Higher bacterial DNAemia can affect the impact of a polyphenol-rich dietary pattern on biomarkers of intestinal permeability and cardiovascular disease risk in older subjects

Scope. Aging is characterized by increased systemic low-grade inflammation, altered gut microbiota composition and enhanced intestinal permeability (IP). The intake of polyphenol-rich (PR) foods is proposed as a promising strategy to positively affect the gut microbiota-immune system-intestinal barrier (IB) axis. In this context, the MaPLE project was designed to test the hypothesis that a PR dietary pattern may preserve and/or improve IB function in older people. Here, we tested the hypothesis that the dietary intervention might have affected the presence of bacterial factors in the bloodstream of the older volunteers participating in the MaPLE trial. Methods and results. We quantified the presence of bacterial DNA in blood by qPCR targeting the 16S rRNA gene (16S; bacterial DNAemia). Blood DNA was taxonomically profiled via 16S sequencing. We found that higher blood 16S levels are associated to higher BMI and markers of IP, inflammation and dyslipidemia. Subjects with higher bacterial DNAemia could benefit more from the PR-dietary intervention as demonstrated by the reduction of the markers related to IP, inflammation and dyslipidemia. Finally, we found that the bacterial DNA detected in blood mostly belong to ?-Proteobacteria, whose abundance significantly decreased after the PR-diet in subjects with higher bacterial DNAemia at baseline.Conclusion. This study shows that the efficacy of the PR diet could depend on bacterial DNAemia. Bacterial DNAemia may be a relevant marker to evaluate in order to test the efficacy of dietary interventions based on PR-foods in the older populations.

研究背景：衰老以全身性低度炎症、肠道菌群组成改变及肠道通透性（intestinal permeability, IP）升高为典型特征。现有研究表明，摄入富含多酚（polyphenol-rich, PR）的食物或可作为调节肠道菌群-免疫系统-肠屏障（intestinal barrier, IB）轴的有效干预策略。基于此，MaPLE项目旨在验证假说：富含多酚的饮食模式可维持并改善老年人群的肠屏障功能。本研究进一步验证了另一假说：饮食干预或可影响MaPLE试验中参与的老年志愿者血液内细菌因子的水平。

方法与结果：本研究通过靶向16S核糖体RNA基因（16S rRNA gene，简称16S）的实时定量聚合酶链式反应（qPCR）对血液中的细菌DNA进行定量，即检测细菌DNA血症（bacterial DNAemia）水平，并通过16S测序对血液DNA开展分类学谱分析。结果显示，血液中较高的16S水平与更高的BMI、肠道通透性、炎症及血脂异常标志物水平呈显著正相关。细菌DNA血症水平较高的受试者可从富含多酚饮食干预中获得更显著的获益，表现为与肠道通透性、炎症及血脂异常相关的标志物水平显著降低。此外，本研究发现血液中检测到的细菌DNA大多属于?-变形菌纲（?-Proteobacteria），在基线细菌DNA血症水平较高的受试者中，该类群的丰度在接受富含多酚饮食干预后显著下降。

结论：本研究表明，富含多酚饮食的干预效果或与细菌DNA血症水平密切相关。细菌DNA血症或可作为评估老年人群中基于富含多酚食物的饮食干预效果的潜在检测标志物。