Dietary DHA affects muscle fiber development by activating AMPK/Sirt1 pathway in blunt snout bream (Megalobrama amblycephala)

Abstract

This study was conducted to evaluate the effect of DHA on muscle development mechanism of blunt snout bream by a feeding trial and a primary hepatocyte culture. Fish (average weight 26.40 ± 0.11 g) were randomly fed three diets: a deficient DHA diet (0% DHA, DD), a control diet (0.1% DHA, DC) and a high level of DHA diet (0.8% DHA, DH) for 8 weeks. Results were indicated that the weight gain rate (WGR) of fish feed with DC diets was significantly higher than the DD and DH diets (P < .05). The texture (hardness, gumminess and chewiness), fibers density, the proportion of small-sized fiber (< 20 μm) and sarcomere lengths in the white muscle were significantly increased in the DH group than DD and DC groups (P < .05). The gene expression of Myog and Mrf4 were significantly increased (P < .05), and the gene expression of MSTNa and MSTNb were significantly decreased in the fish fed DH diets than DD and DC diets (P < .05). These results suggested that DHA increased the flesh quality and promoted the white muscle hyperplasia and muscle fiber development. In addition, the gene expression of AMPKα2 and Sirt1 in the DC and DH group was significantly higher than the DD group (P < .05). The protein level of AMPK, phosphor-AMPK and AMPK/phosphor-AMPK were significantly increased in DC and DH group (P < .05). In vitro, the isolated primary hepatocytes from blunt snout bream were incubated with 0, 100 and 400 μM DHA for 24 h. The results showed that 400 μM DHA was significantly up-regulate the gene expression of AMPKα2 and Sirt1, and increased the protein level of AMPK, phosphor-AMPK, AMPK/phosphor-AMPK and Sirt1 (P < .05). In summary, DHA promoted the white muscle hyperplasia and muscle fiber development, which may be in association with the activation of AMPK/Sirt1 pathway.