Influence of pre-diabetic and pancreatic exocrine states on pulmonary and nutritional status in adults with Cystic Fibrosis

Early glucose abnormalities revealed by continuous glucose monitoring associate with lung function decline in cystic fibrosis: A five-year prospective study

BACKGROUND

Cystic fibrosis related diabetes (CFRD) is commonly associated with declining lung function and nutritional status. We aimed to evaluate the pulmonary impact of early glucose abnormalities by using 2-h standard oral glucose tolerance testing (OGTT) and continuous glucose monitoring (CGM) in people with cystic fibrosis (PwCF).

METHODS

PwCF aged ≥10 years old without known CFRD were included in a five-year prospective multicentre study. Annual evaluation of nutritional status, lung function, OGTT and CGM was set up. Associations between annual rate changes (Δ) in lung function, ΔFEV1 (forced expiratory volume in 1 s) percentage predicted (pp) and ΔFVC (forced vital capacity) pp., and annual rate changes in OGTT or CGM variables were estimated with a mixed model with a random effect for subject.

RESULTS

From 2009 to 2016, 112 PwCF (age: 21 ± 11 years, BMI (body mass index) z-score: -0.55 ± 1.09, FEV1pp: 77 ± 24 %, 2-h OGTT glucose: 122 ± 44 mg/dL, AUC (area under curve) >140 mg/dL: 1 mg/dL/day (0.2, 3.0) were included. A total of 428 OGTTs and 480 CGMs were collected. The participants presented annual decline of FVCpp and FEV1pp at -1.0 % per year (-1.6, -0.4), p < 0.001 and - 1.9 % per year (-2.5, -1.3), p < 0.001 respectively without change in BMI z-score during the study. Variation of two-hour OGTT glucose was not associated with declining lung function, as measured by ΔFEV1pp (p = 0.94) and ΔFVCpp (p = 0.90). Among CGM variables, only increase in AUC >140 mg/dL between two annual visits was associated with a decrease in ΔFVCpp (p < 0.05) and ΔFEV1pp (p < 0.05).

CONCLUSIONS

This prospective study supports the fact that early glucose abnormalities revealed by CGM predict pulmonary function decline in PwCF, while 2-h standard OGTT glucose is not associated with pulmonary impairment.

Association between cystic fibrosis transmembrane regulator genotype and clinical outcomes, glucose homeostasis indices and CF-related diabetes risk in adults with CF

People living with cystic fibrosis (pwCF) homozygous for F508del present more severe phenotypes. PwCF with compound heterozygous genotypes F508del /A455E and F508del /L206W may have milder cystic fibrosis (CF) phenotypes. We compared F508del homozygotes and common compound heterozygotes (F508del and a second pathogenic variant) in adult patients. Nutritional, pulmonary function and glucose homeostasis indices data were collected from the prospective Montreal CF cohort. Two-hundred and three adults with CF having at least one F508del variant were included. Individuals were divided into subgroups: homozygous F508del/F508del (n=149); F508del/621+1G>T (n=17); F508del/711+1G>T (n=11); F508del/A455E (n=12); and F508del/L206W (n=14). Subgroups with the F508del/L206W and F508del/A455E had a lower proportion with pancreatic exocrine insufficiency (p<0.0001), a higher fat mass (p<0.0001), and lower glucose area under the curve (AUC) (p=0.027). The F508del/L206W subgroup had significantly higher insulin secretion (AUC; p=0.027) and body mass index (p<0.001). Pulmonary function (FEV1) was significantly higher for the F508del/L206W subgroup (p<0.0001). Over a median of 7.37 years, the risk of developing CFRD in 141 patients was similar between groups. PwCF with heterozygous F508del/L206W and F508del/A455E tended to have pancreatic exocrine sufficiency, better nutritional status, improved pulmonary function and better diabetogenic indices, but this does not translate into lower risk of CF-related Diabetes.

ESPEN-ESPGHAN-ECFS guideline on nutrition care for cystic fibrosis

BACKGROUND

Nutritional status is paramount in Cystic Fibrosis (CF) and is directly correlated with morbidity and mortality. The first ESPEN-ESPGHAN-ECFS guidelines on nutrition care for infants, children, and adults with CF were published in 2016. An update to these guidelines is presented.

METHODS

The study was developed by an international multidisciplinary working group in accordance with officially accepted standards. Literature since 2016 was reviewed, PICO questions were discussed and the GRADE system was utilized. Statements were discussed and submitted for on-line voting by the Working Group and by all ESPEN members.

RESULTS

The Working Group updated the nutritional guidelines including assessment and management at all ages. Supplementation of vitamins and pancreatic enzymes remains largely the same. There are expanded chapters on pregnancy, CF-related liver disease, and CF-related diabetes, bone disease, nutritional and mineral supplements, and probiotics. There are new chapters on nutrition with highly effective modulator therapies and nutrition after organ transplantation.

Nutritional management of people living with cystic fibrosis throughout life and disease continuum: Changing times, new challenges

Cystic fibrosis (CF) is a genetic disease caused by mutations in the gene encoding for the ion channel cystic fibrosis transmembrane conductance regulator (CFTR). The management of CF disease has evolved in recent decades from treating downstream disease manifestations affecting the airways, the lungs and the gastrointestinal system to addressing the CFTR gene defect. The advent of CFTR modulators, which correct the functionality of the defective CFTR, contributes to reshaping the landscape of CF demographics, prognosis and therapies, including nutritional management. A spectrum of clinical manifestations is emerging within the same patient population where undernutrition and nutritional deficiencies coexist with excessive weight gain and metabolic derangements. Such contrasting presentations challenge current practices, require adjustments to traditional approaches, and involve more individualised interventions. This narrative review examines the current state of knowledge on the nutritional management of people living with cystic fibrosis from early life to adulthood in the era of CFTR modulation.

A glycosylated hemoglobin A1c above 6% (42 mmol/mol) is associated with a high risk of developing Cystic Fibrosis-Related Diabetes and a lower probability of weight gain in both adults and children with Cystic Fibrosis

OBJECTIVES

The classical glycosylated hemoglobin A1c threshold of 6.5% is an insensitive screening test for cystic fibrosis-related diabetes (CFRD). We sought to identify CF-specific A1C thresholds associated with 1) risk of progression to CFRD and 2) changes in body mass index (BMI) and forced expiratory volume (FEV1).

METHODS

We studied the cross sectional and longitudinal associations between A1c, BMI, and FEV1 in 2 cohorts of 223 children (followed for up to 8 years) and 289 adults (followed for a mean of 7.5 ± 4.3 years) with CF but without diabetes at baseline and undergoing regular assessments including Oral Glucose Tolerance Test (OGTT).

RESULTS

For the onset of OGTT-defined CFRD optimal A1c threshold was 5.9% in adults (sensitivity: 67% and specificity: 71%) and 5.7% for children (sensitivity: 60% and specificity: 47%). Kaplan-Meier analysis of progression to CFRD according to baseline A1C showed increased the risk of developing CFRD for A1c ≥ 6.0% in adults (P = 0.002) and ≥ 5.5% in children (p = 0.012). Temporal changes in BMI and FEV1 according to baseline A1C in adults were assessed with a linear mixed-effect model, BMI significantly increased over time in subjects with a baseline A1c < 6%, but those with a A1C ≥ 6.0% gained significantly less weight over time (P = 0.05). There was no difference in FEV1 according to baseline A1c category.

CONCLUSION

An A1C above 6% may be associated with a high risk of developing CFRD and a lower probability of weight gain in both adults and children with CF.

Continuous Glucose Monitoring as an Additional Tool in Early Cystic Fibrosis-Related Diabetes Monitoring and in Evaluation of Short-Term Sitagliptin Response

Cystic fibrosis-related diabetes (CFRD) is a complication associated with a negative prognosis in patients with cystic fibrosis (CF). Although the oral glucose tolerance test (OGTT) is the widely recommended screening test for CFRD diagnosis, continuous glucose monitoring (CGM) is increasingly considered a useful and easy-to-perform test for diagnosis and follow-up in clinical practice. Regarding CFRD treatment, although insulin is the classic approved pharmacological option, incretins could also be a helpful alternative in early stages. CGM could be also a useful tool to measure the early response to this therapy.

METHODS

We studied 25 CF patients with abnormal OGTT results and compared glucose and insulin levels during the OGTTs with CGM results as a tool for early CFRD diagnosis. In addition, we evaluated glycaemic control with CGM before and after treatment with sitagliptin.

RESULTS

A correlation was found between lower plasma insulin levels during the OGTTs and higher average sensor glucose (p = 0.009) and hyperglycaemic excursions (p = 0.017). The CGM data on sitagliptin treatment (n = 25) showed an average glycaemic improvement from 124.2 to 117.2 mg/dL (p = 0.002) with a 5.6-point standard deviation of glucose decrease (p < 0.001). Hyperglycaemic excursions ≥200 mg/dL diminished 57.1% (p = 0.021). Both time in range and time above 180 mg/dL improved during treatment (p = 0.036 and p = 0.006, respectively).

CONCLUSION

CGM is a useful tool that offers valuable information for both the diagnosis and the management of CFRD. Lower plasma insulin levels during OGTTs are associated with a poor ambulatory glucose profile in CGM. Sitagliptin could play an important role in the treatment of the early stages of CFRD.

Cystic Fibrosis-Related Diabetes Workshop: Research Priorities Spanning Disease Pathophysiology, Diagnosis, and Outcomes

Cystic fibrosis (CF) is a recessive disorder arising from mutations in the gene encoding the cystic fibrosis transmembrane conductance regulator (CFTR) protein. CFTR is expressed in numerous tissues, with high expression in the airways, small and large intestine, pancreatic and hepatobiliary ducts, and male reproductive tract. CFTR loss in these tissues disrupts regulation of salt, bicarbonate, and water balance across their epithelia, resulting in a systemic disorder with progressive organ dysfunction and damage. Pancreatic exocrine damage ultimately manifests as pancreatic exocrine insufficiency that begins as early as infancy. Pancreatic remodeling accompanies this early damage, during which abnormal glucose tolerance can be observed in toddlers. With increasing age, however, insulin secretion defects progress such that CF-related diabetes (CFRD) occurs in 20% of teens and up to half of adults with CF. The relevance of CFRD is highlighted by its association with increased morbidity, mortality, and patient burden. While clinical research on CFRD has greatly assisted in the care of individuals with CFRD, key knowledge gaps on CFRD pathogenesis remain. Furthermore, the wide use of CFTR modulators to restore CFTR activity is changing the CFRD clinical landscape and the field's understanding of CFRD pathogenesis. For these reasons, the National Institute of Diabetes and Digestive and Kidney Diseases and the Cystic Fibrosis Foundation sponsored a CFRD Scientific Workshop, 23-25 June 2021, to define knowledge gaps and needed research areas. This article describes the findings from this workshop and plots a path for CFRD research that is needed over the next decade.

Cystic Fibrosis-Related Diabetes Workshop: Research Priorities Spanning Disease Pathophysiology, Diagnosis, and Outcomes

Cystic fibrosis (CF) is a recessive disorder arising from mutations in the gene encoding the cystic fibrosis transmembrane conductance regulator (CFTR) protein. CFTR is expressed in numerous tissues, with high expression in the airways, small and large intestine, pancreatic and hepatobiliary ducts, and male reproductive tract. CFTR loss in these tissues disrupts regulation of salt, bicarbonate, and water balance across their epithelia, resulting in a systemic disorder with progressive organ dysfunction and damage. Pancreatic exocrine damage ultimately manifests as pancreatic exocrine insufficiency that begins as early as infancy. Pancreatic remodeling accompanies this early damage, during which abnormal glucose tolerance can be observed in toddlers. With increasing age, however, insulin secretion defects progress such that CF-related diabetes (CFRD) occurs in 20% of teens and up to half of adults with CF. The relevance of CFRD is highlighted by its association with increased morbidity, mortality, and patient burden. While clinical research on CFRD has greatly assisted in the care of individuals with CFRD, key knowledge gaps on CFRD pathogenesis remain. Furthermore, the wide use of CFTR modulators to restore CFTR activity is changing the CFRD clinical landscape and the field's understanding of CFRD pathogenesis. For these reasons, the National Institute of Diabetes and Digestive and Kidney Diseases and the Cystic Fibrosis Foundation sponsored a CFRD Scientific Workshop, 23-25 June 2021, to define knowledge gaps and needed research areas. This article describes the findings from this workshop and plots a path for CFRD research that is needed over the next decade.

Canadian Cystic Fibrosis-related Diabetes Clinical Practice Survey: Analysis of Current Practices and Gaps in Clinical Care

OBJECTIVES

Our aim in this study was to identify challenges and gaps in Canadian practices in screening, diagnosis and treatment of cystic fibrosis-related diabetes (CFRD), with the goal of informing a Canadian-specific guideline for CFRD.

METHODS

We conducted an online survey of health-care professionals (97 physicians and 44 allied health professionals) who care for people living with CF (pwCF) and/or CFRD (pwCFRD).

RESULTS

Most pediatric centres followed <10 pwCFRD and adult centres followed >10 pwCFRD. Children with CFRD are usually followed at a separate diabetes clinic, whereas adults with CFRD may be followed by respirologists, nurse practitioners or endocrinologists in CF clinic or in a separate diabetes clinic. Less than 25% of pwCF had access to an endocrinologist with a special interest or expertise in CFRD. Many centres perform screening oral glucose tolerance testing with fasting and 2-hour time-points. Respondents, especially those working with adults, also indicate use of additional tests for screening not currently recommended in CFRD guidelines. Pediatric practitioners tend to only use insulin to manage CFRD, whereas adult practitioners are more likely to use repaglinide as an alternative to insulin.

CONCLUSIONS

Access to specialized CFRD care may be a challenge for pwCFRD in Canada. There appears to be wide heterogeneity of CFRD care organization, screening and treatment among health-care providers caring for pwCF and/or CFRD across Canada. Practitioners working with adult pwCF are less likely to adhere to current clinical practice guidelines than practitioners working with children.

Glycemic indices at night measured by CGM are predictive for a lower pulmonary function in adults but not in children with cystic fibrosis

INTRODUCTION

In patients with cystic fibrosis (CF), it is still unclear to which extent glucose abnormalities - preceding the diagnosis of cystic fibrosis related diabetes (CFRD) - are associated with pulmonary and nutritional outcome parameters. This study related circadian glycemic patterns to clinical outcomes in a group of CF patients not previously diagnosed with diabetes.

METHODS

Continuous glucose monitoring (CGM) readings (7 days) of 47 CF patients (26 children, 21 adults) with an impaired oral glucose tolerance test (OGTT) (n = 25) and/or increased Hb1Ac (> 5.5%) were analyzed. Biometric, pulmonary function and clinical parameters were retrospectively collected over a period of 1 year before (T-1) and 1 year after (T + 1) CGM (T0).

RESULTS

96% (45/47) of CGM readings showed glucose values > 140 mg/dL ≥ 4.5% of the time and at least one ≥ 200 mg/dL. In the pediatric cohort, no significant associations were found between CGM parameters and pulmonary and nutritional outcome parameters. In the adult cohort, an area under the curve (AUC) > 140 mg/dL and%-time > 140 mg/dL during the night were associated with a lower forced expiratory volume in 1 s (FEV1)% predicted (pp) at time of evaluation but not with change in FEV1pp.

CONCLUSION

This is the first study reporting the circadian glycemic pattern in children and adults at risk for CFRD. In the adult cohort an association between detection of abnormal glucose exposure and a lower FEV1pp was found. Our results support continued screening for glucose intolerance in patients with CF.

Cystic Fibrosis-Related Diabetes: Clinical approach and knowledge gaps

Cystic Fibrosis-Related Diabetes (CFRD) is a unique type of diabetes mellitus that shares some features with both type 1 and type 2 diabetes. Yet, its distinguishing feature of acute pulmonary complications associated with hyperglycemia and the catabolic metabolism associated with a relative insulin deficiency poses challenges to the application of traditional definitions and treatments for diabetes mellitus. People with CF (pwCF) undergo rigorous annual screening starting at age 10, a process that is challenging for patients and limited by sensitivity, specificity, and reproducibility. As pwCF continue to live longer, over 50% are expected to develop CFRD over their lifetime, including up to 20% of adolescents. Increasing numbers of people with CFRD will make this disease increasingly relevant to diabetes practitioners. Evidence-guided practice in CFRD care is limited by small and short studies. Our current understanding of CFRD may change significantly with the recent introduction of CF Transmembrane Regulator (CFTR) modulator medications. This review will explore current challenges in the diagnosis and management of CFRD, specifically highlighting knowledge gaps in the pathophysiology of CFRD, optimal screening methods, priorities for research and provide guidance with regards to screening, diagnosis, and treatment.

Clinical practice versus guidelines for the screening of cystic fibrosis-related diabetes: A French survey from the 47 centers

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A French survey of clinical practices with the participation of all CF centers.

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Most CF centers used OGTT and CGM for CFRD screening.

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OGTT was conducted before 10 years of age in 73% of pediatric centers.

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One third of centers propose OGTT to sufficient pancreatic patients.

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69% of centers realized CGM in case of glucose tolerance abnormalities at OGTT.

This study aimed to analyze clinical practices concerning cystic fibrosis-related diabetes (CFRD) screening in France. A web-based questionnaire was distributed between December 1, 2020 and January 31, 2021 among 47 cystic fibrosis centers including pediatric, adult, and mixed units. In accordance with guidelines, 92.8% of CF centers performed annual oral glucose tolerance tests (OGTT). Overall, 86.3% of CF centers performed 1- and 2-hour blood glucose determinations following OGTT. The OGTT was conducted before 10 years of age in 73% of pediatric centers. Continuous glucose monitoring (CGM) and laboratory glycated hemoglobin were employed for CFRD screening in 86.5% and 50% of centers, respectively. CGM was carried out in 69% of centers after glucose tolerance abnormalities had been detected in OGTT. Most CF centers used OGTT and CGM for CFRD screening. Studies are required to assess CGM usefulness as a validated tool in CFRD screening.

The Potential Causes of Cystic Fibrosis-Related Diabetes

Cystic fibrosis (CF) is a genetic disease caused by mutations in the cystic fibrosis transmembrane conductance regulator gene (CFTR). Cystic fibrosis-related diabetes (CFRD) is the most common comorbidity, affecting more than 50% of adult CF patients. Despite this high prevalence, the etiology of CFRD remains incompletely understood. Studies in young CF children show pancreatic islet disorganization, abnormal glucose tolerance, and delayed first-phase insulin secretion suggesting that islet dysfunction is an early feature of CF. Since insulin-producing pancreatic β-cells express very low levels of CFTR, CFRD likely results from β-cell extrinsic factors. In the vicinity of β-cells, CFTR is expressed in both the exocrine pancreas and the immune system. In the exocrine pancreas, CFTR mutations lead to the obstruction of the pancreatic ductal canal, inflammation, and immune cell infiltration, ultimately causing the destruction of the exocrine pancreas and remodeling of islets. Both inflammation and ductal cells have a direct effect on insulin secretion and could participate in CFRD development. CFTR mutations are also associated with inflammatory responses and excessive cytokine production by various immune cells, which infiltrate the pancreas and exert a negative impact on insulin secretion, causing dysregulation of glucose homeostasis in CF adults. In addition, the function of macrophages in shaping pancreatic islet development may be impaired by CFTR mutations, further contributing to the pancreatic islet structural defects as well as impaired first-phase insulin secretion observed in very young children. This review discusses the different factors that may contribute to CFRD.