Natural-based solutions to mitigate dietary microplastics side effects in fish

Dietary microplastics (MPs) can be consumed by fish, crossing through the gastrointestinal tract. MPs smaller than 20 μm can easily translocate to other organs, such as liver, commonly triggering oxidative stress in fish. Given the current unlikelihood of their short-term elimination, strategies to mitigate MPs-related issues on fish are of considerable interest to the scientific community. In the present study, to reduce both the dietary MPs-induced oxidative stress and the accumulation of MPs, the effectiveness of microencapsulated astaxanthin (ASX) was evaluated in zebrafish (Danio rerio). Specifically, zebrafish were reared from larvae to adults (6 months) and fed diets containing MPs different in range-size (polymer A: 1-5 μm; polymer B: 40-47 μm) at different concentrations (50 or 500 mg/kg). After this period, fish from each experimental group were divided in two sub-groups that were fed, for an additional month, with the previous diets or with the same diets containing implemented with microencapsulated ASX (7 g/kg), respectively. Results showed that microencapsulated ASX was able to counteract the negative effects caused by MPs different in size. Particularly, in zebrafish fed diets containing polymer B microbeads, microencapsulated astaxanthin was able to restore the intestinal epithelium, affected by the abrasive role of MPs during gut transit. Differently, in zebrafish fed diets containing polymer A microbeads, absorbed at intestinal level and translocated mainly to the liver, the microencapsulated ASX decreased the oxidative stress response and reduced the MPs accumulation in target organs due to the antioxidant and the coagulant properties of the ASX and microcapsules wall, respectively. Taken together, the results highlighted that the aquafeeds' implementation with microencapsulated astaxanthin is a prospective tool to prevent MPs-related issues in fish.