Glucose homeostasis and genotype-phenotype interplay in cystic fibrosis patients with CFTR gene deltaF508 mutation.
OBJECTIVE
We sought to determine the clinical phenotype of adolescent/adult patients with cystic fibrosis, according to heterozygosity or homozygosity for cystic fibrosis transmembrane regulator (CFTR) deltaF508 mutation, and to analyze their characteristics according to glucose tolerance status.


METHODS
A total of 76 cystic fibrosis patients with CFTR deltaF508 mutation (33 heterozygous and 43 homozygous) stratified according to normal glucose tolerance (NGT) (n = 51) or abnormal glucose homeostasis (AGH) (impaired fasting glucose, impaired glucose tolerance, or diabetes; n = 25) had their homeostasis model assessment (HOMA) of beta-cell function and of insulin sensitivity and hyperbolic product (beta-cell function x insulin sensitivity [B x S]) measured. Pancreatic exocrine insufficiency was inferred from pancreatine requirements. Clinical effects of insulin therapy on weight and lung function were recorded.


RESULTS
AGH was observed in 24 and 40% of heterozygous and homozygous subjects, respectively. AGH patients were older than NGT patients (mean +/- SD age 29 +/- 10 vs. 23 +/- 8 years, P = 0.006), and their beta-cell function was lower (93 +/- 49 vs. 125 +/- 51%, P = 0.011). Insulin sensitivity values were comparable in NGT and AGH patients. A lower B x S product was observed in AGH, although it was nonsignificant when adjusted for error propagation. Pancreatic insufficiency was observed in 52 and 100% of heterozygous and homozygous patients (P = 0.001).


CONCLUSIONS
Pre-diabetes and diabetes represent frequent comorbidities in CFTR deltaF508 mutation in the homozygous or heterozygous states. Impairment of insulin secretion, as shown by HOMA, is an important determinant when compared with the magnitude of compensation from insulin sensitivity. Given the high prevalence of abnormal glucose tolerance, screening for (pre-)diabetes is mandatory. Insulin supplementation in diabetic subjects with CFTR deltaF508 mutation seems a rational therapy for consideration, although this does not preclude that therapy directed toward insulin resistance could also interact.
Preumont
Vanessa
V
Department of Endocrinology and Nutrition, Université Catholique de Louvain, Cliniques Universitaires St-Luc, Brussels, Belgium.
Hermans
Michel P
MP
Lebecque
Patrick
P
Buysschaert
Martin
M
D000293:Adolescent; D000328:Adult; D017668:Age of Onset; D003550:Cystic Fibrosis / Q000235:genetics* / Q000378:metabolism; D019005:Cystic Fibrosis Transmembrane Conductance Regulator / Q000235:genetics*; D003920:Diabetes Mellitus / Q000188:drug therapy; D005260:Female; D006580:Genetic Carrier Screening; D005838:Genotype; D005947:Glucose / Q000378:metabolism*; D018149:Glucose Intolerance / Q000235:genetics; D006706:Homeostasis; D006720:Homozygote; D006801:Humans; D007328:Insulin / Q000627:therapeutic use; D008297:Male; D009154:Mutation; D009752:Nutritional Status; D010641:Phenotype; D011236:Prediabetic State / Q000150:complications / Q000188:drug therapy
C505032:CFTR protein, human; D007328:Insulin; D019005:Cystic Fibrosis Transmembrane Conductance Regulator; D005947:Glucose