Microplastics Reduce Lipid Digestion in Simulated Human Gastrointestinal System

-glycolic acid) (80 mg/L in small intestine), significantly reduced lipid digestion in the in vitro gastrointestinal system. PS MPs exhibited the highest inhibition (12.7%) among the five MPs. Lipid digestion decreased with increasing PS concentration, but independent of PS size (50 nm, 1 μm, 10 μm). PS MPs after photoaging by simulated sunlight also significantly decreased lipid digestion. Confocal imaging shows that PS MPs could interact with both lipid droplets and lipases. Two mechanisms underlying the PS-induced digestion inhibition were revealed using both experimental and molecular dynamics simulation approaches: (1) PS MPs decreased the bioavailability of lipid droplets via forming large lipid-MPs heteroaggregates due to the high MP hydrophobicity; and (2) PS MPs adsorbed lipase, and reduced its activity by changing the secondary structure and disturbing the essential open conformation. The first mechanism (MP-lipid interaction) played a more important role in lipid digestion reduction based on interaction energy calculation. These findings reveal potential risk of MPs to human digestion health and nutrient assimilation.