何首乌提取物对脂肪酸合酶的抑制作用

Inhibition to Fatty Acid Synthase with Extract of Tuber Fleeceflower Root

最新报道脂肪酸合酶 (FAS)是治疗肥胖症的潜在靶部位 ,但目前已知的FAS抑制剂还很少 .测定表明 ,中药何首乌提取物对FAS同时具有很强的快结合可逆抑制和慢结合不可逆抑制作用 .萃取的最佳溶剂为 4 0 %乙醇水溶液 .该提取物对FAS全反应的半抑制浓度为 0 .0 0 5mg ml(以萃取时中药重量计 ) ;不可逆抑制过程为两相 ,在 0 4 6mg ml浓度下在 0 5min内快相失活超过 5 0 % ,慢相在 32min时失活达 90 % .该提取物对FAS中的酮酰还原反应有强抑制 ,半抑制浓度为 0 0 18mg ml,对烯酰还原反应有弱抑制作用 .抑制动力学分析表明 ,何首乌提取物对FAS的抑制和底物NADPH之间呈非竞争性关系 ,和丙二酰辅酶A接近竞争性关系 ,而与乙酰辅酶A为反竞争性关系 .推测何首乌还含有作用于FAS中的丙二酰转酰酶的抑制剂 .用何首乌提取物口服饲喂大鼠 ,可明显减低大鼠摄食量和降低大鼠体重 ;实验结束时实验组大鼠肝脏FAS活性低于对照组 .以上结果表明 ,中药何首乌提取物对FAS有很强的抑制作用 ,其抑制能力明显强于已知抑制剂 ,其动力学表现也和已知抑制剂完全不同 ,预计为新的抑制剂 。

Fatty acid synthase (FAS) is reported as a potential new therapeutic target for obesity. However, there are limited known FAS inhibitors presently. It is shown that extract of Chinese medicine tuber fleeceflower root (TFR) inhibited FAS activity by both strong reversible fast binding and irreversible slow binding inhibitions. 40% ethanol was the optimal solvent for extraction. Half inhibition concentration( IC 50 ) of TFR to FAS overall reaction was 0.005 mg/ml calculated on the basis of TFR weight in the extraction. The time course of irreversible inhibition by TFR extract was biphasic. In the presence of 0.46 mg/ml of TFR the inhibition in fast phase led to over 50% activity loss which was completed within 30 s while the slow phase inactivation led to 90% activity loss within 32 min. TFR extract strongly inhibited ketoacyl reduction of FAS with 0.018 mg/ml of IC 50 , and weakly inhibited enoyl reduction. The assay of inhibition kinetics showed that the inhibition to FAS by extract of TFR was non competitive against substrate NADPH, nearly competitive against malonyl CoA and un competitive against acetyl CoA. It was speculated that an inhibitor in TFR reacted on malonyl thansacylase of FAS. Treatment of TFR extract by oral incubation reduced body weight and food intake of rats significantly. The FAS activity in livers of the tested group rats was lower than that of the control rats at the end of the animal test. These results showed that FAS inhibitor in TFR had a stronger inhibition ability than the known inhibitors. Its characteristics of inhibition kinetics were much different from the known inhibitors. It is expected to be a new effective FAS inhibitor, and may be of great value for the study of FAS mechanism and the control of obesity.