Research of factors for glucose intolerance in mucoviscidosis]

Glucose tolerance has been assessed in cystic fibrosis (CF) children using HbA1C and plasma glucose and insulin determinations during an oral glucose tolerance test (OGTT), along with the determination of HLA-DR and islet-cell (ICA) and anti-insulin (IAA) antibodies. Of 49 patients (25 males, 24 females), aged 2 to 21 years (mean = 10.9 years), 29 had normal glucose tolerance (WHO criteria) during OGTT, 14 had impaired glucose tolerance (IGT) and 6 had an isolated hyperglycemia at 120 min. Fasting plasma glucose and HbA1C were significantly higher in IGT than in normoglycemic patients. However, these two parameters showed poor individual predictive value of disturbance in glucose tolerance. Of 14 patients with abnormal OGTT, 7 were aged below 10 years, with 2 as young as 5 years; 8 patients were females. HLA antigens characteristic of type I diabetes tended to be found less frequently in CF patients than in the general population: 9% were DR3, 7% were DR4 and none was DR3/DR4. There were no HLA differences according to glucose tolerance. ICA and IAA were respectively detected in only one patient. Stimulated plasma insulin was low but did not correlate with glucose tolerance. In conclusion, impaired glucose tolerance is common in cystic fibrosis and can be found early in life. Although insulin secretion is decreased in this population, it does not seem to be the only factor responsible for impaired glucose intolerance. The absence of the genetical and immunological characteristics of type I diabetes confirms that glucose intolerance in cystic fibrosis is due to other pathogenetic mechanisms.     

The abnormalities of carbohydrate metabolism in Turner syndrome: analysis of risk factors associated with impaired glucose tolerance

An oral glucose tolerance test (OGTT) was performed in 103 patients with Turner syndrome (TS) who had normal fasting and postprandial glucose levels. The plasma glucose, insulin, C-peptide and proinsulin levels were measured every 30 min during the test. Using a homeostatic model assessment (HOMA) and a quantitative insulin sensitivity check index (QUICKI), the insulin resistance in TS patients was investigated. Diabetes mellitus and impaired glucose tolerance (IGT) were newly diagnosed in two and 18 patients respectively. There was a significant increase in mean plasma glucose, insulin, C-peptide and proinsulin reponse during an OGTT in the IGT group in contrast to the normal glucose tolerance (NGT) group ( P <0.05). There was a significant decrease in the quantitative insulin sensitivity check index (QUICKI) in the IGT group in contrast to the NGT group ( P <0.05). The fasting insulin and triglyceride levels strongly predicted the 2 h glucose level during the OGTT ( P <0.05). Conclusion:The oral glucose tolerance test is superior to the fasting and postprandial plasma glucose test for the early detection of abnormalities of carbohydrate metabolism in patients with Turner syndrome.     

Impaired glucose homeostasis in young adult thalassemic patients: a pilot study with acarbose

This study investigated the effects of the alpha-glucosidase inhibitor, acarbose, on glycemic control and insulin secretion in thalassemic patients with impaired glucose tolerance. The safety and tolerability of the drug were also evaluated. Nine patients (4 men and 5 women, aged 20-34 years) with beta-thalassemia major received a standardized nutritional test load prior to and following 3 months treatment with acarbose 100 mg t.i.d. Blood glucose, insulin and C-peptide levels were measured at 0, 60, 90 and 120 min post-loading. Plasma glucose levels after 3 months of acarbose treatment tended to be slightly lower than pre-treatment levels. Although fasting serum insulin and plasma C-peptide levels were unchanged after acarbose therapy, postprandial serum levels of both hormones were markedly reduced (by 24-47% and 19-32%, respectively, at 60-120 min post-loading). Body mass index, liver enzymes and serum lipids were unaltered following acarbose treatment. Gastrointestinal disturbances were mild and tended to decrease during the course of acarbose therapy. Acarbose is a well-tolerated agent for the management of thalassemic patients with glucose intolerance and normal or increased insulin secretion. It is possible that acarbose may prevent or delay progression from impaired glucose homeostasis to frank insulin-dependent diabetes mellitus.     

Early detection of impaired glucose tolerance in patients with cystic fibrosis and predisposition factors

INTRODUCTION: The number of patients with glucose tolerance alterations associated with cystic fibrosis (CF) has increased, probably due to the greater survival rate among sufferers of this disease. We studied impaired glucose tolerance (IGT) in patients with CF and investigated whether its appearance has any relationship with age, sex, genetic mutation and/or the degree of clinical involvement. We assessed the parameters that might allow early detection. PATIENTS AND METHODS: In 28 patients with CF (14 M, 14 F; aged 22 months to 18 years), sex, genetic mutation, nutritional status and the degree of pancreatic and pulmonary involvement were recorded. The metabolic study included glycosylated hemoglobin (HbA1c) determination, oral glucose tolerance test (OGTT) and intravenous glucose tolerance tests (IVGTT). RESULTS: In the patients with CF, 35.71% showed impaired glucose tolerance (IGT) and 3.57% had diabetes mellitus. The patients with IGT and CF were 3.2 years older than those with normal glucose tolerance (NGT; p<0.05), but no significant differences were found regarding sex, anthropometric measurements, percentage of pulmonary gammagraphic involvement, Shwachman-Kulczycki test or HbA1c. In the OGTT, the patients homozygous for the deltaF508 mutation had higher blood glucose values than the heterozygous group (p=0.03), but these values were not higher than those in patients with other mutations. During the OGTT, blood insulin values at 30' were reduced in patients with IGT compared to patients with NGT (p<0.02) and the insulin peak occurred at 100.9+/-24.3 min compared to 65.3+/-21.8, respectively (p<0.05). In the IVGTT, 82.14% of the patients had reduced insulin levels at 1 and 3 min (I1'+3'). No differences in the blood glucose levels during the OGTT were found between patients with normal I1'+3' values and patients with reduced values. CONCLUSIONS: A high percentage of patients with CF also present with IGT. This increases with age and is more common among patients homozygous for the deltaF508 mutation and is not related to clinical status. Alterations in the kinetics of insulin secretion play an important role in the appearance of IGT and CF. We suggest that the OGTT is a more sensitive method than IVGTT for identifying early alterations in CF-related diabetes mellitus.     

Glucose homeostasis in mucoviscidosis

In patients with cystic fibrosis (CF) of the pancreas an endocrine imbalance especially of insulin secretion due to progressive structural abnormalities of the pancreas must be expected. 30-75 percent of CF-patient exhibit impaired oral glucose tolerance tests (oGTT). Deterioration of the glucose homeostasis leads to a secondary diabetes mellitus that mimics a type II diabetes in the early stage, in the later course of disease it resembles a type I diabetes with absolute insulinopenia. In this study glucose homeostasis was investigated after an oral glucose load with 1.75 g glucose/kg bodyweight. Glucose, C-peptide and insulin were measured during 180 minutes. 32 nondiabetic CF-patients were studied. 16 patients revealed an impaired oral glucose tolerance according to the criteria of the National Diabetes Data Group. 6 patients showed a normal glucose tolerance and 10 patients with normal fasting and 120 minute glucose concentrations were hyperglycemic at midtest determinations. Impaired oGTTs were observed in malnourished CF-patients in a higher rate than in normal weight patients. A delayed and exceeded C-peptide and insulin response to the oral glucose load was determined with deteriorating glucose tolerance. Glucose values did not drop to fasting values at the 180 minute determination in cases of impaired oral glucose tolerance.     

Diabetes mellitus in Danish cystic fibrosis patients: prevalence and late diabetic complications

Lanng S, Thorsteinsson B, Lund-Andersen C, Nerup J, Schiatz PO, Koch C. Diabetes mellitus in Danish cystic fibrosis patients: prevalence and late diabetic complications. Acta Pzdiatr 1994;83: 72–7. Stockholm. ISSN 0803–5253.
The prevalences of impaired glucose tolerance (IGT), diabetes mellitus and late diabetic complications were studied in all Danish cystic fibrosis (CF) patients. A total of 311 CF patients were identified with an estimated ascertainment rate above 98%. Glucose tolerdnce was classified in 278 (89%) patients: the prevalences of IGT and diabetes mellitus were 13.7% (38 patients) and 14.7% (41 patients), respectively, with no sex differences. The prevalence of diabetes mellitus increased with age but not with the severity of CF as compared with age- and sex-matched non-diabetic CF patients. Diabetes was diagnosed at a median age of 20 years (range 3–40 years) and the duration of diabetes was 1.7 years (0.1–17 years). Twenty-eight of the diabetic patients (70%) were trcated with insulin, on average 20 (4–90) IU per day. Late diabetic complications were identified in 4 patients (10%) with a duration of diabetes mellitus of 1–17 years: background retinopathy (2 patients), diabetic nephropathy (1 patient), microalbuminuria (1 patient) and neuropathy (2 patients). Thus diabetic CF patients are probably not less prone to develop late diabetic complications than patients with other types of diabetes of equally long duration and comparable glycemic control.     

Effects of acarbose in patients with beta-thalassaemia major and abnormal glucose homeostasis

Seventeen TM patients with impaired glucose tolerance (IGT) or non-insulin dependent diabetes mellitus (NIDDM) and hyperinsulinism were treated for 12 months with acarbose (100 mg. orally with breakfast, lunch and evening meals). An improvement in glucose tolerance was observed in 2 out of 11 TM patients with IGT and in all TM patients with NIDDM. Acarbose does not appear to directly improve insulin resistance but may have an indirect effect delaying the absorption of glucose of complex carbohydrates and disaccharides. It may be concluded that acarbose may represent a useful first-line therapy for improving glycemic control in TM patients with abnormalities of glucose homeostasis and hyperinsulinism.     

Reduced pancreatic insulin release and reduced peripheral insulin sensitivity contribute to hyperglycaemia in cystic fibrosis

Traditional opinion holds that patients with cystic fibrosis (CF) develop impaired glucose tolerance or diabetes due to insulinopenia caused by fibrosis of the pancreas. However, studies on the dynamics of insulin secretion and peripheral insulin action have yielded confliciting results. We studied 18 patients with CF (9 , 9 , age 15–29 years) and 17 healthy control subjects (8 , 9 , 20–32 years). Oral glucose tolerance tests and combined i.v.-glucose-tolbutamide-tests were performed on separate days in fasting subjects. Bergman's Minimal Model was used to quantitate both peripheral insulin sensitivity (S_I) and insulin-independent glucose disposal (glucose effectiveness; S_G). Based on National Diabetes Data Group criteria, 4 patients were classified as diabetic 922%; CF-DM), 3 patients (17%) had impaired glucose tolerance (CF-IGT) while glucose metabolism was normal in 11 patients (61%; CF-NGT). Irrespective of the degree of glucose tolerance, the insulin response to oral glucose was not reduced but delayed, up to 60 min in the CF-IGT/DM group. First-phase insulin release (0–10 min) after i.v.-glucose was significantly lower in CF patients (29% of healthy controls;P<0.0001), with no difference between the CF-NGT and CF-IGT/DM groups. Insulin release following tolbutamide injection was only marginally reduced in CF patients (64% of controls). In contrast, S_I was significantly reduced in the subgroup of CF patients with abnormal glucose metabolism (CF-IGT/DM: 0.97±0.16·10^–4 l/min/pmol; control group: 1.95±0.25;P<0.05).Conclusion The early insulin release is reduced in response to i.v.-glucose, while in the oral glucose tolerance test, insulin secretion is quantitatively preserved, but delayed. Reduced peripheral insulin sensitivity is a major factor for impaired glucose tolerance and diabetes mellitus in CF patients.     

Insulin resistance is associated with decreased clinical status in cystic fibrosis

Patients with cystic fibrosis (CF) frequently have impaired glucose tolerance and progression to diabetes (DM) with clinical features of both insulin-dependent and non-insulin-dependent diabetes. One feature of non-insulin-dependent DM is decreased insulin sensitivity, also known as insulin resistance. The goal of this study was to determine whether patients with CF exhibit insulin resistance and to determine the potential effect of insulin resistance on clinical status. We also sought to determine whether insulin resistance is associated with a specific CF genotype. We studied 18 patients with CF (8 with normal glucose tolerance, 5 with impaired glucose tolerance, 5 with DM), and 20 lean control subjects matched for age, weight, and sex. All control subjects had normal glucose tolerance. The clinical status for each CF patient was determined according to a modified National Institutes of Health scoring system. Each subject underwent a three-step hyperinsulinemic euglycemic clamp (insulin doses of 10, 40, 120 mU/m ² per minute). Results from the 120 mU/m ² per minute infusion defined maximal glucose disposal rate (defined in milligrams per kilogram body weight per minute) at steady state with peripheral insulin levels 195 ± 20 mU/ml. Subjects with CF demonstrated insulin resistance (control subjects = 13.6 ± 1.1, patients with CF = 10.2 ± 1.6 mg/kg per minute; p = 0.003). When each subgroup was compared separately with control subjects, all subgroups were statistically insulin resistant (glucose disposal rate, patients with CF and normal glucose tolerance = 10.8; those with impaired glucose tolerance = 8.4; those with DM = 10.1 mg/kg per minute), and the patients with CF with impaired glucose tolerance were the most insulin resistant. When plotted versus glucose disposal rate, a striking positive correlation between worsened clinical status and insulin resistance ( r = 0.85) is demonstrated. Furthermore, there is no correlation between insulin resistance and fasting blood glucose, subject age, or percent ideal body weight (all r values not significant). In conclusion, patients with CF exhibit insulin resistance that is associated with worsened clinical status. We believe it is the combination of insulin resistance and decreased insulin secretion that is responsible for the high incidence of CF-related diabetes. (J Pediatr 1997;130:948-56)     

Carbohydrate tolerance in cystic fibrosis is closely linked to pancreatic exocrine function

We evaluated carbohydrate tolerance in nine thin cystic fibrosis (CF) patients and in six controls, measuring responsiveness to the following insulinotropic secretagogues: oral glucose, IV glucose, and IV tolbutamide. Glucose responses segregated patients into two groups: Group I with normal carbohydrate tolerance associated with normal to slightly increased insulin responses, and Group II with impaired carbohydrate tolerance associated with insulinopenia. This latter group included one patient with frank diabetes. The CF patients demonstrated a significant positive correlation between insulin secretion, in response to each secretagogue, and pancreatic exocrine function as measured by serum pancreatic amylase isoenzyme concentration. Pancreatic alpha-cell function, as reflected by basal plasma glucagon concentrations, also correlated well with exocrine function in the CF patients, excluding the diabetic individual. The enteroinsular axis of the CF group was intact as reflected by normal plasma gastric inhibitory polypeptide concentrations in Group I and by elevated levels, basally and in response to oral glucose, in the insulinopenic Group II patients. Furthermore, those patients with impaired tolerance demonstrated a greater magnitude of insulinopenia compared to controls following IV glucose and possibly IV tolbutamide, than following oral glucose. Thus, these data suggest that loss of carbohydrate tolerance in patients with CF, like that seen with classical chronic pancreatitis, 1) parallels the loss of exocrine function, 2) is associated with appropriate enteroinsular signaling, and 3) can be detected earlier or more easily following testing with direct IV secretagogues than following oral glucose stimulation.     

Verbesserung der Glukosetoleranz von Patienten mit Zystischer Fibrose unter pseudomonaswirksamer Chemotherpie

Background. For many patients with cystic fibrosis impaired glucose tolerance or even diabetes mellitus is becoming relevant with growing age. The influence of an anti-Pseudomonas chemotherapy on glucose homeostasis of cystic fibrosis patients was investigated. Patients and methods. In fourteen cystic fibrosis patients aged between 7 and 35 years glucose tolerance was tested by standard oral glucose tolerance test in the beginning and at the end of a routine anti-Pseudomonas chemotherapy of fourteen days. Beside the blood glucose serum insulin was determinated. Results. According to the criteria of the American Diabetes Association three of the fourteen patients had an impaired glucose tolerance and another three had diabetes mellitus when tested at the beginning of anti-Pseudomonas chemotherapy. In four of these six patients glucose tolerance was normal at the end of the chemotherapy. Of the remaining two patients one fulfilled the criteria for impaired glucose tolerance and one for diabetes mellitus. In these patients insulin secretion was lower in the second test. Peak insulin was reached earlier while there was no significant improvement of early insulin response. Conclusion. The treatment of chronic airway infection in cystic fibrosis patients with impaired glucose tolerance or diabetes mellitus results in an improvement of glucose homeostasis by a better insulin sensitivity and less by improvement of early insulin response. In developing diagnostic protocols for screening of cystic fibrosis-related diabetes mellitus the impact of the concomitant therapy on glucose homeostasis should be considered.     

Glucose intolerance in cystic fibrosis patients

Diabetes mellitus has evolved as a complication because of increased longevity of patients with cystic fibrosis (CF). CF-related diabetes (CFRD) is associated with increased morbidity and mortality, therefore, prompt diagnosis and aggressive management are important.The prevalence of CFRD increases with age with an age-dependent incidence rate of 5% per year; at 30 years 50% of patients are diabetic. CFRD develops insidiously. Screening by measurements of fasting, random plasma glucose or glycated haemoglobin A(1c), alone or in combination, do not reliably identify CFRD as compared with the 2-hour plasma glucose value measured during an oral glucose tolerance test.Reasons for the development of CFRD are not fully understood. Generally, patients are characterised by the presence of a class I, II or III CF mutation, exocrine pancreatic insufficiency, impaired and delayed insulin secretion, impaired glucagon secretion, normal insulin sensitivity and an increased insulin clearance rate. One can speculate that for endocrine dysfunction to deteriorate from normal to impaired glucose tolerance and then to CFRD, there must be an additional diabetes mellitus-related genetic defect.CFRD leads to deterioration of overall clinical CF status but insulin therapy can revert this. Late diabetic complications may develop as in other types of diabetes although macrovascular complications are rare. CFRD patients have an increased mortality compared to non-diabetic CF patients. Insulin therapy is the preferred treatment.     

Vitamin A deficiency and nocturnal vision in teenagers with cystic fibrosis

The aim of this study was to document plasma retinol status and nocturnal vision in ten eutrophic adolescents with cystic fibrosis (CF) receiving daily retinol supplementation. Plasma retinol, α and β carotenes and retinol binding protein were measured in ten clinically stable CF patients (mean age: 14.3 years; Shwachman score: 80–100). Nocturnal vision evaluation was performed with a Beyne optometer. Plasma retinol (mean 0.42 ± 0.16 mg/l), α carotene and β carotene levels were below the lower limit of normal in all but one patient. Five out of ten patients with normal standard opthalmological examination presented a poor (n=3 patients) or a pathological (n=2) dark adaptation test. These two patients showed a dramatic increase in nocturnal vision after 1 year of adapted retinol supplementation. Conclusion Low vitamin A levels occur frequently in clinically stable, eutrophic and retinol supplemented CF adolescents. Since vitamin A deficiency is asso-ciated with poor nocturnal vision and since this pattern can be reversed by adapted retinol supplementation, we recommend monitoring plasma vitamin A levels in CF patients and evaluation of dark adaptation in retinol deficient patients. Received: 6 December 1996 / Accepted in revised form: 18 June 1997     

Skinfold measurements in children with cystic fibrosis: monitoring fat-free mass and exercise effects

Monitoring fat free mass (FFM), an indicator of nutritional status and a predictor of exercise performance in children, is particularly important in patients with cystic fibrosis (CF). We assessed validity of the skinfold method for measuring FFM, and its changes with exercise training, in children with CF. A total of 14 children with moderately severe symptoms of CF (age 10–18 years) were followed longitudinally and measured three times, before (at 0 and 6 months) and after exercise training (at 12 months). Separately, single measurements were conducted in 12 children with mild symptoms of CF and in 13 healthy controls. FFM was calculated from four skinfold measurements, and compared with estimations from total body water measured with deuterium dilution. The FFM calculated from skinfolds was 1.7% (P < 0.05) and 3.3% (P < 0.005) higher than that estimated with deuterium oxide dilution in patients with CF and controls, respectively. Limits of agreement were similar in patients with moderate and mild symptoms and in controls. The measurements in patients with moderate symptoms showed similar bias and limits of agreement at 6 and 12 months as compared to 0 months. Changes in FFM measured with both methods were significantly correlated before exercise (r = 0.82, P < 0.0005), and after exercise training (r = 0.60, P < 0.05). Conclusion In children with cystic fibrosis, skinfold measurements are applicable to monitor fat free mass irrespective of clinical severity of the disease, and repeated measurements at intervals of 6 months are applicable to monitor changes in fat free mass during exercise training. Received: 15 September 1998 / Accepted in revised form: 22 February 1999     

Continuous glucose monitoring system in the screening of early glucose derangements in children and adolescents with cystic fibrosis

BACKGROUND: In cystic fibrosis (CF), diabetes mellitus (DM) is associated with progression of pulmonary disease and nutritional impairment. AIM: To compare oral glucose tolerance test (OGTT) and continuous glucose monitoring system (CGMS) in patients with CF with early glucose derangements. PATIENTS AND METHODS: Thirty-two patients with CF (5-20 years) with intermediate glucose values > 7.7 mmol/l during OGTT received a CGMS registration. Patients were classified into those with normal glucose tolerance (NGT), impaired glucose tolerance (IGT) and DM, according to glucose values at 120 min of OGTT and during CGMS. Furthermore BMI z-scores, forced expiratory volume in 1 second (FEV1%), number of respiratory infections/year, enzyme supplementation, and HbA1c were evaluated. RESULTS: OGTT and CGMS derangements were in agreement in 43.7% of the patients. BMI z-scores, FEV1%, number of respiratory infections/ year, enzyme supplementation, and HbA1c did not differ among the three groups. HbA1c, correlated positively with 120 min OGTT (r = 0.34; p = 0.059), CGMS area (r = 0.35; p = 0.048) and the number of respiratory infections, and negatively with FEV1%. CONCLUSIONS: Intermediate glucose values during OGTT should be considered as a screening test in patients with CF. CGMS can be useful in studying the early occurrence of glucose derangements in selected patients.     

Silastic catheters for home antibiotic therapy in patients with cystic fibrosis

Repeated 14-day courses of intravenous antibiotic therapy for patients with cystic fibrosis (CF), who have been colonized with Pseudomonas aeruginosa (PA), is one currently accepted treatment. Conventional intravenous cannulas for antibiotic delivery often have a short line life leading to frequent venipunctures. Therefore we used silastic catheters as a peripheral venous access. Silastic catheters (15 cm, 0.6 mm diameter) were inserted 10 cm into a cubital vein in 15 patients with CF (age 5–32 years) for 20 antibiotic courses. After the antibiotic infusion the catheter was flushed with 200 U heparin (2 ml Vetren). In all patients the antibiotic therapy was delivered as a home therapy. In 15 antibiotic courses the silastic catheter could be continuously used for 14 days. One patient with methicillin resistant Staphylococcus aureus received antibiotic therapy for 54 consecutive days using the same silastic catheter. The catheter had to be removed in four courses: once because of thrombophlebitis with local inflammation, once because of burning pain during infusion and occlusion twice. In one case the patient removed his catheter because of technical problems. No other serious side effects occurred. Ten patients had previously received intravenous antibiotics at least once. The median line life of the last used conventional peripheral cannula of all patients was 4 days versus 14 days with the use of the silastic catheter (P < 0.005). All patients preferred the silastic catheter to other venous access. Conclusion Because of the long line life and easy handling, silastic catheters may be an alternative venous access to perform home antibiotic therapy in patients with CF. Received: 9 May 1996 / Accepted: 24 September 1996     

Carbohydrate metabolism changes in cystic fibrosis

AIMS: To assess the prevalence of impaired glucose tolerance (ITG) and diabetes mellitus (DMRCF) in a group of patients with cystic fibrosis (CF). To study clinical status-related variables and to compare age with the evolution of their carbohydrate metabolism (CHM). PATIENTS AND METHODS: Thirty patients with CF (1.5-26 years). Oral glucose tolerance test (OGTT) in 28 patients. RESULTS: Three patients (10%) showed ITG and four DMRCF (13.3%). CF patients with impaired CHM (ICHM) were older (p = 0.006), and had longer times since diagnosis and first sputum colonization (p = 0.001, p < 0.001). Homozygous deltaF508 mutation was significant (p = 0.001). Insulin peak, area under the curve for insulin, insulin resistance, insulin sensitivity, and pancreatic beta-cell function were all significant. CONCLUSIONS: ICHM was present in 23.3%. Age, time since diagnosis of CF, first sputum colonization and homozygous deltaF508 mutation were significantly associated. CHM in patients with CF is similar to that in the population without CF in the early years.     

Identification of novel mutations in Arabs with cystic fibrosis and their impact on the cystic fibrosis transmembrane regulator mutation detection rate in Arab populations

The cystic fibrosis transmembrane regulator (CFTR) gene in Arab patients with cystic fibrosis (CF) (sweat chloride >60 mmol/l) from 61 unrelated families was screened for mutations in exons 3, 4, 5, 7, 10, 11, 16 and 19 and for mutations W1282X, N1303K and 3849 + 10kbC → T. Eight novel mutations were identified. These are: in exon 4: a) 425del42 (an in-frame 42 bp deletion that removes 14 amino acids and causes Gln₉₈ → His at the point of deletion), b) 475G → T (Glu₁₁₅ → Stop) and c) 548A → T (His₁₃₉ → Leu); in intron 5, 711 + 1G → A (splice site mutation); in exon 10, 1548delG (deletion of a “G” nucleotide causing a frameshift mutation that alters the amino acid sequence at residue 473 and results in translation termination at residue 526); in exon 11, a) 1729T → C (Ph₅₃₃E → Leu) and b) 1811 + 2 (splice site mutation) and finally in exon 19, 3361A → T (Lys₁₁₇₇ → Stop). All mutations were detected by heteroduplex analysis and identified by sequencing. Of more than 850 known CFTR mutations, only 9 were encountered. The comparative frequencies of the most common mutations are: 1548delG> I123V=ΔF508=3120 + 1G → A > H139L. Screening for these five mutations identifies 60% of the CF alleles in Arab populations. The novel mutation 1548delG is the most frequent (17%) among Arabs. Conclusion Novel Arab-specific mutations were identified in the CFTR gene underlying cystic fibrosis. As a result of this study, the CFTR mutation detection rate among Arabs with cystic fibrosis is now comparable to that of other populations. Received: 18 December 1998 / Accepted: 14 May 1999     

Glucose Tolerance and Insulin Receptor Binding to Monocytes and Erythrocytes in Patients with Cystic Fibrosis

ABSTRACT. Cystic fibrosis (CF) is the most frequent life threatening hereditary disease in the Western World with an incidence of approximately 1:2000. Due to increasing survival rates the high frequency of abnormal glucose tolerance has become an important problem. We compared insulin concentrations during oral glucose tolerance test and insulin receptor binding to both monocytes and erythrocytes from 9 patients with CF, with results from 10 healthy controls of similar body weight. The insulin: glucose ratio was increased in the fasting state ( p < 0.05) in patients with CF compared to controls, indicating an increased insulin resistance in CF-patients. The total insulin secretion during oral glucose tolerance test as judged by the area beneath the insulin curve was similar in the two groups, but insulin secretion was significantly delayed in patients with CF. Insulin receptor binding to monocytes and the number of receptors were significantly increased ( p < 0.01 and 0.02, respectively) in patients with CF whereas the dissociation constant was similar in patients with CF and controls. No difference was observed in insulin receptor binding to erythrocytes between the two groups. No correlations were found between insulin receptor binding to monocytes or erythrocytes and glucose tolerance or insulin concentrations.     

Insulin resistance in a young man with cystic fibrosis

An 18-year-old man had cystic fibrosis (CF) and insulin-resistant carbohydrate intolerance characterized by (1) obesity, basal hyperinsulinemia, and hyperglucagonemia; (2) impaired oral glucose tolerance; (3) hyperinsulinemia in response to oral and intravenous (IV) administration of glucose and to IV administration of tolbutamide; (4) exaggerated gastric inhibitory polypeptide secretion following orally administered glucose; and (5) diminished sensitivity to insulin administered IV compared with other patients with CF. Both parents also demonstrate basal and stimulated hyperinsulinemia in response to orally administered glucose. The long-term outlook for patients with CF is improving, and more patients are surviving childhood. Thus, it should be recognized that an insulin-resistant form of carbohydrate intolerance may develop in patients with CF with obesity and/or genetic risk factors.