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The Urinary Excretion of Uromodulin is Regulated by the Potassium Channel ROMK.

ABSTRACT: Uromodulin, the most abundant protein in normal urine, is produced by cells lining the thick ascending limb (TAL) of the loop of Henle. Uromodulin regulates the activity of the potassium channel ROMK in TAL cells. Common variants in KCNJ1, the gene encoding ROMK, are associated with urinary levels of uromodulin in population studies. Here, we investigated the functional link between ROMK and uromodulin in Kcnj1 knock-out mouse models, in primary cultures of mouse TAL (mTAL) cells, and in patients with Bartter syndrome due to KCNJ1 mutations. Both global and kidney-specific Kcnj1 knock-out mice showed reduced urinary levels of uromodulin paralleled by increased levels in the kidney, compared to wild-type controls. Pharmacological inhibition and genetic deletion of ROMK in mTAL cells caused a reduction in apical uromodulin excretion, reflected by cellular accumulation. In contrast, NKCC2 inhibition showed no effect on uromodulin processing. Patients with Bartter syndrome type 2 showed reduced urinary uromodulin levels compared to age and gender matched controls. These results demonstrate that ROMK directly regulates processing and release of uromodulin by TAL cells, independently from NKCC2. They support the functional link between transport activity and uromodulin in the TAL, relevant for blood pressure control and urinary concentrating ability.

SUBMITTER: Schiano G

PROVIDER: S-EPMC6925250 | biostudies-literature | 2019 Dec

REPOSITORIES: biostudies-literature

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The Urinary Excretion of Uromodulin is Regulated by the Potassium Channel ROMK.

Schiano Guglielmo G Glaudemans Bob B Olinger Eric E Goelz Nadine N Müller Michael M Loffing-Cueni Dominique D Deschenes Georges G Loffing Johannes J Devuyst Olivier O

Scientific reports 20191220 1

Uromodulin, the most abundant protein in normal urine, is produced by cells lining the thick ascending limb (TAL) of the loop of Henle. Uromodulin regulates the activity of the potassium channel ROMK in TAL cells. Common variants in KCNJ1, the gene encoding ROMK, are associated with urinary levels of uromodulin in population studies. Here, we investigated the functional link between ROMK and uromodulin in Kcnj1 knock-out mouse models, in primary cultures of mouse TAL (mTAL) cells, and in patient ...[more]

PMID: 31863061

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Project description:ImportanceIn 2010, the Institute of Medicine (now the National Academy of Medicine) recommended collecting 24-hour urine to estimate US sodium intake because previous studies indicated 90% of sodium consumed was excreted in urine.ObjectiveTo estimate mean population sodium intake and describe urinary potassium excretion among US adults.Design, setting, and participantsIn a nationally representative cross-sectional survey of the US noninstitutionalized population, 827 of 1103 (75%) randomly selected, nonpregnant participants aged 20 to 69 years in the examination component of the National Health and Nutrition Examination Survey (NHANES) collected at least one 24-hour urine specimen in 2014. The overall survey response rate for the 24-hour urine collection was approximately 50% (75% [24-hour urine component response rate] × 66% [examination component response rate]).Exposures24-hour collection of urine.Main outcomes and measuresMean 24-hour urinary sodium and potassium excretion. Weighted national estimates of demographic and health characteristics and mean electrolyte excretion accounting for the complex survey design, selection probabilities, and nonresponse.ResultsThe study sample (n = 827) represented a population of whom 48.8% were men; 63.7% were non-Hispanic white, 15.8% Hispanic, 11.9% non-Hispanic black, and 5.6% non-Hispanic Asian; 43.5% had hypertension (according to 2017 hypertension guidelines); and 10.0% reported a diagnosis of diabetes. Overall mean 24-hour urinary sodium excretion was 3608 mg (95% CI, 3414-3803). The overall median was 3320 mg (interquartile range, 2308-4524). In secondary analyses by sex, mean sodium excretion was 4205 mg (95% CI, 3959-4452) in men (n = 421) and 3039 mg (95% CI, 2844-3234) in women (n = 406). By age group, mean sodium excretion was 3699 mg (95% CI, 3449-3949) in adults aged 20 to 44 years (n = 432) and 3507 mg (95% CI, 3266-3748) in adults aged 45 to 69 years (n = 395). Overall mean 24-hour urinary potassium excretion was 2155 mg (95% CI, 2030-2280); by sex, 2399 mg (95% CI, 2253-2545) in men and 1922 mg (95% CI, 1757-2086) in women; and by age, 1986 mg (95% CI, 1878-2094) in adults aged 20 to 44 years and 2343 mg (95% CI, 2151-2534) in adults aged 45 to 69 years.Conclusions and relevanceIn cross-sectional data from a 2014 sample of US adults, estimated mean sodium intake was 3608 mg per day. The findings provide a benchmark for future studies.

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The Urinary Excretion of Uromodulin is Regulated by the Potassium Channel ROMK.

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The Urinary Excretion of Uromodulin is Regulated by the Potassium Channel ROMK.

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