Microplastics from plastic bottles stored at elevated temperatures (60°C for 7 days) caused significant liver damage and fatty liver disease in zebrafish after 80 days of exposure at concentrations as low as 10-100 μg/L, while room-temperature stored plastics showed no effect. The thermal aging process fragments PET particles, making them more likely to accumulate in gut tissue (up to 6.524 μg/g) and disrupt intestinal barrier function. This gut damage triggers a cascade of inflammation through the LPS/TLR4/NF-κB pathway, leading to systemic inflammation, insulin resistance, and ultimately fatty liver disease. The research reveals a critical vulnerability in our understanding of microplastic toxicity—that storage conditions fundamentally alter their biological impact. This finding has immediate practical implications given that bottled water frequently experiences high-temperature storage during transport and warehousing. The successful intervention with probiotics (Lactobacillus rhamnosus) and sodium butyrate suggests potential therapeutic approaches targeting gut health. While conducted in zebrafish, the mechanistic pathways identified are highly conserved in mammals, making this a concerning discovery for human health that warrants urgent investigation of real-world exposure scenarios.