| Summary: | 碩士 === 東海大學 === 畜產與生物科技學系 === 94 === This study aimed to investigate the effects of Saint John’s wort (SJW)-methanol extracts on adipogenesis using the 3T3-L1 preadipocyte culture system. The results of oil-Red O staining showed that cells treated with SJW extracts during differentiation had lower degrees of lipid contents than the control cells, with the flower extracts had more inhibitory effects than the stem or leaf extracts. Treatment with the SJW flower extracts during early stages (day 0 to 2) did not inhibit cell differentiation as indicated by the results of oil-Red O staining and GPDH activity assay of the cells on day 6, but the treatment did decrease the mitotic clonal expansion. Cells treated with the flower extracts at late stages led to low degrees of differentiation compared with the untreated cells. Additionally, the expressions of the adipocyte differentiation-related transcription factors, such as CCAAT/enhancer-binding protein β (C/EBPβ), and peroxisome proliferator-activated receptor γ (PPARγ) were inhibited in the SJW flower extract-treated cells. And these may contribute to the decreased levels of the adipocyte-specific genes, including adipocyte-fatty acid binding protein (A-FABP), leptin, perilipin, and hormonal sensitive lipase (HSL), that are known to be expressed in the late stages of adipocyte differentiation. Furthermore, the levels of protein kinase Cs (PKCs), which usually decline along the adipocyte differentiation process as observed in the control cells, were unaltered in the SJW-treated cells, indicating that SJW extracts hindered the activation and thereafter downregulation of PKCs during adipocyte differentiation. The mRNA levels of lipolysis-related genes, namely perilipin, HSL, and glycerol kinase, were increased in the SJW-treated cells, suggesting that SJW flower extract treatment also increased the lipolytic activities in mature adipocytes. Finally, the SJW extracts were able to inhibit preadipocyte proliferation as estimated by cell enumeration. Overall, the SJW-methanol extracts inhibit adipogenesis by affecting different facets of the process, including the inhibition of preadipocyte division and mitotic clonal expansion during early stages of differentiation, the modulation of adipocyte differentiation through differentiation-related genes, and the elevation of lipolysis activities.
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