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目的:探讨蜂蜡素降低胆固醇作用机制。方法:采用体外HepG2细胞培养,以放射性标记物~(14)C-乙酸、~3H_2O和~3H-甲羟戊酸研究蜂蜡素对胆固醇生物合成步骤的影响,以~(14)C-HMG-CoA研究蜂蜡素对HMG-CoA还原酶的影响,并用Folin-酚试剂测定细胞蛋白质的含量。结果:蜂蜡素呈剂量依赖性抑制~(14)C-乙酸、~3H_2O掺入细胞胆固醇生物合成,而对~3H-甲羟戊酸掺入合成无影响;在细胞微粒体提取物中加入蜂蜡素和~(14)C-HMG-CoA孵育,对甲羟戊酸生成无影响,但在培养的HepG2细胞中加入10%LPDS上调HMG-CoA还原酶水平,同时加入蜂蜡素和~(14)C-HMG-CoA孵育,可使甲羟戊酸生成减少。结论:蜂蜡素抑制胆固醇生物合成,是从乙酸消耗到甲羟戊酸生成之间某一酶催化水平上,与HMG-CoA还原酶有关。蜂蜡素对HMG-CoA还原酶无直接抑制作用,但可通过抑制HMG-CoA还原酶上调而抑制其活性,提示蜂蜡素降低血浆胆固醇的作用点可能在对该酶的合成或降解上。
Objective: To investigate the mechanism of lowering cholesterol by beeswax. METHODS: In vitro HepG2 cell culture was used to study the effect of beeswax on cholesterol biosynthetic steps using radioactive markers 14C-acetate, 3H2O, and 3H-mevalonate to ~(14)C-HMG- CoA studies the effect of beeswax on HMG-CoA reductase, and uses Folin-phenol reagents to determine cellular protein content. RESULTS: The beeswaxin inhibited the biosynthesis of 14C-acetate and -3H2O in cell cholesterol in a dose-dependent manner, but had no effect on the synthesis of 3H-mevalonate incorporation. The beeswax was added to the cell microsomal extracts. Incubation with ~(14)C-HMG-CoA had no effect on the production of mevalonate, but the addition of 10% LPDS in cultured HepG2 cells upregulated HMG-CoA reductase levels while adding beeswaxone and ~(14) Incubation of C-HMG-CoA can reduce mevalonate production. CONCLUSION: The inhibition of cholesterol biosynthesis by beeswax is an enzyme catalyzed between the consumption of acetic acid and the production of mevalonate, which is related to HMG-CoA reductase. The beeswaxin has no direct inhibitory effect on HMG-CoA reductase, but it can inhibit its activity by inhibiting the upregulation of HMG-CoA reductase, suggesting that the action point of beeswaxin to lower plasma cholesterol may be on the synthesis or degradation of the enzyme.