| Summary: | 碩士 === 國立臺灣大學 === 生化科技學系 === 104 === The prevalence of obesity in developed and developing countries has been increasing over the past decades, presumably due to excessive energy intake and less energy consumption.
The main strategy of obesity prevention is to decrease energy intake and to increase consumption. Recent studies indicate that “browning” of white adipose tissue (WAT) can dissipate energy as heat and thus can decrease fat accumulation and ameliorate the obesity condition, which results in weight loss. Previous studies showed that mice fed bitter gourd powder had lower body weight and adipose mass and higher mRNA expression of Pgc1α, Ucp1 and Nrf1 in WAT, Pgc1α and Nrf1 or Tfam in skeletal muscle and brown adipose tissue, suggesting the browning of WAT. In 3T3-L1 cell model, ethyl acetate extract (EAE) of BGP but not water extract (WE) has been shown to trigger Ucp1 mRNA expression. We hypothesize that eglucosylated triterpenoids of BGP can trigger browning. In this study, polar fraction of BGP was treated with HCl (acid hydrolysis) and was extracted with n-hexane and was used to treat 3T3-L1 preadipocytes during or after differentiation: phase 1: during differentiation, phase 2: 4 days before maturation, treatment for 4 days, phase 3: after maturation. The samples included BG extract with acid-hydrolysis (Hex), BG extract without
acid-hydrolysis
(Hex(un)), ursolic acid (UA), oleanolic acid (OA) and 9c, 11t, 13t-CLN. The results indicated that 0.2 μg/mL Hex was able to increase Pgc1α, Cidea, and Nrf1 mRNA expressions at phase 2, and at phase 3, 0.2 μg/mL Hex could increase Pgc1α, Ucp1 and Cidea mRNA expressions. At phase 2, Ucp1 mRNA expression
could be increased at 0.2 μg/mL and 5 μg/mL Hex(un); however, Tfam mRNA expression could only be increased at 0.2 μg/mL Hex(un). At phase 3, Pgc1α and Ucp1 mRNA expressions could only be increased at 1 μg/mL Hex(un). OA increased Ucp1, Cidea and Tfam mRNA expressions at phase 2. UA increased only Ucp1 mRNA expression at phase 3. CLN had no effect on Ucp1 mRNA expression at three phases and at three concentrations.
We also tried to use XFe24 Flux analyzer to measure oxygen consumption rate (OCR) of 3T3-L1 adipocytes after browning. The data showed that when we induced differentiation in XF24 microplates, we could always have low readings of dissolved oxygen, which may be the reason why we couldn’t measure correct OCR of cells.In conclusion, in this cell model, acid-hydrolyzed or unhydrolyzed extract of bitter gourd had different browning activities. Both UA and OA, oleanane-type, could increase some brown-related gene expressions. Hence, triterpenoids presumably can promote browning.
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