Qureshi A A, Pearce B C, Nor R M, Gapor A, Peterson D M, Elson C E
Advanced Medical Research, Madison, WI 53719, USA.
J Nutr. 1996 Feb;126(2):389-94. doi: 10.1093/jn/126.2.389.
The concentration-dependent impact of gamma-tocotrienol on serum cholesterol can be traced to the posttranscriptional down-regulation of 3-hydroxy-3-methylglutaryl coenzyme A reductase activity. gamma-Tocotrienol also suppresses tumor growth. Palmvitee, the tocopherol and tocotrienol-rich fraction of palm oil, is the sole commercial source of gamma-tocotrienol. Contrary to the universal findings of the efficacy of gamma-tocotrienol there are conflicting reports of the impact of Palmvitee on 3-hydroxy-3-methylglutaryl coenzyme A reductase activity, serum cholesterol concentrations and tumor development. These conflicting reports led us to examine the impact of alpha-tocopherol on the cholesterol-suppressive action of gamma-tocotrienol. Control and experimental diets were fed to groups of White Leghorn chickens (n = 10) for 26 d. The control diet was supplemented with 21 nmol alpha-tocopherol/g. All experimental diets provided 141 nmol of blended tocols/g diet. The alpha-tocopherol and gamma-tocotrienol concentrations of the experimental diets ranged from 21 to 141 and 0 to 120 nmol/g, respectively. We now report that including alpha-tocopherol in tocol blends containing adequate gamma-tocotrienol to suppress 3-hydroxy-3-methylglutaryl coenzyme A reductase activity results in an attenuation of the tocotrienol action (P < 0.001). A summary of results from studies utilizing different Palmvitee preparations shows that effective preparations consist of 15-20% alpha-tocopherol and approximately 60% gamma- (and delta-) tocotrienol, whereas less effective preparations consist of > or = 30% alpha-tocopherol and 45% gamma- (and delta-) tocotrienol.
γ-生育三烯酚对血清胆固醇的浓度依赖性影响可追溯到转录后对3-羟基-3-甲基戊二酰辅酶A还原酶活性的下调。γ-生育三烯酚还能抑制肿瘤生长。棕榈维生素E，即富含生育酚和生育三烯酚的棕榈油部分，是γ-生育三烯酚的唯一商业来源。与γ-生育三烯酚功效的普遍研究结果相反，关于棕榈维生素E对3-羟基-3-甲基戊二酰辅酶A还原酶活性、血清胆固醇浓度和肿瘤发展影响的报道存在相互矛盾之处。这些相互矛盾的报道促使我们研究α-生育酚对γ-生育三烯酚胆固醇抑制作用的影响。将对照和实验日粮喂给白来航鸡群（n = 10），持续26天。对照日粮补充21 nmolα-生育酚/克。所有实验日粮提供141 nmol混合生育三烯酚/克日粮。实验日粮中α-生育酚和γ-生育三烯酚的浓度分别为21至141 nmol/克和0至120 nmol/克。我们现在报告，在含有足够γ-生育三烯酚以抑制3-羟基-3-甲基戊二酰辅酶A还原酶活性的生育三烯酚混合物中加入α-生育酚会导致生育三烯酚作用减弱（P < 0.001）。利用不同棕榈维生素E制剂的研究结果总结表明，有效制剂含有15 - 20%的α-生育酚和约60%的γ-（和δ-）生育三烯酚，而效果较差的制剂含有≥30%的α-生育酚和45%的γ-（和δ-）生育三烯酚。
