Diagnosis, screening, and management of cystic fibrosis-related diabetes

Pancreatic islet dysfunction in type 2 diabetes mellitus

Islet dysfunction is a hallmark of type 2 diabetes mellitus (T2DM). Compelling evidence suggests that accumulation of islet amyloid in the islets of Langerhans significantly contribute to β-cell dysfunction and diabetes. Emerging evidence implicates a role for cystic fibrosis transmembrane-conductance regulator in the regulation of insulin secretion from pancreatic islets. Impaired first-phase insulin responses and glucose homeostasis have also been reported in cystic fibrosis patients. The transforming growth factor-β protein superfamily is central regulators of pancreatic cell function, and has a key role in pancreas development and pancreatic disease, including diabetes and islet dysfunction. It is also becoming clear that islet inflammation plays a key role in the development of islet dysfunction. Inflammatory changes, including accumulation of macrophages, have been documented in type 2 diabetic islets. Islet dysfunction leads to hyperglycemia and ultimately the development of diabetes. In this review, we describe these risk factors and their associations with islet dysfunction.

Glucose ingestion in cystic fibrosis induces severe redox imbalance: A potential role in diabetes

BACKGROUND

Cystic fibrosis related diabetes (CFRD) is the most common co-morbidity associated with cystic fibrosis (CF). Individuals with CF demonstrate airway and systemic oxidation compared to people without CF. Furthermore, systemic oxidation precipitated by hyperglycemia in non-CF diabetes has been shown to lead to enhanced inflammation. We hypothesized that the presence of both CF and diabetes in an individual would result in hyperglycemia-induced redox imbalance to an oxidative state. This in turn would result in enhanced production of pro-inflammatory cytokines.

METHODS

Systemic redox balance and pro-inflammatory cytokines were measured before and following a standard oral glucose tolerance test in healthy controls (HC) and in CF individuals with a spectrum of glucose homeostasis (i.e. normal glucose tolerant - NGT, prediabetes or frank CFRD).

RESULTS

There were no significant differences between groups in terms of basal or glucose-induced levels of inflammatory markers. However, baseline systemic redox potential was significantly more oxidized in CF subjects with prediabetes and CFRD compared to both CF with NGT and HC. Systemic oxidation was significantly worsened, and to a profound degree, two hours following ingestion of glucose in all CF groups (NGT, prediabetes, and CFRD). The level of redox imbalance at the two hour point was the same in all three CF groups and was not associated with the degree of hyperglycemia. There was a significant correlation between worse systemic oxidation and reduced insulin secretion.

CONCLUSIONS

This supports a newly identified abnormality of metabolism in CF - glucose induced redox imbalance to the oxidative state.

Glucose-Sensitive CFTR Suppresses Glucagon Secretion by Potentiating KATP Channels in Pancreatic Islet α Cells

The secretion of glucagon by islet α cells is normally suppressed by high blood glucose, but this suppressibility is impaired in patients with diabetes or cystic fibrosis (CF), a disease caused by mutations in the gene encoding CF transmembrane conductance regulator (CFTR), a cyclic adenosine monophosphate-activated Cl- channel. However, precisely how glucose regulates glucagon release remains controversial. Here we report that elevated glucagon secretion, together with increased glucose-induced membrane depolarization and Ca2+ response, is found in CFTR mutant (DF508) mice/islets compared with the wild-type. Overexpression of CFTR in AlphaTC1-9 cells results in membrane hyperpolarization and reduced glucagon release, which can be reversed by CFTR inhibition. CFTR is found to potentiate the adenosine triphosphate-sensitive K+ (KATP) channel because membrane depolarization and whole-cell currents sensitive to KATP blockers are significantly greater in wild-type/CFTR-overexpressed α cells compared with that in DF508/non-overexpressed cells. KATP knockdown also reverses the suppressive effect of CFTR overexpression on glucagon secretion. The results reveal that by potentiating KATP channels, CFTR acts as a glucose-sensing negative regulator of glucagon secretion in α cells, a defect of which may contribute to glucose intolerance in CF and other types of diabetes.

Elevation of one hour plasma glucose during oral glucose tolerance testing

OBJECTIVES

In cystic fibrosis (CF) patients, elevations in 1 hr plasma glucose (PG1) during a 75 g oral glucose tolerance test are common, but of unclear long-term clinical relevance. Thus, we examined associations of PG1 with percent-predicted forced expiratory volume in 1 sec (FEV1 % predicted), CF exacerbations, and CF related diabetes (CFRD) development.

STUDY DESIGN

We conducted a retrospective cohort study of 80 pediatric patients with CF (43 males) followed over 5 years in a single CF center. We considered the association between elevated versus normal PG1 (greater vs. no greater than 160 mg/dl) and linear changes in FEV1 % predicted over time for males and female, as well as the odds of a CF exacerbation and the odds of developing CFRD.

RESULTS

No significant difference in FEV1 % predicted between normal versus elevated PG1 was found at baseline, or over time in males or females. However, males with elevated PG1 tended to have worse FEV1 % predicted over time than those with normal PG1 (reduction of 0.9 FEV1 % predicted/year, 95%CI: -2.5, 0.6). Subjects with PG1 > 160 mg/dl were more likely to develop CFRD (OR 4.5, 95%CI: 1.7, 18.7, P = 0.04) but CF exacerbation risk was similar in both groups.

CONCLUSION

The risk of CFRD increases with PG1 > 160 mg/dl. No statistically significant evidence of an association between elevated PG1 and pulmonary function was found, yet our results do not exclude the possibility that in males, elevated PG1 may signal adverse changes in FEV1 % predicted over time. This possibility requires further study with a larger sample size.

[Screening and management of glucose metabolism disorders in cystic fibrosis patients. Practices survey in 4 French reference centers]

OBJECTIVE

Glucose metabolism disorders are a new point of interest in cystic fibrosis (CF) management. Cystic fibrosis-related diabetes mellitus (CFRD) increases alteration of pulmonary function as well as patients' morbidity and mortality. In France, CF patients are exclusively followed up in reference centers. We conducted a practices survey on screening and diagnosis of glucose metabolism disorders at 4 French CF centers. The objective of this study was to assess adherence to practice guidelines developed in 2002 at these centers.

METHODS

This study was conducted in 2 sessions: 60 medical records were randomly selected in 2005 and in 2007 for patients aged over 10 years followed up at 4 CF centers. A questionnaire survey was completed for each patient with questions on CFRD screening, diagnosis, monitoring and treatment. Our guidelines recommend random blood glucose (RBG) at each standard biological test, annual glycosylated haemoglobin and an oral glucose tolerance test (OGTT) at 10, 15 and 18 years of age, then every 2 or 3 years.

RESULTS

An annual RBG was performed in 82% of patients in 2005 and 91.5% in 2007. HbA1c screening was performed annually for 77% of patients in the 1st session and for 90% of patients for the 2nd session (p<0.10). Adherence to OGTT guidelines was better for adults than children: 96% had an OGTT during the 3 years of the first session and 79% during the second session, while fewer than 50% of children had their OGTT at 15 and 18 years of age. Taking the OGTT at 10 years of age could not be assessed because no patients were 10 years old during the study period. Screening for neurological complications of CFRD was assessed in the majority of diabetic patients, while half or less than half had annual fundus oculi or microalbuminuria dosage.

DISCUSSION

There was an improvement in screening for CFRD and glucose metabolism disorders between 2005 and 2007, even though practices could still be improved. This shows that clinical guidelines can be implemented and followed. However, screening and management criteria for glucose metabolism disorders must be consensus-based with higher evidence in order to limit the variability of practices and prevent CFRD-related complications.

Cystic fibrosis related diabetes

Diabetes is a frequent complication seen in cystic fibrosis patients as they reach adulthood. Cystic fibrosis related diabetes (CFRD) is distinguished as a separate entity with features that include progressive loss of islet beta cell mass and insulin deficiency, as well as insulin resistance. Abnormalities in glucose tolerance may be detectable for many years prior to the development of overt diabetes. Therefore oral glucose tolerance testing is the preferred screening method for the identification of those patients at the highest risk for progression to diabetes. Progression to diabetes has been linked to poor outcomes in CF including loss of pulmonary function and increased mortality among females. Given the role that insulin deficiency plays in CFRD, insulin replacement therapy remains the only recommended intervention. In the absence of definitive supportive data, the use of oral antidiabetic agents is not considered standard therapy and needs further study. As with other forms of diabetes, CFRD patients also experience microvascular complications and should be periodically evaluated for manifestations.

Tachycardia in adults with cystic fibrosis is associated with normal autonomic function

BACKGROUND

Whether autonomic dysfunction contributes to tachycardia in cystic fibrosis (CF) is unknown.

METHODS

Heart rate variability (HRV) was assessed to determine high frequency power and the low/high frequency power ratio (HF, LF/HF) as markers of vagal and sympathovagal balance, respectively, under spontaneous and controlled breathing (15 breaths per minute (bpm)) conditions in 17 CF and 17 healthy control subjects.

RESULTS

Under spontaneously breathing conditions, the CF group was tachycardic (75.4 ± 11.2 vs 60.2 ± 9.0 br/min P < 0.001) and tachypnoeic (22.6 ± 5.8 vs 13.6 ± 4.1 br/min, P= 0.001) compared with controls. No significant difference in HRV was observed between groups during spontaneous or controlled breathing. Coexistent diabetes mellitus and β(2) agonist use were not associated with altered autonomic control. During controlled breathing, the CF group showed a negative correlation between forced expiratory volume in 1 s (FEV(1)) % predicted and HF power (P= 0.013, r=-0.59) and a positive correlation between FEV(1) % predicted and LF/HF ratio (P= 0.002, r= 0.69) suggesting an exaggerated normal vagal response.

CONCLUSION

CF patients have normal autonomic function.

Validation of continuous glucose monitoring in children and adolescents with cystic fibrosis: a prospective cohort study

OBJECTIVE

To validate continuous glucose monitoring (CGM) in children and adolescents with cystic fibrosis.

RESEARCH DESIGN AND METHODS

Paired oral glucose tolerance tests (OGTTs) and CGM monitoring was undertaken in 102 children and adolescents with cystic fibrosis (age 9.5-19.0 years) at baseline (CGM1) and after 12 months (CGM2). CGM validity was assessed by reliability, reproducibility, and repeatability.

RESULTS

CGM was reliable with a Bland-Altman agreement between CGM and OGTT of 0.81 mmol/l (95% CI for bias +/- 2.90 mmol/l) and good correlation between the two (r = 0.74-0.9; P < 0.01). CGM was reproducible with no significant differences in the coefficient of variation of the CGM assessment between visits and repeatable with a mean difference between CGM1 and CGM2 of 0.09 mmol/l (95% CI for difference +/- 0.46 mmol/l) and a discriminant ratio of 13.0 and 15.1, respectively.

CONCLUSIONS

In this cohort of children and adolescents with cystic fibrosis, CGM performed on two occasions over a 12-month period was reliable, reproducible, and repeatable.

One-year glargine treatment can improve the course of lung disease in children and adolescents with cystic fibrosis and early glucose derangements

BACKGROUND

Diabetes increases morbidity and mortality in cystic fibrosis (CF) patients, but several studies indicate that also prediabetic status may have a potential impact on both nutrition and lung function.

OBJECTIVE

To evaluate the effect of glargine on the clinical course in CF patients with early glucose derangements.

METHODS

CF population was screened for glucose tolerance. CF patients with age >10 yr were screened with fasting hyperglycemia (FH). CF patients with age >10 yr without FH and those with age <10 yr with occasional FH were evaluated for glucose abnormalities on the basis of oral glucose tolerance test and/or continuous glucose monitoring system. All CF patients with glucose derangements were enrolled in an open clinical trial with glargine. Body mass index (BMI) z-score, forced expiratory volume in the first second (FEV(1)), number of acute pulmonary exacerbations and hemoglobin A1c, were as outcome measures at baseline and after 1 yr of treatment.

RESULTS

After 12 months of therapy, BMI z-score improved only in patients with baseline BMI z-score less than -1 (p = 0.017). An 8.8% increase in FEV(1) (p = 0.01) and 42% decrease in the number of pulmonary exacerbations (p = 0.003) were found in the whole group compared with previous 12 months of therapy.

CONCLUSION

Glargine could represent an innovative strategy to prevent lung disease progression in CF patients with early glucose derangements. Larger controlled trials are needed to better clarify the effects of insulin on clinical status in CF patients with early glucose derangements.

Diabetes mellitus in patients with cystic fibrosis

Cystic fibrosis-related diabetes (CFRD) is the principal extra-pulmonary complication of cystic fibrosis, occurring in 15-30% of adult cystic fibrosis patients. The number of cystic fibrosis patients who develop diabetes is increasing in parallel with increases in life expectancy. The aim of this study was to review the physiopathology, clinical presentation, diagnosis and treatment of CFRD. A bibliographic search of the Medline and Latin American and Caribbean Health Sciences Literature databases was made. Articles were selected from among those published in the last twenty years. Insulin deficiency, caused by reduced beta-cell mass, is the main etiologic mechanism, although insulin resistance also plays a role. Presenting features of type 1 and type 2 diabetes, CFRD typically affects individuals of approximately 20 years of age. It can also be accompanied by fasting, non-fasting or intermittent hyperglycemia. Glucose intolerance is associated with worsening of nutritional status, increased morbidity, decreased survival and reduced pulmonary function. Microvascular complications are always present, although macrovascular complications are rarely seen. An oral glucose tolerance test is recommended annually for patients > or = 10 years of age and for any patients presenting unexplained weight loss or symptoms of diabetes. Patients hospitalized with severe diseases should also be screened. If fasting hyperglycemia persists for more than 48 h, insulin therapy is recommended. Insulin administration remains the treatment of choice for diabetes and fasting hyperglycemia. Calories should not be restricted, and patients with CFRD should be managed by a multidisciplinary team.

Inpatient Diabetes Mellitus in the Oncology Setting

CASE STUDY

A.B. is a 32-year-old Caucasian man with a significant, 12-year medical history of diabetes mellitus type I as well as a history of hypertension and hypercholesterolemia. He presented to his primary care doctor with blurred vision and was referred to a retinal specialist, who diagnosed hemorhagic and leukemic retinopathy resulting in limited vision. A complete blood count was drawn during the visit with his retinal specialist. The results were abnormal, revealing a white blood cell count of 30,000/mm3, platelet count of 70,000/mm3, and a hemoglobin of 12.2 gm/dl. The peripheral smear showed peripheral blasts. A.B. was referred to a hematologist, who performed a bone marrow aspiration, confirming the diagnosis of pre-B-cell acute lymphocytic leukemia (ALL). Cytogenetic studies revealed positivity for the Philadelphia chromosome and a translocation of genes 4 and 11.

Carbohydrate metabolism changes in cystic fibrosis

AIMS

To assess the prevalence of impaired glucose tolerance (ITG) and diabetes mellitus (DMRCF) in a group of patients with cystic fibrosis (CF). To study clinical status-related variables and to compare age with the evolution of their carbohydrate metabolism (CHM).

PATIENTS AND METHODS

Thirty patients with CF (1.5-26 years). Oral glucose tolerance test (OGTT) in 28 patients.

RESULTS

Three patients (10%) showed ITG and four DMRCF (13.3%). CF patients with impaired CHM (ICHM) were older (p = 0.006), and had longer times since diagnosis and first sputum colonization (p = 0.001, p < 0.001). Homozygous deltaF508 mutation was significant (p = 0.001). Insulin peak, area under the curve for insulin, insulin resistance, insulin sensitivity, and pancreatic beta-cell function were all significant.

CONCLUSIONS

ICHM was present in 23.3%. Age, time since diagnosis of CF, first sputum colonization and homozygous deltaF508 mutation were significantly associated. CHM in patients with CF is similar to that in the population without CF in the early years.

Liver disease as risk factor for cystic fibrosis-related diabetes development

AIM

To evaluate clinical and genetic factors, besides pancreatic insufficiency, associated with increased risk of cystic fibrosis-related diabetes.

METHODS

Case-control (1:1) study on 138 cystic fibrosis patients. Data were collected on gender, age at diagnosis, reason for cystic fibrosis diagnosis, family history of type 1 or 2 diabetes mellitus, pre-existing severe liver disease, and class of cystic fibrosis transmembrane regulation mutation. Moreover, information was obtained on lung involvement and degree of exocrine pancreatic insufficiency evaluated 1 year before the diagnosis of cystic fibrosis-related diabetes in patients and age-matched controls.

RESULTS

Compared to controls, patients with cystic fibrosis-related diabetes had a higher probability of having already been diagnosed with liver disease (16.7% versus 1.7%, OR = 11.6, 95% CI 1.43-93.0). Moreover, in the year before diabetes onset, cases had slightly worse pulmonary function compared to controls (FEV1 = 58.4 +/- 27% predicted versus 67.4 +/- 21% predicted; p = 0.05). No significant effects related to the other factors considered were found.

CONCLUSION

Severe liver disease was found to significantly increase the risk of developing cystic fibrosis-related diabetes. Patients with liver disease should be scheduled for earlier diabetes screening in order to identify and possibly treat glucose intolerance.

Clinical trials in cystic fibrosis

In patients with cystic fibrosis (CF), clinical trials are of paramount importance. Here, the current status of drug development in CF is discussed and future directions highlighted. Methods for pre-clinical testing of drugs with potential activity in CF patients including relevant animal models are described. Study design options for phase II and phase III studies involving CF patients are provided, including required patient numbers, safety issues and surrogate end point parameters for drugs, tested for different disease manifestations. Finally, regulatory issues for licensing new therapies for CF patients are discussed, including new directives of the European Union and the structure of a European clinical trial network for clinical studies involving CF patients is proposed.

[Digestive complications in adults with cystic fibrosis]

In France the median life expectancy of patients with cystic fibrosis (CF) is 36 years and one third of patients are adults. Respiratory disorders are the main determinants of survival during adulthood, although gastrointestinal complications can also have a major impact on quality of life and nutritional status. We reviewed gastro-intestinal and pancreatic manifestations of CF in adults. Some complications (diabetes, distal intestinal obstruction syndrome and acute pancreatitis) are more frequent in adulthood than in childhood. Clinical and therapeutic aspects of specific conditions (such as distal intestinal obstruction syndrome) or atypical presentations (including appendicular complications) are presented herein.

Continuous glucose monitoring in adolescents with cystic fibrosis

The presence of cystic fibrosis (CF)-related diabetes was evaluated in 19 adolescents with CF by continuous glucose monitoring system (CGMS) and oral glucose tolerance testing. CGMS confirmed diabetic glucose excursions in 7/19 subjects deemed diabetic on oral glucose tolerance testing. CGMS is a useful tool for detecting hyperglycemia in CF.

Asians with cystic fibrosis in the UK have worse disease outcomes than clinic matched white homozygous delta F508 controls

BACKGROUND

We tested the hypothesis that the Asian cystic fibrosis (CF) phenotype is comparable to the commonest genetic form of CF found in 50% of the white UK CF population using the UK CF Database, a national disease-specific patient registry.

METHODS

50 Asian CF patients were matched by Centre with 143 white homozygous delta F508 patients for gender, age and chronic Pseudomonas aeruginosa status (a marker of morbidity). The authors compared FEV1 and FVC% predicted, mean height, weight and BMI Z scores.

RESULTS

FVC% predicted, weight and BMI Z scores were significantly worse in the Asians. Asian male/female FVC% predicted (p-value, 95% CI) -15.1 (p=0.001, -24.0, -8.8)/-15.2 (p=0.014, -27.1, -3.3) compared with white controls. Asian females also had significantly worse FEV1% predicted compared with controls (-14.9, p=0.025, 95% CI: -27.8, -2.0). Asians had significantly lower raw Z scores for weight (males p=0.002, females p=0.013) and BMI (males p=0.002, females p=0.008).

CONCLUSIONS

These data suggest that the Asian CF phenotype is as severe as the white controls with the homozygous delta F508 phenotype but is worse in some outcomes, especially in Asian females. Socio-cultural factors and rare CF genotypes may contribute to the severity of CF in this vulnerable group.

Decreased lung function in female but not male subjects with established cystic fibrosis-related diabetes

OBJECTIVE

Although cystic fibrosis-related diabetes (CFRD) is associated with decreased lung function, sex is not known to influence CFRD. However, compared with male subjects with cystic fibrosis, female subjects with cystic fibrosis have increased morbidity. This study examines the association between female subjects with CFRD and poor lung function relative to male subjects using the percent predicted forced expiratory volume in 1 s (FEV(1)) as a surrogate measure of morbidity.

RESEARCH DESIGN AND METHODS

We compared 323 patients with established CFRD with 489 cystic fibrosis control subjects with normal glucose tolerance (NGT) listed in the U.K. Cystic Fibrosis Database. Patients stratified by sex and chronic Pseudomonas aeruginosa infection were compared using binary logistic regression, and patients with new CFRD diagnoses were compared prospectively for the year 2002.

RESULTS

CFRD in female subjects (but not male subjects) without chronic P. aeruginosa infection had a 20% lower percent predicted FEV(1) compared with control subjects with NGT (95% CI -11.7 to -27.7; P < 0.0001). Genotype, age, treatment center, age at diagnosis of cystic fibrosis, pregnancy, liver function, or dose of pancreatic enzyme replacement therapy did not confound this female disadvantage. Comparison of female subjects with newly diagnosed CFRD free of chronic P. aeruginosa infection with matched control subjects with NGT showed no FEV(1) disadvantage in the 1st year after CFRD diagnosis.

CONCLUSIONS

Only female subjects with CFRD have significantly decreased lung function compared with sex-matched NGT control subjects. The absence of poor lung function in the first 12 months after diagnosis of diabetes suggests that an opportunity may exist to intervene and possibly prevent a decline in lung function, which can be as much as 20% in female subjects with CFRD.

Diabetes: a major co-morbidity of cystic fibrosis

Cystic fibrosis-related diabetes (CFRD) is a frequent complication of cystic fibrosis, its prevalence increases with age of patient and is close to 30% at the age of 30 years. As life expectancy greatly increases, the number of cystic fibrosis patients developing diabetes will increase too. CFRD shares some features with type 1 and type 2 diabetes, initial phase is characterised by postprandial hyperglycaemia followed by a progression toward insulin deficiency. Insulin deficiency is an essential factor in the development of diabetes with an additional contribution of insulin resistance. Systematic screening with an oral glucose tolerance test is recommended from the age of 14 years because clinical signs of CFRD are often confused with signs of pulmonary infection and CFRD occurrence is associated with weight and pulmonary function deterioration. In observational studies CFRD diagnosis is associated with a significant increase in mortality, while treatment allow correction of weight and lung deterioration suggesting that CFRD has a significant impact on CF evolution. Microvascular complications are recognised, although paucity of data does not permit a clear description of their natural history. Annual screening for microvascular complication is recommended. There is no evidence by now that CF patients develop macrovascular complications. The only recommended pharmacological treatment is insulin therapy.

Clinical importance of cystic fibrosis-related diabetes

The prevalence of cystic fibrosis-related diabetes (CFRD) and glucose intolerance (IGT) has risen dramatically over the past 20 years as survival has increased for people with cystic fibrosis (CF). Diabetes is primarily caused by pancreatic damage, which reduces insulin secretion, but glucose tolerance is also modified by factors that alter insulin resistance, such as intercurrent illness and infection. CFRD not only causes the symptoms and micro and macrovascular complications seen in type 1 and type 2 diabetes in the general population, but also is associated with accelerated pulmonary decline and increased mortality. Pulmonary effects are seen some years before the diagnosis of CFRD, implying that impaired glucose tolerance may be detrimental. Current practice is to screen for changes in glucose tolerance by regular measurement of fasting blood glucose, by oral glucose tolerance test or a combination of these approaches with symptom review and measurement of HbA1C. Treatment is clearly indicated for those with CFRD and fasting hyperglycaemia to control symptoms and reduce complications. As nutrition is critical in people with CF to maintain body mass and lung function, blood glucose should be controlled in CFRD by adjusting insulin doses to the requirements of adequate food intake and not by calorie restriction. It is less clear whether blood glucose control will have clinical benefits in the management of patients with CFRD without fasting hyperglycaemia or with impaired glucose tolerance and further studies are required to establish the best treatment for this patient group.