Glucose homeostasis and genotype-phenotype interplay in cystic fibrosis patients with CFTR gene deltaF508 mutation

Novel time-saving OGTT sparing HbA1c-HOMA2 based algorithm for the diagnosis of cystic fibrosis-related diabetes

AIMS

The diagnosis of cystic fibrosis-related diabetes (CFRD) faces several challenges. We propose a novel screening algorithm to alleviate the burden of cystic fibrosis (CF).

METHODS

Through a retrospective cross-sectional single-centre study, HbA1c and HOMA2 indices were assessed in multiple models as alternative diagnostic tools from OGTT data. We sought to establish specific thresholds for CFRD screening with oral glucose tolerance test (OGTT) as gold standard. We evaluated various straightforward or sequential approaches, in terms of diagnostic accuracy while also quantify the potential reduction in OGTTs through these different methods.

RESULTS

HOMA indices were recovered in 72 patients. We devised a composite index that combines HbA1c and HOMA-B: Diabetes Predicting Index in cystic fibrosis (DIPIc) = (HbA1c(%) × 3.455) - (HOMA-B(%) ×  0.020) - 19.294. This index yields the highest screening accuracy according to receiver-operating characteristics curves. Using a stepwise algorithm that incorporates DIPIc decreases the requirement for annual OGTTs. A CFRD exclusion cutoff less than -1.7445 (sensitivity 98 %), in conjunction with a CFRD diagnostic threshold greater than 0.4543 (specificity 98 %) allows for 71 % OGTT sparing.

CONCLUSION

The composite index DIPIc is a suitable, less invasive screening method for CFRD, which enables to avoid many OGTTs.

Advances in cystic fibrosis-related diabetes: Current status and future directions

AIMS

The aim of this review is to give an update of the recent advances in the pathophysiology, prognosis, diagnosis and treatments of cystic fibrosis-related diabetes (CFRD).

METHODS

The literature survey focuses on original and review articles dealing with CFRD between 2006 and 2023, and in particular with: pathophysiology, risk and predictive factors, screening, chronic complications of CFRD, management and the effects of CFTR channel modulator therapies on glucose homeostasis, using PubMed®.

RESULTS

The rising prevalence of CFRD is due to prolonged life survival among patients with cystic fibrosis (CF). Advances in the understanding of the pathophysiology highlight the singularity of CFRD. Adherence to diagnostic guidelines remains challenging. Besides the classical OGTT, alternative diagnostic tests are being considered: HbA1c measurement, continuous glucose monitoring (CGM), intermediate measurements of alternative glucose tolerance stages through OGTT and homeostatic model assessment (HOMA). Early treatment of (pre)diabetes in CF patients is mandatory. The advent of CFTR channel modulator therapies have created a paradigm shift in the management of CF: they seem to improve glucose homeostasis, but the mechanism remains unclear.

CONCLUSION

CFRD management is an ongoing concern. Optimal care has reduced the negative impact of CFRD on lung function, nutrition, and survival. Increasing prevalence of CFRD and prolonged lifespan lead to more microvascular complications. New screening tools (Hba1c, CGM, HOMA) show potential for better classification of patients. The effect of CFTR modulators on glucose metabolism warrants further research.

Combined CFTR modulator therapies are linked with anabolic benefits and insulin-sparing in cystic fibrosis-related diabetes

Aims

Combined CFTR modulator therapies have dramatically altered pulmonary outcomes in patients with cystic fibrosis (CF). Their impact on glucose metabolism requires further investigations. This study aims to evaluate insulin requirements after initiation of combined CFTR modulator therapy in patients with CF-related diabetes (CFRD) and HOMA indices changes in CF patients without diabetes.

Methods

We retrospectively analyzed: 1) the effects of tezacaftor + ivacaftor and elexacaftor + tezacaftor + ivacaftor on FEV₁, weight, BMI, HbA1c, and daily insulin dose, in 17 CFRD patients and 2) the impact of tezacaftor + ivacaftor on HOMA indices in 15 CF patients without diabetes.

Results

Age was 37±12y in the CFRD group (70% men), 88% of whom were homozygous for F508del mutation. Diabetes duration was 15±10y. Median duration of combined CFTR modulator therapy was 16 months (IQR: 4) Thirteen patients received tezacaftor + ivacaftor, of whom 9 were switched to elexacaftor + tezacaftor + ivacaftor. Four patients received elexacaftor + tezacaftor + ivacaftor up front. A decrease in insulin needs was noticed in 88% of patients (0.85±0.3 vs 0.71±0.3U/kg/day; p = 0001). Total daily insulin dose decreased from 50±16 to 44±20U/day (p = 0.017). BMI improved (20.9 (IQR: 1.90) vs 22.1 kg/m² (IQR: 3.70); p = 0.014). HbA1c went from 7.3±1.1 to 7.7±1.6% (p = 0.072). Median age was 22y (IQR: 11) in the CF group without diabetes (67% men), 93% of whom were homozygous for F508del mutation. Duration of combined CFTR modulator therapy was 10±5 months. HOMA-B changes were not significant (129.2 (IQR: 84.8) vs 103.5% (IQR: 66.3) nor were HOMA-S changes (from 94±64 to 95±49%). HOMA-BxS decreased from 112±45 to 104±29% (NS). BMI rose from 21.9±3 to 23.1±3.5 kg/m² (p = 0.047). HbA1c was unchanged (5.0±0.5%). FEV₁ improved in both groups (+11% and + 7% of predicted value; p < 0.001; p = 0.013).

Conclusion

Combined CFTR modulator therapies are correlated with a decrease in insulin doses and positive effects on BMI and FEV₁. HOMA indices did not change on tezacaftor + ivacaftor among CF patients without diabetes.

Sweat Proteomics in Cystic Fibrosis: Discovering Companion Biomarkers for Precision Medicine and Therapeutic Development

In clinical routine, the diagnosis of cystic fibrosis (CF) is still challenging regardless of international consensus on diagnosis guidelines and tests. For decades, the classical Gibson and Cooke test measuring sweat chloride concentration has been a keystone, yet, it may provide normal or equivocal results. As of now, despite the combination of sweat testing, CFTR genotyping, and CFTR functional testing, a small fraction (1–2%) of inconclusive diagnoses are reported and justifies the search for new CF biomarkers. More importantly, in the context of precision medicine, with a view to early diagnosis, better prognosis, appropriate clinical follow-up, and new therapeutic development, discovering companion biomarkers of CF severity and phenotypic rescue are of utmost interest. To date, previous sweat proteomic studies have already documented disease-specific variations of sweat proteins (e.g., in schizophrenia and tuberculosis). In the current study, sweat samples from 28 healthy control subjects and 14 patients with CF were analyzed by nanoUHPLC-Q-Orbitrap-based shotgun proteomics, to look for CF-associated changes in sweat protein composition and abundance. A total of 1057 proteins were identified and quantified at an individual level, by a shotgun label-free approach. Notwithstanding similar proteome composition, enrichment, and functional annotations, control and CF samples featured distinct quantitative proteome profiles significantly correlated with CF, accounting for the respective inter-individual variabilities of control and CF sweat. All in all: (i) 402 sweat proteins were differentially abundant between controls and patients with CF, (ii) 68 proteins varied in abundance between F508del homozygous patients and patients with another genotype, (iii) 71 proteins were differentially abundant according to the pancreatic function, and iv) 54 proteins changed in abundance depending on the lung function. The functional annotation of pathophysiological biomarkers highlighted eccrine gland cell perturbations in: (i) protein biosynthesis and trafficking, (ii) CFTR proteostasis and membrane stability, and (iii) cell-cell adherence, membrane integrity, and cytoskeleton crosstalk. Cytoskeleton-related biomarkers were of utmost interest because of the consistency between variations observed here in CF sweat and variations previously documented in other CF tissues. From a clinical stance, nine candidate biomarkers of CF diagnosis (CUTA, ARG1, EZR, AGA, FLNA, MAN1A1, MIA3, LFNG, SIAE) and seven candidate biomarkers of CF severity (ARG1, GPT, MDH2, EML4 (F508del homozygous), MGAT1 (pancreatic insufficiency), IGJ, TOLLIP (lung function impairment)) were deemed suitable for further verification.

Oral Glucose Tolerance Test in Patients with Cystic Fibrosis Compared to the Overweight and Obese: A Different Approach in Understanding the Results

(1) Background: In cystic fibrosis (CF), the oral glucose tolerance test (OGTT) is recommended from 10 years old annually to screen and diagnose cystic fibrosis-related diabetes (CFRD). Alternative OGTT characteristics (glucose curve shape, time to glucose peak, one-hour glucose value, and three-hour glucose value with the new shape curve) were studied in other populations considered at high risk for diabetes; (2) Methods: The study analyses classical and alternative OGGT characteristics from 44 children (22 CF, 22 obese without CF), mean age: 12.9 ± 2.2 years evaluated in a single-center from Romania. (3) Results: In 59.1% of children with CF, the predominant OGTT pattern was: abnormal glucose metabolism or CFRD, with a monophasic curve shape, a late peak glucose level, and 1 h glucose ≥ 155 mg/dL, showing a very different pattern compared with sex and age-matched obese children. Statistical estimation agreement between the late glucose peak (K = 0.60; p = 0.005), the 1 h glucose ≥ 155 mg/dL during OGTT (K = 0.69, p = 0.001), and the classical method of interpretation was found. (4) Conclusions: Late peak glucose and 1 h glucose level ≥ 155 mg/dL during OGTT can be used for diagnosing the early glucose metabolism alteration in children with CF.

Cystic Fibrosis-Related Diabetes (CFRD): Overview of Associated Genetic Factors

Cystic fibrosis (CF) is the most common autosomal recessive disease in the Caucasian population and is caused by mutations in the CF transmembrane conductance regulator (CFTR) gene that encodes for a chloride/bicarbonate channel expressed on the membrane of epithelial cells of the airways and of the intestine, as well as in cells with exocrine and endocrine functions. A common nonpulmonary complication of CF is cystic fibrosis-related diabetes (CFRD), a distinct form of diabetes due to insulin insufficiency or malfunction secondary to destruction/derangement of pancreatic betacells, as well as to other factors that affect their function. The prevalence of CFRD increases with age, and 40–50% of CF adults develop the disease. Several proposed hypotheses on how CFRD develops have emerged, including exocrine-driven fibrosis and destruction of the entire pancreas, as well as contrasting theories on the direct or indirect impact of CFTR mutation on islet function. Among contributors to the development of CFRD, in addition to CFTR genotype, there are other genetic factors related and not related to type 2 diabetes. This review presents an overview of the current understanding on genetic factors associated with glucose metabolism abnormalities in CF.

Glucose tolerance & insulin secretion & sensitivity characteristics in Indian children with cystic fibrosis: A pilot study

Background & objectives

Cystic fibrosis (CF) is a life-limiting genetic condition resulting in chronic respiratory infections, pancreatic enzyme insufficiency and associated complications. This pilot study was undertaken to assess the glucose tolerance and insulin secretion and sensitivity among Indian children with CF.

Methods

Children with CF under regular follow up at the Paediatric Pulmonology Clinic of a tertiary care hospital in New Delhi, India, were enrolled. Children who had a history of acute exacerbation or intake of systemic steroids within the last two weeks were excluded. Anthropometry, pulmonary function and disease severity (Shwachman) score were assessed. Fasting venous sample was drawn to assess glucose, insulin, haemoglobin and calcium. Oral glucose tolerance test was performed, and blood glucose and insulin were assessed at 30, 60, 90 and 120 min. Insulin secretion and sensitivity indices were calculated.

Results

Twenty nine patients with a mean age of 11.2±4.1 yr were enrolled. Stunting, thinness, anaemia and hypocalcaemia were present in 31.0, 13.8, 37.0 and 48.3 per cent of the patients, respectively. Abnormal glucose tolerance (AGT) was present in 21.4 per cent. Insulin secretion was similar in individuals with AGT and normal glucose tolerance (NGT), but insulin sensitivity index was lower (0.12±0.02 vs 0.15±0.01, P<0.001) and homeostatic model assessment of insulin resistance higher [1.63 (0.53-1.76) vs 0.83 (0.28-4.43), P<0.05] in individuals with AGT compared to NGT.

Interpretation & conclusions

AGT was observed in 21.4 per cent of children with CF. The CF patients with AGT had significantly lower insulin sensitivity compared to patients with NGT. Future multicentric studies with a large sample should be conducted to assess insulin secretion and sensitivity indices in CF patients compared to healthy controls.

Cystic Fibrosis Related Diabetes: a Unique Challenge in Diabetes Care

Cystic Fibrosis (CF) is a common autosomal recessive disease that affects multiple organs due to a defect in the gene encoding the cystic fibrosis transmembrane conductance regulator (CFTR). This transporter is present in various organs and tissues, including the airway epithelium, sinuses, pancreas, intestine, biliary tree, the vas deferens, and the sweat ducts, making CF a multi-system disease1. As CF patients are living longer, pancreatic function declines and diabetes emerges, further complicating the nutritional status and care of these patients.

Post-Bariatric Surgery Changes in Quinolinic and Xanthurenic Acid Concentrations Are Associated with Glucose Homeostasis

Background

An increase of plasma kynurenine concentrations, potentially bioactive metabolites of tryptophan, was found in subjects with obesity, resulting from low-grade inflammation of the white adipose tissue. Bariatric surgery decreases low-grade inflammation associated with obesity and improves glucose control.

Objective

Our goal was to determine the concentrations of all kynurenine metabolites after bariatric surgery and whether they were correlated with glucose control improvement.

Design

Kynurenine metabolite concentrations, analysed by liquid or gas chromatography coupled with tandem mass spectrometry, circulating inflammatory markers, metabolic traits, and BMI were measured before and one year after bariatric surgery in 44 normoglycemic and 47 diabetic women with obesity. Associations between changes in kynurenine metabolites concentrations and in glucose control and metabolic traits were analysed between baseline and twelve months after surgery.

Results

Tryptophan and kynurenine metabolite concentrations were significantly decreased one year after bariatric surgery and were correlated with the decrease of the usCRP in both groups. Among all the kynurenine metabolites evaluated, only quinolinic acid and xanthurenic acid were significantly associated with glucose control improvement. The one year delta of quinolinic acid concentrations was negatively associated with the delta of fasting glucose (p = 0.019) and HbA1c (p = 0.014), whereas the delta of xanthurenic acid was positively associated with the delta of insulin sensitivity index (p = 0.0018).

Conclusion

Bariatric surgery has induced a global down-regulation of kynurenine metabolites, associated with weight loss. Our results suggest that, since kynurenine monoxygenase diverts the kynurenine pathway toward the synthesis of xanthurenic acid, its inhibition may also contribute to glucose homeostasis.

An in silico framework for integrating epidemiologic and genetic evidence with health care applications: ventilation-related pneumothorax as a case illustration

OBJECTIVE

To illustrate an in silico integration of epidemiologic and genetic evidence that is being developed at the Center for Devices and Radiological Health/US Food and Drug Administration as part of regulatory research on postmarket device performance. In addition to using conventional epidemiologic evidence from registries, this innovative approach explores the vast potential of open-access omics databases for identifying genetic evidence pertaining to devices.

MATERIAL AND METHODS

A retrospective analysis of Agency for Healthcare Research and Quality (AHRQ)/Healthcare Cost and Utilization Project (HCUPNet) data (2002-2011) was focused on the ventilation-related iatrogenic pneumothorax (Vent-IP) outcome in discharges with mechanical ventilation (MV) and continuous positive airway pressure (CPAP). The derived epidemiologic evidence was analyzed in conjunction with pre-existing genomic data from Gene Expression Omnibus/National Center for Biotechnology Information and other databases.

RESULTS

AHRQ/HCUPNet epidemiologic evidence showed that annual occurrence of Vent-IP did not decrease over a decade. While the Vent-IP risk associated with noninvasive CPAP comprised about 0.5%, the Vent-IP risk due to longer-term MV reached 2%. Along with MV posing an independent risk for Vent-IP, female sex and white race were found to be effect modifiers, resulting in the highest Vent-IP risk among mechanically ventilated white females. The Vent-IP risk was also potentiated by comorbidities associated with spontaneous pneumothorax (SP) and fibrosis. Consistent with the epidemiologic evidence, expression profiling in a number of animal models showed that the expression of several collagens and other SP/fibrosis-related genes was modified by ventilation settings.

CONCLUSION

Integration of complementary genetic evidence into epidemiologic analysis can lead to a cost- and time-efficient discovery of the risk predictors and markers and thus can facilitate more efficient marker-based evaluation of medical product performance.

The ΔF508 Mutation in the Cystic Fibrosis Transmembrane Conductance Regulator Is Associated With Progressive Insulin Resistance and Decreased Functional β-Cell Mass in Mice

Cystic fibrosis (CF) is the result of mutations in the cystic fibrosis transmembrane conductance regulator (CFTR). CF-related diabetes affects 50% of adult CF patients. How CFTR deficiency predisposes to diabetes is unknown. Herein, we examined the impact of the most frequent cftr mutation in humans, deletion of phenylalanine at position 508 (ΔF508), on glucose homeostasis in mice. We compared ΔF508 mutant mice with wild-type (WT) littermates. Twelve-week-old male ΔF508 mutants had lower body weight, improved oral glucose tolerance, and a trend toward higher insulin tolerance. Glucose-induced insulin secretion was slightly diminished in ΔF508 mutant islets, due to reduced insulin content, but ΔF508 mutant islets were not more sensitive to proinflammatory cytokines than WT islets. Hyperglycemic clamps confirmed an increase in insulin sensitivity with normal β-cell function in 12- and 18-week-old ΔF508 mutants. In contrast, 24-week-old ΔF508 mutants exhibited insulin resistance and reduced β-cell function. β-Cell mass was unaffected at 11 weeks of age but was significantly lower in ΔF508 mutants versus controls at 24 weeks. This was not associated with gross pancreatic pathology. We conclude that the ΔF508 CFTR mutation does not lead to an intrinsic β-cell secretory defect but is associated with insulin resistance and a β-cell mass deficit in aging mutants.

Nutrional status and dietary factors in cystic fibrosis patients with delta F508 mutation

Objective To examine the association between nutritional status and dietary factors in children and adolescents with cystic fibrosis that are carriers of delta F508 mutation. Methods Cross-sectional study of cystic fibrosis children and adolescents. Nutritional status (body mass index percentile) and dietary intake (3-day diet records presented as a percentage of estimated energy requirement) were assessed. Results Thirty six patients (median of 8.6; interquartile range 6.8-12.5 years; 50% male). The Poisson regression analysis showed that the carriers for delta F508 mutation had 60% lower prevalence ratio of body mass index ≥25° (PR=0.4; 95%IC=0.2-0.8) and 90% lower prevalence ratio (PR=0.1; confidence interval 95%IC=0.02-0.3) of ≥150% of estimated energy requirement when compared with non-delta F508 mutation carriers. The model was adjusted for lung function, estimated energy requirement, and body mass index. Conclusion Carriers for delta F508 mutation showed lower body mass index percentile and lower daily caloric consumption when compared with patients without this mutation.

Insulin secretion abnormalities in exocrine pancreatic sufficient cystic fibrosis patients

BACKGROUND

The aim of this study is to assess insulin secretion in pediatric cystic fibrosis (CF) patients with exocrine pancreatic sufficiency.

METHODS

Glucose and insulin responses during an oral glucose tolerance test (OGTT) were measured in 146 CF patients. Patients were divided into exocrine sufficient (CF-PS) and insufficient (CF-PI) groups based on pancreatic enzyme usage and fecal elastase. A reference group included healthy, non-diabetic subjects.

RESULTS

All CF groups showed reduced insulin secretion as measured by insulinogenic index. The CF-PS patients had normal glucose tolerance. There was a direct correlation between BMI z-score and insulin area under the curve.

CONCLUSION

Patients with CF have reduced insulin secretion during an OGTT regardless of exocrine pancreatic status. The abnormal insulin secretion in all CF patients may predispose them for glucose intolerance, particularly when challenged by inflammation, infection, or nutritional deficiency. In addition, the diminished insulin secretion may contribute to increased catabolism. Lastly, the CF-related diabetes (CFRD) screening guidelines should be followed by all CF patients regardless of pancreatic status.

Influence of macrolides, nutritional support and respiratory therapies in diabetes and normal glucose tolerance in cystic fibrosis. A retrospective analysis of a cohort of adult and younger patients

AIM

The development of cystic fibrosis related diabetes is associated with increased morbidity and mortality, worse nutritional status and lung function decline. It is known that patients with cystic fibrosis have a chronic inflammation status and that β pancreatic cells are very sensitive to oxidative stress. So these inflammatory mediators could contribute to the onset of progressive pancreatic fibrosis and, hence, to impair glucose metabolism. So, it could be hypothesized that the treatment with macrolides would protect and preserve β-cell function by decreasing pro-inflammatory cytokines and free oxidative radicals.

METHODS

We retrospectively analyzed a cohort of 64 patients affected of cystic fibrosis, older than 14 years, by using the first pathological 2-h oral glucose tolerance test; peripheral insulin resistance was calculated using the homeostasis model assessment for insulin resistance (HOMA - IR) and pancreatic β-cell function was estimated according to Wareham. The influence of macrolides, microbiological colonization, nutritional support and related clinical parameters were analyzed.

RESULTS

Comparing CFRD without FPG and NGT, and after adjustment for microbial colonization, the significance of the use of macrolides was lost (p=0.1), as a risk or protective factor for any of the studied groups. Non-significative associations were found in the use of macrolides, inhaled corticosteroids and nutritional support therapies within the different disorders of carbohydrate metabolism.

CONCLUSIONS

The anti-inflammatory and immunomodulating effect of macrolides did not seem to affect the β cell function or insulin resistance in patients with cystic fibrosis. The use of inhaled corticosteroids or nutritional supplements have not any influence in the carbohydrate metabolism. Further prospective studies are needed to analyze a potential protective role of macrolides in the development of carbohydrate metabolism alterations in cystic fibrosis.

Diabetes mellitus and survival in cystic fibrosis patients after lung transplantation

BACKGROUND

Diabetes mellitus (DM) is common in CF and associated with more severe disease. It is unclear whether DM influences outcome of lung transplantation (LTx).

METHODS

One hundred twenty-three CF patients evaluated for LTx at our centre were included. Survival was calculated.

RESULTS

Patients with and without DM did not differ with regard to gender, age, FEV(1) and BMI prior to LTx. Eighty patients (65%) had a diagnosis of DM before and 13 (11%) only after LTx. Recipients with DM had a significantly higher 1- and 5-year survival (89% and 71%) than those without (71% and 51%). In the multivariate Cox-regression analysis, DM had no impact on LTx-survival.

CONCLUSIONS

One- and five-year survival rates after LTx tend to be better in CF recipients with DM compared to those without DM. No impact of DM on the development of BOS was found.

Cystic fibrosis related diabetes (CFRD)--the end stage of progressive insulin deficiency

In cystic fibrosis, gradual pancreatic destruction causes progressive insulin deficiency, culminating in cystic fibrosis related diabetes (CFRD). As a consequence of insulin deficiency, elevated glucose levels can be detected (well before the diagnosis of CFRD), by continuous ambulatory subcutaneous interstitial fluid glucose monitoring or 30-min sampled oral glucose tolerance test (OGTT). Current diagnostic criteria for CFRD (based on 0 and 120-min OGTT blood glucose levels) were originally designed to forecast microvascular disease in type 2 diabetes, rather than CF-specific outcomes such as declining weight or lung function. In CF, decline in either weight or lung function predicts early mortality. Both may precede the diagnosis of CFRD by several years. Insulin, a potent anabolic hormone, is recommended treatment for CFRD, but use in earlier stages of insulin deficiency is not established. Conventional dosing (with four or more insulin injections per day) is burdensome and carries substantial risk of hypoglycemia. However, recent uncontrolled trials suggest that once-daily injection of intermediate or long-acting insulin improves weight and lung function, with minimal hypoglycemia risk, in CFRD and also in early insulin deficiency. It is plausible that insulin may be of greater benefit to respiratory function when given prior to the diagnosis of CFRD, after which structural lung disease may be irreversible. It is also plausible that early insulin treatment may prolong the lifespan of the remaining insulin-secreting β-cells. Randomized controlled trials are now needed to determine whether or not current clinical practice should be altered toward the earlier commencement of insulin in CF.

Diabetic keto-acidosis as a presentation of cystic fibrosis-related diabetes: a case report

Cystic fibrosis (CF) is one of the most common genetically inherited diseases and often complicated by diabetes mellitus. With increasing longevity, the incidence and prevalence of cystic fibrosis-related diabetes (CFRD) rise and microvascular complications develop. CFRD is an entity on its own with characteristics seen in both type 1 and type 2 diabetes. Keto-acidosis, a potentially life-threatening complication of diabetes, is an extremely rare presentation of CFRD. Here we present the history of a 21-year-old CF patient with no prior diagnosis of CFRD who developed keto-acidosis after an episode of pulmonary infection. Based on this case report we would like to emphasize the importance of screening for and early treatment of CFRD. We also discuss the management policy of CFRD and when and whether to initiate insulin therapy.

Low prevalence of glucose intolerance in racially mixed children with cystic fibrosis

OBJECTIVE

To evaluate glucose tolerance in racially mixed Brazilian youth with cystic fibrosis (CF).

METHODS

Cross-sectional study conducted between August and September 2007, at a reference service for CF, evaluating: glycated hemoglobin (HbA1c), blood glucose, and insulin levels, before and 2 h after a glucose overload.

RESULTS

There were 46 patients aged between 6 yr and 16 yr and 2 months (median: 9 yr and 10 months) of whom 64% were boys. Of these, 26% were Whites; 54.4% Mulattoes; and 19.6% Blacks. HbA1c was normal in all patients. Only one participant (12-yr old) had glucose intolerance. Insulin levels ranged from 1 to 23 µIU/mL (median: 4.5 µIU/mL) at baseline and from 3.2 to 192.1 µIU/mL (median: 11 µIU/mL) after a glucose overload. Insulin resistance evaluated by the HOMA index, stratified by sex and age, was present in three patients. The ΔF508 mutation was present in only 4.3% of the sample, all of them being heterozygous.

CONCLUSIONS

The low prevalence of carbohydrate intolerance in this population is probably a result of their young age. Another possibility is the low frequency of the ΔF508 mutation. Although not conclusive, these data suggest that in addition to age, the genotype:phenotype ratio may influence the development of glucose intolerance in patients with CF.

Long-term metabolic outcome and quality of life after laparoscopic adjustable gastric banding in obese patients with type 2 diabetes mellitus or impaired fasting glucose

BACKGROUND

The long-term outcome of type 2 diabetes mellitus after laparoscopic adjustable gastric banding (LAGB) is unknown.

METHODS

A longitudinal cohort study was undertaken of patients with grade 3 obesity and type 2 diabetes or impaired fasting glucose (IFG) undergoing LAGB. Metabolic outcomes and quality of life (QoL) were assessed before and 5 years after LAGB.

RESULTS

At 5 years, data for 22 out of 23 patients with type 2 diabetes and 51 out of 53 with IFG were available. Mean(s.d.) excess weight loss was 41(25) and 41(27) per cent in patients with type 2 diabetes and IFG respectively, and was associated with a significant decrease in haemoglobin (Hb) A1c, fasting and postprandial blood glucose, insulin and triglyceride levels, and in liver steatosis. There were significant increases in insulin sensitivity, beta-cell function, disposition index, high-density lipoprotein-cholesterol and QoL (Nottingham Health Profile). Good metabolic control (HbA1c 7 per cent or less) was obtained in 13 diabetic patients, but complete diabetes remission was maintained in only four. Longer duration of diabetes, and poor preoperative glucose control and beta-cell function at baseline were associated with a less favourable outcome.

CONCLUSION

LAGB improved metabolic outcomes and QoL in patients with grade 3 obesity with IFG or type 2 diabetes but rarely led to prolonged remission in long-standing diabetes.

Dietary cassava, beta-cell function and hyperbolic product loss rate in type 2 diabetes patients from South Kivu

OBJECTIVE

Cassava, a major carbohydrate source in Africa, contains potentially diabetogenic chemicals, although its consumption is not associated with incident diabetes. As it is not known whether cassava intake impairs residual beta-cell function in patients with type 2 diabetes (T2D), our study compared the metabolic phenotypes of diet- and/or oral antidiabetic drug (OAD)-treated T2D patients in South Kivu (Democratic Republic of the Congo) with [Cassava (+); n=147] and without [Cassava (-); n=46] self-reported cassava consumption.

DESIGN & METHODS

A total of 193 patients [male:female (%) 37:63; mean +/-1 SD age: 56+/-11 years] were interviewed to determine the frequency and distribution of eight major dietary carbohydrate (CHO) sources (cassava, plantain, rice, maize, bread, sorghum, potatoes and legumes). Fasting glucose, insulin and lipid levels were obtained after an overnight fast and OAD discontinuation. Cassava (+) and Cassava (-) groups were compared for HOMA indices of insulin sensitivity (S), beta-cell function (B), hyperbolic product (B x S) and B x S loss rate (B x S LR).

RESULTS

Diabetes duration was 6+/-7 years, age at diabetes diagnosis was 51+/-11 years and BMI was 25+/-5 kg/m(2). Cassava intake was reported by 76% of patients, and amounted to 29+/-11% of their daily CHO intake. The Cassava (-) group ate more plantain, maize, bread and potatoes, and less sorghum. Age, gender and age at diabetes diagnosis did not differ between Cassava (+) and (-) patients, nor did BMI, fat mass, waist circumference, lipid profile and metabolic syndrome prevalence. HOMA indices of S, B, B x S and B x S LR did not differ significantly between groups-Cassava (+) vs (-): S, 114+/-56% vs 114+/-60%; B, 34+/-30% vs 39+/-32%; B x S, 38+/-35% vs 40+/-31%; and B x S LR, 1.19+/-0.84% vs 1.09+/-0.65% per year-nor did the glucose-lowering modalities.

CONCLUSION

Cassava consumption in South Kivu is not associated with changes in T2D phenotype or in the glucose homoeostasis determinants S, B, B x S and B x S LR. Cassava consumption does not accelerate beta-cell function loss in such a population, whose markedly compromised glucose homoeostasis renders them vulnerable to environmentally acquired beta-cell impairment.

Mechanisms of glucose intolerance in cystic fibrosis

AIMS

Although cystic fibrosis-related diabetes (CFRD), a poor prognostic factor in cystic fibrosis (CF), is characterized by insulinopenia, the role of insulin resistance is unclear. Using a prospective study design, we measured insulin resistance, pancreatic beta-cell function and correlated glycaemic status with clinical parameters.

METHODS

Oral glucose tolerance test was performed in 60 stable adult CF patients. Insulin sensitivity and beta-cell function were measured using the homeostatic model assessment (HOMA2), Stumvoll and oral glucose insulin sensitivity (OGIS) indices.

RESULTS

Forty-two (70%) had normal glucose tolerance (NGT), 10 (17%) impaired glucose tolerance (IGT) and eight (13%) CFRD. There was no difference in insulin sensitivity among the three groups (HOMA2: NGT 280, IGT 250, CFRD 339, P = 0.42; Stumvoll: NGT 0.128, IGT 0.126, CFRD 0.129, P = 0.76; and OGIS: NGT 515, IGT 472, CFRD 472, P = 0.12). Pancreatic beta-cell function (CFRD 50% vs. NGT 67%; P < 0.05) and first-phase insulin secretion were reduced in CFRD (250 vs. NGT 509; P = 0.004). First-phase insulin secretion was inversely correlated with 1-h (r = -0.74; P < 0.0001) and 2-h glucose levels (r = -0.34; P < 0.05). There was no difference in body mass index or poor lung function (forced expiratory volume in 1 s: CFRD 54% vs. NGT 65%; P = 0.43). However, there were more hospital admissions in the CFRD group (three vs. NGT one per patient per year; P < 0.05).

CONCLUSIONS

CFRD is characterized by qualitative and quantitative defects in insulin secretion, but not insulin resistance, and is associated with increased hospital admissions for pulmonary exacerbations.

Genetic determinants and epidemiology of cystic fibrosis-related diabetes: results from a British cohort of children and adults

OBJECTIVE

Longer survival of patients with cystic fibrosis has increased the occurrence of cystic fibrosis-related diabetes (CFRD). In this study we documented the incidence of CFRD and evaluated the association between mutations responsible for cystic fibrosis and incident CFRD, while identifying potential risk factors.

RESEARCH DESIGN AND METHODS

This was a population-based longitudinal study of 50 cystic fibrosis speciality clinics in the U.K. Subjects included 8,029 individuals aged 0-64 years enrolled in the U.K. Cystic Fibrosis Registry during 1996-2005. Of these, 5,196 with data and without diabetes were included in analyses of incidence, and 3,275 with complete data were included in analyses of risk factors. Diabetes was defined by physician diagnosis, oral glucose tolerance testing, or treatment with hypoglycemic drugs.

RESULTS

A total of 526 individuals developed CFRD over 15,010 person-years. The annual incidence was 3.5%. The incidence was higher in female patients and in patients with mutations in the cystic fibrosis transmembrane conductance regulator (CFTR) gene in classes I and II. In a multivariate model of 377 cases of 3,275 patients, CFTR class (relative risk 1.70 [95% CI 1.16-2.49], class I or II versus others), increasing age, female sex, worse pulmonary function, liver dysfunction, pancreatic insufficiency, and corticosteroid use were independently associated with incident diabetes.

CONCLUSIONS

The incidence of CFRD is high in Britain. CFTR class I and II mutations increase the risk of diabetes independent of other risk factors including pancreatic exocrine dysfunction.