Are Ingested or Inhaled Microplastics Involved in Nonalcoholic Fatty Liver Disease?

Abstract

Nonalcoholic fatty liver disease (NAFLD) has emerged as the predominant cause of chronic liver injury; however, the mechanisms underlying its progression have not been fully elucidated. Pathophysiological studies have stated that NAFLD is significantly influenced by dietary and environmental factors that could participate in the development of NAFLD through different mechanisms. Currently, "plastic pollution" is one of the most challenging environmental problems worldwide since several plastics have potential toxic or endocrine disputing properties. Specifically, the intake of microplastics (MPs) and nanoplastics (NPs) in water or diet and/or the inhalation from suspended particles is well established, and these particles have been found in human samples. Laboratory animals exposed to MPs develop inflammation, immunological responses, endocrine disruptions, and alterations in lipid and energy metabolism, among other disorders. MPs additives also demonstrated adverse reactions. There is evidence that MPs and their additives are potential "obesogens" and could participate in NAFLD pathogenesis by modifying gut microbiota composition or even worsen liver fibrosis. Although human exposure to MPs seems clear, their relationship with NAFLD requires further study, since its prevention could be a possible personalized therapeutic strategy. Adequate mitigation strategies worldwide, reducing environmental pollution and human exposure levels of MPs, could reduce the risk of NAFLD.

Keywords: NAFLD; microbiota; microplastics; nanoplastics; obesogens.

Figure 1

Microplastics and nanoplastics from plastic degradation enter organisms mainly through the digestive and respiratory systems (from this last system, microplastics pass to the digestive system by swallowing), producing changes in the gut microbiota that could induce intestinal dysbiosis. Intestinal dysbiosis triggers injuries (alterations of metabolic homeostasis, disruption of the intestinal barrier, endotoxaemia, and inflammatory response) that can cause health disorders, such as NAFLD [22,23]. NAFLD, nonalcoholic fatty liver disease; SS, simple steatosis; NASH, nonalcoholic steatohepatitis.