Scientific articles analyzed the passage of microplastics into the gut and the brain and how this may relate to changes in the gut’s microbiota community and autism spectrum disorder (ASD).
The fact that microplastics can cross the intestinal epithelial barrier, was recently demonstrated by Joanne M. Donkers from the Netherlands Organization for Applied Scientific Research (TNO), Zeist, Netherlands, and co-authors using advanced in vitro models. Their research published on February 4, 2022, in the journal Microplastics and Nanoplastics further demonstrated that several of the tested nano- and microplastics disrupted barrier integrity and induced pro-inflammatory cell activation.
In an article published on February 3, 2022, in the journal Scientific Reports Alba Tamargo from the Institute of Food Science Research, Madrid, Spain, and co-authors analyzed the modification of polyethylene terephthalate (PET) microplastic particles during their passage through the digestive tract as well as changes in human gut microbiota composition. The researchers created PET fragments of an average size of 160 µm. Subsequently, microplastics in amount corresponding to realistic human exposure levels of ingestion were subjected to simulated digestion. To mimic digestion, they used a standardized in vitro static model and a dynamic computer-based model that simulates the different regions of the gastrointestinal tract.
Tamargo and co-authors observed that colonic fermentation did not alter the irregular morphology of the PET particles but changed their surface. This would indicate that PET microplastics structurally degrade during gastrointestinal digestion. In addition, colonic microbiota were found to adhere to the microplastics’ surface resulting in biofilm formation. Concerning the impact on microbiota, the scientists reported: “microplastic feeding affects both composition and diversity of colonic microbial communities.” Based on their findings the authors think “that microplastics are indeed capable of digestive-level health effects.” They also called for research on microplastic biodegradation when passing through the gastrointestinal tract as well as the impacts on the functionality of the gut microbiome. According to a previously published study, microplastics may drive unhealthy changes in the gut microbiome (FPF reported).
In an article published on February 3, 2022, in the peer-reviewed journal Environment International Javeria Zaheer from Korea Institute Radiological and Medical Sciences, Seoul, South Korea, and co-authors also investigated gut microbiota but in a different context. The authors investigated whether microplastic exposure presents a risk factor for autism spectrum disorder (ASD).
The scientists developed prenatal, post-weaning period, puberty, and adult mouse models reflecting the different life stages in humans. Next, they orally exposed the mice to roughly 20 µm-sized polyethylene (PE) particles in a solution of 100 ppm/100 µl daily. Using scanning electron microscopy (SEM) and confocal microscopy, they found that PE particles accumulated in the brain in concentrations of 1.43 mg/g already after one-week exposure. The particles detected in the brain were smaller (4 µm) than those detected in the gut (20 µm) and concentrations were lower. Thus, Zaheer et al. hypothesized that the particles were digested in the stomach, deposited into the gut and that only smaller PE fragments transitioned into the brain and accumulated there.
As a next step, the researchers analyzed whether PE-exposed mice behaved differently than unexposed mice. Here, they found that particle exposure induced several ASD-like traits during the different life stages, such as increased compulsive and repetitive behaviors. To investigate further ASD-related changes, the scientists analyzed gut microbiota, dopamine transporter signaling, metabolite levels, glucose metabolism, and gene expression in the brain by applying a wide spectrum of methods. Also here, they reported “the induction of ASD-like traits in response to microplastic exposure.” According to the authors their study results “demonstrated a link between environmental pollution during the pre-natal and early post-natal periods and the development of ASD, as a consequence of complex interactions between genetic and non-genetic risk factors.”
Previous studies have reported that exposure to endocrine disruptors can lead to autistic features (FPF reported) and that prenatal exposure to androgens may disrupt brain development, leaving males more susceptible to ASD (FPF reported). Furthermore, exposure to toxic metals such as lead, mercury, and aluminum, was also linked to ASD (FPF reported).
References
Dinkers, J. M. et al (2022). “Advanced epithelial lung and gut barrier models demonstrate passage of microplastic particles.” Microplastics and Nanoplastics. DOI: 10.1186/s43591-021-00024-w
Tamargo, A. et al (2022). “PET microplastics affect human gut microbiota communities during simulated gastrointestinal digestion, first evidence of plausible polymer biodegradation during human digestion.” Scientific Reports. DOI: 10.1038/s41598-021-04489-w
Zaheer, J. et al (2022). “Pre/post-natal exposure to microplastic as a potential risk factor for autism spectrum disorder.” Environment International. DOI: 10.1016/j.envint.2022.107121
