Obesity is a serious global problem that is considered a great pandemic. It was related to many non-communicable diseases, including type 2 diabetes mellitus (T2DM). Crab (Crustacea: Decapoda) is one of the healthiest sea foods all over the world, being very rich in unsaturated fatty acids, especially in the female gonads and hepatopancreas. Therefore, this study was designed to explore the anti-obesity effect for the soft tissue extract of the female Nile crab Potamonautes niloticus. The chemical constituents of methanol extract from crab´s meat and soft Dichloromethane were evaluated using Liquid Chromatography with tandem mass spectrometryand Nuclear Magnetic Resonance. Also, the effect of this extract on obesity induced in zebra fish adults was studied in vivo, using real time PCR (qPCR) quantification of different lipid-metabolizing enzymes´ genes. More specifically, these analyzed transcripts were for enzymes related to de novo lipogenesis [i.e., fatty acids synthase (FASN) and acetyl- CoA carboxylase alpha (accα)]; adipogenesis [i.e. diacylglycerol O-acyltransferase 2 (dgat2)]; and lipid catabolism through β-oxidation [i.e. acetyl-CoA oxidase 1 (acox1)]. Moreover, the body contents of free cholesterol (TC) and triglycerides (TG) were assessed. The results showed that the extract contains amino acids such as cyclo-(Ala-4-hydroxy-Pro, Ile-pro, isoleucyl-proline, cyclo-(Leu-Leu), cycloleucylleucine, valyl-Leucine, L-valyl-L-phenylalanine, cyclo(L-leucyl-L-phenylalanyl), cyclo-[Tyr-(4-hydroxy-Pro)], and leucyl-phenylalanine); long chain unsaturated fatty acids such as (9-octadecenoic acid, 13-keto-9Z,11E-octadecadienoic acid, (+/-)-11-Hydroxy-5Z,8Z,12E,14Z,17Z-Eicosapentaenoic acid, and (.+/-.)-17-hydroxy-4Z,7Z,10Z,13Z,15E,19Z-docosahexaenoic acid); long chain saturated fatty acids such as (3-Hydroxyoctadecanoic Acid and 1-stearoyl-2-hydroxy-sn-glycero-3-phosphocholine); sphingolipids; fatty amide; and Monoacylglycerol. Furthermore, injection of crab extract to adult zebrafish induced a significant decrease of TG levels and the expression of the gene of the primary enzymes’ genes related to fatty acids β-oxidation, i.e., acox1. Meanwhile, crab extract injection induced significant down-regulation in the key lipogenic enzymes´ genes, i.e. accα, fasn, and dgat2. Therefore, P. niloticus soft tissue extract showed promising ingredients and capabilities that could reduce obesity through interference with lipids´ synthesis and stimulation of lipids´ degradation. Further investigations are recommended to elucidate the mechanism of action of Nile crab bioactive ingredients on obesity and other related health problems, such as T2DM.
