Microcystin-LR induces fatty liver metabolic disease in zebrafish through the PPARα-NOD1 pathway: In vivo, in vitro, and in silico investigations

Hepatic lipid metabolism dysfunction caused by cyanobacteria bloom-released microcystin-LR (MC-LR) contributes to the development of nonalcoholic fatty liver disease and nonalcoholic steatohepatitis (NASH), thereby severely impacting the health and safety of animals and humans. In this study, the effects and mechanisms of different environmental concentrations of MC-LR (0, 0.1, 1, and 10 μg/L) on fatty liver metabolic disease in zebrafish were investigated using in vivo, in vitro, and in silico models. Exposure to 10 μg/L of MC-LR-induced NASH in zebrafish, characterized by hepatic steatosis, toxic saturated fatty acid (SFA) accumulation, and inflammation. Analyses of the liver transcriptome, molecular docking, molecular dynamics simulation, and in vitro experiments indicated that PPARα might be a key molecular target in MC-LR-induced steatosis and in toxic-SFA accumulation. The results obtained from molecular docking, molecular dynamics simulation, and NOD1-inhibitor experiments further revealed that MC-LR-derived SFAs, such as palmitic acid, could target the NOD1 protein to initiate hepatitis in zebrafish. The benchmark dose model identified palmitic acid as a sensitive indicator of MC-LR-induced NASH, and the point of departure value was estimated to be 1.634 μg/L. In conclusion, our findings offer new insights into the mechanism of MC-LR-induced NASH and aid in the prognosis and treatment of MC-LR-related liver metabolic diseases, as well as in assessing the health risks associated with cyanobacterial blooms.