Decreased renal function increases the nighttime urine volume rate by carryover of salt excretion to the nighttime

To determine the pathophysiology of nocturnal polyuria associated with renal dysfunction, patients who underwent laparoscopic nephrectomy were prospectively studied. The diurnal variation in urine volume, osmolality, and salt excretion were measured on preoperative day 2 and postoperative day 7. The factors associated with an increase in the nighttime urine volume rate with decreased renal function were evaluated using multiple linear regression analysis. Forty-nine patients were included. The estimated glomerular filtration rate decreased from 73.3 ± 2.0 to 47.2 ± 1.6 mL/min/1.73 m2 (P < 0.01) and the nighttime urine volume rate increased from 40.6% ± 2.0% to 45.3% ± 1.5% (P = 0.04) with nephrectomy. The nighttime urine osmolality decreased from 273 ± 15 to 212 ± 10 mOsm/kg and the nighttime salt excretion rate increased from 38.7% ± 2.1% to 48.8% ± 1.7% (both P < 0.01) with nephrectomy. Multiple linear regression analysis showed that the increase in the nighttime urine volume rate was strongly affected by the increase in the nighttime salt excretion rate. A decrease in renal function causes an increase in the nighttime urine volume rate, mainly because of an increase in nighttime salt excretion.Trial registration number: UMIN000036760 (University Hospital Medical Information Network Clinical Trials Registry).Date of registration: From 1 June 2019 to 31 October 2020.

Proteinuria changes in kidney disease patients with clinical remission during the COVID-19 pandemic

Backgrounds Data on how lifestyle changes due to the coronavirus disease 2019 (COVID-19) pandemic have influenced the clinical features of kidney disease patients remain scarce. Methods This study retrospectively analyzed clinical variables in patients with stage G1–G4 chronic kidney disease (CKD) with complete or incomplete remission of proteinuria, who were managed in a nephrology outpatient clinic of a university hospital in Tokyo. The clinical variables during the COVID-19 pandemic (term 1, June–July 2020) were compared to those one year before the pandemic (term 0, June–July 2019). The urinary protein excretion (UPE) was used as the primary outcome measure. Results This study included 325 patients with stage G1–G4 CKD (mean age 58.5 years old, 37.5% female, 80.6% on renin-angiotensin aldosterone system inhibitors [RAASis], 12.0% on maintenance dose immunosuppression therapy) evaluated at term 0. The UPE at terms 0 and 1 was 247 (92–624) and 203 (84–508) mg/day [median (25th–75th percentile)], respectively; the value in term 1 was 18% lower than that in term 0 (p<0.001), with no marked difference in body weight, blood pressure, protein intake or urinary salt excretion. In multivariable analyses, incomplete remission of proteinuria in term 0 (odds ratio [OR] = 2.70, p = <0.001), RAASi use (OR = 2.09, p = 0.02) and decreased urinary salt excretion in term 1 vs. term 0 (OR = 1.94, p = 0.002) were identified as independent variables associated with reduced UPE in term 1 vs. term 0. No significant interactions between the variables were observed. Conclusion In kidney disease patients receiving standard medical care from nephrologists, the UPE after the emergency declaration in relation to the COVID-19 pandemic was lower than before the declaration. The UPE reduction may be associated with reduced dietary salt intake during the pandemic in patients treated with RAASi for insufficient control of proteinuria. Our results support the current proposal to continue therapeutic approaches to these patients, which involve RAASi therapy along with optimizing dietary habits, even while dealing with the COVID-19 pandemic.

Decreased renal function increases the nighttime urine volume rate by carryover of salt excretion to the nighttime

Purpose: To determine the pathophysiology of nocturnal polyuria associated with renal dysfunction.Methods: Patients who underwent laparoscopic nephrectomy were studied prospectively. The diurnal variation in urine volume, osmolality, and salt excretion were measured on preoperative day two and postoperative day seven. The factors associated with an increase in the nighttime urine volume rate with decreased renal function were evaluated by multiple linear regression analysis.Results: Forty-nine patients were included. The eGFR decreased from 73.3 ± 2.0 to 47.2 ± 1.6 mL/min/1.73 m2 (P < 0.01) and the nighttime urine volume rate increased from 40.6% ± 2.0% to 45.3% ± 1.5% (P = 0.04) with nephrectomy. The nighttime urine osmolality decreased from 273 ± 15 to 212 ± 10 mOsm/kg (P < 0.01) and the nighttime salt excretion rate increased from 38.7% ± 2.1% to 48.8% ± 1.7% (P < 0.01) with nephrectomy. Multiple linear regression analysis revealed that the increase in the nighttime urine volume rate was strongly affected by the increase in the nighttime salt excretion rate.Conclusion: A decrease in renal function causes an increase in the nighttime urine volume rate, mainly due to an increase in nighttime salt excretion.Trial registration number: UMIN000036760 (University Hospital Medical Information Network Clinical Trials Registry)Date of registration: From June 1st, 2019 to October 31th 2020

The protease corin regulates electrolyte homeostasis in eccrine sweat glands

Sweating is a basic skin function in body temperature control. In sweat glands, salt excretion and reabsorption are regulated to avoid electrolyte imbalance. To date, the mechanism underlying such regulation is not fully understood. Corin is a transmembrane protease that activates atrial natriuretic peptide (ANP), a cardiac hormone essential for normal blood volume and pressure. Here, we report an unexpected role of corin in sweat glands to promote sweat and salt excretion in regulating electrolyte homeostasis. In human and mouse eccrine sweat glands, corin and ANP are expressed in the luminal epithelial cells. In corin-deficient mice on normal- and high-salt diets, sweat and salt excretion is reduced. This phenotype is associated with enhanced epithelial sodium channel (ENaC) activity that mediates Na+ and water reabsorption. Treatment of amiloride, an ENaC inhibitor, normalizes sweat and salt excretion in corin-deficient mice. Moreover, treatment of aldosterone decreases sweat and salt excretion in wild-type (WT), but not corin-deficient, mice. These results reveal an important regulatory function of corin in eccrine sweat glands to promote sweat and salt excretion.

Sodium Handling and Interaction in Numerous Organs

Salt (NaCl) is a prerequisite for life. Excessive intake of salt, however, is said to increase disease risk, including hypertension, arteriosclerosis, heart failure, renal disease, stroke, and cancer. Therefore, considerable research has been expended on the mechanism of sodium handling based on the current concepts of sodium balance. The studies have necessarily relied on relatively short-term experiments and focused on extremes of salt intake in humans. Ultra-long-term salt balance has received far less attention. We performed long-term salt balance studies at intakes of 6, 9, and 12 g/day and found that although the kidney remains the long-term excretory gate, tissue and plasma sodium concentrations are not necessarily the same and that urinary salt excretion does not necessarily reflect total-body salt content. We found that to excrete salt, the body makes a great effort to conserve water, resulting in a natriuretic-ureotelic principle of salt excretion. Of note, renal sodium handling is characterized by osmolyte excretion with anti-parallel water reabsorption, a state-of-affairs that is achieved through the interaction of multiple organs. In this review, we discuss novel sodium and water balance concepts in reference to our ultra-long-term study. An important key to understanding body sodium metabolism is to focus on water conservation, a biological principle to protect from dehydration, since excess dietary salt excretion into the urine predisposes to renal water loss because of natriuresis. We believe that our research direction is relevant not only to salt balance but also to cardiovascular regulatory mechanisms.