Effect of New Fly Maggot Protein Feed on mRNA Expression of TOR Signaling Pathway-related Genes in Loaches (Misgurnus anguillicaudatus)

[Objectives] This study was conducted to explore the effects of new fly maggot protein feed on the mRNA expression of genes related to the TOR signaling pathway in loaches(Misgurnus anguillicaudatus). [Methods] Two kinds of test feed with equal nitrogen and energy were prepared by replacing 60% of the fish meal in the control group with the new fly maggot protein feed, i.e., Diet1(control group) and Diet2(60% fish meal replacement group). The feeding experiment was carried out in an indoor circulating water system, and the breeding period was 60 d. [Results] For the livers, the mRNA levels of TOR and 4EBP1 in the Diet2 group were significantly higher than those in the Diet1 group(P<0.05), while the expression of 4 EBP2 was lower than in the Diet1 group(P<0.05);and as to the muscles, the mRNA levels of TOR and 4EBP1 in the Diet2 group were significantly lower than those in the Diet1 group(P<0.05), while there was no significant change in the mRNA level of 4EBP2 between the two groups. [Conclusions] The replacement of fish meal by fly maggot cultures affected the mRNA expression of TOR, 4EBP1 and 4EBP2 in loach livers and muscles.

Regulation of the PI3K/AKT Pathway and Fuel Utilization During Primate Torpor in the Gray Mouse Lemur, Microcebus murinus

Gray mouse lemurs（Microcebus murinus） from Madagascar present an excellent model for studies of torpor regulation in a primate species. In the present study, we analyzed the response of the insulin signaling pathway as well as controls on carbohydrate sparing in six different tissues of torpid versus aroused gray mouse lemurs. We found that the relative level of phospho-insulin receptor substrate（IRS-1） was significantly increased in muscle, whereas the level of phospho-insulin receptor（IR） was decreased in white adipose tissue（WAT） of torpid animals, both suggesting an inhibition of insulin/insulin-like growth factor-1（IGF-1） signaling during torpor in these tissues. By contrast, the level of phospho-IR was increased in the liver. Interestingly, muscle,WAT, and liver occupy central roles in whole body homeostasis and each displays regulatory controls operating at the plasma membrane. Changes in other tissues included an increase in phosphoglycogen synthase kinase 3a（GSK3a） and decrease in phospho-ribosomal protein S6（RPS6） in the heart, and a decrease in phospho-mammalian target of rapamycin（m TOR） in the kidney. Pyruvate dehydrogenase（PDH） that gates carbohydrate entry into mitochondria is inhibited via phosphorylation by pyruvate dehydrogenase kinase（e.g., PDK4）. In the skeletal muscle, the protein expression of PDK4 and phosphorylated PDH at Ser 300 was increased, suggesting inhibition during torpor. In contrast, there were no changes in levels of PDH expression and phosphorylation in other tissues comparing torpid and aroused animals. Information gained from these studies highlight the molecular controls that help to regulate metabolic rate depression and balance energetics during primate torpor.