Evaluation of glucose tolerance and insulin secretion in cystic fibrosis patients

Associations Between Glucose Tolerance, Insulin Secretion, Muscle and Fat Mass in Cystic Fibrosis

Background:

A frequent comorbidity in cystic fibrosis (CF) is CF related diabetes (CFRD) caused by a gradual decline in insulin secretion. The reduction in the anabolic hormone, insulin, might explain the weight loss that precedes onset of CFRD. We investigated the association between muscle and fat mass in relation to glucose tolerance and insulin function.

Methods:

In a cross-sectional study with CF patients (⩾18 years), we conducted an oral glucose tolerance test and dual energy X-ray absorptiometry scan (DXA). Based on plasma glucose, glucose tolerance was defined as normal (NGT): 1-hour <11.1 mmol/L and 2-hour <7.8 mmol/L, impaired (IGT): 2-hour ⩾7.8 and <11.1 mmol/L or CFRD: 2-hour ⩾11.1 mmol/L. Insulin resistance (HOMA-IR) was derived from fasting levels of plasma glucose and plasma insulin, and fat-free and fat mass index (kg/m²) from DXA. Associations were evaluated using linear regression models adjusted for age, sex, and pancreas insufficiency.

Results:

Among 79 CF patients with exocrine pancreas insufficiency, impairment of glucose tolerance corresponded to reduced insulin secretion. In the IGT group the fat-free mass index (FFMI) was 1.2 kg/m² (95% CI: [−2.3, −0.03] kg/m², P = .044) lower compared to the NGT group. FFMI increased insignificantly by 0.4 kg/m² (95% CI: [−0.6, 1.5] kg/m², P = .422) among the insulin-treated CFRD group compared to IGT. Fat mass index (FMI) was not different between groups but tended to decrease with glucose tolerance impairment. For each 100 pmol/L increase in fasting insulin FFMI increased by 1.77 kg/m² (95% CI: [0.21, 3.33] kg/m²/pmol/L/100) and FMI increased by 6.15 kg/m² (95% CI: [3.87, 8.44] kg/m²/pmol/L/100). In multivariate analyses, HOMA-IR was positively associated with FFMI (β = 0.5 kg/m²/HOMA-IR, 95% CI: [0.08, 0.92] kg/m²/HOMA-IR, P = .021) and FMI (β = 1.5 kg/m²/HOMA-IR, 95% CI: [0.87, 2.15] kg/m²/HOMA-IR, P < .001).

Conclusions:

Muscle mass was significantly lower among participants with impaired glucose tolerance (IGT), while muscle mass was normalized among those treated with insulin.

Drug treatments for managing cystic fibrosis-related diabetes

BACKGROUND

The Cystic Fibrosis Foundation recommends both short-term and long-acting insulin therapy when cystic fibrosis-related diabetes (CFRD) has been diagnosed. Diagnosis is based on: an elevated fasting blood glucose level greater than 6.94 mmol/L (125 mg/dL); or oral glucose tolerance tests greater than 11.11 mmol/L (200 mg/dL) at two hours; or symptomatic diabetes for random glucose levels greater than 11.11 mmol/L (200 mg/dL); or glycated hemoglobin levels of at least 6.5%. This is an update of a previously published review.

OBJECTIVES

To establish the effectiveness of insulin and oral agents for managing diabetes in people with cystic fibrosis in relation to blood sugar levels, lung function and weight management.

SEARCH METHODS

We searched the Cochrane Cystic Fibrosis and Genetic Disorders Group's Trials Register comprising references identified from comprehensive electronic database searches and handsearches of relevant journals and abstract books of conference proceedings. We also handsearched abstracts from pulmonary symposia and the North American Cystic Fibrosis Conferences. Date of most recent register search: 10 September 2020. We searched online trials registries; date of most recent searches: 21 March 2020.

SELECTION CRITERIA

Randomized controlled trials comparing all methods of pharmacological diabetes therapy in people with diagnosed CFRD.

DATA COLLECTION AND ANALYSIS

Two authors independently extracted data and assessed the risk of bias in the included studies. Authors also used GRADE to assess the quality of the evidence.

MAIN RESULTS

The searches identified 29 trials (45 references). Four included trials provide results: one short-term single-center cross-over trial (seven adults) comparing insulin with oral repaglinide and no medication in adults with CFRD and normal fasting glucose; one long-term multicenter trial (61 adults with CFRD) comparing insulin with oral repaglinide and placebo; one long-term multicenter trial (67 adults) comparing insulin with oral repaglinide; and one 12-week single-center cross-over trial (20 adults) comparing the long-acting insulin glargine to short-term neutral protamine Hagedorn insulin. Two ongoing trials of newly approved incretin mimics have been noted for possible future inclusion. Downgrading of the quality of the evidence was mainly due to risks of bias across all domains, but particularly due to concerns surrounding allocation concealment and selective reporting. There were also some concerns due to imprecision from small sample sizes and low event rates. Finally, there may be some bias due to the amounts of insulin and repaglinide given not being comparable. Data from one trial comparing insulin to placebo (39 participants) did not show any difference between groups for the primary outcomes of blood glucose levels (very low-quality evidence), lung function (low-quality evidence) or nutritional status (low-quality evidence). Similarly, no differences between groups were seen for the secondary outcomes of number of hypoglycemic episodes (low-quality evidence), secondary infection complications or quality of life (QoL). These results were mirrored in the narrative reports for the second trial in this comparison (seven participants). Data from the one-year trial comparing repaglinide to placebo (38 participants), showed no differences between groups for the primary outcomes of blood glucose levels (very low-quality evidence), lung function (low-quality evidence) and nutritional status (low-quality evidence). Also, no differences were seen between groups for the secondary outcomes of number of hypoglycemic episodes (low-quality evidence), secondary infection complications or QoL. These findings were mirrored in the narrative reports for the second trial (n = 7) in this comparison. Three trials compared insulin to repaglinide (119 participants). Data from one trial (n = 67) showed no difference in blood glucose levels at either 12 months (high-quality evidence) or 24 months; narrative reports from one trial (45 participants) reported no difference between groups, but the second trial (7 participants) reported a beneficial effect of insulin over repaglinide. Two trials (112 participants) found no difference between insulin and repaglinide in lung function or nutritional status (moderate-quality evidence). Two trials (56 participants) reported no difference in the number of hypoglycemic episodes (low-quality evidence). One trial (45 participants) reported no difference between groups in secondary infections and cystic fibrosis QoL. The single trial comparing glargine to neutral protamine Hagedorn insulin did not report directly on the review's primary outcomes, but did report no differences between groups in post-prandial glucose values and weight; neither group reported infectious complications. There was no difference in episodes of hypoglycemia (very low-quality evidence) and while there was no difference reported in QoL, all participants opted to continue treatment with glargine after the trial was completed. Mortality was not reported by any trial in any comparison, but death was not given as a reason for withdrawal in any trial.

AUTHORS' CONCLUSIONS

This review has not found any conclusive evidence that any agent has a distinct advantage over another in controlling hyperglycemia or the clinical outcomes associated with CFRD. Given the treatment burden already experienced by people with cystic fibrosis, oral therapy may be a viable treatment option. While some cystic fibrosis centers use oral medications to help control diabetes, the Cystic Fibrosis Foundation (USA) clinical practice guidelines support the use of insulin therapy and this remains the most widely-used treatment method. Randomized controlled trials specifically related to controlling diabetes and its impact on the course of pulmonary disease process in cystic fibrosis continue to be a high priority. Specifically, investigators should evaluate adherence to different therapies and also whether there is benefit in using additional hypoglycemic agents as well as the newly approved incretin mimics. Agents that potentiate insulin action, especially agents with additional anti-inflammatory potential should also be further investigated as adjuvant therapy to insulin.

A Systematic Review of Childhood Diabetes Research in the Middle East Region

Background: Diabetes mellitus (DM) is a common chronic disorder in children and is caused by absolute or relative insulin deficiency, with or without insulin resistance. There are several different forms of childhood DM. Children can suffer from neonatal diabetes mellitus (NDM), type 1 diabetes (T1DM), type 2 diabetes (T2DM), Maturity Onset Diabetes of the Young (MODY), autoimmune monogenic, mitochondrial, syndromic and as yet unclassified forms of DM. The Middle East has one of the highest incidences of several types of DM in children; however, it is unclear whether pediatric diabetes is an active area of research in the Middle East and if ongoing, which research areas are of priority for DM in children. Objectives: To review the literature on childhood DM related to research in the Middle East, summarize results, identify opportunities for research and make observations and recommendations for collaborative studies in pediatric DM. Methods: We conducted a thorough and systematic literature review by adhering to a list recommended by PRISMA. We retrieved original papers written in English that focus on childhood DM research, using electronic bibliographic databases containing publications from the year 2000 until October 2018. For our final assessment, we retrieved 429 full-text articles and selected 95 articles, based on our inclusion and exclusion criteria. Results: Our literature review suggests that childhood DM research undertaken in the Middle East has focused mainly on reporting retrospective review of case notes, a few prospective case studies, systemic reviews, questionnaire-based studies, and case reports. These reported studies have focused mostly on the incidence/prevalence of different types of DM in childhood. No studies report on the establishment of National Childhood Diabetes Registries. There is a lack of consolidated studies focusing on national epidemiology data of different types of childhood DM (such as NDM, T1DM, T2DM, MODY, and syndromic forms) and no studies reporting on clinical trials in children with DM. Conclusions: Investing in and funding basic and translational childhood diabetes research and encouraging collaborative studies, will bring enormous benefits financially, economically, and socially for the whole of the Middle East region.

Insulin and oral agents for managing cystic fibrosis-related diabetes

BACKGROUND

The Cystic Fibrosis Foundation recommends both short-term and long-acting insulin therapy when cystic fibrosis-related diabetes has been diagnosed. Diagnosis is based on: an elevated fasting blood glucose level greater than 6.94 mmol/liter (125 mg/deciliter); or oral glucose tolerance tests greater than 11.11 mmol/liter (200 mg/deciliter) at two hours; or symptomatic diabetes for random glucose levels greater than 11.11 mmol/liter (200 mg/deciliter); or glycated hemoglobin levels of at least 6.5%.

OBJECTIVES

To establish the effectiveness of insulin and oral agents for managing diabetes in people with cystic fibrosis in relation to blood sugar levels, lung function and weight management.

SEARCH METHODS

We searched the Cochrane Cystic Fibrosis and Genetic Disorders Group's Trials Register comprising references identified from comprehensive electronic database searches and handsearches of relevant journals and abstract books of conference proceedings. We also handsearched abstracts from pulmonary symposia and the North American Cystic Fibrosis Conferences.Date of the most recent search of the Group's Cystic Fibrosis Trials Register: 18 February 2016.

SELECTION CRITERIA

Randomized controlled trials comparing all methods of diabetes therapy in people with diagnosed cystic fibrosis-related diabetes.

DATA COLLECTION AND ANALYSIS

Two authors independently extracted data and assessed the risk of bias in the included studies.

MAIN RESULTS

The searches identified 22 trials (34 references). Four trials (200 participants) are included: one short-term single-center trial (n = 7) comparing insulin with oral repaglinide and no medication in people with cystic fibrosis-related diabetes and normal fasting glucose; one long-term multicenter trial (n = 100, 74 of whom had cystic fibrosis-related diabetes) comparing insulin with oral repaglinide and placebo; one long-term multicenter trial (n = 73) comparing insulin with oral repaglinide; and one 12-week single-center trial (n = 20) comparing the long-acting insulin glargine to short-term neutral protamine Hagedorn insulin.Two trials with data for the comparison of insulin to placebo did not report any significant differences between groups for the primary outcomes of blood glucose levels, lung function and nutritional status. This was also true for the single trial with data for the comparison of repaglinide to placebo. Two trials (one lasting one year and one lasting two years) contributed data for the comparison of insulin versus repaglinide. There were no significant differences for the primary outcomes at any time point, except at one year (in the two-year trial) when the insulin group had significant improvement in z score for body mass index compared to the repaglinide group. The single trial comparing glargine to neutral protamine Hagedorn insulin also did not report any significant differences in the review's primary outcomes. A few cases of hypoglycemia were seen in three out of the four trials (none in the longest trial), but these events resolved without further treatment.There was an unclear risk of bias from randomization and allocation concealment in two of the four included trials as the authors did not report any details; in the remaining two studies details for randomization led to a low risk of bias, but only one had sufficient details on allocation concealment to allow a low risk judgement, the second was unclear. There was a high risk from blinding for all trials (except for the comparison of oral repaglinide versus placebo) due to the nature of the interventions. Complete data for all outcomes were not available from any trial leading to a high risk of reporting bias. The amounts of insulin and repaglinide administered were not comparable and this may lead to bias in the results. None of the included trials were powered to show a significant improvement in lung function.

AUTHORS' CONCLUSIONS

This review has not found any significant conclusive evidence that long-acting insulins, short-acting insulins or oral hypoglycemic agents have a distinct advantage over one another in controlling hyperglycemia or clinical outcomes associated with cystic fibrosis-related diabetes. While some cystic fibrosis centers use oral medications to help control diabetes, the Cystic Fibrosis Foundation (USA) clinical practice guidelines support the use of insulin therapy and this remains the most widely-used treatment method. Randomized controlled trials specifically related to controlling diabetes with this impact on the course of pulmonary disease process in cystic fibrosis continue to be a high priority.There is no demonstrated advantage yet established for using oral hypoglycemic agents over insulin, and further trials need to be evaluated to establish whether there is clear benefit for using hypoglycemic agents. Agents that potentiate insulin action, especially agents with additional anti-inflammatory potential should be further investigated to see if there may be a clinical advantage to adding these medications to insulin as adjuvant therapy.

The road for survival improvement of cystic fibrosis patients in Arab countries

Cystic fibrosis (CF) is a lethal, monogenic disorder that affects multiple organ systems of the body. The incidence has been described before in the Middle East to be 1 in 2000 to 1 in 5800 live births, and the median survival was estimated to be from 10 to 20 years of age. The present article attempts to revisit various facets of this disease and specifically highlights the most important lacunae that exist in treating CF. In addition, it also tries to emphasize the steps in improving the median survival of patients with CF, in these countries.

Insulin and oral agents for managing cystic fibrosis-related diabetes

BACKGROUND

The Cystic Fibrosis Foundation recommends both short-term and long-acting insulin therapy when cystic fibrosis-related diabetes has been diagnosed. Diagnosis is based on: an elevated fasting blood glucose level greater than 6.94 mmol/liter (125 mg/deciliter); or symptomatic diabetes for random glucose levels greater than 11.11 mmol/liter (200 mg/deciliter); or glycated hemoglobin levels of at least 6.5%.

OBJECTIVES

To establish the effectiveness of agents for managing diabetes in people with cystic fibrosis in relation to blood sugar levels, lung function and weight management.

SEARCH METHODS

We searched the Cochrane Cystic Fibrosis and Genetic Disorders Group Trials Register comprising references identified from comprehensive electronic database searches and handsearches of relevant journals and abstract books of conference proceedings. We also handsearched abstracts from pulmonary symposia and the North American Cystic Fibrosis Conferences.Date of the most recent search of the Group's Cystic Fibrosis Trials Register: 22 July 2013.

SELECTION CRITERIA

Randomized controlled trials comparing all methods of diabetes therapy in people with diagnosed cystic fibrosis-related diabetes.

DATA COLLECTION AND ANALYSIS

Two authors independently extracted data and assessed the risk of bias in the included studies.

MAIN RESULTS

The searches identified 19 studies (28 references). Three studies (107 participants) are included: one comparing insulin with oral repaglinide and no medication (short-term single-center study of seven patients with cystic fibrosis-related diabetes and normal fasting glucose); one comparing insulin with oral repaglinide and placebo (long-term multi-center study with 81 patients, 61 of whom had cystic fibrosis-related diabetes); and one 12-week single-center study comparing the long-acting insulin, glargine to short-term neutral protamine Hagedorn insulin. The long-term trial of insulin and repaglinide demonstrated no significant difference between treatments. In the smaller study comparing insulin and oral repaglinide, there were two incidents of significant hypoglycemia in the insulin group compared to one in the repaglinide group; in the larger study there were five incidents of significant hypoglycemia in the insulin group and six in the repaglinide group. The study comparing glargine to neutral protamine Hagedorn insulin demonstrated a statistically non-significant weight increase in with longer-acting insulin given at bedtime and reported a mean of six hypoglycemia events in the glargine group compared to five events in the neutral protamine Hagedorn insulin group. None of the three included studies were powered to show a significant improvement in lung function.

AUTHORS' CONCLUSIONS

This review has not found any significant conclusive evidence that long-acting insulins, short-acting insulins or oral hypoglycemic agents have a distinct advantage over one another in controlling hyperglycemia or clinical outcomes associated with cystic fibrosis-related diabetes. While some cystic fibrosis centers use oral medications to help control diabetes, the Cystic Fibrosis Foundation (USA) clinical practice guidelines support the use of insulin therapy and this remains the most widely-used treatment method. Randomized controlled trials specifically related to controlling diabetes with this impact on the course of pulmonary disease process in cystic fibrosis continue to be a high priority.There is no demonstrated advantage yet established for using oral hypoglycemic agents over insulin, and further studies need to be evaluated to establish whether there is clear benefit for using hypoglycemic agents. Agents that potentiate insulin action, especially agents with additional anti-inflammatory potential should be further investigated to see if there may be a clinical advantage to adding these medications to insulin as adjuvant therapy.

Nutritional decline in cystic fibrosis related diabetes: the effect of intensive nutritional intervention

BACKGROUND

Reports indicate that nutritional and respiratory decline occur up to four years prior to diagnosis of cystic fibrosis related diabetes (CFRD). Our aim was to establish whether intensive nutritional intervention prevents pre-diabetic nutritional decline in an adult population with CFRD.

METHODS

48 adult patients with CFRD were matched to 48 controls with CF, for age, gender and lung pathogen status. Nutritional and other clinical indices were recorded at annual intervals from six years before until two years after diagnosis. Data were also analysed to examine the impact of early and late acquisition of CFRD.

RESULTS

No important differences in weight, height, body mass index (BMI), lung function or intravenous treatment were found between groups in the six years prior to diagnosis, nor any significant deviation over time. In those who developed diabetes, use of overnight enteral tube feeding (ETF) was four times as likely at the time of diagnosis, compared to controls [ETF 43.8% (CFRD) v 18.8% (CF Controls), OR 4.0, CI 1.3 to 16.4, p=0.01]. Age at onset of CFRD played a significant role in determining the pre-diabetic clinical course. Younger diabetics with continued growth at study onset (n=17) had a lower BMI from 2 years prior to diagnosis compared to controls [BMI 18.9 kg/m(2) (CFRD) v 20.8 kg/m(2) (CF Controls), diff=1.9, CI -0.1 to 3.7 p=0.04]. The BMI of older diabetics (completed growth at study onset) was equal to that of controls throughout.

CONCLUSION

Pre-diabetic nutritional decline is not inevitable in adults with CFRD, but is influenced by age of onset. In the group overall, those with CFRD are more likely to require ETF from 2 years prior to diagnosis. Despite intensive nutritional intervention, patients who continue to grow throughout the pre-diabetic years, show a level of nutritional decline absent in older adults.

Evaluation of glucose tolerance in cystic fibrosis: comparison of 50-g and 75-g tests

BACKGROUND

The recommended tests for evaluation of glucose tolerance in cystic fibrosis are the fasting blood glucose (FBG) and the 75-g, fasting, 2-h oral glucose tolerance test (OGTT). We compared a 50 g, non-fasting, 1-h glucose challenge test (GCT) to the standard OGTT.

METHODS

During their regularly scheduled visit to the cystic fibrosis clinic, patients underwent a 50-g, non-fasting 1-h GCT and were asked to complete a standard 75-g, fasting, 2-h OGTT within one week of their clinic visit.

RESULTS

Fifty-seven patients underwent glucose tolerance testing. Of these, 31/57 (54%) completed both tests. Hyperglycemia was detected on both tests in 9/31 (29%) patients, 11/31 (35%) tested positive only on the GCT, while all those with positive OGTTs had positive GCTs (p<0.01).

CONCLUSIONS

In this study, the GCT identified all patients who meet the criteria for abnormal glucose tolerance on an OGTT. There was a large subgroup that was positive for glucose intolerance only on the GCT. These individuals represent a distinct biochemical subgroup of uncertain significance that warrants closer evaluation. Although the GCT can be completed in a non-fasting state and in conjunction with regular blood work or clinic visits, the anticipated greater compliance was not seen.

The metabolic effects of pregnancy in cystic fibrosis

OBJECTIVE

Our purpose was to determine glucose tolerance in pregnant women with cystic fibrosis (CF) and to relate glucose tolerance to insulin sensitivity, hepatic glucose production, and protein turnover.

METHODS

We studied 8 CF women during pregnancy (CFPreg). Results were compared with those from 9 pregnant controls (PregCont) and 8 nonpregnant CF women (CFCont). The following metabolic studies were conducted: oral glucose tolerance test (OGTT), hyperinsulinemic euglycemic clamp, stable isotope infusion of [1-13C]leucine and [6,6-2H2]glucose for measurement of whole body protein turnover and hepatic glucose production (HGP), respectively. Indirect calorimetry was used to measure resting energy expenditure (REE), and food intake was measured by 3-day food journals. Fat-free mass was measured by total body potassium 40K scan.

RESULTS

All but one CFPreg developed diabetes by the end of the second trimester and had significantly lower insulin secretion and more insulin resistance than PregCont. Hepatic glucose production was significantly higher and suppression by insulin was less in CF subjects, and protein breakdown was significantly higher. Insulin resistance and HGP increased during pregnancy similarly in CFPreg and PregCont groups.

CONCLUSION

Pregnancy in CF is associated with decreased insulin sensitivity and high HGP, in addition to inherent decreased insulin secretion. Pregnancy in CF is also associated with increased protein turnover and less response to insulin's anticatabolic effect. These changes appear to predispose the pregnant CF women to early development of diabetes and poor weight gain.

Insulin and oral agents for managing cystic fibrosis-related diabetes

BACKGROUND

Insulin therapy is recommended by the Cystic Fibrosis Foundation when cystic fibrosis-related diabetes has been diagnosed. Diagnosis is based on an elevated fasting blood glucose level greater than 6.94 mmol/liter (125 mg/deciliter) or symptomatic diabetes for random glucose levels greater than 11.11 mmol/liter (200 mg/deciliter).

OBJECTIVES

To examine the evidence that, when treated with agents for managing diabetes, people with cystic fibrosis improve their sugar metabolic control resulting in beneficial impact on lung function and the ability to maintain optimal weight.

SEARCH STRATEGY

We searched the Cochrane Cystic Fibrosis and Genetic Disorders Group Trials Register comprising references identified from comprehensive electronic database searches and handsearches of relevant journals and abstract books of conference proceedings. We also handsearched abstracts from pulmonary and North American Cystic Fibrosis Conference symposia. Date of the most recent search of the Group's Trials Register: December 2004.

SELECTION CRITERIA

Randomized controlled trials comparing all methods of diabetes therapy for one month or longer in people with cystic fibrosis.

DATA COLLECTION AND ANALYSIS

No studies were found which were eligible for inclusion in this review.

MAIN RESULTS

Six references to four studies were identified by the searches, but none were eligible for inclusion in the review as they were not randomized controlled trials.

AUTHORS' CONCLUSIONS

While some cystic fibrosis centers use oral medications to help control diabetes, a condition which complicates the course of cystic fibrosis, insulin therapy is the recommended and most widely used treatment method. Lung function has been reported to improve with the use of insulin, but this has not been correlated to the degree in which sugar metabolism has been affected. While the Cystic Fibrosis Foundation recommends insulin therapy be used in managing diabetes, this systematic review identifies the need for a multicentre randomized controlled trial assessing both the efficacy of insulin or other insulin-releasing or insulin-sensitizing medications and their possible adverse effects in managing cystic fibrosis-related diabetes.

Insulin-secretion abnormalities and clinical deterioration related to impaired glucose tolerance in cystic fibrosis

OBJECTIVE

To evaluate insulin-secretion kinetics and insulin sensitivity in cystic fibrosis (CF) patients with normal glucose tolerance (CF-NGT), impaired glucose tolerance (CF-IGT) or CF-related diabetes (CFRD), and the potential effects of moderate hyperglycemia on clinical and nutritional status.

DESIGN AND METHODS

Cross-sectional study including 50 outpatients with CF. Patients underwent both oral (OGGT) and intravenous (IVGTT) glucose tolerance tests in order to assess insulin secretion and peripheral insulin sensitivity. Homeostasis assessment model and OGGT were used to investigate insulin sensitivity. Forced expiratory volume in the first second (FEV(1)) and forced vital capacity (FVC) were measured to evaluate pulmonary function. Body mass index (BMI) was determined to assess nutritional status.

RESULTS

Insulin secretion was significantly decreased (and delayed at OGTT) in the CFRD group (n = 9) versus the CF-IGT group (n = 10) and the CF-IGT versus the CF-NGT group (n = 31). Insulin sensitivity was significantly different in the CF-IGT and CFRD groups versus the CF-NGT group. FEV(1), FVC and BMI presented a significant linear correlation with plasma glucose value at 120 min at OGTT and were significantly lower in both CF-IGT and CFRD versus the CF-NGT group, whereas no differences were found between the CF-IGT and CFRD groups.

CONCLUSIONS

CF patients with IGT present diminished insulin secretion and increased peripheral insulin resistance, correlating with a worse clinical status, undernutrition and impaired pulmonary function. These findings open the question of whether early treatment of mild alterations of glucose metabolism with insulin secretagogues or short-action insulin may lead to improvement of clinical status in CF patients.

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.