Metformin to Reduce Airway Glucose in COPD Patients

Chronic obstructive pulmonary disease (COPD) is the 4th leading cause of death worldwide and affects 1.2 million people in the UK, costing the NHS >£800 million annually. COPD patients are more susceptible to bacterial infections and both chronic and acute infections are common. COPD patients with chronic lung bacterial infection have worse quality of life, faster disease progression, more symptoms and frequent exacerbations. Acute infections are the main cause of COPD exacerbations which cause COPD patients to become acutely unwell and often result in hospitalisation especially in the winter. Antibiotics are frequently used to treat COPD exacerbations and this contributes to the development of antibiotic resistance. Therefore there is a need to develop antibiotic-independent approaches to reducing or preventing bacterial infection in COPD. The investigators have carried out work in in animal studies and in humans showing that there is a link between high levels of glucose in the lung and bacterial lung infection. Levels of glucose in the lung are higher in COPD patients compared with people without COPD. These higher glucose levels support greater bacterial growth probably because glucose is a nutrient for bacteria. Therefore reducing airway glucose has the potential to inhibit bacterial growth in COPD patients. In animal studies the investigators have demonstrated that the diabetic drug metformin decreases airway glucose and bacterial growth. The investigators wish to determine if metformin can achieve the same effects in COPD patients. Metformin is safe and cheap, and has been extensively used in COPD patients with diabetes with an excellent safety record. The primary aim of this study will be to determine whether metformin reduces lung glucose in a small group of non-diabetic COPD patients. If it demonstrates that metformin reduces lung glucose concentrations it will justify a larger clinical trial of metformin as a treatment for COPD.