Abstract
Two experiments were conducted to investigate the in vitro effects of Eucommia ulmoides ( E. ulmoides ) and its active components on the growth, lipid metabolism and collagen metabolism of grass carp's ( Ctenopharyngodon idellus ) hepatocytes and intramuscular fibroblasts. In experiments 1 and 2 (Expt. 1, 2), hepatocytes and intramuscular fibroblasts were treated with 2.5, 5, 10, 20, 40 and 80 μg ml –1 of Eucommia bark extract (EBE), Eucommia leaf extract (ELE), pinoresinol diglucoside (PDG), chlorogenic acid (CGA), quercetin (QC) and aucubin (AU) for 24 h, respectively, then the cell growth, lipid and collagen metabolism‐related gene expressions were evaluated. The results showed that the cell proliferation rate of hepatocytes and intramuscular fibroblasts was significantly improved by the supplementation of EBE, ELE, CGA, QC and AU. Moreover, triglyceride concentration of hepatocytes was significantly decreased by the EBE, ELE, CGA and QC supplementations compared to the control. Meanwhile, EBE, ELE, CGA, QC and AU supplementations significantly upregulated the relative gene expressions of insulin‐like growth factor‐1 ( igf1 ), protein kinase B ( akt ), target of rapamycin ( tor ) and eukaryotic initiation factor 4E binding protein 1 ( 4ebp1 ) in hepatocytes, and ribosomal protein S6 kinase 1 ( s6k1 ) transcription was significantly activated by ELE, CGA and QC supplementations. Nonetheless, phosphatidylinositol 3‐kinase ( pi3k ) was unaffected by any of the supplements. In addition, the mRNA expressions of genes associated with lipid metabolism (peroxisome proliferator activated receptor α pparα , carnitine palmitoyltransferase 1 cpt1 , adipose triglyceride lipase atgl , hormone‐sensitive lipase hsl , peroxisome proliferator activated receptor γ pparγ ) were significantly upregulated by EBE, ELE, CGA and QC. In intramuscular fibroblasts, the EBE, ELE, CGA, QC and AU supplementations significantly increased in vitro hydroxyproline concentrations, promoted the relative expressions of transforming growth factor‐β1 ( tgfβ1 ), connective tissue growth factor ( ctgf ), collagen type I alpha 1/2 chain ( col1a1 , col1a2 ), lysine oxidase ( lox ) and tissue inhibitor of matrix metalloproteinase‐2 ( timp2 ), and decreased matrix metalloproteinase‐2 ( mmp2 ) gene expression. Also, the gene expressions of drosophila mothers against decapentaplegic protein 2/4 ( smad2 , smad4 ) and proline hydroxylase ( phd ) were significantly upregulated by ELE, CGA, QC and AU supplementations. Based on the present in vitro results of grass carp, EBE, ELE, CGA, QC and AU improved the growth and lipid metabolism (except AU) in hepatocytes, and promoted the collagen deposition in intramuscular fibroblast, which is partly attributed to the signalling pathways of AKT/TOR, PPARα and TGF‐β/Smads/CTGF.