birth as a risk factor for future chronic kidney disease (CKD). However, only a few publications have investigated the impact of neonatal AKI on CKD development. Here, we will review the evidence linking preterm birth and AKI in the NICU to CKD and highlight the knowledge gaps and opportunities for future research. For neonatal intensive care studies, we propose the inclusion of AKI as an important short-term morbidity outcome and CKD findings such as a reduced glomerular filtration rate in the assessment of long-term outcomes.

Challenges in primary focal segmental glomerulosclerosis diagnosis: from the diagnostic algorithm to novel biomarkers

Primary or idiopathic focal segmental glomerulosclerosis (FSGS) is a kidney entity that involves the podocytes, leading to heavy proteinuria and in many cases progresses to end-stage renal disease. Idiopathic FSGS has a bad prognosis, as it involves young individuals who, in a considerably high proportion (∼15%), are resistant to corticosteroids and other immunosuppressive treatments as well. Moreover, the disease recurs in 30–50% of patients after kidney transplantation, leading to graft function impairment. It is suspected that this relapsing disease is caused by a circulating factor(s) that would permeabilize the glomerular filtration barrier. However, the exact pathologic mechanism is an unsettled issue. Besides its poor outcome, a major concern of primary FSGS is the complexity to confirm the diagnosis, as it can be confused with other variants or secondary forms of FSGS and also with other glomerular diseases, such as minimal change disease. New efforts to optimize the diagnostic approach are arising to improve knowledge in well-defined primary FSGS cohorts of patients. Follow-up of properly classified primary FSGS patients will allow risk stratification for predicting the response to different treatments. In this review we will focus on the diagnostic algorithm used in idiopathic FSGS both in native kidneys and in disease recurrence after kidney transplantation. We will emphasize those potential confusing factors as well as their detection and prevention. In addition, we will also provide an overview of ongoing studies that recruit large cohorts of glomerulopathy patients (Nephrotic Syndrome Study Network and Cure Glomerulonephropathy, among others) and the experimental studies performed to find novel reliable biomarkers to detect primary FSGS.

Domain-Specific Antibodies Reveal Differences in the Membrane Topologies of Apolipoprotein L1 in Serum and Podocytes

BACKGROUND

Circulating APOL1 lyses trypanosomes, protecting against human sleeping sickness. Two common African gene variants of APOL1, G1 and G2, protect against infection by species of trypanosomes that resist wild-type APOL1. At the same time, the protection predisposes humans to CKD, an elegant example of balanced polymorphism. However, the exact mechanism of APOL1-mediated podocyte damage is not clear, including APOL1's subcellular localization, topology, and whether the damage is related to trypanolysis.

METHODS

APOL1 topology in serum (HDL particles) and in kidney podocytes was mapped with flow cytometry, immunoprecipitation, and trypanolysis assays that tracked 170 APOL1 domain-specific monoclonal antibodies. APOL1 knockout podocytes confirmed antibody specificity.

RESULTS

APOL1 localizes to the surface of podocytes, with most of the pore-forming domain (PFD) and C terminus of the Serum Resistance Associated-interacting domain (SRA-ID), but not the membrane-addressing domain (MAD), being exposed. In contrast, differential trypanolytic blocking activity reveals that the MAD is exposed in serum APOL1, with less of the PFD accessible. Low pH did not detectably alter the gross topology of APOL1, as determined by antibody accessibility, in serum or on podocytes.

CONCLUSIONS

Our antibodies highlighted different conformations of native APOL1 topology in serum (HDL particles) and at the podocyte surface. Our findings support the surface ion channel model for APOL1 risk variant-mediated podocyte injury, as well as providing domain accessibility information for designing APOL1-targeted therapeutics.

Organ transplantation in persons with HIV

: With current antiretroviral therapy, the lifespan of newly diagnosed persons with HIV (PWH) approaches that of uninfected persons. However, metabolic abnormalities related to both the disease and the virus itself, along with comorbidities of aging, have resulted in end-organ disease and organ failure as a major cause of morbidity and mortality. Solid organ transplantation is a life-saving therapy for PWH who have organ failure, and the approval of the HIV Organ Policy Equity Act has opened and expanded opportunities for PWH to donate and receive organs. The current environment of organ transplantation for PWH will be reviewed and future directions of research and treatment will be discussed.

Lipotoxicity and Diabetic Nephropathy: Novel Mechanistic Insights and Therapeutic Opportunities

Lipotoxicity is characterized by the ectopic accumulation of lipids in organs different from adipose tissue. Lipotoxicity is mainly associated with dysfunctional signaling and insulin resistance response in non-adipose tissue such as myocardium, pancreas, skeletal muscle, liver, and kidney. Serum lipid abnormalities and renal ectopic lipid accumulation have been associated with the development of kidney diseases, in particular diabetic nephropathy. Chronic hyperinsulinemia, often seen in type 2 diabetes, plays a crucial role in blood and liver lipid metabolism abnormalities, thus resulting in increased non-esterified fatty acids (NEFA). Excessive lipid accumulation alters cellular homeostasis and activates lipogenic and glycogenic cell-signaling pathways. Recent evidences indicate that both quantity and quality of lipids are involved in renal damage associated to lipotoxicity by activating inflammation, oxidative stress, mitochondrial dysfunction, and cell-death. The pathological effects of lipotoxicity have been observed in renal cells, thus promoting podocyte injury, tubular damage, mesangial proliferation, endothelial activation, and formation of macrophage-derived foam cells. Therefore, this review examines the recent preclinical and clinical research about the potentially harmful effects of lipids in the kidney, metabolic markers associated with these mechanisms, major signaling pathways affected, the causes of excessive lipid accumulation, and the types of lipids involved, as well as offers a comprehensive update of therapeutic strategies targeting lipotoxicity.

Contemporary issues and new challenges in chronic kidney disease amongst people living with HIV

Chronic kidney disease (CKD) is a comorbidity of major clinical significance amongst people living with HIV (PLWHIV) and is associated with significant morbidity and mortality. The prevalence of CKD is rising, despite the widespread use of antiretroviral therapy (ART) and is increasingly related to prevalent non-infectious comorbidities (NICMs) and antiretroviral toxicity. There are great disparities evident, with the highest prevalence of CKD among PLWHIV seen in the African continent. The aetiology of kidney disease amongst PLWHIV includes HIV-related diseases, such as classic HIV-associated nephropathy or immune complex disease, CKD related to NICMs and CKD from antiretroviral toxicity. CKD, once established, is often relentlessly progressive and can lead to end-stage renal disease (ESRD). Identifying patients with risk factors for CKD, and appropriate screening for the early detection of CKD are vital to improve patient outcomes. Adherence to screening guidelines is variable, and often poor. The progression of CKD may be slowed with certain clinical interventions; however, data derived from studies involving PLWHIV with CKD are sparse and this represent an important area for future research. The control of blood pressure using angiotensin converting enzyme inhibitors and angiotensin receptor blockers, in particular, in the setting of proteinuria, likely slows the progression of CKD among PLWHIV. The cohort of PLWHIV is facing new challenges in regards to polypharmacy, drug-drug interactions and adverse drug reactions. The potential nephrotoxicity of ART is important, particularly as cumulative ART exposure increases as the cohort of PLWHIV ages. The number of PLWHIV with ESRD is increasing. PLWHIV should not be denied access to renal replacement therapy, either dialysis or kidney transplantation, based on their HIV status. Kidney transplantation amongst PLWHIV is successful and associated with an improved prognosis compared to remaining on dialysis. As the cohort of PLWHIV ages, comorbidity increases and CKD becomes more prevalent; models of care need to evolve to meet the new and changing chronic healthcare needs of these patients.

APOL1 Long-term Kidney Transplantation Outcomes Network (APOLLO): Design and Rationale

INTRODUCTION

Much of the higher risk for end-stage kidney disease (ESKD) in African American individuals relates to ancestry-specific variation in the apolipoprotein L1 gene (APOL1). Relative to kidneys from European American deceased-donors, kidneys from African American deceased-donors have shorter allograft survival and African American living-kidney donors more often develop ESKD. The National Institutes of Health (NIH)-sponsored APOL1 Long-term Kidney Transplantation Outcomes Network (APOLLO) is prospectively assessing kidney allograft survival from donors with recent African ancestry based on donor and recipient APOL1 genotypes.

METHODS

APOLLO will evaluate outcomes from 2614 deceased kidney donor-recipient pairs, as well as additional living-kidney donor-recipient pairs and unpaired deceased-donor kidneys.

RESULTS

The United Network for Organ Sharing (UNOS), Association of Organ Procurement Organizations, American Society of Transplantation, American Society for Histocompatibility and Immunogenetics, and nearly all U.S. kidney transplant programs, organ procurement organizations (OPOs), and histocompatibility laboratories are participating in this observational study. APOLLO employs a central institutional review board (cIRB) and maintains voluntary partnerships with OPOs and histocompatibility laboratories. A Community Advisory Council composed of African American individuals with a personal or family history of kidney disease has advised the NIH Project Office and Steering Committee since inception. UNOS is providing data for outcome analyses.

CONCLUSION

This article describes unique aspects of the protocol, design, and performance of APOLLO. Results will guide use of APOL1 genotypic data to improve the assessment of quality in deceased-donor kidneys and could increase numbers of transplanted kidneys, reduce rates of discard, and improve the safety of living-kidney donation.

Evaluating the promise of inclusion of African ancestry populations in genomics

The lack of representation of diverse ancestral backgrounds in genomic research is well-known, and the resultant scientific and ethical limitations are becoming increasingly appreciated. The paucity of data on individuals with African ancestry is especially noteworthy as Africa is the birthplace of modern humans and harbors the greatest genetic diversity. It is expected that greater representation of those with African ancestry in genomic research will bring novel insights into human biology, and lead to improvements in clinical care and improved understanding of health disparities. Now that major efforts have been undertaken to address this failing, is there evidence of these anticipated advances? Here, we evaluate the promise of including diverse individuals in genomic research in the context of recent literature on individuals of African ancestry. In addition, we discuss progress and achievements on related technological challenges and diversity among scientists conducting genomic research.

Genome-wide association study for time to failure of kidney transplants from African American deceased donors

Two renal-risk variants in the apolipoprotein L1 gene (APOL1) in African American (AA) deceased donors (DD) are associated with shorter renal allograft survival after transplantation. To identify additional genes contributing to allograft survival, a genome-wide association study was performed in 532 AA DDs. Phenotypic data were obtained from the Scientific Registry of Transplant Recipients. Association and single-nucleotide polymorphism (SNP)-by-APOL1 interaction tests were conducted using death-censored renal allograft survival accounting for relevant covariates. Replication and inverse-variance-weighted meta-analysis were performed using data from 250 AA DD in the Genomics of Transplantation study. Accounting for APOL1, multiple SNPs near the Nudix Hydrolase 7 gene (NUDT7) showed strong independent effects (P = 1.6 × 10^-8 -2.2 × 10^-8 ). Several SNPs in the Translocation protein SEC63 homolog (SEC63; P = 2 × 10^-9 -3.7 × 10^-8 ) and plasmacytoma variant translocation 1 (PVT1) genes (P = 4.0 × 10^-8 -7 × 10^-8 ) modified the effect of APOL1 on allograft survival. SEC63 is expressed in human renal tubule cells and glomeruli, and PVT1 is associated with diabetic kidney disease. Overall, associations were detected for 41 SNPs (P = 2 × 10^-9 -5 × 10^-8 ) contributing independently or interacting with APOL1 to impact renal allograft survival after transplantation from AA DD. Given the small sample size of the discovery and replication sets, independent validations and functional genomic efforts are needed to validate these results.

The Missing Diversity in Human Genetic Studies

The majority of studies of genetic association with disease have been performed in Europeans. This European bias has important implications for risk prediction of diseases across global populations. In this commentary, we justify the need to study more diverse populations using both empirical examples and theoretical reasoning.

Nephrotoxicity in a Patient With Inadequate Pain Control: Potential Role of Pharmacogenetic Testing for Cytochrome P450 2D6 and Apolipoprotein L1

A case is presented which demonstrates the perils of opioid inefficacy and how pharmacogenomic testing may have prevented nonsteroidal anti-inflammatory drug (NSAID)-induced nephrotoxicity and progression to chronic kidney disease (CKD). A 62 year-old female with back pain was treated with tramadol and hydrocodone; however, neither proved effective. Consequently, to control her pain, she resorted to cocaine, marijuana, and high dose nonsteroidal anti-inflammatory drugs (NSAIDs). She eventually developed CKD. To identify CKD contributors, she underwent genotyping for Apolipoprotein L1 (APOL1), a known risk factor of CKD, as well as relevant pharmacogenomic genes. Her APOL1 genotype was *G1(GM)/*G1(GM), placing her at increased risk of CKD progression. Her CYP2D6 genotype was *5/*17, consistent with intermediate metabolism, making opioid drugs reliant on CYP2D6 activation, such as tramadol and hydrocodone, relatively ineffective in this patient. Thus, this patient was at genetic risk for CKD and reduced opioid efficacy. We conclude that this genetic combination likely contributed to opioid inefficacy and the eventual progression to CKD.

THE GORDON WILSON LECTURE: THE ETHICS OF HUMAN GENOME EDITING

Human genome editing has undergone major technological advances, raising the possibility of treating or preventing many illnesses. Somatic (nonheritable) genome editing, both in vitro and in vivo, is already being employed under a robust regulatory and ethical framework developed for human gene therapy. In contrast, the prospect of germline (heritable) genome editing is much more contentious, and there is currently no consensus on the proper path forward. The 2017 National Academy of Sciences (NAS) and National Academy of Medicine (NAM) report proposed a series of requirements designed to minimize ethical objections while allowing couples to accept the risks of genome editing in order to have a biologically related child without passing on a known genetic disorder. It is vital to prevent gene editing from resulting in unintended negative consequences for individuals with genetic variants. The utilization of genome editing to enhance human function is highly contentious; it may be better to focus on whether an edit creates an "unfair advantage" rather than an enhancement.

Prevalence of APOL1 Risk Variants in Afro-Descendant Patients with Chronic Kidney Disease in a Latin American Country

Introduction

In Colombia, the genetic background of the populations was shaped by different levels of admixture between Natives, European, and Africans. Approximately 35.363 patients have diagnosed chronic kidney disease and according to population studies, 10.4% of these patients are Afro-descendant. We aim to assess the frequency of APOL1 variants G1 and G2 in Afro-descendant patients with ESRD treated at la Fundacion Valle del Lili University Hospital in Cali, Colombia.

Methods

This is an observational cross-sectional study. Afro-descendant patients with ESRD in waitlist or recipients of kidney transplant were evaluated. Clinical data were collected from the electronic medical records. Genotyping was carried out by amplification of the exon 7 of the APOL1 gene. For the identification of risk genotypes, the bioinformatics tool BLAST was used.

Results

We enrolled 102 participants. The frequency of APOL1 risk variants was 67.2%, in which 24.5% (n = 25) were G1 heterozygous and 5.8% (n = 6) were G2 heterozygous and 37% of the patients had high-risk status with two alleles in homozygous (G1/G1 = 21 and G2/G2 = 3) or compound heterozygote (G1/G2 = 14) form.

A high likelihood of increase in end-stage renal disease among the Japanese HIV-infected population

Kidneys are affected by human immunodeficiency virus (HIV) infection and its associated therapies. Antiretroviral therapy (ART) has markedly reduced acquired immune deficiency syndrome–related deaths and opportunistic infectious diseases among HIV-infected patients. This contributed to their prolonged survival; however, the improvement in survival has been accompanied by an increase in the incidence of non-infectious chronic complications, including hypertension, metabolic diseases, and chronic kidney disease (CKD). Recent studies showed that estimated prevalence of any CKD and end-stage renal disease (ESRD) among HIV-infected patients is approximately 20% and 0.5%, respectively, in Japan. Both a rapid decrease in renal function and a high positive rate of albuminuria and proteinuria are clinical characteristics of HIV-infected patients. Moreover, considering higher complication rates of hypertension and diabetes compared with non-HIV-infected individuals of the similar aging, HIV-infected patients who develop CKD and ESRD are very likely to increase. Furthermore, as the survival rate is favorable after the initiation of dialysis, the cumulative number of ESRD patients is supposed to increase. The corporation for treatment of HIV-positive hemodialysis patients by general dialysis clinics will be urgently required; however, there still remain some preoccupations and prejudices about HIVper sein Japan, which may provoke hesitation from accepting those patients.

[Kidney disease care for the elderly]

In our aging population, kidney disease management needs to take into account the frailty of the elderly. Standardized geriatric assessments can be proposed to help clinicians apprehend this dimension in their daily practice. These tools allow to better identify frail patients and offer them more personalized and harmless treatments. This article aims to focus on the kidney diseases commonly observed in elderly patients and analyze their specific nephrogeriatric care modalities. It should be noticed that all known kidney diseases can be also observed in the elderly, most often with a quite similar clinical presentation. This review is thus focused on the diseases most frequently and most specifically observed in elderly patients (except for monoclonal gammopathy associated nephropathies, out of the scope of this work), as well as the peculiarities of old age nephrological care.

Lupus nephritis: challenges and progress

PURPOSE OF REVIEW

The management of lupus nephritis remains unsatisfactory due to insufficiently effective treatment regimens and the dearth of reliable predictors of disease onset or progression to guide individualized therapeutic decisions. This review summarizes new findings related to lupus nephritis over the last 18 months and discusses clinical needs that should be considered to advance trials of mechanism-based therapeutic strategies.

RECENT FINDINGS

Collaborative teams are addressing how to improve disease definitions and are developing predictive models for disease onset, disease response and risk of flare in individual patients. More attention is being paid to clinical trial design. Advanced technologic approaches are allowing the analysis of small amounts of human tissue and urine in unprecedented detail so as to discover new pathogenic mechanisms and identify disease biomarkers. Novel therapies continue to be tested in disease models and include new strategies to protect renal tissue from cell damage and fibrosis.

SUMMARY

The collaborative efforts of patients, clinical and translational researchers, the pharmaceutical industry and funding sources are needed to advance therapies for lupus nephritis. Specialized clinical centers can then deliver optimal and more personalized patient care that will improve patient outcomes.

APOL1 Genetic Testing in Living Kidney Transplant Donors

The presence of 2 apolipoprotein L1 gene (APOL1) risk variants is associated with increased risk for chronic kidney disease and end-stage kidney disease. Inferior allograft outcomes following transplantation with kidneys from donors with 2 risk variants have also been reported. These data, coupled with anecdotal case reports and a recent cohort study of living donors, raise important questions about the potential increased kidney disease risk for living donors with APOL1 risk variants and the need for testing as part of the standard living donor evaluation process. We identify a series of questions that are central to the development of clinical policy regarding APOL1 testing of potential living kidney donors given the current uncertainty over the clinical implications of having 2 risk variants. We explore the ethical challenges that arise when determining when and to whom APOL1 testing should be offered, what potential donors should be told about APOL1 testing, how test results should be used to determine suitability for donation, if and when recipients should have access to results, and how clinical policy regarding APOL1 testing should be established.

Rethinking the ethical principles of genomic medicine services

Clinical genome and exome sequencing is currently used in only a small fraction of patients, yet large scale genomic initiatives are becoming more embedded in clinical services. This paper examines the ethical principles that should guide regulatory processes regarding consent and data sharing in this context. We argue that a genomic dataset administered by the health system carries substantial societal benefits, and that the collective nature of this initiative means that at least those patients who benefit from genome sequencing have an ethical obligation to share their health information. This obligation is grounded in considerations of fairness. Furthermore, we argue that the use of genomic data for the advancement of medical knowledge should be permitted without explicit consent and that international and other bodies should be granted access to these data, provided certain conditions are satisfied.

Kidney Disease in African American Children: Biological and Nonbiological Disparities

Pediatric-onset chronic kidney disease (CKD) is as relevant to adults as it is to children. Congenital anomalies of the kidney and urinary tract may have a significant impact on health from birth or during childhood or may not manifest until adulthood. Many acquired kidney diseases start to appear in late childhood and adolescence. The propensity for more rapid progression of CKD to end-stage kidney disease in adults of African ancestry, as well as disparities in access to kidney transplantation and allograft longevity, have been well documented for decades. Similar disparate patterns are seen in children, and we now know that there are a range of biological and nonbiological risk factors for the development and progression of CKD in people of African descent that are pertinent to CKD in children. In some cases, it is unclear whether there are effective potential interventions, whereas in other situations, there are opportunities to improve outcomes.

Autosomal dominant tubulointerstitial kidney disease

Autosomal dominant tubulointerstitial kidney disease (ADTKD) is a recently defined entity that includes rare kidney diseases characterized by tubular damage and interstitial fibrosis in the absence of glomerular lesions, with inescapable progression to end-stage renal disease. These diseases have long been neglected and under-recognized, in part due to confusing and inconsistent terminology. The introduction of a gene-based, unifying terminology led to the identification of an increasing number of cases, with recent data suggesting that ADTKD is one of the more common monogenic kidney diseases after autosomal dominant polycystic kidney disease, accounting for ~5% of monogenic disorders causing chronic kidney disease. ADTKD is caused by mutations in at least five different genes, including UMOD, MUC1, REN, HNF1B and, more rarely, SEC61A1. These genes encode various proteins with renal and extra-renal functions. The mundane clinical characteristics and lack of appreciation of family history often result in a failure to diagnose ADTKD. This Primer highlights the different types of ADTKD and discusses the distinct genetic and clinical features as well as the underlying mechanisms.

African Americans, Kidney Disease, and Drug Development: A Regulatory Perspective

Given the burden of kidney disease in African Americans, the discovery of safe and effective medical products to slow the progression of kidney disease and reduce the risk for kidney failure would have a tremendous impact on this population. Differences in response to treatment have been observed in African Americans, highlighting the importance of studying medical products in African Americans. Although historically the African American community has not been well represented in clinical trials, efforts are underway to address this issue. Recent advances in understanding the genetic contributions to disease progression in African Americans, including the discovery of risk variants in the apolipoprotein L1 gene (APOL1), raise the possibility of using genetic information to better tailor treatments for African Americans. One could envision developing therapies that target these variants or possibly using them to help enrich trial populations with patients more likely to experience disease progression.

Apolipoprotein L1 Testing in African Americans: Involving the Community in Policy Discussions

BACKGROUND

Apolipoprotein A1 (APOL1) gene variants occurring in people of West African descent contribute to the greater burden of kidney disease among African Americans. These variants are associated with increased risk of nondiabetic nephropathy, more rapid progression of chronic kidney disease, and shorter survival of donor kidneys after transplantation. However, only a minority of people with APOL1-associated risk develops kidney disease and specific clinical measures to address APOL1-associated risk are lacking. Given these uncertainties, we sought to engage members of the African American public in discussions with other stakeholders about the appropriate use of APOL1 testing.

METHODS

Formative interviews with community members, researchers, and clinicians in Seattle WA, Nashville TN, and Jackson MS, provided baseline information about views toward APOL1 testing and informed the design of 3 community-based deliberations among African Americans. A national meeting held in March 2018 included 13 community members, 7 scientific advisors and 26 additional researchers, clinicians, bioethicists, patient advocates, and representatives from professional organizations and federal funding agencies. Using small break-out and plenary discussion, the group agreed on recommendations based on current knowledge about APOL1-associated risk.

RESULTS

Meeting outcomes included recommendations to develop educational materials about APOL1 for community members and clinicians; to offer APOL1 research results to participants; and on the use of APOL1testing in kidney transplant programs. The group recommended against the routine offer of APOL1 testing in clinical care. Areas of disagreement included whether kidney transplant programs should require APOL1 testing of prospective living donors or bar individuals with APOL1 risk from donating kidneys and whether testing should be available on request in routine clinical care.

CONCLUSION

We recommend continued discussion among stakeholders and concerted efforts to ensure active and informed participation of members of the affected community to guide research on APOL1 and kidney disease.

Kidney Disease in HIV Infection

Antiretroviral therapy (ART) has significantly improved life expectancy of infected subjects, generating a new epidemiological setting of people aging withHuman Immunodeficiency Virus (HIV). People living with HIV (PLWH), having longer life expectancy, now face several age-related conditions as well as side effects of long-term exposure of ART. Chronic kidney disease (CKD) is a common comorbidity in this population. CKD is a relentlessly progressive disease that may evolve toward end-stage renal disease (ESRD) and significantly affect quality of life and risk of death. Herein, we review current understanding of renal involvement in PLWH, mechanisms and risk factors for CKD as well as strategies for early recognition of renal dysfunction and best care of CKD.

A Focus Group Study on African American Living Donors’ Treatment Preferences, Sociocultural Factors, and Health Beliefs About Apolipoprotein L1 Genetic Testing

Introduction:

Because apolipoprotein L1 ( APOL1) risk variants may contribute to live donors’ kidney failure postdonation, professional guidelines suggest informing potential donors with African ancestry about the availability of APOL1 genotyping. This study assessed African American (AA) donors’ perceptions of APOL1 genetic testing and how APOL1 may affect ethnic identity.

Methods/Approach:

Four focus groups were conducted with AA donors about their decision-making for and perceptions of APOL1 genetic testing and donation to inform a new culturally targeted educational brochure on APOL1 genetic testing. Qualitative data were analyzed by thematic analysis.

Findings:

Seventeen donors participated (47% participation rate). Four major themes emerged. (1) In hypothetical scenarios, most participants would have undergone APOL1 testing during donor evaluation to make a more informed decision, but many would have still donated. (2) Participants desired information about how having 2 APOL1 risk variants affects the donor’s and the recipient’s health. (3) Participants referred to diversity of genetic ancestry and cultural constructions of racial/ethnic identity to question the population at risk for APOL1 risk variants and recommended that all potential donors undergo genetic testing and receive education about APOL1. (4) Participants worried that out-of-pocket costs would deter APOL1 testing and that APOL1 could become a preexisting condition and discriminate against AAs.

Discussion:

Our findings suggest that AA donors desire APOL1 testing to foster informed consent. Transplant clinicians should be aware of these responses to APOL1 testing and be sensitive to historical issues of distrust and discrimination.

Balancing the genetic risk of APOL1 kidney disease variants

African-Americans exhibit an excess risk for chronic and end-stage kidney disease compared to the non-African populations. Two APOL1 genetic variants were shown to account for the majority of this racial disparity in glomerulopathies and other non-diabetic kidney disease. The high-risk genotype has only been reported in populations with recent African ancestry (14 % in African-Americans and up to more than 30 % in West Africa). In less than 10 years, the community has accumulated extensive knowledge on APOL1 and its genetic variants, from their positive selection for resistance against African trypanosomes to potential molecular mechanisms of podocyte injury. Finally, APOL1 associations with kidney transplantation outcomes and with postdonation end-stage kidney disease in living donors have paved the way for a personalized medicine implementation of APOL1 genotyping.

The Future of Genomic Studies Must Be Globally Representative: Perspectives from PAGE

The past decade has seen a technological revolution in human genetics that has empowered population-level investigations into genetic associations with phenotypes. Although these discoveries rely on genetic variation across individuals, association studies have overwhelmingly been performed in populations of European descent. In this review, we describe limitations faced by single-population studies and provide an overview of strategies to improve global representation in existing data sets and future human genomics research via diversity-focused, multiethnic studies. We highlight the successes of individual studies and meta-analysis consortia that have provided unique knowledge. Additionally, we outline the approach taken by the Population Architecture Using Genomics and Epidemiology (PAGE) study to develop best practices for performing genetic epidemiology in multiethnic contexts. Finally, we discuss how limiting investigations to single populations impairs findings in the clinical domain for both rare-variant identification and genetic risk prediction.

Apolipoprotein L1 and kidney transplantation

PURPOSE OF REVIEW

Consistent associations between variants of the apolipoprotein L1 (APOL1) gene and nondiabetic nephropathy have been reported in individuals of African descent. Donor APOL1 genotype has also been linked to shorter renal allograft survival. This review summarizes recent advances in understanding the biology of APOL1 and their implications to kidney donors and recipients.

RECENT FINDINGS

Approximately 12-13% of African Americans have two renal risk APOL1 variants but most do not develop kidney disease. Although the exact mechanisms linking APOL1 genotype to renal injury are not known, evidence from new experimental models suggests APOL1 mutations may accelerate age-related podocyte loss. Recent epidemiological studies indicate potential kidney donors with high-risk APOL1 variants have increased risk of chronic kidney disease (CKD) and donors with high-risk APOL1 variants have lower estimated glomerular filtration rate (eGFR) than those with low-risk variants. The absolute risk of CKD in otherwise healthy individuals carrying high-risk APOL1 mutations is likely low.

SUMMARY

Recent studies suggest high-risk APOL1 mutations in kidney donors are linked to shorter graft survival and lower postdonation eGFR. APOL1 genotyping may be used as one of many factors that contribute to assessment of the risk of postdonation CKD and informed decision making.

Kidney Disease Among African Americans: A Population Perspective

End-stage kidney disease and earlier stages of chronic kidney disease (CKD) represent one of the most dramatic examples of racial/ethnic disparities in health in our nation. African Americans are 3 times more likely to require renal replacement therapy then their non-Hispanic white counterparts. This article describes CKD-related disparities linked to a variety of clinical, socioeconomic, and cultural factors, as well as to select social determinants of health that are defined by social positioning and often by race within the United States. Our advancing understanding of these issues has led to improvements in patient outcomes and is narrowing the gap in disparities across most aspects of CKD and CKD risk factors. There are also extensive data indicating similar improvements in quality measures for patients on dialysis therapy. This article also reviews the state of CKD in African Americans from a population perspective and provides recommendations for the way forward.