人体β-胡萝卜素的肠转化和吸收后转化的研究

目的 :为了解部分中国人体内 β 胡萝卜素 ( β carotene ,以下简称 β C)转化维生素A (vitaminA ,以下简称VA)的效率 ,开展了本研究。方法 :使用稳定同位素稀释法对 15名 5 0 60岁健康农村志愿者 (男 9,女6)进行β C人体代谢实验。 2周适应期和 5 6天实验期内 ,志愿者接受常规膳食 ,避免大量VA和 β C摄入以及烟、酒和营养补充剂。实验第 1天 ,给受试者含 6mg氘标记 β C( 2 H8β C)玉米油胶丸 ,随半流质早餐 (脂肪热能比 2 5 % )一起摄入。实验第 4天 ,受试者以同样方法摄入含 3mg氘标记醋酸视黄醇 ( 2 H8RAC)油剂胶丸。实验第 1天和第 4天摄入标记物后 0 ,3 ,5 ,7,9,11,13h时 ,实验第 2 ,3 ,5 ,6,7,8,9,10 ,14,2 1,2 8,3 5 ,42 ,49,5 6天晨空腹时 ,采静脉血。用高效液相色谱仪 (HPLC)分离血清 β C和VA组分 ,再分别使用气相质谱仪(GC MS)和液相质谱仪 (LC MS)测定VA和 β C组分的同位素丰度。根据VA和 β C的浓度和同位素丰度 ,描述标记VA和β C在体内应答的血液动力学曲线。 结果 :所有 15名受试者对2 H8RAC应答明显 ;但是在对2 H8β C的应答方面 ,只有 11名受试者2 H4视黄醇应答曲线明显 ,有 4名受试者血清2 H4视黄醇应答曲线非常微弱。经过对备份血清样品进行的多次重复GC MS测定 ,我们目前初步?

Evaluation on intestinal and whole-body conversion of β-carotene to vitamin A in Chinese adults using a stable isotope reference method

Objectives:β-carotene (β-C) is a major and safe vitamin A source for a vast population in China. But there is little understanding on β-C-vitamin A equivalence in Chinese population. This study was designed to evaluate intestinal and whole-body conversion of β-C to vitamin A in some Chinese adults by using a stable isotope dilution technique. Methods: Fifteen healthy adult farmer volunteers (9 males and 6 females) aged 50～60 years from a few villages of China's eastern Shandong Province were recruited in a 55-days experiment. A Physiological dose of 2H 8 β-C (11011 nmole or 6 mg) in oil was given with a liquid diet (25 % energy from fat) to the volunteers in the first day of the study. Three days after the 2H 8 β-C dose, the volunteers each took a reference dose of 2H 8 RAC (8,915 nmole or 3 mg) in oil with the same liquid diet. Serum samples were collected at 0, 3, 5, 7, 9, 11, 13 hours of the first and the fourth days of study, and fasting serum samples were also collected daily in first 10 days and then weekly at 14th, 21st, 28th, 35th, 42nd, 49th, and 56th day after a 12-hour overnight fast.β-C and retinol were extracted from serum and isolated by high performance liquid chromatography. The serum retinol and β-C enrichments were respectively determined by using a gas chromatography/electron capture negative chemical ionization mass spectrometry (GC/ECNCI-MS) and liquid chromatograph /mass spectrometry with an atmospheric pressure chemical ionization interface (LC/APCI-MS). Results:All the subjects responded well to the 2H 8 retinyl acetate reference dose. However, the responses to the 2H 8 β-C dose were unexpectedly Poor in 4 of the 15 subjects. The repeated GC-MS analysis on the backup serum samples confirmed that these 4 subjects responded less efficiently to ingested 2H 8 β-C dose. These 4 subjects referred as to poor converters will be re-examined to confirm the observation. Therefore, the data of β-C metabolism of the 4 poor converters were not analyzed together with that of the 11 normal converters. In the normal converters (7 males and 4 females), the calculated conversion factor of β-C to retinol in1, 6, 13, 20, 27, 34, 41, and 52 days are 7.1±3.4, 5.6±2.7, 5.4±2.9, 5.1±2.8, 5.0±3.0, 5.0±2.9, 4.9±2.9, 4.8±2.8 to 1 on a molar basis respectively, and the corresponding post intestinal absorption conversion is estimated as (19.7±17.8)%, (22.7±20.5)%, (26.3±21.2)%, (27.8±22.7)%, (28.6±22.7)%, (29.5±22.8)% and (30.1±22.1)% of the total converted retinol. Conclusion: The different time conversion of β-C to vitamin A in the tested Chinese adults had been quantitatively determined by using a stable isotope reference method, and the long term as 52 days conversion factor value was 9.1 to 1 on a weight basis, and about 30% of total converted retinol came from absorbed intact β-C.