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BACKGROUND: Torsemide is proposed to have clinically important pharmacokinetic and pharmacodynamic advantages over furosemide. However, clinical outcomes did not differ in the Torsemide Comparison with Furosemide for Management of Heart Failure (TRANSFORM-HF) randomized trial. METHODS: We conducted a multicenter mechanistic substudy of patients with heart failure randomized to oral furosemide or torsemide (TRANSFORM-Mechanism). At baseline and 30 days, participants underwent detailed assessments of pharmacokinetic and pharmacodynamic parameters. RESULTS: TRANSFORM-Mechanism enrolled 88 participants. Kidney bioavailability, or the proportion of dose delivered to the tubular site of action, was significantly less with torsemide compared to furosemide [median 17.1%, (IQR 12.3, 23.5%) vs. 24.8% (16.6, 34.1%), p < 0.001]. Furosemide had a longer duration of kidney drug delivery and duration of natriuresis (p≤0.004 for both). Prescribed doses of furosemide and torsemide in TRANSFORM-Mechanism were similar to TRANSFORM-HF, with providers on average using a 2:1 dose equivalence conversion between drugs. However, these doses resulted in a substantially greater natriuresis with torsemide (p<0.001). A dose equivalence of â¼4:1 resulted in similar natriuresis. Higher diuretic doses in the torsemide group resulted in mild perturbations in kidney function and significant increases in renin, aldosterone, and norepinephrine (p<0.05 for all). Plasma volume (p=0.52) and body weight (p=0.89) did not improve with torsemide vs. furosemide. CONCLUSIONS: We observed no meaningful pharmacokinetic/pharmacodynamic advantages for torsemide vs. furosemide. The greater natriuresis from higher diuretic doses in the torsemide group was offset by greater neurohormonal activation and kidney dysfunction.
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The disease Familial Hyperkalemic Hypertension (FHHt; also known as Gordon Syndrome) is caused by aberrant accumulation of WNK4 activating the NaCl cotransporter (NCC) in the distal convoluted tubule (DCT) of the kidney. Mutations in cullin 3 (CUL3) cause FHHt by disrupting interaction with the deneddylase COP9 signalosome (CSN). Deletion of Cul3 or Jab1 (the catalytically active CSN subunit) along the entire nephron causes a partial FHHt phenotype with activation of the WNK4-SPAK-NCC pathway. However, progressive kidney injury likely prevents hypertension, hyperkalemia, and hyperchloremic metabolic acidosis associated with FHHt. We hypothesized that DCT-specific deletion would more closely model the disease. We utilized Slc12a3-Cre-ERT2 mice to delete Cul3 (DCT-Cul3-/-) or Jab1 (DCT-Jab1-/-) only in DCT and examined the mice after short- and long-term deletion. Short-term, DCT-specific knockout of both Cul3 and Jab1 mice caused elevated WNK4, SPAK, and pNCC abundance. However, neither model demonstrated changes in plasma K+, Cl-, or TCO2, even though no injury was present. Long-term DCT-Jab1-/- mice showed significantly lower NCC and parvalbumin abundance, and higher abundance of kidney injury molecule 1 (KIM-1), a marker of proximal tubule injury. No injury, or reduction in NCC or parvalbumin were observed in long-term DCT-Cul3-/- mice. In summary, the prevention of injury outside the DCT did not lead to a complete FHHt phenotype despite activation of the WNK4-SPAK-NCC pathway, possibly due to insufficient NCC activation. Chronically, only DCT-Jab1-/- mice developed tubule injury and atrophy of the DCT, suggesting a direct JAB1 effect or dysregulation of other cullins as mechanisms for injury.
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Bidirectional communication between tumours and neurons has emerged as a key facet of the tumour microenvironment that drives malignancy1,2. Another hallmark feature of cancer is epigenomic dysregulation, in which alterations in gene expression influence cell states and interactions with the tumour microenvironment3. Ependymoma (EPN) is a paediatric brain tumour that relies on epigenomic remodelling to engender malignancy4,5; however, how these epigenetic mechanisms intersect with extrinsic neuronal signalling during EPN tumour progression is unknown. Here we show that the activity of serotonergic neurons regulates EPN tumorigenesis, and that serotonin itself also serves as an activating modification on histones. We found that inhibiting histone serotonylation blocks EPN tumorigenesis and regulates the expression of a core set of developmental transcription factors. High-throughput, in vivo screening of these transcription factors revealed that ETV5 promotes EPN tumorigenesis and functions by enhancing repressive chromatin states. Neuropeptide Y (NPY) is one of the genes repressed by ETV5, and its overexpression suppresses EPN tumour progression and tumour-associated network hyperactivity through synaptic remodelling. Collectively, this study identifies histone serotonylation as a key driver of EPN tumorigenesis, and also reveals how neuronal signalling, neuro-epigenomics and developmental programs are intertwined to drive malignancy in brain cancer.
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Carcinogénesis , Ependimoma , Regulación Neoplásica de la Expresión Génica , Histonas , Factores de Transcripción , Histonas/metabolismo , Animales , Carcinogénesis/genética , Carcinogénesis/patología , Carcinogénesis/metabolismo , Ratones , Humanos , Ependimoma/genética , Ependimoma/metabolismo , Ependimoma/patología , Factores de Transcripción/metabolismo , Masculino , Femenino , Proteínas de Unión al ADN/metabolismo , Proteínas de Unión al ADN/genética , Neoplasias Encefálicas/patología , Neoplasias Encefálicas/genética , Neoplasias Encefálicas/metabolismo , Epigénesis Genética , Cromatina/metabolismo , Cromatina/genética , Microambiente Tumoral , Línea Celular Tumoral , Progresión de la EnfermedadRESUMEN
BACKGROUND: Survival data for recurrent pediatric atypical teratoid rhabdoid tumor (ATRT) and its association to molecular groups are extremely limited. METHODS: Single-institution retrospective study of 64 children less than 21 years old with recurrent or treatment-refractory (progressive disease [PD]) ATRT treated at St. Jude Hospital from January 2000 to December 2020. Demographic, clinicopathologic, treatment, molecular grouping (SHH, TYR, and MYC) and germline data were collected. Progression-free survival (PFS2: time from PD to subsequent first progression) and overall survival (OSpostPD: time from PD to death/last follow-up) were estimated by Kaplan-Meier analysis. RESULTS: Median age at and time from initial diagnosis to PD were 2.1 years (range: 0.5-17.9 years) and 5.4 months (range: 0.5-125.6 months), respectively. Only five of 64 children (7.8%) are alive at median follow-up of 10.9 (range: 4.2-18.1) years from PD. The 2/5-year PFS2 and OSpostPD were 3.1% (±1.8%)/1.6% (±1.1%) and 20.3% (±4.8%)/7.3% (±3.5%), respectively. Children with TYR group (n = 10) had a better OSpostPD compared to those with MYC (n = 11) (2-year survival estimates: 60.0% ± 14.3% vs. 18.2% ± 9.5%; p = .019), or those with SHH (n = 21; 4.8% ± 3.3%; p = .014). In univariate analyses, OSpostPD was better with older age at diagnosis (p = .037), female gender (p = .008), and metastatic site of PD compared to local or combined sites of PD (p < .001). Two-year OSpostPD for patients receiving any salvage therapy (n = 39) post PD was 33.3% ± 7.3%. CONCLUSIONS: Children with recurrent/refractory ATRT have dismal outcomes. Older age at diagnosis, female gender, TYR group, and metastatic site of PD were associated with relatively longer survival in our study.
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Recurrencia Local de Neoplasia , Tumor Rabdoide , Teratoma , Humanos , Tumor Rabdoide/mortalidad , Tumor Rabdoide/terapia , Tumor Rabdoide/patología , Masculino , Femenino , Niño , Preescolar , Estudios Retrospectivos , Lactante , Adolescente , Recurrencia Local de Neoplasia/patología , Recurrencia Local de Neoplasia/mortalidad , Teratoma/mortalidad , Teratoma/patología , Teratoma/terapia , Tasa de Supervivencia , Estudios de Seguimiento , Pronóstico , Recién Nacido , Biomarcadores de Tumor/genéticaRESUMEN
Klotho regulates many pathways in the aging process, but it remains unclear how it is physiologically regulated. Because Klotho is synthesized, cleaved, and released from the kidney; activates the chief urinary K+ secretion channel (ROMK) and stimulates urinary K+ secretion, we explored if Klotho protein is regulated by dietary K+ and the potassium-regulatory hormone, Aldosterone. Klotho protein along the nephron was evaluated in humans and in wild-type (WT) mice; and in mice lacking components of Aldosterone signaling, including the Aldosterone-Synthase KO (AS-KO) and the Mineralocorticoid-Receptor KO (MR-KO) mice. We found the specific cells of the distal nephron in humans and mice that are chief sites of regulated K+ secretion have the highest Klotho protein expression along the nephron. WT mice fed K+-rich diets increased Klotho expression in these cells. AS-KO mice exhibit normal Klotho under basal conditions but could not upregulate Klotho in response to high-K+ intake in the K+-secreting cells. Similarly, MR-KO mice exhibit decreased Klotho protein expression. Together, i) Klotho is highly expressed in the key sites of regulated K+ secretion in humans and mice, ii) In mice, K+-rich diets increase Klotho expression specifically in the potassium secretory cells of the distal nephron, iii) Aldosterone signaling is required for Klotho response to high K+ intake.
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Aldosterona , Glucuronidasa , Proteínas Klotho , Ratones Noqueados , Potasio , Proteínas Klotho/metabolismo , Animales , Humanos , Ratones , Potasio/metabolismo , Aldosterona/metabolismo , Glucuronidasa/metabolismo , Glucuronidasa/genética , Masculino , Nefronas/metabolismo , Potasio en la Dieta/metabolismo , Potasio en la Dieta/administración & dosificación , Femenino , Receptores de Mineralocorticoides/metabolismo , Receptores de Mineralocorticoides/genética , Ratones Endogámicos C57BLAsunto(s)
Insuficiencia Cardíaca , Inhibidores del Simportador de Cloruro Sódico y Cloruro Potásico , Torasemida , Humanos , Insuficiencia Cardíaca/tratamiento farmacológico , Inhibidores del Simportador de Cloruro Sódico y Cloruro Potásico/administración & dosificación , Inhibidores del Simportador de Cloruro Sódico y Cloruro Potásico/uso terapéutico , Administración Oral , Sulfonamidas/administración & dosificación , Sulfonamidas/uso terapéuticoAsunto(s)
Riñón , Humanos , Estados Unidos , Historia del Siglo XXI , Fisiología/historia , Sociedades CientíficasRESUMEN
BACKGROUND: Potassium (K+)-deficient diets, typical of modern processed foods, increase blood pressure (BP) and NaCl sensitivity. A K+-dependent signaling pathway in the kidney distal convoluted tubule, coined the K+ switch, that couples extracellular K+ sensing to activation of the thiazide-sensitive NaCl cotransporter (NCC) and NaCl retention has been implicated, but causality has not been established. METHODS: To test the hypothesis that small, physiological changes in plasma K+ (PK+) are translated to BP through the switch pathway, a genetic approach was used to activate the downstream switch kinase, SPAK (SPS1-related proline/alanine-rich kinase), within the distal convoluted tubule. The CA-SPAK (constitutively active SPS1-related proline/alanine-rich kinase mice) were compared with control mice over a 4-day PK+ titration (3.8-5.1 mmol) induced by changes in dietary K+. Arterial BP was monitored using radiotelemetry, and renal function measurements, NCC abundance, phosphorylation, and activity were made. RESULTS: As PK+ decreased in control mice, BP progressively increased and became sensitive to dietary NaCl and hydrochlorothiazide, coincident with increased NCC phosphorylation and urinary sodium retention. By contrast, BP in CA-SPAK mice was elevated, resistant to the PK+ titration, and sensitive to hydrochlorothiazide and salt at all PK+ levels, concomitant with sustained and elevated urinary sodium retention and NCC phosphorylation and activity. Thus, genetically locking the switch on drives NaCl sensitivity and prevents the response of BP to potassium. CONCLUSIONS: Low K+, common in modern ultraprocessed diets, presses the K+-switch pathway to turn on NCC activity, increasing sodium retention, BP, and salt sensitivity.
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Potasio , Proteínas Serina-Treonina Quinasas , Animales , Ratones , Potasio/metabolismo , Proteínas Serina-Treonina Quinasas/metabolismo , Potasio en la Dieta/metabolismo , Presión Sanguínea/fisiología , Cloruro de Sodio/metabolismo , Miembro 3 de la Familia de Transportadores de Soluto 12/metabolismo , Transducción de Señal , Fosforilación , Túbulos Renales Distales/metabolismo , Hidroclorotiazida , Sodio/metabolismo , Alanina/metabolismo , Prolina/metabolismoRESUMEN
Scientific innovation is overturning conventional paradigms of forest, water, and energy cycle interactions. This has implications for our understanding of the principal causal pathways by which tree, forest, and vegetation cover (TFVC) influence local and global warming/cooling. Many identify surface albedo and carbon sequestration as the principal causal pathways by which TFVC affects global warming/cooling. Moving toward the outer latitudes, in particular, where snow cover is more important, surface albedo effects are perceived to overpower carbon sequestration. By raising surface albedo, deforestation is thus predicted to lead to surface cooling, while increasing forest cover is assumed to result in warming. Observational data, however, generally support the opposite conclusion, suggesting surface albedo is poorly understood. Most accept that surface temperatures are influenced by the interplay of surface albedo, incoming shortwave (SW) radiation, and the partitioning of the remaining, post-albedo, SW radiation into latent and sensible heat. However, the extent to which the avoidance of sensible heat formation is first and foremost mediated by the presence (absence) of water and TFVC is not well understood. TFVC both mediates the availability of water on the land surface and drives the potential for latent heat production (evapotranspiration, ET). While latent heat is more directly linked to local than global cooling/warming, it is driven by photosynthesis and carbon sequestration and powers additional cloud formation and top-of-cloud reflectivity, both of which drive global cooling. TFVC loss reduces water storage, precipitation recycling, and downwind rainfall potential, thus driving the reduction of both ET (latent heat) and cloud formation. By reducing latent heat, cloud formation, and precipitation, deforestation thus powers warming (sensible heat formation), which further diminishes TFVC growth (carbon sequestration). Large-scale tree and forest restoration could, therefore, contribute significantly to both global and surface temperature cooling through the principal causal pathways of carbon sequestration and cloud formation.
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Secuestro de Carbono , Cambio Climático , Bosques , Planetas , Temperatura , Agua , Frío , ÁrbolesRESUMEN
Kidney-specific with-no-lysine kinase 1 (KS-WNK1) is an isoform of WNK1 kinase that is predominantly found in the distal convoluted tubule of the kidney. The precise physiological function of KS-WNK1 remains unclear. Some studies have suggested that it could play a role in regulating potassium renal excretion by modulating the activity of the Na+-Cl- cotransporter (NCC). However, changes in the potassium diet from normal to high failed to reveal a role for KS-WNK1, but under a normal-potassium diet, the expression of KS-WNK1 is negligible. It is only detectable when mice are exposed to a low-potassium diet. In this study, we investigated the role of KS-WNK1 in regulating potassium excretion under extreme changes in potassium intake. After following a zero-potassium diet (0KD) for 10 days, KS-WNK1-/- mice had lower plasma levels of K+ and Cl- while exhibiting higher urinary excretion of Na+, Cl-, and K+ compared with KS-WNK1+/+ mice. After 10 days of 0KD or normal-potassium diet (NKD), all mice were challenged with a high-potassium diet (HKD). Plasma K+ levels markedly increased after the HKD challenge only in mice previously fed with 0KD, regardless of genotype. KSWNK1+/+ mice adapt better to HKD challenge than KS-WNK1-/- mice after a potassium-retaining state. The difference in the phosphorylated NCC-to-NCC ratio between KS-WNK1+/+ and KS-WNK1-/- mice after 0KD and HKD indicates a role for KS-WNK1 in both NCC phosphorylation and dephosphorylation. These observations show that KS-WNK1 helps the distal convoluted tubule to respond to extreme changes in potassium intake, such as those occurring in wildlife.NEW & NOTEWORTHY The findings of this study demonstrate that kidney-specific with-no-lysine kinase 1 plays a role in regulating urinary electrolyte excretion during extreme changes in potassium intake, such as those occurring in wildlife. .
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Ratones Noqueados , Potasio en la Dieta , Proteína Quinasa Deficiente en Lisina WNK 1 , Animales , Masculino , Ratones , Riñón/metabolismo , Túbulos Renales Distales/metabolismo , Ratones Endogámicos C57BL , Fosforilación , Potasio/orina , Potasio/metabolismo , Potasio/sangre , Potasio en la Dieta/metabolismo , Proteínas Serina-Treonina Quinasas/metabolismo , Proteínas Serina-Treonina Quinasas/genética , Eliminación Renal , Miembro 3 de la Familia de Transportadores de Soluto 12/metabolismo , Miembro 3 de la Familia de Transportadores de Soluto 12/genética , Proteína Quinasa Deficiente en Lisina WNK 1/metabolismo , Proteína Quinasa Deficiente en Lisina WNK 1/genética , FemeninoRESUMEN
SIGNIFICANCE STATEMENT: High-resolution single-nucleus RNA-sequencing data indicate a clear separation between primary sites of calcium and magnesium handling within distal convoluted tubule (DCT). Both DCT1 and DCT2 express Slc12a3, but these subsegments serve distinctive functions, with more abundant magnesium-handling genes along DCT1 and more calcium-handling genes along DCT2. The data also provide insight into the plasticity of the distal nephron-collecting duct junction, formed from cells of separate embryonic origins. By focusing/changing gradients of gene expression, the DCT can morph into different physiological cell states on demand. BACKGROUND: The distal convoluted tubule (DCT) comprises two subsegments, DCT1 and DCT2, with different functional and molecular characteristics. The functional and molecular distinction between these segments, however, has been controversial. METHODS: To understand the heterogeneity within the DCT population with better clarity, we enriched for DCT nuclei by using a mouse line combining "Isolation of Nuclei Tagged in specific Cell Types" and sodium chloride cotransporter-driven inducible Cre recombinase. We sorted the fluorescently labeled DCT nuclei using Fluorescence-Activated Nucleus Sorting and performed single-nucleus transcriptomics. RESULTS: Among 25,183 DCT cells, 75% were from DCT1 and 25% were from DCT2. In addition, there was a small population (<1%) enriched in proliferation-related genes, such as Top2a , Cenpp , and Mki67 . Although both DCT1 and DCT2 expressed sodium chloride cotransporter, magnesium transport genes were predominantly expressed along DCT1, whereas calcium, electrogenic sodium, and potassium transport genes were more abundant along DCT2. The transition between these two segments was gradual, with a transitional zone in which DCT1 and DCT2 cells were interspersed. The expression of the homeobox genes by DCT cells suggests that they develop along different trajectories. CONCLUSIONS: Transcriptomic analysis of an enriched rare cell population using a genetically targeted approach clarifies the function and classification of distal cells. The DCT segment is short, can be separated into two subsegments that serve distinct functions, and is speculated to derive from different origins during development.
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Calcio , Magnesio , Calcio/metabolismo , Magnesio/metabolismo , Simportadores del Cloruro de Sodio/metabolismo , Transporte Iónico , ARN/análisis , Túbulos Renales Distales/metabolismoRESUMEN
BACKGROUND: High-grade gliomas (HGG) in young children pose a challenge due to favorable but unpredictable outcomes. While retrospective studies broadened our understanding of tumor biology, prospective data is lacking. METHODS: A cohort of children with histologically diagnosed HGG from the SJYC07 trial was augmented with nonprotocol patients with HGG treated at St. Jude Children's Research Hospital from November 2007 to December 2020. DNA methylome profiling and whole genome, whole exome, and RNA sequencing were performed. These data were integrated with histopathology to yield an integrated diagnosis. Clinical characteristics and preoperative imaging were analyzed. RESULTS: Fifty-six children (0.0-4.4 years) were identified. Integrated analysis split the cohort into four categories: infant-type hemispheric glioma (IHG), HGG, low-grade glioma (LGG), and other-central nervous system (CNS) tumors. IHG was the most prevalent (nâ =â 22), occurred in the youngest patients (median ageâ =â 0.4 years), and commonly harbored receptor tyrosine kinase gene fusions (7 ALK, 2 ROS1, 3 NTRK1/2/3, 4 MET). The 5-year event-free (EFS) and overall survival (OS) for IHG was 53.13% (95%CI: 35.52-79.47) and 90.91% (95%CI: 79.66-100.00) vs. 0.0% and 16.67% (95%CI: 2.78-99.74%) for HGG (pâ =â 0.0043, pâ =â 0.00013). EFS and OS were not different between IHG and LGG (pâ =â 0.95, pâ =â 0.43). Imaging review showed IHGs are associated with circumscribed margins (pâ =â 0.0047), hemispheric location (pâ =â 0.0010), and intratumoral hemorrhage (pâ =â 0.0149). CONCLUSIONS: HGG in young children is heterogeneous and best defined by integrating histopathological and molecular features. Patients with IHG have relatively good outcomes, yet they endure significant deficits, making them good candidates for therapy de-escalation and trials of molecular targeted therapy.
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Neoplasias Encefálicas , Glioma , Niño , Lactante , Humanos , Preescolar , Estudios Retrospectivos , Estudios Prospectivos , Proteínas Tirosina Quinasas , Proteínas Proto-Oncogénicas , Glioma/tratamiento farmacológico , Glioma/genética , Glioma/diagnóstico , Neoplasias Encefálicas/tratamiento farmacológico , Neoplasias Encefálicas/genéticaRESUMEN
BACKGROUND: Kir4.2 and Kir4.1 play a role in regulating membrane transport in the proximal tubule (PT) and in the distal-convoluted-tubule (DCT), respectively. METHODS: We generated kidney-tubule-specific-AT1aR-knockout (Ks-AT1aR-KO) mice to examine whether renal AT1aR regulates Kir4.2 and Kir4.1. RESULTS: Ks-AT1aR-KO mice had a lower systolic blood pressure than Agtr1aflox/flox (control) mice. Ks-AT1aR-KO mice had a lower expression of NHE3 (Na+/H+-exchanger 3) and Kir4.2, a major Kir-channel in PT, than Agtr1aflox/flox mice. Whole-cell recording also demonstrated that the membrane potential in PT of Ks-AT1aR-KO mice was lesser negative than Agtr1aflox/flox mice. The expression of Kir4.1 and Kir5.1, Kir4.1/Kir5.1-mediated K+ currents of DCT and DCT membrane potential in Ks-AT1aR-KO mice, were similar to Agtr1aflox/flox mice. However, angiotensin II perfusion for 7 days hyperpolarized the membrane potential in PT and DCT of the control mice but not in Ks-AT1aR-KO mice, while angiotensin II perfusion did not change the expression of Kir4.1, Kir4.2, and Kir5.1. Deletion of AT1aR did not significantly affect the expression of αENaC (epithelial Na+ channel) and ßENaC but increased cleaved γENaC expression. Patch-clamp experiments demonstrated that deletion of AT1aR increased amiloride-sensitive Na+-currents in the cortical-collecting duct but not in late-DCT. However, tertiapin-Q sensitive renal outer medullary potassium channel currents were similar in both genotypes. CONCLUSIONS: AT1aR determines the baseline membrane potential of PT by controlling Kir4.2 expression/activity but AT1aR is not required for determining the baseline membrane potential of the DCT and Kir4.1/Kir5.1 activity/expression. However, AT1aR is required for angiotensin II-induced hyperpolarization of basolateral membrane of PT and DCT. Deletion of AT1aR had no effect on baseline renal outer medullary potassium channel activity but increased ENaC activity in the CCD.
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Canales de Potasio de Rectificación Interna , Receptor de Angiotensina Tipo 1 , Animales , Ratones , Angiotensina II/farmacología , Angiotensina II/metabolismo , Túbulos Renales/metabolismo , Túbulos Renales Distales/metabolismo , Ratones Noqueados , Potasio/metabolismo , Canales de Potasio de Rectificación Interna/genética , Canales de Potasio de Rectificación Interna/metabolismo , Receptor de Angiotensina Tipo 1/genética , Receptor de Angiotensina Tipo 1/metabolismo , Sodio/metabolismo , Canales Epiteliales de SodioRESUMEN
Excessive salt intake raises blood pressure, but the implications of this observation for human health have remained contentious. It has also been recognized for many years that potassium intake may mitigate the effects of salt intake on blood pressure and possibly on outcomes such as stroke. Recent large randomized intervention trials have provided strong support for the benefits of replacing salt (NaCl) with salt substitute (75% NaCl, 25% KCl) on hard outcomes, including stroke. During the same period of time, major advances have been made in understanding how the body senses and tastes salt, and how these sensations drive intake. Additionally, new insights into the complex interactions between systems that control sodium and potassium excretion by the kidneys, and the brain have highlighted the existence of a potassium switch in the kidney distal nephron. This switch seems to contribute importantly to the blood pressure-lowering effects of potassium intake. In recognition of these evolving data, the United States Food and Drug Administration is moving to permit potassium-containing salt substitutes in food manufacturing. Given that previous attempts to reduce salt consumption have not been successful, this new approach has a chance of improving health and ending the 'Salt Wars'.
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Hipertensión , Sodio en la Dieta , Accidente Cerebrovascular , Humanos , Sodio en la Dieta/farmacología , Cloruro de Sodio Dietético/efectos adversos , Hipertensión/etiología , Hipertensión/prevención & control , Cloruro de Sodio , Presión Sanguínea/fisiología , Potasio , Potasio en la Dieta/farmacologíaRESUMEN
SIGNIFICANCE STATEMENT: The effect of sodium-glucose cotransporter-2 inhibitors (SGLT2i) on regional tubular sodium handling is poorly understood in humans. In this study, empagliflozin substantially decreased lithium reabsorption in the proximal tubule (PT) (a marker of proximal tubular sodium reabsorption), a magnitude out of proportion to that expected with only inhibition of sodium-glucose cotransporter-2. This finding was not driven by an "osmotic diuretic" effect; however, several parameters changed in a manner consistent with inhibition of the sodium-hydrogen exchanger 3. The large changes in proximal tubular handling were acutely buffered by increased reabsorption in both the loop of Henle and the distal nephron, resulting in the observed modest acute natriuresis with these agents. After 14 days of empagliflozin, natriuresis waned due to increased reabsorption in the PT and/or loop of Henle. These findings confirm in humans that SGLT2i have complex and important effects on renal tubular solute handling. BACKGROUND: The effect of SGLT2i on regional tubular sodium handling is poorly understood in humans but may be important for the cardiorenal benefits. METHODS: This study used a previously reported randomized, placebo-controlled crossover study of empagliflozin 10 mg daily in patients with diabetes and heart failure. Sodium handling in the PT, loop of Henle (loop), and distal nephron was assessed at baseline and day 14 using fractional excretion of lithium (FELi), capturing PT/loop sodium reabsorption. Assessments were made with and without antagonism of sodium reabsorption through the loop using bumetanide. RESULTS: Empagliflozin resulted in a large decrease in sodium reabsorption in the PT (increase in FELi=7.5%±10.6%, P = 0.001), with several observations suggesting inhibition of PT sodium hydrogen exchanger 3. In the absence of renal compensation, this would be expected to result in approximately 40 g of sodium excretion/24 hours with normal kidney function. However, rapid tubular compensation occurred with increased sodium reabsorption both in the loop ( P < 0.001) and distal nephron ( P < 0.001). Inhibition of sodium-glucose cotransporter-2 did not attenuate over 14 days of empagliflozin ( P = 0.14). However, there were significant reductions in FELi ( P = 0.009), fractional excretion of sodium ( P = 0.004), and absolute fractional distal sodium reabsorption ( P = 0.036), indicating that chronic adaptation to SGLT2i results primarily from increased reabsorption in the loop and/or PT. CONCLUSIONS: Empagliflozin caused substantial redistribution of intrarenal sodium delivery and reabsorption, providing mechanistic substrate to explain some of the benefits of this class. Importantly, the large increase in sodium exit from the PT was balanced by distal compensation, consistent with SGLT2i excellent safety profile. CLINICAL TRIAL REGISTRY NAME AND REGISTRATION NUMBER: ClinicalTrials.gov ( NCT03027960 ).
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Compuestos de Bencidrilo , Glucósidos , Insuficiencia Cardíaca , Inhibidores del Cotransportador de Sodio-Glucosa 2 , Humanos , Sodio , Inhibidores del Cotransportador de Sodio-Glucosa 2/farmacología , Inhibidores del Cotransportador de Sodio-Glucosa 2/uso terapéutico , Litio , Estudios Cruzados , Nefronas , Insuficiencia Cardíaca/tratamiento farmacológico , Diuréticos , GlucosaRESUMEN
Vasopressin regulates water homeostasis via the V2 receptor in the kidney at least in part through protein kinase A (PKA) activation. Vasopressin, through an unknown pathway, upregulates the activity and phosphorylation of Na+-Cl- cotransporter (NCC) and Na+-K+-2Cl- cotransporter 2 (NKCC2) by Ste20-related proline/alanine-rich kinase (SPAK) and oxidative stress-responsive kinase 1 (OSR1), which are regulated by the with-no-lysine kinase (WNK) family. Phosphorylation of WNK4 at PKA consensus motifs may be involved. Inhibitor 1 (I1), a protein phosphatase 1 (PP1) inhibitor, may also play a role. In human embryonic kidney (HEK)-293 cells, we assessed the phosphorylation of WNK4, SPAK, NCC, or NKCC2 in response to forskolin or desmopressin. WNK4 and cotransporter phosphorylation were studied in desmopressin-infused WNK4-/- mice and in tubule suspensions. In HEK-293 cells, only wild-type WNK4 but not WNK1, WNK3, or a WNK4 mutant lacking PKA phosphorylation motifs could upregulate SPAK or cotransporter phosphorylation in response to forskolin or desmopressin. I1 transfection maximized SPAK phosphorylation in response to forskolin in the presence of WNK4 but not of mutant WNK4 lacking PP1 regulation. We observed direct PP1 regulation of NKCC2 dephosphorylation but not of NCC or SPAK in the absence of WNK4. WNK4-/- mice with desmopressin treatment did not increase SPAK/OSR1, NCC, or NKCC2 phosphorylation. In stimulated tubule suspensions from WNK4-/- mice, upregulation of pNKCC2 was reduced, whereas upregulation of SPAK phosphorylation was absent. These findings suggest that WNK4 is a central node in which kinase and phosphatase signaling converge to connect cAMP signaling to the SPAK/OSR1-NCC/NKCC2 pathway.NEW & NOTEWORTHY With-no-lysine kinases regulate the phosphorylation and activity of the Na+-Cl- and Na+-K+-2Cl- cotransporters. This pathway is modulated by arginine vasopressin (AVP). However, the link between AVP and WNK signaling remains unknown. Here, we show that AVP activates WNK4 through increased phosphorylation at putative protein kinase A-regulated sites and decreases its dephosphorylation by protein phosphatase 1. This work increases our understanding of the signaling pathways mediating AVP actions in the kidney.
Asunto(s)
Arginina Vasopresina , Proteínas Serina-Treonina Quinasas , Ratones , Humanos , Animales , Fosforilación , Proteínas Serina-Treonina Quinasas/metabolismo , Células HEK293 , Arginina Vasopresina/metabolismo , Cotransportadores de K Cl , Desamino Arginina Vasopresina , Colforsina , Proteína Fosfatasa 1/metabolismo , Riñón/metabolismo , Miembro 3 de la Familia de Transportadores de Soluto 12/metabolismo , Proteínas Quinasas Dependientes de AMP Cíclico/metabolismoRESUMEN
Introduction: The putative "renal-K switch" mechanism links dietary potassium intake with sodium retention and involves activation of the sodium chloride (NaCl) cotransporter (NCC) in the distal convoluted tubule in response to low potassium intake, and suppression in response to high potassium intake. This study examined NCC abundance and phosphorylation (phosphorylated NCC [pNCC]) in urinary extracellular vesicles (uEVs) isolated from healthy adults on a high sodium diet to determine tubular responses to alteration in potassium chloride (KCl) intake. Methods: Healthy adults maintained on a high sodium (â¼4.5 g [200 mmol]/d) low potassium (â¼2.3 g [60 mmol]/d) diet underwent a 5-day run-in period followed by a crossover study, with 5-day supplementary KCl (active phase, Span-K 3 tablets (potassium 24 mmol) thrice daily) or 5-day placebo administrated in random order and separated by 2-day washout. Ambulatory blood pressure (BP) and biochemistries were assessed, and uEVs were analyzed by western blotting. Results: Among the 18 participants who met analysis criteria, supplementary KCl administration (vs. placebo) was associated with markedly higher levels of plasma potassium and 24-hour urine excretion of potassium, chloride, and aldosterone. KCl supplementation was associated with lower uEV levels of NCC (median fold change (KCl/Placebo) = 0.74 [0.30-1.69], P < 0.01) and pNCC (fold change (KCl/Placebo) = 0.81 [0.19-1.75], P < 0.05). Plasma potassium inversely correlated with uEV NCC (R2 = 0.11, P = 0.05). Conclusions: The lower NCC and pNCC in uEVs in response to oral KCl supplementation provide evidence to support the hypothesis of a functional "renal-K switch" in healthy human subjects.