脂質的積聚反映出前脂肪細胞分化為脂肪細胞，這過程受許多基因、賀
爾蒙(例如胰島素)以及營養因子(如維他命)所調節。本篇論文針對綠茶唲茶
素(曾被視為維他命P)對分化中脂肪細胞的影響及作用機制加以探討。我們
發現綠茶中的EGCG 在前脂肪細胞分化前期對於降低胰島素- MIX
(1-methyl-3-isobutylxanthine)-DEX (dexamethasone)誘發的前脂肪細胞
數目比其他結構相近的綠茶唲茶素如EGC、ECG、EC 效果明顯，且其抑制作
用具有劑量效應和時間效應。此外，EGCG 改變C/EBPβ、C/EBPα、PPARγ等能
有效刺激前脂肪細胞脂肪合成(adipogenesis)的分化相關轉錄因子之蛋白
表現，也減少細胞內和培養液中的三酸甘油酯總量。進一步研究發現，單獨
給予MIX 刺激造成PPARγ蛋白量顯著的增加，但此結果在綠茶唲茶素中受
EGCG 專一地以劑量相關作用抑制。H-89，一種蛋白激酶A(protein kinase A)
的抑制劑，並不能阻斷EGCG 抑制MIX 刺激的PPARγ表現，此結果支持EGCG
的作用並非經由蛋白激酶A 相關途徑(protein kinase A-associated
pathway)。由以上的結果，我們得到的結論為，EGCG 可能經由控制脂肪生成
相關的轉錄因子來調節前脂肪細胞的分化。

Lipid accumulation reflects the process of preadipocytes differentiating into adipocytes
and such process is regulated by genetic, hormonal (i.e., insulin) and nutritional cues (i.e.,
vitamins). In this study, we examined the effect of green tea catechins, having been
considered as vitamin P, on differentiation of 3T3-L1 preadipocytes and investigated how they
work. We found that green tea EGCG was more effective than structurally-related EC, EGC
or ECG to reduce insulin-dexamethasone-1-methyl-3-isobutylxanthine (IDM)-induced
increases in cell number of preadipocytes during their initial differentiation to adipocytes.
The EGCG effect varied with dose administration and with time course. However, EGCG
altered the protein amount of C/EBPβ, C/EBPα, or PPARγ transcriptional factors, which were
enabling to stimulate adipogenesis of preadipocytes, as well as reduced total triglyceride
accumulation in the cells and medium. Further study showed that treatment of preadipocytes
with MIX alone, but neither insulin nor dexamethasone, caused a significant increase in the
protein amount of PPARγ and such stimulation was decreased by EGCG in the manner of dose
dependency or catechin specificity. H-89, a selective protein kinase A inhibitor, could not
block the EGCG inhibition of MIX-stimulated PPARγ, suggesting that EGCG effect is
independent of protein kinase A-associated pathway. We conclude that green tea EGCG may
modulate differentiation of preadipocytes to adipocytes through altering
adipogenesis-controlling transcriptional factors.

第六章參考文獻
Ahmad, N., Adhami, V. M., Gupta, S., Cheng, P., and Mukhtar, H. (2002) Role of the
retinoblastoma (pRb)-E2F/DP pathway in cancer chemopreventive effects of green tea
polyphenol epigallocatechin-3-gallate. Arch. Biochem. Biophys. 398, 125-31.
Ahmad, N., Cheng, P., and Mukhtar, H. (2000) Cell cycle dysregulation by green tea
polyphenol epigallocatechin-3-gallate. Biochem. Biophys. Res. Commun. 275, 328-34.
Brun, R. P., Tontonoz, P., Forman, B. M., Eillis, R., Chen, J., Evans, R. M., and Spiegelman, B.
M. (1996) Differential activation of adipogenesis by multiple PPAR isoforms. Genes &
Dev. 10, 974-984
Cao, Z.(1991) Regulation expression of three C/EBP isoforms during adipose conversion of
3T3-L1 cells. Gene& Development 5, 1538-1552
Chijiwa, T., Mishima, A., Hagiwara, M., Sano, M., Hayashi, K., Inoue, T., Naito, K., Toshioka,
T., and Hidaka, H. (1990) Inhibition of forskolin-induced neurite outgrowth and protein
phosphorylation by a newly synthesized selective inhibitor of cyclic AMP-dependent
protein kinase, N-[2-(p-bromocinnamylamino)ethyl]-5-isoquinolinesulfonamide (H-89), of
PC12D pheochromocytoma cells. J. Biol. Chem. 265, 5267-5272
Chung, L. Y., Cheung, T. C., Kong, S. K., Fung, K. P., Choy, Y. M., Chan, Z. Y., and Kwok, T.
T. (2001) Induction of apoptosis by green tea catechins in human prostate cancer DU145
cells. Life Sci. 681, 207-14.
Elberg, G.., Gimble, J. M., and Tsai, S. Y. (2000) Modulation of the murine peroxisome
proliferator-activated receptor γ2 promoter activity by CCAAT/enhancer-binding proteins. J.
Biol. Chem. 275, 27815-27822
Gupta, S., Ahmad, N., Nieminen, A. L., and Mukhtar, H. (2000) Growth inhibition, cell-cycle
dysregulation, and induction of apoptosis by green tea constituent
(-)-epigallocatechin-3-gallate in androgen-sensitive and androgen-insensitive human
prostate carcinoma cells. Toxicol. Appl. Pharmacol. 16482-90.
Hamm, J. K., Park, B. H., Farmer, S. R. (2001) A role for C/EBPβ in regulating peroxisome
proliferator-activated receptor γ activity during adipogenesis in 3T3-L1 preadipocytes. J.
Biol. Chem. 276, 18464-18471
Han, J., Hajjar, D. P., Zhou, X., Gotto, A. M., Jr., and Nicholson, A. C.(2002) Regulation of
peroxisome proliferator-activated recceptor-γ-mediated gene expression. J. Biol. Chem. 277,
23582-23586
Harmon, A. W., and Harp, J. B. (2001) Differential effects of flavonoids on 3T3-L1
adipogenesis and lipolysis.Am. J. Physiol. Cell Physiol. 280, C807-13.
Jung, Y. D., Kim, M. S., Shin, B. A., Chay, K. O., Ahn, B. W., Liu, W., Bucana, C. D., Gallick,
G. E., and Ellis, L. M. (2001) EGCG, a major component of green tea, inhibits tumour
growth by inhibiting VEGF induction in human colon carcinoma cells. Br. J. Cancer 84,
844-50.
Kao, Y. H., Hiipakka, R. A., and Liao, S. (2000) Modulation of endocrine systems and food
intake by green tea epigallocatechin gallate. Endocrinology 141, 980-7.
Kavanagh, K. T., Hafer, L. J., Kim, D. W., Mann, K. K., Sherr, D. H., Rogers, A. E., and
Sonenshein, G. E. (2001) Green tea extracts decrease carcinogen-induced mammary tumor
burden in rats and rate of breast cancer cell proliferation in culture. J. Cell Biochem. 82,
387-98.
Lea, C. Y. R., Monroe, D., and McIntosh, M. K. (1999). Dehydroepiandrosterone and related
steroids alter 3T3-L1 preadipocyte proliferation and differentiation, Comp Biochem
Physiol C Pharmacol Toxicol Endocrinol 123 17-25.
Liang, Y. C., Lin Shiau, S. Y., Chen, C. F., and Lin, J. K. (1999) Inhibition of cyclin-dependent
kinases 2 and 4 activities as well as induction of Cdk inhibitors p21 and p27 during growth
arrest of human breast carcinoma cells by (-)-epigallocatechin-3-gallate, J. Cell Biochem.
75, 1-12.
Liberto, M., and Cobrinik, D. (2000) Growth factor-dependent induction of p21(CIP1) by the
green tea polyphenol, epigallocatechin gallate. Cancer Lett. 154, 151-61.
Lung, H. L., Ip, W. K., Wong, C. K., Mak, N. K., Chen, Z. Y., and Leung, K. N. (2002)
Anti-proliferative and differentiation –inducing activities of the green tea catechin
epigallocatechin-3-gallate (EGCG ) on the human eosinophilic leukemia EoL-1 cell line.
Life Sci. 72, 257-268
Mary, E.W. L., Wang, X. L., Law, B. K., Hall, R. K., Nawano, M. and Granner, D. K. (2002)
Epigallocatechin gallate, a constituent of green tea, represses hepatic glucose production. J
Biol. Chem. 277, 34933-34940
Morrison, R. F., and Farmer, S. R. (1999) Role of PPARgamma in regulating a cascade
expression of cyclin-dependent kinase inhibitors, p18(INK4c) and p21(Waf1/Cip1), during
adipogenesis. J. Biol. Chem. 274, 17088-97.
Opare Kennedy, D., Kojima, A., Hasuma, T., Yano, Y., Otani, S., and Matsui Yuasa, I. (2001)
Growth inhibitory effect of green tea extract and (-)-epigallocatechin in Ehrlich ascites
tumor cells involves a cellular thiol-dependent activation of mitogenic-activated protein
kinases. Chem. Biol. Interact. 134, 113-33.
Pahan, K., Khan, M., and Singh, I. (1998) Therapy for X-adrenoleukodystrophy：normalization
of very long chain fatty acids and inhibition of induction of cytokines by cAMP. J. Lipid
Res. 39, 1091-1100
Paschka, A. G., Butler, R., and Young, C. Y. (1998) Induction of apoptosis in prostate cancer
cell lines by the green tea component, (-)-epigallocatechin-3-gallate. Cancer Lett. 130, 1-7
Reichert, M., and Eick, D. (1999) Analysis of cell cycle arrest in adipocyte differentiation,
Oncogene 18, 459-66.
Saeki, K., Hayakawa, S., Isemura, M., and Miyase, T. (2000) Importance of a pyrogallol-type
structure in catechin compounds for apoptosis-inducing activity, Phytochemistry 53 391-4.
Singh, A. K., Seth, P., Anthony, P., Husain, M. M., Madhavan, S., Mukhtar, H., and
Maheshwari, R. K. (2002) Arch. Biochem. Biophys. 401, 29-37
Spiegelman, B. M. (1998) PPARγ：adipogenic regulator and thiazolidinedione receptor.
Diabetes 47, 507-514
Tamura, T., Nakatani, K., and Yau, K. W. (1991) Calcium feedback and sensitivity regulation in
primate rods. J. Gen. Physiol. 98, 95-130
Tan, X., Hu, D., Li, S., Han, Y., Zhang, Y., and Zhou, D. (2000) Differences of four catechins
in cell cycle arrest and induction of apoptosis in LoVo cells. Cancer Lett. 158,1-6.
Watanabe, J., and Niki, R. (1998) Isolation and identification of acetyl-coA carboxylase
inhibitors from green tea, Biosci. Biophys. Biochem. 62, 532-534.
Xiong, W.(2001) Regulation of CCAAT/enhancer-binding protein-β isoform by synthesis by
alternative translational initiation at multipule AUG start site. Nucleic Acid Reasearch 29,
3087-3098
Yang, G. Y., Liao, J., Kim, K., Yurkow, E. J., and Yang, C. S. (1998b) Inhibition of growth and
induction of apoptosis in human cancer cell lines by tea polyphenols. Carcinogenesis 19
Yu, S., Matsusue, K., Kashireddy, P., Cao, W. Q., Yeldandi, V., Yeldandi, A. V., Rao, M. S.,
Gonzalez, F. J., and Reddy, J. K. (2002) Adipocyte-specific gene expression and adipogenic
Steatosis in the mouse liver due to peroxisome proliferator-activated receptor γ1 (PPARγ1)
overexpression. J. Biol. Chem. 278, 498-505