Thirty years of the NaCl cotransporter: from cloning to physiology and structure.

The primary structure of the thiazide-sensitive NaCl cotransporter (NCC) was resolved 30 years ago by the molecular identification of the cDNA encoding this cotransporter, from the winter's flounder urinary bladder, following a functional expression strategy. This review outlines some aspects of how the knowledge about thiazide diuretics and NCC evolved, the history of the cloning process, and the expansion of the SLC12 family of electroneutral cotransporters. The diseases associated with activation or inactivation of NCC are discussed, as well as the molecular model by which the activity of NCC is regulated. The controversies in the field are discussed as well as recent publication of the three-dimensional model of NCC obtained by cryo-electron microscopy, revealing not only the amino acid residues critical for Na+ and Cl- translocation but also the residues critical for polythiazide binding to the transporter, opening the possibility for a new era in thiazide diuretic therapy.

Structure-function relationships in the sodium chloride cotransporter.

The thiazide sensitive Na+:Cl- cotransporter (NCC) is the principal via for salt reabsorption in the apical membrane of the distal convoluted tubule (DCT) in mammals and plays a fundamental role in managing blood pressure. The cotransporter is targeted by thiazide diuretics, a highly prescribed medication that is effective in treating arterial hypertension and edema. NCC was the first member of the electroneutral cation-coupled chloride cotransporter family to be identified at a molecular level. It was cloned from the urinary bladder of the Pseudopleuronectes americanus (winter flounder) 30 years ago. The structural topology, kinetic and pharmacology properties of NCC have been extensively studied, determining that the transmembrane domain (TM) coordinates ion and thiazide binding. Functional and mutational studies have discovered residues involved in the phosphorylation and glycosylation of NCC, particularly on the N-terminal domain, as well as the extracellular loop connected to TM7-8 (EL7-8). In the last decade, single-particle cryogenic electron microscopy (cryo-EM) has permitted the visualization of structures at high atomic resolution for six members of the SLC12 family (NCC, NKCC1, KCC1-KCC4). Cryo-EM insights of NCC confirm an inverted conformation of the TM1-5 and TM6-10 regions, a characteristic also found in the amino acid-polyamine-organocation (APC) superfamily, in which TM1 and TM6 clearly coordinate ion binding. The high-resolution structure also displays two glycosylation sites (N-406 and N-426) in EL7-8 that are essential for NCC expression and function. In this review, we briefly describe the studies related to the structure-function relationship of NCC, beginning with the first biochemical/functional studies up to the recent cryo-EM structure obtained, to acquire an overall view enriched with the structural and functional aspects of the cotransporter.

The European and Japanese eel NaCl cotransporters ß exhibit chloride currents and are resistant to thiazide type diuretics.

The thiazide-sensitive Na+-Cl- cotransporter (NCC) is the major pathway for salt reabsorption in the mammalian distal convoluted tubule, and the inhibition of its function with thiazides is widely used for the treatment of arterial hypertension. In mammals and teleosts, NCC is present as one ortholog that is mainly expressed in the kidney. One exception, however, is the eel, which has two genes encoding NCC. The eNCCα is located in the kidney and eNCCß, which is present in the apical membrane of the rectum. Interestingly, the European eNCCß functions as a Na+-Cl- cotransporter that is nevertheless resistant to thiazides and is not activated by low-chloride hypotonic stress. However, in the Japanese eel rectal sac, a thiazide-sensitive NaCl transport mechanism has been described. The protein sequences between eNCCß and jNCCß are 98% identical. Here, by site-directed mutagenesis, we transformed eNCCß into jNCCß. Our data showed that jNCCß, similar to eNCCß, is resistant to thiazides. In addition, both NCCß proteins have high transport capacity with respect to their renal NCC orthologs and, in contrast to known NCCs, exhibit electrogenic properties that are reduced when residue I172 is substituted by A, G, or M. This is considered a key residue for the chloride ion-binding sites of NKCC and KCC. We conclude that NCCß proteins are not sensitive to thiazides and have electrogenic properties dependent on Cl-, and site I172 is important for the function of NCCß.

Thiazide diuretics alone or in combination with a potassium-sparing diuretic on blood pressure-lowering in patients with primary hypertension: protocol for a systematic review and network meta-analysis.

BACKGROUND: The use of thiazide (T) diuretics for the treatment of hypertension may be associated with adverse metabolic effects, which can be minimized by combining thiazides with potassium-sparing (PS) diuretics. The additional blood pressure (BP)-lowering effect provided by the addition of a PS diuretic is unclear. Due to a large number of drugs in the T diuretics class, and the possible difference between them, there is a need to identify the best available evidence for health decision-making. This systematic review with network meta-analysis aims to compare the antihypertensive efficacy of T diuretics alone or in combination with a PS diuretic in patients with primary hypertension, as well as the safety of such drugs through the measurement of drug-related adverse events. METHODS: A comprehensive electronic search will be conducted in six electronic bibliographic databases (PubMed/MEDLINE, Cochrane Library, Embase, Web of Science, Scopus, Lilacs), a registration database ( ClinicalTrials.gov ), and Educational Resources Information Center (ERIC [ProQuest]), published from inception to the date of the search. The search will be updated towards the end of the review. A hand search of the reference sections of the included studies and cited studies will also be performed. In case of missing data, authors will be contacted by e-mail or academic social networking sites whenever possible. To be included in the review, studies must be double-blind randomized controlled trials evaluating T diuretics alone or in combination with PS diuretics in patients with primary hypertension. The primary outcome measure will be office BP. Ambulatory BP monitoring (ABPM), non-melanoma skin cancer, major adverse cardiovascular events, laboratory parameters, and the number of withdrawals will be included as secondary outcomes. The results will be quantitatively summarized using differences between the mean change from baseline or differences between means for quantitative outcomes and relative risk for dichotomous outcomes. Results will be presented as mean or relative risk with credible intervals through a league table. The treatments will also be ranked using the surface under the cumulative ranking curve method. The risk of bias will be assessed through the RoB 1.0 tool. DISCUSSION: To the best of our knowledge, this review will be the first to synthesize currently available evidence on the antihypertensive efficacy of different T diuretics alone or in combination with PS diuretics in adults with hypertension. The goals of hypertension treatment are to control high BP and to reduce associated cardiovascular morbidity and mortality, using the most appropriate therapy. Thiazides are widely used for pharmacological treatment due to their demonstrated effectiveness in reducing BP, favorable safety profile, and low cost. The results of this study will provide evidence regarding the best therapeutic strategies with T and PS diuretics, evidencing interventions with better antihypertensive efficacy and safety profile. TRIAL REGISTRATION: This systematic review and network meta-analysis was prospectively registered at the PROSPERO database ( CRD42018118492 ).

A hipopotassemia como efeito adverso dos diuréticos tiazídicos / Hypopotasemia as an adverse effect of thizide diuretics

O potássio tem função fisiológica fundamental no volume intracelular e na manutenção funcional de nervos e músculos. Distúrbios do potássio são comuns e estão associados a aumento na mortalidade nos portadores de doenças cardiovasculares, entre elas a hipertensão arterial. Assim a manutenção de um equilíbrio entre o potássio intra e extracelular é de fundamental importância para nervos, músculos e o sistema cardiovascular. Há décadas os diuréticos tiazídicos são uma das principais drogas utilizadas no tratamento da hipertensão arterial. Entre suas principais reações adversas relacionam-se os distúrbios eletrolíticos e metabólicos, os quais se tornaram menos frequentes com o uso de doses menores do que as habitualmente empregadas no seu início. Neste artigo os principais efeitos adversos do uso crônico dos diuréticos tiazídicos bem como suas consequências serão discutidos.

Potassium has a fundamental physiological function without intracellular volume and in the functional maintenance of nerves and muscles. Potassium disorders are common and are associated with increased mortality in patients with cardiovascular diseases, including hypertension. Thus, maintaining a balance between intracellular and extracellular potassium is of fundamental importance for the nerves, muscles and cardiovascular system. Thiazide diuretics have been one of the main drugs used in the treatment of hypertension for decades. Among its main adverse reactions are related electrolyte and metabolic disturbances, which become less frequent with the use of lower doses than those usually used at the beginning. In this article, the main adverse effects of the chronic use of thiazide diuretics as well as their consequences will be discussed.

[Severe and rare adverse reaction to hydrochlorothiazide]. / Reacción grave e infrecuente con hidroclorotiazida.

BACKGROUND: The immune mechanism involved in the reaction to hydrochlorothiazide, which is widely used to control hypertension, is unknown. The short latency period between the take of the drug and the onset of symptoms suggests immediate hypersensitivity. CASE REPORT: 63-year-old woman with arterial hypertension who, on three occasions, experienced nausea, vomiting, general malaise, shivering, arthralgias, dysthermic sensation, back pain of mechanical characteristics and mild non-productive cough, as well as fever and chest tightness with increased dyspnea and desaturation of up to 88 %, after taking hydrochlorothiazide. CONCLUSIONS: Clinical presentation in the patient was similar to a septic shock, which is a rare allergic reaction. The diagnosis has to be clinical. This type of reaction might be due to type III hypersensitivity owing to the formation of immune complexes. Avoiding of the culprit drug is key to a good evolution.

Antecedentes: Se desconoce el mecanismo inmunológico implicado en la reacción a la hidroclorotiazida, de amplio uso para el control de la hipertensión arterial. El corto periodo de latencia entre la toma del fármaco y la aparición de síntomas sugiere hipersensibilidad inmediata. Reporte de caso: Mujer de 63 años con hipertensión arterial quien en tres ocasiones presentó náuseas, vómitos, malestar general, tiritona, artralgias, sensación distérmica, dolor lumbar de características mecánicas y tos escasa no productiva, así como fiebre y opresión torácica con incremento de la disnea y desaturación hasta de 88 %, tras la toma de hidroclorotiazida. Conclusiones: La presentación clínica en la paciente fue similar a choque séptico, reacción alérgica rara cuyo diagnóstico es clínico Este tipo de reacción podría deberse a hipersensibilidad tipo III debido a la formación de inmunocomplejos. Evitar el fármaco implicado es clave para la buena evolución.

El metabolismo de la glucosa en pacientes con hipertensión arterial / Glucose metabolism in hypertension patients

Thiazide diuretics (TD) are recommended as first-line therapy in uncomplicated hypertension by several professional organizations. However, they also may pose a risk of glucose metabolism abnormalities in certain individuals. Early studies showed TD cause a small increase in fasting glucose. These effects may be related to exacerbation of insulin resistance as insulin blood levels increased. It could be postulated that long-term use may result in a higher risk of developing diabetes. This was not seen in the Systolic Hypertension in the Elderly study which used low doses of chlorthalidone but an increase in the odds of developing diabetes was demonstrated for chlorthalidone in comparison to lisinopril or amlodipine in the ALLHAT study. Nonetheless, in ALLHAT there was no increased risk of adverse cardiovascular outcomes. In addition, use of chlorthalidone in the ALLHAT study in patients with pre-existing diabetes maintained the same advantage in lower stroke rate versus lisinopril and lower heart failure rate versus amlodipine or lisinopril. Other factors that may play a role in thiazide-induced glucose elevation are potassium levels and weight. In a meta-analysis of 59 trials a correlation existed for lower potassium levels and higher fasting glucose. pidemiological studies suggest that elevated BMI and the level of pre-thiazide fasting glucose predict glucose elevation and new onset diabetes after thiazide therapy. Patients with a BMI over 32.3 kg/m2 had a 6.5% risk of developing diabetes. Whether co-administration of a thiazide diuretic with other classes of antihypertensives modulates the glucose alteration remains unknown. Studies suggest combination with valsartan may reduce the effect perhaps by conserving potassium. Practical implications of these observations would suggest reserving thiazide diuretics to later stages in treatment for patients who are obese, particularly if they have fasting blood glucoses in the pre-diabetic range. However, for the majority of patients thiazide diuretics remain an excellent choice given their long track record of safety and beneficial long-term cardiovascular outcomes

Los diuréticos tiazídicos (DT) se recomiendan como tratamiento de primera línea para la hipertensión no complicada, por varias organizaciones profesionales. Sin embargo, también pueden suponer un riesgo de alteraciones del metabolismo de la glucosa en ciertos individuos. Los primeros estudios mostraron que los DT causan un pequeño aumento de la glucemia en ayunas. Estos efectos pueden estar relacionados con la exacerbación de la resistencia a la insulina y los niveles de insulina plasmáticos están incrementados. Se podría postular que el uso a largo plazo puede resultar en un mayor riesgo de presentar diabetes. Esto no se observó en el estudio Systolic Hypertension in the Elderly, realizado con adultos mayores que utilizaban bajas dosis de clortalidona; sin embargo, un aumento en las probabilidades de contraer diabetes fue demostrado por el uso de clortalidona en comparación con lisinopril y amlodipina en el estudio ALLHAT. No obstante, en el ALLHAT no hubo mayor riesgo de eventos cardiovasculares adversos. Además, el uso de clortalidona en el estudio ALLHAT en pacientes con diabetes preexistente mantuvo la misma ventaja en la baja tasa de accidentes cerebrovasculares, en comparación con lisinopril, y la menor tasa de paro cardíaco, en comparación con amlodipina o lisinopril. Otros factores que pueden desempeñar un papel en la elevación de la glucosa inducida por tiazidas son los niveles de potasio y el peso del paciente. En un metanálisis de 59 ensayos se encontró una correlación entre los niveles de potasio más bajos y los niveles más elevados de glucemia en ayunas. Los estudios epidemiológicos sugieren que el índice de masa corporal (IMC) elevado y el nivel de la glucemia previo al tratamiento con tiazidas pueden predecir la elevación de la glucosa y la diabetes de nueva aparición después de la terapia con tiazidas. Los pacientes con un IMC superior a 32.3 kg/m2 tenían un riesgo de 6.5% de presentar diabetes. Se desconoce aún si la administración de un diurético tiazídico con otras clases de antihipertensivos modula la alteración de la glucosa. Los estudios sugieren que la combinación con valsartán puede reducir el efecto, quizá mediante la conservación del potasio. Las repercusiones prácticas de estas observaciones sugieren reservar los diuréticos tiazídicos para etapas posteriores del tratamiento para los pacientes que son obesos, sobre todo si han presentado glucemia en ayunas en el rango de prediabetes. Sin embargo, para la mayoría de los pacientes, los diuréticos tiazídicos siguen siendo una excelente opción dado su largo historial de seguridad y los resultados cardiovasculares beneficiosos a largo plazo

Inequalities in prescription of hydrochlorothiazide for diabetic hypertensive patients in Colombia / Desigualdades en la prescripción de hidroclorotiazida en pacientes hipertensos diabéticos en Colombia

Objective Evaluating differences in the suitable prescription of thiazides in hypertense patients, according to affiliation regime. Materials and methods This was an analytical cross-sectional study. The database from a previous study was used regarding two groups of hypertense patients (subsidised regime and contributory regime) who had attended out-patient consultation between 01-09-2007 and 29-02-2008. Ideal therapy was evaluated in both groups. Univariate and multivariate analysis was carried out. Results 136 patients (contributory: 41.9 percent; subsidised: 58.1 percent). Subsidised regime patients were older (mean=68.8±10) than those from the contributory regime (mean=64.1±11.1) (t-test, p=0.0110). Prescribing antihypertensive drugs was ideal in 49/136 of the patients (36.0 percent). Ideal prescription accounted for 24/79 (30 percent) of the patients in the subsidised regime and 25/57 (43.8 percent) in the contributory one (OR=1.79; 95 percent CI:0.88-3.64). Older people (aged ≥ 65yo) were at risk of receiving a non-ideal prescription (OR=2.12; 95 percentCI:1.02-4.38) whilst this was not so in the subsidised regime (OR=1.62; 95 percent CI:0.78-3.35). Conclusions Ideal prescription of antihypertensive drugs was low in the population being studied. There were differences regarding age ideal prescription but not concerning affiliation regime. It is suggested that a longitudinal study be carried out in the future.

Objetivo Evaluar las diferencias en la adecuada prescripción de tiazidas en pacientes hipertensos, según régimen de afiliación. Materiales y métodos Estudio de corte transversal analítico. Se utilizó la base de datos de un estudio previo, dos grupos de pacientes hipertensos: régimen subsidiado y régimen contributivo que asistieron a consulta externa entre el 01-09-2007 y el 29-02-2008. Se evaluó terapia ideal en los dos grupos. Se realizó análisis univariado y multivariado. Resultados Se estudiaron 136 pacientes (contributivo: 41,9 por ciento; subsidiado: 58,1 por ciento). Los pacientes del régimen subsidiado fueron mayores (promedio= 68,8±10) que los del contributivo (promedio=64,1±11.1) (t-test, p=0,0110). La prescripción de antihipertensivos fue ideal en 49/136 (36,0 por ciento). En el régimen subsidiado la prescripción fue ideal en 24/79 (30 por ciento) y en el contributivo en 25/57 (43,8 por ciento) (OR: 1,79 IC95 por ciento (0,88-3,64)). La edad ≥65años fue riesgo de prescripción no ideal (OR: 2.12, IC95 por ciento(1,02-4,38)), mientras que no lo fue estar en el régimen subsidiado (OR=1,62, IC95 por ciento(0,78-3,35). Conclusiones La prescripción ideal de antihipertensivos es baja. Hay diferencias en la edad, en la prescripción ideal, mas no por régimen de afiliación. Se sugiere un estudio longitudinal en el futuro.

Magnésio mononuclear em hipertensos idosos tratados com tiazídico / Mononuclear magnesium in aged hypertensive patients treated with thiazide

Purpose­To study mononuclear magnesium and serum cations (Na, K and Mg) in elderly hypertensive patients treated with hydrochlorothiazide during 90 days. Patients and Methods­ 15 elderly hypertensive patients treated with hydrochlorothiazide, 25 mg/day or placebo. A method of freezing produced total Iysis of the cells; Mg was measured by atomic spectrophotometry. Results­No differences were noted in mononuclear or serum magnesium in the thiazide or placebo treated patients, and the diuretic produced significant decreases in supine systolic and diastolic blood pressure. Conclusion­Magnesium supplementation does not seem essencial in most patients in this conditions