Plate Nº 92 · recorded September 29, 2026
Health & Medicine ResearchReported finding
Microplastics Clog Liver Immune Cells and Drive Fat Buildup in Mice
Bacteria-sized microplastics clog the 'stomachs' of liver immune cells in mice, impairing their cleaning role and prompting liver cells to store more fat, a new Nature Metabolism study reports.
By Marcus Bennett4 min read750 words
In brief
- Mice given weekly oral doses of bacteria-sized microplastics for twelve weeks accumulated the particles in liver immune cells (Kupffer cells), which became clogged and malfunctioned.
- The impaired macrophages released stress signals that made surrounding liver cells store more fat, disrupting organ metabolism.
- Ten-times-smaller nanoplastics largely spared the liver but accumulated in brown fat, where they activated heat production.
Microplastics can severely disrupt the work of immune cells in the liver, at least in mice. When these cells swallow plastic particles they cannot digest, they malfunction, and the surrounding liver tissue responds by storing more fat. That is the central result of a joint German-Austrian study led by the University of Bonn, published in the journal Nature Metabolism.
The findings matter because of how much plastic people may be swallowing. Experts estimate that adults ingest up to 5 grams (0.18 ounces) of plastic per week — roughly the weight of a credit card. Whether the results translate to humans remains an open question, but the study offers a concrete mechanism for how plastic in the diet could interfere with metabolism.
The liver's cleaning crew
The cells at the center of the study are called macrophages, literally "eating cells." These immune cells live in virtually every organ of the body, where they patrol for bacteria, diseased cells and foreign material. They engulf these threats and break them into their component parts. Beyond defense, macrophages also help their host organs function properly.
"From working with cell cultures, we've known for several years that macrophages also take up microplastics," explains Professor Elvira Mass from the LIMES Institute at the University of Bonn. "We wanted to know whether that's also the case in a living organism and, if so, what effect it has."
To answer that question, Mass teamed up with research groups from the University of Bonn and the University Hospital Bonn (UKB). They focused on a specific group of macrophages called Kupffer cells. These reside in the sinusoids, the smallest blood vessels of the liver, where they monitor blood arriving from the gut. Any plastic particle that enters the bloodstream through the intestine has to pass by them.
Scaling a credit card down to a mouse
Because young mice weigh only about 20 grams (0.7 ounces), the researchers scaled the human exposure estimate down accordingly. The individual particles they administered were roughly the diameter of an average bacterium.
"We administered microplastics to the animals orally once a week," says Mass, who is also a speaker for the Life and Health Transdisciplinary Research Area (TRA) and a member of the steering committee for the ImmunoSensation3 Cluster of Excellence.
Twelve weeks later, the team examined the animals. "We were able to show that the Kupffer cells had taken up large amounts of microplastics," says Dr. Nikola Makdissi, who ran many of the experiments together with his colleague Dr. Maria Francesca Viola.
A clogged 'stomach'
Normally, macrophages digest whatever they engulf and recycle its building blocks. Plastic resists this process. Instead of breaking down, the particles clog the macrophages' "stomachs" — compartments called lysosomes, which do the cell's digesting.
"On the one hand, this means they can no longer take up pathogens or defective cells," Makdissi explains. "On the other hand, they lack important building blocks that they need for their metabolism."
The clogged cells then react by producing more apolipoproteins. These proteins normally transport fats around the body, but here they act as a kind of molecular stress signal. "The surrounding liver cells detect this signal and respond by storing more fat," Mass says. In other words, the impaired macrophages throw the liver's metabolism out of balance, and fat accumulates as a result.
Size matters
The size of the plastic particles proved decisive. Particles similar in size to bacteria appear particularly harmful to the liver. When the researchers instead gave the mice particles ten times smaller, the picture changed. The "clogging" of the macrophages was much less pronounced, and liver metabolism remained largely unchanged.
These smaller nanoplastics did not simply vanish, though. They accumulated in the brown adipose tissue, or brown fat. Unlike white fat, which stores energy, brown fat burns fat to generate heat. In the mice, the nanoplastics activated the brown adipose tissue and stimulated this heat production.
The researchers now want to investigate this effect in more detail.
Early findings, real limitations
The study looked at mice over twelve weeks, not at humans over a lifetime, so the results should be read with caution. The dose was based on exposure estimates that are themselves uncertain. Still, the work provides a plausible biological pathway — swallowed plastic, clogged immune cells, disturbed fat metabolism — that future research can test in people.
Publication: Nikola Makdissi et al., "Size-dependent plastic exposure disrupts macrophage function and tissue-specific metabolism," Nature Metabolism (2026). DOI: 10.1038/s42255-026-01615-8
via Medical Xpress (Source)
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