Urinary biomarkers at early ADPKD disease stage

Predicting autosomal dominant polycystic kidney disease progression: review of promising Serum and urine biomarkers

Autosomal dominant polycystic kidney disease (ADPKD) is one of the leading causes of end-stage renal disease. In spite of the recent tremendous progress in the understanding of ADPKD pathogenesis, the molecular mechanisms of the disease remain incompletely understood. Considering emerging new targeted therapies for ADPKD, it has become crucial to disclose easily measurable and widely available biomarkers for identifying patients with future rapid disease progression. This review encompasses all the research with a shared goal of identifying promising serum or urine biomarkers for predicting ADPKD progression or response to therapy. The rate of the ADPKD progress varies significantly between patients. The phenotypic variability is only partly explained by the underlying genetic lesion diversity. Considering significant decline in kidney function in ADPKD is not usually evident until at least 50% of the parenchyma has been destroyed, conventional kidney function measures, such as glomerular filtration rate (GFR), are not suitable for monitoring disease progression in ADPKD, particularly in its early stages. Since polycystic kidney enlargement usually precedes the decline in GFR, height-adjusted total kidney volume (ht-TKV) has been accepted as an early biomarker for assessing disease severity in ADPKD patients. However, since measuring ht-TKV is time-consuming and observer-dependent, the identification of a sensitive and quickly measurable biomarker is of a great interest for everyday clinical practice. Throughout the last decade, due to development of proteomic and metabolomic techniques and the enlightenment of multiple molecular pathways involved in the ADPKD pathogenesis, a number of urine and serum protein biomarkers have been investigated in ADPKD patients, some of which seem worth of further exploring. These include copeptin, angiotensinogen, monocyte chemoattractant protein 1, kidney injury molecule-1 and urine-to-plasma urea ratio among many others. The aim of the current review is to provide an overview of all of the published evidence on potentially clinically valuable serum and urine biomarkers that could be used for predicting disease progression or response to therapy in patients with ADPKD. Hopefully, this review will encourage future longitudinal prospective clinical studies evaluating proposed biomarkers as prognostic tools to improve management and outcome of ADPKD patients in everyday clinical practice.

Unveiling the Hidden Power of Uromodulin: A Promising Potential Biomarker for Kidney Diseases

Uromodulin, also known as Tamm-Horsfall protein, represents the predominant urinary protein in healthy individuals. Over the years, studies have revealed compelling associations between urinary and serum concentrations of uromodulin and various parameters, encompassing kidney function, graft survival, cardiovascular disease, glucose metabolism, and overall mortality. Consequently, there has been a growing interest in uromodulin as a novel and effective biomarker with potential applications in diverse clinical settings. Reduced urinary uromodulin levels have been linked to an elevated risk of acute kidney injury (AKI) following cardiac surgery. In the context of chronic kidney disease (CKD) of different etiologies, urinary uromodulin levels tend to decrease significantly and are strongly correlated with variations in estimated glomerular filtration rate. The presence of uromodulin in the serum, attributable to basolateral epithelial cell leakage in the thick ascending limb, has been observed. This serum uromodulin level is closely associated with kidney function and histological severity, suggesting its potential as a biomarker capable of reflecting disease severity across a spectrum of kidney disorders. The UMOD gene has emerged as a prominent locus linked to kidney function parameters and CKD risk within the general population. Extensive research in multiple disciplines has underscored the biological significance of the top UMOD gene variants, which have also been associated with hypertension and kidney stones, thus highlighting the diverse and significant impact of uromodulin on kidney-related conditions. UMOD gene mutations are implicated in uromodulin-associated kidney disease, while polymorphisms in the UMOD gene show a significant association with CKD. In conclusion, uromodulin holds great promise as an informative biomarker, providing valuable insights into kidney function and disease progression in various clinical scenarios. The identification of UMOD gene variants further strengthens its relevance as a potential target for better understanding kidney-related pathologies and devising novel therapeutic strategies. Future investigations into the roles of uromodulin and regulatory mechanisms are likely to yield even more profound implications for kidney disease diagnosis, risk assessment, and management.

PKD1 Mutation Is a Biomarker for Autosomal Dominant Polycystic Kidney Disease

BACKGROUND

Autosomal dominant polycystic kidney disease (ADPKD) occurs in 1 in 500-4000 people worldwide. Genetic mutation is a biomarker for predicting renal dysfunction in patients with ADPKD. In this study, we performed a genetic analysis of Japanese patients with ADPKD to investigate the prognostic utility of genetic mutations in predicting renal function outcomes.

METHODS

Patients clinically diagnosed with ADPKD underwent a panel genetic test for germline mutations in PKD1 and PKD2. This study was conducted with the approval of the Ethics Committee of Juntendo University (no. 2019107).

RESULTS

Of 436 patients, 366 (83.9%) had genetic mutations. Notably, patients with PKD1 mutation had a significantly decreased ΔeGFR/year compared to patients with PKD2 mutation, indicating a progression of renal dysfunction (-3.50 vs. -2.04 mL/min/1.73 m²/year, p = 0.066). Furthermore, PKD1 truncated mutations had a significantly decreased ΔeGFR/year compared to PKD1 non-truncated mutations in the population aged over 65 years (-6.56 vs. -2.16 mL/min/1.73 m²/year, p = 0.049). Multivariate analysis showed that PKD1 mutation was a more significant risk factor than PKD2 mutation (odds ratio, 1.81; 95% confidence interval, 1.11-3.16; p = 0.020).

CONCLUSIONS

The analysis of germline mutations can predict renal prognosis in Japanese patients with ADPKD, and PKD1 mutation is a biomarker of ADPKD.

Urinary Biomarkers in Monitoring the Progression and Treatment of Autosomal Dominant Polycystic Kidney Disease-The Promised Land?

Autosomal dominant polycystic kidney disease (ADPKD) is the most common genetic kidney disease, and it leads to end-stage renal disease (ESRD). The clinical manifestations of ADPKD are variable, with extreme differences observable in its progression, even among members of the same family with the same genetic mutation. In an age of new therapeutic options, it is important to identify patients with rapidly progressive evolution and the risk factors involved in the disease's poor prognosis. As the pathophysiological mechanisms of the formation and growth of renal cysts have been clarified, new treatment options have been proposed to slow the progression to end-stage renal disease. Furthermore, in addition to the conventional factors (PKD1 mutation, hypertension, proteinuria, total kidney volume), increasing numbers of studies have recently identified new serum and urinary biomarkers of the disease's progression, which are cheaper and more easily to dosing from the early stages of the disease. The present review discusses the utility of new biomarkers in the monitoring of the progress of ADPKD and their roles in new therapeutic approaches.

Acetaminophen-Induced Nephrotoxicity: Suppression of Apoptosis and Endoplasmic Reticulum Stress Using Boric Acid

Acetaminophen (APAP) is one of the popular and safe pain medications worldwide. However, due its wide availability, it is frequently implicated in intentional or unintentional overdoses where it can cause severe liver injury and even acute liver failure. Boron is a bioactive trace element, found naturally as boric acid (BA) and borate. In this study, the effects of boric acid on the acute renal toxicity induced by APAP in rats were researched in comparison with N-acetyl cysteine (NAC). In the study, 7 groups were formed and 2 g/kg dose of paracetamol per rat was prepared by suspending in 1% Carboxy Methyl Cellulose (CMC) solution of phosphate buffer saline (PBS). Boric acid dissolved in saline was administered to experimental animals by gavage at doses of 50, 100, and 200 mg/kg. In this study, ER stress and apoptosis formed by paracetamol-induced nephrotoxicity were investigated. This purpose determined iNOS, PERK, ATF6, NFkB p53, caspases 3, 12, bcl-2, and bcl-xL gene mRNA expression kidney tissue. Also, the levels of kidney injury molecule-1 (KIM-1), Cysteine (Cys), and IL-18 levels, which are mentioned today as kidney damage markers were compared with BUN and creatine levels. The effect of boron on kidney damage was determined by histopathologic. Data were statistically analyzed by using SPSS-20 ANOVA and stated as means and standard deviation. According to the data obtained in our study, we believe that boric acid has a protective effect on the negative effects of paracetamol on the kidney. We believe that our study will provide useful data to the literature on the possibility of a supplement to be used as an active compound in paracetamol for the prophylaxis of boric acid and it can also be converted into a useful product.

A Systematic Review of Reported Outcomes in ADPKD Studies

Introduction

Methods

Results

Conclusion

Improving kidney targeting: The influence of nanoparticle physicochemical properties on kidney interactions

Kidney-targeted nanoparticles have become of recent interest due to their potential to deliver drugs directly to diseased tissue, decrease off-target adverse effects, and increase overall tolerability to patients with chronic kidney disease that require lifelong drug exposure. Given the physicochemical properties of nanoparticles can drastically affect their ability to extravasate past cellular and biological barriers and access the kidneys, we surveyed the literature from the past decade and analyzed how nanoparticle size, charge, shape, and material density affects passage and interaction with the kidneys. Specifically, we found that nanoparticle size impacted the mechanism of nanoparticle entry into the kidneys such as glomerular filtration or tubular secretion. In addition, we found charge, aspect ratio, and material density influences nanoparticle renal retention and provide insights for designing nanoparticles for passive kidney targeting. Finally, we conclude by highlighting active targeting strategies that bolster kidney retention and discuss the clinical status of nanomedicine for kidney diseases.

Association between urinary biomarkers and disease progression in adults with autosomal dominant polycystic kidney disease

Background

Height-adjusted total kidney volume (htTKV) is considered as the best predictor of kidney function in patients with autosomal dominant polycystic kidney disease (ADPKD), but its limited predictive capacity stresses the need to find new biomarkers of ADPKD progression. The aim of this study was to investigate urinary biomarkers of ADPKD progression.

Methods

This observational study included ADPKD patients, and two comparator groups of ischaemic and non-ischaemic kidney injury: benign nephroangiosclerosis patients and non-ischaemic chronic kidney disease (CKD) patients. Proteinuria, htTKV and urinary levels of molecules are associated with ischaemia and/or tubular injury. The slope of estimated glomerular filtration rate (eGFR) was used as a dependent variable in univariate and multivariate models of kidney function decline.

Results

The study included 130 patients with ADPKD, 55 with nephroangiosclerosis and 40 with non-ischaemic CKD. All patients had increased urinary concentrations of biomarkers associated with tubular lesions (liver fatty acid-binding protein, kidney injury molecule-1, β2-microglobulin) and molecules overexpressed under ischaemic conditions [hypoxia-inducible factor-1α, vascular endothelial growth factor (VEGF) and monocyte chemoattractant protein-1 (MCP-1)]. These biomarkers correlated positively with htTKV and negatively with the eGFR slope. htTKV was the single best predictor of the eGFR slope variability in univariate analyses. However, a multivariate model including urinary levels of β2-microglobulin, MCP-1 and VEGF improved the capacity to predict the decline of eGFR in ADPKD patients compared with htTKV alone.

Conclusions

The urinary levels of molecules associated with either renal ischaemia (VEGF and MCP-1) or tubular damage (β2-microglobulin) are associated with renal function deterioration in ADPKD patients, and are, therefore, candidates as biomarkers of ADPKD progression.

KIM-1 and Kidney Disease Progression in Autosomal Dominant Polycystic Kidney Disease: HALT-PKD Results

BACKGROUND

Cyst compression of renal tubules plays a role in the progression of autosomal dominant polycystic kidney disease (ADPKD) and may induce expression of kidney injury molecule-1 (KIM-1). Whether urinary KIM-1 indexed for creatinine (uKIM-1/Cr) is a prognostic marker of disease progression in ADPKD is unknown.In this secondary analysis of a prospective cohort study, we sought to determine whether patients with high as opposed to low uKIM-1/CR at baseline had greater rates of eGFR loss and height-adjusted total kidney volume (HtTKV) increase.

METHODS

Baseline uKIM-1/Cr values were obtained from 754 participants in Halt Progression of Polycystic Kidney Disease (HALT-PKD) studies A (early ADPKD) and B (late ADPKD). The predictor was uKIM-1/Cr, which was dichotomized by a median value of 0.2417 pg/g, and the primary outcomes were measured longitudinally over time. Mixed-effects linear models were used in the analysis to calculate the annual slope of change in eGFR and HtTKV.

RESULTS

Patients with high uKIM-1/Cr (above the median) had an annual decline in eGFR that was 0.47 mL/min greater than that in those with low uKIM-1/Cr (p = 0.0015) after adjustment for all considered covariates. This association was seen in study B patients alone (0.45 mL/min; p = 0.009), but not in study A patients alone (0.42 mL/min; p = 0.06). High baseline uKIM-1/Cr was associated with higher HtTKV in the baseline cross-sectional analysis compared to low uKIM-1/Cr (p = 0.02), but there was no difference between the groups in the mixed-effects model annual slopes.

CONCLUSION

Elevated baseline uKIM-1/Cr is associated with a greater decline in eGFR over time. Further research is needed to determine whether uKIM-1/Cr improves risk stratification in patients with ADPKD.

Urinary Angiotensinogen in addition to Imaging Classification in the Prediction of Renal Outcome in Autosomal Dominant Polycystic Kidney Disease

BACKGROUND

Intrarenal renin-angiotensin system (RAS) is known to play the major role in the development of hypertension and renal progression in autosomal dominant polycystic kidney disease (ADPKD). Urinary angiotensinogen to creatinine ratio (AGT/Cr) was suggested as a novel biomarker to reflect intrarenal RAS activity. This study was performed to evaluate urinary AGT/Cr as a predictive biomarker for renal function decline in addition to imaging classification in a prospective ADPKD cohort.

METHODS

From 2011 to 2016, a total of 364 ADPKD patients were enrolled in the prospective cohort called the KoreaN Cohort Study for Outcomes in Patients With Chronic Kidney Disease (KNOW-CKD). Among them, a total of 207 subjects in chronic kidney disease stage 1-4 with baseline urinary AGT and total kidney volume and subsequent renal function follow-up data over more than 1 year were included in the analysis. Patients were defined as slow progressors (SP) if they are classified as 1A or 1B by imaging classification whereas rapid progressors (RP) if they are classified as 1C-1E. Patients were divided according to AGT/Cr quartiles and annual estimated glomerular filtration rate (eGFR) slope was compared among highest quartile (hAGT group) and the rest of quartiles (lAGT group). Patients were divided into 4 groups to evaluate the predictive value of urinary AGT/Cr in addition to imaging classification: SP/lAGT, SP/hAGT, RP/lAGT, and RP/hAGT. The Cox regression model was used to evaluate the hazard ratio (HR) between groups.

RESULTS

The mean age was 45.9 years and 88.9% had hypertension. Baseline eGFR was 79.0 ± 28.4 mL/min/1.73 m² and median height-adjusted total kidney volume was 788.2 (471.2; 1,205.2) mL/m. The patients in the hAGT group showed lower eGFR (72.4 ± 24.8 vs. 81.1 ± 29.2 mL/min/1.73 m², P = 0.039), lower plasma hemoglobin (13.0 ± 1.4 vs. 13.7 ± 1.6 g/dL, P = 0.007), higher urinary protein to creatinine ratio (0.14 [0.09, 0.38] vs. 0.07 [0.04, 0.12] g/g, P = 0.007) compared to the lAGT group. The hAGT group was an independent risk factor for faster eGFR decline after adjusting for gender, RP, baseline eGFR, and other known risk factors. During median follow-up duration of 4.6 years, a total of 29 renal events (14.0%) occurred. The SP/hAGT group showed significantly higher risk of developing renal outcome compared to SP/lAGT group (HR, 13.4; 95% confidence interval, 1.282-139.324; P = 0.03).

CONCLUSION

Urinary AGT/Cr can be a useful predictive marker in the patients with relatively small ADPKD. Various biomarkers should be considered to define RP when implementing novel treatment in the patients with ADPKD.

Tubular STAT3 Limits Renal Inflammation in Autosomal Dominant Polycystic Kidney Disease

BACKGROUND

The inactivation of the ciliary proteins polycystin 1 or polycystin 2 leads to autosomal dominant polycystic kidney disease (ADPKD). Although signaling by primary cilia and interstitial inflammation both play a critical role in the disease, the reciprocal interactions between immune and tubular cells are not well characterized. The transcription factor STAT3, a component of the cilia proteome that is involved in crosstalk between immune and nonimmune cells in various tissues, has been suggested as a factor fueling ADPKD progression.

METHOD

To explore how STAT3 intersects with cilia signaling, renal inflammation, and cyst growth, we used conditional murine models involving postdevelopmental ablation of Pkd1, Stat3, and cilia, as well as cultures of cilia-deficient or STAT3-deficient tubular cell lines.

RESULTS

Our findings indicate that, although primary cilia directly modulate STAT3 activation in vitro, the bulk of STAT3 activation in polycystic kidneys occurs through an indirect mechanism in which primary cilia trigger macrophage recruitment to the kidney, which in turn promotes Stat3 activation. Surprisingly, although inactivating Stat3 in Pkd1-deficient tubules slightly reduced cyst burden, it resulted in a massive infiltration of the cystic kidneys by macrophages and T cells, precluding any improvement of kidney function. We also found that Stat3 inactivation led to increased expression of the inflammatory chemokines CCL5 and CXCL10 in polycystic kidneys and cultured tubular cells.

CONCLUSIONS

STAT3 appears to repress the expression of proinflammatory cytokines and restrict immune cell infiltration in ADPKD. Our findings suggest that STAT3 is not a critical driver of cyst growth in ADPKD but rather plays a major role in the crosstalk between immune and tubular cells that shapes disease expression.

Urinary Uromodulin/Creatinine Ratio as a Potential Clinical Biomarker for Chronic Kidney Disease Patients with Gout: A Pilot Study

OBJECTIVE

Recent studies have reported that reduced excretion of urinary uromodulin is associated with renal tubular function and risks of progressive kidney disease. Gouty nephropathy is usually seen in patients with gout. Patients with chronic gouty nephropathy are characterized by the deposition of monosodium urate crystals primarily involving the collecting ducts in the medulla. We postulated that this correlation may be specific to gout and may serve as a useful biomarker for chronic kidney disease (CKD).

MATERIALS AND METHODS

A total of 114 Taiwanese patients diagnosed with gout (n = 72), CKD (n = 26), or healthy volunteers (n = 16) were prospectively enrolled for this study from the Rheumatology and Nephrology Outpatient Clinics of our institution. We obtained urine and blood samples on patient visits to the outpatient clinics. Demographic data were obtained from medical records.

RESULTS

In patients with gout, the spot urinary uromodulin/creatinine ratio (uUMCR; mg/g) in patients with CKD was significantly lower than that in those without CKD (CKD group: 2.2; non-CKD group: 5.6, p = 0.005). Multivariate analysis revealed that patients with CKD and gout had a lower uUMCR than those with gout alone (p = 0.028). A significant association was not observed in our non-gout cohort.

CONCLUSION

The association of decreased uUMCR with CKD status was identified only in patients with gout in the present study. We believe that uUMCR might serve as an indicator of differential CKD in patients with gout.

Early Urinary Biomarkers in Pediatric Autosomal Dominant Polycystic Kidney Disease (ADPKD): No Evidence in the Interest of Urinary Neutrophil Gelatinase-Associated Lipocalin (uNGAL)

Background: Autosomal Dominant Polycystic Kidney Disease (ADPKD) is increasingly diagnosed during childhood by the presence of renal cysts in patients with a positive familial history. No curative treatment is available and early detection and diagnosis confronts pediatricians with the lack of early markers to decide whether to introduce renal-protective agents and prevent the progression of renal failure. Neutrophil Gelatinase-Associated Lipocalin (NGAL) is a tubular protein that has been recently proposed as an early biomarker of renal impairment in the ADPKD adult population. Methods: Urinary NGAL (uNGAL) levels were measured in 15 ADPKD children and compared with 15 age and gender matched controls using parametric, non-parametric, and Bayesian statistics. We also tested the association of uNGAL levels with markers of disease progression, such as proteinuria, albuminuria, blood pressure, and Total Kidney Volume (TKV) using correlation analysis. TKV was calculated by ultrasound, using the ellipsoid method. Results: No difference in mean uNGAL levels was observed between groups (ADPKD: 26.36 ng/ml; Controls: 27.24 ng/ml; P = 0.96). Moreover, no correlation was found between uNGAL and proteinuria (P = 0.51), albuminuria (P = 0.69), TKV (P = 0.68), or mean arterial pressure (P = 0.90). By contrast, TKV was positively correlated with proteinuria (P = 0.04), albuminuria (P = 0.001), and mean arterial pressure (P = 0.03). Conclusion: uNGAL did not confirm its superiority as a marker of disease progression in a pediatric ADPKD population. In the contrary, TKV appears to be an easy measurable variable and may be promising as a surrogate marker to follow ADPKD progression in children.

A Clinical Patient Reporting Tool: Giving ADPKD Patients Back Their Data

Klinischer Patientenbericht: ADPKD-Patienten erhalten Zugriff auf ihre Daten

Zusammenfassung. Studien zur Patientenbeteiligung in der medizinischen Versorgung deuten darauf hin, dass eine intensive Patientenbeteiligung die Gesundheit verbessert und die Vorsorgungszufriedenheit erhöht. Insbesondere bei Behandlungsentscheidungen, die sowohl Schaden als auch Nutzen verursachen, sind gemeinsame Entscheidungen von Patienten und Ärzten entscheidend um den Patienten auf den Behandlungsplan vorbereitet und ihn dafür zu motivieren. Allerdings sind Instrumente, die den Patienten in den klinischen Versorgungsprozess und gemeinsamen Entscheidungsfindung einbeziehen, nicht weit verbreitet. Wir entwickelten ein klinisches Patientendokument für Patienten mit autosomal-dominanter polyzystischer Nierenerkrankung (ADPKD), für die kürzlich eine neue Therapie – Tolvaptan, das die Progression verlangsamt, aber bemerkenswerte Nebenwirkungen hat – zur Verfügung steht. Untersuchungen vor und nach der Entwicklung zeigten, dass ADPKD-Patienten eine Anzeige individueller Schweregradindikatoren mit Benchmarks für vergleichbare Patienten wünschen. Die Kommunikation wird erleichtert und das Vertrauen der Patienten in die gemeinsam gefällten Behandlungsentscheidungen verbessert. Ein solcher Patientenbericht ist leicht auf andere Krankheitsbilder übertragbar und könnte als ein Aspekt eines Patienteninterventionsmodells in klinischen Zentren dienen.

Baseline total kidney volume and the rate of kidney growth are associated with chronic kidney disease progression in Autosomal Dominant Polycystic Kidney Disease

Autosomal dominant polycystic kidney disease (ADPKD) is characterized by progressive enlargement of kidney cysts leading to chronic kidney disease (CKD) and end-stage renal disease (ESRD). Identification of an early biomarker that can predict progression of CKD is urgently needed. In an earlier Consortium for Radiologic Imaging Studies of Polycystic Kidney Disease (CRISP) study (a prospective, multicenter, observational analysis of 241 patients with ADPKD initiated in 2000), baseline height-adjusted total kidney volume (htTKV) was shown to be associated with development of CKD stage 3 after eight years of follow-up. Here we conducted an extended study and found that in a multivariable logistic regression model, baseline htTKV was shown to be a strong, independent predictor for the development of CKD after a median follow-up of 13 years. The odds ratio of reaching each CKD stage per 100 mL/m increment in htTKV was 1.38 (95% confidence interval 1.19-1.60) for stage 3, 1.42 (1.23-1.64) for stage 4, and 1.35 (1.18-1.55) for stage 5 or ESRD. Baseline htTKV was also associated with relative decreases in the glomerular filtration rate of 30%, and 57% or more. Moreover, the rate of change in htTKV was negatively correlated with the slope of the glomerular filtration rate. While ADPKD genotype was also associated with CKD outcomes, it was not an independent prognostic factor after adjusting for htTKV. Thus, baseline total kidney volume and the rate of kidney growth are strongly associated with the development of advanced stages of CKD. These findings support the use of total kidney volume as a prognostic and potentially monitoring biomarker in ADPKD.

Association Between Urinary Alpha1-Microglobulin Levels and Nonalcoholic Fatty Liver Disease: A Cross-Sectional Study

BACKGROUND

We aimed to explore the association between urinary alpha1-microglobulin (A1M) levels and nonalcoholic fatty liver disease (NAFLD) in a Chinese population.

STUDY

We performed a cross-sectional study among 2,215 Chinese who attended their annual health examination at First Affiliated Hospital, College of Medicine, Zhejiang University. Urinary A1M-creatinine ratio and other clinical and laboratory parameters were measured.

RESULTS

A total of 20.9% of subjects fulfilled the diagnostic criteria of NAFLD. NAFLD subjects had significantly higher urinary A1M-creatinine ratios. These levels were positively associated with NAFLD prevalence. The association between A1M-creatinine ratio and NAFLD was independent of hyperglycemia status. Stepwise regression showed that urinary A1M-creatinine ratio was significantly associated with the risk for NAFLD. Urinary A1M-creatinine ratio was an independent factor predicting advanced fibrosis (FIB-4 ≥1.3) in NAFLD patients.

CONCLUSIONS

Our results showed a significant association between urinary A1M-creatinine ratio and NAFLD.

Insights into cellular and molecular basis for urinary tract infection in autosomal-dominant polycystic kidney disease

Urinary tract infection (UTI) is a broad term referring to an infection of the kidneys, ureters, bladder, and/or urethra. Because of its prevalence, frequent recurrence, and rising resistance to antibiotics, UTI has become a challenge in clinical practice. Autosomal-dominant polycystic kidney disease (ADPKD) is the most common monogenic disorder of the kidney and is characterized by the growth of fluid-filled cysts in both kidneys. Progressive cystic enlargement, inflammation, and interstitial fibrosis result in nephron loss with subsequent decline in kidney function. ADPKD patients frequently develop UTI; however, the cellular and molecular mechanisms responsible for the high UTI incidence in ADPKD patients remain virtually unaddressed. Emerging evidence suggests that α-intercalated cells (α-ICs) of the collecting ducts function in the innate immune defense against UTI. α-ICs inhibit bacterial growth by acidifying urine and secreting neutrophil gelatinase-associated lipocalin (NGAL) that chelates siderophore-containing iron. It is necessary to determine, therefore, if ADPKD patients with recurrent UTI have a reduced number and/or impaired function of α-ICs. Identification of the underlying cellular and molecular mechanisms may lead to the development of novel strategies to reduce UTI in ADPKD.

Urinary Biomarkers to Identify Autosomal Dominant Polycystic Kidney Disease Patients With a High Likelihood of Disease Progression

Introduction

The variable disease course of autosomal dominant polycystic kidney disease (ADPKD) makes it important to develop biomarkers that can predict disease progression, from a patient perspective and to select patients for renoprotective treatment. We therefore investigated whether easy-to-measure urinary biomarkers are associated with disease progression and have additional value over that of conventional risk markers.

Methods

At baseline, inflammatory, glomerular, and tubular damage markers were measured in 24-hour urine collections (albumin, IgG, kidney injury molecule−1 (KIM-1), N-acetyl-β-d-glucosaminidase (NAG), β2 microglobulin (β2MG), heart-type fatty acid binding protein (HFABP), macrophage migration inhibitory factor (MIF), neutrophil gelatinase-associated lipocalin (NGAL), and monocyte chemotactic protein−1 (MCP-1). Disease progression was expressed as annual change in estimated glomerular filtration rate (eGFR, Chronic Kidney Disease EPIdemiology equation), measured glomerular filtation rate (mGFR, using ¹²⁵I-iothalamate), or height-adjusted total kidney volume (htTKV). Multivariable linear regression was used to assess associations of these markers independent of conventional risk markers.

Results

A total of 104 ADPKD patients were included (40 ± 11 years, 39% female, eGFR 77 ± 30, mGFR 79 ± 30 ml/min per 1.73 m² and htTKV 852 [510−1244] ml/m). In particular, β2MG and MCP-1 were associated with annual change in eGFR, and remained associated after adjustment for conventional risk markers (standardized β = −0.35, P = 0.001, and standardized β = −0.29, P = 0.009, respectively). Adding β2MG and MCP-1 to a model containing conventional risk markers that explained annual change in eGFR significantly increased the performance of the model (final R² = 0.152 vs. 0.292, P = 0.001). Essentially similar results were obtained when only patients with an eGFR ≥ 60 ml/min per 1.73 m² were selected, or when change in mGFR was studied. Associations with change in htTKV were less strong.

Conclusion

Urinary β2MG and MCP-1 excretion were both associated with GFR decline in ADPKD, and had added value beyond that of conventional risk markers. These markers therefore have the potential to serve as predictive tools for clinical practice.

Correlations between renal function and the total kidney volume measured on imaging for autosomal dominant polycystic kidney disease: A systematic review and meta-analysis

PURPOSE

To provide a systematic summary of total kidney volume (TKV) as an imaging biomarker in clinical trials for autosomal dominant polycystic kidney disease (ADPKD), focusing on the correlation between TKV and renal function.

METHODS

A computerized literature search was performed using MEDLINE and EMBASE databases for studies that evaluated the correlation between TKV and the glomerular filtration rate (GFR) and between the TKV growth rate and GFR decline rate. A meta-analysis was performed to generate the summary correlation coefficient (r). A qualitative review was performed to evaluate the characteristics of TKV as an imaging biomarker.

RESULTS

Eighteen articles including a total sample size of 2835 patients were retrieved. Meta-analysis revealed substantial correlations between TKV and GFR [r, -0.520; 95% confidence interval (CI), -0.60 to -0.43] and between the TKV growth rate and GFR decline rate [r, -0.320; 95% CI, -0.54 to -0.10]. The quantitative review revealed that baseline TKV can affect the TKV growth rate and GFR decline rate, such that patients with a higher baseline TKV showed faster TKV growth and GFR decline. There was significant variability in image acquisition and analysis methods.

CONCLUSION

There were significant negative correlations between TKV and GFR as well as between TKV growth and GFR decline rates, suggesting that TKV imaging is a useful biomarker in clinical trials. However, standardization-or at least trial-specific standardization-of image acquisition and analysis techniques is required to use TKV as a reliable biomarker.

Temporal and geographical external validation study and extension of the Mayo Clinic prediction model to predict eGFR in the younger population of Swiss ADPKD patients

Background

Prediction models in autosomal dominant polycystic kidney disease (ADPKD) are useful in clinical settings to identify patients with greater risk of a rapid disease progression in whom a treatment may have more benefits than harms. Mayo Clinic investigators developed a risk prediction tool for ADPKD patients using a single kidney value. Our aim was to perform an independent geographical and temporal external validation as well as evaluate the potential for improving the predictive performance by including additional information on total kidney volume.

Methods

We used data from the on-going Swiss ADPKD study from 2006 to 2016. The main analysis included a sample size of 214 patients with Typical ADPKD (Class 1). We evaluated the Mayo Clinic model performance calibration and discrimination in our external sample and assessed whether predictive performance could be improved through the addition of subsequent kidney volume measurements beyond the baseline assessment.

Results

The calibration of both versions of the Mayo Clinic prediction model using continuous Height adjusted total kidney volume (HtTKV) and using risk subclasses was good, with R² of 78% and 70%, respectively. Accuracy was also good with 91.5% and 88.7% of the predicted within 30% of the observed, respectively. Additional information regarding kidney volume did not substantially improve the model performance.

Conclusion

The Mayo Clinic prediction models are generalizable to other clinical settings and provide an accurate tool based on available predictors to identify patients at high risk for rapid disease progression.

Long-term effect of coffee consumption on autosomal dominant polycystic kidneys disease progression: results from the Suisse ADPKD, a Prospective Longitudinal Cohort Study

Background

Previous in vitro experiments of human polycystic kidney disease (PKD) cells reported that caffeine is a risk factor for the promotion of cyst enlargement in patients with autosomal dominant PKD (ADPKD). The relentless progression of ADPKD inclines the majority of physicians to advocate minimization of caffeine consumption despite the absence of clinical data supporting such a recommendation so far. This is the first clinical study to assess prospectively the association between coffee consumption and disease progression in a longitudinal ADPKD cohort.

Methods

Information on coffee consumption and disease progression was collected at each follow-up visit using standardized measurement methods. The main model for the outcomes, kidney size (height-adjusted total kidney volume, htTKV) and kidney function (estimated glomerular filtration rate, eGFR), was a linear mixed model. Patients entered the on-going Swiss ADPKD study between 2006 and June 2014 and had at least 1 visit every year. The sample size of the study population was 151 with a median follow-up of 4 visits per patient and a median follow-up time of 4.38 years.

Results

After multivariate adjustment for age, smoking, hypertension, sex, body mass index and an interaction term (coffee*visit), coffee drinkers did not have a statistically significantly different kidney size compared to non-coffee drinkers (difference of −33.03 cm³ height adjusted TKV, 95% confidence interval (CI) from −72.41 to 6.34, p = 0.10). After the same adjustment, there was no statistically significant difference in eGFR between coffee and non-coffee drinkers (2.03 ml/min/1.73 m², 95% CI from −0.31 to 4.31, p = 0.089).

Conclusion

Data derived from our prospective longitudinal study do not confirm that drinking coffee is a risk factor for ADPKD progression.

Electronic supplementary material

The online version of this article (doi:10.1007/s40620-017-0396-8) contains supplementary material, which is available to authorized users.

An Empirical Biomarker-Based Calculator for Cystic Index in a Model of Autosomal Recessive Polycystic Kidney Disease-The Nieto-Narayan Formula

Autosomal recessive polycystic kidney disease (ARPKD) is associated with progressive enlargement of the kidneys fuelled by the formation and expansion of fluid-filled cysts. The disease is congenital and children that do not succumb to it during the neonatal period will, by age 10 years, more often than not, require nephrectomy+renal replacement therapy for management of both pain and renal insufficiency. Since increasing cystic index (CI; percent of kidney occupied by cysts) drives both renal expansion and organ dysfunction, management of these patients, including decisions such as elective nephrectomy and prioritization on the transplant waitlist, could clearly benefit from serial determination of CI. So also, clinical trials in ARPKD evaluating the efficacy of novel drug candidates could benefit from serial determination of CI. Although ultrasound is currently the imaging modality of choice for diagnosis of ARPKD, its utilization for assessing disease progression is highly limited. Magnetic resonance imaging or computed tomography, although more reliable for determination of CI, are expensive, time-consuming and somewhat impractical in the pediatric population. Using a well-established mammalian model of ARPKD, we undertook a big data-like analysis of minimally- or non-invasive blood and urine biomarkers of renal injury/dysfunction to derive a family of equations for estimating CI. We then applied a signal averaging protocol to distill these equations to a single empirical formula for calculation of CI. Such a formula will eventually find use in identifying and monitoring patients at high risk for progressing to end-stage renal disease and aid in the conduct of clinical trials.