Delimont Nicole M, Rosenkranz Sara K, Haub Mark D, Lindshield Brian L
Department of Food, Nutrition, Dietetics and Health, Kansas State University, 1324 Lovers Lane, 208 Justin Hall, Manhattan, KS, USA.
Nutr Metab (Lond). 2017 Jul 24;14:47. doi: 10.1186/s12986-017-0197-z. eCollection 2017.
Tannins are often cited for antinutritional effects, including chelation of non-heme iron. Despite this, studies exploring non-heme iron bioavailability inhibition with long-term consumption have reported mixed results. Salivary proline-rich proteins (PRPs) may mediate tannin-antinutritional effects on non-heme iron bioavailability.
To review evidence regarding biochemical binding mechanisms and affinity states between PRPs and tannins, as well as effects of PRPs on non-heme iron bioavailability with tannin consumption in vivo.
Narrative systematic review and meta-analysis. Common themes in biochemical modeling and affinity studies were collated for summary and synthesis; data were extracted from in vivo experiments for meta-analysis.
Thirty-two studies were included in analysis. Common themes that positively influenced tannin-PRP binding included specificity of tannin-PRP binding, PRP and tannin stereochemistry. Hydrolyzable tannins have different affinities than condensed tannins when binding to PRPs. In vivo, hepatic iron stores and non-heme iron absorption are not significantly affected by tannin consumption ( = -0.64-1.84; -2.7-0.13 respectively), and PRP expression may increase non-heme iron bioavailability with tannin consumption.
In vitro modeling suggests that tannins favor PRP binding over iron chelation throughout digestion. Hydrolyzable tannins are not representative of tannin impact on non-heme iron bioavailability in food tannins because of their unique structural properties and PRP affinities. With tannin consumption, PRP production is increased, and may be an initial line of defense against tannin-non-heme iron chelation in vivo More research is needed to compare competitive binding of tannin-PRP to tannin-non-heme iron complexes, and elucidate PRPs' role in adaption to non-heme iron bioavailability in vivo.
单宁常被认为具有抗营养作用，包括对非血红素铁的螯合作用。尽管如此，关于长期食用单宁对非血红素铁生物利用度抑制作用的研究结果却参差不齐。富含脯氨酸的唾液蛋白（PRPs）可能介导单宁对非血红素铁生物利用度的抗营养作用。
综述关于PRPs与单宁之间生化结合机制和亲和状态的证据，以及PRPs对体内食用单宁时非血红素铁生物利用度的影响。
叙述性系统评价和荟萃分析。整理生化建模和亲和性研究中的共同主题以进行总结和综合；从体内实验中提取数据进行荟萃分析。
32项研究纳入分析。对单宁-PRP结合有积极影响的共同主题包括单宁-PRP结合的特异性、PRP和单宁的立体化学。与缩合单宁相比，可水解单宁在与PRPs结合时具有不同的亲和力。在体内，食用单宁对肝脏铁储存和非血红素铁吸收没有显著影响（分别为=-0.64-1.84；-2.7-0.13），并且PRP表达可能会增加食用单宁时非血红素铁的生物利用度。
体外模型表明，在整个消化过程中，单宁更倾向于与PRP结合而非与铁螯合。由于其独特的结构特性和PRP亲和力，可水解单宁不能代表食物中单宁对非血红素铁生物利用度的影响。食用单宁时，PRP的产生会增加，这可能是体内对抗单宁-非血红素铁螯合的第一道防线。需要更多研究来比较单宁-PRP与单宁-非血红素铁复合物的竞争性结合，并阐明PRPs在体内适应非血红素铁生物利用度中的作用。
