Dietary proanthocyanidins ameliorate age-related cognitive decline and neuroinflammation in thyroxine-induced accelerated aging-like mice via the gut microbiota-SCFAs-5-HTP axis

Age-related cognitive impairment is a major public health concern associated with neuroinflammation and gut microbiota dysbiosis. Proanthocyanidins (PC), a class of dietary polyphenols, have been suggested to modulate the gut–brain axis. Here, we investigated the mechanisms by which PC alleviate cognitive deficits in a thyroxine-induced accelerated aging-like mouse model. PC supplementation significantly improved spatial learning and memory, as assessed by the Morris water maze. These effects were accompanied by modulation of gut microbiota composition and altered fecal short-chain fatty acids (SCFAs), particularly butyrate and propionate. PC also improved intestinal barrier function, increased colonic tryptophan hydroxylase 1 (TPH1) expression, and regulated 5-hydroxytryptophan (5-HTP)/serotonin (5-HT)-related pathways. In parallel, hippocampal neuroinflammatory responses were attenuated. Collectively, these findings suggest that the neuroprotective effects of PC are associated with a gut microbiota–SCFAs–5-HTP/5-HT axis. This study highlights the potential of dietary proanthocyanidins as a nutritional strategy for mitigating cognitive impairment under thyroxine-induced accelerated aging-like conditions.