Establishing a screening platform targeting activation of insulin-like growth factor I for herbal extracts from Chinese medicine

Abstract

Aquaculture production generated US$ 265 billion dollars in 2020, which is one of the fastest growing industries in the 21^st century. However, environmental concerns have triggered policies requiring a massive reduction in fish farm size. The reduction in pen size has given rise to high density of fish cultures. Due to cramped conditions, fish in pen cultures are more prone to disease and stress. Therefore, the amount of time spent in high density pen cultures should be reduced as much as possible. The use of traditional Chinese medicine (TCM) in fish feed has been proposed as an environmentally friendly, non-toxic and affordable solution. To find the growth-promoting TCM, this study established a luciferase screening platform for TMC using the activation of the the insulin-growth-factor I (IGFI) promoter of Mozambique (Oreochromis mossambicus) as the readout. An increase in IGFI directly induces body growth in fish. The promoter sequence of Mozambique tilapia IGFI was inserted into a plasmid, then which was transfected into cultured HEK293T human kidney fibroblasts cells. Three hundred and eighteen herbal extracts, including thirteen extracts from non-medicinal parts, were screened. Twenty-nine herbal extracts significantly increased the promoter-driven luciferase activity. Amongst them, the extracts of Ziziphus jujuba semen, Salviae plebeia herba and Glycyrrhiza uralensis radix were showing the best inductive results, and the herbal extracts were characterized further. The extracts showed consistent dose-response in both HEK293T cells and C2C12 cells in inducing the luciferase activity. The 75% ethanol extract of Z. jujuba semen could activate luciferase activity by over 3-fold at 40 µg/mL. The 50% ethanol extract of S. plebeia herba has the highest activation of luciferase, capable of a 4-fold increase in activity. All three herbs are showing low toxicity in human, and which are commonly used in TCM formulae. Moreover, the HPLC profiles correlated chemical concentration with activation of the promoter of tilapia IGFI in cultured cells. Higher concentrations of these chemicals in the 50% ethanol extract of G. uralensis radix and S. plebeia herba may be the cause of higher activation of luciferase activity. These results suggest that the ethanol extracts could be ideal candidates for the promotion of fish growth, alleviating the pressure on fish farmers.

Date of Award	2023
Original language	English
Awarding Institution	The Hong Kong University of Science and Technology
Supervisor	Karl Wah Keung TSIM (Supervisor)