Genome-wide association study of blood pressure extremes identifies variant near UMOD associated with hypertension

Insights into Uromodulin and Blood Pressure

PURPOSE OF REVIEW

We review the role of uromodulin, a protein exclusively expressed in the kidney, in blood pressure regulation and hypertension.

RECENT FINDINGS

The last few years have seen a shift of focus from genetic association to mendelian randomisation and uromodulin-salt interaction studies, thus confirming the causal role of uromodulin in blood pressure regulation and hypertension. This work has been complemented by phenome-wide association studies in a wider range of ethnicities. Important recent molecular work elucidated uromodulin trafficking and secretion and provided more insights into the pathophysiological roles of circulating and urinary uromodulin. Uromodulin has a causal role in blood pressure regulation and hypertensin. Recent studies show utility of the uromodulin as a biomarker and a possible precision medicine application based on genetically determined differential responses to loop diuretics.

UMOD Genotype-Blinded Trial of Ambulatory Blood Pressure Response to Torasemide

BACKGROUND

UMOD (uromodulin) has been linked to hypertension through potential activation of Na+-K+-2Cl- cotransporter (NKCC2), a target of loop diuretics. We posited that hypertensive patients carrying the rs13333226-AA UMOD genotype would demonstrate greater blood pressure responses to loop diuretics, potentially mediated by this UMOD/NKCC2 interaction.

METHODS

This prospective, multicenter, genotype-blinded trial evaluated torasemide (torsemide) efficacy on systolic blood pressure (SBP) reduction over 16 weeks in nondiabetic, hypertensive participants uncontrolled on ≥1 nondiuretic antihypertensive for >3 months. The primary end point was the change in 24-hour ambulatory SBP (ABPM SBP) and SBP response trajectories between baseline and 16 weeks by genotype (AA versus AG/GG) due to nonrandomized groups at baseline (ClinicalTrials.gov: NCT03354897).

RESULTS

Of 251 enrolled participants, 222 received torasemide and 174 demonstrated satisfactory treatment adherence and had genotype data. The study participants were middle-aged (59±11 years), predominantly male (62%), obese (body mass index, 32±7 kg/m2), with normal eGFR (92±17 mL/min/1.73 m²) and an average baseline ABPM of 138/81 mm Hg. Significant reductions in mean ABPM SBP were observed in both groups after 16 weeks (AA, -6.57 mm Hg [95% CI, -8.44 to -4.69]; P<0.0001; AG/GG, -3.22 [95% CI, -5.93 to -0.51]; P=0.021). The change in mean ABPM SBP (baseline to 16 weeks) showed a difference of -3.35 mm Hg ([95% CI, -6.64 to -0.05]; P=0.048) AA versus AG/GG genotypes. The AG/GG group displayed a rebound in SBP from 8 weeks, differing from the consistent decrease in the AA group (P=0.004 for difference in trajectories).

CONCLUSIONS

Our results confirm a plausible interaction between UMOD and NKCC2 and suggest a potential role for genotype-guided use of loop diuretics in hypertension management.

REGISTRATION

URL: https://www.clinicaltrials.gov; Unique identifier: NCT03354897.

Cullin 3/with No Lysine [K] Kinase/Ste20/SPS-Related Proline Alanine Rich Kinase Signaling: Impact on NaCl Cotransporter Activity in BP Regulation

The sodium chloride cotransporter (NCC) fine-tunes Na + balance and indirectly affects the homeostasis of other ions including K + , Mg 2+ , and Ca 2+ . Owing to its effects on Na + balance, BP is significantly affected by alterations in NCC activity. Several factors have been reported to influence the expression and activity of NCC. One critical factor is NCC phosphorylation/dephosphorylation that occurs at key serine-threonine amino acid residues of the protein. Phosphorylation, which results in increased NCC activity, is mediated by the with no lysine [K] (WNK)-SPS-related proline alanine rich kinase (SPAK)/OSR1 kinases. NCC activation stimulates reabsorption of Na + , increasing extracellular fluid volume and hence BP. On the other hand, proteasomal degradation of WNK kinases after ubiquitination by the Cullin 3-Kelch-like 3 E3 ubiquitin ligase complex and dephosphorylation pathways oppose WNK-SPAK/OSR1-mediated NCC activation. Components of the Cullin 3/Kelch-like 3-WNK-SPAK/OSR1 regulatory pathway may be targets for novel antihypertensive drugs. In this review, we outline the impact of these regulators on the activity of NCC and the consequent effect on BP.

In-silico identification and functional characterization of common genes associated with type 2 diabetes and hypertension

Type 2 diabetes (T2D) and hypertension are global public health concerns and major metabolic disorders in humans. Experimental evidence indicates considerable hereditary influences on the etiology of T2D and hypertension, but the molecular basis of these diseases is still limited. Thus, the current study analyzed 185 (132 T2D and 53 hypertension) GWAS catalog datasets and identified 83 common genes linked to T2D and hypertension pathogenesis. These genes were further examined using various bioinformatics approaches to elucidate their molecular mechanisms underlying the pathophysiology of T2D and hypertension. Gene ontology (GO) analysis revealed the biological, cellular, and molecular functions of these genes, which were also linked to different T2D and hypertension pathways. Specifically, seven genes were found to be crucial for T2D, and nine were directly associated with hypertension. Protein-protein interaction (PPI) analysis identified 28 candidate genes and seven hub genes through 11 topological methods. Among 231 miRNAs, seven were significant in interacting with the hub genes, and nine transcription factors (TFs) out of 36 were linked to these hub genes. Additionally, two of the seven hub genes were downregulated by 43 FDA-approved drugs. These findings elucidate the molecular processes underlying T2D and hypertension, suggesting that targeting these genes could lead to future drug development and therapeutic strategies to treat T2D and hypertension.

Advances in uromodulin biology and potential clinical applications

Uromodulin (also known as Tamm-Horsfall protein) is a kidney-specific glycoprotein secreted bidirectionally into urine and into the circulation, and it is the most abundant protein in normal urine. Although the discovery of uromodulin predates modern medicine, its significance in health and disease has been rather enigmatic. Research studies have gradually revealed that uromodulin exists in multiple forms and has important roles in urinary and systemic homeostasis. Most uromodulin in urine is polymerized into highly organized filaments, whereas non-polymeric uromodulin is detected both in urine and in the circulation, and can have distinct roles. The interactions of uromodulin with the immune system, which were initially reported to be a key role of this protein, are now better understood. Moreover, the discovery that uromodulin is associated with a spectrum of kidney diseases, including acute kidney injury, chronic kidney disease and autosomal-dominant tubulointerstitial kidney disease, has further accelerated investigations into the role of this protein. These discoveries have prompted new questions and ushered in a new era in uromodulin research. Here, we delineate the latest discoveries in uromodulin biology and its emerging roles in modulating kidney and systemic diseases, and consider future directions, including its potential clinical applications.

Multiple urinary peptides are associated with hypertension: a link to molecular pathophysiology

OBJECTIVES

Hypertension is a common condition worldwide; however, its underlying mechanisms remain largely unknown. This study aimed to identify urinary peptides associated with hypertension to further explore the relevant molecular pathophysiology.

METHODS

Peptidome data from 2876 individuals without end-organ damage were retrieved from the Human Urinary Proteome Database, belonging to general population (discovery) or type 2 diabetic (validation) cohorts. Participants were divided based on systolic blood pressure (SBP) and diastolic BP (DBP) into hypertensive (SBP ≥140 mmHg and/or DBP ≥90 mmHg) and normotensive (SBP <120 mmHg and DBP <80 mmHg, without antihypertensive treatment) groups. Differences in peptide abundance between the two groups were confirmed using an external cohort ( n  = 420) of participants without end-organ damage, matched for age, BMI, eGFR, sex, and the presence of diabetes. Furthermore, the association of the peptides with BP as a continuous variable was investigated. The findings were compared with peptide biomarkers of chronic diseases and bioinformatic analyses were conducted to highlight the underlying molecular mechanisms.

RESULTS

Between hypertensive and normotensive individuals, 96 (mostly COL1A1 and COL3A1) peptides were found to be significantly different in both the discovery (adjusted) and validation (nominal significance) cohorts, with consistent regulation. Of these, 83 were consistently regulated in the matched cohort. A weak, yet significant, association between their abundance and standardized BP was also observed.

CONCLUSION

Hypertension is associated with an altered urinary peptide profile with evident differential regulation of collagen-derived peptides. Peptides related to vascular calcification and sodium regulation were also affected. Whether these modifications reflect the pathophysiology of hypertension and/or early subclinical organ damage requires further investigation.

The role of uromodulin in cardiovascular disease: a review

Uromodulin, also referred to as Tamm Horsfall protein (THP), is a renal protein exclusively synthesized by the kidneys and represents the predominant urinary protein under normal physiological conditions. It assumes a pivotal role within the renal system, contributing not only to ion transport and immune modulation but also serving as a critical factor in the prevention of urinary tract infections and kidney stone formation. Emerging evidence indicates that uromodulin may serve as a potential biomarker extending beyond renal function. Recent clinical investigations and Mendelian randomization studies have unveiled a discernible association between urinary regulatory protein levels and cardiovascular events and mortality. This review primarily delineates the intricate relationship between uromodulin and cardiovascular disease, elucidates its predictive utility as a novel biomarker for cardiovascular events, and delves into its involvement in various physiological and pathophysiological facets of the cardiovascular system, incorporating recent advancements in corresponding genetics.

Uromodulin biology

Uromodulin is a kidney-specific glycoprotein which is exclusively produced by the epithelial cells lining the thick ascending limb and early distal convoluted tubule. It is currently recognized as a multifaceted player in kidney physiology and disease, with discrete roles for intracellular, urinary, interstitial and serum uromodulin. Among these, uromodulin modulates renal sodium handling through the regulation of tubular sodium transporters that reabsorb sodium and are targeted by diuretics, such as the loop diuretic-sensitive Na+-K+-2Cl- cotransporter type 2 (NKCC2) and the thiazide-sensitive Na+/Cl- cotransporter (NCC). Given these roles, the contribution of uromodulin to sodium-sensitive hypertension has been proposed. However, recent studies in humans suggest a more complex interaction between dietary sodium intake, uromodulin and blood pressure. This review presents an updated overview of the uromodulin's biology and its various roles, and focuses on the interaction between uromodulin and sodium-sensitive hypertension.

Uromodulin in sepsis and severe pneumonia: a two-sample Mendelian randomization study

The outcome for patients with sepsis-associated acute kidney injury in the intensive care unit (ICU) remains poor. Low serum uromodulin (sUMOD) protein levels have been proposed as a causal mediator of this effect. We investigated the effect of different levels of sUMOD on the risk of sepsis and severe pneumonia and outcomes in these conditions. A two-sample Mendelian randomization (MR) study was performed. Single-nucleotide polymorphisms (SNPs) associated with increased levels of sUMOD were identified and used as instrumental variables for association with outcomes. Data from different cohorts were combined based on disease severity and meta-analyzed. Five SNPs associated with increased sUMOD levels were identified and tested in six datasets from two biobanks. There was no protective effect of increased levels of sUMOD on the risk of sepsis [two cohorts, odds ratio (OR) 0.99 (95% confidence interval 0.95-1.03), P = 0.698, and OR 0.95 (0.91-1.00), P = 0.060, respectively], risk of sepsis requiring ICU admission [OR 1.04 (0.93-1.16), P = 0.467], ICU mortality in sepsis [OR 1.00 (0.74-1.37), P = 0.987], risk of pneumonia requiring ICU admission [OR 1.05 (0.98-1.14), P = 0.181], or ICU mortality in pneumonia [OR 1.17 (0.98-1.39), P = 0.079]. Meta-analysis of hospital-admitted and ICU-admitted patients separately yielded similar results [OR 0.98 (0.95-1.01), P = 0.23, and OR 1.05 (0.99-1.12), P = 0.86, respectively]. Among patients with sepsis and severe pneumonia, there was no protective effect of different levels of sUMOD. Results were consistent regardless of geographic origins and not modified by disease severity. NEW & NOTEWORTHY The presence of acute kidney injury in severe infections increases the likelihood of poor outcome severalfold. A decrease in serum uromodulin (sUMOD), synthetized in the kidney, has been proposed as a mediator of this effect. Using the Mendelian randomization technique, we tested the hypothesis that increased sUMOD is protective in severe infections. Analyses, however, showed no evidence of a protective effect of higher levels of sUMOD in sepsis or severe pneumonia.

siRNA as potential therapeutic strategy for hypertension

Hypertension, a well-known cardiovascular disorder noticed by rise in blood pressure, poses a significant global health challenge. The development RNA interfering (RNAi)-based therapies offers a ground-breaking molecular tool, holds promise for addressing hypertension's intricate molecular mechanisms. Harnessing the power of small interfering RNA (siRNA), researchers aim to selectively target and modulate genes associated with hypertension. Furthermore, they aim to downregulate the levels of mRNA by activating cellular nucleases in response to sequence homology between the siRNA and the corresponding mRNA molecule. As a result, genes involved in the cause of disorders linked to a known genetic background can be silenced using siRNA strategy. In the realm of hypertension, siRNA therapy emerges as a potential therapy for prognostics, diagnostics and treatments. It plays an important role in execution of targeting suppression of genes involved in vascular tone regulation, sodium handling, and pathways contributing to high blood pressure. A clinical trial involving intervention like angiotensinogen siRNA (AGT siRNA) is currently being carried out to treat hypertension. Genetic correlations between uromodulin (UMOD) and hypertension are investigated as emerging Non AGT siRNA target. Furthermore, expression of UMOD is responsible for regulation of sodium by modulating the tumor necrosis factor-α and regulating the Na + -K + -2Cl-cotransporter (NKCC2) in the thick ascending limb, which makes it an important target for blood pressure regulation.

From Rare Disorders of Kidney Tubules to Acute Renal Injury: Progress and Prospective

Background

Acute kidney injury (AKI) is a severe condition marked by rapid renal function deterioration and elevated mortality, with traditional biomarkers lacking sensitivity and specificity. Rare tubulointerstitial diseases encompass a spectrum of disorders, primarily including monogenic diseases, immune-related conditions, and drug-induced tubulointerstitial diseases. The clinical manifestations vary from electrolyte and acid-base imbalances to kidney function insufficiency, which is associated with AKI in up to 20% of cases. Evidence indicated that rare tubulointerstitial diseases might provide new conceptual insights and perspectives for novel biomarkers and potential therapeutic strategies for AKI.

Summary

Autosomal dominant tubulointerstitial kidney disease (ADTKD) and Fanconi syndrome (FS) are rare tubulointerstitial diseases. In ADTKD, UMOD and REN are closely related to AKI by affecting oxidative stress and tubuloglomerular feedback, which provide potential new biomarkers for AKI. Both rare tubulointerstitial diseases and AKI share etiologies and treatment responses. From the mechanism standpoint, rare tubulointerstitial diseases and AKI involve tubular transporter injury, initially manifesting as tubular dysfunction in tubulointerstitial disorder and progressing to AKI because of the programmed cell death with apoptosis, pyroptosis, or necroptosis of proximal tubule cells. Additionally, mitochondrial dysfunction has been identified as a common mechanism in both tubulointerstitial diseases and AKI induced by drugs, pSS, or monoclonal diseases. In the end, both AKI and FS patients and animal models responded well to the therapy of the primary diseases.

Key Messages

In this review, we describe an overview of ADTKD and FS to identify their associations with AKI. Mitochondrial dysfunction contributes to rare tubulointerstitial diseases and AKI, which might provide a potential therapeutic target.

Pregnancy-associated changes in urinary uromodulin excretion in chronic hypertension

BACKGROUND

Pregnancy involves major adaptations in renal haemodynamics, tubular, and endocrine functions. Hypertensive disorders of pregnancy are a leading cause of maternal mortality and morbidity. Uromodulin is a nephron-derived protein that is associated with hypertension and kidney diseases. Here we study the role of urinary uromodulin excretion in hypertensive pregnancy.

METHODS

Urinary uromodulin was measured by ELISA in 146 pregnant women with treated chronic hypertension (n = 118) and controls (n = 28). We studied non-pregnant and pregnant Wistar Kyoto and Stroke Prone Spontaneously Hypertensive rats (n = 8/strain), among which a group of pregnant Stroke-Prone Spontaneously Hypertensive rats was treated with either nifedipine (n = 7) or propranolol (n = 8).

RESULTS

In pregnant women, diagnosis of chronic hypertension, increased maternal body mass index, Black maternal ethnicity and elevated systolic blood pressure at the first antenatal visit were significantly associated with a lower urinary uromodulin-to-creatinine ratio. In rodents, pre-pregnancy urinary uromodulin excretion was twofold lower in Stroke-Prone Spontaneously Hypertensive rats than in Wistar Kyoto rats. During pregnancy, the urinary uromodulin excretion rate gradually decreased in Wistar Kyoto rats (a twofold decrease), whereas a 1.5-fold increase was observed in Stroke-Prone Spontaneously Hypertensive rats compared to pre-pregnancy levels. Changes in uromodulin were attributed by kidney injury in pregnant rats. Neither antihypertensive changed urinary uromodulin excretion rate in pregnant Stroke-Prone Spontaneously Hypertensive rats.

CONCLUSIONS

In summary, we demonstrate pregnancy-associated differences in urinary uromodulin: creatinine ratio and uromodulin excretion rate between chronic hypertensive and normotensive pregnancies. Further research is needed to fully understand uromodulin physiology in human pregnancy and establish uromodulin's potential as a biomarker for renal adaptation and renal function in pregnancy.

Susceptibility to hypertension based on MTHFR rs1801133 single nucleotide polymorphism and MTHFR promoter methylation

Background

The aetio-pathologenesis of hypertension is multifactorial, encompassing genetic, epigenetic, and environmental factors. The combined effect of genetic and epigenetic changes on hypertension is not known. We evaluated the independent and interactive association of MTHFR rs1801133 single nucleotide polymorphism (SNP) and MTHFR promoter methylation with hypertension among Taiwanese adults.

Methods

We retrieved data including, MTHFR promoter methylation, MTHFR rs1801133 genotypes (CC, CT, and TT), basic demography, personal lifestyle habits, and disease history of 1,238 individuals from the Taiwan Biobank (TWB).

Results

The distributions of hypertension and MTHFR promoter methylation quartiles (β < 0.1338, 0.1338 ≤ β < 0.1385, 0.1385 ≤ β < 0.1423, and β ≥ 0.1423 corresponding to

Conclusion

Independently, rs1801133 TT was associated with a higher risk of hypertension, but methylation was not. Based on genotypes, lower methylation was dose-dependently associated with a higher risk of hypertension in individuals with the CC genotype. Our findings suggest that MTHFR rs1801133 and MTHFR promoter methylation could jointly influence hypertension susceptibility.

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Key Words

• MTHFR
• hypertension
• interaction
• promoter methylation
• rs1801133
• susceptibility

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Affiliation(s)

Ming-Huang Chiu Department of Pulmonology and Respiratory Care, Cathay General Hospital, Taipei City, Taiwan
Chia-Hsiu Chang Cardiovascular Center, Cathay General Hospital, Taipei City, Taiwan
Disline Manli Tantoh Department of Medical Imaging, Chung Shan Medical University Hospital, Taichung City, Taiwan Department of Public Health and Institute of Public Health, Chung Shan Medical University, Taichung City, Taiwan
Tsui-Wen Hsu Superintendent Office, Institute of Medicine, Cathay General Hospital, Taipei City, Taiwan
Chih-Hsuan Hsiao Department of Public Health and Institute of Public Health, Chung Shan Medical University, Taichung City, Taiwan
Ji-Han Zhong Department of Public Health and Institute of Public Health, Chung Shan Medical University, Taichung City, Taiwan
Yung-Po Liaw Department of Medical Imaging, Chung Shan Medical University Hospital, Taichung City, Taiwan Department of Public Health and Institute of Public Health, Chung Shan Medical University, Taichung City, Taiwan Institute of Medicine, Chung Shan Medical University, Taichung City, Taiwan

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UROMODULIN - A LINK BETWEEN SODIUM EXCRETION AND ALTERATION IN CIRCADIAN BLOOD PRESSURE PATTERN IN PREHYPERTENSIVES

Although changes in dietary sodium intake alter blood pressure (BP) in salt-sensitive individuals, pathophysiological mechanisms are still unknown. It has been reported that uromodulin is involved in sodium tubular transport, and genome-wide association studies pointed to UMOD gene as one of the most important gene candidates for arterial hypertension. Our aim was to analyze urinary uromodulin, salt intake and BP in 326 young middle-aged subjects (mean age 36±8 years, 49.4% male). In a subgroup of 175 individuals, ambulatory blood pressure monitoring and echocardiogram were performed. Uromodulin was determined by ELISA. According to the JNC-7 criteria, subjects were classified as optimal BP (n=103, men 72%), prehypertension (PHT) (n=143, men 43%) and hypertension (HT) (n= 80, men 38%). There were no differences in age, salt intake, estimated glomerular filtration rate, sodium excretion and uromodulin among BP groups. However, in PHT subjects, uromodulin was positively associated with fractional sodium excretion and negatively with 24-h sodium excretion and diastolic BP dip. These findings point to the effect of uromodulin on sodium reabsorption along the nephron and consequently circadian BP alteration in prehypertensives.

Longitudinal effects of a common UMOD variant on kidney function, blood pressure, cognitive and physical function in older women and men

Genetic variants in UMOD associate with kidney function and hypertension. These phenotypes are also linked to sex-related differences and impairment in cognitive and physical function in older age. Here we evaluate longitudinal associations between a common UMOD rs4293393-A>G variant and changes in estimated glomerular filtration rate (eGFR), blood pressure (BP), cognitive and physical function parameters in older participants in the BASE-II after long-term follow-up as part of the GendAge study. Overall, 1010 older participants (mean age 75.7 ± 3.7 years, 51.6% women) were analyzed after follow-up (mean 7.4 years) both in cross-sectional analysis and in longitudinal analysis as compared to baseline. In cross-sectional analysis, heterozygous G-allele carriers exhibited significantly higher eGFR values (AA, 71.3 ml/min/1.73 m2, 95% CI, 70.3-72.3 vs. AG, 73.5 ml/min/1.73 m2, 95% CI, 72.1-74.9, P = 0.033). Male heterozygous G-allele carriers had lower odds of eGFR < 60 mL/min/1.73 m2 (OR 0.51, 95% CI, 0.28-0.95, P = 0.032) and in Timed Up and Go-Test ≥ 10 s (OR 0.50, 95% CI, 0.29-0.85, P = 0.011) whereas women were less likely to have hypertension (OR 0.58, CI, 0.37-0.91, P = 0.018). UMOD genotypes were not significantly associated with longitudinal changes in any investigated phenotype. Thus, while the impact of UMOD rs4293393 on kidney function is maintained in aging individuals, this variant has overall no impact on longitudinal changes in BP, kidney, cognitive or functional phenotypes. However, our results suggest a possible sex-specific modifying effect of UMOD on eGFR and physical function in men and hypertension prevalence in women.

Role of non-coding variants in cardiovascular disease

Cardiovascular diseases (CVDs) constitute one of the significant causes of death worldwide. Different pathological states are linked to CVDs, which despite interventions and treatments, still have poor prognoses. The genetic component, as a beneficial tool in the risk stratification of CVD development, plays a role in the pathogenesis of this group of diseases. The emergence of genome-wide association studies (GWAS) have led to the identification of non-coding parts associated with cardiovascular traits and disorders. Variants located in functional non-coding regions, including promoters/enhancers, introns, miRNAs and 5'/3' UTRs, account for 90% of all identified single-nucleotide polymorphisms associated with CVDs. Here, for the first time, we conducted a comprehensive review on the reported non-coding variants for different CVDs, including hypercholesterolemia, cardiomyopathies, congenital heart diseases, thoracic aortic aneurysms/dissections and coronary artery diseases. Additionally, we present the most commonly reported genes involved in each CVD. In total, 1469 non-coding variants constitute most reports on familial hypercholesterolemia, hypertrophic cardiomyopathy and dilated cardiomyopathy. The application and identification of non-coding variants are beneficial for the genetic diagnosis and better therapeutic management of CVDs.

Identifying a urinary peptidomics profile for hypertension in young adults: The African-PREDICT study: Urinary peptidomics and hypertension: Urinary peptidomics and hypertension

Hypertension is one of the most important and complex risk factors for cardiovascular diseases (CVDs). By using urinary peptidomics analyses, we aimed to identify peptides associated with hypertension, building a framework for future research towards improved prediction and prevention of premature development of CVD. We included 78 hypertensive and 79 normotensive participants from the African-PREDICT study (aged 20-30 years), matched for sex (51% male) and ethnicity (49% black and 51% white). Urinary peptidomics data were acquired using capillary-electrophoresis-time-of-flight-mass-spectrometry. Hypertension-associated peptides were identified and combined into a support vector machine-based multidimensional classifier. When comparing the peptide data between the normotensive and hypertensive groups, 129 peptides were nominally differentially abundant (Wilcoxon p < 0.05). Nonetheless, only three peptides, all derived from collagen alpha-1(III), remained significantly different after rigorous adjustments for multiple comparisons. The 37 most significant peptides (all p ≤ 0.001) served as basis for the development of a classifier, with 20 peptides being combined into a unifying score, resulting in an AUC of 0.85 in the ROC analysis (p < 0.001), with 83% sensitivity at 80% specificity. Our study suggests potential value of urinary peptides in the classification of hypertension, which could enable earlier diagnosis and better understanding of the pathophysiology of hypertension and premature cardiovascular disease development.

Uromodulin: more than a marker for chronic kidney disease progression

PURPOSE OF REVIEW

Uromodulin, a protein that is highly conserved across several species through evolution, functions to maintain homeostasis and prevent disease development and progression. Historically, the role of uromodulin has been thought to be limited to the kidney and genitourinary tract. This review highlights developments indicating a broader role of uromodulin in human health.

RECENT FINDINGS

Although initially discovered in the urine and found to have immunomodulatory properties, recent findings indicate that serum uromodulin (sUMOD) is distinct from urine uromodulin (uUMOD) in its structure, function, and regulation. uUMOD binds pathogenic bacteria in the urine preventing infection and is also upregulated in kidneys undergoing repair after injury. Uromodulin knockout mice exhibit higher mortality in the setting of sepsis which is also associated with upregulation of sUMOD. sUMOD lowers calcification risk but this may be influenced by presence of kidney disease.

SUMMARY

Uromodulin is an evolutionarily conserved protein produced exclusively in the kidney tubule cells with evolving roles being reported both in the kidney and systemically. Further research should be focused at harnessing its use as a potential therapeutic.

Genomic Disorders in CKD across the Lifespan

SIGNIFICANCE STATEMENT

Pathogenic structural genetic variants, also known as genomic disorders, have been associated with pediatric CKD. This study extends those results across the lifespan, with genomic disorders enriched in both pediatric and adult patients compared with controls. In the Chronic Renal Insufficiency Cohort study, genomic disorders were also associated with lower serum Mg, lower educational performance, and a higher risk of death. A phenome-wide association study confirmed the link between kidney disease and genomic disorders in an unbiased way. Systematic detection of genomic disorders can provide a molecular diagnosis and refine prediction of risk and prognosis.

BACKGROUND

Genomic disorders (GDs) are associated with many comorbid outcomes, including CKD. Identification of GDs has diagnostic utility.

METHODS

We examined the prevalence of GDs among participants in the Chronic Kidney Disease in Children (CKiD) cohort II ( n =248), Chronic Renal Insufficiency Cohort (CRIC) study ( n =3375), Columbia University CKD Biobank (CU-CKD; n =1986), and the Family Investigation of Nephropathy and Diabetes (FIND; n =1318) compared with 30,746 controls. We also performed a phenome-wide association analysis (PheWAS) of GDs in the electronic MEdical Records and GEnomics (eMERGE; n =11,146) cohort.

RESULTS

We found nine out of 248 (3.6%) CKiD II participants carried a GD, replicating prior findings in pediatric CKD. We also identified GDs in 72 out of 6679 (1.1%) adult patients with CKD in the CRIC, CU-CKD, and FIND cohorts, compared with 199 out of 30,746 (0.65%) GDs in controls (OR, 1.7; 95% CI, 1.3 to 2.2). Among adults with CKD, we found recurrent GDs at the 1q21.1, 16p11.2, 17q12, and 22q11.2 loci. The 17q12 GD (diagnostic of renal cyst and diabetes syndrome) was most frequent, present in 1:252 patients with CKD and diabetes. In the PheWAS, dialysis and neuropsychiatric phenotypes were the top associations with GDs. In CRIC participants, GDs were associated with lower serum magnesium, lower educational achievement, and higher mortality risk.

CONCLUSION

Undiagnosed GDs are detected both in children and adults with CKD. Identification of GDs in these patients can enable a precise genetic diagnosis, inform prognosis, and help stratify risk in clinical studies. GDs could also provide a molecular explanation for nephropathy and comorbidities, such as poorer neurocognition for a subset of patients.

Renal Assessment in Acute Cardiorenal Syndrome

Cardiorenal syndrome (CRS) is a complex, heterogeneous spectrum of symptoms that has kept cardiologists awake for decades. The heart failure (HF) population being burdened with multimorbidity poses diagnostic and therapeutic challenges even for experienced clinicians. Adding deteriorated renal function to the equation, which is one of the strongest predictors of adverse outcome, we measure ourselves against possibly the biggest problem in modern cardiology. With the rapid development of new renal assessment methods, we can treat CRS more effectively than ever. The presented review focuses on explaining the pathophysiology, recent advances and current practices of monitoring renal function in patients with acute CRS. Understanding the dynamic interaction between the heart and the kidney may improve patient care and support the selection of an effective and nephroprotective treatment strategy.

A genomic deep field view of hypertension

Blood pressure is regulated by a complex neurohumoral system including the renin-angiotensin-aldosterone system, natriuretic peptides, endothelial pathways, the sympathetic nervous system, and the immune system. This review charts the evolution of our understanding of the genomic basis of hypertension at increasing resolution over the last 5 decades from monogenic causes to polygenic associations, spanning ∼30 monogenic rare variants and >1500 single nucleotide variants. Unexpected early wins from blood pressure genomics include deepening of our understanding of the complex causation of hypertension; refinement of causal estimates bidirectionally between blood pressure, risk factors, and outcomes through Mendelian randomization; risk stratification using polygenic risk scores; and opportunities for precision medicine and drug repurposing.

Responses to Ang II (Angiotensin II), Salt Intake, and Lipopolysaccharide Reveal the Diverse Actions of TNF-α (Tumor Necrosis Factor-α) on Blood Pressure and Renal Function

TNF-α (tumor necrosis factor-alpha) is the best known as a proinflammatory cytokine; yet, this cytokine also has important immunomodulatory and regulatory functions. As the effects of TNF-α on immune system function were being revealed, the spectrum of its activities appeared in conflict with each other before investigators defined the settings and mechanisms by which TNF-α contributed to both host defense and chronic inflammation. These effects reflect self-protective mechanisms that may become harmful when dysregulated. The paradigm of physiological and pathophysiological effects of TNF-α has since been uncovered in the lung, colon, and kidney where its role has been identified in pulmonary edema, electrolyte reabsorption, and blood pressure regulation, respectively. Recent studies on the prohypertensive and inflammatory effects of TNF-α in the cardiovascular system juxtaposed to those related to NaCl and blood pressure homeostasis, the response of the kidney to lipopolysaccharide, and protection against bacterial infections are helping define the mechanisms by which TNF-α modulates distinct functions within the kidney. This review discusses how production of TNF-α by renal epithelial cells may contribute to regulatory mechanisms that not only govern electrolyte excretion and blood pressure homeostasis but also maintain the appropriate local hypersalinity environment needed for optimizing the innate immune response to bacterial infections in the kidney. It is possible that the wide range of effects mediated by TNF-α may be related to severity of disease, amount of inflammation and TNF-α levels, and the specific cell types that produce this cytokine, areas that remain to be investigated further.

Blood Pressure Mediated the Effects of Urinary Uromodulin Levels on Myocardial Infarction: a Mendelian Randomization Study

Background:

The causal links between urinary uromodulin (uUMOD) and cardiovascular disease (CVD) are still not clarified.

Methods:

We first assessed the relationship between uUMOD and CVD using bidirectional 2-sample Mendelian randomization. Then, multivariable Mendelian randomization and product of the coefficients methods were used to investigate the role of blood pressure in mediating the effect of uUMOD on CVD.

Results:

1-unit higher uUMOD level was associated with a higher risk of myocardial infarction (MI), with an odds ratio of 1.08 ([95% CI, 1.02–1.14]; P =0.009), while MI was not associated with uUMOD levels in reverse. Our study did not support the causal effects of uUMOD on other CVD outcomes, including coronary artery disease, atrial fibrillation, heart failure, and ischemic stroke. In multivariable Mendelian Randomization, the direct effects of uUMOD on MI were attenuated to null after introducing systolic blood pressure or diastolic blood pressure. Mediation analysis showed that the indirect effect of uUMOD on MI mediated by systolic blood pressure or diastolic blood pressure was 1.05 ([95% CI, 1.04–1.06]; mediation proportion=69%) and 1.07 ([95% CI, 1.05–1.08]; mediation proportion=87%), respectively. Similar results were found in sensitivity analysis based on different sets of genetic instruments.

Conclusions:

Our findings provide evidence for the effect of higher uUMOD on increasing blood pressure, which mediates a consequent effect on MI risk in the general population. Further studies are necessary to verify the associations between uUMOD and other CVD outcomes.

Effect of a common UMOD variant on kidney function, blood pressure, cognitive and physical function in a community-based cohort of older adults

In genome-wide association studies, genetic variants in the UMOD gene associate with kidney function, blood pressure (BP), and hypertension. Elevated BP is linked to kidney function and impaired cognitive as well as physical performance in later life. We investigated the association between UMOD rs4293393-A > G and kidney function, BP, cognitive and physical function in the Berlin Aging Study II (BASE-II). Data of 1556 older BASE-II participants (mean age 68.2 ± 3.7 years) were analyzed. BP was determined by standardized automated measurements, estimated glomerular filtration rate (eGFR) by CKD Epidemiology Collaboration creatinine equation. Cognitive function was assessed by Mini-Mental State Examination and Digit Symbol Substitution Test, while physical function by Handgrip Strength and Timed Up and Go-Test. Association analyses were performed by covariance and logistic regression models adjusting for sex. G-allele carriers at UMOD rs4293393 exhibited significantly higher eGFR values compared to non-carriers (AA, 76.4 ml/min/1.73 m², CI: 75.7-77.2 vs. AG, 78.4 ml/min/1.73 m², CI: 77.3-79.5 vs. GG, 78.5 ml/min/1.73 m², CI: 75.4-81.7; P = 0.010), and a lower risk of eGFR < 60 mL/min/1.73 m² (AG, OR: 0.63, CI: 0.41-0.97, P = 0.033). However, UMOD rs4293393 genotypes were not associated with BP, diagnosis of hypertension or cognitive and physical function parameters. Our data corroborate previous findings on the association of UMOD rs4293393-G with better kidney function in older adults. However, no association between UMOD and BP or physical and cognitive parameters in these community-dwelling older adults was detected.

Evolving Concepts in Uromodulin Biology, Physiology, and Its Role in Disease: a Tale of Two Forms

Uromodulin (or Tamm-Horsfall protein) is a glycoprotein uniquely produced in the kidney by tubular cells of the thick ascending limb of the loop of Henle and early distal tubules. This protein exhibits bidirectional secretion in the urine and in the renal interstitium and circulation. The role of this protein in maintaining renal and systemic homeostasis is becoming increasingly appreciated. Furthermore, perturbations of its functions may play a role in various diseases affecting the kidney and distant organs. In this review, we will discuss important advances in understanding its biology, highlighting the recent discoveries of its secretion and differential precursor processing that generates 2 forms: (1) a highly polymerizing form that is apically excreted in the urine and generates filaments and (2) a nonpolymerizing form that retains a polymerization inhibitory pro-peptide and is released basolaterally in the kidney interstitium and circulation, but can also be found in the urine. We will also discuss factors regulating its production and release, taking into account its intricate physiology, and propose best practices to report its levels. We also discuss breaking advances in its role in hypertension, acute kidney injury and progression to chronic disease, immunomodulation and regulating renal and systemic oxidative stress. We anticipate that this work will be a great resource for researchers and clinicians. This review will highlight the importance of defining what regulates the 2 forms of uromodulin, so that modulation of uromodulin levels and function could become a novel tool in our therapeutic armamentarium against kidney disease.

Role of Uromodulin in Salt-Sensitive Hypertension

The exclusive expression of uromodulin in the kidneys has made it an intriguing protein in kidney and cardiovascular research. Genome-wide association studies discovered variants of uromodulin that are associated with chronic kidney diseases and hypertension. Urinary and circulating uromodulin levels reflect kidney and cardiovascular health as well as overall mortality. More recently, Mendelian randomization studies have shown that genetically driven levels of uromodulin have a causal and adverse effect on kidney function. On a mechanistic level, salt sensitivity is an important factor in the pathophysiology of hypertension, and uromodulin is involved in salt reabsorption via the NKCC2 (Na+-K+-2Cl- cotransporter) on epithelial cells of the ascending limb of loop of Henle. In this review, we provide an overview of the multifaceted physiology and pathophysiology of uromodulin including recent advances in its genetics; cellular trafficking; and mechanistic and clinical studies undertaken to understand the complex relationship between uromodulin, blood pressure, and kidney function. We focus on tubular sodium reabsorption as one of the best understood and pathophysiologically and clinically most important roles of uromodulin, which can lead to therapeutic interventions.

Towards a global view of multiple sclerosis genetics

Multiple sclerosis (MS) is a neuroimmunological disorder of the CNS with a strong heritable component. The genetic architecture of MS susceptibility is well understood in populations of European ancestry. However, the extent to which this architecture explains MS susceptibility in populations of non-European ancestry remains unclear. In this Perspective article, we outline the scientific arguments for studying MS genetics in ancestrally diverse populations. We argue that this approach is likely to yield insights that could benefit individuals with MS from all ancestral groups. We explore the logistical and theoretical challenges that have held back this field to date and conclude that, despite these challenges, inclusion of participants of non-European ancestry in MS genetics studies will ultimately be of value to all patients with MS worldwide.

Insights From a Large-Scale Whole-Genome Sequencing Study of Systolic Blood Pressure, Diastolic Blood Pressure, and Hypertension

BACKGROUND

The availability of whole-genome sequencing data in large studies has enabled the assessment of coding and noncoding variants across the allele frequency spectrum for their associations with blood pressure.

METHODS

We conducted a multiancestry whole-genome sequencing analysis of blood pressure among 51 456 Trans-Omics for Precision Medicine and Centers for Common Disease Genomics program participants (stage-1). Stage-2 analyses leveraged array data from UK Biobank (N=383 145), Million Veteran Program (N=318 891), and Reasons for Geographic and Racial Differences in Stroke (N=10 643) participants, along with whole-exome sequencing data from UK Biobank (N=199 631) participants.

RESULTS

Two blood pressure signals achieved genome-wide significance in meta-analyses of stage-1 and stage-2 single variant findings (P<5×10-8). Among them, a rare intergenic variant at novel locus, LOC100506274, was associated with lower systolic blood pressure in stage-1 (beta [SE]=-32.6 [6.0]; P=4.99×10-8) but not stage-2 analysis (P=0.11). Furthermore, a novel common variant at the known INSR locus was suggestively associated with diastolic blood pressure in stage-1 (beta [SE]=-0.36 [0.07]; P=4.18×10-7) and attained genome-wide significance in stage-2 (beta [SE]=-0.29 [0.03]; P=7.28×10-23). Nineteen additional signals suggestively associated with blood pressure in meta-analysis of single and aggregate rare variant findings (P<1×10-6 and P<1×10-4, respectively).

DISCUSSION

We report one promising but unconfirmed rare variant for blood pressure and, more importantly, contribute insights for future blood pressure sequencing studies. Our findings suggest promise of aggregate analyses to complement single variant analysis strategies and the need for larger, diverse samples, and family studies to enable robust rare variant identification.

UMOD and the architecture of kidney disease

The identification of genetic factors associated with the risk, onset, and progression of kidney disease has the potential to provide mechanistic insights and therapeutic perspectives. In less than two decades, technological advances yielded a trove of information on the genetic architecture of chronic kidney disease. The spectrum of genetic influence ranges from (ultra)rare variants with large effect size, involved in Mendelian diseases, to common variants, often non-coding and with small effect size, which contribute to polygenic diseases. Here, we review the paradigm of UMOD, the gene coding for uromodulin, to illustrate how a kidney-specific protein of major physiological importance is involved in a spectrum of kidney disorders. This new field of investigation illustrates the importance of genetic variation in the pathogenesis and prognosis of disease, with therapeutic implications.

Phenome-Wide Association Study of UMOD Gene Variants and Differential Associations With Clinical Outcomes Across Populations in the Million Veteran Program a Multiethnic Biobank

Introduction

Common variants in the UMOD gene are considered an evolutionary adaptation against urinary tract infections (UTIs) and have been implicated in kidney stone formation, chronic kidney disease (CKD), and hypertension. However, differences in UMOD variant-phenotype associations across population groups are unclear.

Methods

We tested associations between UMOD/PDILT variants and up to 1528 clinical diagnosis codes mapped to phenotype groups in the Million Veteran Program (MVP), using published phenome-wide association study (PheWAS) methodology. Associations were tested using logistic regression adjusted for age, sex, and 10 principal components of ancestry. Bonferroni correction for multiple comparisons was applied.

Results

Among 648,593 veterans, mean (SD) age was 62 (14) years; 9% were female, 19% Black, and 8% Hispanic. In White patients, the rs4293393 UMOD risk variant associated with increased uromodulin was associated with increased odds of CKD (odds ratio [OR]: 1.22, 95% CI: 1.20-1.24, P = 5.90 × 10-111), end-stage kidney disease (OR: 1.17, 95% CI: 1.11-1.24, P = 2.40 × 10-09), and hypertension (OR: 1.03, 95% CI: 1.05-1.05, P = 2.11 × 10-06) and significantly lower odds of UTIs (OR: 0.94, 95% CI: 0.92-0.96, P = 1.21 × 10-10) and kidney calculus (OR: 0.85, 95% CI: 0.83-0.86, P = 4.27 × 10-69). Similar findings were observed across UMOD/PDILT variants. The rs77924615 PDILT variant had stronger associations with acute cystitis in White female (OR: 0.73, 95% CI: 0.59-0.91, P = 4.98 × 10-03) versus male (OR: 0.99, 95% CI: 0.89-1.11, P = 8.80 × 10-01) (P interaction = 0.01) patients. In Black patients, the rs77924615 PDILT variant was significantly associated with pyelonephritis (OR: 0.65, 95% CI: 0.54-0.79, P = 1.05 × 10-05), whereas associations with UMOD promoter variants were attenuated.

Conclusion

Robust associations were observed between UMOD/PDILT variants linked with increased uromodulin expression and lower odds of UTIs and calculus and increased odds of CKD and hypertension. However, these associations varied significantly across ancestry groups and sex.

Corin Missense Variants, Blood Pressure, and Hypertension in 11 322 Black Individuals: Insights From REGARDS and the Jackson Heart Study

Background Corin enzyme contributes to the processing of inactive natriuretic peptides to bioactive hormones. In Black individuals, Corin gene variants (rs111253292 [Q568P] and rs75770792 [T555I]) have been previously reported to have a modest association with blood pressure (BP) and hypertension. Methods and Results We evaluated the association of Corin genotype with BP traits, prevalent hypertension, and incident hypertension among self-identified 11 322 Black Americans in the REGARDS (Reasons for Geographic and Racial Differences in Stroke) study and the JHS (Jackson Heart Study) using multivariable-adjusted regression modeling. Multivariable-adjusted genotype-stratified differences in NT-proBNP (N-terminal pro-B-type natriuretic peptide) and BNP (B-type natriuretic peptide) levels were assessed. Genotype-stratified NPPA and NPPB expression differences in healthy organ donor left atrial and left ventricular heart tissue (N=15) were also examined. The rs111253292 genotype was not associated with systolic BP (β±SE, 0.42±0.58; -1.24±0.82), diastolic BP (0.51±0.33; -0.41±0.46), mean arterial pressure (0.48±0.38; -0.68±0.51), and prevalent hypertension (odds ratio [OR], 0.93 [95% CI, 0.80-1.09]; OR, 0.79 [95% CI, 0.61-1.01]) in both REGARDS and JHS, respectively. The rs75770792 genotype was not associated with systolic BP (0.48±0.58; -1.26±0.81), diastolic BP (0.52±0.33; -0.33±0.45), mean arterial pressure (0.50±0.38; -0.63±0.50), and prevalent hypertension (OR, 1.02 [95% CI, 0.84-1.23]; OR, 0.87 [95% CI, 0.67-1.13]) in both cohorts, respectively. The Corin genotype was also not associated with incident hypertension (OR, 1.35 [95% CI, 0.94-1.93]; OR, 0.95 [95% CI, 0.64-1.39]) in the study cohorts. The NT-proBNP levels in REGARDS and BNP levels in JHS were similar between the Corin genotype groups. In heart tissue, the NPPA and NPPB expression was similar between the genotype groups. Conclusions Corin gene variants observed more commonly in Black individuals are not associated with differences in NP expression, circulating NP levels, and BP or hypertension as previously reported in candidate gene studies. Understanding the genetic determinants of complex cardiovascular traits in underrepresented populations requires further evaluation.

Genome-wide studies reveal factors associated with circulating uromodulin and its relationships to complex diseases

Uromodulin (UMOD) is a major risk gene for monogenic and complex forms of kidney disease. The encoded kidney-specific protein uromodulin is highly abundant in urine and related to chronic kidney disease, hypertension, and pathogen defense. To gain insights into potential systemic roles, we performed genome-wide screens of circulating uromodulin using complementary antibody-based and aptamer-based assays. We detected 3 and 10 distinct significant loci, respectively. Integration of antibody-based results at the UMOD locus with functional genomics data (RNA-Seq, ATAC-Seq, Hi-C) of primary human kidney tissue highlighted an upstream variant with differential accessibility and transcription in uromodulin-synthesizing kidney cells as underlying the observed cis effect. Shared association patterns with complex traits, including chronic kidney disease and blood pressure, placed the PRKAG2 locus in the same pathway as UMOD. Experimental validation of the third antibody-based locus, B4GALNT2, showed that the p.Cys466Arg variant of the encoded N-acetylgalactosaminyltransferase had a loss-of-function effect leading to higher serum uromodulin levels. Aptamer-based results pointed to enzymes writing glycan marks present on uromodulin and to their receptors in the circulation, suggesting that this assay permits investigating uromodulin's complex glycosylation rather than its quantitative levels. Overall, our study provides insights into circulating uromodulin and its emerging functions.

Application of omics in hypertension and resistant hypertension

Hypertension is a major modifiable risk factor that affects the global health burden. Despite the availability of multiple antihypertensive drugs, blood pressure is often not optimally controlled. The prevalence of true resistant hypertension in treated hypertensive patients is ~2-20%, and these patients are at higher risk for adverse events and poor clinical outcomes. Therefore, an in-depth dissection of the pathophysiological mechanisms of hypertension and resistant hypertension is needed to identify more effective targets for regulating blood pressure. Omics technologies, such as genomics, transcriptomics, proteomics, metabolomics, and microbiomics, can accurately present the characteristics of organisms at varying molecular levels. Integrative omics can further reveal the network of interactions between molecular levels and provide a complete dynamic view of the organism. In this review, we describe the applications, progress, and challenges of omics technologies in hypertension. Specifically, we discuss the application of omics in resistant hypertension. We believe that omics approaches will produce a better understanding of the pathogenesis of hypertension and resistant hypertension and improve diagnostic and therapeutic strategies, thus increasing rates of blood pressure control and reducing the public health burden of hypertension.

Cataloging the potential SNPs (single nucleotide polymorphisms) associated with quantitative traits, viz. BMI (body mass index), IQ (intelligence quotient) and BP (blood pressure): an updated review

Background

Single nucleotide polymorphism (SNP) variants are abundant, persistent and widely distributed across the genome and are frequently linked to the development of genetic diseases. Identifying SNPs that underpin complex diseases can aid scientists in the discovery of disease-related genes by allowing for early detection, effective medication and eventually disease prevention.

Main body

Various SNP or polymorphism-based studies were used to categorize different SNPs potentially related to three quantitative traits: body mass index (BMI), intelligence quotient (IQ) and blood pressure, and then uncovered common SNPs for these three traits. We employed SNPedia, RefSNP Report, GWAS Catalog, Gene Cards (Data Bases), PubMed and Google Scholar search engines to find relevant material on SNPs associated with three quantitative traits. As a result, we detected three common SNPs for all three quantitative traits in global populations: SNP rs6265 of the BDNF gene on chromosome 11p14.1, SNP rs131070325 of the SL39A8 gene on chromosome 4p24 and SNP rs4680 of the COMT gene on chromosome 22q11.21.

Conclusion

In our review, we focused on the prevalent SNPs and gene expression activities that influence these three quantitative traits. These SNPs have been used to detect and map complex, common illnesses in communities for homogeneity testing and pharmacogenetic studies. High blood pressure, diabetes and heart disease, as well as BMI, schizophrenia and IQ, can all be predicted using common SNPs. Finally, the results of our work can be used to find common SNPs and genes that regulate these three quantitative features across the genome.

First genome-wide association study investigating blood pressure and renal traits in domestic cats

Hypertension (HTN) and chronic kidney disease (CKD) are common in ageing cats. In humans, blood pressure (BP) and renal function are complex heritable traits. We performed the first feline genome-wide association study (GWAS) of quantitative traits systolic BP and creatinine and binary outcomes HTN and CKD, testing 1022 domestic cats with a discovery, replication and meta-analysis design. No variants reached experimental significance level in the discovery stage for any phenotype. Follow up of the top 9 variants for creatinine and 5 for systolic BP, one SNP reached experimental-wide significance for association with creatinine in the combined meta-analysis (chrD1.10258177; P = 1.34 × 10^–6). Exploratory genetic risk score (GRS) analyses were performed. Within the discovery sample, GRS of top SNPs from the BP and creatinine GWAS show strong association with HTN and CKD but did not validate in independent replication samples. A GRS including SNPs corresponding to human CKD genes was not significant in an independent subset of cats. Gene-set enrichment and pathway-based analysis (GSEA) was performed for both quantitative phenotypes, with 30 enriched pathways with creatinine. Our results support the utility of GWASs and GSEA for genetic discovery of complex traits in cats, with the caveat of our findings requiring validation.

Salt loading decreases urinary excretion and increases intracellular accumulation of uromodulin in stroke-prone spontaneously hypertensive rats

Uromodulin (UMOD) is the most abundant renal protein secreted into urine by the thick ascending limb (TAL) epithelial cells of the loop of Henle. Genetic studies have demonstrated an association between UMOD risk variants and hypertension. We aimed to dissect the role of dietary salt in renal UMOD excretion in normotension and chronic hypertension. Normotensive Wistar-Kyoto rats (WKY) and stroke-prone spontaneously hypertensive rats (SHRSP) (n=8/sex/strain) were maintained on 1% NaCl for 3 weeks. A subset of salt-loaded SHRSP was treated with nifedipine. Salt-loading in SHRSP increased blood pressure (ΔSBP 35 ± 5 mmHg, P<0.0001) and kidney injury markers such as kidney injury marker-1 (KIM-1; fold change, FC 3.4; P=0.003), neutrophil gelatinase-associated lipocalin (NGAL; FC, 2.0; P=0.012) and proteinuria. After salt-loading there was a reduction in urinary UMOD excretion in WKY and SHRSP by 26 and 55% respectively, compared with baseline. Nifedipine treatment reduced blood pressure (BP) in SHRSP, however, did not prevent salt-induced reduction in urinary UMOD excretion. In all experiments, changes in urinary UMOD excretion were dissociated from kidney UMOD protein and mRNA levels. Colocalization and ex-vivo studies showed that salt-loading increased intracellular UMOD retention in both WKY and SHRSP. Our study provides novel insights into the interplay among salt, UMOD, and BP. The role of UMOD as a cardiovascular risk marker deserves mechanistic reappraisal and further investigations based on our findings.

Associations of Serum Uromodulin and Its Genetic Variants With Blood Pressure and Hypertension in Chinese Adults

Background: Uromodulin, also named Tamm Horsfall protein, has been associated with renal function and regulation of sodium homeostasis. We aimed to examine the associations of serum uromodulin levels and its genetic variants with longitudinal blood pressure (BP) changes and hypertension incidence/risk. Methods: A total of 514 participants from the original Baoji Salt-Sensitive Study cohort were genotyped to examine the associations of genetic variations in uromodulin gene with the longitudinal BP changes and the incidence of hypertension over 8 years of follow-up. In addition, 2,210 subjects from the cohort of Hanzhong Adolescent Hypertension Study were used to investigate the relationships between serum uromodulin levels and the risk of hypertension. Results: SNPs rs12917707 and rs12708631 in the uromodulin gene were significantly associated with the longitudinal BP changes over 8 years of follow-up. SNP rs12708631 was significantly associated with the incidence of hypertension over 8 years. In addition, gene-based analyses supported the associations of uromodulin gene with the longitudinal BP changes and hypertension incidence in Baoji Salt-Sensitive Study cohort. Furthermore, serum uromodulin levels in the hypertensive subjects were lower than in the normotensive subjects (25.5 ± 1.1 vs. 34.7 ± 0.7 ng/mL). Serum uromodulin levels decreased gradually as BP levels increased (34.6, 33.2, 27.8, and 25.0 ng/mL for subjects with normotension, high-normal, grade 1 hypertension, and grade 2 hypertension, respectively). Serum uromodulin was significantly associated with the lower risk of hypertension [0.978 (0.972-0.984)] in Hanzhong Adolescent Hypertension Study cohort. Conclusion: This study shows that uromodulin is associated with blood pressure progression and development of hypertension.

Mendelian randomization to assess causality between uromodulin, blood pressure and chronic kidney disease

UMOD variants associated with higher levels of urinary uromodulin (uUMOD) increase the risk of chronic kidney disease (CKD) and hypertension. However, uUMOD levels also reflect functional kidney tubular mass in observational studies, questioning the causal link between uromodulin production and kidney damage. We used Mendelian randomization to clarify causality between uUMOD levels, kidney function and blood pressure in individuals of European descent. The link between uUMOD and estimated glomerular filtration rate (eGFR) was first investigated in a population-based cohort of 3851 individuals. In observational data, higher uUMOD associated with higher eGFR. Conversely, when using rs12917707 (an UMOD polymorphism) as an instrumental variable in one-sample Mendelian randomization, higher uUMOD strongly associated with eGFR decline. We next applied two-sample Mendelian randomization on four genome wide association study consortia to explore causal links between uUMOD and eGFR, CKD risk (567,460 individuals) and blood pressure (757,461 individuals). Higher uUMOD levels significantly associated with lower eGFR, higher odds for eGFR decline or CKD, and higher systolic or diastolic blood pressure. Each one standard deviation (SD) increase of uUMOD decreased log-transformed eGFR by -0.15 SD (95% confidence interval -0.17 to -0.13) and increased log-odds CKD by 0.13 SD (0.12 to 0.15). One SD increase of uUMOD increased systolic blood pressure by 0.06 SD (0.03 to 0.09) and diastolic blood pressure by 0.08 SD (0.05 to 0.12). The effect of uUMOD on blood pressure was mediated by eGFR, whereas the effect on eGFR was not mediated by blood pressure. Thus, our data support that genetically driven levels of uromodulin have a direct, causal and adverse effect on kidney function outcome in the general population, not mediated by blood pressure.

UMOD Polymorphisms Associated with Kidney Function, Serum Uromodulin and Risk of Mortality among Patients with Chronic Kidney Disease, Results from the C-STRIDE Study

We aimed to explore associations of several single nucleotide polymorphisms (SNPs) detected by genome-wide association studies in uromodulin (UMOD) gene with phenotypes and prognosis of chronic kidney disease (CKD) among 2731 Chinese patients with CKD stage 1–4. Polymorphisms of rs11864909, rs4293393, rs6497476, and rs13333226 were genotyped using the Sequenom MassARRAY iPLEX platform. The SNPs of rs13333226 and rs4293393 were in complete linkage disequilibrium. Based on the T dominant model, T allele of rs11864909 was associated with levels of estimated glomerular filtration rate (eGFR) and serum uromodulin with linear regression coefficients of 2.68 (95% confidence interval (CI): 0.61, 4.96) and −12.95 (95% CI: −17.59, −7.98), respectively, after adjustment for cardiovascular and kidney-specific risk factors. After a median follow-up of 4.94 years, both G allele of rs4293393/rs13333226 and C allele of rs6497476 were associated with reduced risk of all-cause mortality with multivariable-adjusted hazard ratios of 0.341 (95% CI: 0.105, 0.679) and 0.344 (95% CI: 0.104, 0.671), respectively. However, no associations were found between the variants and slope of eGFR in the linear mix effect model. In summary, the variant of rs11864909 in the UMOD gene was associated with levels of eGFR and serum uromodulin, while those of rs4293393 and rs6497476 were associated with all-cause mortality among patients with CKD.

Combined Use of Serum Uromodulin and eGFR to Estimate Mortality Risk

Serum uromodulin (sUmod) shows a strong direct correlation with eGFR in patients with impaired kidney function and an inverse association with mortality. However, there are patients in whom only one of both markers is decreased. Therefore, we aimed to investigate the effect of marker discordance on mortality risk. sUmod and eGFR were available in 3,057 participants of the Ludwigshafen Risk and Cardiovascular Health study and 529 participants of the VIVIT study. Both studies are monocentric prospective studies of patients that had been referred for coronary angiography. Participants were categorized into four groups according to the median values of sUmod (LURIC: 146 ng/ml, VIVIT: 156) and eGFR (LURIC: 84 ml/min/1.73 m², VIVIT: 87). In 945 LURIC participants both markers were high (UHGH), in 935 both were low (ULGL), in 589 only eGFR (UHGL), and in 582 only sUmod (ULGH) was low. After balancing the groups for cardiovascular risk factors, hazard ratios (95%CI) for all-cause mortality as compared to UHGH were 2.03 (1.63-2.52), 1.43 (1.13-1.81), and 1.32 (1.03-1.69) for ULGL, UHGL, and ULGH, respectively. In VIVIT, HRs were 3.12 (1.38-7.08), 2.38 (1.01-5.61), and 2.06 (0.81-5.22). Adding uromodulin to risk prediction models that already included eGFR as a covariate slightly increased the Harrell's C and significantly improved the AUC in LURIC. In UHGL patients, hypertension, heart failure and upregulation of the renin-angiotensin-aldosterone-system seem to be the driving forces of disease development, whereas in ULGH patients metabolic disturbances might be key drivers of increased mortality. In conclusion, SUmod/eGFR subgroups mirror distinct metabolic and clinical patterns. Assessing sUmod additionally to creatinine or cystatin C has the potential to allow a more precise risk modeling and might improve risk stratification.

Associations of plasma uromodulin and genetic variants with blood pressure responses to dietary salt interventions

Uromodulin, also named Tamm Horsfall protein, have been associated with renal function and sodium homeostasis regulation. The authors sought to examine the effects of salt intake on plasma and urinary uromodulin levels and the association of its genetic variants with salt sensitivity in Chinese adults. Eighty patients from our natural population cohort were maintained sequentially either on a usual diet for 3 days, a low-salt diet (3.0 g) for 7 days, and a high-salt diet (18.0 g) for an additional 7 days. In addition, the authors studied 514 patients of the Baoji Salt-Sensitive Study, recruited from 124 families who received the same salt intake intervention, and investigated the association of genetic variations in uromodulin gene with salt sensitivity. Plasma uromodulin levels were significantly lower on a high-salt diet than on a baseline diet (28.3 ± 4.5 vs. 54.9 ± 8.8 ng/ml). Daily urinary excretions of uromodulin were significantly decreased on a high-salt diet than on a low-salt diet (28.7 ± 6.7 vs. 157.2 ± 21.7 ng/ml). SNPs rs7193058 and rs4997081 were associated with the diastolic blood pressure (DBP), mean arterial pressure (MAP) responses to the high-salt diet. In addition, several SNPs in the uromodulin gene were significantly associated with pulse pressure (PP) response to the low-salt intervention. This study shows that dietary salt intake affects plasma and urinary uromodulin levels and that uromodulin may play a role in the pathophysiological process of salt sensitivity in the Chinese populations.

Mechanistic interactions of uromodulin with the thick ascending limb: perspectives in physiology and hypertension

Hypertension is a significant risk factor for cardiovascular disease and mortality worldwide. The kidney is a major regulator of blood pressure and electrolyte homeostasis, with monogenic disorders indicating a link between abnormal ion transport and salt-sensitive hypertension. However, the association between salt and hypertension remains controversial. Thus, there is continued interest in deciphering the molecular mechanisms behind these processes. Uromodulin (UMOD) is the most abundant protein in the normal urine and is primarily synthesized by the thick ascending limb epithelial cells of the kidney. Genome-wide association studies have linked common UMOD variants with kidney function, susceptibility to chronic kidney disease and hypertension independent of renal excretory function. This review will discuss and provide predictions on the role of the UMOD protein in renal ion transport and hypertension based on current observational, biochemical, genetic, pharmacological and clinical evidence.

Vasopressin Induces Urinary Uromodulin Secretion By Activating PKA (Protein Kinase A)

[Figure: see text].

Genomics of hypertension: the road to precision medicine

The known genetic architecture of blood pressure now comprises >30 genes, with rare variants resulting in monogenic forms of hypertension or hypotension and >1,477 common single-nucleotide polymorphisms (SNPs) being associated with the blood pressure phenotype. Monogenic blood pressure syndromes predominantly involve the renin-angiotensin-aldosterone system and the adrenal glucocorticoid pathway, with a smaller fraction caused by neuroendocrine tumours of the sympathetic and parasympathetic nervous systems. The SNPs identified in genome-wide association studies (GWAS) as being associated with the blood pressure phenotype explain only approximately 27% of the 30-50% estimated heritability of blood pressure, and the effect of each SNP on the blood pressure phenotype is small. A paucity of SNPs from GWAS are mapped to known genes causing monogenic blood pressure syndromes. For example, a GWAS signal mapped to the gene encoding uromodulin has been shown to affect blood pressure by influencing sodium homeostasis, and the effects of another GWAS signal were mediated by endothelin. However, the majority of blood pressure-associated SNPs show pleiotropic associations. Unravelling these associations can potentially help us to understand the underlying biological pathways. In this Review, we appraise the current knowledge of blood pressure genomics, explore the causal pathways for hypertension identified in Mendelian randomization studies and highlight the opportunities for drug repurposing and pharmacogenomics for the treatment of hypertension.

Hypertension: Current trends and future perspectives

Hypertension is a significant and increasing global health issue. It is a leading cause of cardiovascular disease and premature death worldwide due to its effects on end organs, and through its associations with chronic kidney disease, diabetes mellitus and obesity. Despite current management strategies, many patients do not achieve adequate blood pressure (BP) control. Hypertension-related cardiovascular mortality rates are rising in tandem with the increasing global prevalence of chronic kidney disease, diabetes mellitus and obesity. Improving BP control must therefore be urgently prioritised. Strategies include utilising existing antihypertensive agents more effectively, and using treatments developed for co-existing conditions (such as sodium-glucose cotransporter 2 inhibitors for diabetes mellitus) that offer additional BP-lowering and cardiovascular benefits. Additionally, novel therapeutic agents that target alternative prohypertensive pathways and that offer broader cardiovascular protection are under development, including dual angiotensin receptor-neprilysin inhibitors. Nonpharmacological strategies such as immunotherapy are also being explored. Finally, advancing knowledge of the human genome and molecular modification technology may usher in an exciting new era of personalised medicine, with the potential to revolutionise the management of hypertension.

The Relationship Between Urine Uromodulin and Blood Pressure Changes: The DASH-Sodium Trial

BACKGROUND

Uromodulin modulates the sodium-potassium-two-chloride transporter in the thick ascending limb of the loop of Henle, and its overexpression in murine models leads to salt-induced hypertension. We hypothesized that individuals with higher baseline levels of urine uromodulin would have a greater increase in systolic blood pressure (SBP) for the same increase in sodium compared with those with lower uromodulin levels.

METHODS

We used data from 157 subjects randomized to the control diet of the Dietary Approaches to Stop Hypertension (DASH)-Sodium trial who were assigned to 30 days of low (1,500 mg/d), medium (2,400 mg/d), and high salt (3,300 mg/d) diets in random order. Blood pressure was measured prerandomization and then weekly during each feeding period. We evaluated the association of prerandomization urine uromodulin with change in SBP between diets, as measured at the end of each feeding period, using multivariable linear regression.

RESULTS

Baseline urine uromodulin stratified by tertiles was ≤17.64, 17.65-31.97, and ≥31.98 µg/ml. Across the tertiles, there were no significant differences in SBP at baseline, nor was there a differential effect of sodium diet on SBP across tertiles (low to high, P = 0.81). After adjusting for age, sex, body mass index, and race, uromodulin levels were not significantly associated with SBP change from low to high sodium diet (P = 0.42).

CONCLUSIONS

In a randomized trial of different levels of salt intake, higher urine uromodulin levels were not associated with a greater increase in blood pressure in response to high salt intake.

Uromodulin Isolation and Its N-Glycosylation Analysis by NanoLC-MS/MS

The glycoprotein uromodulin (UMOD) is the most abundant protein in urine, and N-glycans are critical for many biological functions of UMOD. Comprehensive glycan profiling of UMOD provides valuable information to understand the exact mechanisms of glycan-regulated functions. To perform comprehensive glycosylation analysis of UMOD from urine samples with limited volumes, we developed a streamlined workflow that included UMOD isolation from 5 mL of urine from 6 healthy adult donors (3 males and 3 females) and a glycosylation analysis using a highly sensitive and reproducible nanoLC-MS/MS based glycomics approach. In total, 212 N-glycan compositions were identified from the purified UMOD, and 17% were high-mannose glycans, 2% were afucosylated/asialylated, 3% were neutral fucosylated, 28% were sialylated (with no fucose), 46% were fucosylated and sialylated, and 4% were sulfated. We found that isolation of UMOD resulted in a significant decrease in the relative quantity of high-mannose and sulfated glycans with a significant increase of neutral fucosylated glycans in the UMOD-depleted urine relative to the undepleted urine, but depletion had little impact on the sialylated glycans. To our knowledge, this is the first study to perform comprehensive N-glycan profiling of UMOD using nanoLC-MS/MS. This analytical workflow would be very beneficial for studies with limited sample size, such as pediatric studies, and can be applied to larger patient cohorts not only for UMOD interrogation but also for global glycan analysis.

Rationale and Design of the Genotype-Blinded Trial of Torasemide for the Treatment of Hypertension (BHF UMOD)

BACKGROUND

Genome-wide association studies have identified single nucleotide polymorphisms (SNPs) near the uromodulin gene (UMOD) affecting uromodulin excretion and blood pressure (BP). Uromodulin is almost exclusively expressed in the thick ascending limb (TAL) of the loop of Henle and its effect on BP appears to be mediated via the TAL sodium transporter, NKCC2. Loop-diuretics block NKCC2 but are not commonly used in hypertension management. Volume overload is one of the primary drivers for uncontrolled hypertension, so targeting loop-diuretics to individuals who are more likely to respond to this drug class, using the UMOD genotype, could be an efficient precision medicine strategy.

METHODS

The BHF UMOD Trial is a genotype-blinded, multicenter trial comparing BP response to torasemide between individuals possessing the AA genotype of the SNP rs13333226 and those possessing the G allele. 240 participants (≥18 years) with uncontrolled BP, on ≥1 antihypertensive agent for ≥3 months, will receive treatment with Torasemide, 5 mg daily for 16 weeks. Uncontrolled BP is average home systolic BP (SBP) >135 mmHg and/or diastolic BP >85 mmHg. The primary outcome is the change in 24-hour ambulatory SBP area under the curve between baseline and end of treatment. Sample size was calculated to detect a 4 mmHg difference between groups at 90% power. Approval by West of Scotland Research Ethics Committee 5 (16/WS/0160).

RESULTS

The study should conclude August 2021.

CONCLUSIONS

If our hypothesis is confirmed, a genotype-based treatment strategy for loop diuretics would help reduce the burden of uncontrolled hypertension.

CLINICAL TRIALS REGISTRATION

https://clinicaltrials.gov/ct2/show/NCT03354897.

Uromodulin: Roles in Health and Disease

Uromodulin, a protein exclusively produced by the kidney, is the most abundant urinary protein in physiological conditions. Already described several decades ago, uromodulin has gained the spotlight in recent years, since the discovery that mutations in its encoding gene UMOD cause a renal Mendelian disease (autosomal dominant tubulointerstitial kidney disease) and that common polymorphisms are associated with multifactorial disorders, such as chronic kidney disease, hypertension, and cardiovascular diseases. Moreover, variations in uromodulin levels in urine and/or blood reflect kidney functioning mass and are of prognostic value for renal function, cardiovascular events, and overall mortality. The clinical relevance of uromodulin reflects its multifunctional nature, playing a role in renal ion transport and immunomodulation, in protection against urinary tract infections and renal stones, and possibly as a systemic antioxidant. Here, we discuss the multifaceted roles of this protein in kidney physiology and its translational relevance.