Diabetes in cystic fibrosis: multicenter screening results based on current guidelines

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.

Delayed glucose peak and elevated 1-hour glucose on the oral glucose tolerance test identify youth with cystic fibrosis with lower oral disposition index

BACKGROUND

Alternate methods for characterizing oral glucose tolerance tests (OGTT) have emerged as superior to the 2-hour glucose in identifying individuals at risk for type 2 diabetes. The significance of these methods in cystic fibrosis (CF) is unclear. We compared 3 OGTT classifications in youth with CF: 1. curve shape (biphasic vs. monophasic), 2. time to glucose peak (≤30minutes vs. >30minutes), 3. 1-hour glucose (1hG) <155 mg/dL vs. ≥155 mg/dL to traditional OGTT criteria to determine which best identifies lower oral disposition index (oDI), pulmonary function, and body mass index (BMI).

METHODS

Youth 10-18 years with CF, not on insulin, underwent 2-hour OGTT. Glucoses were classified by traditional criteria and 3 alternate methods as normal (biphasic curve, glucose peak ≤30minutes, and/or 1hG <155 mg/dL) or abnormal (monophasic curve, glucose peak >30minutes, and/or 1hG ≥155 mg/dL). oDI was calculated [1/fasting insulin*(ΔInsulin_0-30 min/ΔGlucose_0-30 min)]. Mean oDI, BMI, forced expiratory volume in 1 second (FEV1), and forced vital capacity (FVC) were compared by OGTT classification.

RESULTS

Fifty-two youth with CF participated (mean±SD age 13±4years; 37% male; BMI z-score 0.0±0.8; FEV1 88±16.3%; FVC 97±14.8%). Late time to peak glucose and 1hG ≥155 mg/dL identified individuals with lower oDI (p=0.01); traditional OGTT criteria for prediabetes did not. No OGTT classification identified individuals with worse BMI nor pulmonary function. oDI was not associated with BMI, FEV1, or FVC.

CONCLUSIONS

Alternate OGTT measures including time to peak glucose and 1hG better identify oDI abnormalities than traditional criteria. Further studies are required to determine whether these alternate methods identify individuals with CF at risk for future clinical decline.

Epithelial vectorial ion transport in cystic fibrosis: Dysfunction, measurement, and pharmacotherapy to target the primary deficit

Cystic fibrosis patients display multi-organ system dysfunction (e.g. pancreas, gastrointestinal tract, and lung) with pathogenesis linked to a failure of Cl^- secretion from the epithelial surfaces of these organs. If unmanaged, organ dysfunction starts early and patients experience chronic respiratory infection with reduced lung function and a failure to thrive due to gastrointestinal malabsorption. Early mortality is typically caused by respiratory failure. In the past 40 years of newborn screening and improved disease management have driven the median survival up from the mid-teens to 43-53, with most of that improvement coming from earlier and more aggressive management of the symptoms. In the last decade, promising pharmacotherapies have been developed for the correction of the underlying epithelial dysfunction, namely, Cl^- secretion. A new generation of systemic drugs target the mutated Cl^- channels in cystic fibrosis patients and allow trafficking of the immature mutated protein to the cell membrane (correctors), restore function to the channel once in situ (potentiators), or increase protein levels in the cells (amplifiers). Restoration of channel function prior to symptom development has the potential to significantly change the trajectory of disease progression and their evidence suggests that a modest restoration of Cl^- secretion may delay disease progression by decades. In this article, we review epithelial vectorial ion and fluid transport, its quantification and measurement as a marker for cystic fibrosis ion transport dysfunction, and highlight some of the recent therapies targeted at the dysfunctional ion transport of cystic fibrosis.

Monogenic diabetes mellitus in cystic fibrosis

We present a non-consanguineous family of three siblings who presented with diabetes mellitus (DM), two of whom had genetically confirmed cystic fibrosis (CF), with one pancreatic-sufficient mutation in the cystic fibrosis transmembrane conductance regulator (CFTR) gene (ΔF508/R117H;IVS8-5T). A detailed history revealed family members from three successive generations diagnosed with 'type 1' or 'type 2' diabetes, leading to genetic investigations for monogenic DM. A heterozygous frameshift mutation in the hepatocyte nuclear factor 1 homeobox alpha (HNF1A) gene (c.404delA) was subsequently confirmed in all three siblings, which is known to cause monogenic diabetes and is exquisitely sensitive to sulfonylurea therapy. Following this diagnosis, both siblings with CF and HNF1A monogenic diabetes were started on gliclazide therapy, while their older brother who had been wrongly diagnosed with type 1 diabetes was switched from insulin to gliclazide, all with excellent therapeutic responses.

Diabetes mellitus in pediatric solid organ recipients without and with cystic fibrosis: An analysis from the German-Austrian diabetes database (Diabetes Patienten Verlaufsdokumentation)

INTRODUCTION

Posttransplantation diabetes mellitus (PTDM) increases the risk of cardiovascular disease, graft loss, and decreased survival. Follow-up treatment after solid organ transplantation (SOT) needs to focus on, inter alia, maintaining balanced glucose metabolism. This study aimed to ascertain the prevalence of PTDM and describe patient characteristics in the large DPV (Diabetes Patienten Verlaufsdokumentation) pediatric diabetes database.

METHODS

DPV data of 71 902 patients from the January 01, 1995 to January 04, 2015 period were analyzed for patients with and without cystic fibrosis (CF) after SOT (kidney, liver, heart, and lung). Multivariable analysis served to assess differences between SOT patient groups at risk for developing diabetes.

RESULTS

Out of 109 SOT patients, 51 had CF; 72.5% received steroids and 62% were additionally given tacrolimus. PTDM developed in 45% of CF patients and 12% of non-CF patients. SOT patients were older at diabetes onset (mean age, 12.50 ± 3.98 years), shorter (height z-score, -1.67 ± 1.25), and lighter (weight z-score, -1.59 ± 1.57) than non-SOT diabetes patients (P < 0.01). With transplantation, glycated hemoglobin (HbA1c) was significantly lower and treatment for hypertension and dyslipidemia was increased. Among SOT patients, weight and body mass index (BMI) z-scores were significantly lower in patients with CF-related diabetes (P < 0.05).

CONCLUSIONS

SOT was present in 6.6% of children with diabetes, and this might aggravate the risk of cardiovascular disease in populations with already increased rates of hypertension and dyslipidemia. Dystrophy and short stature were also present, particularly in transplant recipients with CF and diabetes. Comorbidities and long-term consequences call for multidisciplinary collaboration.

Repaglinide versus insulin for newly diagnosed diabetes in patients with cystic fibrosis: a multicentre, open-label, randomised trial

BACKGROUND

As survival among patients with cystic fibrosis has improved in recent decades, complications have become increasingly relevant. The most frequent complication is cystic-fibrosis-related diabetes. The recommended treatment is injected insulin, but some patients are treated with oral antidiabetic drugs to ease the treatment burden. We assessed the efficacy and safety of oral antidiabetic drugs.

METHODS

We did a multicentre, open-label, comparative, randomised trial in 49 centres in Austria, France, Germany, and Italy. Eligible patients had cystic fibrosis, were older than 10 years, and had newly diagnosed diabetes. We used a central randomisation schedule derived from a Geigy random number table to assign patients 1:1 to receive insulin or repaglinide, stratified by sex and age (10-15 years or >15 years). The primary outcome was glycaemic control assessed by mean change in HbA_1c concentration from baseline after 24 months of treatment. Differences between groups were assessed by linear models. The primary and safety analyses were done in the modified intention-to-treat population (including patients who stopped treatment early because of lack of efficacy). This trial is registered with ClinicalTrials.gov, number NCT00662714.

FINDINGS

We enrolled 34 patients in the repaglinide group and 41 in the insulin group, of whom 30 and 37, respectively, were included in the analyses. At 24 months, glycaemic control was similar in the repaglinide and insulin groups (mean change in HbA_1c concentration from baseline 0·2% [SD 0·7%], 1·7 mmol/mol [8·1 mmol/mol] with repaglinide vs -0·2% [1·3%], -2·7 mmol/mol, [14·5 mmol/mol] with insulin; mean difference between groups -0·4%, (95% CI -1·1 to 0·2 [-4·4 mmol/mol, -11·5 to 2·7], p=0·15). The most frequent adverse events were pulmonary events (43 [40%] of 107 in the repaglinide group and 60 [45%] of 133 in the insulin group), and the most frequent serious adverse events were pulmonary events leading to hospital admission (five [50%] of ten and seven [54%] of 13, respectively).

INTERPRETATION

Repaglinide for glycaemic control in patients with cystic-fibrosis-related diabetes is as efficacious and safe as insulin.

FUNDING

Mukoviszidose eV, Vaincre la Mucoviscidose, ABCF Association, and Novo Nordisk.

A description of clinician reported diagnosis of type 2 diabetes and other non-type 1 diabetes included in a large international multicentered pediatric diabetes registry (SWEET)

BACKGROUND

Although type 1 diabetes (T1D) remains the most frequent form of diabetes in individuals aged less than 20 years at onset, other forms of diabetes are being increasingly recognized.

OBJECTIVES

To describe the population of children with other forms of diabetes (non-type 1) included in the multinational SWEET (Better control in Pediatric and Adolescent diabeteS: Working to crEate CEnTers of Reference) database for children with diabetes.

METHODS

Cases entered in the SWEET database are identified by their physician as T1D, type 2 diabetes (T2D) and other types of diabetes according to the ISPAD classification. Etiologic subgroups are provided for other types of diabetes. Descriptive analyses were tabulated for age at onset, gender, daily insulin doses, and hemoglobin A1c (A1C) for each type and subtype of diabetes and when possible, values were compared.

RESULTS

Of the 27 104 patients included in this report, 95.5% have T1D, 1.3% T2D, and 3.2% other forms of diabetes. The two most frequent etiologies for other forms of diabetes were maturity onset diabetes of the young (MODY) (n = 351) and cystic fibrosis-related diabetes (CFRD) (n = 193). The cause was unknown or unreported in 10% of other forms of diabetes. Compared with T1D, children with T2D and CFRD were diagnosed at an older age, took less insulin and had lower A1C (all P < .0001).

CONCLUSION

In centers included in SWEET, forms of diabetes other than type 1 remain rare and at times difficult to characterize. Sharing clinical information and outcome between SWEET centers on those rare forms of diabetes has the potential to improve management and outcome.

High variability in oral glucose tolerance among 1,128 patients with cystic fibrosis: a multicenter screening study

Background

In cystic fibrosis, highly variable glucose tolerance is suspected. However, no study provided within-patient coefficients of variation. The main objective of this short report was to evaluate within-patient variability of oral glucose tolerance.

Methods

In total, 4,643 standardized oral glucose tolerance tests of 1,128 cystic fibrosis patients (median age at first test: 15.5 [11.5; 21.5] years, 48.8% females) were studied. Patients included were clinically stable, non-pregnant, and had at least two oral glucose tolerance tests, with no prior lung transplantation or systemic steroid therapy. Transition frequency from any one test to the subsequent test was analyzed and within-patient coefficients of variation were calculated for fasting and two hour blood glucose values. All statistical analysis was implemented with SAS 9.4.

Results

A diabetic glucose tolerance was confirmed in 41.2% by the subsequent test. A regression to normal glucose tolerance at the subsequent test was observed in 21.7% and to impaired fasting glucose, impaired glucose tolerance or both in 15.2%, 12.0% or 9.9%. The average within-patient coefficient of variation for fasting blood glucose was 11.1% and for two hour blood glucose 25.3%.

Conclusion

In the cystic fibrosis patients studied, a highly variable glucose tolerance was observed. Compared to the general population, variability of two hour blood glucose was 1.5 to 1.8-fold higher.

Cystic fibrosis related diabetes

Improved life expectancy in cystic fibrosis (CF) has led to an expanding population of adults with CF, now representing almost 50 % of the total CF population. This creates new challenges from long-term complications such as diabetes mellitus (DM), a condition that is present in 40 %-50 % of adults with CF. Cystic fibrosis-related diabetes (CFRD) results from a primary defect of insulin deficiency and although sharing features with type 1 (DM1) and type 2 diabetes (DM2), it is a clinically distinct condition. Progression to diabetes is associated with poorer CF clinical outcomes and increased mortality. CFRD is not associated with an increased risk of cardiovascular disease and the prevalence of microvascular complications is lower than DM1 or DM2. Rather, the primary goal of insulin therapy is the preservation of lung function and optimization of nutritional status. There is increasing evidence that appropriate screening and early intervention with insulin can reverse weight loss and improve pulmonary function. This approach may include targeting postprandial hyperglycemia not detected by standard diagnostic tests such as the oral glucose tolerance test. Further clinical research is required to guide when and how much to intervene in patients who are already dealing with the burden of one chronic illness.

Adherence to clinical care guidelines for cystic fibrosis-related diabetes in 659 German/Austrian patients

BACKGROUND

In Germany/Austria, data on medical care for cystic fibrosis-related diabetes (CFRD) is limited.

METHODS

Anonymized data from 659 CFRD patients were analyzed and compared to the latest ADA/CFF guidelines.

RESULTS

Specialized diabetes clinics were attended less frequently than recommended (3.1 vs. 4.0 times yearly). 7.9% of patients had a complete profile of examinations: diabetes education (44.9%), HbA1c (88.8%), blood pressure (79.5%), BMI (86.5%), lipid status (37.5%), retinopathy (29.9%), microalbuminuria (33.2%), and self-monitoring of blood glucose (71.6%). HbA1c and blood pressure were measured less frequently than recommended (2.3 and 2.0 vs. 4.0 times yearly). Overall, guidelines were followed more frequently in children than adults. Contrary to recommendations, not all patients were treated with insulin (77.2 vs. 100.0%). Insulin therapy was initiated earlier in children than adults, but there was still a substantial delay (0.9 vs. 2.7years after diagnosis, p<0.001).

CONCLUSION

In CFRD patients studied, adherence to care guidelines was suboptimal.