New insights into targeting hepatic cystogenesis in autosomal dominant polycystic liver and kidney disease

GANAB c.1118C > T is a novel variant in patients with polycystic liver disease / polycystic kidney disease

BACKGROUND

Many patients suffer from genetically unsolved polycystic liver disease (PLD). Our aim was to explore mutated genes associated with the pathogenesis of PLD.

METHODS

First, a family investigation was conducted on probands with a definite diagnosis of PLD and the pedigree was confirmed. Data on the clinical symptoms and biochemical and imaging indicators of family members were collected. Mutation analysis was performed using whole exome sequencing (WES), and Sanger sequencing was used for mutation verification.

RESULTS

Nine of the 33 patients from five generations of the proband and their families were diagnosed with PLD/polycystic kidney disease (PKD). Imaging examination of all patients confirmed numerous hepatic and renal cysts. Patients clinically presented with different degrees of abdominal distension and impaired renal function. WES revealed a missense mutation in GANAB c.1118C > T (p. Thr373Ile) in the proband and her affected son, which resulted in a change from hydrophilic threonine to hydrophobic isoleucine at amino acid 373. The mutation was verified using Sanger sequencing.

CONCLUSION

This study identified a novel heterozygous mutation, c.1118C > T (p. Thr373Ile) in GANAB in patients with PLD/PKD. This mutation has not been reported to date and enriches the phenotype and genotype spectrum of GANAB-related diseases.

Abnormalities of IL-12 Family Cytokine Pathways in Autosomal Dominant Polycystic Kidney Disease Progression

Background and Objectives: Autosomal Dominant Polycystic Kidney Disease (ADPKD) is the most frequent genetic renal disease with a complex physiopathology. More and more studies sustain that inflammation plays a crucial role in ADPKD pathogenesis and progression. We evaluated IL-12 involvement in ADPKD pathophysiology by assessing the serum levels of its monomers and heterodimers. Materials and Methods: A prospective case-control study was developed and included 66 ADPKD subjects and a control group of 40 healthy subjects. The diagnosis of ADPKD was based on familial history clinical and imagistic exams. The study included subjects with eGFR > 60 mL/min/1.73 mp, with no history of hematuria or other renal disorders, with stable blood pressure in the last 6 months. We tested serum levels of monomers IL-12 p40 and IL-12 p35 and heterodimers IL-12 p70, IL-23, IL 35, assessed by ELISA method. Results: IL-12 family programming was abnormal in ADPKD patients. IL-12p70, IL-12p40, and IL-23 secretion increased, while IL-12p35 and IL-35 secretion decreased compared to control. IL-12p70, IL-12p40, and IL-23 had a progressive increase correlated with immune response amplification, a decrease of eGFR, an increase in TKV, and in albuminuria. On the other hand, IL-35 and IL-12p35 were correlated negatively with CRP and albuminuria and positively with eGFR in advanced ADPKD. Conclusions: The present study investigated IL-12 cytokine family members' involvement in ADPKD pathogenesis, enriching our understanding of inflammation in the most common renal genetic disorder.

Protocol for a randomized controlled multicenter trial assessing the efficacy of leuprorelin for severe polycystic liver disease: the AGAINST-PLD study

Background

In patients with severe polycystic liver disease (PLD), there is a need for new treatments. Estrogens and possibly other female sex hormones stimulate growth in PLD. In some patients, liver volume decreases after menopause. Female sex hormones could therefore be a target for therapy. The AGAINST-PLD study will examine the efficacy of the GnRH agonist leuprorelin, which blocks the production of estrogen and other sex hormones, to reduce liver growth in PLD.

Methods

The AGAINST-PLD study is an investigator-driven, multicenter, randomized controlled trial. Institutional review board (IRB) approval was received at the University Medical Center of Groningen and will be collected in other sites before opening these sites. Thirty-six female, pre-menopausal patients, with a very large liver volume for age (upper 10% of the PLD population) and ongoing liver growth despite current treatment options will be randomized to direct start of leuprorelin or to 18 months standard of care and delayed start of leuprorelin. Leuprorelin is given as 3.75 mg subcutaneously (s.c.) monthly for the first 3 months followed by 3-monthly depots of 11.25 mg s.c. The trial duration is 36 months. MRI scans to measure liver volume will be performed at screening, 6 months, 18 months, 24 months and 36 months. In addition, blood will be drawn, DEXA-scans will be performed and questionnaires will be collected. This design enables comparison between patients on study treatment and standard of care (first 18 months) and within patients before and during treatment (whole trial). Main outcome is annualized liver growth rate compared between standard of care and study treatment. Secondary outcomes are PLD disease severity, change in liver growth within individuals and (serious) adverse events. The study is designed as a prospective open-label study with blinded endpoint assessment (PROBE).

Discussion

In this trial, we combined the expertise of hepatologist, nephrologists and gynecologists to study the effect of leuprorelin on liver growth in PLD. In this way, we hope to stop liver growth, reduce symptoms and reduce the need for liver transplantation in severe PLD.

Trial registration Eudra CT number 2020-005949-16, registered at 15 Dec 2020. https://www.clinicaltrialsregister.eu/ctr-search/search?query=2020-005949-16.

Polycystic Liver Disease: Advances in Understanding and Treatment

Polycystic liver disease (PLD) is a group of genetic disorders characterized by progressive development of cholangiocyte-derived fluid-filled hepatic cysts. PLD is the most common manifestation of autosomal dominant and autosomal recessive polycystic kidney diseases and rarely occurs as autosomal dominant PLD. The mechanisms of PLD are a sequence of the primary (mutations in PLD-causative genes), secondary (initiation of cyst formation), and tertiary (progression of hepatic cystogenesis) interconnected molecular and cellular events in cholangiocytes. Nonsurgical, surgical, and limited pharmacological treatment options are currently available for clinical management of PLD. Substantial evidence suggests that pharmacological targeting of the signaling pathways and intracellular processes involved in the progression of hepatic cystogenesis is beneficial for PLD. Many of these targets have been evaluated in preclinical and clinical trials. In this review, we discuss the genetic, molecular, and cellular mechanisms of PLD and clinical and preclinical treatment strategies. Expected final online publication date for the Annual Review of Pathology: Mechanisms of Disease, Volume 17 is January 2022. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.

Autophagy-mediated reduction of miR-345 contributes to hepatic cystogenesis in polycystic liver disease

Background & Aims

Polycystic liver disease (PLD) is characterised by increased autophagy and reduced miRNA levels in cholangiocytes. Given that autophagy has been implicated in miRNA regulation, we tested the hypothesis that increased autophagy accounts for miRNA reduction in PLD cholangiocytes (PLDCs) and accelerated hepatic cystogenesis.

Methods

We assessed miRNA levels in cultured normal human cholangiocytes (NHCs), PLDCs, and isolated PLDC autophagosomes by miRNA-sequencing (miRNA-seq), and miRNA targets by mRNA-seq. Levels of miR-345 and miR-345-targeted proteins in livers of animals and humans with PLD, in NHCs and PLDCs, and in PLDCs transfected with pre-miR-345 were assessed by in situ hybridisation (ISH), quantitative PCR, western blotting, and fluorescence confocal microscopy. We also assessed cell proliferation and cyst growth in vitro, and hepatic cystogenesis in vivo.

Results

In total, 81% of miRNAs were decreased in PLDCs, with levels of 10 miRNAs reduced by more than 10 times; miR-345 was the most-reduced miRNA. In silico analysis and luciferase reporter assays showed that miR-345 targets included cell-cycle and cell-proliferation-related genes [i.e. cell division cycle 25A (CDC25A), cyclin-dependent kinase 6 (CDK6), E2F2, and proliferating cell nuclear antigen (PCNA)]; levels of 4 studied miR-345 targets were increased in PLDCs at both the mRNA and protein levels. Transfection of PLDCs with pre-miR-345 increased miR-345 and decreased the expression of miR-345-targeted proteins, cell proliferation, and cyst growth in vitro. MiR-345 accumulated in autophagosomes in PLDCs but not NHCs. Inhibition of autophagy increased miR-345 levels, decreased the expression of miR-345-targeted proteins, and reduced hepatic cystogenesis in vitro and in vivo.

Conclusion

Autophagy-mediated reduction of miR-345 in PLDCs (i.e. miRNAutophagy) accelerates hepatic cystogenesis. Inhibition of autophagy restores miR-345 levels, decreases cyst growth, and is beneficial for PLD.

Lay summary

Polycystic liver disease (PLD) is an incurable genetic disorder characterised by the progressive growth of hepatic cysts. We found that hepatic cystogenesis is increased when the levels of miR-345 in PLD cholangiocytes (PLDCs) are reduced by autophagy. Restoration of miR-345 in PLDCs via inhibition of autophagy decreases hepatic cystogenesis and thus, is beneficial for PLD.

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The miRNA profile is altered in PLD.

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MiR-345 is the most-reduced miRNA in PLDCs.

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The reduction of miR-345 increases PLDC proliferation and hepatic cystogenesis.

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MiR-345 in PLDCs is regulated by autophagy, termed ‘miRNAutophagy’.

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Restoration of miR-345 in PLDC is beneficial for PLD.

Estrogens in polycystic liver disease: A target for future therapies?

BACKGROUND AND AIMS

Patients suffering from polycystic liver disease (PLD) can develop large liver volumes, leading to physical and psychological complaints, reducing quality of life. There is an unmet need for new therapies in these patients. Estrogen seems to be a promising target for new therapies. In this review, we summarize the available experimental and epidemiological evidence to unravel the role of estrogens and other female hormones in PLD, to answer clinical questions and identify new targets for therapy.

METHODS

We identified all experimental and epidemiologial studies concerning estrogens or other female hormones and PLD, to answer pre-defined clinial questions.

RESULTS

Female sex is the most important risk factor for the presence and severity of disease; estrogen supplementation enhances liver growth and after menopause, liver growth decreases. Experimental studies show the presence of the estrogen receptors alfa and beta on cystic cholangiocytes, and increased in vitro growth after administration of estrogen.

CONCLUSIONS

Based on the available evidence, female PLD patients should be discouraged from taking estrogen-containing contraceptives or hormone replacement therapy. Since liver growth rates decline after menopause, treatment decisions should be based on measured liver growth in postmenopausal women. Finally, blockage of estrogen receptors or estrogen production is a promising target for new therapies.

Tamoxifen for the treatment of polycystic liver disease: A case report

RATIONALE

Polycystic liver disease is a rare disease characterized by the growth of numerous cysts in the liver. The liver function remains well preserved, but liver volumes can grow very large, and some patients ultimately need a liver transplantation. Other treatment options are limited and there is an unmet need for new therapeutic options.

PATIENT CONCERNS

We describe a 59-year-old patient with pain in the abdomen, especially when bending forward. Five years ago, she was diagnosed with breast cancer and as an incidental finding a couple of large liver cysts were diagnosed, explaining her abdominal pain.

DIAGNOSIS

Polycystic liver disease with several large liver cysts.

INTERVENTIONS

The patient was treated with tamoxifen, an estrogen receptor modulator, as treatment for her hormone receptor positive breast cancer. One of the liver cysts was aspirated.

OUTCOMES

In the 4.6 years after the start of tamoxifen treatment, 20 mg once daily, the volume of her liver cysts decreased remarkably. There was a reduction of combined cyst volume from 311 mL to 22 mL without percutaneous drainage.

LESSONS

Epidemiological as well as experimental evidence supports a pivotal role for estrogens as a driver for growth of polycystic livers. Estrogen antagonism has often been proposed as a therapeutic target, but supporting evidence is lacking in the literature. We hypothesize that the decrease in cyst size in this patient was caused by tamoxifen therapy, suggesting an in vivo antagonistic effect on cystic cholangiocytes. This is an important finding because tamoxifen could be a promising new treatment option for polycystic liver disease.

Metformin slows liver cyst formation and fibrosis in experimental model of polycystic liver disease

Polycystic liver disease (PLD) is a hereditary liver disease in which the number of cysts increases over time, causing various abdominal symptoms and poor quality of life. Although effective treatment for PLD has not been established, we recently reported that long-term exercise ameliorated liver cyst formation and fibrosis with the activation of AMP-activated protein kinase (AMPK) in polycystic kidney (PCK) rats, a PLD model. Therefore, the aim of this study was to investigate whether metformin, an indirect AMPK activator, was effective in PCK rats. PCK rats were randomly divided into a control (Con) group and a metformin-treated (Met) group. The Met group was treated orally with metformin in drinking water. After 12 wk, liver function, histology, and signaling cascades of PLD were examined in the groups. Metformin did not affect the body weight or liver weight, but it reduced liver cyst formation, cholangiocyte proliferation, and fibrosis around the cyst. Metformin increased the phosphorylation of AMPK and tuberous sclerosis complex 2 and decreased the phosphorylation of mammalian target of rapamycin, S6, and extracellular signal-regulated kinase and the expression of cystic fibrosis transmembrane conductance regulator, aquaporin I, transforming growth factor-β, and type 1 collagen without changes in apoptosis or collagen degradation factors in the liver. Metformin slows the development of cyst formation and fibrosis with the activation of AMPK and inhibition of signaling cascades responsible for cellular proliferation and fibrosis in the liver of PCK rats.NEW & NOTEWORTHY This study indicates that metformin, an indirect AMPK activator slows liver cyst formation and fibrosis in PLD rat model. Metformin attenuates excessive cell proliferation in the liver with the inactivation of mTOR and ERK pathways. Metformin also reduces the expression of proteins responsible for cystic fluid secretion and liver fibrosis. Metformin and AMPK activators may be potent drugs for polycystic liver disease.

Mechanism and application of metformin in kidney diseases: An update

Metformin is an oral antihyperglycemic drug widely used to treat type 2 diabetes mellitus (T2DM), acting via indirect activation of 5' Adenosine monophosphate-activated Protein Kinase (AMPK). Beyond the anti-diabetic effect, accumulative pieces of evidence have revealed that metformin also everts a beneficial effect in diverse kidney diseases. In various acute kidney diseases (AKI) animal models, metformin protects renal tubular cells from inflammation, apoptosis, reactive oxygen stress (ROS), endoplasmic reticulum (ER) stress, epithelial-mesenchymal transition (EMT) via AMPK activation. In diabetic kidney disease (DKD), metformin also alleviates podocyte loss, mesangial cells apoptosis, and tubular cells senescence through AMPK-mediated signaling pathways. Besides, metformin inhibits cystic fibrosis transmembrane conductance regulator (CFTR)-mediated fluids secretion and the mammalian target of rapamycin (mTOR)-involved cyst formation negatively regulated by AMPK in autosomal dominant polycystic kidney disease (APDKD). Furthermore, metformin also contributes to the alleviation of urolithiasis and renal cell carcinoma (RCC). As the common pathway for chronic kidney disease (CKD) progressing towards end-stage renal disease (ESRD), renal fibrosis is ameliorated by metformin, to a great extent dependent on AMPK activation. However, clinical data are not always consistent with preclinical data, some clinical investigations showed the unmeaningful even detrimental effect of metformin on T2DM patients with kidney diseases. Most importantly, metformin-associated lactic acidosis (MALA) is a vital issue restricting the application of metformin. Thus, we conclude the application of metformin in kidney diseases and uncover the underlying molecular mechanisms in this review.

Polycystic liver disease genes: Practical considerations for genetic testing

The development of a polycystic liver is a characteristic of the monogenic disorders: autosomal dominant polycystic kidney disease (ADPKD), autosomal recessive polycystic kidney disease (ARPKD), and autosomal dominant polycystic liver disease (ADPLD). Respectively two and one genes mainly cause ADPKD and ARPKD. In contrast, ADPLD is caused by at least six different genes which combined do not even explain the disease development in over half of the ADPLD population. Genetic testing is mainly performed to confirm the likelihood of developing PKD and if renal therapy is essential. However, pure ADPLD patients are frequently not genetically screened as knowledge about the genotype-phenotype correlation is currently limited. This paper will clarify the essence of genetic testing in ADPLD patients.