A pharmacogenetic investigation of intravenous furosemide in decompensated heart failure: a meta-analysis of three clinical trials

Contribution of Uptake and Efflux Transporters to Oral Pharmacokinetics of Furosemide

Furosemide is a widely used diuretic for treating excessive fluid accumulation caused by disease conditions like heart failure and liver cirrhosis. Furosemide tablet formulation exhibits variable pharmacokinetics (PK) with bioavailability ranging from 10 to almost 100%. To explain the variable absorption, we integrated the physicochemical, in vitro dissolution, permeability, distribution, and the elimination parameters of furosemide in a physiologically-based pharmacokinetic (PBPK) model. Although the intravenous PBPK model reasonably described the observed in vivo PK data, the reported low passive permeability failed to capture the observed data after oral administration. To mechanistically justify this discrepancy, we hypothesized that transporter-mediated uptake contributes to the oral absorption of furosemide in conjunction with passive permeability. Our in vitro results confirmed that furosemide is a substrate of intestinal breast cancer resistance protein (BCRP), multidrug resistance-associated protein 4 (MRP4), and organic anion transporting polypeptide 2B1 (OATP2B1), but it is not a substrate of P-glycoprotein (P-gp) and MRP2. We then estimated the net transporter-mediated intestinal uptake and integrated it into the PBPK model under both fasting and fed conditions. Our in vitro data and PBPK model suggest that the absorption of furosemide is permeability-limited, and OATP2B1 and MRP4 are important for its permeability across intestinal membrane. Further, as furosemide has been proposed as a probe substrate of renal organic anion transporters (OATs) for assessing clinical drug-drug interactions (DDIs) during drug development, the confounding effects of intestinal transporters identified in this study on furosemide PK should be considered in the clinical transporter DDI studies.

Vascular homeostasis at high-altitude: role of genetic variants and transcription factors

High-altitude pulmonary edema occurs most frequently in non-acclimatized low landers on exposure to altitude ≥2500 m. High-altitude pulmonary edema is a complex condition that involves perturbation of signaling pathways in vasoconstrictors, vasodilators, anti-diuretics, and vascular growth factors. Genetic variations are instrumental in regulating these pathways and evidence is accumulating for a role of epigenetic modification in hypoxic responses. This review focuses on the crosstalk between high-altitude pulmonary edema-associated genetic variants and transcription factors, comparing high-altitude adapted and high-altitude pulmonary edema-afflicted subjects. This approach might ultimately yield biomarker information both to understand and to design therapies for high-altitude adaptation.

A genetic association study of heart failure: more evidence for the role of BAG3 in idiopathic dilated cardiomyopathy

Aims

Few investigations have been conducted to identify genetic determinants of common, polygenetic forms of heart failure (HF), and only a limited number of these genetic associations have been validated by multiple groups.

Methods and results

We performed a case–control study to further investigate the potential impact of 14 previously reported candidate genes on the risk of HF and specific HF sub‐types. We also performed an exploratory genome‐wide study. We included 799 patients with HF and 1529 controls. After adjusting for age, sex, and genetic ancestry, we found that the C allele of rs2234962 in BAG3 was associated with a decreased risk of idiopathic dilated cardiomyopathy (odds ratio 0.42, 95% confidence interval 0.25–0.68, P = 0.0005), consistent with a previous report. No association for the other primary variants or exploratory genome‐wide study was found.

Conclusions

Our findings provide independent replication for the association between a common coding variant (rs2234962) in BAG3 and the risk of idiopathic dilated cardiomyopathy.

Obese-Inflammatory Phenotypes in Heart Failure With Preserved Ejection Fraction

BACKGROUND

Comorbidity-driven microvascular inflammation is posited as a unifying pathophysiologic mechanism for heart failure with preserved ejection fraction (HFpEF). Obesity is proinflammatory and common in HFpEF. We hypothesized that unique obesity-inflammation HFpEF phenotypes exist and are associated with differences in clinical features, fibrosis biomarkers, and functional performance.

METHODS

Patients (n=301) from 3 HFpEF clinical trials were studied. Unsupervised machine learning (hierarchical clustering) with obese status and 13 inflammatory biomarkers as input variables was performed. Associations of clusters with HFpEF severity and fibrosis biomarkers (PIIINP [procollagen III N-terminal peptide], CITP [C-telopeptide for type I collagen], IGFBP7 [insulin-like growth factor-binding protein-7], and GAL-3 [galectin-3]) were assessed.

RESULTS

Hierarchical clustering revealed 3 phenotypes: pan-inflammatory (n=129; 64% obese), noninflammatory (n=83; 55% obese), and obese high CRP (C-reactive protein; n=89; 98% obese). The pan-inflammatory phenotype had more comorbidities and heart failure hospitalizations; higher left atrial volume, NT-proBNP (N-terminal pro-B-type natriuretic peptide), and fibrosis biomarkers; and lower glomerular filtration rate, peak oxygen consumption, 6-minute walk distance, and active hours/day (P<0.05 for all). The noninflammatory phenotype had the most favorable values for all measures. The obese high CRP phenotype resembled the noninflammatory phenotype except for isolated elevation of CRP and lower functional performance. Hierarchical cluster assignment was independent of CRP genotype combinations that alter CRP levels and more biologically plausible than other clustering approaches. Multiple traditional analytic techniques confirmed and extended the hierarchical clustering findings.

CONCLUSIONS

Unique obesity-inflammation phenotypes exist in HFpEF and are associated with differences in comorbidity burden, HFpEF severity, and fibrosis. These data support comorbidity-driven microvascular inflammation as a pathophysiologic mechanism for many but not all HFpEF patients.

Association of APOL1 With Heart Failure With Preserved Ejection Fraction in Postmenopausal African American Women

Importance

APOL1 genotypes are associated with kidney diseases in African American individuals and may influence cardiovascular disease and mortality risk, but findings have been inconsistent.

Objective

To discern whether high-risk APOL1 genotypes are associated with cardiovascular disease and stroke in postmenopausal African American women, who are at high risk for these outcomes.

Design, Setting, and Participants

The Women's Health Initiative is a prospective cohort that enrolled 161 838 postmenopausal women into clinical trials and an observational study between 1993 and 1998. This study includes 11 137 African American women participants who had a clinical event from enrollment to June 2014. Data analyses were completed from January 2017 to August 2017.

Exposures

The variants of APOL1 were genotyped or imputed from whole-exome sequencing.

Main Outcomes and Measures

Incident coronary heart disease, stroke and heart failure subtypes, and overall and cause-specific mortality were adjudicated from hospital records and death certificates. Estimated incidence rates were determined for each outcome and hazard ratios (HR) and 95% CIs for the associations of APOL1 groups with outcomes.

Results

The mean (SD) age of participants was 61.7 (7.1) years. Carriers of high-risk APOL1 variants (n = 1370; 12.3%) had higher prevalence of hypertension, use of cholesterol-lowering medications, and reduced estimated glomerular filtration rate (eGFR). After a mean (SD) of 11.0 (3.6) years, carriers of high-risk APOL1 variants had a higher incidence rate of hospitalized heart failure with preserved ejection fraction (HFpEF) than low-risk carriers did but showed no differences for other outcomes. In adjusted models, there was a significant 58% increased hazard of hospitalized HFpEF (HR, 1.58 [95% CI, 1.03-2.41]) among carriers of high-risk APOL1 variants compared with carriers of low-risk APOL1 variants. The association with HFpEF was attenuated (HR = 1.50 [95% CI, 0.98-2.30]) and no longer significant when adjusting for baseline eGFR.

Conclusions and Relevance

Status as a carrier of a high-risk APOL1 genotype was associated with HFpEF hospitalization among postmenopausal women, which is partly accounted for by baseline kidney function. These findings do not support an association of high-risk APOL1 genotypes with coronary heart disease, stroke, or mortality in postmenopausal African American women.

Multidrug resistance-associated protein 4 in pharmacology: Overview of its contribution to pharmacokinetics, pharmacodynamics and pharmacogenetics

MRP4 is an ABC membrane transporter involved in clinical outcomes as it is located in many tissues that manages the transport and the elimination of many drugs. This review explores the implication of MRP4 in clinical pharmacology and the importance of its genetic variability. Although there is no specific recommendation regarding the study of MRP4 in drug development, it should be considered when drugs are eliminated by the kidney or liver or when drug-drug interactions are expected.

Furosemide Exposure and Prevention of Bronchopulmonary Dysplasia in Premature Infants

OBJECTIVE

To evaluate the association between furosemide exposure and risk of bronchopulmonary dysplasia (BPD).

STUDY DESIGN

This retrospective cohort study included infants (2004-2015) born at 23-29 weeks gestational age and 501-1249 g birth weight. We compared the demographic and clinical characteristics of infants exposed and not exposed to furosemide between postnatal day 7 and 36 weeks postmenstrual age. We examined the association between furosemide exposure and 2 outcomes: BPD and BPD or death. We performed multivariable probit regression models that included demographic and clinical variables in addition to 2 instrumental variables: furosemide exposure by discharge year, and furosemide exposure by site.

RESULTS

Of 37 693 included infants, 19 235 (51%) were exposed to furosemide; these infants were more premature and had higher respiratory support. Of 33 760 infants who survived to BPD evaluation, 15 954 (47%) had BPD. An increase in the proportion of furosemide exposure days by 10 percentage points was associated with a decrease in both the incidence of BPD (4.6 percentage points; P = .001), and BPD or death (3.7 percentage points; P = .01).

CONCLUSIONS

More days of furosemide exposure between postnatal day 7 and 36 weeks was associated with decreased risk of BPD and a combined outcome of BPD or death.

Diuretic Resistance in Heart Failure

PURPOSE OF REVIEW

Diuretic resistance (DR) occurs along a spectrum of relative severity and contributes to worsening of acute heart failure (AHF) during an inpatient stay. This review gives an overview of mechanisms of DR with a focus on loop diuretics and summarizes the current literature regarding the prognostic value of diuretic efficiency and predictors of natriuretic response in AHF.

RECENT FINDINGS

The pharmacokinetics of diuretics are impaired in chronic heart failure, but little is known about mechanisms of DR in AHF. Almost all diuresis after administration of a loop diuretic dose occurs in the first few hours after administration and within-dose DR can develop. Recent studies suggest that DR at the level of the nephron may be more important than defects in diuretic delivery to the tubule. Because loop diuretics induce natriuresis, urine sodium (UNa) concentration may serve as a functional, physiological, and direct measure for diuretic responsiveness to a given loop diuretic dose. Identifying and targeting individuals with DR for more aggressive, tailored therapy represents an important opportunity to improve outcomes. A better understanding of the mechanistic underpinnings of DR in AHF is needed to identify additional biomarkers and guide future trials and therapies.

CYP3A4 genotype is associated with sildenafil concentrations in patients with heart failure with preserved ejection fraction

Despite its established inter-individual variability, sildenafil has been the subject of only a few pharmacogenetic investigations, with limited data regarding the genetic modulators of its pharmacokinetics. We conducted a pharmacogenetic sub-study of patients randomized to sildenafil (n=85) in the RELAX trial, which investigated the impact of high-dose sildenafil in patients with heart failure with preserved left ventricular ejection fraction (HFpEF). In the overall population, the CYP3A4 inferred phenotype appeared associated with the dose-adjusted peak concentrations of sildenafil at week 12 and week 24 (adjusted P=0.045 for repeated measures analysis), although this P-value did not meet our corrected significance threshold of 0.0167. In the more homogeneous Caucasian subgroup, this association was significant (adjusted P=0.0165 for repeated measures). Hence, CYP3A4 inferred phenotype is associated with peak sildenafil dose-adjusted concentrations in patients with HFpEF receiving high doses of sildenafil. The clinical impact of this association requires further investigation.

Association Between APOL1 Genotypes and Risk of Cardiovascular Disease in MESA (Multi-Ethnic Study of Atherosclerosis)

Background

APOL1 genetic variants confer an increased risk for kidney disease. Their associations with cardiovascular disease (CVD) are less certain. We aimed to compare the prevalence of subclinical CVD and incidence of atherosclerotic CVD and heart failure by APOL1 genotypes among self‐identified black participants of MESA (Multi‐Ethnic Study of Atherosclerosis).

Methods and Results

Cross‐sectional associations of APOL1 genotypes (high‐risk=2 alleles; low‐risk=0 or 1 allele) with coronary artery calcification, carotid‐intimal media thickness, and left ventricular mass were evaluated using logistic and linear regression. Longitudinal associations of APOL1 genotypes with incident myocardial infarction, stroke, coronary heart disease, and congestive heart failure were examined using Cox regression. We adjusted for African ancestry, age, and sex. We also evaluated whether hypertension or kidney function markers explained the observed associations. Among 1746 participants with APOL1 genotyping (mean age 62 years, 55% women, mean cystatin C–based estimated glomerular filtration rate 89 mL/min per 1.73 m², 12% with albuminuria), 12% had the high‐risk genotypes. We found no difference in prevalence or severity of coronary artery calcification, carotid‐intimal media thickness, or left ventricular mass by APOL1 genotypes. The APOL1 high‐risk group was 82% more likely to develop incident heart failure compared with the low‐risk group (95% confidence interval, 1.01–3.28). Adjusting for hypertension (hazard ratio, 1.80; 95% confidence interval, 1.00–3.24) but not markers of kidney function (hazard ratio, 1.86; 95% confidence interval, 1.03–3.35) slightly attenuated this association. The APOL1 high‐risk genotypes were not significantly associated with other clinical CVD outcomes.

Conclusions

Among blacks without baseline CVD, the APOL1 high‐risk variants may be associated with increased risk for incident heart failure but not subclinical CVD or incident clinical atherosclerotic CVD.

Practical Pharmacogenomic Approaches to Heart Failure Therapeutics

OPINION STATEMENT

The major challenge in applying pharmacogenomics to everyday clinical practice in heart failure (HF) is based on (1) a lack of robust clinical evidence for the differential utilization of neurohormonal antagonists in the management of HF in different subgroups, (2) inconsistent results regarding appropriate subgroups that may potentially benefit from an alternative strategy based on pharmacogenomic analyses, and (3) a lack of clinical trials that focused on testing gene-guided treatment in HF. To date, all pharmacogenomic analyses in HF have been conducted as post hoc retrospective analyses of clinical trial data or of observational patient series studies. This is in direct contrast with the guideline-directed HF therapies that have demonstrated their safety and efficacy in the absence of pharmacogenomic guidance. Therefore, the future of clinical applications of pharmacogenomic testing will largely depend on our ability to incorporate gene-drug interactions into the prescribing process, requiring that preemptive and cost-effective testing be paired with decision-support tools in a value-based care approach.