Weight increase in people with cystic fibrosis on CFTR modulator therapy is mainly due to increase in fat mass

Progress of personalized medicine of cystic fibrosis in the times of efficient CFTR modulators

BACKGROUND

Cystic fibrosis (CF) is a systemic disorder of exocrine glands that is caused by mutations in the CFTR gene.

MAIN BODY

The basic defect in people with CF (pwCF) leads to impaired epithelial transport of chloride and bicarbonate that can be assessed by CFTR biomarkers, i.e. the β-adrenergic sweat rate and sweat chloride concentration (SCC), chloride conductance of the nasal respiratory epithelium (NPD), urine secretion of bicarbonate, intestinal current measurements (ICM) of chloride secretory responses in rectal biopsies and in bioassays of chloride transport in organoids or cell cultures. CFTR modulators are a novel class of drugs that improve defective posttranslational processing, trafficking and function of mutant CFTR. By April 2025, triple combination therapy with the CFTR potentiator ivacaftor (IVA) and the CFTR correctors elexacaftor (ELX) and tezacaftor (TEZ) has been approved in Europe for the treatment of all pwCF who do not carry two minimal function CFTR mutations. Previous phase 3 and post-approval phase 4 studies in pwCF who harbour one or two alleles of the major mutation F508del consistently reported significant improvements of lung function and anthropometry upon initiation of ELX/TEZ/IVA compared to baseline. Normalization of SCC, NPD and ICM correlated with clinical outcomes on the population level, but the restoration of CFTR function was diverse and not predictive for clinical outcome in the individual patient. Theratyping of non-F508del CF genotypes in patient-derived organoids and cell cultures revealed for most cases clinically meaningful increases of CFTR activity upon exposure to ELX/TEZ/IVA. Likewise, every second CF patient with non-F508del genotypes improved in SCC and clinical outcome upon exposure to ELX/TEZ/IVA indicating that triple CFTR modulator therapy is potentially beneficial for all pwCF who do not carry two minimal function CFTR mutations. This group who is not eligible for CFTR modulators may opt for gene addition therapy in the future, as the first-in-human trial with a recombinant lentiviral vector is underway.

FUTURE DIRECTIONS

The upcoming generation of pwCF will probably experience a rather normal life in childhood and adolescence. To classify the upcoming personal signatures of CF disease in the times of efficient modulators, we need more sensitive CFTR biomarkers that address the long-term course of airway and gut microbiome, host defense, epithelial homeostasis and multiorgan metabolism.

20 years of the Montreal Cystic Fibrosis Related Diabetes Screening Cohort: key insights

INTRODUCTION

The Montreal Cystic Fibrosis Related Diabetes Screening Cohort (MCFC) was established in 2004 to study the prevalence, risk factors and management of cystic fibrosis-related diabetes, a significant extrapulmonary complication of cystic fibrosis with an increasing prevalence due to improved cystic fibrosis survival rates. The aims of this review are to highlight the key insights gained from monitoring the MCFC over 20 years, and to discuss the challenges and advantages of establishing such a cohort in a rare disease like cystic fibrosis.

METHODS

Adult people with cystic fibrosis were recruited from 2004 onward in Montreal, Canada, excluding those already diagnosed with cystic fibrosis-related diabetes. Clinical and biological results (including oral glucose tolerance tests) were recorded regularly.

RESULTS

Findings from the MCFC contributed to a better understanding of cystic fibrosis-related diabetes pathophysiology (in particular, the joint roles of reduced insulin secretion and added insulin resistance) and its relationship with lung function. Over the years, we observed a shift towards overweight and obesity among cystic fibrosis patients, along with improved lung function. This could be due to improved cystic fibrosis care and to the introduction of cystic fibrosis transmembrane conductance regulator modulators. We were also able to validate new, simplified screening modalities and management strategies (e.g. physical activity) for cystic fibrosis-related diabetes.

CONCLUSION

The MCFC has contributed to the understanding of cystic fibrosis-related diabetes and informed best practice guidelines. Future research will focus on how cystic fibrosis transmembrane conductance regulator modulators influence glycaemic control and cardiometabolic health in people with cystic fibrosis.

Peripheral Muscle Function and Body Composition in People With Cystic Fibrosis on Elexacaftor/Tezacaftor/Ivacaftor: A Cross-Sectional Single-Centre Study

BACKGROUND

People with cystic fibrosis (pwCF) often have multifactorial peripheral muscle abnormalities attributed to, for example, malnutrition, steroid use, altered redox balance and, potentially, CF-specific intrinsic alterations. Malnutrition in CF now includes an increasing prevalence of overweight and obesity, particularly in those receiving CF transmembrane conductance regulator (CFTR) modulator therapy (CFTRm). We aimed to characterise peripheral muscle function and body composition in pwCF on Elexacaftor/Tezacaftor/Ivacaftor (ETI) CFTRm, compared to healthy controls.

METHODS

Fifteen pwCF on ETI, and 15 healthy age- and sex-matched controls (CON), underwent whole-body dual-energy X-ray absorptiometry scans, and a comprehensive evaluation of peripheral muscle function. Tests included quadriceps maximal isometric force measurement, an intermittent isometric quadriceps fatiguing protocol, handgrip strength dynamometry, squat jump height assessment, and 1-min sit-to-stand testing.

RESULTS

No significant differences in quadriceps maximal isometric force (CON: 181.60 ± 92.90 Nm vs. CF: 146.15 ± 52.48 Nm, p = 0.21, d = 0.47), handgrip strength (CON: 34 ± 15 kg vs. CF: 31 ± 11 kg, p = 0.62, d = 0.18), peripheral muscle endurance, fatigue, or power were observed between the groups. Moreover, no significant differences in whole-body, trunk or limb lean mass, fat-free mass, fat mass, or whole-body bone mineral density were evident.

CONCLUSION

Comparable peripheral muscle mass and function has been demonstrated in pwCF on ETI, albeit a group with good lung function. Research is needed to confirm these findings longitudinally in pwCF, including those with more severe lung disease, who are less physically active, and have less optimal nutrition and exercise support.

Body composition changes and clinical outcomes in pediatric cystic fibrosis during 24 months of lumacaftor ivacaftor therapy based on real-world data

Clinical trials demonstrate the short-term efficacy of dual CFTR modulators, but long-term real-world data is limited. We aimed to investigate the effects of 24-month lumacaftor/ivacaftor (LUM/IVA) therapy in pediatric CF patients (pwCF). This observational study included pwCF homozygous for F508del mutation treated between 2021 and 2023. We report data for the first 24 months from therapy initiation. Variables were analyzed separately for ages 2-5, 6-11, and over 12. Data from 49 pwCF (median age: 9.3 years (5.5-14.2)) showed that ppFEV1 values after a transient increase at 12 months, decreased from 102% (82-114) at baseline to 87% (74-96) at 24 months. The decrease was more pronounced with higher initial ppFEV1. Median sweat chloride concentration decreased from 75 mmol/L (69-82) to 57 mmol/L (43-70) without any association with respiratory function change. Median BMI z-score increased from - 0.81 (- 1.37-0.49) to - 0.39 (- 0.88 to  - 0.04) (p = 0.288), and the proportion of underweight and overweight children decreased. Skeletal muscle mass remained stable, while fat mass significantly increased (p = 0.011). Fecal elastase levels improved, especially among younger patients. These findings underscore the potential benefits of early initiation of CFTR modulator therapy in pediatric CF patients, highlighting improvements in nutritional status and pancreatic function.

Low-Dose Ketone Monoester Administration in Adults with Cystic Fibrosis: A Pilot and Feasibility Study

INTRODUCTION

Cystic fibrosis transmembrane conductance regulator (CFTR) modulators have greatly improved outcomes in persons with CF (pwCF); however, there is still significant heterogeneity in clinical responses, particularly with regard to respiratory infection and inflammation. Exogenous administration of ketones has profound systemic anti-inflammatory effects and produces several nutrient-signaling and metabolic effects that may benefit multiple organ systems affected in pwCF. This pilot study was designed to determine the feasibility of administration of a ketone monoester (KME) to increase circulating D-beta hydroxybutyrate concentrations (D-βHB) and to improve subjective measures of CF-specific quality of life and markers of inflammation in serum and sputum in adults with CF.

METHODS

Fourteen participants receiving modulator therapy were randomized to receive either KME (n = 9) or placebo control (PC, n = 5) for 5-7 days during hospitalization for treatment of acute pulmonary exacerbation or as outpatients under standard care.

RESULTS

The KME was well tolerated, with only mild reports of gastrointestinal distress. D-βHB concentrations increased from 0.2 ± 0.1 mM to 1.6 ± 0.6 mM in the KME group compared to 0.2 ± 0.0 to 0.3 ± 0.1 in the PC group (p = 0.011) within 15 min following consumption and remained elevated, relative to baseline, for over 2 h. Pulmonary function was not altered after single- or short-term KME administration, but participants in the KME group self-reported higher subjective respiratory scores compared to PC in both cases (p = 0.031). Plasma inflammatory markers were not statistically different between groups following the short-term (5-7 d) intervention (p > 0.05). However, an exploratory analysis of plasma pre- and post-IL-6 concentrations was significant (p = 0.028) in the KME group but not PC. Sputum IFNγ (p = 0.057), IL-12p70 (p = 0.057), IL-1β (p = 0.100), IL-15 (p = 0.057), IL-1α (p = 0.114), and MPO (p = 0.133) were lower in the KME group compared to PC but did not achieve statistical significance.

CONCLUSIONS

With the emerging role of exogenous ketones as nutrient signaling molecules and mediators of metabolism, we showed that KME is well tolerated, increases circulating D-βHB concentrations, and produces outcomes that justify the need for large-scale clinical trials to investigate the role of KME on whole-body and tissue lipid accumulation and inflammation in pwCF.

Nutritional status in the era of highly effective CFTR modulators

Advances in cystic fibrosis (CF) diagnostics and therapeutics have led to improved health and longevity, including increased body weight and decreased malnutrition in people with CF. Highly effective CFTR modulator therapies (HEMT) are associated with increased weight through a variety of mechanisms, accelerating trends of overweight and obesity in the CF population. Higher body mass index (BMI) is associated with improved pulmonary function in CF, yet the incremental improvement at overweight and obese BMIs is not clear. Improvements in pulmonary health with increasing BMI are largely driven by increases in fat-free mass (FFM), and impact of HEMT on FFM is uncertain. While trends toward higher weight and BMI are generally seen as favorable in CF, the increased prevalence of overweight and obesity has raised concern for potential risk of traditional age- and obesity-related comorbidities. Such comorbidities, including impaired glucose tolerance, hypertension, cardiac disease, hyperlipidemia, fatty liver, colon cancer, and obstructive sleep apnea, may occur on top of pre-existing CF-related comorbidities. CF nutrition recommendations are evolving in the post-modulator era to more individualized approaches, in contrast to prior blanket high-fat, high-calorie prescriptions for all. Ultimately, it will be essential to redefine goals for optimal weight and nutritional status to allow for holistic health and aging in people with CF.

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.

Impact of CFTR modulator therapy on body composition as assessed by thoracic computed tomography: A follow-up study

OBJECTIVE

Treatment with cystic fibrosis transmembrane conductance regulator (CFTR) modulators in individuals with cystic fibrosis (CF) has brought a significant change in forced expiratory volume in 1 second (FEV1) and clinical parameters. However, it also results in weight gain. The aim of our study is to evaluate the effect of CFTR modulator treatment on body composition, measured by computed tomography (CT).

METHODS

Adult subjects with CF under follow-up at La Princesa University Hospital were recruited. All of them were on elexacaftor-tezacaftor-ivacaftor (ELX/TEZ/IVA) treatment. Body composition analysis was conducted using CT scans and an open-source software. The results were then compared with bioimpedance estimations, as well as other clinical and spirometry data.

RESULTS

Our sample consisted of 26 adult subjects. The fat mass compartments on CT scans correlated with similar compartments on bioimpedance, and normal-density muscle mass exhibited a strong correlation with phase angle. Higher levels of very low-density muscle prior to treatment were associated with lower final FEV1 and less improvement in FEV1 after therapy. We observed an increase in total body area (P < 0.001), driven by increases in total fat mass (P < 0.001), subcutaneous fat (P < 0.001), visceral fat (P = 0.002), and intermuscular fat (P = 0.022). The only muscle compartment that showed an increase after treatment was very low-density muscle (P = 0.032).

CONCLUSIONS

CT scans represent an opportunity to assess body composition on CF. Combination treatment with CFTR modulators, leads to an improvement in FEV1 and to an increase in body mass in all compartments primarily at the expense of fat mass.

Malnutrition, sarcopenia, and frailty assessment in pediatric transplantation

Nutrition assessment can be challenging in children with end-stage organ disease and in those requiring an organ transplant. The effect of poor nutrition status can exert long-lasting effects on children with end-stage organ disease requiring transplantation. Malnutrition, sarcopenia, and frailty are conditions that require provision of optimal nutrition to prevent or support the treatment of these conditions. Unfortunately, the literature on the assessment of malnutrition, sarcopenia, and frailty in pediatric end-stage organ disease is scarce, thus leading to confusion on how to effectively identify them. Recently, the addition of a variety of validated nutrition and functional assessment techniques has assisted with appropriate assessment of these conditions. The objective of this narrative review is to provide an overview of the current literature for pediatric assessment of malnutrition, sarcopenia, and frailty in the setting of solid organ transplantation and provide practicing nutrition clinicians a solid foundation for learning how to effectively assess these conditions with the current literature available.