Influence of pancreatic status on circulating plasma sterols in patients with cystic fibrosis

Liver biochemical indexes and cholesterol metabolism in cystic fibrosis patients with F508del/CFTR variant genotype after elexacaftor/tezacaftor/ivacaftor treatment

Modulators of cystic fibrosis transmembrane conductance regulator (CFTR) improved cystic fibrosis (CF) patients' outcome. The elexacaftor/tezacaftor/ivacaftor (ETI) combination was safe and effective improving lung function in patients with different CFTR genotypes, including at least one F508del mutation. However, cases with liver damage were reported. We describe 105 CF patients heterozygous for F508del in trans with another CFTR mutation, treated for 1 year with ETI. We analyzed liver biochemical parameters and cholesterol metabolism, including lathosterol and phytosterols, surrogate markers of cholesterol de-novo synthesis and absorption, respectively. The treatment significantly improved sweat chloride, body mass index and forced expiratory volume in 1 s, whereas it caused a significant increase of total and conjugated bilirubin, ALT and GGT, even if no patients developed CF liver disease. Such alterations were less relevant than those previously observed in ETI-treated F508del homozygous patients. Furthermore, ETI treatment significantly increased serum cholesterol by enhancing its absorption (correlation between serum cholesterol and phytosterols). Whereas, we observed a normalization of de-novo biosynthesis (lathosterol reduction) that was not observed in homozygous patients. These data suggest that the second mutation in trans with the F508del contributes to reduce the liver cholesterol accumulation and thus, the triggering of liver inflammation. However, no differences in the alteration of biochemical indexes were observed between CF patients with and without liver steatosis, and between patients with different mutations in trans with the F508del. Such data suggest to further investigate the effects of ETI therapy on liver function indexes and new predictive biomarkers.

Treatment of intestinal and liver features in cystic fibrosis mice by the osmotic laxative polyethylene glycol

BACKGROUND

Cystic Fibrosis (CF) is a genetic disease affecting multiple organs, primarily the lungs and digestive system. Improved pulmonary management significantly improved life expectancy of CF patients. As a result, extrapulmonary manifestations, including gastrointestinal and liver-related symptoms, have become more relevant. We previously reported that the osmotic laxative polyethylene glycol (PEG), which hydrates the CF gut, decreased fecal bile acid loss in a CF knockout mouse model. In the current study we investigated the effect of PEG on intestinal fat and cholesterol absorption and on CF-related liver features in a CF mouse model with the most common CF-causing mutation.

METHODS

CftrΔF508/ΔF508 (n=13) and wild-type (WT) (n=12) mice were treated with PEG for 2 weeks. The intestinal and hepatic effects of PEG were assessed by analysis of intestinal bile acid, cholesterol, and fat fluxes, transcriptome analysis as well as histology.

RESULTS

PEG improved intestinal malabsorption of bile acids, fat, and cholesterol in CftrΔF508/ΔF508 mice. Transcriptome analysis showed that PEG partially restored the intestinal signaling of nuclear receptors RXR, FXR, and CAR/PXR, which are involved in bile acid and xenobiotic metabolism. PEG also reduced liver inflammation in CF mice as assessed by transcriptome and histological analyses.

CONCLUSIONS

PEG, a non-absorbable osmotic laxative, improved intestinal nutrient absorption, intestinal bile acid and xenobiotic signaling, as well as CF-related liver features. These findings highlight the potential for osmotic laxation to improve gastrointestinal complications of CF in humans.

One year of treatment with elexacaftor/tezacaftor/ivacaftor in patients with cystic fibrosis homozygous for the F508del mutation causes a significant increase in liver biochemical indexes

Introduction: Modulators of cystic fibrosis transmembrane conductance regulator mutated protein significantly improved the outcome of patients with cystic fibrosis (CF). We describe 63 patients who were independently followed up in two CF regional centers (i.e., Campania and Tuscany regions). Methods: All patients were homozygous for the F508del mutation and were treated with lumacaftor/ivacaftor (LI) for 3 years, followed by 1 year of treatment with elexacaftor/tezacaftor/ivacaftor (ETI). We studied the biochemical parameters of liver damage and cholesterol metabolism. Results: Beyond the improvement of BMI and lung function with LI treatment and even more with ETI, we found that the 3 years of LI treatment significantly improved liver function parameters (total and conjugated bilirubin, ALT, AP, and GGT), while the subsequent ETI treatment caused a significant increase of such parameters. Discussion: We confirm that treatment with LI does not correct hypocholesterolemia, whereas treatment with ETI significantly increases serum cholesterol. Such an increase is likely due to enhanced de novo biosynthesis, as indicated by the significant increase in serum lathosterol, and it is likely that the subsequent liver cholesterol accumulation may contribute to triggering inflammation and worsening liver biochemical indexes. The increase in serum bilirubin and ALT that we observed in approximately 94% and 84% of patients treated with ETI, respectively, suggests further investigation of the impact of ETI therapy on liver function indexes.

Nutritional Care in Children with Cystic Fibrosis

Patients with cystic fibrosis (CF) are prone to malnutrition and growth failure, mostly due to malabsorption caused by the derangement in the chloride transport across epithelial surfaces. Thus, optimal nutritional care and support should be an integral part of the management of the disease, with the aim of ameliorating clinical outcomes and life expectancy. In this report, we analyzed the nutrition support across the different ages, in patients with CF, with a focus on the relationships with growth, nutritional status, disease outcomes and the use of the CF transmembrane conductance regulator (CFTR) modulators. The nutrition support goal in CF care should begin as early as possible after diagnosis and include the achievement of an optimal nutritional status to support the growth stages and puberty development in children, that will further support the maintenance of an optimal nutritional status in adult life. The cornerstone of nutrition in patients with CF is a high calorie, high-fat diet, in conjunction with a better control of malabsorption due to pancreatic enzyme replacement therapy, and attention to the adequate supplementation of fat-soluble vitamins. When the oral caloric intake is not enough for reaching the anthropometric nutritional goals, supplemental enteral feeding should be initiated to improve growth and the nutritional status. In the last decade, the therapeutic possibilities towards CF have grown in a consistent way. The positive effects of CFTR modulators on nutritional status mainly consist in the improvement in weight gain and BMI, both in children and adults, and in an amelioration in terms of the pulmonary function and reduction of exacerbations. Several challenges need to be overcome with the development of new drugs, to transform CF from a fatal disease to a treatable chronic disease with specialized multidisciplinary care.

CFTR Modulator Therapy with Lumacaftor/Ivacaftor Alters Plasma Concentrations of Lipid-Soluble Vitamins A and E in Patients with Cystic Fibrosis

RATIONALE

Cystic fibrosis (CF), caused by mutations in the cystic fibrosis transmembrane conductance regulator (CFTR) gene, leads to impaired pancreatic function and therefore reduced intestinal absorption of lipids and fat-soluble vitamins especially in patients with CF developing pancreatic insufficiency (PI). Previous studies showed that CFTR modulator therapy with lumacaftor-ivacaftor (LUM/IVA) in Phe508del-homozygous patients with CF results in improvement of pulmonary disease and thriving. However, the effects of LUM/IVA on plasma concentration of the lipid soluble vitamins A and E remain unknown.

OBJECTIVES

To investigate the course of plasma vitamin A and E in patients with CF under LUM/IVA therapy.

METHODS

Data from annual follow-up examinations of patients with CF were obtained to assess clinical outcomes including pulmonary function status, body mass index (BMI), and clinical chemistry as well as fat-soluble vitamins in Phe508del-homozygous CF patients before initiation and during LUM/IVA therapy.

RESULTS

Patients with CF receiving LUM/IVA improved substantially, including improvement in pulmonary inflammation, associated with a decrease in blood immunoglobulin G (IgG) from 9.4 to 8.2 g/L after two years (p < 0.001). During the same time, plasma vitamin A increased significantly from 1.2 to 1.6 µmol/L (p < 0.05), however, levels above the upper limit of normal were not detected in any of the patients. In contrast, plasma vitamin E as vitamin E/cholesterol ratio decreased moderately over the same time from 6.2 to 5.5 µmol/L (p < 0.01).

CONCLUSIONS

CFTR modulator therapy with LUM/IVA alters concentrations of vitamins A and vitamin E in plasma. The increase of vitamin A must be monitored critically to avoid hypervitaminosis A in patients with CF.

Severe Genotype, Pancreatic Insufficiency and Low Dose of Pancreatic Enzymes Associate with Abnormal Serum Sterol Profile in Cystic Fibrosis

BACKGROUND

Several factors could lead to lipid disturbances observed in cystic fibrosis (CF). This study aimed to assess sterol homeostasis in CF and define potential exogenous and endogenous determinants of lipid dysregulation.

METHODS

The study involved 55 CF patients and 45 healthy subjects (HS). Sterol concentrations (μg/dL) were measured by gas chromatography/mass spectrometry. CF was characterised by lung function, pancreatic status, liver disease and diabetes coexistence, Pseudomonas aeruginosa colonisation and BMI. CFTR genotypes were classified as severe or other.

RESULTS

Campesterol and β-sitosterol concentrations were lower (p = 0.0028 and p < 0.0001, respectively) and lathosterol levels (reflecting endogenous cholesterol biosynthesis) were higher (p = 0.0016) in CF patients than in HS. Campesterol and β-sitosterol concentrations were lower in patients with a severe CFTR genotype, pancreatic insufficiency and lower pancreatic enzyme dose (lipase units/gram of fat). In multiple regression analyses, β-sitosterol and campesterol concentrations were predicted by genotype and pancreatic insufficiency, whereas cholesterol and its fractions were predicted by phytosterol concentrations, age, dose of pancreatic enzymes, nutritional status and genotype.

CONCLUSIONS

Independent determinants of lipid status suggest that malabsorption and pancreatic enzyme supplementation play a significant role in sterol abnormalities. The measurement of campesterol and β-sitosterol concentrations in CF patients may serve for the assessment of the effectiveness of pancreatic enzyme replacement therapy and/or compliance, but further research is required.

Impaired cholesterol metabolism in the mouse model of cystic fibrosis. A preliminary study

This study aims to investigate cholesterol metabolism in a mouse model with cystic fibrosis (CF) by the comparison of affected homozygous versus wild type (WT) mice. In particular, we evaluated the effects of a diet enriched with cholesterol in both mice groups in comparison with the normal diet. To this purpose, beyond serum and liver cholesterol, we analyzed serum phytosterols as indirect markers of intestinal absorption of cholesterol, liver lathosterol as indirect marker of de novo cholesterol synthesis, liver cholestanol (a catabolite of bile salts synthesis) and the liver mRNA levels of LDL receptor (LDLR), 3-hydroxy-3-methylglutaryl-CoA reductase (HMG-CoAR), acyl CoA:cholesterol acyl transferase 2 (ACAT2), cytochrome P450 7A1 (CYP7A1) and tumor necrosis factor alpha (TNFα). CF mice showed lower intestinal absorption and higher liver synthesis of cholesterol than WT mice. In WT mice, the cholesterol supplementation inhibits the synthesis of liver cholesterol and enhances its catabolism, while in CF mice we did not observe a reduction of LDLR and HMG-CoAR expression (probably due to an altered feed-back), causing an increase of intracellular cholesterol. In addition, we observed a further increase (5-fold) in TNFα mRNA levels. This preliminary study suggests that in CF mice there is a vicious circle in which the altered synthesis/secretion of bile salts may reduce the digestion/absorption of cholesterol. As a result, the liver increases the biosynthesis of cholesterol that accumulates in the cells, triggering inflammation and further compromising the metabolism of bile salts.

Lumacaftor/ivacaftor improves liver cholesterol metabolism but does not influence hypocholesterolemia in patients with cystic fibrosis

BACKGROUND

Cystic fibrosis (CF) patients have reduced intestinal absorption of sterols and, despite enhanced endogenous synthesis, low plasma cholesterol. Lumacaftor/ivacaftor CFTR protein modulator therapy is used to improve the clinical outcome of CF patients homozygous for F508del mutation (homo-deltaF508). Aim of the study is to evaluate the cholesterol metabolism and hepatobiliary injury/function in adult homo-deltaF508 patients, before and after lumacaftor/ivacaftor treatment. Baseline parameters in homo-deltaF508 patients were compared to those in CF patients compound heterozygous for F508del mutation and another severe mutation (hetero-deltaF508).

METHODS

Cholesterol metabolism was evaluated measuring plasma phytosterols and cholestanol, as intestinal absorption markers, and lathosterol, as liver biosynthesis marker. We quantified serum vitamin E, as nutritional marker. We evaluated liver injury by aspartate aminotransferase (AST) and alanine transaminase (ALT), biliary injury by γ-glutamyltransferase (γGT) and AP, and the liver function by bilirubin and albumin.

RESULTS

Before the treatment, homo-deltaF508 patients (n = 20) had significantly lower cholesterol and vitamin E compared to hetero-deltaF508 (n = 20). Lumacaftor/ivacaftor treatment caused: 1) further reduction of cholesterol; 2) lathosterol reduction, suggesting a normalization of endogenous synthesis; 3) cholestanol and vitamin E increment, indicating an improvement of lipid digestion/absorption. Vitamin E difference (after-before treatment) was positively associated to treatment months. Alkaline phosphatase was also reduced.

CONCLUSIONS

These data suggest an effect of lumacaftor/ivacaftor on cholesterol metabolism and enterohepatic flux in CF patients. However, lumacaftor/ivacaftor does not promote the increase of cholesterol serum concentration that on the contrary declines. Further studies are needed to research the real mechanism causing this reduction.