The mediation role of blood lipids on the path from air pollution exposure to MAFLD: A longitudinal cohort study

Xinyu Han; Bing Guo; Lele Wang; Kejun Chen; Hanwen Zhou; Shourui Huang; Huan Xu; Xianmou Pan; Jinyao Chen; Xufang Gao; Zhenghong Wang; La Yang; Ciren Laba; Qiong Meng; Yuming Guo; Gongbo Chen; Feng Hong; Xing Zhao; China Multi-Ethnic Cohort (CMEC) collaborative group

doi:10.1016/j.scitotenv.2023.166347

The mediation role of blood lipids on the path from air pollution exposure to MAFLD: A longitudinal cohort study

Sci Total Environ. 2023 Dec 15:904:166347. doi: 10.1016/j.scitotenv.2023.166347. Epub 2023 Aug 15.

Authors

Xinyu Han¹, Bing Guo¹, Lele Wang¹, Kejun Chen¹, Hanwen Zhou¹, Shourui Huang¹, Huan Xu², Xianmou Pan¹, Jinyao Chen¹, Xufang Gao³, Zhenghong Wang⁴, La Yang⁵, Ciren Laba⁶, Qiong Meng⁷, Yuming Guo⁸, Gongbo Chen⁹, Feng Hong¹⁰, Xing Zhao¹¹; China Multi-Ethnic Cohort (CMEC) collaborative group

Affiliations

¹ West China School of Public Health and West China Fourth Hospital, Sichuan University, Chengdu, Sichuan, China.
² West China School of Public Health and West China Fourth Hospital, Sichuan University, Chengdu, Sichuan, China; Institute for Disaster Management and Reconstruction, Sichuan University-The Hongkong Polytechnic University, Chengdu, Sichuan, China.
³ Chengdu Center for Disease Control and Prevention, Chengdu, Sichuan, China.
⁴ Chongqing Municipal Center for Disease Control and Prevention, Chongqing, China.
⁵ Tibet University, Lhasa, Tibet, China.
⁶ Tibet Center for Disease Control and Prevention CN, Lhasa, Tibet, China.
⁷ Department of Epidemiology and Health Statistics, School of public Health, Kunming Medical University, Kunming, Yunnan, China.
⁸ Department of Epidemiology and Preventive Medicine, School of Public Health and Preventive Medicine, Monash University, Melbourne, VIC 3004, Australia.
⁹ Climate, Air Quality Research Unit, School of Public Health and Preventive Medicine, Monash University, Melbourne, Australia. Electronic address: gongbo.chen1@monash.edu.
¹⁰ School of Public Health, the key Laboratory of Environmental Pollution Monitoring and Disease Control, Ministry of Education, Guizhou Medical University, Guiyang, China. Electronic address: fhong@gmc.edu.cn.
¹¹ West China School of Public Health and West China Fourth Hospital, Sichuan University, Chengdu, Sichuan, China. Electronic address: xingzhao@scu.edu.cn.

PMID: 37591384
DOI: 10.1016/j.scitotenv.2023.166347

Abstract

Background & aims: Recent cross-sectional studies found that exposure to ambient air pollution (AP) was associated with an increased risk of metabolic dysfunction-associated fatty liver disease (MAFLD). The alternation of blood lipids may explain the association, but epidemiological evidence is lacking. We aimed to examine whether and to what extent the association between long-term exposure to AP and incident MAFLD is mediated by blood lipids and dyslipidemia in a prospective cohort.

Methods: We included 6350 participants from the China Multi-Ethnic Cohort (CMEC, baseline 2018-2019, follow-up 2020-2021). Three-year average (2016-2018) of AP (PM₁, PM_2.5, PM₁₀, NO₂), blood lipids (TC, LDL-C, HDL-C, TG with their combinations) and incident MAFLD for each individual were assessed chronologically. Linear and logistic regression was used to assess the associations among AP, blood lipids, and MAFLD, and the potential mediation effects of blood lipids were evaluated using causal mediation analysis.

Results: A total of 744 participants were newly diagnosed with MAFLD at follow-up. The odds ratios of MAFLD associated with a 10 μm increase in PM₁, PM_2.5, and NO₂ were 1.35 (95 % CI: 1.14, 1.58), 1.34 (1.10, 1.65) and 1.28 (1.14, 1.44), respectively. Blood lipids are important mediators between AP and incident MAFLD. LDL-C (Proportion Mediated: 6.9 %), non-HDL (13.4 %), HDL-C (20.7 %), LDL/HDL (30.1 %), and dyslipidemia (6.5 %) significantly mediated the association between PM_2.5 and MAFLD. For PM₁, the indirect effects were similar to those for PM_2.5, with a larger value for the direct effect, and the mediation proportion by blood lipids was less for NO₂.

Conclusion: Blood lipids are important mediators between AP and MAFLD, and can explain 5 %-30 % of the association between AP and incident MAFLD, particularly cholesterol-related variables, indicating that AP could lead to MAFLD through the alternation of blood lipids. These findings provided mechanical evidence of AP leading to MAFLD in epidemiological studies.

Keywords: Air pollution; Blood lipids; Causal mediation effect; MAFLD.

MeSH terms

Air Pollutants* / analysis
Air Pollution* / analysis
China / epidemiology
Cholesterol, LDL
Cohort Studies
Dyslipidemias* / chemically induced
Dyslipidemias* / epidemiology
Environmental Exposure / analysis
Humans
Lipids
Longitudinal Studies
Nitrogen Dioxide / analysis
Particulate Matter / adverse effects
Particulate Matter / analysis
Prospective Studies

Substances

Air Pollutants
Nitrogen Dioxide
Particulate Matter
Cholesterol, LDL
Lipids