Effects of rosmarinic acid on the fibrotic toxicity of amylin in a zebrafish model

Amylin aggregation and the resulting fibrotic toxicity are associated with the pathogenesis of type 2 diabetes mellitus (T2DM). This study evaluated the protective effects of rosmarinic acid (RA) against amylin-induced toxicity in a zebrafish model. Healthy zebrafish embryos from cell stages 1-8 were microinjected with a mixture of 50 μM amylin and 20 μM thioflavin-T (ThT) to induce amylin aggregation and fluorescently label fibril deposition. Subsequently, the embryos were exposed to different concentrations of RA to investigate its impact on amylin toxicity. Morphological assessments at 48 and 120 h post-fertilization (hpf) revealed that neither amylin injection nor RA exposure caused significant deformity or circulatory failure. Fluorescence imaging at 72 and 96 hpf showed strong ThT fluorescence in amylin-injected embryos, indicating the presence of amylin fibril deposition. Exposure to 60 and 300 μM RA significantly reduced fluorescence intensity, suggesting its inhibitory effect on amylin aggregation. Behavioral analysis at 120 hpf demonstrated that amylin injection significantly increased the swimming distance of zebrafish larvae, potentially reflecting anxiety-like behaviors induced by oxidative stress. RA exposure mitigated these behavioral changes, restoring swimming activity to normal levels. This study revealed the in vivo inhibitory effects of RA on amylin-induced fibrillation and toxicity in the zebrafish model, providing insights into its potential application in combating amylin fibrillation.