多囊性卵巢囊腫 (polycystic ovarian syndrome) 是一種常伴隨肥胖與雄性素過高 (hyperandrogenemia) 的疾病。而雄性素接受器 (androgen receptor) 已經在人類的脂肪前細胞 (preadipocyte) 與脂肪細胞(adipocyte) 被發現，顯示雄性素有可能直接作用在脂肪組織。體外脂肪生 成 (in vitro adipogenesis) 需要一連串的步驟，包括:增生中脂肪前細胞的生長停滯 (growth-arrest)，再進入細胞週期的細胞擴充 (mitotic clonal expansion)，以及末期分化 (terminal differentiation) 的生長停滯，並伴隨著特定基因表現的改變，當細胞擴充結束後，過氧小體增生活化接受體加碼 (peroxisome proliferator-activated receptor PPAR) 與CCAAT/促進子結合蛋白阿法 (CCAAT/enhancer binding protein C/EBP) 的表現會被引發，PPAR與C/EBP的表現會轉錄活化許多脂肪細胞基因，包括脂肪細胞特有的脂肪酸結合蛋白 (fatty acid binding protein, A-FABP/aP2)。現今已知多囊性卵巢囊腫病人的卵巢分泌過多的雄性素，其所分泌的雄性素主要是雄烯二酮 (androstenedione, ADTD) ，而腎上腺皮質會分泌脫氫表雄淄酮 (dehydroepiandrosterone, DHEA)，在多囊性卵巢囊腫病人的血液中DHEA的含量較高。在此研究中，我們使用3T3-L1細胞株探討ADTD與DHEA對脂肪前細胞分化的影響。將細胞培養到鋪滿整個培養皿，之後，用不同的分化培養液 (differentiation medium) 誘導細胞分化，並利用Oil Red O染細胞質液中油滴的特性以確定脂肪細胞的分化，在分化的第0，1，2，3，4，6天，以細胞計數方式評估細胞擴充，實驗結果發現，在正常情況下細胞數目至分化第3天會增加為第0天的兩倍，而ADTD (1 M) 與DHEA (1 M) 會抑制細胞增生。ADTD與DHEA降低細胞內三酸甘油脂 (triglyceride) 的堆積，且抑制aP2蛋白表現，ADTD 和DHEA抑制胰島素 (insulin) 誘導的葡萄糖攝入。ADTD和DHEA抑制脂肪前細胞分化的作用可被雄性素拮抗劑部分阻斷。ADTD與DHEA會抑制PPAR蛋白的表現，但不影響C/EBP蛋白的表現。這些結果顯示ADTD與DHEA透過阻斷細胞擴充與降低PPAR蛋白表現而抑制脂肪前細胞的分化。

Polycystic ovarian syndrome (PCOS) is a common disorder associated with obesity and hyperandrogenemia. Androgen receptors have been identified in human preadipocytes and adipocytes, suggesting that androgen can act directly on adipose tissue. In vitro adipogenesis requires a sequence of events, including growth arrest of proliferating preadipocytes, coordinated reentry into the cell cycle with limited clonal expansion, and growth arrest associated with terminal differentiation, accompanied by characteristic changes in gene expression. As clonal expansion ceases, expression of peroxisome proliferator-activated receptor (PPAR), CCAAT/enhancer binding protein  (C/EBP) are induced. Expression of PPAR and C/EBPis followed closely by the transcriptional activation of many adipocyte genes including the fatty acid binding protein (422/aP2). It is known that ovary is the main contributor to excess androgen production (mainly androstenedione; ADTD) in PCOS and that dehydroepiandrosterone (DHEA; the most abundant steroid in humans) is produced by the adrenal cortex and may be elevated in women with PCOS. In this study, we used 3T3-L1 cells to investigate the direct effect of ADTD and DHEA on adipocyte differentiation. Cells were cultured until conflunce and then were induced to differentiate by using variable differentiation media. Oil Red O staining was used to confirm adipocyte differentiation based on the presence of oil droplets in cytosol. Mitotic clonal expansion was assessed by cell counting at days 0, 1, 2, 3, 4 and 6 following treatment of the cells with ADTD (1 M) and DHEA (1 M) and resulted in a significant block in the normal doubling in cell number that occurs by day 3 of differentiation. Treating differentiating 3T3-L1 cells with ADTD and DHEA resulted in decreased intracellular triglyceride accumulation and protein levels of aP2. ADTD and DHEA also reduced insulin-stimulated glucose uptake. The inhibitory effects of ADTD and DHEA on adipogenic differentiation were partially prevented by androgen receptor antagonist, flutamide. ADTD and DHEA reduced protein levels of transcription factor, PPAR , but not C/EBP . These results suggest that ADTD and DHEA block adipocyte differentiation through disruption of mitotic expansion and down-regulation of PPAR protein expression.

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