| 摘要註: |
鰻魚在生長過程中體脂肪會逐漸累積，已有證據指出當體脂肪累積到一定比率可能是促使鰻魚降海繁殖的因素。鰻魚攝取的能量經肝臟代謝後可轉換為脂肪儲存在肌肉之間的脂肪細胞，儲存的脂肪可再經肝臟代謝再運送至其他組織進行利用。已知PPAR在脂肪代謝扮演重要角色，本研究希望藉由分析鰻魚生長及人工催熟過程中，PPAR、PTEN、RXR和脂肪代謝相關基因在肝臟和肌肉組織中基因表現量之變化，藉以了解脂肪代謝與鰻魚生長或卵巢發育的關係。首先挑選6~193公克鰻魚進行調查，結果顯示肝臟中隨體重增加PPARγ、RXR short、PTEN short、aldolase b 、NNT和fatty acid elongase的基因表現有上升的趨勢；而在肌肉組織中PPARγ、RXR short、PTEN long、aldolase b的基因表現有上升的趨勢，H-FABP和PPARα的基因表現則有下降趨勢，推測體型較小的鰻魚，肝臟和肌肉組織傾向脂肪合成，將能量儲存在肌肉組織中。接著挑選100~800公克鰻魚進行重複實驗，結果顯示雌鰻肝臟中PPARγ、RXR long、EDF-1和NNT的基因表現會隨著體重增加而呈現下降趨勢且趨於平緩，aldolase b和H-FABP的基因表現則呈上升的趨勢；而在肌肉組織中隨著體重和肌肉脂肪含量增加，PPARγ、RXR long、EDF-1、PTEN short、PTEN long 、aldolase b、NNT、H-FABP和pyruvate carboxylase之基因表現均呈現下降趨勢。在雄鰻則發現隨著體重增加，肝臟內 PPARγ和RXR long和aldolase b表現量有上升的趨勢；肌肉組織中的基因表現則和雌鰻類似。若以卵巢發育的角度來看，隨著GSI上升雌鰻肝臟中PPARγ和EDF-1的基因表現呈下降趨勢，aldolase b和pyruvate carboxylase的基因表現則呈現上升趨勢，而在肌肉組織中PPARγ、RXR long、PTEN short、PTEN long 、aldolase b、NNT、H-FABP和pyruvate carboxylase的基因表現隨GSI增加反而呈現下降趨勢，因此推測體型較大的鰻魚，脂肪累積達到一定比率後，肝臟和肌肉組織的脂肪合成會減緩，而肝臟中pyruvate carboxylase和卵巢發育有關。在飢餓的鰻魚發現，隨著體重減少(%)越多，肝臟中PPARγ、RXR long和NNT的表現呈下降的趨勢，PPARβ、PPARα、肌酸激?creatine kinase、RXR short 和ACC2的表現則有上升的趨勢；而在肌肉組織中，隨著體重減少(%)越多，PPARγ、EDF-1、aldolase b、NNT、PTEN long、PTEN short、lipoprotein lipase 和ACC2 的基因表現呈下降的趨勢，PPARβ和RXR long則呈上升的趨勢，顯示飢餓的鰻魚會減少脂肪合成並增加脂肪酸氧化產生能量。接著觀察人工催熟對脂肪代謝相關基因表現量之影響，施打腦下垂體萃取物加睪固酮的雌鰻，其肌肉組織內EDF-1和H-FABP的表現量相較於只施打腦下垂體萃取物的雌鰻有明顯下降，而ACC 2的表現量則有明顯上升。以鮭魚腦下垂體催熟雌鰻，結果顯示隨GSI增加肝臟內RXR long、RXR short和H-FABP 的基因表現量有上升的趨；而在肌肉組織中ACC 2、H-FABP、EDF-1和6PDGH 的基因表現量隨GSI增加有上升趨勢。總合以上結果：推測體重較重以及脂肪含量較高的鰻魚，其肝臟和肌肉內的脂肪合成會減緩；隨著卵巢發育越好，肝臟中pyruvate carboxylase、RXR long、RXR short和H-FABP的表現量有上升的趨勢；肌肉組織中ACC 2、H-FABP、EDF-1和6PDGH的表現量有上升趨勢，顯示肝臟中pyruvate carboxylase、RXR long、RXR short和H-FABP以及肌肉中的ACC 2、H-FABP、EDF-1和6PDGH和卵巢發育具較強之相關性，推測在成體繁殖發育過程肝臟和肌肉組織能提供脂肪供卵巢發育利用。 Evidences have showed that the body fat content is a trigger factor to the eel catadromous reproduction migration. Adipocytes deposit energy located among the muscle fibers, energy derived from lipids is transferred among the liver, muscle, and other organs in the eel. PPARs play an important role in lipid metabolism. By investigate expression profiles of PPARs and other lipid metabolism-related genes in the muscle and liver, we try to know the relationship between lipid metabolism, growth and reproduction. First we investigated expression profiles of metabolism-related genes in the muscle and liver of eels with body weight of 6 to 193 gram. The results indicated that hepatic expressions of PPARγ, RXR short, PTEN short, aldolase b, NNT and fatty acid elongase increased with the increase of body size; in the muscle, the expressions of PPARγ, RXR short, PTEN long, aldolase b increased with the increase of body size. Then we investigated expression profiles of lipid metabolism-related genes in the muscle and liver of eels with body weight of 100 to 800 gram. The results indicated that hepatic expressions of PPARγ, RXR long, EDF-1 and NNT decreased but aldolase b and H-FABP increased with the increase of body size and muscle fat content in the female eels; in the muscle, the expressions of all tested genes (PPARγ, RXR, EDF-1, PTEN, aldolase b, NNT, H-FABP, and pyruvate carboxylase) decreased with the increase of body size and muscle fat content in the female eels. The expressions of all tested genes (PPARγ, RXR, EDF-1, PTEN, aldolase b, NNT, H-FABP, and pyruvate carboxylase) of male eels were similar to female eels, but hepatic expressions of PPARγ and RXR long inversely related to the increase of body size increased and muscle fat content in male eels. In addition, with the augment of GSI in the female eels, the hepatic expressions of aldolase b and pyruvate carboxylase increased but PPARγ and EDF-1 decreased; the muscular expressions of PPARγ, RXR long, PTEN short, PTEN long, aldolase b, NNT, H-FABP and pyruvate carboxylase decreased. We also investigated expression profiles of lipid metabolism-related genes in the muscle and liver of fasting eels. The results indicated that hepatic expressions of PPARγ, RXR long and NNT decreased but PPARβ, PPARα, creatine kinase, RXR short and ACC2 increased during the weght loss; in the muscle, PPARγ, EDF-1, aldolase b, NNT, PTEN long, PTEN short, lipoprotein lipase and ACC2 decreased but PPARβ and RXR long increased with the reducing of body weght. The results suggested that reducing lipogenesis and increasing fatty acid oxidation was utilized for energy production in fasting eels. The effects of pituitary extracts on the gene expressions were also followed. GSI was increased by the treatment. The supplement of testosterone reduced muscular expressions of EDF-1 and H-FABP; if compared with the pituitary extracts alone, the expression of ACC b2 was significantly stimulated by the supplement. In addition, with treatment of salmon pituitary homogenates (SPH), the hepatic expressions of pyruvate carboxylase, RXR long, RXR short and H-FABP increased with the augment of GSI in the female eels; in the muscle, the expressions of ACC 2, H-FABP, EDF-1 and 6PDGH increased with the augment of GSI in the female eels. From the results, it is speculated that the lipid synthesis in the liver or muscle decreased in the female eels with a bigger body size or a higher body fat content. Pyruvate carboxylase, RXR long, RXR short and H-FABP in liver and ACC 2, H-FABP, EDF-1 and 6PDGH in muscle were related to development of ovary. |