Relationships of serum CC16 levels with smoking status and lung function in COPD.

BACKGROUND: The club cell secretory protein (CC16) has anti-inflammatory and antioxidant effects, and low CC16 serum levels have been associated with both risk and progression of COPD, yet the interaction between smoking and CC16 on lung function outcomes remains unknown. METHODS: Utilizing cross-sectional data on United States veterans, CC16 serum concentrations were measured by ELISA and log transformed for analyses. Spirometry was conducted and COPD status was defined by post-bronchodilator FEV1/FVC ratio < 0.7. Smoking measures were self-reported on questionnaire. Multivariable logistic and linear regression were employed to examine associations between CC16 levels and COPD, and lung function with adjustment for covariates. Unadjusted Pearson correlations described relationships between CC16 level and lung function measures, pack-years smoked, and years since smoking cessation. RESULTS: The study population (N = 351) was mostly male, white, with an average age over 60 years. An interaction between CC16 and smoking status on FEV1/FVC ratio was demonstrated among subjects with COPD (N = 245, p = 0.01). There was a positive correlation among former smokers and negative correlation among current or never smokers with COPD. Among former smokers with COPD, CC16 levels were also positively correlated with years since smoking cessation, and inversely related with pack-years smoked. Increasing CC16 levels were associated with lower odds of COPD (ORadj = 0.36, 95% CI 0.22-0.57, Padj < 0.0001). CONCLUSIONS: Smoking status is an important effect modifier of CC16 relationships with lung function. Increasing serum CC16 corresponded to increases in FEV1/FVC ratio in former smokers with COPD versus opposite relationships in current or never smokers. Additional longitudinal studies may be warranted to assess relationship of CC16 with smoking cessation on lung function among subjects with COPD.

Association of Dietary Fiber on Asthma, Respiratory Symptoms, and Inflammation in the Adult National Health and Nutrition Examination Survey Population.

Rationale: High intake of dietary fiber may have antiinflammatory properties and be protective against respiratory morbidity.Objectives: We examined the relationship between dietary fiber intake and asthma, respiratory symptoms, and inflammation among adults who participated in the 2007 to 2012 NHANES (National Health and Nutrition Examination Survey).Methods: We analyzed data from adults 20 to 79 years of age (n = 13,147) with complete information on fiber intake, total calorie intake, body mass index, smoking status, and poverty level. Fiber intake was categorized into quartiles, with Q1 being lowest quartile of intake and Q4 being the highest quartile. Respiratory morbidities included asthma, wheeze, cough, and phlegm. Self-report questionnaires were used to define asthma, wheeze, cough, and phlegm production. Serum C-reactive protein (CRP) was used as a biomarker of inflammation. Exclusion criteria included current pregnancy and implausible intake of total calories.Results: A total of 69.5% of participants were non-Hispanic white; 54.5% were nonsmokers, and 7.8% had current asthma. After adjusting for covariates, fiber intake was associated with asthma (P = 0.01), with an increased odds of asthma with lower fiber intake (Q1 vs. Q4: odds ratio [OR], 1.4; 95% confidence interval [CI], 1.0-1.8; P = 0.027). There were significant interactions between fiber and sex and fiber and race/ethnicity; stronger associations were seen for women and for non-Hispanic white adults. Low fiber intake (Q1) was associated with increased odds of wheeze (OR, 1.3; 95% CI, 1.0-1.6; P = 0.018), cough (OR, 1.7; 95% CI, 1.2-2.3; P = 0.002), and phlegm (OR, 1.4; 95% CI, 1.1-2.0; P = 0.021) compared with high fiber intake. The odds of having high CRP versus nondetectable CRP were 1.6 times higher in the low-fiber group (Q1) compared with high-fiber group (Q4; OR, 1.6; 95% CI, 1.0-2.5).Conclusions: High-fiber diet may mediate an inflammatory response and decrease odds of having asthma, especially for women and specific racial groups, cough, wheeze, and phlegm production when compared with low-fiber diet.