Microalgae extracts reduce appetite in zebrafish larvae linked to long-chain fatty acids and 5′-methylthioadenosine

Appetite modulation is a promising strategy for obesity treatment. The presented research screened 103 microalgae extracts from three strains of microalgae ( Chlorella sp. , Chlorococcum sp. and Nannochloropsis oceanica ) for appetite reducing activity, using high pressure processing and moderate electric fields. Two different feeding assays with zebrafish larvae were applied using either fluorescent labeled liposomes or paramecia. Two extracts of Chlorococcum sp., reduced food uptake for >30 % in the liposomes assay, while three extracts of Chlorella sp. (grown under autotrophic and heterotrophic conditions) for >40 % in the paramecia assay. Real-time mRNA expression revealed that autotrophic grown Chlorella sp. increased the anorexigenic signaling of cartpt and pomc . Metabolite profiling with LCMS/MS was performed to get first insights into responsible compounds for appetite signaling. Chlorococcum presented a glycerolipid cluster with 9 highly correlated nodes and 6 putative identifications, while Chlorella sp. (heterotrophic) had 11 highly correlated nodes with 3 putative identifications as nucleotides and nucleosides. Following, unsaturated fatty acids (oleic acid (OA), linoleic acid (LA), palmitoleic acid (PA)), as members of the glycerolipid cluster, and adenosine (A) and 5-methylthioadenosine (5′-MTA), as member of the nucleosides, were commercially acquired and tested in both appetite assays in zebrafish. All unsaturated fatty acids reduced food intake in both assays, while 5′-MTA only in the liposomes assay. Overall, the extraction conditions of microalgae triggered promising appetite reduction activity in Chlorella and Chlorococcum , which could be linked to unsaturated fatty acids and 5′-MTA. • Microalgae extracts reduce zebrafish food intake by over 30–40 %. • Autotrophic Chlorella sp. upregulates appetite-suppressing genes. • Key metabolites (UFAs, 5′-MTA) linked to appetite reduction in zebrafish.