Effect of inhibition of converting enzyme on renal hemodynamics and sodium management in polycystic kidney disease

We compared the tubular transport of sodium and the erythrocyte sodium-lithium countertransport activity in hypertensive patients with autosomal dominant polycystic kidney disease (ADPKD) and in normotensive control subjects. In addition, we assessed the effects of inhibition of converting enzyme on renal hemodynamics and sodium excretion in hypertensive patients with ADPKD to provide information on mechanisms responsible for the increased renal vascular resistance and filtration fraction and the adjustment of the pressure-natriuresis relationship during saline expansion, observed in patients with ADPKD, hypertension, and preserved renal function. In comparison with normotensive control subjects, the hypertensive patients with ADPKD had lower renal plasma flows, higher renal vascular resistances and filtration fractions, and similar proximal and distal fractional reabsorptions of sodium. The administration of enalapril resulted in significant increases in the renal plasma flow and significant reductions in mean arterial pressure, renal vascular resistance, and filtration fraction, but the glomerular filtration rate remained unchanged. Despite the significant reduction in mean arterial pressure during inhibition of converting enzyme, the distal fractional reabsorption of sodium decreased while the total fractional excretion of sodium remained unchanged or increased slightly. No significant differences were detected between the normotensive control subjects and the hypertensive patients with ADPKD in erythrocyte sodium-lithium countertransport activity, plasma renin activity, plasma aldosterone concentration, or atrial natriuretic factor. These results suggest that the renal renin-angiotensin system plays a central role in the alterations in renal hemodynamics and sodium management associated with the development of hypertension in ADPKD.     

Molecular complexes formed with polycystins

Polycystins are a family of novel transmembrane proteins with at least six members already identified in humans. Defects in polycystins-1 and -2 are responsible for nearly all cases of autosomal-dominant polycystic kidney disease (ADPKD), a major cause of end-stage renal failure. With the progress made in elucidating the genetic basis of ADPKD, the challenges are to understand the functions of polycystins and to delineate the biochemical and cellular mechanisms of cyst development and progression. In this review, we summarize the recent advances in our knowledge of the functions of polycystins with emphasis on the molecular composition of polycystin protein complexes in the kidney.     

Autosomal dominant polycystic kidney disease: recent advances in pathogenesis and treatment

Autosomal dominant polycystic kidney disease (ADPKD) is a common genetic disorder affecting 1 in 1,000 people in the general population and accounts for up to 10% of all patients on renal replacement therapy. Numerous fluid-filled epithelial cysts arise from different nephron segments as spherical dilatations or small out-pouchings, enlarge progressively and eventually become disconnected from the rest of the renal tubule. The development of cysts is accompanied by destruction of the renal parenchyma, interstitial fibrosis, cellular infiltration and loss of functional nephrons. ADPKD is not only a kidney disease but also a systemic disorder associated with intracranial arterial aneurysms, cardiac valvular defects, colonic diverticulosis and cyst formation in other organs such as the liver, spleen and pancreas. The identification of PKD1 and PKD2 together with the drive to elucidate the functions of their encoded proteins, polycystin-1 (PC1) and polycystin-2 (PC2), has led to an explosion of clinical and scientific interest in this common disorder. The aim of this review is to highlight recent advances in our understanding of ADPKD pathogenesis which are leading to exciting new treatment strategies.     

彩色多普勒超声对多囊肾患者肾脏血流的研究

目的　为了探讨常染色体显性多囊肾病 (autosomal dominantpolycystic kidney disease,ADPKD)对患者肾脏血流的影响 ,采用彩色多普勒超声测定血管的平均峰值流速 (Vmax、 Vmin)、阻力指数 (RI) ,确定肾脏血流与肾功能的关系以及囊肿大小与肾脏血流的关系。方法　选取 4 2例 ADPKD患者 ,以 4 5例正常人作为对照组。彩色多普勒超声测定双侧肾动脉 ,囊肿周边叶间动脉的最大、最小峰值流速和阻力指数。常规测定受试者的血清肌酐、尿素氮以及肌酐清除率。结果　 (1)多囊肾病组 (包括肾功能正常和异常组 )肾动脉平均峰值流速低于正常对照组 ,两者相比有明显差异 (P<0 .0 1) ;(2 )肾功能正常的多囊肾病组 RI较正常对照组升高 ,且具有统计学意义 (P<0 .0 5 ) ;(3)肾功能异常的多囊肾病组 RI较正常对照组升高 ,两者相比有明显差异 (P<0 .0 1) ;(4) RI与患者的肾功能呈正相关。结论　彩色多普勒超声检测能提示 ADPKD患者的肾脏血流情况 ,较肾功能测定更为敏感 ,为临床评价肾血流状态及疾病的转归、疗效的判定提供了一种新方法。     

Cardiovascular manifestations of autosomal dominant polycystic kidney disease in young adults

PURPOSE: Autosomal Dominant Polycystic Kidney Disease (ADPKD) is the most common hereditary renal disorder. In addition to renal structure and function abnormalities, the cardiovascular changes (extra renal manifestations) are the frequent findings observed in these subjects. This pilot study describes the viscoelastic properties of the aorta, a predisposing factor for the genesis of hypertension and left ventricular hypertrophy in young adults diagnosed with ADPKD. METHODS: Twenty new patients with ADPKD, all the off springs of previously diagnosed patients with ADPKD were recruited to participate in the study. Each patient underwent the measurement of 24-hour creatinine clearance (Ccr), 24-hour Ambulatory Blood Pressure Monitoring (ABPM), and ultrasonographic determination of the aortic dimensions and left ventricular measurements by M-mode echocardiogram and 12-lead electrocardiogram (ECG) in the echo laboratory. RESULTS: The mean age of our ADPKD subjects was 29.9 +/- 6.5 yr. Five patients had impaired renal functions (Ccr < 1.48 ml/sec). Fourteen patients had hypertension and nine were considered Non-dippers on ABPM. The median value of LVMI and AOD was 84.9 g/m2 and 28.5 x 10(-3)/kPa respectively. Forty five percent of these subjects had non-dipping circadian pattern with smaller nocturnal BP reduction. No relationship between AOD, LVMI and 24-hr ABPM was observed; however, a positive trend towards Ccr and AOD was evident. CONCLUSION: The majority of our ADPKD subjects have an unfavourable cardiovascular risk profile: hypertension and a non-dipping circadian BP rhythm. Subjects with evidence of renal function impairment had reduced aortic distensibility, placing them at an increased risk for cardiovascular morbidity and mortality.     

Expression and cellular localisation of renal endothelin-1 and endothelin receptor subtypes in autosomal-dominant polycystic kidney disease

The major factors influencing the rate of progression of chronic renal disease in autosomal-dominant polycystic kidney disease (ADPKD) are unknown and there are currently no effective treatments for slowing the progression of chronic renal failure in ADPKD patients. As a first step in investigating the potential role of endothelin-1 (ET1) and its receptors (ETA and ETB) in the pathophysiology of progression in ADPKD, we have studied their expression and cellular localisation in ADPKD kidney. Immunoreactive ET1 was detected in cyst epithelia, mesangial cells and vascular smooth muscle cells suggesting continuing ET1 synthesis in the cystic kidney. Compared to healthy controls, ETA mRNA was 5-10-fold higher in ADPKD cystic kidney. In cystic kidney, neo-expression of ETA receptors was found overlying glomeruli and cysts and markedly increased in medium-sized renal arteries by microautoradiography. This is the first study to demonstrate a specific upregulation of ETA receptors in human renal disease. Future studies should address whether ETA selective antagonists may be effective in slowing renal disease progression in ADPKD.     

常染色体显性多囊肾病的预后评估及治疗

常染色体显性多囊肾病(autosomal dominant polycystic kidney disease, ADPKD)患病率为1‰~2‰, 属于罕见病, 临床主要表现为双侧肾囊肿且逐渐发展, 肾脏体积进行性增大, 肾功能逐步降低。PKD1基因突变约占81%, PKD2基因突变约占10.5%~22%。血管加压素(arginine vasopressin, AVP)和环磷酸腺苷(cyclic adenosine monophosphate, cAMP)信号通路在ADPKD囊肿发展过程中发挥重要作用。近年来发表的梅奥风险评估模型和PROPKD(predicting renal outcome in polycystic kidney disease)评分是ADPKD较好的预后评估模型, 已成为临床医生决策的重要依据。通过拮抗AVP受体, 抑制cAMP通路的托伐普坦已成为ADPKD首个特异治疗药物, 可有效抑制总肾脏体积的增长和保护肾功能。药物的长期安全性仍需进一步研究。     

Modifier effect of the Glu298Asp polymorphism of endothelial nitric oxide synthase gene in autosomal-dominant polycystic kidney disease

Autosomal-dominant polycystic kidney disease (ADPKD) is one of the most common monogenic diseases. It is characterized by a substantial variability in the severity of renal phenotype, primarily assessed by the age at end-stage renal disease (ESRD). The role of modifier genes has been shown in various hereditary diseases, including ADPKD. The gene coding for the endothelial nitric oxide synthase (NOS3) is considered to have a modifier effect on the severity of ADPKD, even if there are studies among different populations that have shown contradictory results. In this study, we investigated the influence of one of the most studied polymorphisms of the NOS3 gene, the Glu298Asp polymorphism, on the age at ESRD in ADPKD. We analyzed a total of 100 ADPKD unrelated patients and 107 healthy cohorts from the Greek population. ADPKD patients were classified into two subgroups: patients with early (rapid progressors) and late (slow progressors) age at ESRD. The results suggested that the Glu298Asp polymorphism of NOS3 gene is associated with the onset age of ESRD. The distribution of C/T alleIes is significantly different between rapid and slow ADPKD progressors leading to the conclusion that the T allele of the Glu298Asp polymorphism of NOS3 gene is associated with earlier progression to ESRD in ADPKD patients.     

Identification and localization of polycystin,the PKD1 gene product.

Polycystin, the product of autosomal dominant polycystic kidney disease (ADPKD) 1 gene (PKD1) is the cardinal member of a novel class of proteins. As a first step towards elucidating the function of polycystin and the pathogenesis of ADPKD, three types of information were collected in the current study: the subcellular localization of polycystin, the spatial and temporal distribution of the protein within normal tissues and the effects of ADPKD mutations on the pattern of expression in affected tissues. Antisera directed against a synthetic peptide and two recombinant proteins of different domains of polycystin revealed the presence of an approximately 400-kD protein (polycystin) in the membrane fractions of normal fetal, adult, and ADPKD kidneys. Immunohistological studies localized polycystin to renal tubular epithelia, hepatic bile ductules, and pancreatic ducts, all sites of cystic changes in ADPKD, as well as in tissues such as skin that are not known to be affected in ADPKD. By electron microscopy, polycystin was predominantly associated with plasma membranes. Polycystin was significantly less abundant in adult than in fetal epithelia. In contrast, polycystin was overexpressed in most, but not all, cysts in ADPKD kidneys.     

Effect of statin therapy on disease progression in pediatric ADPKD: design and baseline characteristics of participants

Autosomal dominant polycystic kidney disease (ADPKD) is the most common genetic kidney condition and is associated with important renal and cardiovascular manifestations in childhood. Renal cystic disease can be documented in some cases as early as in utero. Early intervention is critical if the long-term complications of this condition, including end-stage renal disease, are to be ameliorated. Here we describe our ongoing randomized double-blind placebo-controlled phase III clinical trial to assess the effect of pravastatin treatment on renal and cardiovascular disease progression in 107 children and young adults age 8-22 years with ADPKD who are receiving the angiotensin converting enzyme inhibitor lisinopril. Baseline demographic and laboratory data are provided. Results of this study could markedly impact the standard of care for evaluation and treatment of ADPKD in this population.     

Abdominal sonographic study of autosomal dominant polycystic kidney disease

PURPOSE: The purpose of this study was to determine whether kidney size in patients who have autosomal dominant polycystic kidney disease (ADPKD) is related to renal function, hypertension, or extrarenal manifestations of the disease and to sonographically evaluate the abdominal manifestations of ADPKD. METHODS: Between 1994 and 1998, 400 individuals from 85 families with a history of ADPKD were examined. There were 213 persons with ADPKD and 187 unaffected family members; there were 182 males and 218 females, 1-82 years old (mean, 39.3 years). We obtained a complete medical history, performed a physical examination, measured the arterial blood pressure and serum creatinine levels, and performed abdominal sonography on each subject. The sonographic features that were studied were renal length and the presence and number of cysts on the kidneys, liver, and pancreas. RESULTS: There was a relationship between kidney size and age (p < 0.05), kidney size and renal function (p < 0.001), and kidney size and hypertension (p < 0.001). The overall prevalence of hepatic cysts in patients with ADPKD was 67%, and the prevalence increased with age. The presence of hepatic cysts was related to the severity of renal disease. Females had more severe polycystic liver disease, and massive polycystic liver disease (ie, hepatomegaly with innumerable cysts) was seen only in females. The prevalence of pancreatic cysts in the 187 persons in whom the pancreas was well evaluated sonographically was 5%. CONCLUSIONS: Kidney size in patients with ADPKD is related to renal function, hypertension, and extrarenal involvement and can be used to predict the outcome of the disease. Hepatic cysts are very common in patients with ADPKD and are related to age and renal function; pancreatic cysts are infrequent in these patients.     

Macrophage migration inhibitory factor promotes cyst growth in polycystic kidney disease

Autosomal dominant polycystic kidney disease (ADPKD) is characterized by renal cyst formation, inflammation, and fibrosis. Macrophages infiltrate cystic kidneys, but the role of these and other inflammatory factors in disease progression are poorly understood. Here, we identified macrophage migration inhibitory factor (MIF) as an important regulator of cyst growth in ADPKD. MIF was upregulated in cyst-lining epithelial cells in polycystin-1–deficient murine kidneys and accumulated in cyst fluid of human ADPKD kidneys. MIF promoted cystic epithelial cell proliferation by activating ERK, mTOR, and Rb/E2F pathways and by increasing glucose uptake and ATP production, which inhibited AMP-activated protein kinase signaling. MIF also regulated cystic renal epithelial cell apoptosis through p53-dependent signaling. In polycystin-1–deficient mice, MIF was required for recruitment and retention of renal macrophages, which promoted cyst expansion, and Mif deletion or pharmacologic inhibition delayed cyst growth in multiple murine ADPKD models. MIF-dependent macrophage recruitment was associated with upregulation of monocyte chemotactic protein 1 (MCP-1) and inflammatory cytokine TNF-α. TNF-α induced MIF expression, and MIF subsequently exacerbated TNF-α expression in renal epithelial cells, suggesting a positive feedback loop between TNF-α and MIF during cyst development. Our study indicates MIF is a central and upstream regulator of ADPKD pathogenesis and provides a rationale for further exploration of MIF as a therapeutic target for ADPKD.     

Practical genetics for autosomal dominant polycystic kidney disease

Autosomal dominant polycystic kidney disease (ADPKD) is the most common mendelian disorder of the kidney and accounts for ~5% of end-stage renal disease in North America. It is characterized by focal development of renal cysts which increase in number and size with age. Mutations of PKD1 and PKD2 account for most cases. Although the clinical manifestations of both gene types overlap completely, PKD1 is associated with more severe disease than PKD2, with larger kidneys and earlier onset of end-stage renal disease. Furthermore, marked within-family renal disease variability is well documented in ADPKD and suggests a strong modifier effect from as yet unknown genetic and environmental factors. In turn, the significant inter- and intra-familial renal disease variability poses a challenge for diagnosis and genetic counseling. In general, renal ultrasonography is commonly used for the diagnosis, and age-dependent criteria have been defined for subjects at risk of PKD1. However, the utility of the PKD1 ultrasound criteria in the clinical setting is unclear since their performance characteristics have not been defined for the milder PKD2 and the gene type for most test subjects is unknown. Recently, highly predictive ultrasound diagnostic criteria have been derived for at-risk subjects of unknown gene type. Additionally, both DNA linkage and gene-based direct sequencing are available for the diagnosis of ADPKD, especially in subjects with equivocal imaging results, a negative or indeterminate family history, or in younger at-risk individuals being evaluated as potential living related kidney donor. This review will highlight the utility and limitations of clinical predictors of gene types, imaging- and molecular-based diagnostic tests, and present an integrated approach for evaluating individuals suspected to have ADPKD.     

Hepatic cysts in autosomal dominant polycystic kidney disease

Hepatic cysts are one of several extrarenal manifestations of the ADPKD gene. Several factors, including age, gender, pregnancy, the degree of renal cystic disease, and the extent of renal functional impairment, may modify the expression of hepatic cystic disease. With advances in medical care, such as improvement in the management of end-stage renal disease, hemodialysis, and renal transplantation, patients with ADPKD will experience an increased life expectancy. As a result, complications associated with hepatic cysts may become more common, and physicians may encounter an increasing number of patients with ADPKD who have infected hepatic cysts. Several issues in the management of this complication remain unresolved, but the article by Telenti and associates in this issue of the Proceedings addresses some of the critical issues that physicians who are responsible for the care of these patients will certainly confront in future years.     

Pkd1 regulates immortalized proliferation of renal tubular epithelial cells through p53 induction and JNK activation

Autosomal dominant polycystic kidney disease (ADPKD) is the most common human monogenic genetic disorder and is characterized by progressive bilateral renal cysts and the development of renal insufficiency. The cystogenesis of ADPKD is believed to be a monoclonal proliferation of PKD-deficient (PKD(-/-)) renal tubular epithelial cells. To define the function of Pkd1, we generated chimeric mice by aggregation of Pkd1(-/-) ES cells and Pkd1(+/+) morulae from ROSA26 mice. As occurs in humans with ADPKD, these mice developed cysts in the kidney, liver, and pancreas. Surprisingly, the cyst epithelia of the kidney were composed of both Pkd1(-/-) and Pkd1(+/+) renal tubular epithelial cells in the early stages of cystogenesis. Pkd1(-/-) cyst epithelial cells changed in shape from cuboidal to flat and replaced Pkd1(+/+) cyst epithelial cells lost by JNK-mediated apoptosis in intermediate stages. In late-stage cysts, Pkd1(-/-) cells continued immortalized proliferation with downregulation of p53. These results provide a novel understanding of the cystogenesis of ADPKD patients. Furthermore, immortalized proliferation without induction of p53 was frequently observed in 3T3-type culture of mouse embryonic fibroblasts from Pkd1(-/-) mice. Thus, Pkd1 plays a role in preventing immortalized proliferation of renal tubular epithelial cells through the induction of p53 and activation of JNK.     

Autosomic dominant polycystic kidney disease and metformin: Old knowledge and new insights on retarding progression of chronic kidney disease

Autosomal dominant polycystic kidney disease (ADPKD) is the most common congenital kidney disorder, generally caused by mutations in the PKD1 and PKD2 genes, coding for polycystins 1 and 2. Its pathogenesis is accompanied by alterations of the cAMP, mTOR, MAPK/ERK, and JAK/STAT pathways. ADPKD is clinically characterized by the formation of many growing cysts with kidney enlargement and a progressive damage to the parenchyma, up to its complete loss of function, and the onset of end-stage renal disease (ESRD). The current aim of ADPKD therapy is the inhibition of cyst development and retardation of chronic kidney disease progression. Several drugs have been recently included as potential therapies for ADPKD including metformin, the drug of choice for the treatment of type 2 diabetes mellitus, according to its potential inhibitory effects on cystogenesis. In this review, we summarize preclinical and clinical evidence endorsing or rejecting metformin administration in ADPKD evolution and pathological mechanisms. We explored the biology of APDKD and the role of metformin in slowing down cystogenesis searching PubMed and Clinical Trials to identify relevant data from the database inception to December 2020. From our research analysis, evidence for metformin as emerging cure for ADPKD mainly arise from preclinical studies. In fact, clinical studies are still scanty and stronger evidence is awaited. Its effects are likely mediated by inhibition of the ERK pathway and increase of AMPK levels, which are both linked to ADPKD pathogenesis.     

CT与SPECT在常染色体显性多囊肾治疗中的应用

目的 探讨CT与SPECT在常染色体显性多囊肾(ADPKD)治疗中的作用.方法 回顾性分析89例ADPKD患者的病历资料,观察各期患者术前CT表现特点及术前、术后SPECT肾动态显像的变化.结果 患者术前CT显示双肾体积增大,肾实质内多发大小不等的囊性低密度影,增强扫描后肾盂与囊肿对比明显.SPECT肾动态显像结果显示Ⅰ、Ⅱ、Ⅲ期患者术前肾小球滤过率(GFR)分别为(49.47±9.93)ml/min、(30.59±8.16)ml/min、(14.84±6.22)ml/min,术后分别为(52.14±8.67)ml/min、(43.77±9.33)ml/min、(14.65±5.61)ml/min.Ⅱ期患者术后GFR显著高于术前(P<0.05),Ⅰ、Ⅲ期患者术后GFR与术前相比,差异无统计学意义(P>0.05).结论 联合应用CT及SPECT有利于掌握肾脏形态及功能的综合信息,选择最佳手术时机及合理治疗方案.     

Prenatal sonographic patterns in autosomal dominant polycystic kidney disease: a multicenter study.

OBJECTIVE: To determine whether a specific prenatal sonographic pattern can be identified for autosomal dominant polycystic kidney disease (ADPKD) and if so whether it would be helpful in orienting complementary analysis, properly counseling parents and adapting pregnancy management. METHODS: A retrospective multicenter study was conducted in four prenatal diagnostic centers. The records of fetuses with a prenatal ultrasound examination revealing abnormal kidneys and with a final diagnosis of ADPKD were analyzed. Ultrasound analysis included: amount of amniotic fluid, bladder size, renal length, presence or absence of renal cysts and size of renal pelves, and was focused on parenchyma echogenicity and status of corticomedullary differentiation. Postnatal follow-up was reviewed. RESULTS: Of the 27 patients included in the study, 25 had hyperechogenic renal cortex and 20 had hypoechogenic medulla resulting in increased corticomedullary differentiation (CMD). In six cases, the medulla was hyperechogenic leading to absent or decreased CMD. One patient had normal cortical echogenicity and CMD. Renal cysts were present during the prenatal period in four patients (at 22 weeks in one case and after 30 weeks in three cases). In 12 patients, the cysts appeared after birth (within the first 6 months of postnatal life in 10 cases and by the age of 1 year in two cases). Elevated blood pressure was observed in only two cases and moderate chronic renal failure in one case. CONCLUSION: We have described the sonographic presentation in fetuses with ADPKD: moderately enlarged hyperechogenic kidneys with increased CMD. Although not specific to ADPKD, these findings should prompt familial screening. Other prenatal sonographic features (absent or decreased CMD and cortical cysts) are less frequent.     

Molecular genetics of autosomal dominant polycystic kidney disease

Autosomal dominant polycystic kidney disease (ADPKD) is a common Mendelian disorder, occurring in approximately 1 in 1000 births and accounting for 8% to 10% of cases of end-stage renal disease (ESRD). Mutations of 2 genes, PKD1 and PKD2, account for the disease in approximately 80% to 85% and 10% to 15% of families respectively. The gene products (polycystin 1 and 2) of PKD1 and PKD2 are plasma membrane proteins and components of a novel signalling pathway that regulates epithelial cell growth and differentiation. Significant inter- and intrafamilial renal disease variability in ADPKD has been well documented and is influenced by both germline and somatic genetic events. Specifically, genetic locus heterogeneity and 2 rare Mendelian syndromes have been shown to strongly influence the variability of interfamilial renal disease, and as-yet-unknown genetic and environmental factors likely modify both inter- and intrafamilial renal disease severity. Furthermore, individual cyst formation in ADPKD represents an aberration of monoclonal growth triggered by somatic PKD1 or PKD2 mutations within individual epithelial cells. Current studies are in progress to identify major genetic and environmental modifiers of renal disease variability. A thorough knowledge of these determinants will allow better patient risk assessment and development of mechanism-based therapy in ADPKD.