Lipid Metabolism and Oxidative Stress Altered in Crucian Carp (Carassius auratus) Following Exposure to Microplastics Under Laboratory and Field Conditions

Microplastics are pervasive in aquatic environments; however, their impacts on aquatic organisms at environmentally relevant concentrations remain poorly understood, particularly under field conditions. To address this gap, we employed high-throughput sequencing to assess these impacts under both field and laboratory conditions using crucian carp (Carassius auratus) as a model organism. Following a 4-week exposure in situ, the abundance of intestinal microplastics slightly increased from an initial level of 55.00 ± 59.73 items/fish to 72.67 ± 27.50 items/fish (p > 0.05). Accordingly, a total of 3036 differentially expressed genes (DEGs) were identified in the hepatic transcriptome, with notable enrichment in pathways related to lipid metabolism and oxidative stress. Furthermore, a positive correlation between intestinal microplastic abundance and exposure concentration was observed in fish following a 2-week laboratory exposure to polyamide (PA), with intestinal burdens ranging from 7.50 ± 3.54 to 367.50 ± 17.68 items/fish. The number of DEGs in the hepatic transcriptome, ranging from 41 to 380 items, demonstrated a nonlinear relationship with microplastic levels. Furthermore, these DEGs were primarily enriched in pathways associated with lipid metabolism and oxidative stress, including the PPAR signaling pathway (ko03320) and fatty acid degradation (ko00071). This suggests that microplastics at environmental levels may have detrimental effects on organisms through perturbations in lipid metabolism and oxidative stress. As expected, these findings provide essential insights for evaluating the ecological risks linked to microplastic pollution at environmental levels.