The gut microbiota, a key to understanding the health implications of micro(nano)plastics and their biodegradation

Abstract

The effects of plastic debris on the environment and plant, animal, and human health are a global challenge, with micro(nano)plastics (MNPs) being the main focus. MNPs are found so often in the food chain that they are provoking an increase in human intake. They have been detected in most categories of consumed foods, drinking water, and even human feces. Therefore, oral ingestion becomes the main source of exposure to MNPs, and the gastrointestinal tract, primarily the gut, constantly interacts with these small particles. The consequences of human exposure to MNPs remain unclear. However, current in vivo studies and in vitro gastrointestinal tract models have shown that MNPs of several types and sizes impact gut intestinal bacteria, affecting gut homeostasis. The typical microbiome signature of MNP ingestion is often associated with dysbiosis and loss of resilience, leads to frequent pathogen outbreaks, and local and systemic metabolic disorders. Moreover, the small micro‐ and nano‐plastic particles found in animal tissues with accumulated evidence of microbial degradation of plastics/MNPs by bacteria and insect gut microbiota raise the issue of whether human gut bacteria make key contributions to the bio‐transformation of ingested MNPs. Here, we discuss these issues and unveil the complex interplay between MNPs and the human gut microbiome. Therefore, the elucidation of the biological consequences of this interaction on both host and microbiota is undoubtedly challenging. It is expected that microbial biotechnology and microbiome research could help decipher the extent to which gut microorganisms diversify and MNP‐determinant species, mechanisms, and enzymatic systems, as well as become important to understand our response to MNP exposure and provide background information to inspire future holistic studies.

Microplastics exposure and immunologic response

“…Thus, MPs work like a Trojan horse, bringing with them a series of environmental contaminants that can interact with the mucus that lines the GIT, with epithelial cells, and with the intestinal microbiota, causing cellular responses and various physiological changes. 76,77 MP ingestion acts on the gut microbiome and is associated with dysbiosis, loss of resilience, frequent pathogen outbreaks, and local and systemic metabolic disturbances, 78 in addition to the development of an intestinal microbiota that is positively associated with diseases of the digestive tract, such as Bifidobacterium, Streptococcus, and Sphingomonas, and a decline in the intestinal microbiota beneficial to health (Ruminococcus, Fusobacterium, Coprococcus). 76 Chemical contaminants can be transferred from mother to child through breastfeeding, depending on its duration, and the child's body burden generally reflects the burden of maternal exposure.…”

Micro(nano)plastics in the Human Body: Sources, Occurrences, Fates, and Health Risks

“…Present studies mainly focus on the transformations of MNPs within the respiratory and digestive systems, including their degradation, the release of toxic chemicals, and interactions with other pollutants. MNP degradation in organisms is mainly induced by the gut microflora, reactive oxygen species (ROS), and enzymes, resulting in depolymerization . While gut microflora effectively promote MNP degradation in organisms, current data are limited to insect models .…”

“…MNP degradation in organisms is mainly induced by the gut microflora, reactive oxygen species (ROS), and enzymes, resulting in depolymerization. 123 While gut microflora effectively promote MNP degradation in organisms, current data are limited to insect models. 124 Studies have shown that mealworm larvae degrade commonly used plastics such as PS, PP, PE, poly(vinyl chloride) (PVC), and polylactic acid (PLA).…”

Report of the Scientific Committee of the Spanish Agency for Food Safety and Nutrition (AESAN) on the available evidence in relation to the potential obesogenic activity of certain chemical compounds that may be present in foods

“…Other metabolic disorders recorded after exposure to MNPs are associated with alterations of the intestinal microbiota (Jiménez-Arroyo et al, 2023). It is well known that the loss of diversity of the intestine microbiota, known as intestinal dysbiosis, is related to local effects (digestive) as well as systemic (in other organs and tissues), due to the alteration of physiological homoeostasis, causing metabolic diseases.…”