Data_Sheet_1_The effects of polyphenols against oxidative stress in Caenorhabditis elegans are determined by coexisting bacteria.docx

IntroductionIncreasing evidence supports the role of gut microbiota in many aspects of human health, including immune, metabolic and neurobehavioral traits. Several studies have focused on how different components of the diet, such as polyphenols, can modulate the composition and function of the gut microbiota leading to health benefits.
MethodsThe effects on the resistance against thermally induced oxidative stress of C. elegans grown in the presence of flavonoids (quercetin or epicatechin) and fed different probiotic strains, namely Lactobacillus plantarum CLC17, Bifidobacterium longum NCIMB 8809 and Enterococcus faecium CECT 410, were explored.
ResultsFeeding C. elegans with the assayed bacteria in the absence of flavonoids did not significantly affect body size and fertility of the worms neither improve their resistance against oxidative stress compared to E. coli controls. However, increased resistance to stress was found when C. elegans was cultivated in the presence of both L. plantarum and flavonoids, but not with B. longum or E. faecium. An exploratory study revealed the presence of glycosylated and sulfated metabolites together with the aglycone in worms treated with quercetin and fed any of the different assayed LAB strains. However, in the assays with epicatechin a differential metabolite, tentatively identified as 5-(4′-hydroxyphenyl)-γ-valerolactone 3′-O-glucoside, was detected in the worms fed L. plantarum but not with the other bacteria.
ConclusionThe obtained results indicated that the interactions bacteria/polyphenol play a key role in the effects produced in C. elegans regarding resistance against oxidative stress, although those effects cannot be only explained by the ability of bacteria to metabolize polyphenols, but other mechanisms should also be involved.

引言
越来越多的证据表明，肠道菌群（gut microbiota）在人类健康的诸多方面发挥关键作用，涵盖免疫、代谢及神经行为表型。已有多项研究聚焦于膳食不同组分（如多酚（polyphenols））如何调控肠道菌群的组成与功能，进而带来健康益处。

方法
本研究探讨了在黄酮类化合物（flavonoids，即槲皮素（quercetin）或表儿茶素（epicatechin））存在下培养，并喂食不同益生菌菌株——即植物乳杆菌（Lactobacillus plantarum）CLC17、长双歧杆菌（Bifidobacterium longum）NCIMB 8809及屎肠球菌（Enterococcus faecium）CECT 410——的秀丽隐杆线虫（C. elegans）的热诱导氧化应激抗性变化。

结果
与大肠杆菌（E. coli）对照组相比，在无黄酮类化合物的条件下给秀丽隐杆线虫喂食本次试验所用的细菌，既未显著影响线虫的体型与繁殖力，也未提升其氧化应激抗性。然而，当秀丽隐杆线虫在植物乳杆菌与黄酮类化合物共同存在的环境中培养时，其应激抗性显著增强，但长双歧杆菌或屎肠球菌并未产生此类效果。探索性研究显示，在用槲皮素处理并喂食任意一种本次试验所用的乳酸菌（LAB）菌株的线虫体内，均可检测到糖基化、硫酸化代谢物以及苷元（aglycone）。不过在表儿茶素的相关试验中，仅在喂食植物乳杆菌的线虫体内检测到一种差异代谢物，经初步鉴定为5-(4'-羟基苯基)-γ-戊内酯-3'-O-葡萄糖苷（5-(4′-hydroxyphenyl)-γ-valerolactone 3′-O-glucoside），其余细菌组未检出该物质。

结论
本研究结果表明，细菌与多酚之间的相互作用在秀丽隐杆线虫氧化应激抗性相关效应中发挥关键作用；不过此类效应不能仅通过细菌代谢多酚的能力来解释，还应涉及其他作用机制。