Liver involvement in cystic fibrosis: primary organ damage or innocent bystander?

Cystic fibrosis hepatobiliary involvement: an update on imaging in diagnosis and monitoring

Analysis of the liver using imaging for persons with cystic fibrosis (CF) continues to evolve as new medical therapies are developed improving and extending life. In the 2010s, therapies targeted at modulating protein folding became available to those with CF. Therapeutic options have continued to expand, now providing both correction of protein folding and stabilization for most gene mutations that code for the CF transmembrane receptor protein (CFTR). Today, approximately 80% of persons with CF are eligible for highly effective modulator therapy. With these advancements, the impact of CF on the liver has become more complex, adding metabolism of CFTR modulators to intrinsic CF hepatobiliary involvement (CFHBI) and adding not previously appreciated vascular changes within the liver due to increased longevity in persons with CF. A combination of serum biomarkers and imaging is needed to add clarity to the diagnosis and monitoring of the severity of liver disease. A substantial portion of persons with CF will develop at least CFHBI and a subset will develop advanced cystic fibrosis-associated liver disease (aCFLD); therefore, diagnosis and monitoring need to begin in childhood. In this review, we cover the use of and need for imaging, including elastography, ultrasound, and magnetic resonance imaging (MRI), in diagnosing and monitoring CFHBI and its associated complications.

Management of liver disease and portal hypertension in cystic fibrosis: a review

INTRODUCTION

Cystic fibrosis (CF)-associated liver disease can significantly affect the quality of life and survival of people with CF. The hepatobiliary manifestations in CF are various, with focal/multilobular biliary cirrhosis more common in children and porto-sinusoidal vascular disease (PSVD) in young adults. Portal hypertensive complications, particularly bleeding from esophagogastric varices and hypersplenism are common, while liver failure is rarer and mainly linked to biliary disease.

AREAS COVERED

This review explores current therapeutic options for CF-associated liver disease, presenting ongoing studies and new insights into parthenogenesis for potential future therapies.

EXPERT OPINION

Monitoring for signs of portal hypertension is essential. Limited evidence supports ursodeoxycholic acid (UDCA) efficacy in halting CF liver disease progression. The effect of cystic fibrosis transmembrane conductance regulator (CFTR) modulators on liver outcomes lacks definitive data, since patients with CF-related liver disease were excluded from trials due to potential hepatotoxicity. A proposed approach involves using UDCA and modulators in early stages, along with anti-inflammatory agents, with further therapeutic strategies awaiting randomized trials. Prevention of portal hypertensive bleeding includes endoscopic sclerotherapy or ligation of esophageal varices. Nonselective beta-blockers may also prevent bleeding and could be cautiously implemented. Other non-etiological treatments require investigation.

Cystic Fibrosis in an Adolescent: A "Miranda Warning" Against Blaming TB-A Case-Based Scholarly Update

Cystic fibrosis (CF) is a multisystem disorder that occurs as a result of autosomal recessive congenital transmission of CF transmembrane conductance regulator (CFTR) gene mutation on chromosome 7. Because it is considered a disease of the Caucasian pediatric population or due to lack of awareness, it is rarely considered in developing countries like ours. This case report presents the first case of cystic fibrosis ever reported in Ethiopia and possibly East Africa, that of a 17-year-old female diagnosed with the disease following a CT scan of her abdomen and chest. She was initially misdiagnosed and treated for tuberculosis (TB) as she was a chronic cougher. Perhaps due to epidemiological evidence, there is an obstinate tendency of blaming tuberculosis (TB) for almost every case of chronic cough with fibro-bronchiectatic lung parenchymal changes in Ethiopia. Once a diagnosis of TB is posted on such patients, their diagnosis remains in the circle of TB reinfection, relapse or resistance, followed by multiple phases of anti-mycobacterial drugs. This could lead to hazardous implications, including unnecessary prolonged anti-mycobacterial treatments, possibility of developing drug resistance, and mismanagement-related patient morbidity. This patient's chest and abdominal CT findings, including bronchiectasis, hepatic steatosis, pancreatic lipomatosis, micro-gallbladder and proximal colonic wall thickening, led to the diagnosis of CF. This article, presenting the first documented case of CF in the region, is meant to be a helpful reminder for clinicians and radiologists to also consider presumably "rare" illnesses like CF rather than blaming TB for every chronic cough and highlights the importance of abdominal CT features in the diagnosis of CF.

Abdominal ultrasound findings in adult patients with cystic fibrosis

INTRODUCTION AND AIMS

Cystic fibrosis (CF) is a genetic disease whose gastrointestinal compromise mainly involves the pancreas, bile ducts, and liver. Our aim was to analyze abdominal ultrasound findings.

METHODS

A retrospective, descriptive study was conducted on adults (patients ≥ 16 years of age) diagnosed with CF, within the time frame of 2006-2019. Clinical and genetic parameters, body mass index, forced expiratory volume in one second, pancreatic insufficiency, CF-related diabetes, cirrhosis secondary to CF, and abdominal ultrasound images were analyzed.

RESULTS

Seventy patients, 39 of whom were men (55.8%), had a mean age of 27 years and a mean body mass index of 21.3 ± 2.8 kg/m2 (r: 17-30.9). Forty-seven (67.1%) presented with pancreatic insufficiency, 6 (8.5%) with cirrhosis secondary to CF, and 21 (30%) had CF-related diabetes. Median forced expiratory volume in one second was 47% and the F508del mutation was found in 56.1%. Images of the pancreas: no pathologic findings in 49 (70%), increased echogenicity in 18 (25.7%), and cysts in 3 (4.3%). Gallbladder images: microgallbladder in 3 (4.2%), biliary sludge in 2 (2.8%), gallstones in 7 (10%), and a history of cholecystectomy in 4 (5.8%). Liver and spleen images: no pathologic findings in 47 (67.2%), homogeneous hepatomegaly with splenomegaly in 2 (2.8%), a heterogeneous pattern of the parenchyma in 11 (15.8%), increased echogenicity in 4 (5.7%), and heterogeneous echo patterns, lobulated liver contour, and splenomegaly in 6 (8.5%).

CONCLUSION

Abdominal ultrasound is a safe, low-cost technique that enables the identification of some degree of chronic liver and pancreatic diseases, improving the approach and follow-up decisions in adult patients with CF.

A Gastroenterologist's Guide to Care Transitions in Cystic Fibrosis from Pediatrics to Adult Care

Cystic Fibrosis is a chronic disease affecting multiple systems, including the GI tract. Clinical manifestation in patients can start as early as infancy and vary across different age groups. With the advent of new, highly effective modulators, the life expectancy of PwCF has improved significantly. Various GI aspects of CF care, such as nutrition, are linked to an overall improvement in morbidity, lung function and the quality of life of PwCF. The variable clinical presentations and management of GI diseases in pediatrics and adults with CF should be recognized. Therefore, it is necessary to ensure efficient transfer of information between pediatric and adult providers for proper continuity of management and coordination of care at the time of transition. The transition of care is a challenging process for both patients and providers and currently there are no specific tools for GI providers to help ensure a smooth transition. In this review, we aim to highlight the crucial features of GI care at the time of transition and provide a checklist that can assist in ensuring an effective transition and ease the challenges associated with it.

Transmembrane channel activity in human hepatocytes and cholangiocytes derived from induced pluripotent stem cells

The initial creation of human-induced pluripotent stem cells (iPSCs) set the foundation for the future of regenerative medicine. Human iPSCs can be differentiated into a variety of cell types in order to study normal and pathological molecular mechanisms. Currently, there are well-defined protocols for the differentiation, characterization, and establishment of functionality in human iPSC-derived hepatocytes (iHep) and iPSC-derived cholangiocytes (iCho). Electrophysiological study on chloride ion efflux channel activity in iHep and iCho cells has not been previously reported. We generated iHep and iCho cells and characterized them based on hepatocyte-specific and cholangiocyte-specific markers. The relevant transmembrane channels were selected: cystic fibrosis transmembrane conductance regulator, leucine rich repeat-containing 8 subunit A, and transmembrane member 16 subunit A. To measure the activity in these channels, we used whole-cell patch-clamp techniques with a standard intracellular and extracellular solution. Our iHep and iCho cells demonstrated definitive activity in the selected transmembrane channels, and this approach may become an important tool for investigating human liver biology of cholestatic diseases.

[Abdominal manifestations in cystic fibrosis : Clinical review]

Cystic fibrosis (CF) is the most common fatal autosomal recessive disease in the Caucasian population. A mutation in the cystic fibrosis transmembrane regulator protein (CFTR) gene leads to the production of abnormally viscous mucus and secretions in the lungs of these patients. A similar pathology also occurs in other organs. In the abdomen, among others the gastrointestinal tract, the pancreas, and the hepatobiliary system are affected. The involvement of the pancreas leads to its exocrine and endocrine insufficiency. Hepatic manifestations include hepatic steatosis, focal biliary and multilobular cirrhosis, and portal hypertension. Biliary complications include cholelithiasis, microgallbladder, and sclerosing cholangitis. In the gastrointestinal tract, complications such as the distal intestinal obstruction syndrome, invaginations, chronic constipation, wall thickening, and fibrosis in the colon may occur. An important renal manifestation is nephrolithiasis. With currently rapidly increasing life expectancy of patients with cystic fibrosis, complications of extrapulmonary cystic fibrosis manifestations including hepatic and gastrointestinal malignancy could be an increasing cause of morbidity and mortality of these patients. It is therefore important for radiologists to know and recognize these clinical patterns and to monitor these manifestations in follow-up exams. Previous therapy of extrapulmonary manifestations has been largely symptomatic. Fortunately, the new CFTR modulators seem to represent an effective causal therapeutic approach here.

PREVALENCE OF HEPATIC STEATOSIS AMONG CHILDREN AND ADOLESCENTS WITH CYSTIC FIBROSIS AND ITS ASSOCIATION WITH NUTRITIONAL STATUS

ABSTRACT Objective: To determine the prevalence of hepatic steatosis (HS) in children and adolescents with cystic fibrosis (CF) and associate it with nutritional status. Methods: Cross-sectional study with children and adolescents with CF diagnosis. Weight and height were used to calculate the body mass index (BMI) and subsequent classification of the nutritional status. The midarm circumference (MAC), triceps skinfold thickness (TSF) and midarm muscle circumference (MAMC) were used to evaluate body composition. Abdominal ultrasonography was performed for diagnosis of HS. The statistical tests used were Student’s t test, Mann-Whitney test and chi-square test with significance level of 5%. Results: 50 patients with CF were evaluated, 18 (36%) were diagnosed with HS (Group A) and 32 (64%) without HS (Group B). The mean age of Group A was 13,2±4,9 years old and Group B 11,7±4,9; for BMI, the value for Group A was 18,0±4,1 and Group B was 15,7±3,8; the TSF of Group A was 8,4±3,5 mm and Group B was 7,0±2,5 mm. For these variables, there was no significant difference between the groups. The mean of MAC and MAMC differed significantly between the groups, being higher in the HS group, with p values of 0,047 and 0,043. Conclusions: The frequency of HS in patients with CF is high and it is not related to malnutrition, according to the parameters of BMI, TSF and MAMC. The values of MAC and MAMC indicated a greater reserve of muscle mass in patients with HS.

The cystic fibrosis transmembrane conductance regulator controls biliary epithelial inflammation and permeability by regulating Src tyrosine kinase activity

In the liver, the cystic fibrosis (CF) transmembrane conductance regulator (CFTR) regulates bile secretion and other functions at the apical membrane of biliary epithelial cells (i.e., cholangiocytes). CF-related liver disease is a major cause of death in patients with CF. CFTR dysfunction affects innate immune pathways, generating a para-inflammatory status in the liver and other epithelia. This study investigates the mechanisms linking CFTR to toll-like receptor 4 activity. We found that CFTR is associated with a multiprotein complex at the apical membrane of normal mouse cholangiocytes, with proteins that negatively control Rous sarcoma oncogene cellular homolog (Src) activity. In CFTR-defective cholangiocytes, Src tyrosine kinase self-activates and phosphorylates toll-like receptor 4, resulting in activation of nuclear factor kappa-light-chain-enhancer of activated B cells and increased proinflammatory cytokine production in response to endotoxins. This Src/nuclear factor kappa-light-chain-enhancer of activated B cells-dependent inflammatory process attracts inflammatory cells but also generates changes in the apical junctional complex and loss of epithelial barrier function. Inhibition of Src decreased the inflammatory response of CF cholangiocytes to lipopolysaccharide, rescued the junctional defect in vitro, and significantly attenuated endotoxin-induced biliary damage and inflammation in vivo (Cftr knockout mice).

CONCLUSION

These findings reveal a novel function of CFTR as a regulator of toll-like receptor 4 responses and cell polarity in biliary epithelial cells; this mechanism is pathogenetic, as shown by the protective effects of Src inhibition in vivo, and may be a novel therapeutic target in CF-related liver disease and other inflammatory cholangiopathies. (Hepatology 2016;64:2118-2134).

Stimulation of nuclear receptor peroxisome proliferator-activated receptor-γ limits NF-κB-dependent inflammation in mouse cystic fibrosis biliary epithelium

Cystic fibrosis-associated liver disease is a chronic cholangiopathy that negatively affects the quality of life of cystic fibrosis patients. In addition to reducing biliary chloride and bicarbonate secretion, up-regulation of toll-like receptor 4/nuclear factor kappa light-chain-enhancer of activated B cells (NF-κB)-dependent immune mechanisms plays a major role in the pathogenesis of cystic fibrosis-associated liver disease and may represent a therapeutic target. Nuclear receptors are transcription factors that regulate several intracellular functions. Some nuclear receptors, including peroxisome proliferator-activated receptor-γ (PPAR-γ), may counterregulate inflammation in a tissue-specific manner. In this study, we explored the anti-inflammatory effect of PPAR-γ stimulation in vivo in cystic fibrosis transmembrane conductance regulator (Cftr) knockout mice exposed to dextran sodium sulfate and in vitro in primary cholangiocytes isolated from wild-type and from Cftr-knockout mice exposed to lipopolysaccharide. We found that in CFTR-defective biliary epithelium expression of PPAR-γ is increased but that this does not result in increased receptor activity because the availability of bioactive ligands is reduced. Exogenous administration of synthetic agonists of PPAR-γ (pioglitazone and rosiglitazone) up-regulates PPAR-γ-dependent genes, while inhibiting the activation of NF-κB and the secretion of proinflammatory cytokines (lipopolysaccharide-induced CXC chemokine, monocyte chemotactic protein-1, macrophage inflammatory protein-2, granulocyte colony-stimulating factor, keratinocyte chemoattractant) in response to lipopolysaccharide. PPAR-γ agonists modulate NF-κB-dependent inflammation by up-regulating nuclear factor of kappa light polypeptide gene enhancer in B cells inhibitor alpha, a negative regulator of NF-κB. Stimulation of PPAR-γ in vivo (rosiglitazone) significantly attenuates biliary damage and inflammation in Cftr-knockout mice exposed to a dextran sodium sulfate-induced portal endotoxemia.

CONCLUSION

These studies unravel a novel function of PPAR-γ in controlling biliary epithelium inflammation and suggest that impaired activation of PPAR-γ contributes to the chronic inflammatory state of CFTR-defective cholangiocytes.

Cystic Fibrosis below the Diaphragm: Abdominal Findings in Adult Patients

Cystic fibrosis (CF) is the most common lethal autosomal recessive disease in the white population. Mutation of the CF transmembrane conductance regulator gene on chromosome 7 results in production of abnormally viscous mucus and secretions in the lungs of patients with CF. A similar pathologic process occurs in the gastrointestinal tract, pancreas, and hepatobiliary system. Inspissated mucus causes luminal obstruction and resultant clinical and radiologic complications associated with the disease process. Pancreatic involvement can result in exocrine and endocrine insufficiency, pancreatic atrophy, fatty replacement, or lipomatous pseudohypertrophy. Acute and chronic pancreatitis, pancreatic calcification, cysts, and cystosis also occur. Hepatic manifestations include hepatic steatosis, focal biliary and multilobular cirrhosis, and portal hypertension. Biliary complications include cholelithiasis, microgallbladder, and sclerosing cholangitis. The entire digestive tract can be involved. Distal ileal obstruction syndrome, intussusception, appendicitis, chronic constipation, colonic wall thickening, fibrosing colonopathy, pneumatosis intestinalis, gastroesophageal reflux, and peptic ulcer disease have been described. Renal manifestations include nephrolithiasis and secondary amyloidosis. The educational objectives of this review are to reveal the abdominal manifestations of CF to facilitate focused analysis of cross-sectional imaging in adult patients. Life expectancy in patients with CF continues to improve because of a combination of aggressive antibiotic treatment, improved emphasis on nutrition and physiotherapy, and development of promising new CF transmembrane conductance regulator modulators. As lung function and survival improve, extrapulmonary conditions, including hepatic and gastrointestinal malignancy, will be an increasing cause of morbidity and mortality. Awareness of the expected abdominal manifestations of CF may assist radiologists in identifying acute inflammatory or neoplastic conditions. (©)RSNA, 2015.

Liver disease in cystic fibrosis: an update

CONTEXT

Cystic fibrosis (CF) is the most widespread autosomal recessive genetic disorder that limits life expectation amongst the Caucasian population. As the median survival has increased related to early multidisciplinary intervention, other manifestations of CF have emerged especially for the broad spectrum of hepatobiliary involvement. The present study reviews the existing literature on liver disease in cystic fibrosis and describes the key issues for an adequate clinical evaluation and management of patients, with a focus on the pathogenetic, clinical and diagnostic-therapeutic aspects of liver disease in CF.

EVIDENCE ACQUISITION

A literature search of electronic databases was undertaken for relevant studies published from 1990 about liver disease in cystic fibrosis. The databases searched were: EMBASE, PubMed and Cochrane Library.

RESULTS

CF is due to mutations in the gene on chromosome 7 that encodes an amino acidic polypeptide named CFTR (cystic fibrosis transmembrane regulator). The hepatic manifestations include particular changes referring to the basic CFTR defect, iatrogenic lesions or consequences of the multisystem disease. Even though hepatobiliary disease is the most common non-pulmonary cause of mortality in CF (the third after pulmonary disease and transplant complications), only about the 33%of CF patients presents clinically significant hepatobiliary disease.

CONCLUSIONS

Liver disease will have a growing impact on survival and quality of life of cystic fibrosis patients because a longer life expectancy and for this it is important its early recognition and a correct clinical management aimed at delaying the onset of complications. This review could represent an opportunity to encourage researchers to better investigate genotype-phenotype correlation associated with the development of cystic fibrosis liver disease, especially for non-CFTR genetic polymorphisms, and detect predisposed individuals. Therapeutic trials are needed to find strategies of fibrosis prevention and to avoid its progression prior to development its related complications.

Acoustic radiation force impulse (ARFI) imaging with Virtual Touch Tissue Quantification in liver disease associated with cystic fibrosis in children

PURPOSE

Cystic-fibrosis-associated liver disease (CFLD) may lead to portal hypertension (PHT) and cirrhosis. Clinical signs and biochemistry of liver involvement are not discriminating. The aim of the study was to evaluate the performance of acoustic radiation force impulse (ARFI) with virtual tissue quantification in comparison with clinical signs, biochemistry and standard hepatic ultrasound (US) patterns.

MATERIALS AND METHODS

Virtual Touch Tissue Quantification, an implementation of US ARFI with shear-wave velocity (SWV) measurements was used in 75 children with cystic fibrosis (CF) and suspected CFLD to quantify hepatic stiffness. In each patient, ten measurements of SWV were performed on the right hepatic lobe. Patients were also evaluated by standard diagnostic tools (standard US, liver- and lung function tests, oesophagogastroscopy).

RESULTS

Among CF patients, median SWV was significantly higher in patients with clinical, biochemical and US signs of hepatic involvement than in patients without US evidence of liver disease 1.08 m/s [(95% confidence interval (CI), 1.02-1.14]. Median SWV values in patients with portal hypertension, splenomegaly and oesophageal varices were 1.30 (95% CI, 1.17-1.43), 1.54 (95% CI, 1.32-1.75) and 1.63 (95% CI, 1.26-1.99), respectively. Differences were significant (p<0.001).

CONCLUSIONS

ARFI is an innovative screening technique able to help identify CFLD in children.

Non-invasive evaluation of cystic fibrosis related liver disease in adults with ARFI, transient elastography and different fibrosis scores

Background

Cystic fibrosis-related liver disease (CFLD) is present in up to 30% of cystic fibrosis patients and can result in progressive liver failure. Diagnosis of CFLD is challenging. Non-invasive methods for staging of liver fibrosis display an interesting diagnostic approach for CFLD detection.

Aim

We evaluated transient elastography (TE), acoustic radiation force impulse imaging (ARFI), and fibrosis indices for CFLD detection.

Methods

TE and ARFI were performed in 55 adult CF patients. In addition, AST/Platelets-Ratio-Index (APRI), and Forns' score were calculated. Healthy probands and patients with alcoholic liver cirrhosis served as controls.

Results

Fourteen CF patients met CFLD criteria, six had liver cirrhosis. Elastography acquisition was successful in >89% of cases. Non-cirrhotic CFLD individuals showed elastography values similar to CF patients without liver involvement. Cases with liver cirrhosis differed significantly from other CFLD patients (ARFI: 1.49 vs. 1.13 m/s; p = 0.031; TE: 7.95 vs. 4.16 kPa; p = 0.020) and had significantly lower results than individuals with alcoholic liver cirrhosis (ARFI: 1.49 vs. 2.99 m/s; p = 0.002). APRI showed the best diagnostic performance for CFLD detection (AUROC 0.815; sensitivity 85.7%, specificity 70.7%).

Conclusions

ARFI, TE, and laboratory based fibrosis indices correlate with each other and reliably detect CFLD related liver cirrhosis in adult CF patients. CF specific cut-off values for cirrhosis in adults are lower than in alcoholic cirrhosis.

Best practice guidance for the diagnosis and management of cystic fibrosis-associated liver disease

Approximately 5-10% of cystic fibrosis (CF) patients develop multilobular cirrhosis during the first decade of life. Most CF patients later develop signs of portal hypertension with complications, mainly variceal bleeding. Liver failure usually occurs later, after the paediatric age. Annual screening for liver disease is recommended to detect pre-symptomatic signs and initiate ursodeoxycholic acid therapy, which might halt disease progression. Liver disease should be considered if at least two of the following variables are present: abnormal physical examination, persistently abnormal liver function tests and pathological ultrasonography. If there is diagnostic doubt, a liver biopsy is indicated. All CF patients with liver disease need annual follow-up to evaluate the development of cirrhosis, portal hypertension or liver failure. Management should focus on nutrition, prevention of bleeding and variceal decompression. Deterioration of pulmonary function is an important consideration for liver transplantation, particularly in children with hepatic dysfunction or advanced portal hypertension.

Ursodeoxycholic acid treatment in patients with cystic fibrosis at risk for liver disease

BACKGROUND

Meconium ileus has been detected as a risk factor for development of liver disease in cystic fibrosis, with influence on morbidity and mortality.

AIMS

To evaluate the effect of early treatment with ursodeoxycholic acid in patients with cystic fibrosis and meconium ileus to prevent chronic hepatic involvement and to explore the potential role of therapy on clinical outcomes.

METHODS

26 cystic fibrosis patients with meconium ileus (16 M, mean age 8,4 years, range 3,5-9) were assigned to two groups: group 1 (14 patients) treated early with ursodeoxycholic acid (UDCAe); group 2 (12 patients) treated with ursodeoxycholic acid at the onset of cystic fibrosis liver disease (UDCAd). Anthropometric data, pulmonary function tests, pancreatic status, complications such as diabetes, hepatic involvement and Pseudomonas aeruginosa colonisation were compared among groups.

RESULTS

A higher prevalence of cystic fibrosis chronic liver disease was observed in the UDCAd group with a statistically significant difference at 9 years of age (p<0.05). Chronic infection by P. aeruginosa was found in 7% of UDCAe and 33% of UDCAd (p<0.05). No differences were observed in nutritional status and other complications.

CONCLUSIONS

Early treatment with ursodeoxycholic acid may be beneficial in patients at risk of developing cystic fibrosis chronic liver disease such as those with meconium ileus. Multicentre studies should be encouraged to confirm these data.

Repression of CFTR activity in human MMNK-1 cholangiocytes induces sulfotransferase 1E1 expression in co-cultured HepG2 hepatocytes

Mouse models of cystic fibrosis (CF) indicate that sulfotransferase (SULT) 1E1 is significantly induced in livers of many mice lacking cystic fibrosis transmembrane receptor (CFTR) activity. Increased SULT1E1 activity results in the alteration of estrogen-regulated protein expression in the livers of these mice. In this study, human MMNK-1 cholangiocytes with repressed CFTR function were used to induce SULT1E1 expression in human HepG2 hepatocytes to investigate whether SULT1E1 can be increased in human CF liver. CFTR expression was inhibited in MMNK-1 cholangiocytes using CFTR-siRNA, then the MMNK-1 and HepG2 cells were co-cultured in a membrane-separated Transwell system. Expression of SULT1E1 and selected estrogen-regulated proteins were then assayed in the HepG2 cells. Results demonstrate that inhibition of CFTR expression in MMNK-1 cells results in the induction of SULT1E1 message and activity in HepG2 cells in the Transwell system. The expression of estrogen-regulated proteins including insulin-like growth factor (IGF)-1, glutathione-S-transferase (GST) P1 and carbonic anhydrase (CA) II expression are repressed in the HepG2 cells cultured with the CFTR-siRNA-MMNK-1 cells apparently in response to the increased sulfation of beta-estradiol. Thus, we have shown that co-culture of HepG2 hepatocytes with MMNK-1 cholangiocytes with siRNA repressed CFTR expression results in the selective induction of SULT1E1 in the HepG2 cells. Loss of CFTR function in cholangiocytes may have a paracrine regulatory effect on hepatocytes via the induction of SULT1E1 and the increased sulfation of beta-estradiol. Experiments are presently underway in our laboratory to elucidate the identity of these paracrine regulatory factors.

Liver disease in cystic fibrosis

PURPOSE OF REVIEW

This review highlights recent developments in liver disease associated with cystic fibrosis.

RECENT FINDINGS

The broad spectrum of hepatobiliary problems in cystic fibrosis includes specific alterations ascribable to the underlying defect as well as lesions of iatrogenic origin or that reflect the effects of a disease process occurring outside the liver. Focal biliary cirrhosis, resulting from biliary obstruction and progressive periportal fibrosis, is the most clinically relevant problem, because extension of the initially focal fibrogenic process may lead to multilobular biliary cirrhosis, portal hypertension and eventually liver failure. Cystic fibrosis associated liver disease is presently classified among genetic cholangiopathies and results from lack or dysfunction of the cystic fibrosis transmembrane regulator at the apical membrane of bile duct cells. Major advances have been achieved regarding characterization of natural history, risk factors, diagnostic modalities and treatment options.

SUMMARY

Liver disease is a relatively frequent and early complication of cystic fibrosis. The pathogenesis is apparently multifactorial, with contributions from environmental and genetic determinants. Its impact on quality of life and survival will increase in future years, and its early detection and treatment will become increasingly important issues. Ursodeoxycholic acid is the only treatment currently available, but novel therapeutic options are being evaluated.

Impact of nutrition on phenotype in CFTR-deficient mice

To elucidate the impact of nutrition in cystic fibrosis (CF), we compared the phenotypic traits of Cftr -/- mice fed either a lipid-enriched liquid diet (Peptamen) or a standard chow combined with polyethylenglycol osmotic laxative (PEG), two strategies commonly used to prevent intestinal obstruction in CF mice. Survival, growth, liver, and ventilatory status were determined in Cftr -/- and Cftr +/+ mice, followed-up until 120 d. Ventilation was recorded in conscious animals using whole-body plethysmography. We found that the survival rate was similar in Peptamen and PEG Cftr -/- mice. Cftr -/- mice had lower minute ventilation than Cftr +/+ mice, whatever the diet. Both Cftr -/- and Cftr +/+ mice fed Peptamen displayed preadult growth delay compared with PEG-treated animals. Despite subsequent growth catch-up, Cftr -/- mice remained smaller than Cftr +/+ mice, whatever the diet. All Peptamen fed Cftr -/- mice showed hepatomegaly and liver steatosis, which also occurred but to a lesser extent in Peptamen fed Cftr +/+ animals. Therefore, while both treatment strategies are similarly efficient to avoid high mortality at weaning, Peptamen induces preadult growth delay and liver steatosis. These effects of diet are important to consider in future animal studies and also prompt to evaluate high-energy diets in CF patients.

Liver manifestations of cystic fibrosis

Chronic liver disease is one of the major complications of cystic fibrosis (CF). Significant liver disease is seen in 13-25% of children with CF. Improved life expectancy and prolonged follow-up have favored better characterization of the hepatic manifestations of CF and allowed direct observation of an increasing number of liver-related events. Liver disease typically develops in the first decade of life, with the incidence dropping rapidly after the age of 10 years. The wide spectrum of liver disease ranging from asymptomatic gallbladder abnormalities to biliary cirrhosis will be reviewed in this article.

Polymorphisms of TGF-beta1 in cystic fibrosis patients

There is a significant phenotypic variance among cystic fibrosis (CF) patients. Due to the role of TGF-beta1 in fibrotic processes we investigated its role in CF pathogenesis. TGF-beta 1 codons 10 and 25 were genotyped in 118 Czech CF patients and 268 controls by PCR-ARMS. Difference between CF and controls was found at codon 10, lower frequency of T/T homozygotes, and codon 25, higher frequency of G/C heterozygotes. We did not prove the association of TGF-beta1 polymorphisms and lung function in CF, however, the TT (codon 10)/GG (codon 25) genotype was preferentially associated with CF-related liver disease and diabetes. Independent of the TGF-beta1 genotype, production of cytokine was higher in patients than in controls with the notable exception of very low levels in Burkholderia cepacia complex colonized patients. In CF, both extremes, highest or lowest TGF-beta 1 production, were associated with impaired lung function.

Liver disease in cystic fibrosis

Liver involvement in Cystic Fibrosis (CF) is much less frequent than both pulmonary and pancreatic diseases that are present in 80-90% of CF patients; liver disease (LD) affects only one third of CF patients, however, because of the decreasing mortality from extrahepatic causes, its recognition and management is becoming a relevant clinical issue. Recent observations suggest that clinical expression of LD in CF may be influenced by genetic modifiers; their identification is an important issue because it may allow recognition of patients at risk for the development of LD at the time of diagnosis of CF and early institution of prophylactic strategies. Oral bile acid therapy, aimed at improving biliary secretion in terms of bile viscosity and bile acid composition, is currently the only available therapeutic approach for CF-associated LD. However, the impact of this therapy on the natural history of LD remains to be defined and long-term effectiveness on clinically relevant outcomes should be further investigated. Liver transplantation should be offered to CF patients with progressive liver failure and/or with life-threatening sequelae of portal hypertension, who also have mild pulmonary involvement that is expected to support long-term survival. The 1-year survival rate after transplantation in CF patients is approximately 80%, with beneficial effects on lung function, nutritional status, body composition and quality of life in most cases.