Distribution of OGTT-Related Variables in Patients with Cystic Fibrosis from Puberty to Adulthood: An Italian Multicenter Study.

BACKGROUND: Insulin secretion and glucose tolerance is annually assessed in patients with cystic fibrosis (PwCF) through oral glucose tolerance tests (OGTTs) as a screening measure for cystic fibrosis-related diabetes. We aimed to describe the distribution and provide reference quartiles of OGTT-related variables in the Italian cystic fibrosis population. METHODS: Cross-sectional study of PwCF receiving care in three Italian cystic fibrosis centers of excellence, from 2016 to 2020. We performed a modified 2-h OGTT protocol (1.75 g/kg, maximum 75 g), sampling at baseline and at 30-min intervals, analyzing plasma glucose, serum insulin, and C-peptide. The modified OGTT allowed for the modeling of ß cell function. For all variables, multivariable quantile regression was performed to estimate the median, the 25th, and 75th percentiles, with age, sex, and pancreatic insufficiency as predictors. RESULTS: We have quantified the deterioration of glucose tolerance and insulin secretion with age according to sex and pancreatic insufficiency, highlighting a deviation from linearity both for patients <10 years and >35 years of age. CONCLUSIONS: References of OGTT variables for PwCF provide a necessary tool to not only identify patients at risk for CFRD or other cystic fibrosis-related complications, but also to evaluate the effects of promising pharmacological therapies.

Prepuberal insulin secretory indices are long-term predictors of short adult stature in cystic fibrosis.

Objective: Diabetes is a frequent comorbidity in cystic fibrosis (CF), related to multiple unfavorable outcomes. During the progression of ß-cell dysfunction to diabetes, insulin deficiency could possibly reduce the anabolic support to grow even in the absence of significant glycemic derangements. To test this hypothesis, we evaluated whether prepuberal insulin secretory indices are independent predictors of adult height. Design: Observational cohort study. Research design and methods: A longitudinal analysis of 66 CF patients (33 females) from an ongoing cohort received at prepuberal age (median age of 12 years) modified 3-h oral glucose tolerance tests with 30-min insulin and C-peptide sampling, modeling of insulin secretory and sensitivity parameters, anthropometric evaluation. The latter was repeated when adults after a median follow-up of 9 years. Results: In alternative models, we found a positive association with either basal insulin secretion (mean 0.22, 95% CI 0.01, 0.44 z-scores) or prepuberal ß-cell glucose sensitivity (mean 0.23, 95% CI 0.00, 0.46 z-scores) and adult height, while total insulin secretion was negatively related to adult height (mean -0.36, 95% CI -0.57, -0.15 z-scores or mean -0.42, 95% CI -0.69, -0.16 z-scores, respectively). The high total insulin secretion of low adult height patients was mainly due to late (>60 min) secretion and was associated with a worse glucose response during OGTT. Conclusions: Abnormal insulin secretion associated with high glucose response during OGTT predicts a decrease in adult height z-score. Our results suggest that insulin secretory defects in CF affect growth prior to the development of fasting hyperglycemia.

The preclinical discovery and development of the combination of ivacaftor + tezacaftor used to treat cystic fibrosis.

INTRODUCTION: Cystic Fibrosis (CF) is caused by mutations in the Cystic Fibrosis Transmembrane Conductance Regulator (CFTR) gene. The most common mutation, F508del, induces protein misprocessing and loss of CFTR function. The discovery through in vitro studies of the CFTR correctors (i.e. lumacaftor, tezacaftor) that partially rescue the misprocessing of F508del-CFTR with the potentiator ivacaftor is promising in giving an unprecedented clinical benefit in affected patients. AREAS COVERED: Online databases were searched using key phrases for CF and CFTR modulators. Tezacaftor-ivacaftor treatment has proved to be safer than lumacaftor-ivacaftor, although clinical efficacy is similar. Further clinical efficacy has ensued with the introduction of triple therapy, i.e. applying second-generation correctors, such as VX-569 and VX-445 (elexacaftor) to tezacaftor-ivacaftor. The triple combinations will herald the availability of etiologic therapies for patients for whom no CFTR modulators are currently applied (i.e. F508del/minimal function mutations) and enhance CFTR modulator therapy for patients homozygous for F508del. EXPERT OPINION: CF patient-derived tissue models are being explored to determine donor-specific response to current approved and future novel CFTR modulators for F508del and other rare mutations. The discovery and validation of biomarkers of CFTR modulation will complement these studies in the long term and in real-life world.

No gender differences in growth patterns in a cohort of children with cystic fibrosis born between 1986 and 1995.

BACKGROUND & AIMS: A higher mortality rate at young ages has been reported in cystic fibrosis (CF) girls compared to boys. The reasons of this gap remain unclear but may be related to a different evolution of the disease, in terms of growth and lung function throughout childhood and adolescence. This study aimed at investigating gender differences in growth patterns in a cohort of children with CF through a longitudinal study, and as secondary objectives, to evaluate gender differences in forced expiratory volume in one second (FEV1) trend and transplant-free survival. METHODS: We performed an historical cohort study of 203 CF patients born between 1986 and 1995. Weight and height were recorded from the time of CF diagnosis to the age of 18 years. Generalized estimated equations were used to evaluate the effect of gender on changes in z-score of BMI-for-age and z-score of height-for-age and FEV1. Transplant-free survival to age 18 was computed by the Kaplan-Meier estimator. RESULTS: Girls did not show a worse growth pattern as compared to boys. The odds of being underweight [Odds Ratio (OR) for girls: 0.85, 95% CI: 0.51; 1.39] or stunted [OR for girls: 0.79, 95% CI: 0.42; 1.49] were not significantly different between genders. FEV1 trend was also similar in boys and girls, as well as the probability of surviving to age 18 without receiving lung transplantation (boys: 0.88, 95% CI: 0.82-0.95, girls: 0.92, 0.87-0.98, P = 0.26). CONCLUSIONS: In a cohort of children with CF born between 1986 and 1995, no gender differences in growth patterns were observed. This finding suggests that CF girls and boys have benefited equally from the advances in treatments that have occurred over the last three decades.

Clinical expression of cystic fibrosis in a large cohort of Italian siblings.

BACKGROUND: A clinical heterogeneity was reported in patients with Cystic Fibrosis (CF) with the same CFTR genotype and between siblings with CF. METHODS: We investigated all clinical aspects in a cohort of 101 pairs of siblings with CF (including 6 triplets) followed since diagnosis. RESULTS: Severe lung disease had a 22.2% concordance in sib-pairs, occurred early and the FEV1% at 12 years was predictive of the severity of lung disease in the adulthood. Similarly, CF liver disease occurred early (median: 15 years) and showed a concordance of 27.8% in sib-pairs suggesting a scarce contribution of genetic factors; in fact, only 2/15 patients with liver disease in discordant sib-pairs had a deficiency of alpha-1-antitrypsin (a known modifier gene of CF liver phenotype). CF related diabetes was found in 22 pairs (in 6 in both the siblings). It occurred later (median: 32.5 years) and is strongly associated with liver disease. Colonization by P. aeruginosa and nasal polyposis that required surgery had a concordance > 50% in sib-pairs and were poorly correlated to other clinical parameters. The pancreatic status was highly concordant in pairs of siblings (i.e., 95.1%) but a different pancreatic status was observed in patients with the same CFTR mutations. This suggests a close relationship of the pancreatic status with the "whole" CFTR genotype, including mutations in regulatory regions that may modulate the levels of CFTR expression. Finally, a severe course of CF was evident in a number of patients with pancreatic sufficiency. CONCLUSIONS: Physicians involved in care of patients with CF and in genetic counseling must be aware of the clinical heterogeneity of CF even in sib-pairs that, at the state of the art, is difficult to explain.

Accuracy of Prediction Formulae for the Assessment of Resting Energy Expenditure in Hospitalized Children.

BACKGROUND AND AIM: The resting energy expenditure (REE) of ill children is commonly estimated from prediction formulae developed in healthy children. The aim of the present study was to evaluate the accuracy of commonly employed REE prediction formulae versus indirect calorimetry in hospitalized children. METHODS: We performed a cross-sectional study of 236 infants, children, and adolescents consecutively admitted to the Intermediate Care, Nephrology, Intensive Care, Emergency, and Cystic Fibrosis Units of the De Marchi Pediatric Hospital (Milan, Italy) between September 2013 and March 2015. REE was measured by indirect calorimetry and estimated using the World Health Organization (WHO), Harris-Benedict, Schofield, and Oxford formulae. RESULTS: The mean (standard deviation) difference between the estimated and measured REE was: -1 (234) kcal/day for the WHO formula; 82 (286) kcal/day for the Harris-Benedict formula; 2 (215) kcal/day for the Schofield-weight formula; -2 (214) kcal/day for the Schofield-weight and height formula; and -5 (221) kcal/day for the Oxford formula. Even though the WHO, Schofield, and Oxford formulae gave accurate estimates of REE at the population level (small mean bias), all the formulae were not accurate enough to be employed at the individual level (large SD of bias). CONCLUSIONS: The WHO, Harris-Benedict, Schofield, and Oxford formulae should not be used to estimate REE in hospitalized children.

Streptococcus pneumoniae oropharyngeal colonization in children and adolescents with cystic fibrosis.

BACKGROUND: This study was designed to evaluate Streptococcus pneumoniae (S. pneumoniae) carriage rates in patients with cystic fibrosis (CF). METHODS: An oropharyngeal swab was obtained from 212 CF children and adolescents enrolled during routine clinical visits. DNA from swabs was analyzed by real-time polymerase chain reaction. RESULTS: A total of 42 (19.8%) CF patients (mean age±standard deviation [SD], 12.0±3.3years) were colonized by S. pneumoniae. Carriage was more common in younger patients and tended to decline with age. Administration of systemic and/or inhaled antibiotics in the last 3months significantly correlated with a reduced carrier state [odds ratio (OR) 0.23, 95% confidence interval (CI) 0.07-0.69, and OR 0.26, 95% CI 0.08-0.77, respectively]. Vitamin D serum levels ≥30ng/mL were less common in carriers than that in non-carriers (OR 0.35; 95% CI 0.08-1.49). In both the vaccinated and unvaccinated subjects, serotypes 19F, 5, 4, and 9V were the most commonly carried serotypes. CONCLUSIONS: S. pneumoniae carrier state of school-age children and adolescents with CF is more prevalent than previously thought, and pneumococcal conjugate vaccination administered in the first year of life does not reduce the risk of re-colonization in later childhood and adolescence.

Estimating body composition from skinfold thicknesses and bioelectrical impedance analysis in cystic fibrosis patients.

BACKGROUND: The accuracy of body composition estimates based on skinfold thickness measurements and bioelectrical impedance analysis (BIA) is not yet adequately explored in cystic fibrosis (CF). Using DXA as reference method we verified the accuracy of these techniques and identified predictors of body composition specific for CF. METHODS: One hundred forty-two CF patients (age range: 8-31 years) underwent a DXA scan. Body fat percentage (BF%) was estimated from skinfolds, while fat free mass (FFM) from single-frequency 50 kHz BIA. RESULTS: Bland-Altman analysis showed poor intra-individual agreement between body composition data provided by DXA and BF% estimated from skinfolds or FFM estimated from BIA. The skinfolds of the upper arm were better predictors of BF% than BMI, while compared to other BIA measurements the best predictor of FFM was the R-index (Height(2)/Resistance). CONCLUSIONS: Due to poor accuracy at individual level, the estimates of body composition obtained from these techniques cannot be part of the standard nutritional assessment of CF patients until reliable CF-specific equations will become available. BMI has limited value in predicting body fatness in CF patients and should be used in combination with other predictors. Skinfolds of the upper arm and R-index are strongly related to BF% and FFM and should be tested in a large CF population to develop specific predictive equations.

Human rhinovirus infection in children with cystic fibrosis.

Nasopharyngeal swabs obtained from 78 pediatric patients with cystic fibrosis (CF), including 47 with acute pulmonary exacerbation and 31 in a stable clinical condition, were evaluated for 17 respiratory viruses. Human rhinovirus (HRV) was the most frequently detected virus in patients with pulmonary exacerbation and in those who were clinically stable (21.3% vs. 12.9%; P = 0.52). HRV-A was the main RV detected in patients with pulmonary exacerbations. However, no prevalence of particular HRV-A subtypes was found. This study highlights that RV is frequently found in the respiratory secretions of patients with CF and the impact of HRV-A appears higher than that of the other HRV types in patients with pulmonary exacerbations.

Recurrent pulmonary exacerbations are associated with low fat free mass and low bone mineral density in young adults with cystic fibrosis.

BACKGROUND: In cystic fibrosis (CF), systemic inflammation and pulmonary infections sustain a catabolic response leading to fat free mass (FFM) depletion. OBJECTIVES: To investigate the association between recurrent pulmonary exacerbations and alteration in body composition in young adults with CF. METHODS: In a retrospective study we collected body composition data, obtained by DXA scan, on 85 young adults with CF (44 males, mean age 23±4years). Whole body and appendicular FFM were divided by height squared to obtain FFM indices (FFMI). Number of pulmonary exacerbations occurred in the year preceding DXA scan were computed and patients were defined as frequent exacerbators if they experienced more than 2 pulmonary exacerbations/year. Body composition data were compared between frequent and infrequent exacerbators. RESULTS: Male patients classified as frequent exacerbators had lower total body bone mineral density (Z-score -1.44±1.22 vs. -0.66±0.92, P=0.033), whole body FFMI (18.0±1.9kg/m(2) vs. 19.3±1.4kg/m(2), P=0.024) and appendicular FFMI (7.8±1.0kg/m(2) vs. 8.8±0.8kg/m(2)P=0.004) compared to infrequent exacerbators. The reduced FFM found in frequent exacerbators was not uniformly distributed and involved mainly appendicular FFM (mean difference: -11% compared to infrequent exacerbators, P=0.016), whereas trunk FFM was not significantly affected by pulmonary exacerbations (mean difference -3% compared to infrequent exacerbators, P=0.34). These differences were not found in female patients. CONCLUSIONS: Recurrent pulmonary exacerbations are associated with reduced appendicular FFM and bone mineral density in young male adults with CF. The gender-dependent relationship between pulmonary exacerbations and body composition alteration needs to be further investigated.