Air pollution linked to fatty liver disease

Metabolism-associated fatty liver disease (MAFLD) is a growing global health challenge and represents a substantial economic burden. A large-scale epidemiological study in China (“Exposure to air pollution is associated with an increased risk of fatty liver disease associated with metabolic dysfunction”), published in the Journal of hepatology, the official journal of the European Association for the Study of the Liver, has identified links between long-term exposure to ambient air pollution and MAFLD. These links are exacerbated by unhealthy lifestyles and the presence of central obesity.

The incidence of MAFLD has increased steadily since the 1980s, currently affecting a quarter of the world’s population and a majority of patients with adult diabetes and is a significant global burden. In Asia, MAFLD increased to 40% between 2012 and 2017. Formerly known as non-alcoholic fatty liver disease (NAFLD), it can progress to end-stage liver disease such as cirrhosis and liver cancer, liver transplantation and death related to the liver.

Animal studies have shown that breathing air pollutants can increase the risk of MAFLD. For example, exposure to fine particles can trigger a non-alcoholic steatohepatitis (NASH) -like phenotype, alter hepatic glucose metabolism, and promote hepatic fibrogenesis.

“Accumulating animal studies have demonstrated the harmful contribution of ambient air pollution (PA) to fatty liver disease associated with metabolic dysfunction (MAFLD), but the corresponding epidemiological evidence is limited. We examined the associations between long-term exposure to PA and the prevalence of MAFLD in a Chinese population, ”the investigators write.

“We conducted a cross-sectional study on 90,086 participants recruited in China from 2018 to 2019. MAFLD was assessed on the basis of radiologically diagnosed fatty liver disease and the presence of overweight / obesity, diabetes mellitus or a metabolic disturbance. Residence-specific air pollutant levels, including particulates with aerodynamic diameters of ≤1 μm (PM1), ≤2.5m (PM2.5) and ≤10 m (PMten) and nitrogen dioxide (NO2), were estimated by validated spatio-temporal models.

“We used logistic regression models to examine AP-MAFLD associations and further assessed potential effect changes based on demographics, lifestyle, central obesity, and diabetes status.

“Increased levels of exposure to the 4 air pollutants were significantly associated with an increased likelihood of MAFLD, with odds ratios (OR) of 1.13 (95% CI 1.10-1.17), 1.29 (1.25-1.34), 1.11 (1.09-1.14) and 1.15 (1.12–1.17) for each 10 g / m3 MP increase1, PM2.5, PMten, and no2, respectively. Other stratified analyzes found that men, current and former alcohol drinkers and smokers, those who consume a high-fat diet, and those with central obesity experience greater adverse effects from exposure to the AP than other individuals.

A large-scale epidemiological study in China identified links between long-term exposure to ambient air pollution and metabolic-associated fatty liver disease. [Journal of Hepatology]

“This study provides evidence that long-term exposure to ambient particles1, PM2.5, PMten, and no2 may increase the chances of MAFLD in the real world. These effects can be exacerbated by unhealthy lifestyle habits and central obesity. “

“The MAFLD epidemic corresponds to the environmental and lifestyle changes that have occurred alongside rapid industrialization around the world, especially in many Asian countries,” said lead researcher Xing Zhao, PhD, West China School of Public Health and West China Fourth Hospital, Sichuan University, Chengdu, Sichuan, China. “A growing number of studies suggest that ambient air pollution, which is the biggest environmental problem caused by industrialization, can increase the risk of metabolic disorders such as insulin resistance and dyslipidemia, and related diseases such as type 2 diabetes and metabolic syndrome.

“However, the epidemiological evidence for the association was limited, so we conducted this research to improve our understanding of the effects of air pollution on human health and also to help reduce the burden of MAFLD.”

Investigators conducted an epidemiological study on the potential role of ambient air pollution in the risk of MAFLD in approximately 90,000 adults in China based on the China Multi-Ethnic Cohort (CMEC) baseline survey. , a prospective cohort that recruited nearly 100,000 participants in southwest China from 2018 to 2019. CMEC collected information on participants, including socio-demographic data, lifestyle and health-related history, through verbal interviews conducted by trained personnel and then evaluated anthropometry, biological samples (blood, urine and saliva) and imaging data.

Researchers have found that long-term exposure to ambient air pollution may increase the risks of MAFLD, especially in men, smokers and alcohol drinkers, and those who consume a high-fat diet. . Unhealthy lifestyle behaviors and excessive accumulation of fat in the abdominal area can exacerbate the harmful effects.

“Our findings add to the growing evidence for the detrimental effects of environmental pollution on metabolic function and associated organs,” commented Zhao and his co-investigators. “However, physical activity does not appear to alter the associations between air pollution and MAFLD. We suggest that future studies explore whether the timing, intensity and form of physical activity may mitigate the effects. harmful air pollution.

Investigators suggest that air pollution be recognized as a modifiable risk factor for MAFLD. High-risk populations should be aware of the air quality in the areas where they live and plan their activities to minimize their exposure to air pollution.

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