Influence of the BsmI polymorphism of the vitamin D receptor gene on the levels of vitamin D, inflammatory and oxidative stress profile in patients with cystic fibrosis supplemented with Colecalciferol megadose.

OBJECTIVE: Evaluate the influence of the BsmI polymorphism of the vitamin D receptor gene on vitamin D levels, and inflammatory and oxidative stress markers in patients with Cystic Fibrosis supplemented with cholecalciferol megadose. METHODS: We performed a single-arm, non-randomized pre- and post-study of 17 patients aged 5 to 20 years with cystic fibrosis diagnosed with vitamin D insufficiency/deficiency 25-hydroxy vitamin< 30 ng/mL. Individuals were genotyped for the BsmI polymorphism of the vitamin D receptor gene and all received cholecalciferol supplementation of 4,000 IU daily for children aged 5 to 10 years and 10,000 IU for children over 10 years of age for 8 weeks. Interviews were conducted with personal data, sun exposure, anthropometric and blood samples of 25-hydroxy vitamin parathormone, serum calcium, ultrasensitive C-reactive protein, alpha 1 acid glycoprotein, total antioxidant capacity, malondialdehyde and kidney and liver function. Inter- and intra-group assessment was assessed by paired t-test Anova test or its non-parametric counterparts. RESULTS: The individuals were mostly male and reported no adverse effects from the use of supplementation, 64 % had 25-hydroxy vitamin levels >30 ng/mL. Patients with BB and Bb genotypes showed increased serum levels of 25-hydroxy vitamin. The group with BB genotype showed a reduction in alpha 1 acid glycoprotein. And individuals with the bb genotype had high levels of malondialdehyde compared to the pre-intervention time. CONCLUSION: It is concluded that variations of the BsmI polymorphism of the vitamin D receptor gene have different responses in vitamin D levels and markers of inflammation and oxidative stress.

Vitamin D status and variable responses to supplements depend in part on genetic factors in adults with cystic fibrosis.

Vitamin D sufficiency has been difficult to achieve consistently in patients with cystic fibrosis (CF), even with robust oral supplements. To assess vitamin D status and resistance to supplementation, we studied 80 adults using 25-hydroxyvitamin D (25OHD) determinations and whole genome sequencing to construct polygenic risk scores (PRS) that aggregate variants associated with vitamin D status. The results revealed that 30 % of patients were below the threshold of 30 ng/mL and thus should be regarded as insufficient despite normal vitamin E status, a reflection of adherence to fat soluble vitamin supplementation. The PRS values were significantly correlated with 25OHD concentrations, confirming our results in children with CF, and indicating that genetic factors play a role and have implications for therapy.

FDA-approved drug screening in patient-derived organoids demonstrates potential of drug repurposing for rare cystic fibrosis genotypes.

BACKGROUND: Preclinical cell-based assays that recapitulate human disease play an important role in drug repurposing. We previously developed a functional forskolin induced swelling (FIS) assay using patient-derived intestinal organoids (PDIOs), allowing functional characterization of CFTR, the gene mutated in people with cystic fibrosis (pwCF). CFTR function-increasing pharmacotherapies have revolutionized treatment for approximately 85% of people with CF who carry the most prevalent F508del-CFTR mutation, but a large unmet need remains to identify new treatments for all pwCF. METHODS: We used 76 PDIOs not homozygous for F508del-CFTR to test the efficacy of 1400 FDA-approved drugs on improving CFTR function, as measured in FIS assays. The most promising hits were verified in a secondary FIS screen. Based on the results of this secondary screen, we further investigated CFTR elevating function of PDE4 inhibitors and currently existing CFTR modulators. RESULTS: In the primary screen, 30 hits were characterized that elevated CFTR function. In the secondary validation screen, 19 hits were confirmed and categorized in three main drug families: CFTR modulators, PDE4 inhibitors and tyrosine kinase inhibitors. We show that PDE4 inhibitors are potent CFTR function inducers in PDIOs where residual CFTR function is either present, or created by additional compound exposure. Additionally, upon CFTR modulator treatment we show rescue of CF genotypes that are currently not eligible for this therapy. CONCLUSION: This study exemplifies the feasibility of high-throughput compound screening using PDIOs. We show the potential of repurposing drugs for pwCF carrying non-F508del genotypes that are currently not eligible for therapies. ONE-SENTENCE SUMMARY: We screened 1400 FDA-approved drugs in CF patient-derived intestinal organoids using the previously established functional FIS assay, and show the potential of repurposing PDE4 inhibitors and CFTR modulators for rare CF genotypes.

Effects of prolonged proton pump inhibitor treatment on nutritional status and respiratory infection risk in cystic fibrosis: A matched cohort study.

BACKGROUND: Evidence on the effectiveness of proton pump inhibitors (PPI) as adjuvant therapy to improve maldigestion in people with cystic fibrosis (pwCF) is limited and there is increasing concern on possible side effects. METHODS: We conducted a matched cohort study based on paediatric and adult pwCF who received PPI for ≥3 months. Treated patients were matched to a group of patients who never received PPI using a nearest neighbour propensity score matching based on sex, year of birth, CFTR genotype and pancreatic insufficiency. RESULTS: The study included 160 pwCF: 80 treated and 80 untreated patients. Over a median follow-up of 2 years, no significant differences in changes in BMI z-score were detected between groups (adjusted mean difference: 0.06, 95% CI: -0.17-0.30). At baseline 25% (n = 20) of the treated patients and 22.5% (n = 18) of the untreated patients had a positive culture for P. aeruginosa (Pa). At follow-up percentages of Pa positive cultures increased to 47.5% (n = 38) in the treated group and to 26.3% (n = 21) in the untreated group (adjusted mean difference: 23.1%, 95% CI: 10.8-35.3). CONCLUSIONS: Prolonged PPI therapy should be used cautiously in pwCF since it may increase the risk of respiratory infection by Pa. In addition, such treatment does not seem to improve nutritional status.

Virtual Drug Repositioning as a Tool to Identify Natural Small Molecules That Synergize with Lumacaftor in F508del-CFTR Binding and Rescuing.

Cystic fibrosis is a hereditary disease mainly caused by the deletion of the Phe 508 (F508del) of the cystic fibrosis transmembrane conductance regulator (CFTR) protein that is thus withheld in the endoplasmic reticulum and rapidly degraded by the ubiquitin/proteasome system. Cystic fibrosis remains a potentially fatal disease, but it has become treatable as a chronic condition due to some CFTR-rescuing drugs that, when used in combination, increase in their therapeutic effect due to a synergic action. Also, dietary supplementation of natural compounds in combination with approved drugs could represent a promising strategy to further alleviate cystic fibrosis symptoms. On these bases, we screened by in silico drug repositioning 846 small synthetic or natural compounds from the AIFA database to evaluate their capacity to interact with the highly druggable lumacaftor binding site of F508del-CFTR. Among the identified hits, nicotinamide (NAM) was predicted to accommodate into the lumacaftor binding region of F508del-CFTR without competing against the drug but rather stabilizing its binding. The effective capacity of NAM to bind F508del-CFTR in a lumacaftor-uncompetitive manner was then validated experimentally by surface plasmon resonance analysis. Finally, the capacity of NAM to synergize with lumacaftor increasing its CFTR-rescuing activity was demonstrated in cell-based assays. This study suggests the possible identification of natural small molecules devoid of side effects and endowed with the capacity to synergize with drugs currently employed for the treatment of cystic fibrosis, which hopefully will increase the therapeutic efficacy with lower doses.

Genetic factors help explain the variable responses of young children with cystic fibrosis to vitamin D supplements.

BACKGROUND & AIMS: Children with cystic fibrosis (CF) are susceptible to fat-soluble vitamin deficiencies unless supplemented, but even large doses of vitamin D may not prevent low 25-hydroxyvitamin D (25OHD) concentrations. The explanation for these vitamin D non-responders has been elusive. We utilized data from whole genome sequencing (WGS) to test the hypothesis that genetic variations predict responsiveness to vitamin D supplementation in a prospective cohort study of children with CF in the first 3 years of life. METHODS: One hundred and one infants born during 2012-2017 and diagnosed with CF through newborn screening were studied. Serum 25OHD concentrations and vitamin D supplement doses were assessed during early infancy and annually thereafter. WGS was performed, the resultant variant calling files processed, and the summary statistics from a recent genome-wide association study were utilized to construct a polygenic risk score (PRS) for each subject. RESULTS: Overall, the prevalence of vitamin D insufficiency (<30 ng/mL) was 21% in the first 3 years of life. Among the 70 subjects who always adhered to vitamin D supplement doses recommended by the US CF Foundation guidelines, 89% were responders (achieved vitamin D sufficiency) by 3 years of age, while 11% were transient or non-responders. Multiple regression analysis revealed that PRS was a significant predictor of 25OHD concentrations (p < 0.001) and the likelihood of being an earlier responder in the first 3 years of life (p < 0.01). A limited SNP analysis revealed variants in four important genes (GC, LIPC, CYP24A1, and PDE3B) that were shown to be associated with 25OHD concentrations and vitamin D responder status. Other determinants included vitamin D supplement dose, season at 25OHD measurement, and pancreatic functional status. CONCLUSIONS: Applying WGS in conjunction with utilizing a PRS approach revealed genetic variations that partially explain the unresponsiveness of some children with CF to vitamin D supplementation. Our findings suggest that a nutrigenomics strategy could help promote personalized treatment in CF.

Role of inflammation and oxidative stress in tissue damage associated with cystic fibrosis: CAPE as a future therapeutic strategy.

Cystic fibrosis (CF) is an autosomal recessive disease caused by mutations in the cystic fibrosis transmembrane conductance regulator (CFTR) gene, responsible for the synthesis of the CFTR protein, a chloride channel. The gene has approximately 2000 known mutations and all of them affect in some degree the protein function, which makes the pathophysiological manifestations to be multisystemic, mainly affecting the respiratory, gastrointestinal, endocrine, and reproductive tracts. Currently, the treatment of the disease is restricted to controlling symptoms and, more recently, a group of drugs that act directly on the defective protein, known as CFTR modulators, was developed. However, their high cost and difficult access mean that their use is still very restricted. It is important to search for safe and low-cost alternative therapies for CF and, in this context, natural compounds and, mainly, caffeic acid phenethyl ester (CAPE) appear as promising strategies to assist in the treatment of the disease. CAPE is a compound derived from propolis extracts that has antioxidant and anti-inflammatory activities, covering important aspects of the pathophysiology of CF, which points to the possible benefit of its use in the disease treatment. To date, no studies have effectively tested CAPE for CF and, therefore, we intend with this review to elucidate the role of inflammation and oxidative stress for tissue damage seen in CF, associating them with CAPE actions and its pharmacologically active derivatives. In this way, we offer a theoretical basis for conducting preclinical and clinical studies relating the use of this molecule to CF.

Resolution of severe hepatosteatosis in a cystic fibrosis patient with multifactorial choline deficiency: A case report.

In cystic fibrosis (CF), 85% to 90% of patients develop exocrine pancreatic insufficiency. Despite enzyme substitution, low pancreatic phospholipase A2 (sPLaseA2-IB) activity causes fecal loss of bile phosphatidylcholine and choline deficiency. We report on a female patient who has CF and progressive hepatosteatosis from 4.5 y onward. At 22.3 y, the liver comprised 27% fat (2385 mL volume) and transaminases were strongly increased. Plasma choline was 1.9 µmol/L (normal: 8-12 mol/L). Supplementation with 3 ×  1g/d choline chloride decreased liver fat and volume (3 mo: 8.2%; 1912 mL) and normalized transaminases. Plasma choline increased to only 5.6 µmol/L upon supplementation, with high trimethylamine oxide levels (12-35 µmol/L; normal: 3 ± 1 mol/L) proving intestinal microbial choline degradation. The patient was homozygous for rs12325817, a frequent single-nucleotide polymorphism in the PEMT gene, associated with severe hepatosteatosis in response to choline deficiency. Resolution of steatosis required 2 y (4.5% fat). Discontinuation/resumption of choline supplementation resulted in rapid relapse/resolution of steatosis, increased transaminases, and abdominal pain.

Is the ENaC Dysregulation in CF an Effect of Protein-Lipid Interaction in the Membranes?

While approximately 2000 mutations have been discovered in the gene coding for the cystic fibrosis transmembrane conductance regulator (CFTR), only a small amount (about 10%) is associated with clinical cystic fibrosis (CF) disease. The discovery of the association between CFTR and the hyperactive epithelial sodium channel (ENaC) has raised the question of the influence of ENaC on the clinical CF phenotype. ENaC disturbance contributes to the pathological secretion, and overexpression of one ENaC subunit, the ß-unit, can give a CF-like phenotype in mice with normal acting CFTR. The development of ENaC channel modulators is now in progress. Both CFTR and ENaC are located in the cell membrane and are influenced by its lipid configuration. Recent studies have emphasized the importance of the interaction of lipids and these proteins in the membranes. Linoleic acid deficiency is the most prevailing lipid abnormality in CF, and linoleic acid is an important constituent of membranes. The influence on sodium excretion by linoleic acid supplementation indicates that lipid-protein interaction is of importance for the clinical pathophysiology in CF. Further studies of this association can imply a simple clinical adjuvant in CF therapy.

Perinatal Reduced Blood Concentrations of Free Carnitine and Acylcarnitines in Infants with Cystic Fibrosis.

OBJECTIVE: Cystic fibrosis (CF) is a multisystemic inherited disease. The aim of this study was to determine free carnitine (FC) and acylcarnitine concentrations in CF newborns with various mutations of the CFTR gene perinatally. STUDY DESIGN: FC/acylcarnitines were determined in dried blood spots via liquid chromatography-tandem mass spectrometry (LC-MS/MS) on the third day of life of full-term normal (n = 50) and CF (n = 28) newborns. For infants with elevated immunoreactive trypsinogen values, FC/acylcarnitines were quantified again 48 hours later, followed by mutational analysis of CFTR gene via Sanger sequencing. RESULTS: Initial FC and sums of acylcarnitine concentrations were statistically significantly lower in CF patients than in controls and even lower 48 hours later. The mutations F508del and 621 + 1G > T were predominantly identified among CF patients. CONCLUSION: Low FC and acylcarnitine concentrations were measured perinatally in CF patients, for all CFTR mutations detected. Carnitine supplementation of breastfeeding mothers could be beneficial.

Identification of Compounds That Promote Readthrough of Premature Termination Codons in the CFTR.

Cystic fibrosis (CF) is caused by a mutation of the Cystic Fibrosis Transmembrane Conductance Regulator (CFTR) gene, which disrupts an ion channel involved in hydration maintenance via anion homeostasis. Nearly 5% of CF patients possess one or more copies of the G542X allele, which results in a stop codon at residue 542, preventing full-length CFTR protein synthesis. Identifying small-molecule modulators of mutant CFTR biosynthesis that affect the readthrough of this and other premature termination codons to synthesize a fully functional CFTR protein represents a novel target area of drug discovery. We describe the implementation and integration for large-scale screening of a homogeneous, 1536-well functional G542X-CFTR readthrough assay. The assay uses HEK 293 cells engineered to overexpress the G542X-CFTR mutant, whose functional activity is monitored with a membrane potential dye. Cells are co-incubated with a CFTR amplifier and CFTR corrector to maximize mRNA levels and trafficking of CFTR to the cell surface. Compounds that allow translational readthrough and synthesis of functional CFTR chloride channels are reflected by changes in membrane potential in response to cAMP stimulation with forskolin and CFTR channel potentiation with genistein. Assay statistics yielded Z' values of 0.69 ± 0.06. As further evidence of its suitability for high-throughput screening, we completed automated screening of approximately 666,000 compounds, identifying 7761 initial hits. Following secondary and tertiary assays, we identified 188 confirmed hit compounds with low and submicromolar potencies. Thus, this approach takes advantage of a phenotypic screen with high-throughput scalability to identify new small-molecule G542X-CFTR readthrough modulators.

Emerging preclinical modulators developed for F508del-CFTR have the potential to be effective for ORKAMBI resistant processing mutants.

BACKGROUND: F508del is prototypical of Class 2 CFTR mutations associated with protein misprocessing and reduced function. Corrector compounds like lumacaftor partially rescue the processing defect of F508del-CFTR whereas potentiators like ivacaftor, enhance its channel activity once trafficked to the cell surface. We asked if emerging modulators developed for F508del-CFTR can rescue Class 2 mutations previously shown to be poorly responsive to lumacaftor and ivacaftor. METHODS: Rescue of mutant CFTRs by the correctors: AC1, AC2-1 or AC2-2 and the potentiator, AP2, was studied in HEK-293 cells and in primary human nasal epithelial (HNE) cultures, using a membrane potential assay and Ussing chamber, respectively. RESULTS: In HEK-293 cells, we found that a particular combination of corrector molecules (AC1 plus AC2-1) and a potentiator (AP2) was effective in rescuing both the misprocessing and reduced function of M1101K and G85E respectively. These findings were recapitulated in patient-derived nasal cultures, although another corrector combination, AC1 plus AC2-2 also improved misprocessing in these primary tissues. Interestingly, while this corrector combination only led to a modest increase in the abundance of mature N1303K-CFTR it did enable its functional expression in the presence of the potentiator, AP2, in part, because the nominal corrector, AC2-2 also exhibits potentiator activity. CONCLUSIONS: Strategic combinations of novel modulators can potentially rescue Class 2 mutants thought to be relatively unresponsive to lumacaftor and ivacaftor.

Dietary Macronutrient Distribution and Nutrition Outcomes in Persons with Cystic Fibrosis: An Evidence Analysis Center Systematic Review.

Cystic fibrosis (CF) increases risk for undernutrition and malabsorption. Individuals with CF traditionally have been counseled to consume a high-fat diet. However, a new era of CF care has increased lifespan and decreased symptoms in many individuals with CF, necessitating a re-examination of the high-fat CF legacy diet. A literature search was conducted of Medline (Ovid), Embase, and CINAHL (EBSCO) databases to identify articles published from January 2002 to May 2018 in the English language examining the relationships between dietary macronutrient distribution and nutrition outcomes in individuals with CF. Articles were screened, risk of bias was assessed, data were synthesized narratively, and each outcome was graded for certainty of evidence. The databases search retrieved 2,519 articles, and 7 cross-sectional articles were included in the final narrative analysis. Three studies examined pediatric participants and 4 examined adults. None of the included studies reported on outcomes of mortality or quality of life. Very low certainty evidence described no apparent relationship between dietary macronutrient distribution and lung function, anthropometric measures, or lipid profile in individuals with CF. The current systematic review demonstrates wide ranges in the dietary macronutrient intakes of individuals with CF with little to no demonstrable relationship between macronutrient distribution and nutrition-related outcomes. No evidence is presented to substantiate an outcomes-related benefit to a higher fat-diet except in the context of achieving higher energy intakes in a lesser volume of food.

Distal intestinal obstruction syndrome: a diagnostic and therapeutic challenge in cystic fibrosis / Síndrome da obstruc¸ão intestinal distal: um desafio diagnóstico e terapêutico na fibrose cística

Abstract Objective: To evaluate the demographics, genotype, and clinical presentation of pediatric patients presenting with distal intestinal obstruction syndrome (DIOS), and factors associated with DIOS recurrence. Methods: Case series of ten patients (median age 13.2 years), followed-up in a reference center, retrospectively assessed. Data analyzed included age, gender, cystic fibrosis genotype, meconium ileus at birth, hydration status, pulmonary exacerbation, Pseudomonas aeruginosa colonization, pancreatic insufficiency (PI), body mass index (BMI) at the episodes, clinical manifestations of DIOS, imaging studies performed, acute management of DIOS, maintenance therapy, and recurrence on follow-up. Results: All patients had two positive sweat chloride tests, and nine of ten also had genotype study. The most common genotype identified was homozygosis for the delta F508 mutation. In seven cases, a previous history of meconium ileus was reported. All patients had pancreatic insufficiency. Diagnosis of DIOS was based on clinical and imaging findings. Of the total number of episodes, 85% were successfully managed with oral osmotic laxatives and/or rectal therapy (glycerin enema or saline irrigation). Recurrence was observed in five of ten patients. Conclusion In this first report of pediatric DIOS in South America, the presence of two risk factors for DIOS occurrence was universal: pancreatic insufficiency and severe genotype. Medical history of meconium ileus at birth was present in most patients, as well as in the subgroup with DIOS recurrence. The diagnosis relied mainly on the clinical presentation and on abdominal imaging. The practices in the management of episodes varied, likely reflecting changes in the management of this syndrome throughout time.

Resumo Objetivo: Avaliar os dados demográficos, o genótipo e o quadro clínico de pacientes pediátricos que apresentam síndrome da obstrução intestinal distal (DIOS) e os fatores associados à recidiva da DIOS. Métodos: Casuística de 10 pacientes (média de 13,2 anos) monitorados em um centro de referência e avaliados de forma retroativa. Os dados analisados incluíram idade, sexo, genótipo da fibrose cística, íleo meconial no nascimento, estado de hidratação, exacerbação pulmonar, colonização por Pseudomonas aeruginosa, insuficiência pancreática (IP), IMC nos episódios, manifestações clínicas da DIOS, estudos de diagnóstico por imagem realizados, manejo agudo da DIOS, terapia de manutenção e recidiva no acompanhamento. Resultados: Todos os pacientes apresentaram dois exames de cloreto no suor positivos e 09/10 também apresentaram estudo do genótipo. O genótipo mais comum identificado foi a homozigose da mutação delta F508. Em sete casos foi mencionado um histórico de íleo meconial. Todos os pacientes apresentaram insuficiência pancreática. O diagnóstico da DIOS teve como base achados clínicos e de imagem; 85% do número total de episódios foram tratados com sucesso com laxantes osmóticos orais e/ou terapia retal (enema de glicerina ou irrigação salina). A recidiva foi observada em 5 de 10 pacientes. Conclusão: Neste primeiro relatório da DIOS pediátrica na América do Sul, a presença de dois fatores de risco na ocorrência da DIOS foi universal: insuficiência pancreática e genótipo associado a doença grave. O histórico de íleo meconial no nascimento esteve presente na maioria dos pacientes, bem como no subgrupo com recidiva da DIOS. O diagnóstico dependeu principalmente do quadro clínico e do diagnóstico por imagem abdominal. As práticas de manejo de episódios variaram, provavelmente refletiram as mudanças no tratamento dessa síndrome ao longo do tempo.

Pseudo-Bartter syndrome in Chinese children with cystic fibrosis: Clinical features and genotypic findings.

OBJECTIVES: To characterize the clinical and genotypic features of cystic fibrosis-associated pseudo-Bartter syndrome (CF-PBS) in Chinese children. METHODS: We recruited and characterized the clinical manifestations of 12 Chinese children with CF-PBS. Sweat test, blood and urinary analysis, sputum culture, chest and sinus computed tomography, and abdominal ultrasonography were obtained. Whole-exome sequencing, bioinformatics analysis, and Sanger sequencing validation were performed to define the genotypes. RESULTS: CF-PBS was accompanied by recurrent and/or persistent pneumonia (91.7%), pancreatitis (83.3%), vomiting and/or diarrhea (66.7%), failure to thrive and liver disease (58.3% respectively), among our patients. The predominant organisms found in the airways were Pseudomonas aeruginosa (83.3%) and Staphylococcus aureus (75.0%). The mean concentrations of blood gas and electrolytes were pH 7.58, bicarbonate 40.8 mmol/L, sodium 125.9 mmol/L, chloride 77.5 mmol/L, and potassium 2.6 mmol/L. A high recurrence rate (50.0%) of CF-PBS was observed despite continued electrolyte supplementation during follow-up. In all, 19 different variants of CFTR gene were identified, and 10 of these were found to be novel observations (c.262_266delTTATA[p.L88FfsX21], c.579+2insACAT, c.1210-3C>G, c.1733T>C[p.L578P], c.2236_2246delGAGGCGATACTinsAAAAATC[p.E746KfsX8], c.3068T>G [p.I1023R], c.3635delT[p.V1212AfsX16], c.3859delG[p.G1287EfsX2], c.3964-7A>G and ΔE23 [c.3718-?_3873+?del]). The c.2909G>A[p.G970D] was the most common variant, with an allele frequency of 16.6%. A homozygous genotype of c.1521_1523delCTT[p.F508del] was discovered for the first time in patients of Chinese origin. CONCLUSIONS: In China, CF-PBS usually presents early and recurs frequently in infancy, accompanied by multiple comorbidities. Recurrence of CF-PBS in school-going patients does occur but is rare. The p.G970D is the most frequent variant, with a significant ethnic tendency of Chinese origin.

Sodium Status and Replacement in Children and Adults Living with Cystic Fibrosis: A Narrative Review.

Patients with cystic fibrosis (CF) have a two- to four-fold higher sodium chloride sweat content compared with healthy controls. This high sweat salt loss increases the risk for electrolyte disturbances, associated with subacute or chronic complications. Sodium status therefore needs to be adequately monitored and salt intake adjusted to individual needs. The lack of current evidence to formulate specific recommendations and assess sodium status is reflected in a variability of recommendations in international guidelines. This narrative review presents an overview of the current evidence. Infants with CF in particular are at risk for severe sodium deficiency, potentially leading to metabolic alkalosis due to low intake and high sweat losses. More research on the assessment of sodium status and efficacy of sodium chloride supplements in the population of patients with CF, especially given the changing era of CF transmembrane conductance regulator modulatory treatment, is warranted.

Apolipoprotein E polymorphism and vitamin K status in cystic fibrosis patients not supplemented with vitamin K.

OBJECTIVE: ApoE alleles have been shown to significantly correlate with vitamin K status, however, data concerning this phenomenon in cystic fibrosis (CF) are scarce. This study aimed to investigate the effect of ApoE polymorphism on vitamin K status in a unique group of CF patients who had never received vitamin K supplementation. PATIENTS AND METHODS: The study group consisted of 93 CF patients aged from 3 months to 32 years. Vitamin K status was assessed by the concentration of prothrombin induced by vitamin K absence (PIVKA-II) and the percentage of undercarboxylated osteocalcin (u-OC). The clinical status was evaluated in all patients. RESULTS: Fifty-four (65.1%) out of 83 patients had a pathological PIVKA-II concentration (≥2 ng/ml) and an abnormal percentage of u-OC (≥20%). There were no differences in the clinical parameters, including PIVKA-II concentration (p=0.7752) and u-OC percentage (p=0.8395), between patients with genotypes ApoE2/3, ApoE3/3 and ApoE3/4. Moreover, the frequency of vitamin K deficiency did not significantly differ in CF patients with ApoE2/3, ApoE3/3 and ApoE3/4 genotypes (66.7 vs. 69.9 vs. 80%, p=0.8411; 87.5 vs. 89.6 vs. 100%, p=1.000, respectively). CONCLUSIONS: The presence of the ApoE4 allele does not influence the vitamin K status in CF patients who have never received vitamin K supplementation.

Ivacaftor Reverses Airway Mucus Abnormalities in a Rat Model Harboring a Humanized G551D-CFTR.

Rationale: Animal models have been highly informative for understanding the characteristics, onset, and progression of cystic fibrosis (CF) lung disease. In particular, the CFTR-/- rat has revealed insights into the airway mucus defect characteristic of CF but does not replicate a human-relevant CFTR (cystic fibrosis transmembrane conductance regulator) variant.Objectives: We hypothesized that a rat expressing a humanized version of CFTR and harboring the ivacaftor-sensitive variant G551D could be used to test the impact of CFTR modulators on pathophysiologic development and correction.Methods: In this study, we describe a humanized-CFTR rat expressing the G551D variant obtained by zinc finger nuclease editing of a human complementary DNA superexon, spanning exon 2-27, with a 5' insertion site into the rat gene just beyond intron 1. This targeted insertion takes advantage of the endogenous rat promoter, resulting in appropriate expression compared with wild-type animals.Measurements and Main Results: The bioelectric phenotype of the epithelia recapitulates the expected absence of CFTR activity, which was restored with ivacaftor. Large airway defects, including depleted airway surface liquid and periciliary layers, delayed mucus transport rates, and increased mucus viscosity, were normalized after the administration of ivacaftor.Conclusions: This model is useful to understand the mechanisms of disease and the extent of pathology reversal with CFTR modulators.

Highly Efficient Gene Editing of Cystic Fibrosis Patient-Derived Airway Basal Cells Results in Functional CFTR Correction.

There is a strong rationale to consider future cell therapeutic approaches for cystic fibrosis (CF) in which autologous proximal airway basal stem cells, corrected for CFTR mutations, are transplanted into the patient's lungs. We assessed the possibility of editing the CFTR locus in these cells using zinc-finger nucleases and have pursued two approaches. The first, mutation-specific correction, is a footprint-free method replacing the CFTR mutation with corrected sequences. We have applied this approach for correction of ΔF508, demonstrating restoration of mature CFTR protein and function in air-liquid interface cultures established from bulk edited basal cells. The second is targeting integration of a partial CFTR cDNA within an intron of the endogenous CFTR gene, providing correction for all CFTR mutations downstream of the integration and exploiting the native CFTR promoter and chromatin architecture for physiologically relevant expression. Without selection, we observed highly efficient, site-specific targeted integration in basal cells carrying various CFTR mutations and demonstrated restored CFTR function at therapeutically relevant levels. Significantly, Omni-ATAC-seq analysis revealed minimal impact on the positions of open chromatin within the native CFTR locus. These results demonstrate efficient functional correction of CFTR and provide a platform for further ex vivo and in vivo editing.