Iso-α-acids, the bitter components of beer, improve hippocampus-dependent memory through vagus nerve activation

What is it about?

Epidemiological studies report that moderate alcohol consumption is beneficial for cognitive function, but the effect of other ingredients in alcoholic beverages has not been clarified. Previously, we reported that long-term consumption of iso-α-acids (IAA), bitter components of beer prevents inflammation and Alzheimer's pathologies in mice, but their effects on cognitive function have not been evaluated. In the present study, we demonstrated that the consumption of IAA improves spatial and object recognition memory functions in mice. In addition, IAA consumption increased the dopamine, important neurotransmitter for the memory function, in the hippocampus. Mice knocked down of dopamine D1 receptor expression in the hippocampus attenuated IAA-induced spatial memory improvement. Furthermore, vagotomy attenuated the effects of IAA in improving spatial and object recognition memory functions and increasing the total level of dopamine in the hippocampus. These results suggest that the consumption of IAA activates dopamine D1 receptor signaling in the hippocampus in a vagus nerve-dependent manner and, consequently, improves spatial and object recognition memory functions. The amount of IAA showing memory improvement is equivalent to that in 400-1000 ml of beer. Our findings support the previous epidemiological study. Vagal activation with food components including IAA may be an easy and safe approach to improve cognitive functions.

Featured Image