(Poly)phenol-rich grape and blueberry extract prevents LPS-induced disruption of the blood-brain barrier through the modulation of the gut microbiota-derived uremic toxins

The dynamic protective capacity of (poly)phenols, attributed to their potent antioxidant and anti-inflammatory properties, has been consistently reported. Due to their capacity to alter gut microbiome composition, further actions of (poly)phenols may be exerted through the modulation of the microbiota-gut-brain axis. However, the underlying mechanisms remain poorly defined. Here, we investigated the protective effect of a (poly)phenol-rich grape and blueberry extract (Memophenol™), on the microbiota-gut-brain axis in a model of chronic low-grade inflammation (0.5 mg/kg/wk lipopolysaccharide (LPS) for 8 weeks). Dietary supplementation of male C57BL/6 J mice with Memophenol™ prevented LPS-induced increases in the microbe-derived uremia-associated molecules, indoxyl sulfate (IS) and trimethylamine N-oxide (TMAO). These changes coincided with shifts in gut microbiome composition, notably Romboutsia and Desulfovibrio abundance, respectively. In the brain, LPS exposure disrupted the marginal localisation of the endothelial tight junction ZO-1 and downregulated ZO-1 mRNA expression to an extent closely correlated with TMAO and IS levels; a process prevented by Memophenol™ intake. Hippocampal mRNA sequencing analysis revealed significant downregulation in regulatory pathways of neurodegeneration with Memophenol™ intake. These findings may indicate a novel protective role of the (poly)phenol-rich grape and blueberry extract on the endothelial tight junction component ZO-1, acting through modulation of gut microbial metabolism.