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The Effects of Several Phtoestrogens on Metabolic Syndrome
fatty acid metabolism
human hepatocellular carcinoma cell (HepG2 cell)
|Abstract:|| 代謝症候群指具有腹部肥胖 (central obesity)、高血壓、高血糖、高血三酸甘油酯 (TG)、高密度脂蛋白膽固醇 (HDL-C) 過低並常伴隨脂肪肝等症狀，最終可能引發心血管疾病，而雌激素對於心血管疾病及代謝症侯群相關病灶具保護效應，但若使用雌激素治療可能會增加乳癌風險。本研究分別以動物及細胞實驗模式，探討具植物性雌激素之食材對於代謝症候群病灶之影響。
實驗一、6週齡apoE剔除小鼠予以卵巢切除後分為2組，OVX組(n = 8) 給予高脂 (20% fat) 飼料、OVX+SE組(n = 8) 給予高脂飼料加0.5% sesamin，餵養11週後犧牲。結果顯示OVX+SE組第4及11週血液TC顯著高於OVX組34% ( p<0.05)；血液TG、HDL-C及adiponectin兩組無顯著差異；OVX組主動脈弓與胸主動脈脂質堆積面積百分比高於OVX+SE組，達邊際顯著差異(p = 0.07)。
實驗二、6週齡C57BL/6J小鼠分為4組，其中sham組施予假手術，其他三組予以卵巢切除，Sham(n = 5)及OVX組(n =11) 給予高脂 (20% fat) 飼料、OVX+ SE組(n=12)給予高脂飼料加0.5% sesamin、OVX+IS組(n=12) 給予高脂飼料加0.5% isoflavone，共餵養14週後犧牲。結果得知OVX+SE組及OVX+IS組第9週血液TC顯著高於OVX組，但到了實驗第14週，各組間無顯著差異。OVX+SE組血液HDL-C顯著高於OVX組27% ( p<0.05)，無顯著影響肝臟TC及TG含量；OVX+IS組血糖、肝臟TG含量皆顯著低於OVX組( p<0.05)，血液adiponectin顯著低於OVX組55% ( p<0.05)；血液TG、insulin、NEFA、HOMA-IR各組間無顯著差異。
實驗三、以50 nM T0901317或5 μl/ml intralipid兩種方式提高HepG2的TG含量，模擬脂肪肝的生成，並同時分別投予不同劑量之具植物性雌激素活性之食材：sesamin、genistein、enterolactone、苜蓿芽乙酸乙酯萃取物及山藥乙酸乙酯萃取物，共同培養48小時，之後分析細胞內TG含量以及脂肪酸生合成及氧化酵素之mRNA和蛋白質的表現量。結果發現，在LXR agonist模式中，sesamin、enterolactone 及genistein皆能顯著降低肝細胞內TG的含量，而山藥及苜蓿芽乙酸乙酯萃取物對肝細胞TG含量無顯著影響，Intralipid模式中，sesamin、enterolactone 及苜蓿乙酸乙酯萃物可顯著降低肝細胞內TG的含量；進一步發現sesamin、genistein、苜蓿乙酸乙酯萃物均能顯著下降FAS mRNA及蛋白質表現量，且轉錄因子sterol regulatory element binding proteins-1 (SREBP-1) mRNA的表現量也明顯被抑制，sesamin及苜蓿芽乙酸乙酯萃物亦能顯著上升肝細胞脂肪酸氧化酵素acyl-CoA oxidase (ACO) mRNA表現量；所有萃物皆無顯著影響glycerol 3-phosphate acyltransferase (GPAT) mRNA表現量。
Metabolic syndrome includes central obesity, hypertention, hyperglycemia, hypertriglyceridemia, and low serum level of high density lipoprotein-cholesterol (HDL-C), and is usually associated with cardiovascular diseases and fatty liver. The prevalence of metabolic syndrome increases after menopause due to estrogen deficiency, but estrogen therapy increases the risk of breast cancer. This study was to investigate the effects of some phytoestrogens on atherosclerosis, metabolic syndrome, and fatty liver using ovariectomized (OVX) C57BL/6J mice, OVX apoE-/- mice and HepG2 cells, respectively. In experiment 1, 6-wk-old OVX apoE-/- mice were assigned to 2 groups, fed the high fat (20%, w/w) diet (OVX, n = 8) or the high fat diet supplemented with 0.5% sesamin (OVX+SE, n = 8). After 11 wk of feeding, the mice were sacrificed to collect blood and aorta. The results showed that OVX+SE group had a higher serum level of total cholesterol (TC) in wk 4 and 11 (p<0.05), a higher serum level of enterolactone (p<0.05), and a slightly lower percent of aortic lesion areas (p = 0.07) in wk 11. There were no significant differences in serum levels of TG, HDL-C, and adiponectin between the two groups. In experiment 2, 6-wk-old female C57BL/6J mice were randomly divided into 4 groups and fed different diets. Sham group (n = 5) and OVX group (n =11) were fed high fat diet; OVX+SE group (n = 12) was fed high fat diet supplemented with 0.5% sesamin; OVX+IS group(n = 12) was fed high fat diet supplemented with 0.5% isoflavones. After 14 wk of feeding, the mice were sacrificed to collect blood and liver. The OVX+SE and the OVX+IS groups had a higher serum levels of TC in wk 9 (p<0.05), but not in wk 14, as compared with the OVX. The OVX+SE group had a higher level of serum HDL-C than the OVX groups (27% increase, p<0.05). Levels of hepatic TC and TG were not significantly different between the OVX and OVX+SE groups. The OVX+IS group had a significantly lower levels of fasting serum glucose, adiponectin (55% reduction, p<0.05) and hepatic TG than the OVX group (p<0.05). There were no significant difference in serum levels of TG, insulin, non-esterified fatty acid, and HOMA-IR among OVX, OVX+SE and OVX+IS group. In experiment 3, HepG2 cell was treated with LXR agonist, 50 nM T090137, or 5 μl /ml intralipid to induce intracellular TG accumulation and co-treated with several phytoestrogens for 48 h. Cellular TG and protein contents were determined. mRNA and protein expression of lipogenic and fatty acid oxidation enzymes were evaluated by reverse transcriptase-PCR and Western immunoblot analyses, respectively. The results showed that sesamin, enterolactone or genistein significantly decreased intracellular TG (p<0.05) in LXR agonist model, but yam ethylacetate extracts (EAE) and alfalfa EAE did not. In intralipid model, sesamin, enterolactone or alfalfa EAE significantly decreased intracellular TG (p<0.05). Sesamin, genistein or alfalfa EAE significantly decreased mRNA and protein expression of fatty acid synthase (p<0.05), and significantly down-regulated mRNA expression of sterol regulatory element binding proteins-1 (p<0.05). Sesamin and genistein also decreased acetyl-CoA carboxylase mRNA expression (p<0.05). Besides, sesamin and alfalfa EAE up-regulated mRNA expression of acyl-CoA oxidase, a key enzyme of peroxisomal β-oxidation. But none of the phytoestrogens tested affected the mRNA expression of glycerol 3-phosphate acyltransferase. In conclusion, this study shows that sesamin increases serum HDL-C, potentially decreases aorta lesion, but can not improve central obesity or fatty liver; isoflavones can reduce central obesity and reduce the risk of fatty liver; alfalfa EAE may have thepotency to reduce the risk of fatty liver.
|Appears in Collections:||學位論文|
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