title: Relationship of serum gamma-glutamyltransferase levels with pulmonary function and chronic obstructive pulmonary disease.
abstract: BACKGROUND
  Gamma-glutamyltransferase (GGT) levels within the normal reference range, possibly a biomarker of oxidative stress and/or exposure to various environmental chemicals, are associated with pulmonary function. However, it is unclear whether it is totally independent of cigarette smoking. Also, the potential interaction between serum GGT and cigarette smoking has not ever been evaluated. Therefore, this study investigated (1) whether serum GGT levels are associated with pulmonary function and chronic obstructive pulmonary disease (COPD), independent of cigarette smoking, and (2) whether there is any interaction between serum GGT and cigarette smoking status on pulmonary function.
  
  
  METHODS
  The study subjects were 4,583 participants aged ≥ 40 in the 2010-2011 Korean National Health and Nutrition Examination Survey. The outcomes were pulmonary function (forced expiratory volume in 1 second [FEV1] and forced vital capacity [FVC]) and spirometrically defined COPD.
  
  
  RESULTS
  After adjusting for potential confounders, including cigarette smoking, serum GGT levels were inversely associated with FEV1 and FVC in both genders and positively associated with the risk of COPD in men (all P values < 0.01). In men, adjusted odds ratios of COPD were 1.0, 1.69, 1.97, and 2.02 across the quartiles of GGT level (P trend = 0.002). However, the associations between serum GGT and pulmonary function seemed to differ depending on the smoking status; inverse associations of GGT with FEV1 % and FVC % were clearly observed only among non-current smokers.
  
  
  CONCLUSIONS
  In conclusion, in non-smokers serum GGT levels can be used to detect individuals at high risk of decreased pulmonary function and/or COPD.
authors.affiliation: Department of Family Medicine, Daegu Medical Center, 157 Pyungli-ro, Seo-Gu, Daegu, 703-713, Korea.
authors.forename: Hyun-Woo
authors.initials: HW
authors.lastname: Kim
authors.forename: Seock-Hwan
authors.initials: SH
authors.lastname: Lee
authors.forename: Duk-Hee
authors.initials: DH
authors.lastname: Lee
mesh_terms: D015415:Biomarkers / Q000097:blood; D003430:Cross-Sectional Studies; D005260:Female; D005541:Forced Expiratory Volume; D006801:Humans; D016014:Linear Models; D008168:Lung / Q000503:physiopathology*; D008297:Male; D008875:Middle Aged; D009749:Nutrition Surveys; D016017:Odds Ratio; D015995:Prevalence; D029424:Pulmonary Disease, Chronic Obstructive / Q000097:blood / Q000175:diagnosis / Q000201:enzymology* / Q000453:epidemiology / Q000503:physiopathology*; D056910:Republic of Korea / Q000453:epidemiology; D012307:Risk Factors; D012737:Sex Factors; D012907:Smoking / Q000009:adverse effects / Q000097:blood / Q000453:epidemiology / Q000503:physiopathology; D013147:Spirometry; D015854:Up-Regulation; D014797:Vital Capacity; D005723:gamma-Glutamyltransferase / Q000097:blood*
chemical_list: D015415:Biomarkers; D005723:gamma-Glutamyltransferase; C554782:gamma-glutamyltransferase, human