Recognition of purified beta 1,3/1,6 glucan and molecular signalling in the intestine of Atlantic salmon

Atlantic salmon was orally intubated with a highly purified beta-glucan product (MacroGard (R)) to study the recognition of the molecule by the receptor genes, the regulation of the downstream signalling genes and global proteins, and the micromorphological changes in the intestine. The beta-glucan receptor genes of Atlantic salmon, sclra, sclrb, sclrc and cr3, seem to recognize the molecule, and initiate the downstream ITAM-motif signalling, as evident from the significantly high mRNA levels of ksyk, mapkin2, il1b and mip2a levels. Among the altered proteins, the Apoa4 (involved in carbohydrate and lipid metabolism); Tagln, Actb (uptake of beta-glucan); Psma2 (associated with substrate recognition); and Ckt (energy metabolism-related) were the overexpressed ones. The underexpressed proteins included the Uk114, Rpl9, Ctsb and Lgal that are connected to proliferation, LPS-stimulation, Rib and lactose recognition, respectively. Furthermore, the mRNA levels of igt and the number of immune cells in the distal intestine were found to increase upon beta-glucan uptake by the fish. This study provides some clues on the mechanisms by which the beta-glucan evokes response in Atlantic salmon, particularly at the intestinal level. (C) 2015 Elsevier Ltd. All rights reserved.