Medical Therapy Before, During and After Hospitalization in Medicare Beneficiaries With Heart Failure and Diabetes: Get With The Guidelines - Heart Failure Registry.

BACKGROUND: Patients hospitalized with heart failure (HF) and diabetes mellitus (DM) are at risk for worsening clinical status. Little is known about the frequency of therapeutic changes during hospitalization. We characterized the use of medical therapies before, during and after hospitalization in patients with HF and DM. METHODS: We identified Medicare beneficiaries in Get With The Guidelines-Heart Failure (GWTG-HF) hospitalized between July 2014 and September 2019 with Part D prescription coverage. We evaluated trends in the use of 7 classes of antihyperglycemic therapies (metformin, sulfonylureas, GLP-1RA, SGLT2-inhibitors, DPP-4 inhibitors, thiazolidinediones, and insulins) and 4 classes of HF therapies (evidence-based ß-blockers, ACEi or ARB, MRA, and ARNI). Medication fills were assessed at 6 and 3 months before hospitalization, at hospital discharge and at 3 months post-discharge. RESULTS: Among 35,165 Medicare beneficiaries, the median age was 77 years, 54% were women, and 76% were white; 11,660 (33%) had HFrEF (LVEF ≤ 40%), 3700 (11%) had HFmrEF (LVEF 41%-49%), and 19,805 (56%) had HFpEF (LVEF ≥ 50%). Overall, insulin was the most commonly prescribed antihyperglycemic after HF hospitalization (n = 12,919, 37%), followed by metformin (n = 7460, 21%) and sulfonylureas (n = 7030, 20%). GLP-1RA (n = 700, 2.0%) and SGLT2i (n = 287, 1.0%) use was low and did not improve over time. In patients with HFrEF, evidence-based beta-blocker, RASi, MRA, and ARNI fills during the 6 months preceding HF hospitalization were 63%, 62%, 19%, and 4%, respectively. Fills initially declined prior to hospitalization, but then rose from 3 months before hospitalization to discharge (beta-blocker: 56%-82%; RASi: 51%-57%, MRA: 15%-28%, ARNI: 3%-6%, triple therapy: 8%-20%; P < 0.01 for all). Prescription rates 3 months after hospitalization were similar to those at hospital discharge. CONCLUSIONS: In-hospital optimization of medical therapy in patients with HF and DM is common in participating hospitals of a large US quality improvement registry.

Dapagliflozin vs. metolazone in heart failure resistant to loop diuretics.

BACKGROUND AND AIMS: To examine the decongestive effect of the sodium-glucose cotransporter 2 inhibitor dapagliflozin compared to the thiazide-like diuretic metolazone in patients hospitalized for heart failure and resistant to treatment with intravenous furosemide. METHODS AND RESULTS: A multi-centre, open-label, randomized, and active-comparator trial. Patients were randomized to dapagliflozin 10 mg once daily or metolazone 5-10 mg once daily for a 3-day treatment period, with follow-up for primary and secondary endpoints until day 5 (96 h). The primary endpoint was a diuretic effect, assessed by change in weight (kg). Secondary endpoints included a change in pulmonary congestion (lung ultrasound), loop diuretic efficiency (weight change per 40 mg of furosemide), and a volume assessment score. 61 patients were randomized. The mean (±standard deviation) cumulative dose of furosemide at 96 h was 977 (±492) mg in the dapagliflozin group and 704 (±428) mg in patients assigned to metolazone. The mean (±standard deviation) decrease in weight at 96 h was 3.0 (2.5) kg with dapagliflozin compared to 3.6 (2.0) kg with metolazone [mean difference 0.65, 95% confidence interval (CI) -0.12,1.41 kg; P = 0.11]. Loop diuretic efficiency was less with dapagliflozin than with metolazone [mean 0.15 (0.12) vs. 0.25 (0.19); difference -0.08, 95% CI -0.17,0.01 kg; P = 0.10]. Changes in pulmonary congestion and volume assessment score were similar between treatments. Decreases in plasma sodium and potassium and increases in urea and creatinine were smaller with dapagliflozin than with metolazone. Serious adverse events were similar between treatments. CONCLUSION: In patients with heart failure and loop diuretic resistance, dapagliflozin was not more effective at relieving congestion than metolazone. Patients assigned to dapagliflozin received a larger cumulative dose of furosemide but experienced less biochemical upset than those assigned to metolazone. TRIAL REGISTRATION: ClinicalTrials.gov Identifier: NCT04860011.

Projected Clinical Benefits of Implementation of SGLT-2 Inhibitors Among Medicare Beneficiaries Hospitalized for Heart Failure.

BACKGROUND: The sodium-glucose cotransporter-2 (SGLT-2) inhibitors form the latest pillar in the management of heart failure with reduced ejection fraction (HFrEF) and appear to be effective across a range of patient profiles. There is increasing interest in initiating SGLT-2 inhibitors during hospitalization, yet little is known about the putative benefits of this implementation strategy. METHODS: We evaluated Medicare beneficiaries with HFrEF (≤ 40%) hospitalized at 228 sites in the Get With The Guidelines-Heart Failure (GWTG-HF) registry in 2016 who had linked claims data for ≥ 1 year postdischarge. We identified those eligible for dapagliflozin under the latest U.S. Food and Drug Administration label (excluding estimated glomerular filtration rates < 25 mL/min per 1.73 m2, dialysis and type 1 diabetes). We evaluated 1-year outcomes overall and among key subgroups (age ≥ 75 years, gender, race, hospital region, kidney function, diabetes status, triple therapy). We then projected the potential benefits of implementation of dapagliflozin based on the risk reductions observed in the Dapagliflozin and Prevention of Adverse Outcomes in Heart Failure (DAPA-HF) trial. RESULTS: Among 7523 patients hospitalized for HFrEF, 6576 (87%) would be candidates for dapagliflozin (mean age 79 ± 8 years, 39% women, 11% Black). Among eligible candidates, discharge use of ß-blockers, ACEi/ARB, MRA, ARNI, and triple therapy (ACEi/ARB/ARNI+ß-blocker+MRA) was recorded in 88%, 64%, 29%, 3%, and 20%, respectively. Among treatment-eligible patients, the 1-year incidence (95% CI) of mortality was 37% (36-38%) and of HF readmission was 33% (32-34%), and each exceeded 25% across all key subgroups. Among 1333 beneficiaries eligible for dapagliflozin who were already on triple therapy, the 1-year incidence of mortality was 26% (24%-29%) and the 1-year readmission due to HF was 30% (27%-32%). Applying the relative risk reductions observed in DAPA-HF, absolute risk reductions with complete implementation of dapagliflozin among treatment-eligible Medicare beneficiaries are projected to be 5% (1%-9%) for mortality and 9% (5%-12%) for HF readmission by 1 year. The projected number of Medicare beneficiaries who would need to be treated for 1 year to prevent 1 death is 19 (11-114), and 12 (8-21) would need to be treated to prevent 1 readmission due to HF. CONCLUSIONS: Medicare beneficiaries with HFrEF who are eligible for dapagliflozin after hospitalization due to HF, including those well-treated with other disease-modifying therapies, face high risks of mortality and HF readmission by 1 year. If the benefits of reductions in death and hospitalizations due to HF observed in clinical trials can be fully realized, the absolute benefits of implementation of SGLT-2 inhibitors among treatment-eligible candidates are anticipated to be substantial in this high-risk postdischarge setting.

Ribonucleoprotein Capture by in Vivo Expression of a Designer Pentatricopeptide Repeat Protein in Arabidopsis.

Pentatricopeptide repeat (PPR) proteins bind RNA via a mechanism that facilitates the customization of sequence specificity. However, natural PPR proteins have irregular features that limit the degree to which their specificity can be predicted and customized. We demonstrate here that artificial PPR proteins built from consensus PPR motifs selectively bind the intended RNA in vivo, and we use this property to develop a new tool for ribonucleoprotein characterization. We show by RNA coimmunoprecipitation sequencing (RIP-seq) that artificial PPR proteins designed to bind the Arabidopsis (Arabidopsis thaliana) chloroplast psbA mRNA bind with high specificity to psbA mRNA in vivo. Analysis of coimmunoprecipitating proteins by mass spectrometry showed the psbA translational activator HCF173 and two RNA binding proteins of unknown function (CP33C and SRRP1) to be highly enriched. RIP-seq revealed that these proteins are bound primarily to psbA RNA in vivo, and precise mapping of the HCF173 and CP33C binding sites placed them in different locations on psbA mRNA. These results demonstrate that artificial PPR proteins can be tailored to bind specific endogenous RNAs in vivo, add to the toolkit for characterizing native ribonucleoproteins, and open the door to other applications that rely on the ability to target a protein to a specified RNA sequence.

Wash-Free, Digital Immunoassay in Polydisperse Droplets.

Immunoassays are important for the detection of proteins to enable disease identification and monitor treatment, but many immunoassays suffer from sensitivity limitations. The development of digital assays has enabled highly sensitive biomarker detection and quantification, but the necessary devices typically require precisely controlled volumes to reduce biases in concentration estimates from compartment size variation. These constraints have led to systems that are often expensive, cumbersome, and challenging to operate, confining many digital assays to centralized laboratories. To overcome these limitations, we have developed a simplified digital immunoassay performed in polydisperse droplets that are prepared without any specialized equipment. This polydisperse digital droplet immunoassay (ddIA) uses proximity ligation to remove the need for wash steps and simplifies the system to a single reagent addition step. Using interleukin-8 (IL-8) as an example analyte, we demonstrated the concept with samples in buffer and diluted whole blood with limits of detection of 0.793 pM and 1.54 pM, respectively. The development of a one-pot, washless assay greatly improves usability compared to traditional immunoassays or digital-based systems that rely heavily on wash steps and can be run with common and readily available laboratory equipment such as a heater and simple fluorescent microscope. We also developed a stochastic model with physically meaningful parameters that can be utilized to optimize the assay and enable quantification without standard curves, after initial characterization of the parameters. Our polydisperse ddIA assay serves as an example of sensitive, lower-cost, and simpler immunoassays suitable for both laboratory and point-of-care applications.

RNA-binding specificity landscapes of designer pentatricopeptide repeat proteins elucidate principles of PPR-RNA interactions.

Pentatricopeptide repeat (PPR) proteins are helical-repeat proteins that offer a promising scaffold for the engineering of proteins to bind specified RNAs. PPR tracts bind RNA in a modular 1-repeat, 1-nucleotide fashion. An amino acid code specifying the bound nucleotide has been elucidated. However, this code does not fully explain the sequence specificity of native PPR proteins. Furthermore, it does not address nuances such as the contribution toward binding affinity of various repeat-nucleotide pairs or the impact of mismatches between a repeat and aligning nucleotide. We used an in vitro bind-n-seq approach to describe the population of sequences bound by four artificial PPR proteins built from consensus scaffolds. The specificity of these proteins can be accounted for by canonical code-based nucleotide recognition. The results show, however, that interactions near the 3'-end of binding sites make less contribution to binding affinity than do those near the 5'-end, that proteins with 11 and 14 repeats exhibit similar affinity for their intended targets but 14-repeats are more permissive for mismatches, and that purine-binding repeats are less tolerant of transversion mismatches than are pyrimidine-binding motifs. These findings have implications for mechanisms that establish PPR-RNA interactions and for optimizing PPR design to minimize off-target interactions.

Kidney Outcomes Among Medicare Beneficiaries After Hospitalization for Heart Failure.

Importance: Kidney health has received increasing focus as part of comprehensive heart failure (HF) treatment efforts. However, the occurrence of clinically relevant kidney outcomes in contemporary populations with HF has not been well studied. Objective: To examine rates of incident dialysis and acute kidney injury (AKI) among Medicare beneficiaries after HF hospitalization. Design, Setting, and Participants: This retrospective cohort study evaluated adults aged 65 years or older who were hospitalized for HF across 372 sites in the Get With The Guidelines-Heart Failure registry in the US between January 1, 2014, and December 31, 2018. Patients younger than 65 years or requiring dialysis either during or prior to hospitalization were excluded. Data were analyzed from May 4, 2021, to March 8, 2024. Main Outcomes and Measures: The primary outcome was inpatient dialysis initiation in the year after HF hospitalization and was ascertained via linkage with Medicare claims data. Other all-cause and cause-specific hospitalizations were also evaluated. The covariate-adjusted association between discharge estimated glomerular filtration rate (eGFR) and 1-year postdischarge outcomes was examined using Cox proportional hazards regression models. Results: Overall, among 85 298 patients included in the analysis (mean [SD] age, 80 [9] years; 53% women) mean (SD) left ventricular ejection fraction was 47% (16%) and mean (SD) eGFR was 53 (29) mL/min per 1.73 m2; 54 010 (63%) had an eGFR less than 60 mL/min per 1.73 m2. By 1 year after HF hospitalization, 6% had progressed to dialysis, 7% had progressed to dialysis or end-stage kidney disease, and 7% had been readmitted for AKI. Incident dialysis increased steeply with lower discharge eGFR category: compared with patients with an eGFR of 60 mL/min per 1.73 m2 or more, individuals with an eGFR of 45 to less than 60 and of less than 30 mL/min per 1.73 m2 had higher rates of dialysis readmission (45 to <60: adjusted hazard ratio [AHR], 2.16 [95% CI, 1.86-2.51]; <30: AHR, 28.46 [95% CI, 25.25-32.08]). Lower discharge eGFR (per 10 mL/min per 1.73 m2 decrease) was independently associated with a higher rate of readmission for dialysis (AHR, 2.23; 95% CI, 2.14-2.32), dialysis or end-stage kidney disease (AHR, 2.34; 95% CI, 2.24-2.44), and AKI (AHR, 1.25; 95% CI, 1.23-1.27), with similar findings for all-cause mortality, all-cause readmission, and HF readmission. Baseline left ventricular ejection fraction did not modify the covariate-adjusted association between lower discharge eGFR and kidney outcomes. Conclusions and Relevance: In this study, older adults with HF had substantial risk of kidney complications, with an estimated 6% progressing to dialysis in the year after HF hospitalization. These findings emphasize the need for health care approaches prioritizing kidney health in this high-risk population.

Cause-Specific Health Care Costs Following Hospitalization for Heart Failure and Cost Offset With SGLT2i Therapy.

BACKGROUND: Little is known regarding differences in cause-specific costs between heart failure (HF) with ejection fraction (EF) ≤40% vs >40%, and potential cost implications of sodium glucose co-transporter 2 inhibitor (SGLT2i) therapy. OBJECTIVES: This study sought to compare cause-specific health care costs following hospitalization for HF with EF ≤40% vs >40% and estimate the cost offset with implementation of SGLT2i therapy. METHODS: This study examined Medicare beneficiaries hospitalized for HF in the Get With The Guidelines-Heart Failure registry from 2016 to 2020. Mean per-patient total (excluding drug costs) and cause-specific costs from discharge through 1-year follow-up were calculated and compared between EF ≤40% vs >40%. Next, risk reductions on total all-cause and HF hospitalizations were estimated in a trial-level meta-analysis of 5 pivotal trials of SGLT2is in HF. Finally, these relative treatment effects were applied to Medicare beneficiaries eligible for SGLT2i therapy to estimate the projected cost offset with implementation of SGLT2i, excluding drug costs. RESULTS: Among 146,003 patients, 50,598 (34.7%) had EF ≤40% and 95,405 (65.3%) had EF >40%. Mean total cost through 1 year was $40,557. Total costs were similar between EF groups overall but were higher for EF ≤40% among patients surviving the 1-year follow-up period. Patients with EF >40% had higher costs caused by non-HF and noncardiovascular hospitalizations, and skilled nursing facilities (all P < 0.001). Trial-level meta-analysis of the 5 SGLT2i clinical trials estimated 11% (rate ratio: 0.89; 95% CI: 0.84-0.93; P < 0.001) and 29% (rate ratio: 0.71; 95% CI: 0.66-0.76; P < 0.001) relative reductions in rates of total all-cause and HF hospitalizations, respectively, regardless of EF. Reductions in all-cause and HF hospitalizations were projected to reduce annual costs of readmission by $2,451 to $2,668 per patient with EF ≤40% and $1,439 to $2,410 per patient with EF >40%. CONCLUSIONS: In this large cohort of older U.S. adults hospitalized for HF, cause-specific costs of care differed among patients with EF ≤40% vs >40%. SGLT2i significantly reduced the rate of HF and all-cause hospitalizations irrespective of EF in clinical trials, and implementation of SGLT2i therapy in clinical practice is projected to reduce costs by $1,439 to $2,668 per patient over the 1 year post-discharge, excluding drug costs.

Contemporary Use of Sodium-Glucose Cotransporter-2 Inhibitor Therapy Among Patients Hospitalized for Heart Failure With Reduced Ejection Fraction in the US: The Get With The Guidelines-Heart Failure Registry.

Importance: Clinical guidelines for patients with heart failure with reduced ejection fraction (HFrEF) strongly recommend treatment with a sodium-glucose cotransporter-2 inhibitor (SGLT2i) to reduce cardiovascular mortality or HF hospitalization. Nationwide adoption of SGLT2i for HFrEF in the US is unknown. Objective: To characterize patterns of SGLT2i use among eligible US patients hospitalized for HFrEF. Design, Setting, and Participants: This retrospective cohort study analyzed 49 399 patients hospitalized for HFrEF across 489 sites in the Get With The Guidelines-Heart Failure (GWTG-HF) registry between July 1, 2021, and June 30, 2022. Patients with an estimated glomerular filtration rate less than 20 mL/min/1.73 m2, type 1 diabetes, and previous intolerance to SGLT2i were excluded. Main Outcomes and Measures: Patient-level and hospital-level prescription of SGLT2i at hospital discharge. Results: Of 49 399 included patients, 16 548 (33.5%) were female, and the median (IQR) age was 67 (56-78) years. Overall, 9988 patients (20.2%) were prescribed an SGLT2i. SGLT2i prescription was less likely among patients with chronic kidney disease (CKD; 4550 of 24 437 [18.6%] vs 5438 of 24 962 [21.8%]; P < .001) but more likely among patients with type 2 diabetes (T2D; 5721 of 21 830 [26.2%] vs 4262 of 27 545 [15.5%]; P < .001) and those with both T2D and CKD (2905 of 12 236 [23.7%] vs 7078 vs 37 139 [19.1%]; P < .001). Patients prescribed SGLT2i therapy were more likely to be prescribed background triple therapy with an angiotensin-converting enzyme inhibitor/angiotensin receptor blocker/angiotensin receptor-neprilysin inhibitor, ß-blocker, and mineralocorticoid receptor antagonist (4624 of 9988 [46.3%] vs 10 880 of 39 411 [27.6%]; P < .001), and 4624 of 49 399 total study patients (9.4%) were discharged with prescriptions for quadruple medical therapy including SGLT2i. Among 461 hospitals with 10 or more eligible discharges, 19 hospitals (4.1%) discharged 50% or more of patients with prescriptions for SGLT2i, whereas 344 hospitals (74.6%) discharged less than 25% of patients with prescriptions for SGLT2i (including 29 [6.3%] that discharged zero patients with SGLT2i prescriptions). There was high between-hospital variance in the rate of SGLT2i prescription in unadjusted models (median odds ratio, 2.53; 95% CI, 2.36-2.74) and after adjustment for patient and hospital characteristics (median odds ratio, 2.51; 95% CI, 2.34-2.71). Conclusions and Relevance: In this study, prescription of SGLT2i at hospital discharge among eligible patients with HFrEF was low, including among patients with comorbid CKD and T2D who have multiple indications for therapy, with substantial variation among US hospitals. Further efforts are needed to overcome implementation barriers and improve use of SGLT2i among patients with HFrEF.

Kidney Function and Outcomes in Patients Hospitalized With Heart Failure.

BACKGROUND: Few contemporary data exist evaluating care patterns and outcomes in heart failure (HF) across the spectrum of kidney function. OBJECTIVES: This study sought to characterize differences in quality of care and outcomes in patients hospitalized for HF by degree of kidney dysfunction. METHODS: Guideline-directed medical therapies were evaluated among patients hospitalized with HF at 418 sites in the GWTG-HF (Get With The Guidelines-Heart Failure) registry from 2014 to 2019 by discharge CKD-EPI (Chronic Kidney Disease Epidemiology Collaboration)-derived estimated glomerular filtration rate (eGFR). We additionally evaluated the risk-adjusted association of admission eGFR with in-hospital mortality. RESULTS: Among 365,494 hospitalizations (age 72 ± 15 years, left ventricular ejection fraction [EF]: 43 ± 17%), median discharge eGFR was 51 ml/min/1.73 m2 (interquartile range: 34 to 72 ml/min/1.73 m2), 234,332 (64%) had eGFR <60 ml/min/1.73 m2, and 18,869 (5%) were on dialysis. eGFR distribution remained stable from 2014 to 2019. Among 157,439 patients with HF with reduced EF (≤40%), discharge guideline-directed medical therapies, including beta-blockers, were lowest in discharge eGFR <30 mL/min/1.73 m2 or dialysis (p < 0.001). "Triple therapy" with angiotensin-converting enzyme inhibitor/angiotensin receptor blocker/angiotensin receptor-neprilysin inhibitor + beta-blocker + mineralocorticoid receptor antagonist was used in 38%, 33%, 25%, 15%, 5%, and 3% for eGFR ≥90, 60 to 89, 45 to 59, 30 to 44, <30 ml/min/1.73 m2, and dialysis, respectively; p < 0.001. Mortality was higher in a graded fashion at lower admission eGFR groups (1.1%, 1.5%, 2.0%, 3.0%, 5.0%, and 4.2%, respectively; p < 0.001). Steep covariate-adjusted associations between admission eGFR and mortality were observed across EF subgroups, but was slightly stronger for HF with reduced EF compared with HF with mid-range or preserved EF (pinteraction = 0.045). CONCLUSIONS: Despite facing elevated risks of mortality, patients with comorbid HF with reduced EF and kidney disease are not optimally treated with evidence-based medical therapies, even at levels of eGFR where such therapies would not be contraindicated by kidney dysfunction. Further efforts are required to mitigate risk in comorbid HF and kidney disease.

Applicability of US Food and Drug Administration Labeling for Dapagliflozin to Patients With Heart Failure With Reduced Ejection Fraction in US Clinical Practice: The Get With the Guidelines-Heart Failure (GWTG-HF) Registry.

IMPORTANCE: In May 2020, dapagliflozin was approved by the US Food and Drug Administration (FDA) as the first sodium-glucose cotransporter 2 inhibitor for heart failure with reduced ejection fraction (HFrEF), based on the Dapagliflozin and Prevention of Adverse Outcomes in Heart Failure (DAPA-HF) trial. Limited data are available characterizing the generalizability of dapagliflozin to US clinical practice. OBJECTIVE: To evaluate candidacy for initiation of dapagliflozin based on the FDA label among contemporary patients with HFrEF in the US. DESIGN, SETTING, AND PARTICIPANTS: This cohort study included 154 714 patients with HFrEF (left ventricular ejection fraction ≤40%) hospitalized at 406 sites in the Get With the Guidelines-Heart Failure (GWTG-HF) registry admitted between January 1, 2014, and September 30, 2019. Patients who left against medical advice, transferred to an acute care facility or to hospice, or had missing data were excluded. The FDA label (which excluded patients with an estimated glomerular filtration rate [eGFR] <30 mL/min/1.73 m2, those undergoing dialysis, and those with type 1 diabetes) was applied to the GWTG-HF registry sample. Data analyses were conducted from April 1 to June 30, 2020. MAIN OUTCOMES AND MEASURES: The proportion of patients hospitalized with HFrEF who would be candidates for dapagliflozin under the FDA label. RESULTS: Among 154 714 patients hospitalized with HFrEF, 125 497 (81.1%; 83 481 men [66.5%]; mean [SD] age, 68 [15] years) would be candidates for dapagliflozin according to the FDA label. Across 355 sites with patients with 10 or more hospitalizations, the median proportion of candidates for dapagliflozin according to the FDA label was 81.1% (interquartile range, 77.8%-84.6%) at each site. This proportion was similar across all study years (interquartile range, 80.4%-81.7%) and was higher among those without type 2 diabetes than with type 2 diabetes (85.5% vs 75.6%). Among GWTG-HF participants, the most frequent reason for not meeting the FDA label criteria was eGFR less than 30 mL/min/1.73 m2 at discharge (18.5%). Among 75 654 patients with available paired admission and discharge data, 14.2% had an eGFR less than 30 mL/min/1.73 m2 at both time points, while 3.8% developed an eGFR less than 30 mL/min/1.73 m2 by discharge. Although there were more older adults, women, and Black patients in the GWTG-HF registry than in the DAPA-HF trial, most clinical characteristics were qualitatively similar between the 2 groups. Compared with the DAPA-HF trial cohort, there was lower use of evidence-based HF therapies among patients in GWTG-HF. CONCLUSIONS AND RELEVANCE: These data from a large, contemporary US registry of patients hospitalized with heart failure suggest that 4 of 5 patients with HFrEF (with or without type 2 diabetes) would be candidates for initiation of dapagliflozin, supporting its broad generalizability to US clinical practice.

Effects of RNA structure and salt concentration on the affinity and kinetics of interactions between pentatricopeptide repeat proteins and their RNA ligands.

Pentatricopeptide repeat (PPR) proteins are helical repeat proteins that bind specific RNA sequences via modular 1-repeat:1-nucleotide interactions. Binding specificity is dictated, in part, by hydrogen bonds between the amino acids at two positions in each PPR motif and the Watson-Crick face of the aligned nucleobase. There is evidence that PPR-RNA interactions can compete with RNA-RNA interactions in vivo, and that this competition underlies some effects of PPR proteins on gene expression. Conversely, RNA secondary structure can inhibit the binding of a PPR protein to its specific binding site. The parameters that influence whether PPR-RNA or RNA-RNA interactions prevail are unknown. Understanding these parameters will be important for understanding the functions of natural PPR proteins and for the design of engineered PPR proteins for synthetic biology purposes. We addressed this question by analyzing the effects of RNA structures of varying stability and position on the binding of the model protein PPR10 to its atpH RNA ligand. Our results show that even very weak RNA structures (ΔG° ~ 0 kcal/mol) involving only one nucleotide at either end of the minimal binding site impede PPR10 binding. Analysis of binding kinetics using Surface Plasmon Resonance showed that RNA structures reduce PPR10's on-rate and increase its off-rate. Complexes between the PPR proteins PPR10 and HCF152 and their respective RNA ligands have long half-lives (one hour or more), correlating with their functions as barriers to exonucleolytic RNA decay in vivo. The effects of salt concentration on PPR10-RNA binding kinetics showed that electrostatic interactions play an important role in establishing PPR10-RNA interactions but play a relatively small role in maintaining specific interactions once established.

Mechanistic investigations reveal that dibromobimane extrudes sulfur from biological sulfhydryl sources other than hydrogen sulfide†Electronic supplementary information (ESI) available: Experimental details, pH stability data for BTE, NMR spectra. See DOI: 10.1039/c4sc01875cClick here for additional data file.

Hydrogen sulfide (H2S) has emerged as an important biological signaling molecule in the last decade. During the growth of this field, significant controversy has arisen centered on the physiological concentrations of H2S. Recently, a monobromobimane (mBB) method has been developed for the quantification of different biologically-relevant sulfide pools. Based on the prevalence of the mBB method for sulfide quantification, we expand on this method to report the use of dibromobimane (dBB) for sulfide quantification. Reaction of H2S with dBB results in formation of highly-fluorescent bimane thioether (BTE), which is readily quantifiable by HPLC. Additionally, the reaction of sulfide with dBB to form BTE is significantly faster than the reaction of sulfide with mBB to form sulfide dibimane. Using the dBB method, BTE levels as low as 0.6 pM can be detected. Upon use of the dBB method in wild-type and CSE-/- mice, however, dBB reports significantly higher sulfide levels than those measured using mBB. Further investigation revealed that dBB is able to extract sulfur from other sulfhydryl sources including thiols. Based on mechanistic studies, we demonstrate that dBB extracts sulfur from thiols with α- or ß-hydrogens, thus leading to higher BTE formation than from sulfide alone. Taken together, the dBB method is a highly sensitive method for H2S but is not compatible for use in studies in which other thiols are present.