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

APOL1 Genotype and HIV Infection: 20-Year Outcomes for CKD, Cardiovascular Disease, and Hypertension

Introduction

APOL1 variant alleles substantially increase the risk for chronic kidney disease (CKD) in Black individuals, especially in the setting of HIV infection; however, their impact on hypertension and cardiovascular disease (CVD) is unclear.

Methods

Black persons with HIV (n = 1194) followed in the AIDS Clinical Trials Group (ACTG) observational studies A5001 and A5322 were genotyped for APOL1 risk alleles. Cox proportional hazard models were used to assess associations between APOL1 genotype and incident CKD, CVD, and hypertension, and linear mixed effects models were used to examine associations with longitudinal estimated glomerular filtration rate (eGFR) and proteinuria. Plasma HIV-1 viral suppression was evaluated as an effect modifier.

Results

APOL1 genotype was associated with CKD, but not with hypertension or CVD, although CVD events were infrequent in this relatively young cohort. Annual rates of eGFR decline and proteinuria were greater among persons with APOL1 risk alleles, including a detrimental effect of 1 APOL1 risk allele, which only became evident in the second decade of follow-up. Sustained HIV-1 viral suppression did not alter the association between incident CKD and APOL1 genotype; however, it was associated with a slower rate of eGFR decline and less proteinuria in participants with at least 1 APOL1 risk allele, including individuals with eGFRs above the CKD threshold throughout follow-up.

Conclusion

Among treated persons with HIV, APOL1 risk alleles were associated with CKD and eGFR decline, including an effect of 1 APOL1 risk allele which took longer to manifest and was greater in individuals who did not achieve sustained viral suppression. Conversely, no association between APOL1 risk alleles and incident hypertension or CVD was detected.

APOL1 Dynamics in Diabetic Kidney Disease and Hypertension

APOL1 Renal Risk Variants (APOL1RRVs, G1, and G2) are known to be toxic to glomerular podocytes and causally associated with an enhanced prevalence and progression of many different etiologies of chronic kidney disease (CKD), leading to the delineation of a new disease designation of APOL1-Mediated Kidney Disease (AMKD). Notably, APOL1RRVs have not consistently been shown to increase the prevalence or severity of diabetic kidney disease (DKD) progression, which is the most common cause of End-Stage Kidney Disease (ESKD). While this apparent discrepancy seems perplexing, its clarification should provide important mechanistic and therapeutic insights. Activation of the Renin-Angiotensin System (RAS) plays a critical role in the development and progression of DKD. Recent in vitro and in vivo studies also demonstrated that RAS activation contributes to kidney cell injury in AMKD experimental models. Both high glucose, as well as APOL1RRVs escalate the podocyte expression of miR193a, a known mediator of glomerulosclerosis, including idiopathic Focal Segmental Glomerular Sclerosis (FSGS) and DKD. We propose that either the RAS and/or miR193a levels in the diabetic milieu are already maximally conducive to kidney target cell injury and, therefore, are agnostic to further injury in response to APOL1RRVs. Similarly, the contributory role of hypertension (which is frequently reported as the second most common cause of ESKD) in the progression of AMKD remains a controversial issue. Since several clinical reports have shown that controlling hypertension does not consistently slow the progression of AMKD, this has led to a formulation wherein APOL1-RRVs primarily lead to kidney injury with accompanying hypertension. Notably, half a decade later, the notion that hypertension is not a cause but rather a consequence of kidney injury was contested by investigators analyzing the Mount Sinai BioMe repository, a comprehensive clinical and genetic database including participants with APOL1RRVs. These investigators observed that hypertension predated the observed decline in GFR in individuals with APOL1RRVs by ten years. In the present study, we discuss the mechanistic forces that may underpin the gaps in these clinical manifestations, which did not allow the temporal association of hypertension with AMKD to be translated into causation and may also dissociate DKD and AMKD. We have hypothesized models that need to be validated in future experimental studies.

Differing sensitivities to angiotensin converting enzyme inhibition of kidney disease mediated by APOL1 high-risk variants G1 and G2

Apolipoprotein L1 (APOL1) variants G1 and G2 contribute to the excess risk of kidney disease in individuals of recent African ancestry. Since disease mechanisms and optimal treatments remain controversial, we study the effect of current standard-of-care drugs in mouse models of APOL1 kidney disease. Experiments were performed in APOL1 BAC-transgenic mice, which develop proteinuria and glomerulosclerosis following injection with a pCpG-free IFN-γ plasmid. Proteinuric, plasmid injected G1/G1 and G2/G2 mice were randomized to drug treatment or no treatment. Lisinopril, dapagliflozin, and hydralazine were administered in drinking water starting day seven. The urine albumin/creatinine ratio was measured twice weekly, and the kidneys examined histologically with the focal segmental glomerulosclerosis score computed from periodic acid-Shiff-stained sections. The angiotensin converting enzyme inhibitor lisinopril, at standard dose, reduced proteinuria by approximately 90-fold and reduced glomerulosclerosis in the APOL1 G1/G1 BAC-transgenic mice. These effects were independent of blood pressure. Dapagliflozin did not alter disease progression in either G1/G1 or G2/G2 mice. Proteinuria reduction and glomerulosclerosis in G2/G2 BAC-transgenic mice required lisinopril doses two times higher than were effective in G1/G1 mice but achieved a much smaller benefit. Therefore, in these BAC-transgenic mouse models of APOL1 disease, the anti-proteinuric and anti-glomerulosclerotic effects of standard dose lisinopril were markedly effective in G1/G1 compared with G2/G2 APOL1 mice. Comparable reduction in blood pressure by hydralazine treatment provided no such protection. Neither G1/G1 nor G2/G2 mice showed improvement with the sodium-glucose cotransporter-2 inhibition dapagliflozin. Thus, it remains to be determined if similar differences in ACE inhibitor responsiveness are observed in patients.

Genome-Wide Approach of Gene-Nutrient Intake Interaction Study for Essential Hypertension in a Large Korean Cohort (KoGES)

Background/Objectives: There is limited evidence on gene-nutrient interaction associated with hypertension (HTN). We examined interactions between genotypes and various nutrients that influenced high blood pressure (BP). Methods: Data were obtained from a total of 50,808 participants from the Korean Genome and Epidemiology Study (KoGES). Dietary intake was assessed by a food frequency questionnaire, and dietary reference intakes (DRIs) were set. We performed genome-wide association analyses (GWAS) and subsequent interaction analyses with genome-wide significant SNPs to identify genomic loci that interact with specific nutrients associated with HTN. Results: We identified one locus near the CUB and Sushi Multiple Domains 1 (CSMD1) gene that showed interaction with dietary iron and vitamin B6 (Vit.B6) intake and significantly influenced HTN risk. Among the individuals consuming iron above DRI (9.5 mg/day for men, 9.25 mg/day for women), carriers of the rs13282715 minor allele (A) at 8p23.2 showed a lower risk of HTN than those who did not (odds ratio [OR] 0.723, 95% confidence interval [CI] (0.644-0.813), p-value 4.858 × 10-8; interaction p-value 1.336 × 10-3). Among the individuals consuming Vit.B6 above DRI (1.5 mg/day for men, 1.4 mg/day for women), carriers of the same variant rs13282715 minor allele (A) also showed a lower risk of HTN (OR 0.733, 95% CI 0.733 (0.656-0.819), p-value 4.121 × 10-8; interaction p-value 7.183 × 10-4). Conclusions: We identified a novel gene-nutrient interaction regarding dietary iron and Vit.B6 intake affecting the risk of HTN in Korean adults. This suggests individuals with the variant may benefit from lower HTN risk from dietary intervention of iron and Vit.B6 intake. Further studies with larger diverse populations are warranted to validate our findings.

APOL1 nephropathy - a population genetics success story

PURPOSE OF REVIEW

More than a decade ago, apolipoprotein L1 ( APOL1 ) risk alleles designated G1 and G2, were discovered to be causally associated with markedly increased risk for progressive kidney disease in individuals of recent African ancestry. Gratifying progress has been made during the intervening years, extending to the development and clinical testing of genomically precise small molecule therapy accompanied by emergence of RNA medicine platforms and clinical testing within just over a decade.

RECENT FINDINGS

Given the plethora of excellent prior review articles, we will focus on new findings regarding unresolved questions relating mechanism of cell injury with mode of inheritance, regulation and modulation of APOL1 activity, modifiers and triggers for APOL1 kidney risk penetrance, the pleiotropic spectrum of APOL1 related disease beyond the kidney - all within the context of relevance to therapeutic advances.

SUMMARY

Notwithstanding remaining controversies and uncertainties, promising genomically precise therapies targeted at APOL1 mRNA using antisense oligonucleotides (ASO), inhibitors of APOL1 expression, and small molecules that specifically bind and inhibit APOL1 cation flux are emerging, many already at the clinical trial stage. These therapies hold great promise for mitigating APOL1 kidney injury and possibly other systemic phenotypes as well. A challenge will be to develop guidelines for appropriate use in susceptible individuals who will derive the greatest benefit.

Multi-Institutional Implementation of Clinical Decision Support for APOL1, NAT2, and YEATS4 Genotyping in Antihypertensive Management

(1) Background: Clinical decision support (CDS) is a vitally important adjunct to the implementation of pharmacogenomic-guided prescribing in clinical practice. A novel CDS was sought for the APOL1, NAT2, and YEATS4 genes to guide optimal selection of antihypertensive medications among the African American population cared for at multiple participating institutions in a clinical trial. (2) Methods: The CDS committee, made up of clinical content and CDS experts, developed a framework and contributed to the creation of the CDS using the following guiding principles: 1. medical algorithm consensus; 2. actionability; 3. context-sensitive triggers; 4. workflow integration; 5. feasibility; 6. interpretability; 7. portability; and 8. discrete reporting of lab results. (3) Results: Utilizing the principle of discrete patient laboratory and vital information, a novel CDS for APOL1, NAT2, and YEATS4 was created for use in a multi-institutional trial based on a medical algorithm consensus. The alerts are actionable and easily interpretable, clearly displaying the purpose and recommendations with pertinent laboratory results, vitals and links to ordersets with suggested antihypertensive dosages. Alerts were either triggered immediately once a provider starts to order relevant antihypertensive agents or strategically placed in workflow-appropriate general CDS sections in the electronic health record (EHR). Detailed implementation instructions were shared across institutions to achieve maximum portability. (4) Conclusions: Using sound principles, the created genetic algorithms were applied across multiple institutions. The framework outlined in this study should apply to other disease-gene and pharmacogenomic projects employing CDS.

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.

Association of West African ancestry and blood pressure control among African Americans taking antihypertensive medication in the Jackson Heart Study

African Americans have a wide range of continental genetic ancestry. It is unclear whether racial differences in blood pressure (BP) control are related to ancestral background. The authors analyzed data from the Jackson Heart Study, a cohort exclusively comprised of self-identified African Americans, to assess the association between estimated West African ancestry (WAA) and BP control (systolic and diastolic BP < 140/90 mm Hg). Three nested modified Poisson regression models were used to calculate prevalence ratios for BP control associated with the three upper quartiles, separately, vs the lowest quartile of West African ancestry. The authors analyzed data from 1658 participants with hypertension who reported taking all of their antihypertensive medications in the previous 24 hours. WAA was estimated using 389 ancestry informative markers and categorized into quartiles (Q1: <73.7%, Q2: >73.7%-81.0%, Q3: >81.0%-86.3%, and Q4: >86.3%). The proportion of participants with controlled BP in the lowest-to-highest WAA quartile was 75.2%, 76.1%, 76.6%, and 74.4%. The prevalence ratios (95% CI) for controlled BP comparing Q2, Q3, and Q4 to Q1 of WAA were 1.00 (0.93-1.08), 1.02 (0.94-1.10), and 0.99 (0.91-1.07), respectively. Among African Americans in the Jackson Heart Study taking antihypertensive medication, BP control rates did not differ across quartiles of WAA.