Effect of severity and etiology of chronic kidney disease in patients with heart failure with mildly reduced ejection fraction.

OBJECTIVE: The study investigates the prognostic impact of the severity and etiology of chronic kidney disease (CKD) in patients with heart failure with mildly reduced ejection fraction (HFmrEF). BACKGROUND: Data regarding the outcomes in patients with CKD in HFmrEF is scarce. METHODS: Consecutive patients with HFmrEF were retrospectively included at one institution from 2016 to 2022. Prognosis of patients with different stages and etiologies of CKD was investigated with regard to the primary endpoint of all-cause mortality at 30 months. RESULTS: A total of 2155 consecutive patients with HFmrEF were included with an overall prevalence of CKD of 31%. Even milder stages of CKD (i.e., KDIGO stage 3a) were associated with an increased risk of 30-months all-cause mortality (HR = 1.242; 95% CI 1.147-1.346; p = 0.001). However, long-term prognosis did not differ in patients with KDIGO stage 5 compared to patients with stage 4 (HR = 0.886; 95% CI 0.616-1.275; p = 0.515). Furthermore, the highest risk of HF-related rehospitalization was observed in patients with KDIGO stages 3b and 4 (log rank p ≤ 0.015), whereas patients with KDIGO stage 5 had a lower risk of HF-related rehospitalization compared to patients with KDIGO stage 4 (HR = 0.440; 95% CI 0.228-0.849; p = 0.014). In contrast, the etiology of CKD was not associated with the risk of 30-month all-cause mortality (log rank p ≥ 0.347) and HF-related rehospitalization (log rank p ≥ 0.149). CONCLUSION: In patients with HFmrEF, even milder stages of CKD were independently associated with increased risk of 30-months all-cause mortality.

Prognostic Implications of Type 2 Diabetes Mellitus in Heart Failure with Mildly Reduced Ejection Fraction.

BACKGROUND: Data regarding the characterization and outcomes of diabetics with heart failure with a mildly reduced ejection fraction (HFmrEF) is scarce. This study investigates the prevalence and prognostic impact of type 2 diabetes in patients with HFmrEF. METHODS: Consecutive patients with HFmrEF (i.e., left ventricular ejection fraction 41-49% and signs and/or symptoms of HF) were retrospectively included at one institution from 2016 to 2022. Patients with type 2 diabetes (dia-betics) were compared to patients without (i.e., non-diabetics). The primary endpoint was all-cause mortality at 30 months. Statistical analyses included Kaplan-Meier, multivariable Cox regression analyses and propensity score matching. RESULTS: A total of 2169 patients with HFmrEF were included. The overall prevalence of type 2 diabetes was 36%. Diabetics had an increased risk of 30-months all-cause mortality (35.8% vs. 28.6%; HR = 1.273; 95% CI 1.092-1.483; p = 0.002), which was confirmed after multivariable adjustment (HR = 1.234; 95% CI 1.030-1.479; p = 0.022) and propensity score matching (HR = 1.265; 95% CI 1.018-1.572; p = 0.034). Diabetics had a higher risk of HF-related rehospitalization (17.8% vs. 10.7%; HR = 1.714; 95% CI 1.355-2.169; p = 0.001). Finally, the risk of all-cause mortality was increased in diabetics treated with insulin (40.7% vs. 33.1%; log-rank p = 0.029), whereas other anti-diabetic pharmacotherapies had no prognostic impact in HFmrEF. CONCLUSIONS: Type 2 diabetes is common and independently associated with adverse long-term prognosis in patients with HFmrEF.

Predictors and Prognostic Impact of Early Acute Kidney Injury in Cardiogenic Shock: Results from a Monocentric, Prospective Registry.

INTRODUCTION: The presence of acute kidney injury (AKI) was shown to increase the risk of mortality following acute myocardial infarction; however, data regarding the prognostic impact of early AKI in patients with concomitant cardiogenic shock (CS) is limited. The study investigates predictors and the prognostic impact of AKI in patients with CS. METHODS: Consecutive patients with CS from 2019 to 2021 were included at one institution. Laboratory values were retrieved from day of disease onset (day 1) and days 2, 3, 4, and 8 thereafter. Predictors for AKI (defined as an increase of plasma creatinine >50% within 48 h referring to pre-admission or baseline creatinine on day 1 and/or the need for continuous veno-venous hemodiafiltration [CVVHDF]) and the prognostic impact of early AKI with regard to 30-day all-cause mortality were assessed. Statistical analyses included t test, Spearman's correlation, C-statistics, Kaplan-Meier, and Cox proportional regression analyses. RESULTS: A total of 219 CS patients were included with an incidence of early CS-related AKI of 52%. With an area under the curve of up to 0.689 (p = 0.001), creatine discriminated 30-day mortality in CS. Increasing lactate levels (OR = 1.194; 95% CI: 1.083-1.316; p = 0.001; per increase of 1 mmol/L) was associated with the occurrence of AKI. The presence of AKI was associated with an increased risk of 30-day all-cause mortality (63% vs. 36%; HR = 2.138; 95% CI: 1.441-3.171; p = 0.001), even after multivariable adjustment (HR = 1.861; 95% CI: 1.207-2.869; p = 0.005). Finally, highest risk of all-cause mortality was observed in patients with AKI requiring CVVHDF (75% vs. 44%; log rank p = 0.001; HR = 2.211; 95% CI: 1.315-3.718; p = 0.003). CONCLUSION: Early AKI affects more than half of patients with CS and is independently associated with 30-day all-cause mortality in CS, with highest risk of death among patients with AKI requiring CVVHDF.

Prognostic impact of chronic obstructive pulmonary disease in patients with heart failure with mildly reduced ejection fraction.

BACKGROUND: The aging population has led to a significant increase in heart failure (HF) patients. Related to demographic changes, the burden with comorbidities was shown to increase in patients with HF. Whereas chronic obstructive pulmonary disease (COPD) was yet demonstrated to be associated with adverse outcomes in patients with HF, the prognostic impact of COPD in HF with mildly reduced ejection fraction (HFmrEF) has not yet been clarified. OBJECTIVE: The study investigates the prognostic impact of COPD in patients hospitalized with HFmrEF. METHODS: Consecutive patients with HFmrEF were retrospectively included at one institution from 2016 to 2022. Patients with COPD were compared to patients without with regard to the primary endpoint all-cause mortality at 30 months (median follow-up). Secondary endpoints comprised in-hospital mortality, HF-related re-hospitalization, cardiac re-hospitalization and major adverse cardiac and cerebrovascular events (MACCE) at 30 months. RESULTS: A total of 2184 patients with HFmrEF were included with a prevalence of COPD of 12.0 %. Patients with COPD were older (median 77 vs. 75 years; p = 0.025), had increased burden of cardiovascular comorbidities and more advanced HF symptoms. At 30 months, patients with COPD had an increased risk of all-cause mortality compared to patients without (45 % vs. 30 %; HR = 1.667; 95 % CI 1.366-2.034; p = 0.001), alongside with a higher risk of re-hospitalization for worsening HF (20 % vs. 12 %; HR = 1.658; 95 % CI 1.218-2.257; p = 0.001). CONCLUSION: COPD is independently associated with adverse outcomes in patients hospitalized with HFmrEF.

Secretin: a hormone for HCO3- homeostasis.

Secretin is a key hormone of the intestinal phase of digestion which activates pancreatic, bile duct and Brunner gland HCO3- secretion. Recently, the secretin receptor (SCTR) was also found in the basolateral membrane of the beta-intercalated cell (B-IC) of the collecting duct. Experimental addition of secretin triggers a pronounced activation of urinary HCO3- excretion, which is fully dependent on key functional proteins of the B-IC, namely apical pendrin and CFTR and the basolateral SCTR. Recent studies demonstrated that the SCTR knock-out mouse is unable to respond to an acute base load. Here, SCTR KO mice could not rapidly increase urine base excretion, developed prolonged metabolic alkalosis and exhibited marked compensatory hypoventilation. Here, we review the physiological effects of secretin with distinct focus on how secretin activates renal HCO3- excretion. We describe its new function as a hormone for HCO3- homeostasis.

Trimethoprim inhibits renal H+-K+-ATPase in states of K+ depletion.

There is growing consensus that under physiological conditions, collecting duct H+ secretion is independent of epithelial Na+ channel (ENaC) activity. We have recently shown that the direct ENaC inhibitor benzamil acutely impairs H+ excretion by blocking renal H+-K+-ATPase. However, the question remains whether inhibition of ENaC per se causes alterations in renal H+ excretion. To revisit this question, we studied the effect of the antibiotic trimethoprim (TMP), which is well known to cause K+ retention by direct ENaC inhibition. The acute effect of TMP (5 µg/g body wt) was assessed in bladder-catheterized mice, allowing real-time measurement of urinary pH, electrolyte, and acid excretion. Dietary K+ depletion was used to increase renal H+-K+-ATPase activity. In addition, the effect of TMP was investigated in vitro using pig gastric H+-K+-ATPase-enriched membrane vesicles. TMP acutely increased natriuresis and decreased kaliuresis, confirming its ENaC-inhibiting property. Under control diet conditions, TMP had no effect on urinary pH or acid excretion. Interestingly, K+ depletion unmasked an acute urine alkalizing effect of TMP. This finding was corroborated by in vitro experiments showing that TMP inhibits H+-K+-ATPase activity, albeit at much higher concentrations than benzamil. In conclusion, under control diet conditions, TMP inhibited ENaC function without changing urinary H+ excretion. This finding further supports the hypothesis that the inhibition of ENaC per se does not impair H+ excretion in the collecting duct. Moreover, TMP-induced urinary alkalization in animals fed a low-K+ diet highlights the importance of renal H+-K+-ATPase-mediated H+ secretion in states of K+ depletion.NEW & NOTEWORTHY The antibiotic trimethoprim (TMP) often mediates K+ retention and metabolic acidosis. We suggest a revision of the underlying mechanism that causes metabolic acidosis. Our results indicate that TMP-induced metabolic acidosis is secondary to epithelial Na+ channel-dependent K+ retention. Under control dietary conditions, TMP does not per se inhibit collecting duct H+ secretion. These findings add further argument against a physiologically relevant voltage-dependent mechanism of collecting duct H+ excretion.

Blood Pressure and Mortality in the 4D Study.

INTRODUCTION: Systolic blood pressure (SBP), diastolic blood pressure (DBP), and mean arterial pressure (MAP) are risk factors for cardiovascular mortality (CVM). Pulse pressure (PP) is an easily available parameter of vascular stiffness, but its impact on CVM in chronic dialysis patients with diabetes is unclear. METHODS: Therefore, we have examined the predictive value of baseline, predialytic PP, SBP, DBP, and MAP in the German Diabetes and Dialysis (4D) study, a prospective, randomized, double-blind trial enrolling 1,255 patients with type 2 diabetes on hemodialysis in 178 German dialysis centers. RESULTS: Mean age was 66.3 years, mean blood pressure 146/76 mm Hg, mean time suffering from diabetes 18.1 years, and mean time on maintenance dialysis 8.3 months. Considered as continuous variables, PP, MAP, SBP, and DBP could not provide a significant mortality prediction for either cardiovascular or all-cause mortality. After dividing the cohort into corresponding tertiles, we also did not detect any significant mortality prediction for PP, SBP, DBP, or MAP, both for all-cause mortality and CVM after adjusting for age and sex. Nevertheless, when comparing the HR plots of the corresponding blood pressure parameters, a pronounced U-curve was seen for PP for both all-cause mortality and CVM, with the trough range being 70-80 mm Hg. DISCUSSION: In patients with end-stage renal disease and long-lasting diabetes mellitus predialytic blood pressure parameters at study entry are not predictive for mortality, presumably because there is a very high rate of competing mortality risk factors, resulting in overall very high rates of all-cause and CVM that may no longer be significantly modulated by blood pressure control.

Benzamil-mediated urine alkalization is caused by the inhibition of H+-K+-ATPases.

Epithelial Na+ channel (ENaC) blockers elicit acute and substantial increases of urinary pH. The underlying mechanism remains to be understood. Here, we evaluated if benzamil-induced urine alkalization is mediated by an acute reduction in H+ secretion via renal H+-K+-ATPases (HKAs). Experiments were performed in vivo on HKA double-knockout and wild-type mice. Alterations in dietary K+ intake were used to change renal HKA and ENaC activity. The acute effects of benzamil (0.2 µg/g body wt, sufficient to block ENaC) on urine flow rate and urinary electrolyte and acid excretion were monitored in anesthetized, bladder-catheterized animals. We observed that benzamil acutely increased urinary pH (ΔpH: 0.33 ± 0.07) and reduced NH4+ and titratable acid excretion and that these effects were distinctly enhanced in animals fed a low-K+ diet (ΔpH: 0.74 ± 0.12), a condition when ENaC activity is low. In contrast, benzamil did not affect urine acid excretion in animals kept on a high-K+ diet (i.e., during high ENaC activity). Thus, urine alkalization appeared completely uncoupled from ENaC function. The absence of benzamil-induced urinary alkalization in HKA double-knockout mice confirmed the direct involvement of these enzymes. The inhibitory effect of benzamil was also shown in vitro for the pig α1-isoform of HKA. These results suggest a revised explanation of the benzamil effect on renal acid-base excretion. Considering the conditions used here, we suggest that it is caused by a direct inhibition of HKAs in the collecting duct and not by inhibition of the ENaC function.NEW & NOTEWORTHY Bolus application of epithelial Na+ channel (EnaC) blockers causes marked and acute increases of urine pH. Here, we provide evidence that the underlying mechanism involves direct inhibition of the H+-K+ pump in the collecting duct. This could provide a fundamental revision of the previously assumed mechanism that suggested a key role of ENaC inhibition in this response.

ENaC expression correlates with the acute furosemide-induced K+ excretion.

BACKGROUND: In the aldosterone-sensitive distal nephron (ASDN), epithelial sodium channel (ENaC)-mediated Na+ absorption drives K+ excretion. K+ excretion depends on the delivery of Na+ to the ASDN and molecularly activated ENaC. Furosemide is known as a K+ wasting diuretic as it greatly enhances Na+ delivery to the ASDN. Here, we studied the magnitude of acute furosemide-induced kaliuresis under various states of basal molecular ENaC activity. METHODS: C57/Bl6J mice were subjected to different dietary regimens that regulate molecular ENaC expression and activity levels. The animals were anesthetized and bladder-catheterized. Diuresis was continuously measured before and after administration of furosemide (2 µg/g BW) or benzamil (0.2 µg/g BW). Flame photometry was used to measure urinary [Na+ ] and [K+ ]. The kidneys were harvested and, subsequently, ENaC expression and cleavage activation were determined by semiquantitative western blotting. RESULTS: A low K+ and a high Na+ diet markedly suppressed ENaC protein expression, cleavage activation, and furosemide-induced kaliuresis. In contrast, furosemide-induced kaliuresis was greatly enhanced in animals fed a high K+ or low Na+ diet, conditions with increased ENaC expression. The furosemide-induced diuresis was similar in all dietary groups. CONCLUSION: Acute furosemide-induced kaliuresis differs greatly and depends on the a priori molecular expression level of ENaC. Remarkably, it can be even absent in animals fed a high Na+ diet, despite a marked increase of tubular flow and urinary Na+ excretion. This study provides auxiliary evidence that acute ENaC-dependent K+ excretion requires both Na+ as substrate and molecular activation of ENaC.

Vasopressin Increases Urinary Acidification via V1a Receptors in Collecting Duct Intercalated Cells.

BACKGROUND: Antagonists of the V1a vasopressin receptor (V1aR) are emerging as a strategy for slowing progression of CKD. Physiologically, V1aR signaling has been linked with acid-base homeostasis, but more detailed information is needed about renal V1aR distribution and function. METHODS: We used a new anti-V1aR antibody and high-resolution microscopy to investigate Va1R distribution in rodent and human kidneys. To investigate whether V1aR activation promotes urinary H+ secretion, we used a V1aR agonist or antagonist to evaluate V1aR function in vasopressin-deficient Brattleboro rats, bladder-catheterized mice, isolated collecting ducts, and cultured inner medullary collecting duct (IMCD) cells. RESULTS: Localization of V1aR in rodent and human kidneys produced a basolateral signal in type A intercalated cells (A-ICs) and a perinuclear to subapical signal in type B intercalated cells of connecting tubules and collecting ducts. Treating vasopressin-deficient Brattleboro rats with a V1aR agonist decreased urinary pH and tripled net acid excretion; we observed a similar response in C57BL/6J mice. In contrast, V1aR antagonist did not affect urinary pH in normal or acid-loaded mice. In ex vivo settings, basolateral treatment of isolated perfused medullary collecting ducts with the V1aR agonist or vasopressin increased intracellular calcium levels in ICs and decreased luminal pH, suggesting V1aR-dependent calcium release and stimulation of proton-secreting proteins. Basolateral treatment of IMCD cells with the V1aR agonist increased apical abundance of vacuolar H+-ATPase in A-ICs. CONCLUSIONS: Our results show that activation of V1aR contributes to urinary acidification via H+ secretion by A-ICs, which may have clinical implications for pharmacologic targeting of V1aR.

Potassium acts through mTOR to regulate its own secretion.

Potassium (K+) secretion by kidney tubule cells is central to electrolyte homeostasis in mammals. In the K+ secretory "principal" cells of the distal nephron, electrogenic Na+ transport by the epithelial sodium channel (ENaC) generates the electrical driving force for K+ transport across the apical membrane. Regulation of this process is attributable in part to aldosterone, which stimulates the gene transcription of the ENaC-regulatory kinase, SGK1. However, a wide range of evidence supports the conclusion that an unidentified aldosterone-independent pathway exists. We show here that in principal cells, K+ itself acts through the type 2 mTOR complex (mTORC2) to activate SGK1, which stimulates ENaC to enhance K+ excretion. The effect depends on changes in K+ concentration on the blood side of the cells, and requires basolateral membrane K+-channel activity. However, it does not depend on changes in aldosterone, or on enhanced distal delivery of Na+ from upstream nephron segments. These data strongly support the idea that K+ is sensed directly by principal cells to stimulate its own secretion by activating the mTORC2-SGK1 signaling module, and stimulate ENaC. We propose that this local effect acts in concert with aldosterone and increased Na+ delivery from upstream nephron segments to sustain K+ homeostasis.