Dietary selenium promoted muscle growth (myofiber hypertrophy rather than hyperplasia) by reducing endoplasmic reticulum stress in juvenile grass carp (Ctenopharyngodon idella)

Abstract

Selenium is an indispensable trace element in animals. Previous findings have shown that selenium deficiency can lead to various muscle diseases. Muscle is the major edible portion of animals and the largest tissue in fish. Therefore, the aim of this experiment was to investigate how dietary selenium affects muscle growth in juvenile grass carp (Ctenopharyngodon idella). The 2520 healthy juvenile grass carp (9.76 ± 0.005 g) were randomly assigned to 7 test groups of 6 replicates each and fed graded selenomethionine (SeMet) (0.05, 0.20, 0.40, 0.61, 0.77, and 0.98 mg selenium/kg diet) and sodium selenite (SS) (0.79 mg selenium/kg diet) for 10 weeks. Results showed that optimal dietary selenium levels (0.40 mg/kg) increased growth performance, whole-body and muscle protein content, serum and muscle hormone levels, and selenium status in juvenile grass carp; optimal dietary selenium levels (0.40–0.61 mg/kg) increased the mean diameter of myofibers and the frequency of myofibers with diameter > 50 μm but decreased the frequency of myofibers with diameter < 20 μm, and promoted the expression of genes related to myoblast proliferation and differentiation; optimal dietary selenium levels (0.40–0.61 mg/kg) inhibited mRNA and protein levels of endoplasmic reticulum stress-related genes in juvenile grass carp muscle; optimal dietary selenium levels (0.40–0.61 mg/kg) increased muscle protein deposition in juvenile grass carp, which was associated with IGF-1/PI3K/AKT/TOR and IGF-1/PI3K/AKT/FoxO3a signaling pathways. In conclusion, selenium promoted muscle growth associated with myofiber hypertrophy in juvenile grass carp. And selenium-promoted myofiber hypertrophy was associated with inhibition of endoplasmic reticulum stress, promotion of myoblast proliferation and differentiation, and protein deposition. In addition, the dietary selenium requirement (SeMet as the selenium source) for juvenile grass carp (10–182 g) was 0.51 and 0.56 mg/kg, based on quadratic regression of percent weight gain (PWG) and muscle protein content, respectively.