Studies of gamma-glutamyl transferase in alpha-1 antitrypsin deficiency

Gamma-glutamyl transferase (GGT) is a clinical marker of biliary disease, but is also of importance in anti-oxidant metabolic pathways and, consequently, is a potential biomarker of oxidative stress in COPD. Serum GGT is increased in alpha-1 antitrypsin deficiency (AATD) but this could reflect a hepatic, systemic or pulmonary origin. We aimed to investigate the relationship between serum GGT, lung disease, liver disease and mortality in subjects with AATD. Serum GGT was measured at the baseline assessment in 334 PiZ subjects from the UK AATD registry, and related to static lung function, chronic bronchitis, sputum purulence, history of acute exacerbations, smoking status, mortality, alcohol consumption, cirrhosis and serum markers of liver disease. GGT correlated with airflow obstruction and was associated with chronic bronchitis. GGT levels were higher in current smokers compared with ex-smokers and never smokers, and in non-survivors compared with survivors. Although GGT related to alcohol consumption and established liver disease, it was independently related to FEV(1), mortality, smoking history and male gender. In conclusion, although serum GGT reflects the presence of liver disease it is independently associated with airflow obstruction and mortality. Further studies are needed to establish the role of GGT in oxidative lung injury, and its use as a potential biomarker in chronic inflammatory lung disease.