Apolipoprotein L1, income and early kidney damage

Novel Therapies in APOL1-Mediated Kidney Disease: From Molecular Pathways to Therapeutic Options

Apolipoprotein L1 (APOL1) high-risk variants confer an increased risk for the development and progression of kidney disease among individuals of recent African ancestry. Over the past several years, significant progress has been made in understanding the pathogenesis of APOL1-mediated kidney diseases (AMKD), including genetic regulation, environmental interactions, immunomodulatory, proinflammatory and apoptotic signaling processes, as well as the complex role of APOL1 as an ion channel. Collectively, these findings have paved the way for novel therapeutic strategies to mitigate APOL1-mediated kidney injury. Precision medicine approaches are being developed to identify subgroups of AMKD patients who may benefit from these targeted interventions, fueling hope for improved clinical outcomes. This review summarizes key mechanistic insights in the pathogenesis of AMKD, emergent therapies, and discusses future challenges.

Association between socioeconomic position and cystatin C in the Heinz Nixdorf Recall Study

Social inequalities in health and disease are well studied. Less information is available on inequalities in biomarker levels indicating subclinical stages of disease such as cystatin C, an early diagnostic marker of renal dysfunction and predictor for cardiovascular disease. We evaluated the relationship between cystatin C, socioeconomic position (SEP) and established cardiovascular risk factors in a population-based study. In 4475 men and women aged 45–75 years participating in the baseline examination of the Heinz Nixdorf Recall Study cystatin C was measured from serum samples with a nephelometric assay. SEP was assessed by education and household income. Linear regression models were used to analyse the association between SEP and cystatin C as well as the impact of cardiovascular risk factors (i.e., body mass index, blood pressure, blood glucose, diabetes mellitus, blood lipids, C-reactive protein, smoking) on this association. After adjustment for age and sex cystatin C decreased by 0.019 mg/l (95% confidence interval (CI) − 0.030 to − 0.008) per five years of education. While using a categorical education variable cystatin C presented 0.039 mg/l (95% CI 0.017–0.061) higher in men and women in the lowest educational category (≤ 10 years of education) compared to the highest category (≥ 18 years). Concerning income, cystatin C decreased by 0.014 mg/l (95% CI − 0.021 to − 0.006) per 1000 € after adjustment for age and sex. For men and women in the lowest income quartile cystatin C was 0.024 mg/l (95% CI 0.009–0.038) higher compared to the highest income quartile. After adjusting for established cardiovascular risk factors the observed associations were substantially diminished. Social inequalities seem to play a role in subclinical stages of renal dysfunction, which are also related to development of cardiovascular disease. Adjustment for traditional cardiovascular risk factors showed that these risk factors largely explain the association between SEP and cystatin C.

Diagnosis, Education, and Care of Patients with APOL1-Associated Nephropathy: A Delphi Consensus and Systematic Review

BACKGROUND

APOL1 variants contribute to the markedly higher incidence of ESKD in Blacks compared with Whites. Genetic testing for these variants in patients with African ancestry who have nephropathy is uncommon, and no specific treatment or management protocol for APOL1-associated nephropathy currently exists.

METHODS

A multidisciplinary, racially diverse group of 14 experts and patient advocates participated in a Delphi consensus process to establish practical guidance for clinicians caring for patients who may have APOL1-associated nephropathy. Consensus group members took part in three anonymous voting rounds to develop consensus statements relating to the following: (1) counseling, genotyping, and diagnosis; (2) disease awareness and education; and (3) a vision for management of APOL1-associated nephropathy in a future when treatment is available. A systematic literature search of the MEDLINE and Embase databases was conducted to identify relevant evidence published from January 1, 2009 to July 14, 2020.

RESULTS

The consensus group agreed on 55 consensus statements covering such topics as demographic and clinical factors that suggest a patient has APOL1-associated nephropathy, as well as key considerations for counseling, testing, and diagnosis in current clinical practice. They achieved consensus on the need to increase awareness among key stakeholders of racial health disparities in kidney disease and of APOL1-associated nephropathy and on features of a successful education program to raise awareness among the patient community. The group also highlighted the unmet need for a specific treatment and agreed on best practice for management of these patients should a treatment become available.

CONCLUSIONS

A multidisciplinary group of experts and patient advocates defined consensus-based guidance on the care of patients who may have APOL1-associated nephropathy.

Social Determinants of CKD Hotspots

Chronic kidney disease (CKD) hotspots are defined as countries, regions, communities, or ethnicities with a higher than average incidence of CKD when compared with the worldwide, country, or regional rates. Here, we describe what is known about socially determined CKD hotspots, that is, the burden of CKD among socially defined communities that often collocate geographically. We focus on the poor, the homeless, and the food insecure, and their intersection with other social determinants of health, including race/ethnicity. In addition to discussing the burden of CKD in these communities, we describe some efforts to mitigate this burden and identify gaps in current knowledge.

Genetics and ESKD Disparities in African Americans

African Americans have a 2- to 4-fold greater incidence of end-stage kidney disease (ESKD) than whites, which has long raised the possibility of a genetic cause for this disparity. Recent advances in genetic studies have shown a causal association of polymorphisms at the apolipoprotein L1 gene (APOL1) with the markedly increased risk for the nondiabetic component of the overall disparity in ESKD in African Americans. Although APOL1-associated kidney disease is thought to account for a substantial proportion of ESKD in African Americans, not all the increased risk for ESKD is accounted for, and a complete cataloging of disparities in genetic causes of ESKD eludes our current understanding of genetic-associated kidney disease. Genetic testing aids the screening, diagnosis, prognosis, and treatment of diseases with a genetic basis. Widespread use of genetic testing in clinical practice is limited by the small number of actionable genetic variants, limited health literacy of providers and patients, and underlying complex ethical, legal, and social issues. This perspective reviews racial and ethnic differences associated with genetic diseases and the development of ESKD in African Americans and discusses potential uncertainties associated with our current understanding of penetrance of genetically linked kidney disease and population-attributable risk percent.

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.

APOL1 Risk Genotypes Are Associated With Early Kidney Damage in Children in Sub-Saharan Africa

INTRODUCTION

Apolipoprotein-L1 (APOL1) risk variants G1 and G2 increase the risk of chronic kidney disease (CKD), including HIV-related CKD, among African Americans. However, such data from populations living in Africa, especially children, remain limited. Our research aimed to determine the prevalence of APOL1 risk variants and to assess the association between these variants and early-stage CKD in the general pediatric population and HIV-infected children.

METHODS

In a cross-sectional study, we enrolled 412 children from the general population and 401 HIV-infected children in Kinshasa, Democratic Republic of Congo (DRC). APOL1 high-risk genotype (HRG) was defined by the presence of 2 risk variants (G1/G1, G2/G2, or G1/G2), and low-risk genotype (LRG) by the presence of 0 or 1 risk variants. The main outcome was elevated albuminuria, defined as a urinary albumin/creatinine ratio ≥30 mg/g.

RESULTS

APOL1 sequence analysis revealed that in the general population, 29 of 412 participants (7.0%) carried HRG, 84 of 412 (20.4%) carried the G1/G0 genotype, and 61 of 412 (14.8%) carried the G2/G0 genotype. In HIV-infected children, 23 of 401 (5.7%) carried HRG, and the same trend as in the general population was observed in regard to the prevalence of LRG. Univariate analysis showed that in the general population, 5 of 29 participants (17.2%) carrying HRG had elevated albuminuria, compared with 35 of 383 (9.0%) with LRG (odds ratio [OR] 2.1, 95% confidence interval [CI] 0.6-6.0; P = 0.13). In HIV-infected children, participants who carried APOL1 HRG had almost 22-fold increased odds of albuminuria compared to those with LRG.

CONCLUSION

The APOL1 risk variants are prevalent in children living in DRC. HRG carriers have increased odds of early kidney disease, and infection with HIV dramatically increases this probability.

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.

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.

Clinical Genetic Testing for APOL1: Are we There Yet?

End-stage renal disease (ESRD) disproportionately affects African Americans, who are two to four times more likely than European Americans to develop ESRD. Two independent variants of the apolipoprotein L1 (APOL1) gene, G1 and G2, have been associated with a 7- to 10-fold greater risk of developing nondiabetic ESRD in African Americans. Those who inherit two risk variants (G1/G1, G2/G2, or G1/G2) are also more likely to develop ESRD at a younger age and to have progression of chronic kidney disease. Currently, it is not known what proportion of persons with high-risk genotypes will develop ESRD in the general population, the exact mechanism of injury for APOL1-related risk, its relation to environmental exposures, or whether patients with comorbid conditions are more likely to develop ESRD. To address the above uncertainties, research that includes assessment of APOL1 status is needed before guidelines for general testing can be endorsed. Currently, APOL1 testing has been proposed as part of kidney transplant protocols both for living donors and recipients. However, because of uncertainties regarding the clinical implications of APOL1 variants, testing could generate confusion, anxiety, or stigma. Multiple forms of evidence, including the views of community members, are needed to support responsible approaches to providing information about APOL1 status as part of clinical care or in population screening. Informed consent with subsequent counseling regarding the risks and benefits of APOL1 testing should be considered for patients at high risk.

Associations between socioeconomic status and chronic kidney disease: a meta-analysis

BACKGROUND

Socioeconomic status (SES) has long been conjectured to be associated with the incidence and progression of chronic kidney disease (CKD), but few studies have examined this quantitatively. This meta-analysis aims to fill this gap.

METHODS

A systematic literature review was performed using Medline and EMBASE to identify observational studies on associations between SES and incidence and progression of CKD, published between 1974 and March 2017. Individual results were meta-analysed using a random effects model, in line with Meta-analysis of Observational Studies in Epidemiology guidelines.

RESULTS

In total, 43 articles met our inclusion criteria. CKD prevalence was associated with several indicators of SES, particularly lower income (OR 1.34, 95% CI (1.18 to 1.53), P<0.001; I²=73.0%, P=0.05); lower education (OR 1.21, 95% CI (1.11 to 1.32), P<0.001; I²=45.20%, P=0.034); and lower combined SES (OR 2.18, 95% CI (1.64 to 2.89), P<0.001; I²=0.0%, P=0.326). Lower levels of income, occupation and combined SES were also significantly associated with progression to end-stage renal disease (risk ratio (RR) 1.24, 95% CI (1.12 to 1.37), P<0.001; I²=66.6%, P=0.006; RR 1.05, 95% CI (1.01 to 1.09), P=0.012; I²=0.0%, P=0.796; and RR 1.39, 95% CI (1.09 to 1.79), P=0.009; I²=74.2%, P=0.009). Subgroup analyses generally confirmed these results, except in a few cases, such as an inverse association related to particular socioeconomic backgrounds and where results were adjusted by more disease-related risk factors.

CONCLUSION

Lower income was most closely associated with prevalence and progression of CKD, and lower education was significantly associated with its prevalence. Evidence for other indicators was inconclusive.

The evolving science of apolipoprotein-L1 and kidney disease

PURPOSE OF REVIEW

There are evolving epidemiological and biological data to support an association between the gene encoding apolipoprotein-L1 (APOL1) and progressive chronic kidney disease (CKD) among African-Americans.

RECENT FINDINGS

Individuals with two APOL1 risk alleles are at greater risk of incident albuminuria, CKD, and progression to end-stage renal disease despite optimal blood pressure management and use of angiotensin-converting enzyme inhibitors. These variants also appear to influence outcomes in donor and recipients in kidney transplantation. Recent studies have also variably shown a potential role of APOL1 variants in cardiovascular disease. A number of studies have addressed genetic and environmental factors such as HIV but most do not modify the course of APOL1-related kidney disease. Although the exact mechanism remains unclear, functional studies have demonstrated the effect of APOL1 and related protein on innate immunity and cytotoxicity.

SUMMARY

APOL1 is an important genetic risk factor for kidney disease among African-Americans. With approximately one in 10 African-Americans at risk, further studies are warranted to identify underlying biological mechanisms and other potential modifiers leading to CKD. Moreover, studies that clarify the association of APOL1 variants with cardiovascular disease, independent of CKD, are also needed.

Neighborhood perceptions and hypertension among low-income black women: a qualitative study

Background

The majority of studies examining the role of neighborhoods and hypertension-related outcomes have been quantitative in nature and very few studies have examined specific disadvantaged populations, including low-income housing residents. The objective of this study was to use qualitative interviews to explore low-income Black women’s perceptions of their neighborhoods and to understand how those perceptions may affect their health, especially as it relates to blood pressure.

Methods

Seventeen Black female participants, living in public housing communities in New York City, completed one semi-structured, audiotaped interview in July of 2014. All interviews were transcribed, coded, and analyzed for emerging themes using N’Vivo 10 software.

Results

Three major themes emerged: (1) social connectedness, (2) stress factors, and (3) availability of food options. For example, factors that caused stress varied throughout the study population. Sources of stress included family members, employment, and uncleanliness within the neighborhood. Many participants attributed their stress to personal issues, such as lack of employment and relationships. In addition, the general consensus among many participants was that there should be a greater density of healthy food options in their neighborhoods. Some believed that the pricing of fresh foods in the neighborhoods should better reflect the financial status of the residents in the community.

Conclusions

Various neighborhood influences, including neighborhood disorder and lack of healthy food options, are factors that appear to increase Black women’s risk of developing high blood pressure. Implications of this research include the need to develop interventions that promote good neighborhood infrastructure (e.g. healthy food stores to encourage good nutrition habits and well-lit walking paths to encourage daily exercise), in addition to interventions that increase hypertension awareness in low-income neighborhoods.