Background:Smoking and body mass index (BMI) are the key risk factors for chronic obstructive pulmonary disease (COPD).Adiponectin with both anti-inflammatory and pro-inflammatory properties is a vital modulator of inflammatory processes,which is expressed in epithelial cells in the airway in COPD-emphysema.The aim of this study was to examine the effects of adiponectin on tobacco smoke-induced emphysema in rats,which were fed different diets.Methods:Seventy-six adult (6-8 weeks old) male Sprague-Dawley rats (average weight 220 ± 20 g) were exposed to smoke or smoke-free room atmosphere and fed different diets (regular,high-fat,or low-fat diets) for 6 months.The rats were randomly divided into six groups.They are nonsmoke-exposed regular diet (n 10),nonsmoke-exposed high-fat diet (n =14),nonsmoke-exposed low-fat diet (n =14),smoke-exposed regular diet (n ＝ 10),smoke-exposed high-fat diet (n =14),and smoke-exposed low-fat diet groups (n =14).A full 23 factorial design was used to evaluate the effect of independent variables on smoke exposure and different rearing methods.Serum adiponectin and inflammatory cytokines were measured by the enzyme-linked immunosorbent assay (ELISA).Results:Serum adiponectin levels in rats fed low-fat and regular diets exposed to smoke exposure were remarkably higher than that of rats exposed to room air while serum adiponectin levels of fat-rich diet rats exposed to tobacco smoke were lower than that of rats exposed to room air.Compared with regular diet or low-fat diet group,serum adiponectin levels in high-fat diet rats exposed to tobacco smoke were lower (t =6.932,11.026;all P ＜ 0.001).BMI was inversely correlated with serum adiponectin levels (r =-0.751,P =0.012).Serum interleukin 6 (IL-6),tumor necrosis factor-α (TNF-α),and 4-hydroxy 2-nonenal (HNE) levels in rats exposed to low-fat or fat-rich diets were remarkably higher than that of rats exposed to normal diets (IL-6,t =4.196,3.480;P ＜ 0.01,P =0.001;TNF-α,t =4.286,3.521;P ＜ 0.01,P =0.001;4-HNE,t =4.298,4.316;all P ＜ 0.001).In nonhigh-fat diet rats exposed to tobacco smoke,serum adiponectin levels correlated positively with serum IL-6,TNF-α,and 4-HNE,bronchoalveolar lavage cell count,and mean linear intercept.In contrast,in high-fat diet rats,serum adiponectin levels correlated inversely with these parameters.Conclusions:In smoke-induced emphysema and fat-rich diet rat model,serum adiponectin level was decreased,and the anti-inflammatory effect was attenuated.By contrast,nonhigh-fat diet elevated serum adiponectin and enhanced the role of pro-inflammatory.