中老年人β-胡萝卜素转化为维生素A的效率

目的:了解中国成人体内β-胡萝卜素( β-carotene, β-C ) 转化维生素A (VA)的效率。方法:使用稳定同位素稀释法对11名50～60岁健康志愿者(男7,女4)进行 β-C人体代谢实验。2 w适应期和8 w实验期内,志愿者接受常规膳食,避免大量VA和 β-C摄入及烟、酒和营养制剂。实验D1 ,给受试者含6 mg氘标记 β-C(2H8 β-C )玉米油胶丸,随半流质早餐(脂肪热能比25%)一起摄入。实验D4 ,同样方法摄入含3 mg氘标记醋酸视黄醇(2H8 -RAc ) 油剂胶丸。实验D1 和D4 摄入标记物后0、3、5、7、9、11、13 h时,实验D2、3、 5、6、7、8、9、10、14、21、28、35、42、49、56 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: 11名受试者对口服2H8–RAc和2H8-C的应答均非常明显;52 d时血清中2H4视黄醇(来自2H8 β-C)的曲线下面积(AUC )平均为1 102 ± 658 nmol/d,52 d的2H8视黄醇(来自2H8 -RAc)的AUC平均为3659 ±787 nmol/d, 以摄入的2H8 –RAc作为VA参照,计算来自摄入2H8-C的2H4 视黄醇平均为2599 ±1180 nmol/d 。由此计算 β-C

STUDY ON THE CONVERSION RATIO OF β-CAROTENE TO VITAMIN A IN CHINESE ADULTS BY ISOTOPE DILUTION TECHNIQUE

Objectives: This study was designed to determine the conversion ratio of synthetic deuterium labeled ?C to vitamin A in some Chinese adults by using stable isotope dilution technique. Methods: Eleven healthy Chinese adult volunteers aged 50-60 years were recruited in a 56 day experiment, which included residency in the Metabolic Research Unit (first 10 days) and at home (last 46 days). A physiological dose of 2H8 ?-C (11 011 nmol or 6 mg) in oil was given with a semi-liquid diet (25 % energy from fat) to the volunteers (7 males and 4 females) in the first day of the study. Three days after the 2H8 ?C dose, each volunteer took a reference dose of 2H8 retinyl acetate (8 915 nmol or 3 mg) in oil with the same semi-liquid diet. Serum samples were collected at 0, 3, 5, 7, 9, 11, 13 hours of the 1st and the 4th day of study, and fasting serum samples were also collected daily in first 10 days and then weekly at morning of the 14th, 21st, 28th, 35th, 42nd, 49th, and 56th day after 12h overnight fast. ?C and retinol were extracted from serum and isolated by high performance liquid chromatography (HPLC). The serum retinol and -C enrichments were respectively determined by using gas chromatograph/mass spectrometry (GC-MS) with electron capture negative chemical ionizationand liquid chromatograph /mass spectrometry (LC-MS) with an atmospheric pressure chemical ionization interface. Results:The average 52 areas under the serum 2H4 retinol response curve (from 2H8 -C dose) was 1 102658 nmol/d and the 52 areas under the serum 2H8 retinol response curve (from 2H8 retinyl acetate dose) was 3 659787 nmol/d. By using 2H8 retinyl acetate as vitamin A reference, 2H4 retinol formed from 2H8 ?-C (11,011 nmol) was calculated to be equivalent to 2 5991 180 nmol of retinol. The calculated conversion factor of ?C to retinol ranged from 2.0-12.2 to 1 with an average of 4.82.8 to 1 on a molar basis, or 3.8-22.8 to 1 with an average of 9.15.3 to 1 on a weight basis. Conclusion: The conversion of -C to vitamin A in Chinese adults had been quantitatively determined by using stable isotope reference method, and was 9.1 to 1 on a weight basis.