Hypertension and left ventricular hypertrophy in autosomal dominant polycystic kidney disease

Pleural Effusions on MRI in Autosomal Dominant Polycystic Kidney Disease

Autosomal dominant polycystic kidney disease (ADPKD) has cystic fluid accumulations in the kidneys, liver, pancreas, arachnoid spaces as well as non-cystic fluid accumulations including pericardial effusions, dural ectasia and free fluid in the male pelvis. Here, we investigate the possible association of ADPKD with pleural effusion. ADPKD subjects (n = 268) and age-gender matched controls without ADPKD (n = 268) undergoing body magnetic resonance imaging from mid-thorax down into the pelvis were independently evaluated for pleural effusion by 3 blinded expert observers. Subjects with conditions associated with pleural effusion were excluded from both populations. Clinical and laboratory data as well as kidney, liver and spleen volume, pleural fluid volume, free pelvic fluid and polycystic kidney disease genotype were evaluated. Pleural effusions were observed in 56 of 268 (21%) ADPKD subjects compared with 21 of 268 (8%) in controls (p < 0.0001). In a subpopulation controlling for renal function by matching estimated glomerular filtration rate (eGFR), 28 of 110 (25%) ADPKD subjects had pleural effusions compared to 5 of 110 (5%) controls (p < 0.001). Pleural effusions in ADPKD subjects were more prevalent in females (37/141; 26%) than males (19/127,15%; p = 0.02) and in males were weakly correlated with the presence of free pelvic fluid (r = 0.24, p = 0.02). ADPKD subjects with pleural effusions were younger (48 ± 14 years old vs. 43 ± 14 years old) and weighed less (77 vs. 70 kg; p ≤ 0.02) than those without pleural effusions. For ADPKD subjects with pleural effusions, the mean volume of fluid layering dependently in the posterior−inferior thorax was 19 mL and was not considered to be clinically significant. Pleural effusion is associated with ADPKD, but its role in the pathogenesis of ADPKD requires further evaluation.

Practical Issues in the Management of Polycystic Kidney Disease: Blood Pressure and Water Balance

Autosomal dominant polycystic kidney disease is the most common hereditary renal disease affecting more than 13 million people worldwide. Renal function deteriorates as the cysts in both kidneys increase in number and size, which eventually results in end-stage kidney failure. Until recently, conservative management for chronic kidney disease such as blood pressure control, low sodium diet, adequate water intake, and weight control were known for the only treatment of polycystic kidney disease. However, the introduction of disease-modifying drug has led to the new paradigm shift in the management of polycystic kidney disease. Tolvaptan, the vasopressin V2 receptor antagonist, has been introduced to the patients with large kidneys since it can inhibit cyclic adenosine monophosphate, attenuates cyst growth, and delays renal failure. This article reviews the two important practical issues in the management of polycystic kidney disease: blood pressure and water balance. Firstly, the article will review the pathogenesis of high blood pressure in polycystic kidney disease and will demonstrate the current up-to-date management plan for blood pressure control. Secondly, this article will explain the mechanism of Tolvaptan on the treatment of polycystic kidney disease and its possible adverse effect on water and sodium balance.

Epicardial Fat Thickness in Patients with Autosomal Dominant Polycystic Kidney Disease

INTRODUCTION

Autosomal dominant polycystic kidney disease (ADPKD) is associated with early organ damage such as left ventricular hypertrophy and higher cardiovascular risk when compared to essential hypertension (EH). Epicardial adipose tissue (EAT) is a new cardiovascular risk factor, but its role and correlation with left ventricular mass (LVM) in ADPKD is unknown.

AIMS

we sought to investigate whether EAT is higher and related to LVM indexed by body surface area (LVMi) in hypertensive patients with ADPKD compared to those with EH.

METHODS

We performed ultrasound measurement of EAT thickness, LVM, LVMi, and left atrium size (left atrial volume indexed for body surface, LAVI) in 41 consecutive hypertensive patients with ADPKD, compared to 89 EH patients.

RESULTS

EAT was significantly higher in the ADPKD group in comparison to EH subjects (9.2 ± 2.9 mm vs. 7.8 ± 1.6 mm, p < 0.001), and significantly correlated with LVM, LVMi, and LAVI in the ADPKD group (r = 0.56, p = 0.005; r = 0.424, p = 0.022; and r = 0.48, p = < 0.001, respectively). Comparing EAT against body mass index, systolic blood pressure, and age, we found that EAT was the strongest predictor of LVMi (β = 0.42, p = 0.007).

CONCLUSION

Our data showed that EAT was higher in ADPKD patients than in EH subjects and independently correlated with LVMi. EAT measurement can be a useful marker for the cardiovascular risk stratification in ADPKD.

Early atherosclerosis in normotensive patients with autosomal dominant polycystic kidney disease: the relation between epicardial adipose tissue thickness and carotid intima-media thickness

Epicardial adipose tissue thickness (EATT) is suggested as a novel marker of subclinical atherosclerosis. Despite increased carotid intima-media thickness (CIMT) in autosomal dominant polycystic kidney disease (ADPKD) patients, the extent of the relationship between CIMT and EATT is unknown. The main purpose of our study was to evaluate the relation between EATT and CIMT in normotensive ADPKD patients with well-preserved renal function. Fifty-five normotensive ADPKD patients with normal renal function and 50 healthy control subjects were included in the study. EATT and CIMT were measured by echocardiography in all subjects. Correlation between EATT and CIMT was evaluated in ADPKD patients, while multivariate linear regression analysis was performed to determine factors predicting EATT and CIMT. ADPKD patients had significantly higher levels CIMT [0.7 (0.4–1.2) vs. 0.5 (0.4–0.8) mm, p < 0.001] and EATT (6.8 ± 2.7 vs. 4.8 ± 1.2 mm, p < 0.001) as compared with control subjects. Significant positive correlation was found between EATT and CIMT (r = 0.58, p < 0.001). Higher CRP levels (OR 54.7, 95 % CI 37.44–72.01, p < 0.001) and having ADPKD (OR 10.2, 95 % CI 2.53–17.86, p = 0.01) were the only independent factors associated with a higher EATT. A higher age (OR 0.35, 95 % CI −0.02 to 0.71, p = 0.06) tended to be independently associated with a higher EATT. In conclusion, our findings suggest that EATT, being simply measured by echocardiography and correlated with CIMT, can be used to detect subclinical atherosclerosis in normotensive ADPKD patients.

Protective cardiorenal effects of spironolactone in a rodent model of polycystic kidney disease

Studies were performed to examine the contribution of aldosterone to the pathogenesis of cardiovascular and renal disease in a rodent model of genetic kidney disease. Spironolactone (20 mg/kg per day) was administered in water to mixed sex Lewis Polycystic Kidney (LPK) rats (n = 20) and control Lewis rats (n = 27) from 4 to 12 weeks of age. At 12 weeks of age, hypertension was reduced in female LPK rats; systolic blood pressure declined from 226.4 ± 26.8 mmHg in untreated rats and to 179.2 ± 3.2 mmHg in treated rats (P = 0.018). No similar effect on male or control rats was found. Water consumption and urine volume were significantly greater in LPK animals than in Lewis rats, and treatment reduced both variables by ~30% in LPK animals (P < 0.05). Proteinuria and the urinary protein-to-creatinine ratio were normalized in treated LPK relative to Lewis controls, and plasma creatinine levels were significantly reduced by treatment in LPK rats. Spironolactone did not alter kidney morphology in LPK rats (fibrosis or cyst size). Aortic vascular responses to noradrenaline and acetylcholine were sensitized and impaired in the LPK (P < 0.01). Aldosterone antagonism did not alter these responses or indicators of aortic structural remodelling. There was no treatment effect on left ventricular hypertrophy or elevated cardiac messenger RNA for β-myosin-heavy chain and brain natriuretic peptide in the LPK rats. However, perivascular fibrosis and messenger RNA for α-cardiac actin were normalized by spironolactone in LPK animals relative to Lewis controls. In conclusion, we have shown an important blood pressure independent effect whereby inhibition of aldosterone via spironolactone was able to retard both renal and cardiac disease progression in a rodent model of polycystic kidney disease.

Correlation between arterial stiffness and inflammatory markers in autosomal dominant polycystic kidney disease patients with preserved renal function

AIM

To evaluate the association between arterial stiffness and inflammatory markers including C-reactive protein (CRP), pentraxin 3 (PTX3) and neutrophil-to-lymphocyte ratio (NLR) in autosomal dominant polycystic kidney disease (ADPKD) patients with preserved renal function.

METHODS

A total of 52 ADPKD patients [mean (SD) age 38.2 (12.8) years, 69.2 % were females] with preserved renal function and 25 healthy volunteers [mean (SD) age 35.5 (6.5) years, 48.0 % were females] were included. Data on patient characteristics, blood biochemistry, inflammatory markers [PTX3 (pg/mL), CRP (mg/dL) and NLR] and arterial stiffness [large artery elasticity index (LAEI) (mL/mmHg × 10) and small artery elasticity index (SAEI) (mL/mmHg × 100)] were recorded in patient and control groups. Correlation between inflammatory markers and arterial stiffness parameters was analysed in patients.

RESULTS

Overall, 42.3 % of ADPKD patients were hypertensive and 44.4 % were receiving renin-angiotensin-aldosterone system (RAAS) blockade therapy. Median levels for PTX3 [442.0 (20.0-4140.0) pg/mL vs. 220.5 (14.7-393.0) pg/mL, p < 0.001] and SAEI [4.90 (1.60-11.80) mL/mmHg × 100 vs. 6.45 (2.80-15.70) mL/mmHg × 10, p = 0.013] were significantly higher in ADPKD patients than in controls. PTX3 and CRP were not correlated with arterial elasticity, while NLR was significantly correlated with LAEI negatively (Rho = -0.278, p = 0.042).

CONCLUSION

In conclusion, our findings revealed increased PTX3 levels and reduced SAEI in patients as compared with controls, while no correlation between inflammatory markers studied and the small artery elasticity.

Developments in the management of autosomal dominant polycystic kidney disease

Autosomal dominant polycystic kidney disease (ADPKD) is the most frequent life- threatening, hereditary disease. ADPKD is more common than sickle cell anemia, cystic fibrosis, muscular dystrophy, hemophilia, Down's syndrome, and Huntington's disease combined. ADPKD is a multisystemic disorder characterized by the progressive development of renal cysts and marked renal enlargement. Structural and functional renal deterioration occurs in ADPKD patients and is the fourth leading cause of end-stage renal disease (ESRD) in adults. Aside from the renal manifestations, extrarenal structural abnormalities, such as liver cysts, cardiovascular abnormalities, and intracranial aneurysms may lead to morbidity and mortality. Recent studies have identified prognostic factors for progressive renal impairment including gender, race, age, proteinuria, hematuria, hypertension and increased left ventricular mass index (LVMI). Early diagnosis and better understanding of the pathophysiology of the disease provides the opportunity to aggressivly treat hypertension with renin-angiotensin-aldosterone system inhibitors and thereby potentially reduce LVMI, prevent cardiovascular morbidity and mortality and slow progression of the renal disease.

Temporal relationship between renal cyst development, hypertension and cardiac hypertrophy in a new rat model of autosomal recessive polycystic kidney disease

BACKGROUND/METHODS

We have examined the hypothesis that cyst formation is key in the pathogenesis of cardiovascular disease in a Lewis polycystic kidney (LPK) model of autosomal-recessive polycystic kidney disease (ARPKD), by determining the relationship between cyst development and indices of renal function and cardiovascular disease.

RESULTS

In the LPK (n = 35), cysts appear at week 3 (1.1 +/- 0.1 mm) increasing to week 24 (2.8 +/- 2 mm). Immunostaining for nephron-specific segments indicate cysts develop predominantly from the collecting duct. Cyst formation preceded hypertension (160 +/- 22 vs. Lewis control 105 +/- 20 mm Hg systolic blood pressure (BP), n = 12) at week 6, elevated creatinine (109 +/- 63 vs. 59 +/- 6 micromol/l, n = 16) and cardiac mass (0.7 vs. 0.4% bodyweight, n = 15) at week 12, and left ventricular hypertrophy (2,898 +/- 207 vs. 1,808 +/- 192 mum, n = 14) at week 24 (all p < or = 0.05). Plasma-renin activity and angiotensin II were reduced in 10- to 12-week LPK (2.2 +/- 2.9 vs. Lewis 11.9 +/- 4.9 ng/ml/h, and 25.0 +/- 19.1 vs. 94.9 +/- 64.4 pg/ml, respectively, n = 26, p < or = 0.05). Ganglionic blockade (hexamethonium 3.3 mg/kg) significantly reduced mean BP in the LPK (52 vs. Lewis 4%, n = 9, p < or = 0.05).

CONCLUSION

Cyst formation is a key event in the genesis of hypertension while the sympathetic nervous system is important in the maintenance of hypertension in this model of ARPKD.

Autosomal Dominant Polycystic Kidney Disease: Time for a Change?

Diagnosis and treatment of autosomal dominant polycystic kidney disease (ADPKD) is rapidly changing. Cellular pathways that involve the polycystins are being mapped and involve the primary cilium, intracellular calcium and cAMP regulation, and the mammalian target of rapamycin (mTOR) pathway. With the use of new imaging approaches, earlier diagnosis of hepatic cystic disease is possible, and measurement of kidney and cystic growth as well as kidney blood flow is possible over relatively short periods. PKD gene type, gender, proteinuria, and the presence of hypertension relate to the rate of kidney growth in ADPKD. On the basis of risk factors for progression to ESRD and the pathogenic roles that intracellular cAMP and mTOR play in cystogenesis, novel therapies are now being tested, including maximal inhibition of the renin-angiotensin system, inhibition of renal intracellular cAMP using vasopressin V2 receptor antagonists, and somatostatin analogues, as well as inhibitors of mTOR. This review addresses the current understanding of the pathogenesis and the natural history of ADPKD; accuracy and reliability of diagnostic approaches in utero, childhood, and adulthood; the value of reliable magnetic resonance imaging to measure disease progression early in the course of ADPKD; and novel therapeutic approaches that are being evaluated in ADPKD.

Long-lasting arrest of murine polycystic kidney disease with CDK inhibitor roscovitine

Polycystic kidney diseases (PKDs) are primarily characterized by the growth of fluid-filled cysts in renal tubules leading to end-stage renal disease. Mutations in the PKD1 or PKD2 genes lead to autosomal dominant PKD (ADPKD), a slowly developing adult form. Autosomal recessive polycystic kidney disease results from mutations in the PKHD1 gene, affects newborn infants and progresses very rapidly. No effective treatment is currently available for PKD. A previously unrecognized site of subcellular localization was recently discovered for all proteins known to be disrupted in PKD: primary cilia. Because ciliary functions seem to be involved in cell cycle regulation, disruption of proteins associated with cilia or centrioles may directly affect the cell cycle and proliferation, resulting in cystic disease. We therefore reasoned that the dysregulated cell cycle may be the most proximal cause of cystogenesis, and that intervention targeted at this point could provide significant therapeutic benefit for PKD. Here we show that treatment with the cyclin-dependent kinase (CDK) inhibitor (R)-roscovitine does indeed yield effective arrest of cystic disease in jck and cpk mouse models of PKD. Continuous daily administration of the drug is not required to achieve efficacy; pulse treatment provides a robust, long-lasting effect, indicating potential clinical benefits for a lifelong therapy. Molecular studies of the mechanism of action reveal effective cell-cycle arrest, transcriptional inhibition and attenuation of apoptosis. We found that roscovitine is active against cysts originating from different parts of the nephron, a desirable feature for the treatment of ADPKD, in which cysts form in multiple nephron segments. Our results indicate that inhibition of CDK is a new and effective approach to the treatment of PKD.

Earlier Diagnosis of Autosomal Dominant Polycystic Kidney Disease: Importance of Family History and Implications for Cardiovascular and Renal Complications

BACKGROUND

Autosomal dominant polycystic kidney disease (ADPKD) is a common and serious cause of hereditary renal disease. The emerging possibilities to intervene early in the disease course elevate the importance of both accurate and early diagnosis of ADPKD. Family history analysis is a simple and inexpensive approach to identifying individuals at risk for ADPKD. We hypothesized that advances in knowledge of and potential interventions for ADPKD have led to increased use of family history screening.

METHODS

We distributed surveys to 1,527 subjects from our ADPKD research database to determine the extent to which examination of family history was used to diagnose ADPKD, by birth cohort.

RESULTS

Six hundred thirty-seven subjects with ADPKD (42%) completed and returned surveys. Family history analysis led to the initial ADPKD diagnosis in 49% of all subjects overall. In the birth-cohort analysis, ADPKD was more likely to have been diagnosed in individuals born between 1951 and 1974 because of family history (55% versus 38%; P < 0.0002) and patients were younger at diagnosis (27 versus 39 years; P < 0.0001) than individuals born before 1951.

CONCLUSION

In a large cohort of subjects with ADPKD, we found increased use of family history analysis as a tool for diagnosing ADPKD and earlier age of diagnosis in the more recent birth cohort. This trend may reflect increased overall awareness of ADPKD by physicians, as well as encouraging hypertension and proteinuria treatment outcome data that may depend on intervening early in the course of disease.