Smoking results in accumulation of ectopic fat in the liver

Ayako Kato,1 Yuanying Li,1 Atsuhiko Ota,1 Hisao Naito,1 Hiroya Yamada,2 Takashi Nihashi,3 Yo Hotta,4 Chifa Chiang,5 Yoshihisa Hirakawa,5 Atsuko Aoyama,5,6 Koji Tamakoshi,7 Hiroshi Yatsuya1,51Department of Public Health, Fujita Health University School of Medicine, Toyoake, Aichi, Japan; 2Department of Hygiene, Fujita Health University School of Medicine, Toyoake, Aichi, Japan; 3Department of Radiology, Komaki City Hospital, Komaki, Aichi, Japan; 4Toyoda Gosei Co., Ltd, Medical and Hygiene Designing Department, Inazawa, Aichi, Japan; 5Department of Public Health and Health Systems, Nagoya University Graduate School of Medicine, Nagoya, Aichi, Japan; 6Nagoya University of Arts and Sciences, Nissin, Aichi, Japan; 7Department of Nursing, Nagoya University School of Health Sciences, Nagoya, Aichi, JapanObjective: An association between smoking and nonalcoholic fatty liver disease has been reported. However, objective quantification of intrahepatic fat via magnetic resonance spectroscopy (MRS) in relation to smoking has rarely been performed in previous studies. Moreover, the possible pathways via which smoking could induce ectopic fat accumulation have not yet been addressed. The current study aimed to examine the association between smoking status and intrahepatic fat quantity and explore the possible mediating effects of triglycerides (TG) and adiponectin.Subjects and methods: Magnetic resonance imager (MRI) spectra were analyzed to quantify intrahepatic fat in 45 men who were on average 62.3 years of age. Smoking status and alcohol intake were self-reported. Accelerometers were used to record daily total physical activity. Fasting blood TG and adiponectin levels were measured enzymatically. Differences in mean intrahepatic fat values according to smoking status were assessed using analysis of covariance.Results: A stepwise increase in mean intrahepatic fat was observed between never, former, and current smokers, respectively, independent of age, physical activity, alcohol intake, and body mass index (BMI) (P=0.005). Adjustment for TG and adiponectin significantly attenuated this association (P=0.074).Conclusion: Current smoking was significantly associated with increased intrahepatic fat, which may be a result of adipocyte dysfunction, manifested as high circulating TG concentrations and low adiponectin levels.Keywords: intrahepatic fat, cigarette smoking, adiponectin, triglycerides, cross-sectional study