Kidney tubular injury does not appear to have an association with WRF in the context of aggressive diuresis of patients with acute heart failure. These findings reinforce the notion that the small to moderate deteriorations in renal function commonly encountered with aggressive diuresis are dissimilar from traditional causes of acute kidney injury.

Biomarkers of diverse pathophysiologic mechanisms may improve risk stratification for incident or progressive diabetic kidney disease (DKD) in persons with type 2 diabetes. To evaluate such biomarkers, we performed a nested case-control study (=190 cases of incident DKD and 190 matched controls) and a prospective cohort study (=1156) using banked baseline plasma samples from participants of randomized, controlled trials of early (ACCORD) and advanced (VA NEPHRON-D) DKD. We assessed the association and discrimination obtained with baseline levels of plasma TNF receptor-1 (TNFR-1), TNFR-2, and kidney injury molecule-1 (KIM-1) for the outcomes of incident DKD (ACCORD) and progressive DKD (VA-NEPHRON-D). At baseline, median concentrations of TNFR-1, TNFR-2, and KIM-1 were roughly two-fold higher in the advanced DKD population (NEPHRON-D) than in the early DKD population (ACCORD). In both cohorts, patients who reached the renal outcome had higher baseline levels than those who did not reach the outcome. Associations between doubling in TNFR-1, TNFR-2, and KIM-1 levels and risk of the renal outcomes were significant for both cohorts. Inclusion of these biomarkers in clinical models increased the area under the curve (SEM) for predicting the renal outcome from 0.68 (0.02) to 0.75 (0.02) in NEPHRON-D. Systematic review of the literature illustrated high consistency in the association between these biomarkers of inflammation and renal outcomes in DKD. In conclusion, TNFR-1, TNFR-2, and KIM-1 independently associated with higher risk of eGFR decline in persons with early or advanced DKD. Moreover, addition of these biomarkers to clinical prognostic models significantly improved discrimination for the renal outcome.

Background: Sodium-glucose cotransporter-2 inhibitors (SGLT-2i's) improve heart failure (HF) related outcomes. The mechanisms underlying these benefits are not well understood, but diuretic properties may contribute. Traditional diuretics, such as furosemide, induce substantial neurohormonal activation contributing to the limited improvement in intravascular volume often seen with these agents. However, the proximal tubular site of action of the SGLT-2i's may help circumvent these limitations. Methods: 20 patients with type-2 diabetes and chronic, stable HF completed a randomized placebo-controlled crossover study of empagliflozin 10mg daily vs. placebo. Patients underwent an intensive 6-hour biospecimen collection and cardio-renal phenotyping at baseline and again after 14 days of study drug. After a 2-week washout, patients crossed over to the alternate therapy with repeat of the above protocol. Results: Oral empagliflozin was rapidly absorbed as evidenced by a 27-fold increase in urinary glucose excretion by 3 hours (p<0.0001). Fractional excretion of sodium (FENa) increased significantly with empagliflozin monotherapy vs. placebo (FENa 1.2 ± 0.7% vs. 0.7 ± 0.4% p=0.001) and there was a synergistic effect in combination with bumetanide (FENa 5.8 ± 2.5% vs. 3.9 ± 1.9%, p=0.001). At 14 days, the natriuretic effect of empagliflozin persisted, resulting in a reduction in blood volume (-208mL, IQR -536 to 153 mL vs -14mL, IQR -282 to 335 mL, p=0.035), and plasma volume (-138mL, IQR -379 to 154mL ± 453 mL, p=0.04). This natriuresis was not, however, associated with evidence of neurohormonal activation as change in norepinephrine was superior (p = 0.02) and all other neurohormones similar (p<0.34) during the empagliflozin vs. placebo period. Furthermore, there was no evidence of potassium wasting (p=0.20), or renal dysfunction (p>0.11 for all biomarkers), whereas both serum magnesium (p<0.001) and uric acid levels (p=0.008) improved. Conclusions: Empagliflozin causes significant natriuresis, particularly when combined with loop diuretics, resulting in an improvement in blood volume. However, off-target electrolyte wasting, renal dysfunction, and neurohormonal activation were not observed. This favorable diuretic profile may offer significant advantage in the management of volume status in HF patients and may represent a mechanism contributing to the superior long-term HF outcomes observed with these agents. Clinical Trial Registration: URL: https://clinicaltrials.gov Unique Identifier: NCT03029760

SummarySeveral snake venoms contain procoagulant proteins that can activate prothrombin. We have purified pseutarin C, a prothrombin activator from the venom of the Australian brown snake (Pseudonaja textilis). It converts prothrombin to thrombin by cleaving both the peptide bonds Arg274 – Thr275 and Arg323 – Ile324, similar to mammalian factor Xa. It is a protein complex (∼250 Kd) consisting of an enzymatic and a nonenzymatic subunit. These subunits were separated by reverse phase HPLC and their interactions with bovine factor Xa and factor Va were studied. The enzymatic subunit of pseutarin C has a ∼13 fold higher affinity for bovine factor Va (K d of 11.4 nM for pseutarin C enzymatic subunit – bovine factor Va interaction as compared to a K d of 147.4 nM for the bovine factor Xa-Va interaction). The non-enzymatic component, however, was unable to activate bovine factor Xa. N-terminal sequence analysis of the catalytic subunit of pseutarin C showed ∼ 60% homology to mammalian factor Xa and ∼78% homology to trocarin, a group D prothrombin activator from Tropidechis carinatus venom. Structural information for the non-enzymatic subunit of pseutarin C was obtained by amino terminal sequencing of several internal peptides. The sequence data obtained indicates that the non-enzymatic subunit of pseutarin C has similar domain architecture like the mammalian factor Va and the overall homology is ∼55%. Thus pseutarin C is the first venom procoagulant protein that is structurally and functionally similar to mammalian factor Xa-Va complex.

Background Removal of excess sodium and fluid is a primary therapeutic objective in acute decompensated heart failure (ADHF) and commonly monitored with fluid balance and weight loss. However, these parameters are frequently inaccurate or not collected and require a delay of several hours after diuretic administration before they are available. Accessible tools for rapid and accurate prediction of diuretic response are needed. Methods and Results Based on well-established renal physiologic principles an equation was derived to predict net sodium output using a spot urine sample obtained one or two hours following loop diuretic administration. This equation was then prospectively validated in 50 ADHF patients using meticulously obtained timed 6-hour urine collections to quantitate loop diuretic induced cumulative sodium output. Poor natriuretic response was defined as a cumulative sodium output of <50 mmol, a threshold that would result in a positive sodium balance with twice-daily diuretic dosing. Following a median dose of 3 mg (2–4 mg) of intravenous bumetanide, 40% of the population had a poor natriuretic response. The correlation between measured and predicted sodium output was excellent (r=0.91, p<0.0001). Poor natriuretic response could be accurately predicted with the sodium prediction equation (AUC=0.95, 95% CI 0.89–1.0, p<0.0001). Clinically recorded net fluid output had a weaker correlation (r=0.66, p<0.001) and lesser ability to predict poor natriuretic response (AUC=0.76, 95% CI 0.63–0.89, p=0.002). Conclusions In patients being treated for ADHF, poor natriuretic response can be predicted soon after diuretic administration with excellent accuracy using a spot urine sample.

Background Recent epidemiologic studies have implicated chloride, rather than sodium, as the driver of poor survival previously attributed to hyponatremia in heart failure (HF). Accumulating basic science evidence has identified chloride as a critical factor in renal salt sensing. Our goal was to probe the physiology bridging this basic and epidemiologic literature. Methods and Results Two HF cohorts were included: (1) Observational: Patients receiving loop diuretics at the Yale Transitional Care Center (YTCC; N=162); (2) Interventional Pilot: Stable outpatients receiving ≥80mg furosemide equivalents were studied before and after three days of 115 mmol/d supplemental lysine chloride (N=10). In YTCC, 31.5% of patients had hypochloremia (chloride ≤96 mmol/L). Plasma renin concentration correlated with serum chloride (r=−0.46, p<0.001) with no incremental contribution from serum sodium (p=0.49). Hypochloremic vs. non-hypochloremic patients exhibited renal wasting of chloride (p=0.04) and of chloride relative to sodium (p=0.01), despite better renal free water excretion (urine osmolality 372±94 mOsm/kg vs. 507±118, p<0.001). Hypochloremia was associated with poor diuretic response (OR=7.3, 95% CI 3.3–16.1, p<0.001). In the interventional pilot, lysine chloride supplementation was associated with an increase in serum chloride levels of 2.2±2.3 mmol/L and the majority of participants experienced findings such as hemoconcentration, weight loss, reduction in NT-proBNP, increased plasma renin activity, and increased blood urea nitrogen to creatinine ratio. Conclusions Hypochloremia is associated with neurohormonal activation and diuretic resistance with chloride depletion as a candidate mechanism. Sodium-free chloride supplementation was associated with increases in serum chloride and changes in several cardio-renal parameters. Clinical Trial Registration URL: http://www.clinicaltrials.gov. Unique identifier: NCT02031354.

Background Loop diuretic resistance is a common barrier to effective decongestion in acute heart failure (AHF), and is associated with poor outcome. Specific mechanisms underlying diuretic resistance are currently unknown in contemporary AHF patients. We therefore aimed to determine the relative importance of defects in diuretic delivery vs. renal tubular response in determining diuretic response (DR) in AHF. Methods and results Fifty AHF patients treated with intravenous bumetanide underwent a 6-h timed urine collection for sodium and bumetanide clearance. Whole-kidney DR was defined as sodium excreted per doubling of administered loop diuretic and represents the sum of defects in drug delivery and renal tubular response. Tubular DR, defined as sodium excreted per doubling of renally cleared (urinary) loop diuretic, captures resistance specifically in the renal tubule. Median administered bumetanide dose was 3.0 (2.0–4.0) mg with 52 (33–77)% of the drug excreted into the urine. Significant between-patient variability was present as the administered dose only explained 39% of variability in the quantity of bumetanide in urine. Cumulatively, factors related to drug delivery such as renal bumetanide clearance, administered dose, and urea clearance explained 28% of the variance in whole-kidney DR. However, resistance at the level of the renal tubule (tubular DR) explained 71% of the variability in whole-kidney DR. Conclusion Defects at the level of the renal tubule are substantially more important than reduced diuretic delivery in determining diuretic resistance in patients with AHF.

Hypothermic machine perfusion (HMP) is increasingly used in deceased-donor kidney transplantation, but controversy exists regarding the value of perfusion biomarkers and pump parameters for assessing organ quality. We prospectively determined associations between perfusate biomarkers [neutrophil gelatinase-associated lipocalin (NGAL), kidney injury molecule-1 (KIM-1), interleukin-18 (IL-18) and liver-type fatty acid-binding protein (L-FABP)] and pump parameters (resistance and flow) with outcomes of delayed graft function (DGF) and 6-month estimated glomerular filtration rate (eGFR). DGF occurred in 230/671 (34%) recipients. Only 1-hour flow was inversely associated with DGF. Higher NGAL or L-FABP concentrations and increased resistance were inversely associated with 6-month eGFR, while higher flow was associated with higher adjusted 6-month eGFR. Discarded kidneys had consistently higher median resistance and lower median flow than transplanted kidneys, but median perfusate biomarker concentrations were either lower or not significantly different in discarded compared with transplanted kidneys. Notably, most recipients of transplanted kidneys with isolated “undesirable” biomarker levels or HMP parameters experienced acceptable 6-month allograft function, suggesting these characteristics should not be used in isolation for discard decisions. Additional studies must confirm the utility of combining HMP measurements with other characteristics to assess kidney quality.