HLA type, islet cell antibodies, and glucose intolerance in cystic fibrosis

Pancreatic islet autoantibodies and their association with glycemic status in cystic fibrosis patients: A comprehensive meta-analysis

BACKGROUND

The role of autoimmune beta-cell damage in cystic fibrosis-related glucose abnormalities remains unclear. This study evaluates the prevalence of pancreatic islet autoantibodies (AABs) by glycemic status and age, and assesses the risk of developing cystic fibrosis-related diabetes (CFRD) in people with cystic fibrosis (pwCF).

METHODS

A random-effects meta-analysis examined AABs against glutamic acid decarboxylase (GADA), insulin (IAA), islet cell (ICA), islet antigen-2 (IA-2A) and zinc transporter 8 (ZnT8A) in pwCF (CRD42023482663). Prevalence, odds ratios (OR), and 95 % confidence intervals (CI) were calculated with subgroup analyses by glycemic status and age.

RESULTS

Analysis of 20 studies (2229 pwCF) found an overall islet AAB positivity rate of 4 % (CI: 2-9 %) and multiple positivity at 1 % (CI: 0-11 %). IAA had the highest prevalence at 6 % (CI: 3-14 %), and ICA the lowest at 1 % (CI: 0-9 %). Islet AAB prevalence trended higher in CFRD than non-CFRD patients and in children than adults. CFRD was significantly associated with islet AAB positivity, notably for GADA (OR 4.63, CI: 3.42-6.28), ICA (OR 3.57, CI: 1.05-12.18), and IA-2A (OR 2.36, CI: 1.29-4.34). Any and multiple AAB positivity were similarly correlated to CFRD (OR 2.82, CI: 1.22-6.51 and OR 2.71, CI: 1.49-4.93).

CONCLUSIONS

Pancreatic islet AABs are present in 1-6 % of pwCF and increase the risk of CFRD by 2.36 to 4.63 times. While there's a suggested link, limited study quality and inconsistent testing warrant cautious interpretation. Further robust studies are needed to confirm these findings and improve screening strategies.

Continuous glucose monitoring systems for monitoring cystic fibrosis-related diabetes

BACKGROUND

Cystic fibrosis (CF) is one of the most common life-shortening autosomal-recessive genetic conditions with around 100,000 people affected globally. CF mainly affects the respiratory system, but cystic fibrosis-related diabetes (CFRD) is a common extrapulmonary co-morbidity and causes excess morbidity and mortality in this population. Continuous glucose monitoring systems (CGMS) are a relatively new technology and, as yet, the impact of these on the monitoring and subsequent management of CFRD remains undetermined.

OBJECTIVES

To establish the impact of insulin therapy guided by continuous glucose monitoring compared to insulin therapy guided by other forms of glucose data collection on the lives of people with CFRD.

SEARCH METHODS

We searched the Cochrane Cystic Fibrosis Trials Register, compiled from electronic database searches and handsearching of journals and conference abstract books. Date of latest search: 23 September 2021. We also searched the reference lists of relevant articles and reviews and online trials registries. Date of last search: 23 September 2021.

SELECTION CRITERIA

Randomised controlled studies comparing insulin regimens led by data from CGMS (including real-time or retrospective data, or both) with insulin regimens guided by abnormal blood glucose measurements collected through other means of glycaemic data collection in people with CFRD. Studies with a cross-over design, even with a washout period between intervention arms, are not eligible for inclusion due to the potential long-term impact of each of the interventions and the potential to compromise the outcomes of the second intervention.

DATA COLLECTION AND ANALYSIS

No studies were included in the review, meaning that no data were available to be collected for analysis.

MAIN RESULTS

Review authors screened 14 studies at the full-text stage against the review's inclusion criteria. Consequently, seven were excluded due to the study type being ineligible (not randomised), two studies were excluded due to their cross-over design, and two studies was excluded since the intervention used was not eligible and one was a literature review. One study in participants hospitalised for a pulmonary exacerbation is ongoing. Investigators are comparing insulin dosing via insulin pump with blood sugar monitoring by a CGMS to conventional diabetes management with daily insulin injections (or on an insulin pump if already on an insulin pump in the outpatient setting) and capillary blood glucose monitoring. The participants in the control arm will wear a blinded continuous glucose monitoring system for outcome assessment. In addition to this, one further study is still awaiting classification, and will be screened to determine whether it is eligible for inclusion, or is to be excluded, in an update of this review.

AUTHORS' CONCLUSIONS

No studies were included in the review, indicating that there is currently insufficient evidence to determine the impact of insulin therapy guided by CGMS compared to insulin therapy guided by other forms of glucose data collection on the lives of people with CFRD, nor on potential adverse effects of continuous glucose monitoring in this context. Randomised controlled studies are needed to generate evidence on the efficacy and safety of continuous glucose monitoring in people with CFRD. There is one relevant ongoing study that may be eligible for inclusion in a future update of this Cochrane Review, and whose results may help answer the review question.

HLA frequencies and associations in cystic fibrosis

Cystic fibrosis (CF) is classically attributed to the dysfunction of the single CF transmembrane conductance regulator gene. The incidence of human leukocyte antigen (HLA) polymorphisms in different CF-associated diseases raises the question of an unequal distribution of HLA genotypes in CF. This study aimed to evaluate HLA gene frequencies and possible associations in CF patients compared with a control population. Frequencies of HLA-DRB1, HLA-DQA1 and HLA-DQB1, performed by intermediate resolution typing using Luminex sequence-specific oligonucleotide, and epitope counts were similar in 340 CF patients when compared with 400 control subjects. In conclusion, HLA-DRB1, -DQA1 and -DQB1 do not seem to influence susceptibility to CF. Whether HLA plays a role in the severity of CF disease needs to be investigated.

Reduced levels of active GLP-1 in patients with cystic fibrosis with and without diabetes mellitus

Glucagon like peptide 1 (GLP-1) is an incretin hormone released as a bioactive peptide from intestinal L-cells in response to eating. It acts on target cells and exerts several functions as stimulating insulin and inhibiting glucagon. It is quickly deactivated by the serine protease dipeptidyl peptidase IV (DPP-IV) as an important regulatory mechanism. GLP-1 analogues are used as antidiabetic drugs in patients with type 2 diabetes. We served patients with cystic fibrosis (CF, n=29), cystic fibrosis related diabetes (CFRD, n=19) and healthy controls (n=18) a standardized breakfast (23 g protein, 25 g fat and 76 g carbohydrates) after an overnight fasting. Blood samples were collected before meal as well as 15, 30, 45 and 60 min after the meal in tubes prefilled with a DPP-IV inhibitor. The aim of the study was to compare levels of GLP-1 in patients with CF, CFRD and in healthy controls. We found that active GLP-1 was significantly decreased in patients with CF and CFRD compared to in healthy controls (p<0.01). However, levels in patients with CFRD tended to be lower but were not significantly lower than in patients with CF without diabetes (p=0.06). Total GLP-1 did not differ between the groups, which points to that the inactive form of GLP-1 is more pronounced in CF patients. The endogenous insulin production (measured by C-peptide) was significantly lower in patients with CFRD as expected. However, levels in non-diabetic CF patients did not differ from the controls. We suggest that the decreased levels of GLP-1 could affect the progression toward CFRD and that more studies need to be performed in order to evaluate a possible treatment with GLP-1 analogues in CF-patients.

Anti-GAD65 reactive peripheral blood mononuclear cells in the pathogenesis of cystic fibrosis related diabetes mellitus

OBJECTIVE

A role of autoreactive T cells for type 1 diabetes pathogenesis is considered crucial. In our pilot study we addressed if autoreactive mononuclear cells are present also in peripheral blood of patients with other specific forms of diabetes as cystic fibrosis related diabetes (CFRD).

METHODS

Cellular immune responses to a known beta-cell autoantigen (GAD65 and GAD65 derived peptides) were analysed by ELISPOT (IFN-gamma) and by protein microarray analysis in four patients suffering from CFRD, in four cystic fibrosis (CF) patients without diabetes, in eight type 1 diabetes patients (without CF) and in four healthy controls.

RESULTS

Response to the autoantigen GAD65 (protein and peptides) was observed in 7/8 patients suffering from CF and in all type 1 diabetes patients. Post-stimulation production of Th1 cytokines (IFN-gamma, TNF-beta) was observed in 2/4 CFRD, 1/4 CF patients and in 7/8 type 1 diabetes patients. All these patients carry prodiabetogenic HLA-DQ genotype. Th2- and Th3 type of cytokine pattern was observed in 2/4 CF patients. Production of IL-8 was observed in the third CFRD as well as in the third CF patient and in 1/8 type 1 diabetes patient and borderline production of this chemokine was also observed in 2/4 healthy controls. No reaction was observed in the other 2/4 healthy controls and in the fourth CFRD patient who carried a strongly protective genotype and did not produce autoantibodies. The most potent peptide of GAD65 was amino acids 509-528.

CONCLUSIONS

We consider our observations as a sign of a reaction directed against the self-antigen GAD65 that are closely connected to type 1 diabetes. In CF patients who do not develop diabetes autoreactive mechanisms are very probably efficiently suppressed by immune self-tolerance mechanisms. CFRD patients are a heterogenic group. To disclose those who may display features of autoimmune diabetes could have an impact for their therapy and prognosis.

Le diabète de la mucoviscidose chez l’adulte

Cystic fibrosis is an autosomal recessive disorder affecting about 1/3500 case in France. The disease, that affects all epithelia, is responsible for pulmonary tract infections but also pancreas, gut, liver and genital tract abnormalities. It is linked to CFTR gene mutations, inducing unusually high increase of sodium chloride in sweat, used to track down the illness. deltaF508 CFTR mutation, encountered in 70% of cases, is nearly always associated to pancreatic insufficiency with early-onset lung attack. Around 10% of cystic fibrosis cases, whatever the age, are complicated with partially insulinopenic diabetes, favored by pancreatic fibrosis, while one third of patients shows glucose intolerance. After 20 years old, one third of patients suffers from diabetes and one half after 30 years. Diabetes diagnosis is difficult, and requires the fulfillment of oral glucose tolerance test (OGTT). One glycemia greater or equal to 2 g/l, two hours after a 75 g glucose load, established diabetes diagnosis. Indeed, fasting blood glucose and glycated hemoglobin appear as poor diagnosis markers. Despite histological arguments in favor of the mainly mechanical islet disturbances, an increased prevalence of anti-islets auto-antibodies and an increased frequency of HLA DR3/DR4 have been reported in cystic fibrosis population with glucose tolerance troubles. Also, glucose metabolism is influenced by specific factors linked to cystic fibrosis (infection, malnutrition, steroids...). In reason of the silent phase of diabetes, systematic tracking down of diabetes with a yearly OGTT is recommended, all the more so that hyperglycemia appears as a worsening factor of cystic fibrosis. The efficacy of oral anti-diabetic drugs has not been evaluated on large studies. By contrast, some studies argue for insulin therapy as soon as diabetes appears, insulin improving respiratory and nutritional prognosis. In conclusion, the aim of treatment of cystic fibrosis is to prevent the lung function decline by controlling inflammation and infection, to implement endo- and exo-crine pancreas insufficiency, and to improve nutritional status.

Beta-cell autoantibodies and diabetes mellitus family history in cystic fibrosis

OBJECTIVE

To verify whether autoimmunity against beta-cells and family history of type 1 and/or type 2 diabetes mellitus (DM) play a role in the pathogenesis of cystic fibrosis (CF)-related diabetes mellitus (CFRD).

PATIENTS AND METHODS

The prevalence of beta-cell autoantibodies (GADA and IA-2A) was investigated in a group of patients with CF compared with patients with type 1 DM (DM1) and controls. Family history of DM1 and/or DM2 was investigated among patients with CF.

RESULTS

Frequency of beta-cell autoantibodies was significantly lower (p = 0.0001) in patients with CF with CFRD (IA-2A: 0%; GADA 12.5%) than in patients with DM1 (64.1% vs 52.8%, respectively) and it did not differ from the frequency in patients with CF without CFRD. Prevalence of family history for DM1 or DM2 was not significantly higher in CF patients with CFRD than in CF patients without CFRD.

CONCLUSIONS

The investigated factors did not show correlation with the pathogenesis of 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.

Cystic fibrosis-related diabetes

Diabetes mellitus (DM) has been recognized as a complication of cystic fibrosis (CF) for almost 50 years and commonly develops around 20 years of age. The prevalence increases with age and, with improved survival of those with CF, approaches 30% in certain centres. Its development appears to have a significant impact on pulmonary function and may increase mortality by up to six-fold. Subjects with CF are rarely ketosis-prone and phenotypically lie between Type 1 and Type 2 DM. Microvascular complications are recognized, although paucity of data does not permit a clear description of their natural history. An annual oral glucose tolerance test from the age of 10 years is recommended for screening, but logistical difficulties have led some groups to develop specific algorithms to aid diagnosis. Insulin sensitivity in CF is much debated and may depend upon the degree of glucose intolerance. Insulin resistance occurs in the presence of infection, corticosteroid usage and hyperglycaemia, whilst hepatic insulin resistance is considered an adaptation to CF. There is no universal consensus on the treatment of hyperglycaemia. With increased longevity of individuals with CF, greater numbers will develop diabetes and the diabetes physician is destined to play a greater role in the multidisciplinary CF team.

Relative increase in IgG antibodies to Pseudomonas aeruginosa 60-kDa GroEL in prediabetic patients with cystic fibrosis

In recent years research has focused on a possible connection between bacterial infection and development of diabetes mellitus. In this study, serum antibody responses against bacterial antigens in diabetic and nondiabetic patients with cystic fibrosis (CF) were evaluated. The first part of the study included 252 CF patients of whom 46 (18 %) had diabetes. This study showed that precipitating antibodies (precipitins) against Pseudomonas aeruginosa and other bacteria in crossed immunoelectrophoresis, and IgG antibodies against a 60-kD GroEL of P. aeruginosa, were highly variable and positively correlated with age. Patient material matched for age and sex showed no significant difference between diabetic and nondiabetic CF patients in precipitins or IgG antibodies to P. aeruginosa GroEL. Two longitudinal studies of 9 and 5 y using retrospectively selected sera from 29 prediabetic and 29 cross-matched nondiabetic CF patients were performed. As to precipitins against P. aeruginosa, we found no difference between the prediabetic and the nondiabetic group of patients during the study period. The study revealed, however, a significant increase of 24.6 % (p = 0.008) of IgG antibodies against P. aeruginosa 60-kD GroEL, 3-12 mo before the onset of diabetes in patients with CF, compared with an overall increase of 5 % to 6 % per year in both groups during the observation period. This study shows that diabetes in CF appears after a peak of serum IgG antibodies against GroEL and indicates that development of diabetes in CF patients may not only be caused by a progressive fibrosis of the pancreatic tissue, but may be augmented by a short-term specific immunologic reaction, initially triggered by an ongoing and progressive pulmonary infection.

Challenges in the dietary treatment of cystic fibrosis related diabetes mellitus

Cystic fibrosis related diabetes mellitus is an increasingly recognized problem as survival in patients with cystic fibrosis improves. In a 5 year retrospective study of 627 children and adults attending Toronto cystic fibrosis clinics, we identified 57 (9%) patients with cystic fibrosis related diabetes mellitus; four (1.3%) of 301 children (<18 years) and 53 (16%) of 326 adults. The development of this complication of cystic fibrosis is associated with increased mortality, deteriorations in both respiratory and nutritional status, and the development of late microvascular, but not macrovascular, diabetic complications. Unfortunately, systematic review of the literature provides few well designed studies that provide sound evidence for clinical practice. Recommendations are therefore often based on anecdote, rather than physiological or outcomes research. Dietary therapy combines the principles of the dietary management of both cystic fibrosis and diabetes mellitus, but emphasizes the need for a high energy diet (> 100% of recommended daily intake) in patients with cystic fibrosis related diabetes mellitus. The importance of calories from fat is emphasized, with no restriction on total carbohydrate intake. Insulin intake mirrors carbohydrate intake. Routine dietary therapy is straightforward, but challenges occur due to both complications of cystic fibrosis and advancing disease. If a patient with cystic fibrosis related diabetes mellitus is malnourished, overnight enteral tube feeding is often used, with an adjusted insulin regimen. There is a great need for both physiological and outcomes research to provide sound scientific evidence for the dietary treatment of cystic fibrosis related diabetes mellitus.

Islet autoantibodies and insulin dependent diabetes mellitus in cystic fibrosis

Cystic fibrosis-related diabetes mellitus (CF-DM) is thought to be secondary to beta-cell destruction by fibrous tissue replacing the exocrine pancreas. The aim of this study was to investigate the hypothesis that other factors may also be responsible. Glutamic acid decarboxylase (GAD) and islet cell (IA-2) antibodies were measured by quantitative ELISA in a group of patients with CF (n=30) in comparison to a group of newly diagnosed DM type 1 (IDDM) patients (n=30) and normal subjects (n=30). GAD antibodies were positive (>32 ng/ml) in 50% of the CF, 93% of the IDDM and 0% of the control group. IA-2 antibodies were detected (>0.9 U/ml) in 40% of the CF, 93% of the IDDM and 0% of the control group. Among the fifteen CF patients with positive GAD and IA-2 antibodies, four already had IDDM and another five abnormally low (<45 mU/l) first phase insulin response (FPIR) indicating a prediabetic state. We conclude that factors other than mechanical may be involved in the development of CFDM. The presence of autoantibodies predicting IDDM supports the hypothesis that CF-DM may have a multifactorial pathogenesis.

The major histocompatibility complex influences the development of chronic liver disease in male children and young adults with cystic fibrosis

BACKGROUND/AIMS

Chronic liver disease is a well-recognised complication of cystic fibrosis. Recent reports suggest that its development is not determined by specific mutations within the cystic fibrosis gene; however, familial clustering of portal hypertension cases and inappropriate immune responses against liver membrane antigens demonstrated in children with cystic fibrosis and chronic liver disease suggest that other genetic loci may be relevant. As the major histocompatibility complex has an important immunoregulatory role, we have investigated for associations with this complex and chronic liver disease in cystic fibrosis.

METHODS

We have determined human leucocyte antigen class I (A and B) and class II (DR) phenotypes by serological tissue typing and class II (DR and DQ) and class III (complement component C4 and 21-hydroxylase) gene polymorphisms in 274 children and young adults with cystic fibrosis, of whom 82 had evidence of chronic liver disease with portal hypertension in 49, and 146 healthy controls.

RESULTS

A marked difference in human leucocyte antigen frequency was limited to DQ6, which was found in 66.7% of cystic fibrosis patients with liver disease compared to 32.9% of patients with no liver disease (Pc < 0.03) and 28.8% of controls (Pc < 0.006). An increased frequency of the two antigens in strong linkage disequilibrium with DQ6 was also observed within this patient group, namely DR15 and B7. When the patients were stratified for the presence of portal hypertension, these observations were confirmed, but the human leucocyte antigen associations were significant only for male patients and there was no association with the age of onset of liver disease.

CONCLUSIONS

These data suggest that the haplotype B7-DR15-DQ6 may carry an increased risk of development of liver disease in male cystic fibrosis patients.

Proinsulin, proinsulin intermediate and insulin in cystic fibrosis

OBJECTIVE

We determined the changes in insulin, intact proinsulin and 32-33 split proinsulin as markers of beta cell damage in assessing the state of carbohydrate intolerance in patients with cystic fibrosis.

DESIGN

Measurements of insulin, proinsulin and 32-33 proinsulin concentrations in cystic fibrosis following oral glucose tolerance test (OGTT).

SUBJECTS

Sixteen cystic fibrosis patients attending the chest outpatient clinic for follow-up, age range 14-42 years, and 14 healthy controls matched for age and body mass index.

MEASUREMENTS

Insulin, intact proinsulin and 32-33 split proinsulin were measured immunoradiometrically at 0, 30, 60, 90 and 120 minutes after an OGTT. Glucose and HbA1 were also measured.

RESULTS

Cystic fibrosis patients were divided into two groups according to their OGTT results: those with diabetes mellitus or impaired glucose tolerance and those with normal glucose tolerance. Insulin concentrations and insulin/glucose ratios at 30 minutes were lower in both cystic fibrosis groups in comparison with the control. There was also a significant increase in the time to reach peak insulin levels in both cystic fibrosis groups. Fasting intact proinsulin concentrations and the proportion of proinsulin-like molecules were significantly higher in cystic fibrosis with diabetes mellitus or impaired glucose tolerance than in the control group, but not in the normal glucose tolerance cystic fibrosis group. There was no significant difference in the plasma concentrations of 32-33 split proinsulin amongst the three groups.

CONCLUSIONS

Abnormal beta cell function in cystic fibrosis patients was reflected initially in a diminished 30-minute insulin response to oral glucose. A significant rise in fasting intact proinsulin and the proportion of proinsulin-like molecules was seen only in cystic fibrosis patients who had progressed to impaired glucose tolerance or diabetes mellitus. Cystic fibrosis patients with normal glucose tolerance showed changes intermediate between the control and the other group.

Diabetes and its complications may be caused by inadequate circulation. A new concept

Students of diabetes have noted that the so-called vascular complications of the disease appear with little or no consistency. Uncontrolled patients may have no vascular problems. Contrarywise obsessive compulsive individuals who follow every dietary regimen perfectly and take their prescriptions faithfully may have horrendous vascular difficulties. These experiences brought me to the conclusion that the 'complications' were really a component of the disease rather than the result of it. In an effort to find a unified concept of the disease it seemed reasonable to conclude that inadequate circulation to the islets may be a cause of the chemical constellation that we call diabetes. Vascular pathology may appear haphazardly in various arteries. Thus some will develop cerebrovascular disease, others coronary manifestations while still other patients will experience peripheral vascular symptoms. Is it not possible that defective circulation to the pancreas might be an aetiological factor in the development of diabetes? These observations lend credence to the concept that arterial pathology may actually precede the appearance of clinical diabetes.

Longitudinal evaluation of glucose tolerance and insulin secretion in non-diabetic children and adolescents with cystic fibrosis: results of a two-year follow-up

Thirty-two patients with cystic fibrosis and repeatedly normal fasting blood glucose underwent oral glucose tests and islet-cell antibody assessments on two occasions approximately two years apart. Fourteen patients underwent two iv glucose tolerance tests also. Although in the group as a whole mean glucose areas in response to the oral test remained substantially unmodified over the two-year period, the prevalence of glucose tolerance abnormalities increased from 37.5 to 50%. Insulin output in response to both oral and iv tolerance tests decreased over time. Worsening of insulin secretion and/or of glucose tolerance was never accompanied by deteriorating clinical status. Islet-cell antibodies were detected in no patients, even in those who developed a diabetic glucose tolerance. These results support, on a longitudinal basis, the view of a progressive impairment of B-cell function in cystic fibrosis, which may precede the onset of metabolic abnormalities and is not triggered by autoimmunity.

Diabetes mellitus in cystic fibrosis: genetic and immunological markers

Family history, as well as genetic and immunological markers of diabetes mellitus, were studied in cystic fibrosis (CF) patients with and without diabetes mellitus. Positive family history of diabetes mellitus in first-degree relatives was found in only 6 of 210 (3%) CF patients, with no difference between non-diabetic and diabetic patients. The frequency distributions of the HLA types DR3, DR4 and DR3/4, which normally confer susceptibility to insulin-dependent diabetes mellitus and of HLA-DR2, which normally confers resistance to insulin-dependent diabetes mellitus, were not different in non-diabetic CF patients, diabetic CF patients and normal subjects. The genotypic frequencies of tumor necrosis factor-beta and of heat shock protein 70, located within the HLA region on chromosome 6, in CF patients with diabetes were not different from those in patients with insulin-dependent diabetes mellitus, while non-diabetic CF patients and normal subjects shared other patterns. The frequencies of the interleukin-1 beta alleles, located on chromosome 2, were not different in non-diabetic and diabetic CF patients, insulin-dependent diabetic patients and normal subjects. Islet cell cytoplasmic antibodies, measured before, at and after the diagnosis of diabetes in 33 diabetic CF patients and in 32 matched non-diabetic CF patients, were detected in only 2 of 236 (0.8%) serum samples: in a pre-diabetic patient and in a non-diabetic control patient. Birth weights were not different in diabetic and non-diabetic CF patients, arguing against the importance of the intrauterine environment as a determinant in the transmission of diabetes mellitus in CF patients.(ABSTRACT TRUNCATED AT 250 WORDS)

Diabetes mellitus and cystic fibrosis

There is a high prevalence of diabetes mellitus in patients with CF and this is likely to increase in the future as more patients are surviving into adult life. In view of this all CF clinics should routinely screen for diabetes mellitus. The prevalence of diabetes mellitus in adult CF patients is higher than in children, and the onset is commonly insidious. The diabetes seen in CF is not classical Type 1 diabetes or Type 2 diabetes and could more helpfully be called cystic fibrosis-related diabetes (CFRD). Treatment is by oral hypoglycaemic agents or insulin. It is not appropriate to control patients by diet alone. Dietary advice to CF diabetic patients is not the same as that given to non-CF diabetic patients. Microvascular complications have now been reported and careful monitoring of all CF patients with diabetes should be undertaken.

Pancreatic morphology and function in adult patients with cystic fibrosis

To determine the relation between pancreatic morphology and pancreatic exocrine and endocrine function, we have studied 8 adult cystic fibrosis patients and 14 normal control subjects by ultrasonography and pancreatic function testing. In the patients with cystic fibrosis the maximum anteroposterior diameter of the pancreatic head was significantly increased over that in control subjects (p less than 0.01), whereas the maximum diameter of the body was significantly decreased (p = 0.05). Increased echogenicity of the pancreatic body was observed in most patients. In the cystic fibrosis patients postprandial insulin secretion was reduced in the 1st h (p less than 0.005 versus control), whereas pancreatic polypeptide secretion was virtually abolished for at least 3 h (p less than 0.01 versus control). All cystic fibrosis patients had evidence of exocrine pancreatic dysfunction as reflected by a diminished urinary para-aminobenzoic acid excretion. Intraduodenal enzyme and bicarbonate output in response to secretin-cholecystokinin was reduced in all of three patients studied. It is concluded that loss of endocrine and exocrine pancreatic function in adult cystic fibrosis patients is accompanied by a small and echo-dense pancreatic body relative to a large pancreatic head.

Islet cell cytoplasmic antibodies (ICA) in diabetes and disorders of glucose tolerance

Islet cell cytoplasmic antibodies were determined in 85 individuals 60 to 74 years old with fasting hyperglycaemia, in 65 patients with cystic fibrosis, in 113 patients with pancreatitis, in 21 patients with Turner's phenotype, and in 135 first-degree relatives of patients with Type 1 (insulin-dependent) diabetes. Islet cell antibodies were absent in all 60 to 74-year-old subjects with fasting hyperglycaemia detected by screening, and who did not require insulin treatment within 3 years. Islet cell antibodies were also absent in all patients with pancreatitis, cystic fibrosis, or Turner's phenotype. Islet cell antibodies were detected in 2 out of 135 (1.5%) first-degree relatives of new Type 1 diabetic patients, and in 1 out of 371 (0.3%) non-diabetic control subjects. During 12 years of follow-up 1 of the 2 first-degree relatives with islet cell antibodies and the only positive control developed Type 1 diabetes. It is suggested that islet cell antibodies are primarily associated with Type 1 diabetes and not with other disorders of glucose tolerance.