Microplastics Reduce Lipid Digestion in Simulated Human Gastrointestinal System

Area of Science:

• Environmental Science
• Biochemistry
• Toxicology

Background:

• Microplastics (MPs) are pervasive environmental contaminants.
• Human ingestion of MPs is unavoidable, yet their impact on gastrointestinal processes remains largely unknown.
• Understanding MP effects on lipid digestion is crucial for human health assessment.

Purpose of the Study:

• To investigate the impact of various microplastic types on in vitro lipid digestion.
• To elucidate the mechanisms by which microplastics inhibit lipid digestion.
• To assess the role of microplastic properties (type, concentration, size, photoaging) in digestion inhibition.

Main Methods:

• In vitro gastrointestinal digestion model simulating the human small intestine.
• Analysis of lipid digestion inhibition by five different microplastic types at 80 mg/L.
• Confocal imaging to visualize interactions between microplastics, lipid droplets, and lipases.
• Molecular dynamics simulations to explore interaction mechanisms and binding energies.

Main Results:

• All five tested microplastic types significantly reduced lipid digestion.
• Polystyrene (PS) MPs exhibited the highest inhibition (12.7%), with effects increasing with PS concentration but independent of size.
• Photoaged PS MPs also significantly decreased lipid digestion.
• Two inhibition mechanisms identified: formation of lipid-MP heteroaggregates and lipase adsorption/inactivation.
• Lipid-MP interaction was identified as the dominant inhibitory mechanism.

Conclusions:

• Microplastics, particularly polystyrene, pose a significant risk to human lipid digestion and nutrient assimilation.
• The hydrophobicity of MPs facilitates interactions with lipid droplets, reducing their bioavailability.
• Microplastic adsorption to lipase alters its structure and function, further impairing digestion.
• These findings underscore the potential health implications of microplastic ingestion.