Glucose intolerance in cystic fibrosis as a determinant of pulmonary function and clinical status

Background: Cystic fibrosis related diabetes (CFRD) is associated with a decrease in pulmonary function and nutritional status. We investigated the clinical significance of impaired glucose tolerance (IGT) in cystic fibrosis (CF) patients. Methods: Fifty-five CF patients (aged 22.8 +/- 9.2 years, 29 males, mean FEV1 67.9 +/- 22% predicted, mean BMI-SDS - 0.23 +/- 1.1) underwent a 2-h Oral Glucose Tolerance Test (OGTT) with 30-min interval measurements of glucose and insulin. Additional clinical and laboratory data were obtained from the medical charts. Results: Thirty-eight participants (69%) had normal glucose tolerance (NGT), 13 (23.7%) had IGT, and 4 (7.3%) had newly diagnosed CFRD. Compared to patients with NGT, patients with IGT had significantly lower BMI-SDS (-1.1 +/- 0.8 vs. 0.1 +/- 1.1, p < 0.001), mean FEV1 (57 +/- 19 vs. 74 +/- 21% predicted, p < 0.01), and albumin (3.9 +/- 0.3 vs. 4.3 +/- 0.2 g/dl, p = 0.004), and higher fibrinogen (376 +/- 56 vs. 327 +/- 48 g/dl, p = 0.02). Patients with IGT had impaired beta-cell function, with reduced first phase insulin secretion, a delayed insulin peak, and significantly lower total insulin secretion, HOMA-%B and insulinogenic index. Seven patients had HbA1c in the diabetic'' range (>= 6.5%; 47.5 mmol/mol), however, HbA1c was not a sensitive or specific marker of glucose tolerance status. Conclusions: IGT in CF patients is associated with increased inflammation and decreased nutritional status and pulmonary function. (C) 2015 Elsevier Ireland Ltd. All rights reserved.