Aqueous extract of Protaetia brevitarsis larvae increases mTOR-mediated growth rate in zebrafish larvae

Abstract

Objective: To evaluate the effects of an aqueous extract of Protaetia brevitarsis (AEPB) on the growth of zebrafish and preosteoblast MC3T3-E1 cells. Methods: The effects of AEPB on the linear growth and the expression of growth-related genes in zebrafish and MC3T3-E1 cells were assessed using various molecular techniques. Furthermore, the involvement of the mammalian target of rapamycin (mTOR) pathway in AEPB-induced growth was investigated by employing the mTOR inhibitor rapamycin. Results: AEPB administration led to a significant and dose-dependent increase in zebrafish larvae growth over time. Additionally, AEPB treatment upregulated the expression of growth hormone-1 (GH-1), insulin-like growth factor-1 (IGF-1), growth hormone receptor-1 (GHR-1), and cholecystokinin-a (CCKA) in zebrafish. Similarly, AEPB stimulated the expression and release of IGF-1 and accelerated mTOR expression in MC3T3-E1 cells. In addition, rapamycin hindered AEPB-induced linear growth in zebrafish larvae and suppressed the expression of growth-promoting genes by inhibiting mTOR activation. Conclusions: AEPB shows growth-promoting effects by upregulating growth-related genes and activating the mTOR signaling pathway. Further investigations are warranted to elucidate its mechanisms of action and explore its potential application in the development of growth-enhancing supplements for various purposes.