Effect of dietary supplementation with the cyanobacterium Synechococcus elongatus PCC 7942 on the brain transcriptome of zebrafish (Danio rerio).

The application of cyanobacteria as sustainable feed additives in aquaculture has gained increasing attention due to their nutritional and functional properties. In previous studies, we demonstrated that dietary supplementation with Synechococcus elongatus PCC 7942 improved hepatic homeostasis and modulated the intestinal microbiota of zebrafish (Danio rerio), without adverse effects on intestinal morphology. Building upon these findings, the present study aimed to expand our understanding of the transcriptomic responses in the zebrafish brain to dietary supplementation with S. elongatus. The cyanobacterial biomass presented a proximate composition of 45.19% protein, 21.34% lipids, 10.08% carbohydrates, and 8.01% ash, along with a fatty acid profile rich in palmitic acid (39.96%) and linoleic acid (12.25%). After 35 days of feeding, fish receiving the supplemented diet showed higher daily feed intake and condition factor, while other growth parameters did not differ significantly from the control group. Transcriptomic analysis of the brain revealed differential expression of 15 genes grouped into five functional categories: energy metabolism, calcium homeostasis, neuroplasticity, oxidative stress response, and metabolic regulation. Overexpression of genes such as ldhbb, gapdh, and tsc1a suggests that S. elongatus modulates brain metabolism through enhanced glycolysis and activation of protective cellular pathways. The findings indicate that S. elongatus PCC 7942 exerts neuroprotective and metabolic effects, supporting its potential as a novel dietary supplement in aquaculture.