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Hyperglycemia impedes lung bacterial clearance in a murine model of cystic fibrosis-related diabetes

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AJP Lung Cellular and Molecular Physiology

Published online on

Abstract

Cystic fibrosis-related diabetes (CFRD) is the most common co-morbidity associated with cystic fibrosis (CF), impacting more than half of patients over age 30. CFRD is clinically significant, portending accelerated decline in lung function, more frequent pulmonary exacerbations, and increased mortality. Despite the profound morbidity associated with CFRD, little is known about the underlying CFRD-related pulmonary pathology. Our aim was to develop a murine model of CFRD to explore the hypothesis that elevated glucose in CFRD is associated with reduced lung bacterial clearance. A diabetic phenotype was induced in gut-corrected CFTR knockout mice (CFKO) and their CFTR expressing wild-type littermates (WT) utilizing streptozotocin (STZ). Mice were subsequently challenged with an intratracheal inoculation of P. aeruginosa (PAO1) (75 µL of 1-5x106 cfu/mL) for 18 h. Bronchoalveolar lavage fluid (BALF) was collected for glucose concentration and cell counts. A portion of the lung was homogenized and cultured as a measure of the remaining viable PAO1 inoculum. Diabetic mice had increased airway glucose compared to non-diabetic mice. The ability to clear bacteria from the lung was significantly reduced in diabetic WT mice and control CFKO mice. Critically, bacterial clearance by diabetic CFKO mice was significantly more diminished compared to non-diabetic CFKO mice, despite an even more robust recruitment of neutrophils to the airways. This finding that CFRD mice boast an exaggerated, but less effective, inflammatory cell response to intratracheal PAO1 challenge presents a novel and useful murine model to help identify therapeutic strategies that promote bacterial clearance in CFRD.