Cystic fibrosis-related diabetes compared with type 1 and type 2 diabetes in adults

Effects of insulin therapy optimization with sensor augmented pumps on glycemic control and body composition in people with cystic fibrosis-related diabetes

Objective

Cystic fibrosis (CF)-related diabetes (CFRD) resulting from partial-to-complete insulin deficiency occurs in 40-50% of adults with CF. In people with CFRD, poor glycemic control leads to a catabolic state that may aggravate CF-induced nutritional impairment and loss of muscle mass. Sensor augmented pump (SAP) therapy may improve glycemic control as compared to multiple daily injection (MDI) therapy.

Research design and methods

This non-randomized clinical trial was aimed at evaluating the effects of insulin therapy optimization with SAP therapy, combined with a structured educational program, on glycemic control and body composition in individuals with insulin-requiring CFRD. Of 46 participants who were offered to switch from MDI to SAP therapy, 20 accepted and 26 continued the MDI therapy. Baseline demographic and clinical characteristics were balanced between groups using a propensity score-based overlap weighting procedure and weighted mixed-effects regression models were used to estimate changes in study outcomes.

Results

After 24 months changes in HbA1c were: -1.1% (-12.1 mmol/mol) (95% CI: -1.5; -0.8) and -0.1% (-1 mmol/mol) (95% CI: -0.5; 0.3) in the SAP and MDI therapy group, respectively, with a between-group difference of -1.0 (-10 mmol/mol) (-1.5; -0.5). SAP therapy was also associated with a decrease in mean glucose (between group difference: -32 mg/dL; 95% CI: -44; -20) and an increase in TIR (between group difference: 19.3%; 95% CI 13.9; 24.7) and in fat-free mass (between group difference: +5.5 Kg, 95% CI: 3.2; 7.8).

Conclusion

Therapy optimization with SAP led to a significant improvement in glycemic control, which was associated with an increase in fat-free mass.

The Impact of Pancreatic Exocrine Diseases on the β-Cell and Glucose Metabolism-A Review with Currently Available Evidence

Pancreatic exocrine and endocrine dysfunctions often come together in the course of pancreatic diseases as interdependent manifestations of the same organ. However, the mechanisms underlying the bidirectional connection of the exocrine and endocrine pancreas are not fully understood. In this review, we aimed to synthetize the current knowledge regarding the effects of several exocrine pancreatic pathologies on the homeostasis of β-cells, with a special interest in the predisposition toward diabetes mellitus (DM). We focused on the following pancreatic exocrine diseases: chronic pancreatitis, acute pancreatitis, cystic fibrosis, pancreatic cancer, pancreatic resections, and autoimmune pancreatitis. We discuss the pathophysiologic mechanisms behind the impact on β-cell function and evolution into DM, as well as the associated risk factors in progression to DM, and we describe the most relevant and statistically significant findings in the literature. An early and correct diagnosis of DM in the setting of pancreatic exocrine disorders is of paramount importance for anticipating the disease's course and its therapeutical needs.

Cystic fibrosis related diabetes (CFRD) prognosis

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Poor nutritional status and decreased lean body mass.

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Decline in pulmonary function.

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Increased mortality from lung disease.

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Microvascular complications.

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Macrovascular complications (not currently a significant complication but this may change with modulators).

Cystic fibrosis related diabetes (CFRD) occurs in at least 40–50% of adults with CF. With other forms of diabetes, microvascular and macrovascular disease are the major causes of morbidity and mortality. Macrovascular disease is rare in CF. While microvascular disease does occur in this population, there are CF-specific diabetes complications that have a more important impact on prognosis. The additional diagnosis of diabetes in CF is associated with decreased lung function, poor nutritional status, and an overall increase in mortality from lung disease. These negative findings start even before the clinical diagnosis of CFRD, during the period when patients experience abnormal glucose tolerance related to insulin insufficiency. The main mechanisms by which CFRD negatively affects prognosis are thought to be a combination of 1) protein catabolism, decreased lean body mass and undernutrition resulting from insulin insufficiency, and 2) an increased pro-inflammatory and pro-infectious state related to intermittent hyperglycemia. With the introduction of CFTR modulators, the care of CF patients has been revolutionized and many aspects of CF health such as BMI and lung function are improving. The impact of these drugs on the adverse prognosis related to the diagnosis of diabetes in CF, as well as the potential to delay or prevent onset of CFRD remain to be determined.

Understanding the Pancreatic Islet Microenvironment in Cystic Fibrosis and the Extrinsic Pathways Leading to Cystic Fibrosis Related Diabetes

Cystic fibrosis (CF) is an autosomal recessive chronic condition effecting approximately 70 000 to 100 000 people globally and is caused by a loss-of-function mutation in the CF transmembrane conductance regulator. Through improvements in clinical care, life expectancy in CF has increased considerably associated with rising incidence of secondary complications including CF-related diabetes (CFRD). CFRD is believed to result from β-cell loss as well as insufficient insulin secretion due to β-cell dysfunction, but the underlying pathophysiology is not yet fully understood. Here we review the morphological and cellular changes in addition to the architectural remodelling of the pancreatic exocrine and endocrine compartments in CF and CFRD pancreas. We consider also potential underlying proinflammatory signalling pathways impacting on endocrine and specifically β-cell function, concluding that further research focused on these mechanisms may uncover novel therapeutic targets enabling restoration of normal insulin secretion.

Effect of CFTR modulator therapy on cystic fibrosis-related diabetes

BACKGROUND

Half of adults with cystic fibrosis (CF) develop CF-related diabetes (CFRD). CFRD contributes to worsened pulmonary function and malnutrition. We undertook this study to determine the effect of cystic fibrosis transmembrane regulator (CFTR) modulators on CRFD.

METHODS

We reviewed the medical records of adults with CF who followed in the CF clinic at Oklahoma University Medical Center. We collected data for age at diagnosis of CF and CFRD, CF mutations present, first date of ivacaftor therapy either alone or in combination, insulin use, pulmonary function, body mass index data, and home glucose monitoring results. Clinical resolution of CFRD was taken as discontinuation of routine insulin and resolution of high interstitial home glucose values.

RESULTS

We identified 69 adult CF patients, of whom 31 had CFRD. Among these 14 CFRD patients taking ivacaftor alone or in combination, four patients completely stopped using insulin. Another patient went from three times a day pre-prandial insulin to using insulin once a week. Home blood glucose and hemoglobin A1c values supported resolution of CFRD. Three patients continued to have hypoglycemia despite stopping insulin. No CFRD patient not taking CFTR modulators markedly changed the insulin regimen. Pulmonary function was preserved in those patients with resolved CFRD (FEV₁ +6.75% ±7.6), whereas it worsened in CFRD patients who either were not taking CFTR modulators (FEV₁ -2.09% ±3.9) or who had no response of CFRD status (FEV₁ -4.9% ±7.6).

CONCLUSIONS

About one-third of patients on CFTR modulator therapy had resolution or near resolution of CFRD.

CFTR Deficiency Affects Glucose Homeostasis via Regulating GLUT4 Plasma Membrane Transportation

Cystic Fibrosis (CF) is an autosomal recessive disorder caused by mutations in the Cystic Fibrosis Transmembrane Conductance Regulator (CFTR) gene. CF-related diabetes (CFRD) is one of the most prevalent comorbidities of CF. Altered glucose homeostasis has been reported in CF patients. The mechanism has not been fully elucidated. Besides the consequence of pancreatic endocrine dysfunction, we focus on insulin-responsive tissues and glucose transportation to explain glucose homeostasis alteration in CFRD. Herein, we found that CFTR knockout mice exhibited insulin resistance and glucose tolerance. Furthermore, we demonstrated insulin-induced glucose transporter 4 (GLUT4) translocation to the cell membrane was abnormal in the CFTR knockout mice muscle fibers, suggesting that defective intracellular GLUT4 transportation may be the cause of impaired insulin responses and glucose homeostasis. We further demonstrated that PI(4,5)P₂ could rescue CFTR related defective intracellular GLUT4 transportation, and CFTR could regulate PI(4,5)P₂ cellular level through PIP5KA, suggesting PI(4,5)P₂ is a down-stream signal of CFTR. Our results revealed a new signal mechanism of CFTR in GLUT4 translocation regulation, which helps explain glucose homeostasis alteration in CF patients.

The supply chain of human pancreatic β cell lines

Patients with type 1 or type 2 diabetes have an insufficiency in their functional β cell mass. To advance diabetes treatment and to work toward a cure, a better understanding of how to protect the pancreatic β cells against autoimmune or metabolic assaults (e.g., obesity, gestation) will be required. Over the past decades, β cell protection has been extensively investigated in rodents both in vivo and in vitro using isolated islets or rodent β cell lines. Transferring these rodent data to humans has long been challenging, at least partly for technical reasons: primary human islet preparations were scarce and functional human β cell lines were lacking. In 2011, we described a robust protocol of targeted oncogenesis in human fetal pancreas and produced the first functional human β cell line, and in subsequent years additional lines with specific traits. These cell lines are currently used by more than 150 academic and industrial laboratories worldwide. In this Review, we first explain how we developed the human β cell lines and why we think we succeeded where others, despite major efforts, did not. Next, we discuss the use of such functional human β cell lines and share some perspectives on their use to advance diabetes research.

Patient-derived pancreas-on-a-chip to model cystic fibrosis-related disorders

Cystic fibrosis (CF) is a genetic disorder caused by defective CF Transmembrane Conductance Regulator (CFTR) function. Insulin producing pancreatic islets are located in close proximity to the pancreatic duct and there is a possibility of impaired cell-cell signaling between pancreatic ductal epithelial cells (PDECs) and islet cells as causative in CF. To study this possibility, we present an in vitro co-culturing system, pancreas-on-a-chip. Furthermore, we present an efficient method to micro dissect patient-derived human pancreatic ducts from pancreatic remnant cell pellets, followed by the isolation of PDECs. Here we show that defective CFTR function in PDECs directly reduced insulin secretion in islet cells significantly. This uniquely developed pancreatic function monitoring tool will help to study CF-related disorders in vitro, as a system to monitor cell-cell functional interaction of PDECs and pancreatic islets, characterize appropriate therapeutic measures and further our understanding of pancreatic function.

Defective CFTR protein, responsible for Cystic Fibrosis (CF), is highly expressed in pancreatic ductal epithelial cells (PDECs) but their impact on insulin secreting pancreatic islets is not fully understood. Here the authors develop a non-CF and CF patient derived pancreas-on-a-chip model to study how CF affects insulin secretion.

Characteristics of cystic fibrosis-related diabetes: Data from two different sources the European cystic fibrosis society patient registry and German/Austrian diabetes prospective follow-up registry

BACKGROUND

Standardized patient registries provide a unique basis to get insight into cystic fibrosis (CF)-related diabetes (CFRD), the most common comorbidity in CF.

METHODS

A total of 3853 CFRD patients from the European CF Society Patient Registry (ECFSPR) and 752 from the German/Austrian diabetes prospective follow-up (diabetes patienten verlaufsdokumentation [DPV]) were studied. To adjust for age and sex, multivariable regression was used (SAS 9.4).

RESULTS

DPV subjects were younger (26.5 [20.2-32.6] vs 28.3 [21.7-36.0] years, P < 0.001) and more often female (59.6 vs 50.9%, P < 0.001). In both registries, F508del homozygotes were most frequent, with higher proportion in DPV (80.9 vs 57.8%, P = 0.003). After adjustment, lung-transplantation (LTX) was more common in ECFSPR (18.9 vs 4.9%, P < 0.001), although duration since LTX (4.8 ± 0.2 vs 5.5 ± 0.7 years, P = 0.33) did not differ. In DPV patients without LTX, a lower BMI (19.6 ± 0.1 vs 21.0 ± 0.1 kg/m² , P < 0.001), higher proportion of underweight (41.2 vs 20.2%, P < 0.001) and a tendency towards worse lung function (%FEV₁ : 42.3 ± 4.2 vs 48.3 ± 0.5%, P = 0.16) were observed.

CONCLUSIONS

Between both registries, demographic and clinical differences of CFRD were present. Besides different kind of data sources, diverse treatment structures between countries may play a role. The results may further indicate a more serious illness in patients treated in specialized diabetes clinics, documenting their data in DPV.

Cystic fibrosis-related diabetes is caused by islet loss and inflammation

Cystic fibrosis-related (CF-related) diabetes (CFRD) is an increasingly common and devastating comorbidity of CF, affecting approximately 35% of adults with CF. However, the underlying causes of CFRD are unclear. Here, we examined cystic fibrosis transmembrane conductance regulator (CFTR) islet expression and whether the CFTR participates in islet endocrine cell function using murine models of β cell CFTR deletion and normal and CF human pancreas and islets. Specific deletion of CFTR from murine β cells did not affect β cell function. In human islets, CFTR mRNA was minimally expressed, and CFTR protein and electrical activity were not detected. Isolated CF/CFRD islets demonstrated appropriate insulin and glucagon secretion, with few changes in key islet-regulatory transcripts. Furthermore, approximately 65% of β cell area was lost in CF donors, compounded by pancreatic remodeling and immune infiltration of the islet. These results indicate that CFRD is caused by β cell loss and intraislet inflammation in the setting of a complex pleiotropic disease and not by intrinsic islet dysfunction from CFTR mutation.

Cystic Fibrosis-Related Diabetes

Cystic fibrosis (CF) is the most common autosomal recessive disorder in Caucasian populations. Individuals with CF have seen significant increases in life expectancy in the last 60 years. As a result, previously rare complications are now coming to light. The most common of these is cystic fibrosis-related diabetes (CFRD), which affects 40-50% of CF adults. CFRD significantly impacts the pulmonary function and longevity of CF patients, yet a lack of consensus on the best methods to diagnose and treat CFRD remains. We begin by reviewing our understanding of the pathogenesis of CFRD, as emerging evidence shows the cystic fibrosis transmembrane conductance regulator (CFTR) also has important roles in the release of insulin and glucagon and in the protection of β cells from oxidative stress. We then discuss how current recommended methods of CFRD diagnosis are not appropriate, as continuous glucose monitoring becomes more effective, practical, and cost-effective. Finally, we evaluate emerging treatments which have narrowed the mortality gap within the CF patient group. In the future, pharmacological potentiators and correctors directly targeting CFTR show huge promise for both CFRD and the wider CF patient groups.

Evolving Mechanistic Views and Emerging Therapeutic Strategies for Cystic Fibrosis-Related Diabetes

Diabetes is a common and important complication of cystic fibrosis, an autosomal recessive genetic disease due to mutations in the cystic fibrosis transmembrane conductance regulator (CFTR) gene. Cystic fibrosis-related diabetes (CFRD) is associated with profound detrimental effects on the disease course and mortality and is expected to increase in prevalence as the survival of patients with cystic fibrosis continues to improve. Despite progress in the functional characterization of CFTR molecular defects, the mechanistic basis of CFRD is not well understood, in part because of the relative inaccessibility of the pancreatic tissue and the limited availability of representative animal models. This review presents a concise overview of the current understanding of CFRD pathogenesis and provides a cutting-edge update on novel findings from human and animal studies. Potential contributions from paracrine mechanisms and β-cell compensatory mechanisms are highlighted, as well as functional β-cell and α-cell defects, incretin defects, exocrine pancreatic insufficiency, and loss of islet cell mass. State-of-the-art and emerging treatment options are explored, including advances in insulin administration, CFTR modulators, cell replacement, gene replacement, and gene editing therapies.

The Mechanistic Links between Insulin and Cystic Fibrosis Transmembrane Conductance Regulator (CFTR) Cl- Channel

The cystic fibrosis transmembrane conductance regulator (CFTR) Cl⁻ channel belongs to the ATP-binding cassette (ABC) transporter superfamily and regulates Cl⁻ secretion in epithelial cells for water secretion. Loss-of-function mutations to the CFTR gene cause dehydrated mucus on the apical side of epithelial cells and increase the susceptibility of bacterial infection, especially in the airway and pulmonary tissues. Therefore, research on the molecular properties of CFTR, such as its gating mechanism and subcellular trafficking, have been intensively pursued. Dysregulated CFTR trafficking is one of the major pathological hallmarks in cystic fibrosis (CF) patients bearing missense mutations in the CFTR gene. Hormones that activate cAMP signaling, such as catecholamine, have been found to regulate the intracellular trafficking of CFTR. Insulin is one of the hormones that regulate cAMP production and promote trafficking of transmembrane proteins to the plasma membrane. The functional interactions between insulin and CFTR have not yet been clearly defined. In this review article, I review the roles of CFTR in epithelial cells, its regulatory role in insulin secretion, and a mechanism of CFTR regulation by insulin.

Physical Activity Levels in Individuals with Cystic Fibrosis-Related Diabetes

Purpose: The literature on physical activity (PA) in adults with cystic fibrosis, particularly in those with cystic fibrosis-related diabetes (CFRD), is limited. PA may be an important part of blood glucose management in CFRD. The purpose of this study was to describe PA levels in adults with CFRD and determine their adherence to the Canadian Diabetes Association (CDA) aerobic exercise training guidelines. Methods: Adults with CFRD were recruited from a hospital-based CF clinic. PA was measured using the Seven-Day Physical Activity Recall (telephone interview), adherence to CFRD management with the Self-Care Inventory-Revised (questionnaire), and blood glucose control from glycated hemoglobin levels documented in participants' medical chart within 3 months. Results: Eighteen adults (mean age 41 [SD 9] y) with diagnosed CFRD participated in the study. They varied in volume of PA (range 13,080-17,362 metabolic equivalent min/wk). Of the study participants, 12 (67%) met the CDA guidelines of 150 minutes of moderate to vigorous PA per week with no more than 2 consecutive days without exercise. No differences were found in clinical factors between those who met the aerobic exercise guidelines and those who did not. Conclusion: The majority of individuals with CFRD are meeting the recommended amount of aerobic PA. The factors influencing PA and blood glucose control in adults with CFRD require further investigation.

Current and Emerging Therapies for the Treatment of Cystic Fibrosis or Mitigation of Its Symptoms

Clinical presentation of the chronic, heritable condition cystic fibrosis (CF) is complex, with a diverse range of symptoms often affecting multiple organs with varying severity. The primary source of morbidity and mortality is due to progressive destruction of the airways attributable to chronic inflammation arising from microbial colonisation. Antimicrobial therapy combined with practises to remove obstructive mucopurulent deposits form the cornerstone of current therapy. However, new treatment options are emerging which offer, for the first time, the opportunity to effect remission from the underlying cause of CF. Here, we discuss these therapies, their mechanisms of action, and their successes and failures in order to illustrate the shift in the nature of how CF will likely be managed into the future.

Glucose-induced electrical activities and insulin secretion in pancreatic islet β-cells are modulated by CFTR

The cause of insulin insufficiency remains unknown in many diabetic cases. Up to 50% adult patients with cystic fibrosis (CF), a disease caused by mutations in the gene encoding the CF transmembrane conductance regulator (CFTR), develop CF-related diabetes (CFRD) with most patients exhibiting insulin insufficiency. Here we show that CFTR is a regulator of glucose-dependent electrical acitivities and insulin secretion in β-cells. We demonstrate that glucose elicited whole-cell currents, membrane depolarization, electrical bursts or action potentials, Ca(2+) oscillations and insulin secretion are abolished or reduced by inhibitors or knockdown of CFTR in primary mouse β-cells or RINm5F β-cell line, or significantly attenuated in CFTR mutant (DF508) mice compared with wild-type mice. VX-809, a newly discovered corrector of DF508 mutation, successfully rescues the defects in DF508 β-cells. Our results reveal a role of CFTR in glucose-induced electrical activities and insulin secretion in β-cells, shed light on the pathogenesis of CFRD and possibly other idiopathic diabetes, and present a potential treatment strategy.