口服細菌素 albusin B 促進脂肪酸氧化

Abstract

Albusin B 為Ruminococcus albus 7分泌之細菌素，分子量32 kDa，藉由Saccharomyces cerevisiae表現系統大量製備。先前的試驗指出，添加R. albus 7分泌之albusin B於肉雞飼料，有助於小腸營養分吸收，抑制腸道有害病原菌，進而促進肉雞生長效能。故第一部分研究目的為探討由R. albus 7分泌的細菌素對動物脂肪代謝的影響。本部分研究以六週齡BALB/c公鼠為實驗模式，飼料及飲水不限，隨機分成3組：控制組、酵母菌 （0.125 μg /g體重）、酵母菌加albusin B （0.125μg /g 體重），連續灌食14天後犧牲，觀察其生理表現及血液的脂肪代謝。與控制組比較，灌食albusin B不影響小鼠採食量，但體重有下降的趨勢。該組別的小鼠血液中三酸甘油酯與游離脂肪酸下降，而血中總膽固醇、高密度脂蛋白上升（P <0.05）。在腸道型態上，相較於控制組與酵母菌組，餵飼albusin B之小鼠有較高的迴腸絨毛高度（P <0.05）。相較於控制組，餵飼albusin B小鼠之迴腸、肝臟與心臟皆有較高脂肪酸運輸蛋白與脂肪酸氧化酵素acyl-CoA oxidase（ACO）基因表現(P <0.05)；在肝臟中有較低之脂肪酸合成酵素acetyl-CoA carboxylase (ACC)之基因表現；在心臟與肝臟中有較低之脂肪酸合成酵素fatty acid synthase (FAS) 之基因表現 (P <0.05)。且在餵飼albusin B小鼠之迴腸與肝臟中有較低之三酸甘油酯合成酵素acyl transferase之基因表現 (P <0.05)。此外，餵飼albusin B之小鼠心臟與肝臟中ATP生成較高，並增加抗氧化能力。由上述結果可知albusin B可增加小鼠腸道脂肪酸吸收，促進肝臟與心臟之脂肪酸氧化，降低脂肪酸合成，因此可降低小鼠體重。 第二部分研究目的為探討albusin B之添加對心肌細胞（H9c2）和小腸細胞（Caco2）脂肪酸代謝與抵抗氧化壓力之保護效果。利用H2O2誘發氧化壓力。結果顯示albusin B可促進細胞存活率，且增加脂肪酸運送與ACO基因表現，並提高ATP產量 (P <0.05)。當細胞處於氧化壓力下，albusin B提升細胞存活率，且有較高ACO與抗氧化酵素glutathione transferase之基因表現，並促進ATP生成。由上述結果可知即使在氧化壓力下， albusin B可促進脂肪酸氧化，且增強抗氧化系統，並提高細胞存活率。 綜合試驗結果可知，健康的狀態下，albusin B可促進脂肪氧化，提高能量生成，且減少小鼠體重。在氧化壓力下，albusin B也可提升脂肪氧化，並促進抗氧化機制。綜觀上述，albusin B可增加脂肪代謝，但詳細機制還須進一步探討。

Albusin B (bacteriocin), a 32 kDa protein, is isolated from Ruminococcus albus 7 and mass-produced by the Saccharomyces cerevisiae expression system. In previous study, we found that broilers supplemented with albusin B had a better intestinal absorption of protein and carbohydrate, and thus caused greater growth performance. The first objective of this study was to elucidate the effect of albusin B on lipid metabolism of healthy mice. Twenty-four of BALB/c male mice at age of 6 weeks were randomly assigned into 3 groups: normal saline (control), yeast ( 0.125μg /g BW ) , yeast with albusin B ( albusin B, 0.125μg /g BW ) with daily oral administration for 14 days exhibited until sampling. Compared with the control, mice with albusin B treatment decreased body weight, lowered plasma triglyceride and free fatty acids, but increased plasms total cholesterol and high density lipoproteins (P <0.05). In the intestinal morphology, mice oral administrated with albusin B displayed higher villus lenght in the ileum than those of the other two groups (P <0.05). Mice with yeast alone or administrated with yeast + albusin B had a higher mRNA expression of fatty acid binding proteins and acyl-CoA oxidase（ACO） in the ileum, heart and liver than those of control mice (P <0.05). Compared with the control mice, yeast only and albusin B treatments caused a decreased mRNA expression of hepatic acetyl-CoA carboylase (ACC) and n fatty acid synthase (FAS) in the heart and liver (P <0.05). Moreover, albusin B administration also suppressed mRNA level of diacylglycerol acyltransferase, responsible for triglyceride synthesis in the ileum and liver (P <0.05). Mice albusin B treatment also exhibited better ATP production and antioxidant capability in the heart and liver of mice (P <0.05). To sum up, these results demonstrated that albusin B treatment increased the intestinal lipid absorption, while it enhanced lipid oxidation but decreased the lipid synthesis in liver and heart, and therefore may accoumt for the decresed BW of mice orally doesd with albusin B. The second objective of this study was to elucidate the role of albusin B on lipid metabolism of cardiomyocytes（H9c2） and intestinal cell（Caco2） under oxidative stress. Hydrogen peroxide was applied to induce oxidative stress. The results showed that H9c2 and Caco2 with albusin B treatment had higher cell viability, and increased uptake and oxidation of fatty acid and ATP production when compared to the control (P <0.05). Consistent results were also observed in both of cell lines under oxidative stress. The mRNA expressions of ACO and antioxidative enzymes were upregulated and ATP production was increased by albusin B. The beneficial effect thus may improve cell survival rate. Taken together, under healthy condition, albusin B treatment promotes the lipid oxidation and ATP production but reduces the lipid synthesis and therefore cause body weight loss in mice. Under oxidative stress, treatment of albusin B increases energy metabolism and improves antioxidative system, and therefore improves the cell viability. This study demonstrated beneficial effect of albusin B on lipid metabolism and body weight. More comprehensive studies, however, required to elucidate the mechanism.