Interdepartmental Graduate Program in Nutritional Sciences, Department of Nutritional Sciences, University of Wisconsin-Madison, Madison, WI, USA.
Department of Pharmacology, Case Western Reserve University, Cleveland, OH, USA.
J Nutr. 2020 Nov 19;150(11):2912-2923. doi: 10.1093/jn/nxaa142.
Vitamin A (VA) deficiency is a public health problem in some countries. Fortification, supplementation, and increased provitamin A consumption through biofortification are efficacious, but monitoring is needed due to risk of excessive VA intake when interventions overlap.
Two studies in 28-36-d-old male Mongolian gerbils simulated exposure to multiple VA interventions to determine the effects of provitamin A carotenoid consumption from biofortified maize and carrots and preformed VA fortificant on status.
Study 1 was a 2 × 2 × 2 factorial design (n = 85) with high-β-carotene maize, orange carrots, and VA fortification at 50% estimated gerbil needs, compared with white maize and white carrot controls. Study 2 was a 2 × 3 factorial design (n = 66) evaluating orange carrot and VA consumption through fortification at 100% and 200% estimated needs. Both studies utilized 2-wk VA depletion, baseline evaluation, 9-wk treatments, and liver VA stores by HPLC. Intestinal scavenger receptor class B member 1 (Scarb1), β-carotene 15,15'-dioxygenase (Bco1), β-carotene 9',10'-oxygenase (Bco2), intestine-specific homeobox (Isx), and cytochrome P450 26A1 isoform α1 (Cyp26a1) expression was analyzed by qRT-PCR in study 2.
In study 1, liver VA concentrations were significantly higher in orange carrot (0.69 ± 0.12 μmol/g) and orange maize groups (0.52 ± 0.21 μmol/g) compared with baseline (0.23 ± 0.069 μmol/g) and controls. Liver VA concentrations from VA fortificant alone (0.11 ± 0.053 μmol/g) did not differ from negative control. In study 2, orange carrot significantly enhanced liver VA concentrations (0.85 ± 0.24 μmol/g) relative to baseline (0.43 ± 0.14 μmol/g), but VA fortificant alone (0.42 ± 0.21 μmol/g) did not. Intestinal Scarb1 and Bco1 were negatively correlated with increasing liver VA concentrations (P < 0.01, r2 = 0.25-0.27). Serum retinol concentrations did not differ.
Biofortified carrots and maize without fortification prevented VA deficiency in gerbils. During adequate provitamin A dietary intake, preformed VA intake resulted in excessive liver stores in gerbils, despite downregulation of carotenoid absorption and cleavage gene expression.
维生素 A（VA）缺乏是一些国家的公共卫生问题。强化、补充和通过生物强化增加类维生素 A 摄入是有效的，但由于干预措施重叠时可能摄入过多 VA，因此需要进行监测。
两项对 28-36 日龄雄性蒙古沙鼠的研究模拟了多种 VA 干预措施的暴露情况，以确定生物强化玉米和胡萝卜中的类胡萝卜素和预成型 VA 强化剂对状态的影响。
研究 1 是一项 2×2×2 析因设计（n=85），高-β-胡萝卜素玉米、橙色胡萝卜和 VA 强化剂达到 50%估计沙鼠需求，与白玉米和白胡萝卜对照相比。研究 2 是一项 2×3 析因设计（n=66），通过 100%和 200%估计需求量评估橙色胡萝卜和 VA 的消耗情况。两项研究均利用 2 周 VA 耗竭、基线评估、9 周治疗和 HPLC 测定肝脏 VA 储存。在研究 2 中，通过 qRT-PCR 分析了肠道清道夫受体 B 成员 1（Scarb1）、β-胡萝卜素 15,15'-加双氧酶（Bco1）、β-胡萝卜素 9',10'-加双氧酶（Bco2）、肠道特异性同源盒（Isx）和细胞色素 P450 26A1 同工酶 α1（Cyp26a1）的表达。
在研究 1 中，与基线（0.23±0.069 μmol/g）和对照组相比，橙色胡萝卜（0.69±0.12 μmol/g）和橙色玉米组（0.52±0.21 μmol/g）的肝脏 VA 浓度显著升高。仅 VA 强化剂（0.11±0.053 μmol/g）的肝脏 VA 浓度与阴性对照组无差异。在研究 2 中，橙色胡萝卜显著增加了肝脏 VA 浓度（0.85±0.24 μmol/g），与基线（0.43±0.14 μmol/g）相比，但单独使用 VA 强化剂（0.42±0.21 μmol/g）并没有。肠道 Scarb1 和 Bco1 与肝脏 VA 浓度的增加呈负相关（P<0.01，r2=0.25-0.27）。血清视黄醇浓度没有差异。
生物强化的胡萝卜和玉米在没有强化剂的情况下可预防沙鼠的 VA 缺乏。在适当的类维生素 A 饮食摄入期间，即使下调了类胡萝卜素吸收和裂解基因表达，预成型 VA 摄入也会导致沙鼠肝脏储存过量。
