Biodegradable microplastics in mice gut trigger metabolic reprogramming, shedding light on safety concerns (May 2025) Incorporation of polylactic acid microplastics into the carbon cycle as a carbon source to remodel the endogenous metabolism of the gut Study

[Michael Harrop]

https://medicalxpress.com/news/2025-05-biodegradable-microplastics-mice-gut-trigger.html
https://www.pnas.org/doi/10.1073/pnas.2417104122

Microplastic pollution is a severe ecological and environmental issue and is also one of the important risk factors affecting human health. Polylactic acid (PLA), a medical biodegradable material approved by the FDA, is an important material to replace petroleum-based plastics.

Although PLA has achieved large-scale application in food packaging, its brittle characteristics make it more likely to generate microplastic particles. These particles can efficiently invade the gut through the food chain and trigger unknown biotransformation processes at the microbiota–host interface. Therefore, elucidating precisely the transformation map of PLA microplastics within the living body is crucial for assessing their safety.

Ultimately, their entry into the gut carbon cycle triggers metabolic reprogramming, reducing short-chain fatty acid production, disrupting energy homeostasis, and reallocating carbon flux. This leads to suppressed host feeding behavior and significant weight loss.

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More bad news for bioplastics

Significance​

The growing presence of polylactic acid microplastics (PLA-MPs) in aqueous and alimentary contexts has led to increased oral exposure. Understanding primary biological processes of PLA-MPs in the gut is crucial for assessing their potential impact on the host health. We clarified the degradation source of PLA-MPs in the gut and revealed the incorporation of PLA-MPs into the metabolic flux of gut microbiota and epithelial cells as a carbon source in vivo using the 13C isotope tracing technique, thereby entailing a distinct biological fate of biodegradable plastics in mammals.

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Abstract​

Biodegradable polylactic acid (PLA) plastics have been praised as an effective solution to the global pollution caused by petroleum-based plastics, and their widespread use in food packaging and disposable tableware has resulted in increased oral exposure to PLA microplastics (PLA-MPs). Despite their eco-friendly and biodegradable reputation, the in vivo behaviors of PLA-MPs concerning fermentation, carbon cycle, and adverse effects remain unknown. Here, we showed that gut microbiota from the colon can effectively degrade the PLA-MPs by secreting esterase FrsA, whereas esterase FrsA-producing bacteria were identified to dominate this behavior in male C57BL/6 mice. Using isotope tracing and multiomics techniques, we uncovered that 13C-labeled PLA-MPs were incorporated into the carbon cycle of gut microbiota as a carbon source. Meanwhile, these degraded PLA-MPs fragments entered the succinate pathway of the tricarboxylic acid cycle within gut epithelial cells. These processes altered the metabolic phenotype of the gut, resulting in the decreased linear short-chain fatty acids that are primary energy sources of the gut epithelium. Furthermore, we found that exposure of PLA-MPs significantly reduced the appetite and body weight of mice. Our findings present an overall process of biodegradable plastics within hosts, with the focus on the entire double carbon cycle of PLA-MPs in the gut, which offers indispensable insights into the potential impact of exposure to PLA-MPs.

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