Patients with cystic fibrosis and normoglycemia exhibit diabetic glucose tolerance during pulmonary exacerbation

Background: Patients with cystic fibrosis and normoglycemia (CF-NGT) have higher but still "normal" glucose levels in the Oral Glucose Tolerance Test (OGTT). Respiratory exacerbation is associated with metabolic stress. The objective of this study was to assess the glucose metabolism and its relation to the steady state pulmonary function (FEV1) in patients with CF-NGT, specifically during pulmonary exacerbations (PE). Methods: CF-NGT patients who were not on steroids, underwent OGTT and intravenous glucose tolerance tests (IVGTT) during PE and 4. weeks after complete recovery. Results: Of the ten recruited patients two had diabetic OGTT and were excluded. The remaining normoglycemic patients displayed during PE a diabetic glucose tolerance with mean glucose levels of 233 ± 8 and 262 ± 11. mg/dl at 90 and 120. min respectively, compared with normal levels of 154 ± 21and 126 ± 20. mg/dl (p< 0.002) during the steady state. IVGTT showed a tendency to higher first phase insulin release during PE compared with the steady state.(min 3; 305 ± 80 vs. 216 ± 40. pmol\l p= 0.075). Finally, when relating the diabetic status to the general respiratory function we found a negative correlation between baseline FEV1 and glucose levels at 2. h after OGTT during PE (r=-0.88, p= 0.002). Conclusion: In this pilot study we show that during PE patients with CF and normal glucose tolerance exhibited early latent diabetic glucose intolerance. As this hyperglycemia presents in the later parts of the OGTT it probably results from insufficient second phase insulin secretion during PE. The negative correlation observed here between the diabetic glucose tolerance and FEV1 indicate the need of interventional studies using insulin during PE in non-diabetic patients to determine its potential benefit on the outcome from recurrent PEs.