Microplastics in human diet

From the food on our plates to the air we breathe, microplastics are everywhere. Studies on diet have revealed that humans ingest approximately five grams of microplastics per week.

Research on microplastics and immune cells

Research conducted in Germany by scientists at the University of Bonn has found that microplastics may alter the function of phagocytes, a type of white blood cell, in the livers of mice. This could disrupt the metabolism of the organ and increase the accumulation of fats. The findings were published in the journal Nature Metabolism.

Role of phagocytes in the immune system

Phagocytes are immune cells present in almost all organs of the body and play an essential protective role by detecting bacteria, sick cells, and traces of foreign bodies, ingesting and decomposing them. "Thanks to our work on cell cultures, we have known for several years that macrophages also absorb microplastics," explains Professor Elvira Mass from the LIMES Institute at the University of Bonn. She adds: "We wanted to know if this phenomenon also occurs in a living organism and, if so, what the effects are."

Impact of microplastics on macrophages

In the context of this study, the researchers administered microplastics to the animals orally once a week. Twelve weeks later, the animals were examined. "We were able to demonstrate that Kupffer cells had absorbed large amounts of microplastics," explains Dr. Nikola Makdissi. Macrophages usually digest what they ingest and recycle its components. However, plastic cannot be decomposed and thus blocks the "stomachs" of macrophages according to the conclusions of this study. "On the one hand, this means that they can no longer absorb pathogens or defective cells. On the other hand, they are deprived of essential elements for their metabolism," points out Dr. Makdissi.

Microplastics and liver function

Another finding from this study is that the white blood cells of the liver reacted to this exposure by producing more apolipoproteins, proteins that normally transport fats in the body. Here, they act as a kind of molecular stress signal. "The surrounding liver cells detect this signal and respond by storing more fats," warns Professor Mass. According to the results of this study, the disruption of the function of macrophages could therefore lead to a metabolic imbalance in the liver. Metabolic steatosis, commonly nicknamed fatty liver disease, is associated with the metabolic syndrome and is characterized by the accumulation of fats in the liver, outside of excessive alcohol consumption.