Autoptic aspects in a case of autosomal dominant polycystic kidney disease.

Background: Polycystic kidney disease is a cystic genetic disease. There are two forms: an autosomal dominant one, more common and typical of adults, and an autosomal recessive one, rarer and present in childhood. The autosomal dominant form is caused by genetic mutations of the PKD1 gene in 85% of cases and of PKD2 in 10-15% of cases. Case Report: We reported a case of 56-year-old woman with ADPKD, who had a kidney transplant and who was hospitalized for respiratory failure from Covid 19 disease. She was intubated, sedated and dialyzed, treated with antibiotics, immunosuppressants, diuretics and heparin. CT scan of the abdomen showed multiple cysts of various sizes in the liver and multiple cysts in the kidneys. The patient died after 20 days because she was unresponsive to therapy. The autopsy showed milky ascitic fluid in the abdomen, massive gastric haemor-rhage, intestinal fungal plaques, hepatic and renal polycystosis. The kidneys measured a total of 27 cm with a total weight of about 9 kg. The liver parenchyma appeared cavernous with multiple cysts. The kidney cysts contained bloody liquid. Conclusions: The case demonstrates how important it is in these subjects to evaluate not only the kidneys but also the liver which could present polycystosis and cause liver failure, affecting the severity of the pathology and death. This data is important to emphasize in the clinical management of these patients a close monitoring of liver function also from a preventative perspective in life.

Single-Base Substitution Causing Dual-Exon Skipping Event in PKD2 Gene: Unusual Molecular Finding from Exome Sequencing in a Patient with Autosomal Dominant Polycystic Kidney Disease.

Background: Pathogenic variants in the Polycystic Kidney Disease 2 (PKD2) gene are associated with Autosomal Dominant Polycystic Kidney Disease (ADPKD) in approximately 30% of cases. In recent years, the high-throughput sequencing techniques have significantly increased the number of variants identified in affected patients. Here, we described the peculiar effect of a PKD2 splicing variant, the c.1717-2A>G, identified in an Italian male patient with ADPKD. This variant led to the unusual and rare skipping of two consecutive exons, causing a large in-frame deletion. Methods: The genetic evaluation of the patient was performed using the Next-Generation Sequencing (NGS) assay Clinical Exome Solution® (SOPHiA Genetics). Bioinformatics analysis was performed using the SOPHiA DDM platform (SOPHiA Genetics). Prediction of pathogenicity was carried out by integrating several in silico tools. RNA evaluation was performed to test the effect of the variant on the PKD2 splicing using a Reverse-Transcription PCR coupled with cDNA sequencing. Results: NGS revealed the presence of the PKD2 c.1717-2A>G variant that lies in the canonical splice site of intron 7. This rare variant was predicted to have a significant impact on the splicing, proved by the RNA-based analysis. We identified the presence of a transcript characterised by the simultaneous skipping of exons 8 and 9, with a retained reading frame and the merging of exons 7-10. Conclusions: We described for the first time a dual-exon skip event related to the presence of a single-base substitution in the PKD2 gene in an ADPKD-affected patient. We assumed that the molecular basis of such a rare mechanism lies in the specific order of intron removal. The finding represents novel evidence of an alternative and unusual splicing mechanism in the PKD2 gene, adding insights to the pathogenesis of the ADPKD.

Acyl-CoA thioesterase 13 (ACOT13) attenuates the progression of autosomal dominant polycystic kidney disease in vitro via triggering mitochondrial-related cell apoptosis.

PURPOSE: Autosomal dominant polycystic kidney disease (ADPKD) is the most common cause of end-stage kidney disease. It has been shown that Acyl-CoA thioesterase 13 (ACOT13) level was reduced in renal cystic tissues from ADPKD patients. However, the role of ACOT13 in ADPKD remains largely elusive. METHODS: The data in the GSE7869 dataset were acquired from the GEO database to determine ACOT13 level between normal renal cortical tissues and renal cystic tissues. Next, the potential functions of ACOT13 were explored by gene set enrichment analysis (GSEA). Furthermore, ACOT13 level in ADPKD cells (WT9-12) was verified by RT-qPCR. The effects of ACOT13 on WT9-12 cell growth were evaluated using the EdU staining and flow cytometry assays. RESULTS: Compared to normal group, ACOT13 mRNA level was obviously reduced in renal cystic tissues and WT9-12 cells. Meanwhile, GSEA results showed that compared to the low ACOT13 expression group, PI3K-Akt and MAPK signaling pathways were inactivated, and PPAR signaling pathway and fatty acid metabolism were activated in high ACOT13 expression group. Furthermore, overexpression of ACOT13 notably reduced WT9-12 cell proliferation and triggered cell cycle arrest. Moreover, ACOT13 overexpression remarkably triggered apoptosis, increased cleaved caspase 3 protein level, reduced ATP production and induced loss of mitochondrial membrane potential in WT9-12 cells, suggesting that ACOT13 overexpression could trigger mitochondrial-related apoptosis in WT9-12 cells. CONCLUSIONS: Collectively, our results showed that overexpression of ACOT13 could suppress WT9-12 cell proliferation and trigger mitochondrial-mediated cell apoptosis, suggesting that ACOT13 may exert a protective role in ADPKD.

A Novel Monoallelic ALG5 Variant Causing Late-Onset ADPKD and Tubulointerstitial Fibrosis.

Introduction: Monoallelic variants in the ALG5 gene encoding asparagine-linked glycosylation protein 5 homolog (ALG5) have been recently shown to disrupt polycystin-1 (PC1) maturation and trafficking via underglycosylation, causing an autosomal dominant polycystic kidney disease-like (ADPKD-like) phenotype and interstitial fibrosis. In this report, we present clinical, genetic, histopathologic, and protein structure and functional correlates of a new ALG5 variant, p.R79W, that we identified in 2 distant genetically related Irish families displaying an atypical late-onset ADPKD phenotype combined with tubulointerstitial damage. Methods: Whole exome and targeted sequencing were used for segregation analysis of available relatives. This was followed by immunohistochemistry examinations of kidney biopsies, and targeted (UMOD, MUC1) and untargeted plasma proteome and N-glycomic studies. Results: We identified a monoallelic ALG5 variant [GRCh37 (NM_013338.5): g.37569565G>A, c.235C>T; p.R79W] that cosegregates in 23 individuals, of whom 18 were clinically affected. We detected abnormal localization of ALG5 in the Golgi apparatus of renal tubular cells in patients' kidney specimens. Further, we detected the pathological accumulation of uromodulin, an N-glycosylated glycosylphosphatidylinositol (GPI)-anchored protein, in the endoplasmic reticulum (ER), but not mucin-1, an O- and N-glycosylated protein. Biochemical investigation revealed decreased plasma and urinary uromodulin levels in clinically affected individuals. Proteomic and glycoproteomic profiling revealed the dysregulation of chronic kidney disease (CKD)-associated proteins. Conclusion: ALG5 dysfunction adversely affects maturation and trafficking of N-glycosylated and GPI anchored protein uromodulin, leading to structural and functional changes in the kidney. Our findings confirm ALG5 as a cause of late-onset ADPKD and provide additional insight into the molecular mechanisms of ADPKD-ALG5.

Total kidney volume in autosomal dominant polycystic kidney disease: intraobserver and interobserver agreement of two methods with MRI.

Background/aim: Total kidney volume (TKV) is a parameter used in both treatment decision and follow-up in autosomal dominant polycystic kidney disease (ADPKD) patients. The objective of this study was to evaluate intra- and interobserver agreement of the ellipsoid formula (EF) and manual boundary tracing method (MBTM) used in TKV measurement of ADPKD patients across different levels of experience radiologists. Additionally, the study aimed to evaluate the correlation between the EF and MBTM, which is considered the gold standard for TKV. Materials and methods: A retrospective evaluation was conducted on magnetic resonance imaging (MRI) data from 55 ADPKD patients who underwent abdominal MRI between January 2017 and November 2021 to evaluate TKV. TKV measurements were performed by three independent observers (observer 1, an abdominal imaging radiologist with 5 years of experience; observer 2, a fourth-year radiology resident; observer 3, a second-year radiology resident).To assess intraobserver variability, all observers repeated the measurements at two-week intervals. The ICC was used to assess both intraobserver and interobserver variability. A comparison of the two methods was performed by linear regression for all three observers. Results: The ICC (95% CI) indicated excellent agreement between the observers for both methods (among all observers, p < 0.001). Furthermore, excellent intraobserver agreement was found between all observer measurements either EF or MBTM based on ICC (95% CI) (p < 0.001). The results of the linear regression analysis demonstrated high correlations between the two methods in all three observers (r = 0.992, p < 0.001 for the first observer; r = 0.975, p < 0.001 for the second observer; r = 0.989, p < 0.001 for the third observer). Conclusion: Both the EF and MBTM methods used for the measurement of TKV provided excellent intra- and interobserver reproducibility. The EF is as accurate and precise as the MBTM. It may therefore be preferred in radiology departments with heavy workload, as it is a reliable method for rapid and easy assessment, independent of experience.

Overview of clinical status, treatment, and long-term outcomes of pediatric autosomal-dominant polycystic kidney disease: a nationwide survey in Taiwan.

This retrospective study investigated the incidence, medication use, and outcomes in pediatric autosomal-dominant polycystic kidney disease (ADPKD) using Taiwan's National Health Insurance Research Database (NHIRD). A 1:4 matched control group of individuals included in the NHIRD during the same period was used for comparative analyses. A total of 621 pediatric patients were identified from 2009 to 2019 (mean age, 9.51 ± 6.43 years), and ADPKD incidence ranged from 2.32 to 4.45 per 100,000 individuals (cumulative incidence, 1.26-1.57%). The incidence of newly developed hypertension, anti-hypertensive agent use, nephrolithiasis, and proteinuria were significantly higher in the ADPKD group than the non-ADPKD group (0.7 vs. 0.04, 2.26 vs. 0.30, 0.4 vs. 0.02, and 0.73 vs. 0.05 per 100 person-years, respectively). The adjusted hazard ratios for developing hypertension, proteinuria, nephrolithiasis and anti-hypertensive agent use in cases of newly-diagnosed pediatric ADPKD were 12.36 (95% CI 4.92-31.0), 13.49 (95% CI 5.23-34.79), 13.17 (95% CI 2.48-69.98), and 6.38 (95% CI 4.12-9.89), respectively. The incidence of congenital cardiac defects, hematuria, urinary tract infections, gastrointestinal diverticulosis, dyslipidemia, and hyperuricemia were also higher in the ADPKD group. Our study offers valuable insights into the epidemiology of pediatric ADPKD in Taiwan and could help in formulating guidelines for its appropriate management.

Disease-associated missense mutations in the pore loop of polycystin-2 alter its ion channel function in a heterologous expression system.

Polycystin-2 (PC2) is mutated in ∼15% of patients with autosomal dominant polycystic kidney disease (ADPKD). PC2 belongs to the family of transient receptor potential (TRP) channels and can function as a homotetramer. We investigated whether three disease-associated mutations (F629S, C632R, or R638C) localized in the channel's pore loop alter ion channel properties of human PC2 expressed in Xenopus laevis oocytes. Expression of wild-type (WT) PC2 typically resulted in small but measurable Na+ inward currents in the absence of extracellular divalent cations. These currents were no longer observed when individual pore mutations were introduced in WT PC2. Similarly, Na+ inward currents mediated by the F604P gain-of-function (GOF) PC2 construct (PC2 F604P) were abolished by each of the three pore mutations. In contrast, when the mutations were introduced in another GOF construct, PC2 L677A N681A, only C632R had a complete loss-of-function effect, whereas significant residual Na+ inward currents were observed with F629S (∼15%) and R638C (∼30%). Importantly, the R638C mutation also abolished the Ca2+ permeability of PC2 L677A N681A and altered its monovalent cation selectivity. To elucidate the molecular mechanisms by which the R638C mutation affects channel function, molecular dynamics (MD) simulations were used in combination with functional experiments and site-directed mutagenesis. Our findings suggest that R638C stabilizes ionic interactions between Na+ ions and the selectivity filter residue D643. This probably explains the reduced monovalent cation conductance of the mutant channel. In summary, our data support the concept that altered ion channel properties of PC2 contribute to the pathogenesis of ADPKD.

Unveiling Neglected Concerns: Possible Severe Hepatic Complications after Nephrectomy in Autosomal Dominant Polycystic Kidney Disease - A Case Report.

Introduction: Autosomal dominant polycystic kidney disease (ADPKD) is the most common genetic kidney disease and the 4th leading cause of renal replacement therapy in the world. ADPKD is a systemic disorder as cysts may develop in several organs. Liver cysts are the most common extrarenal manifestations and are often incidentally detected. Even though cysts do not influence liver function, they can grow to a very great size and can significantly enlarge liver volume, causing structural distortion of the biliary tree and patient discomfort due to the mass effect. Nephrectomy is frequently considered in preparation for renal transplantation in patients with remarkable kidneys' enlargement. There are currently no globally recognized clinical guidelines for nephrectomy. Although cysts do not normally affect liver function in ADPKD, after nephrectomy cases of liver fibrosis and Budd-Chiari have been reported. These are uncommon disorders due to the obstruction of the blood flow in the hepatic venous causing spleen and liver volume enlargement, portal hypertension, and hepatic cirrhosis. Case Presentation: We present a case of hepatic fibrosis with splenomegaly and severe pancytopenia as a tardive complication after bilateral nephrectomy in 47-year-old ADPKD patient. Conclusion: This finding underscores the critical significance of meticulously examining the anatomical relationship between polycystic kidneys and the liver before performing nephrectomy. Additionally, it highlights the importance of assessing liver involvement and associated complications. By integrating liver assessment into the criteria, we can significantly enhance patient care and improve the overall management of ADPKD before kidney transplantation.

The First Pediatric Case of an IFT140 Heterozygous Deletion Causing Autosomal Dominant Polycystic Kidney Disease: Case Report.

Introduction: Autosomal dominant polycystic kidney disease (ADPKD) is the most common hereditary kidney disease, which is mainly caused by pathogenic variants in two particular genes: PKD1 and PKD2. ADPKD caused by variants in other genes (GANAB or IFT140) is very rare. Case Report: In a 6-year-old girl examined for abdominal pain, a cystic mass in the upper part of the right kidney was detected during an abdominal ultrasound. She was referred to pediatric oncology and urology for suspicion of a tumorous mass and the condition was assessed as a cystic nephroma. A heminephrectomy was then performed on the upper cystic part of the right kidney. The histological examination was inconclusive; therefore, genetic testing was recommended. Kidney and liver cysts were detected sonographically in the mother, but DNA analysis of the PKD1 and PKD2 genes did not reveal any pathogenic variant; the cause of the pathological formation in the kidneys remained unclear. Nine years later, next-generation sequencing of a panel of genes for kidney disease was performed and a heterozygous deletion was found on chromosome 16; this included exon 13 of the IFT140 gene. The same deletion was found in the patient's mother. Currently, the patient is 14 years old and has mild sonographic findings, normal glomerular filtration, mild proteinuria, and hypertension. Conclusion: Pathogenic variants of the IFT140 gene very rarely cause ADPKD; however, they should be considered in all children with autosomal dominant forms of PKD and asymmetric/atypical cystic kidney involvement or negative findings of PKD1 and PKD2.

MicroRNA and renal fibrosis in autosomal dominant polycystic kidney disease: a longitudinal study.

BACKGROUND: Autosomal dominant polycystic kidney disease (ADPKD) is a hereditary kidney disorder that may progress to kidney failure, accounting for 5-10% of all patients with end-stage kidney disease (ESKD). Clinical data, as well as molecular genetics and advanced imaging techniques have provided surrogate prognostic biomarkers to predict rapid decline in kidney function, nonetheless enhanced tools for assessing prognosis for ADPKD are still needed. The aim of this study was to analyze specific microRNAs involved in the pathogenesis of ADPKD and in the development of renal fibrosis, evaluating their potential role as predictors of renal function loss. METHODS: We evaluated kidney function by estimated glomerular filtration rate (eGFR) in 32 ADPKD patients in different stages of kidney disease at T0 and after a 24-month follow up (T1). Patients were divided into two groups: Rapid disease progression ([RP], n 15) and Non-rapid disease progression ([NRP], n 17), according to the Mayo Clinic classification criteria. At T0, ADPKD patients underwent plasma sampling for quantitative analysis of h-miR-17-5p, h-miR-21-5p and h-miR-199a-5p microRNA expression, using the quantitative reverse transcriptase-polymerase chain reaction (qRT-PCR) method and a 3 T magnetic resonance imaging (MRI), using an advanced MRI imaging protocol, for the quantification of total kidney volume (TKV), total perfusion volume (TPV) and total fibrotic volume (TFV). RESULTS: The expression of h-miR17-5p was higher (p < 0.05) in ADPKD patients with rapid disease progression. h-miR-17-5p, h-miR-21-5p and h-mir-199-5p showed a positive and significant correlation with the eGFR slope (mL/min/1.73 m2/year) (p < 0.05) but not with the eGFR at both T0 and T1. Both total fibrotic volume (cm3) and height-adjusted total fibrotic volume (cm3/m) were positively and significantly correlated to h-miR 21-5p and h-miR 199-5p (p < 0.05), but not to total kidney volume (cm3) and height-adjusted total kidney volume (cm3/m). CONCLUSIONS: The microRNAs we studied were associated with fibrosis and renal damage, suggesting their possible role as biomarkers able to identify ADPKD patients at high risk of disease progression regardless of the degree of kidney function, and therefore suitable for medical therapy, and may help uncovering new molecular mechanisms underlying cystogenesis.

Decoupling shear stress and pressure effects in the biomechanics of autosomal dominant polycystic kidney disease using a perfused kidney-on-chip.

Kidney tubular cells are submitted to two distinct mechanical forces generated by the urine flow: shear stress and hydrostatic pressure. In addition, the mechanical properties of the surrounding extracellular matrix modulate tubule deformation under constraints. These mechanical factors likely play a role in the pathophysiology of kidney diseases as exemplified by autosomal dominant polycystic kidney disease, in which pressure, flow and matrix stiffness have been proposed to modulate the cystic dilation of tubules with PKD1 mutations. The lack of in vitro systems recapitulating the mechanical environment of kidney tubules impedes our ability to dissect the role of these mechanical factors. Here we describe a perfused kidney-on-chip with tunable extracellular matrix mechanical properties and hydrodynamic constraints, that allows a decoupling of shear stress and flow. We used this system to dissect how these mechanical cues affect Pkd1 -/- tubule dilation. Our results show two distinct mechanisms leading to tubular dilation. For PCT cells (proximal tubule), overproliferation mechanically leads to tubular dilation, regardless of the mechanical context. For mIMCD-3 cells (collecting duct), tube dilation is associated with a squamous cell morphology but not with overproliferation and is highly sensitive to extracellular matrix properties and hydrodynamic constraints. Surprisingly, flow alone suppressed Pkd1 -/- mIMCD-3 tubule dilation observed in static conditions, while the addition of luminal pressure restored it. Our in vitro model emulating nephron geometrical and mechanical organization sheds light on the roles of mechanical constraints in ADPKD and demonstrates the importance of controlling intraluminal pressure in kidney tubule models.

Acute Kidney Injury Due to Nephrolithiasis in Autosomal Dominant Polycystic Kidney Disease Treated With Tolvaptan: A Case Report.

A 61-year-old asymptomatic female with autosomal dominant polycystic kidney disease (ADPKD) on tolvaptan therapy was hospitalized for acute kidney injury (AKI). Nephrolithiasis had already been diagnosed; however, the patient had not undergone any interventions. She also presented with hyponatremia possibly caused by overhydration. Because the estimated glomerular filtration rate (eGFR) decline was significantly higher than the predicted rate, we considered a possible case of postrenal AKI and examined computed tomography (CT), which revealed left hydronephrosis with a 9.4-mm ureteric stone at the level of L3/L4. We restricted fluid intake, which resulted in an increase in sodium levels. She was treated with transurethral lithotripsy (TUL) twice, which successfully improved her kidney function. Although the serum sodium levels increase because of aquaresis in almost all patients treated with tolvaptan, our case was unique in that the patient presented with hyponatremia. We should pay more attention to the periodical follow-up of nephrolithiasis in addition to the increase in total kidney volume and decide the appropriate time to treat nephrolithiasis depending on the case. We should also keep in mind that ADPKD patients have a high frequency of nephrolithiasis and, even if asymptomatic, investigate urinary tract obstruction and hydronephrosis in case of AKI.

Variable Clinical Presentations and Renal Outcome in Neonates With Autosomal Recessive Polycystic Kidney Disease.

Autosomal recessive polycystic kidney disease (ARPKD) is caused by a mutation in the polycystic kidney and hepatic disease-1 (PKHD1) gene and is an important inherited cause of chronic kidney disease in children. The most typical presentations in neonates are massively enlarged kidneys with variable echogenicity, multiple small cysts, and congenital hepatic fibrosis. Potter sequence with pulmonary hypoplasia can present due to oligohydramnios. Severe pulmonary hypoplasia can lead to respiratory insufficiency and perinatal death. Some affected children can develop end-stage renal disease in early childhood or adolescence. Here, we report the clinical presentations, management, and renal outcomes of three neonatal cases of ARPKD from our center.

Update on the Application of Ultrasonography in Understanding Autosomal Dominant Polycystic Kidney Disease.

With an estimated prevalence of 1 in 1000 individuals globally, autosomal dominant polycystic kidney disease (ADPKD) stands as the most prevalent inherited renal disorder. Ultrasonography (US) is the most widely used imaging modality in the diagnosis and monitoring of ADPKD. This review discusses the role of US in the evaluation of ADPKD, including its diagnostic accuracy, limitations, and recent advances. An overview of the pathophysiology and clinical manifestations of ADPKD has also been provided. Furthermore, the potential of US as a noninvasive tool for the assessment of disease progression and treatment response is examined. Overall, US remains an essential tool for the management of ADPKD, and ongoing research efforts are aimed at improving its diagnostic and prognostic capabilities.

COVID-19 Infection in Autosomal Dominant Polycystic Kidney Disease and Chronic Kidney Disease Patients: Progression of Kidney Disease.

INTRODUCTION: the COVID-19 pandemic has brought to light the intricate interplay between viral infections and preexisting health conditions. In the field of kidney diseases, patients with Autosomal Dominant Polycystic Kidney Disease (ADPKD) and Chronic Kidney Disease (CKD) face unique challenges when exposed to the SARS-CoV-2 virus. This study aims to evaluate whether SARS-CoV-2 virus infection impacts renal function differently in patients suffering from ADPKD and CKD when compared to patients suffering only from CKD. MATERIALS AND METHODS: clinical data from 103 patients were collected and retrospectively analyzed. We compared the renal function of ADPKD and CKD patients at two distinct time points: before COVID-19 infection (T0) and 1 year after the infection (T1). We studied also a subpopulation of 37 patients with an estimated glomerular filtration rate (eGFR) < 60 mL/min and affected by ADPKD and CKD. RESULTS: clinical data were obtained from 59 (57.3%) ADPKD patients and 44 (42.7%) CKD patients. At T1, ADPKD patients had significantly higher serum creatinine levels compared to CKD patients, and a significantly lower eGFR was observed only in ADPKD patients with eGFR < 60 mL/min compared to CKD patients (p < 0.01, p < 0.05; respectively). Following COVID-19 infection, ADPKD-CKD patients exhibited significantly higher variation in both median serum creatinine (p < 0.001) and median eGFR (p < 0.001) compared to CKD patients. CONCLUSION: the interplay between COVID-19 and kidney disease is complex. In CKD patients, the relationship between COVID-19 and kidney disease progression is more established, while limited studies exist on the specific impact of COVID-19 on ADPKD patients. Current evidence does not suggest that ADPKD patients are at a higher risk of SARS-CoV-2 infection; however, in our study we showed a significant worsening of the renal function among ADPKD patients, particularly those with an eGFR < 60 mL/min, in comparison to patients with only CKD after a one-year follow-up from COVID-19 infection.

Computational drug discovery approaches identify mebendazole as a candidate treatment for autosomal dominant polycystic kidney disease.

Autosomal dominant polycystic kidney disease (ADPKD) is a rare genetic disorder characterised by numerous renal cysts, the progressive expansion of which can impact kidney function and lead eventually to renal failure. Tolvaptan is the only disease-modifying drug approved for the treatment of ADPKD, however its poor side effect and safety profile necessitates the need for the development of new therapeutics in this area. Using a combination of transcriptomic and machine learning computational drug discovery tools, we predicted that a number of existing drugs could have utility in the treatment of ADPKD, and subsequently validated several of these drug predictions in established models of disease. We determined that the anthelmintic mebendazole was a potent anti-cystic agent in human cellular and in vivo models of ADPKD, and is likely acting through the inhibition of microtubule polymerisation and protein kinase activity. These findings demonstrate the utility of combining computational approaches to identify and understand potential new treatments for traditionally underserved rare diseases.

Juxtaglomerular apparatus-mediated homeostatic mechanisms: therapeutic implication for chronic kidney disease.

INTRODUCTION: Juxtaglomerular apparatus (JGA)-mediated homeostatic mechanism links to how sodium-glucose cotransporter 2 inhibitors (SGLT2is) slow progression of chronic kidney disease (CKD) and may link to how tolvaptan slows renal function decline in autosomal dominant polycystic kidney disease (ADPKD). AREA COVERED: JGA-mediated homeostatic mechanism has been hypothesized based on investigations of tubuloglomerular feedback and renin-angiotensin system. We reviewed clinical trials of SGLT2is and tolvaptan to assess the relationship between this mechanism and these drugs. EXPERT OPINION: When sodium load to macula densa (MD) increases, MD increases adenosine production, constricting afferent arteriole (Af-art) and protecting glomeruli. Concurrently, MD signaling suppresses renin secretion, increases urinary sodium excretion, and counterbalances reduced sodium filtration. However, when there is marked increase in sodium load per-nephron, as in advanced CKD, MD adenosine production increases, relaxing Af-art and maintaining sodium homeostasis at the expense of glomeruli. The beneficial effects of tolvaptan on renal function in ADPKD may also depend on the JGA-mediated homeostatic mechanisms since tolvaptan inhibits sodium reabsorption in the thick ascending limb.The JGA-mediated homeostatic mechanism regulates Af-arts, constricting to relaxing according to homeostatic needs. Understanding this mechanism may contribute to the development of pharmacotherapeutic compounds and better care for patients with CKD.