Diabetes mellitus is an increasing complication of
cystic fibrosis (CF), as a result of the improved life expectancy. There is clear association between diabetes and increased morbidity and mortality. Lung function and clinical status deteriorate up to 2-4 yr before the diagnosis of CF-related diabetes (CFRD). The aim of our study was to evaluate the effects, on
glucose homeostasis and clinical status, of the early treatment with
insulin glargine in CF patients with
impaired glucose tolerance (IGT). We selected six subjects with IGT diagnosed at oral
glucose tolerance test (OGTT). Median age was 18.12 yr (range 9.2-27.8).
Insulin glargine was administered at the median dosage of 0.3 U/kg/day (range 0.2-0.5). After the initial adjustment of the dosage, no patient manifested
hypoglycemia during treatment. Median
glycosylated hemoglobin (HbA1c) did not show any significant variation during treatment: it was 5.9% at baseline (range 5.5-6.2) and 6.1% (range 5.0-6.7) at the end of follow-up (p=0.496). Median body mass index (BMI) z-score significantly increased during treatment, from -0.95 (range -3.2-+0.6) at baseline to -0.5. (range -3.0-+0.9) at the end of follow-up (p=0.026). Lung function, measured by median forced expiratory volume in the first second (FEV1%), showed a mild but significant improvement during
insulin treatment. It was 72.7% at baseline (range 41.5-98.4) and 76.7% (range 42.0-106.8) at the end of follow-up (p=0.027). No significant variation was found between the number of hospitalizations for clinical exacerbation (no./patient/yr) in the last 2 yr before treatment and during follow-up. Median number at baseline was 1.95/patient/yr (range 1-3) and 2.0/patient/yr (range 1-3) at follow-up (p=0.715). Our data seem to indicate that early
insulin therapy can be safe, no patient manifested
hypoglycemia or other adverse effects during treatment.
Insulin is an anabolic
hormone implicated in both
lipid and
protein metabolism. The appearance of IGT out of
infections can indicate an early
insulin deficiency, with a potential impact on the nutritional and clinical status of the patient, even before the appearance of overt diabetes. Larger controlled trials are necessary to verify if early
insulin therapy is able to reduce the deterioration of nutritional status and lung function associated with the onset of IGT.